Fuchsia is not Linux
fuchsia.googlesource.com
fuchsia.googlesource.com
> Calls which have no limitations, of which there are only a very few, for example zx_clock_get() and zx_nanosleep() may be called by any thread.
Having the clock be an ambient authority leaves the system open to easy timing attacks via implicit covert channels. I'm glad these kinds of timing attacks have gotten more attention with Spectre and Meltdown. Capability security folks have been pointing these out for decades.
> Calls which create new Objects but do not take a Handle, such as zx_event_create() and zx_channel_create(). Access to these (and limitations upon them) is controlled by the Job in which the calling Process is contained.
I'm hesitant to endorse any system calls with ambient authority, even if it's scoped by context like these. It's far too easy to introduce subtle vulnerabilities. For instance, these calls seem to permit a Confused Deputy attack as long as two processes are running in the same Job.
Other notes on the kernel:
* The focus on handles overall is good though. Some capability security lessons have finally seeped into common knowledge!
* I'm not sure why they went with C++. You shouldn't need dispatching or template metaprogramming in a microkernel, as code reuse is minimal since all primitives are supposed to be orthogonal to each other. That's the whole point of a microkernel. Shapiro learned this from building the the early versions of EROS in C++, then switching to C. C also has modelling and formal analysis tools, like Frama-C.
* I don't see any reification of scheduling as a handle or an object. Perhaps they haven't gotten that far.
Looks like they'll also support private namespacing ala Plan 9, which is great. I hope we can get a robust OS to replace existing antiquated systems with Google's resources. This looks like a good start.
Orthogonality doesn’t obviate the need for metaprogramming though. For example, there are lots of places you might need a linked list structure, where the nodes store different types. You might use templates over intrusive structures to gain some type safety without duplicating code for each contained type.
I haven't worked with Go personally, but "no generics" is probably the most commonly vocal complaint I hear about it, so clearly some people do care.
Not my observation at all.
Multiply that by 10 if you have several junior team members who have been told, and read, that concurrency and parallelism is easy in go.
Advanced users might want to use advanced data structures that are not built-in in the langage, and templates can be convenient to do that.
Sure, but linked lists have solutions already using simple macros [1]. There aren't many sophisticated kernel data structures, mainly tables for indexing and linked lists, all of which have simple expressions as macros. Templates perhaps make this a little easier, but are overkill.
[1] http://www.roman10.net/2011/07/28/linux-kernel-programmingli...
aPerson = list_entry(node, struct Person, list);
Sure they do, unless your type checker is formally verified. Are you suggesting there exists a formally verified C++ compiler?
> Running the compiler is also a lot cheaper than having someone inspect every line of code carefully.
Except that's not what I suggested. You only need to audit lines that perform potentially undefined behaviour. The C type checker ensures the rest are fine. I think it's clear this problem is worse in C++ given all of the additional abstractions that interact in surprising ways.
Furthermore, C++ has no formal verification tools, so if you wanted real guarantees, you'd use something like Frama-C or a theorem prover like they did with seL4. Microkernels in C++ have been tried, and in every case they switched back to C for very good reasons.
If I care so much about system correctness that I do the insane amount of work that is formal verification (just look at how many man years sel4 consumed!), I don't write C or C++ at all, I use Spark. There is a reason why you can count the number of formally verified kernels on the fingers of one hand, and it's not because everybody tries to use C++ instead of C.
Nope, but your unqualified statement was simply false, and in any case, your point isn't really relevant. This single line of code we're discussing is easily verifiable by manual inspection and automated testing. We're not talking about huge swaths of code here, we're talking about a few unsafe primitives, because this kind of reuse isn't typical of a microkernel.
The type safety of a single operation expressed as a template is relatively insignificant compared to the added complexity of C++, particularly considering the "reuse" benefits are non-existent for microkernels, and if all you're left with is some elusive "type safety" for a linked list, that's simply not enough.
This is obvious when you know the history of multiple C++ kernel verification efforts, all of which failed, no matter how simple of a C++ subset was chosen. Many C verification efforts have succeeded, and tools for lightweight formal methods, like Frama-C, make the transition to verification possible with C. C++ is a dead end for this purpose, and the various L4 groups that created L4 kernels in C++ and then rewrote them in C all agree.
Is there a way that these could mediated by a capability without having to incur syscall overhead? One of the reasons that these are bare functions is likely that they are in the vDSO, and are just simple function calls which can access some shared memory which contains the clock time. I suppose you could simply not give some processes access to that memory, and have the functions in the vDSO just return an error in that case.
I know that there was a time when the Linux kernel changed how their vDSO handling worked, so older glibcs would have to fall back to making an actual syscall for gettimeofday, and that seriously affected performance on some servers that updated the kernel without updating glibc. These functions are called quite often on servers for logging purposes, so adding overhead to make them go through a syscall can be a big performance hit.
> I'm hesitant to endorse any system calls with ambient authority, even if it's scoped by context like these. It's far too easy to introduce subtle vulnerabilities. For instance, these calls seem to permit a Confused Deputy attack as long as two processes are running in the same Job.
Yeah, this is a bit odd. In fact, it's not just these syscalls which have ambient authority, there's a whole list in https://fuchsia.googlesource.com/zircon/+/master/docs/syscal... and it includes VMOs, ports, sockets, and so on.
It does seem somewhat odd to have this capability system, but then ignore it for a number of actions which can only be limited at the job level.
Is that even warranted? What applications can you imagine would make so many clock calls so as to incur noticeable overhead?
Your example of logging costs might work, but I'm very skeptical that user/kernel transition costs for a clock call would drown out the costs of writing the log entry to disk.
But to answer your question directly, the ability to access the clock in a shared memory segment can itself be reified as a handle that's granted to a process. The process would then issue a map operation and provide an address at which to map the clock (or you could just always map it at the same address too if that's preferable for some reason).
There's a few more related articles on his blog if you search, and I've read of it being implicated elsewhere, that's not to say the software calling that much was doing the right thing, just that it had impact.
You might be shielded from this depending on what level you're working at, but there's a reason that vDSO exists basically solely for clock_gettime, too.
Yes it allows for timing attacks, but you can't really avoid that, either, not without utterly crippling your platform.
That seems strange to me. Why would you use the clock/gettime call for that instead of a work counter of some sort?
Something like sleep() is an operation on your own schedule, not an operation on a global system clock. That's not nearly as problematic.
Consider if you wanted to virtualize a process, say to deterministically replay it to trigger a fault or something. sleep(100 ticks) doesn't require additional kernel support for virtualization, but an ambient clock requires a lot of extra kernel support.
If the clock were only accessible via a handle, then you could proxy invocations on the handle without any extra support in the kernel. See my other comment for more details: https://news.ycombinator.com/item?id=16817462
Otherwise what actually happens when you do a postDelayed(func, delay) is it immediately is translated into a postAt(func, clock_gettime() + delay). Then as messages are consumed the work queue consistently knows how long it should wait to wake back up, no matter how many delayed tasks are in flight.
Are you instead talking about some kind of event loop? If so, then clock_gettime seems like it's merely convenient, not essential. You could just as easily keep a ticket incremented on successful operations or successive loops (or some other metric), and exponential backoff is a wait operation on a ticket number.
Unless you're suggesting the delay must be based on real time for some reason?
Congrats, you've re-invented clock_gettime(CLOCK_MONOTONIC) :)
You're right that it's not essential to have, but if you can re-implement it then you've also just re-introduced the timing attack that the removal of clock_gettime was trying to prevent.
The trivial-ness with which a clock suitable for timing attacks is able to be created is literally why SharedArrayBuffer was panic-removed from all major browsers. Because that's all you need, shared memory & a worker. Congrats, you have a high-precision timer with zero OS support.
So as soon as you allow any form of threading or shared memory to occur you've given apps a high precision timer, so you might as well just give them an actual timer, too.
I'm not convinced. The clock is global, shared among all processes, the ticket I suggested is local to a process, and so can't be used to signal between processes. Unless I'm again missing some context for what you mean.
That still requires a piece shared state, like I said. That vulnerability results from running untrusted code in the same process as trusted code. The whole point of a process is to establish a protection boundary around potentially unsafe code, hence why I keep mentioning processes, and this is the whole point of microkernels and IPC. Within a process, all bets are off.
My earlier point was that a shared clock between processes amplifies this problem so that timing attacks cross even the process protection boundary. So when you started talking about job scheduling, I assumed the following:
1. we're in a microkernel context, where we partition trusted and untrusted code using processes.
2. the job scheduling system you mentioned either
a) is a process running its own code that it trusts and so in-process timing attacks don't matter, but timing attacks with another process might matter and so you don't want to grant a clock capability if it isn't needed, or
b) is a process scheduling system ala cron, where the job scheduler is trusted but the jobs being run are untrusted, and so they run in separate processes.
In case (a), the ticket system seems sufficient if you don't want/need to grant access to the clock consistent with least privilege, and for (b) the job scheduler may or may not have the clock installed or not, doesn't really matter, since job scheduling happens via IPC so there's no shared read, ie. delay(100 ticks, self) sends the relative delay which the cron-like scheduler adds to its own clock.
Hopefully that clarifies my context, and you can then describe what assumptions your scenario violates.
It doesn't, though. Your point fundamentally misunderstands the nature of a timing attack for ex-filtration. It doesn't cross process boundaries. It doesn't use any process crossing state of any kind for timing. It simply times how long it takes to access cache lines, which is perfectly local & isolated. It does not involve time correletation or association across processes of any kind. It doesn't care about real time at all. All it needs is a stopwatch that can measure the difference between 0.5-2ns & 80-120ns.
The meltdown attack via SharedArrayBuffer did not use any untrusted code in the same process. It read kernel memory at will using 2 threads and an atomic int.
And besides logging, there are things like nanosleep or spinlocks which may briefly spin while querying the time before yielding.
I know of at least one CDN which was measurably impacted by the gettimeofday issue.
And yes, you could have the access to the address itself be something you are given access to via a capability/handle, but then the system call itself (which is actually a vDSO call) wouldn't have to actually take a handle as a parameter.
Another poster said something similar, but using the clock for this seems strange to me. Yielding a time slice for a certain number of ticks doesn't need access to the current time. I have less objection to an ambient yield since that's really an operation on your own schedule capability.
If you're after some kind of exponential backoff for a spinlock, that again doesn't seem to need the current time so much as a growing counter of the number of ticks to sleep.
> And yes, you could have the access to the address itself be something you are given access to via a capability/handle, but then the system call itself (which is actually a vDSO call) wouldn't have to actually take a handle as a parameter.
Correct, you'd use the handle to install an ambient clock in your environment. This leaves open the possibility that you can easily virtualize the clock by proxying the clock handle, ie. instead of the kernel updating your shared memory segment, it's another process.
The point being that reifying everything as a handle makes arbitrary virtualization patterns possible, but having ambient authorities all the way down to root makes it much more difficult.
Does it matter if it seems strange to you? The GP gave real world examples of where this is an impact. I'm not sure why you are arguing against the design.
Because the design is questionable, and so the example is questionable. Isn't that obvious? Why else would I bring it up?
I will grant that this case is an outlier, but this customer use-case is real enough to drive development dollars. It may not be the norm, but precision timing access appears to be very useful in some hard real-time contexts given current hw/sw realities.
Mixing safety criticality levels is hard.
Low latency processing or realtime-ish applications. If you have a budget of a few milliseconds only, lots of gettimeofday can start to add up. Now true that nowadays they are mostly vDSO so it doesn't matter as much. I remember before they were we saw a decent speedup when we upgraded to vDSO kernel version.
> But to answer your question directly, the ability to access the clock in a shared memory segment can itself be reified as a handle that's granted to a process.
rdtsc is not shared memory but more like a register read. Though it is a virtualized instruction so on proper VMs (not a container) it is possible to control what the guest sees as the value.
The point being, a handle should be involved at some point in order to make the access control explicit and not implicit and ambient.
This can happen because RDTSC is not synchronized between physical CPU sockets (NUMA regions).
Good point. I was going to say that in general the vDSO is just rdtsc + an offset applied. However they insert a barrier before it usually. That maybe or many not be helpful so I would probably still use rdtsc by itself.
I'd never heard the terms "Confused Deputy" or "ambient authority" before, but it sent me on a pleasant and informative internet security tangent.
https://www.youtube.com/watch?v=TQhmua7Z2cY&index=5&list=PLU...
It is a good course.
"leaves the system open" are strong words. If you allow only threads you have got high precision clocks as a bonus in practice. Still it could be useful to have environments so restricted that even restricting clock services could be useful, but I would certainly not call the lack of capability there a very big issue. Plus designing those would be hard anyway: does not having this capa would mandatorily prevent from even creating threads (or pretty much all kind of objects which can be retargeted to infer time, which means tons of them, and maybe it being the case or not will depend on the implementation)?
Maybe it is better to not pretend that a capability exists for getting the time if you will probably be able to get it without said capability?
The point being, any abilities that aren't reified as explicit handles are ambient in the environment, and so make isolation and virtualization harder. Consider how you would virtualize the clock now that it's part of the process's implicit environment instead of an invocation made via a handle.
An OS could help by making the virtualisable clock the default API. Still there will be applications that want a high-precision or low overhead clock. But those applications should buy into the trade-off explicitly.
And the Spectre and Meltdown vulnerabilities have shown that it doesn't matter. Taking access to a clock or sleep mechanism away doesn't stop the bad guys but makes common programmers lives much more difficult.
You don't take it away, you reify the clock as a capability/handle. This has two benefits:
1. Those vulnerabilities have shown that you can mount timing attacks even without a clock, but a clock amplifies the timing attacks you can mount. For instance, there remain attacks with a clock even if Spectre and Meltdown and related vulnerabilities are fixed.
2. There are software engineering benefits. For instance, in principle you can replace the clock handle with a proxy that you can use to provide your own times. This helps considerably with testing, deterministic replay, etc.
Basic memory management and error handling, for example, are radically easier and less error prone in C++ than in C. Less reliance on macros and goto's should be pretty obvious wins.
There's really very little reason to ever use C over C++ with modern toolchains.
Microkernels don't need memory management. Dynamic memory management in a kernel is a denial of service attack vector. Fuschia is built on a microkernel, so I expect they will follow the property of every microkernel since the mid 90s: no dynamic memory allocation in the kernel, all memory needed is allocated at boot.
Furthermore, you don't want exceptions in kernel code. That carries huge and surprising runtime execution and space costs.
Simply put, there is no reason to choose C++ for a microkernel, and many, many reasons not to.
Surely there’s a reason. Why?
Are they aware of them? That's not so clear. There's a lot of literature in microkernel design. Lots of things have been tried which sound good but haven't worked out, and some things didn't work out well before would work well now. As usual, security also rarely gets the attention it deserves and it's doubly important at the kernel level.
This does not seem incredibly complicated.
Except this was tried. More than once for different kernels (EROS and L4 at least), and they regretted it and then switched back to C. Both projects made many excellent arguments against C++ in a microkernel that haven't suddenly disappeared in modern C++.
So I think I am being charitable in this case because the weight of evidence suggests otherwise. It's charitable to assume that the developers are well meaning but aren't familiar with the history. This isn't staggering ignorance, just ordinary run of the mill ignorance.
For L4, there's brief mention here of the VFiasco project which attempted a verified L4 using C++, which failed despite considerable effort [2].
[3] is perhaps a better review of what worked and what didn't work in L4 research, and they explicitly discuss the issues, such as the fact that C++ conveyed no real advantages over C, the extra complexity of C++ made verification intractable (even for a subset), and practically, the availability of good C++ compilers for embedded systems was limited.
[1] http://webcache.googleusercontent.com/search?q=cache:PQMCrw4...
[2] http://web5.cs.columbia.edu/~junfeng/09fa-e6998/papers/sel4....
[3] https://ts.data61.csiro.au/publications/nicta_full_text/8988...
Of course they do. It takes memory to hold metadata about a process. It takes memory to hold resources about other services. It takes memory to pass data between them.
Just because that memory is reserved at boot doesn't mean it suddenly has no lifecycle of any kind.
> Furthermore, you don't want exceptions in kernel code.
Nobody said anything about C++ throw/catch exceptions.
> Simply put, there is no reason to choose C++ for a microkernel, and many, many reasons not to.
If you want to avoid C++ that's great, but to argue for C over it is insanity rooted in nostalgia.
Yes it does. The "lifecycle" is: allocate at boot, machine halts.
All of the memory you describe for other purposes is allocated at user level and booked to processes. This is how you make a kernel immune to DoS.
> Nobody said anything about C++ throw/catch exceptions.
That's the only meaningful difference in error handling between C and C++. Since you mentioned error handling as a reason to choose C++, what else could you possibly mean?
> If you want to avoid C++ that's great, but to argue for C over it is insanity rooted in nostalgia.
Sure, you keep believing that. It's clear you're not familiar with microkernel design. The advantages C++ has for application-level programming are useless in this domain.
So if you're going to argue in favour of C++ with the caveat of good developer practices then you must also make the same caveat of C (ie you cannot play the "goto spaghetti" card) otherwise you're just intentially skewing your comparison to win a pointless internet argument.
There's no goto spaghetti in C -- it's only used for local error handling, not for jumping around, at least since the 70s...
All 10 of them?
Enterprises also write native code, it is not everything Java, .NET and SAP stuff.
The rest of it could hide any number of dragons (and be written in any kind of legacy, nightmarish, and/or proprietary tools and languages), so it's not much of a proof of widespread bad C "goto" abuse.
Let's make a better criterion: how many of the top 200 C projects in GitHub suffer from "spaghetti goto" abuse? How many of all the C projects in GitHub?
For example, iOS applications, portable code between Android and iOS, distribution tracking, factory automation, life science devices, big data, graphics are all a small list of examples where C and C++ get used a lot.
Sometimes it says C++ on the tin, but when one opens it, it is actually the flavour I call "C with C++ compiler".
Github is not representative of enterprise code quality.
Bjarne created C++ exactly because he didn't want to repeat the experience he had, when he lost his Simula productivity to BCPL.
Of course the C designers thought otherwise of their own baby.
https://isocpp.org/blog/2012/11/universal-references-in-c11-...
In my view C++ is a very complex language that only few people can write safely and productively.
When you say "I understand my code" I have to believe you. The problem is that understanding other people's C++ code takes ages, even if they don't abuse the language. Trusting their code is another story entirely.
C++ is a very flexible language in that it puts few restrictions on redefining the meaning of any particular syntactic expression.
That's great, but it also means that there is a lot of non-local information that you have to be aware of in order to understand what any particular piece of code actually does.
I'm not surprised that C++ is both loved and hated and perhaps even more often simply accepted as the only practical choice.
There aren't many widely used languages around that allow us to optimize our code almost without limit and at the same time provide powerful abstraction facilities.
At the same time, there aren't many widely used languages around that make reading other people's code as difficult as C++ (even well written code) and come with a comparably long tail of accumulated historical baggage.
Even Java and C# are slowly getting down that path.
Languages get those features because they make sense and solve real production problems.
The language is dealing with some tricky concepts. To hide them or try to gloss over them would lead to writing virtual machines and bloated memory usage etc. in the style of C# / Java.
How else would you deal with movement of variables and when an rvalue becomes an lvalue inside a function?
> Any language can be used to write indecipherable bad code. You are blaming the wrong thing. Some languages allow stupid things. Some even encourage it. So, no, languages can and should be blamed.
Can you please name a project that you have worked on where you have run into problems because everything was in a single namespace? What was the problem, how did you run into it, and how did you resolve it?
There are a lot of advantages to namespaces. I used to believe that single-namespace languages would cause problems for large software, but working with Emacs (huge single namespace with all the libraries loaded into memory at once, so much worse than C, where you only link a subset of libraries), this problem has not surfaced. I mean literally the only difference is that ".", or whatever the language-enforced namespace accessor is, goes from being special syntactically, to being a convention. When you start to think about namespaces as trees, this makes more sense. Namespaces just push naming conflicts to the parent node. There is no magic that is going to solve conflicts or structure things well or give things clear names. All that is up to the programmer.
I believe he means RAII. It makes it almost impossible to forget to release resources or rollback transaction.
There are also library types that enforce checking for errors, something currently impossible in C.
Also thanks to its stronger type system, it is possible to do type driven programming thus preventing many errors to happen at all, which is also not possible in plain C.
Finally everyone is moving to C++, C for OS development is stuck on UNIX and embedded devs that wouldn't use anything else even at point gun.
OpenCL lost to CUDA because it did not natively supported C++, only when it was too late.
NVidia has designed Volta specifically to run CUDA C++ code.
There is no C left on game consoles SDKs or major middleware engines.
All major C compilers are written in C++.
Microsoft has replaced their C runtime library by one written in C++, exposing the entry points as extern "C".
Beyond the Linux kernel, all native parts on Android are written in C++.
The majority of deep learning APIs being used from Python, R and friends are written in C++.
Darwin uses a C++ subset on IO Kit, and Metal shaders are C++14.
AUTOSAR has updated their guidelines to use C++14 instead of C.
All major modern research OSes are being done in C++, like Genode.
Arduino Wiring and ARM mbed are written in C++.
As for Rust, while I do like it a lot, it still cannot compete with C++ in many key areas, like amount of supported hardware, GUI frameworks and available tooling.
They are surely a vocal minority, otherwise Metal shaders wouldn't be C++14.
Really? Interesting thing. You mean for "standard/legacy" autosar, or for the new "dynamic" variant?
When I was back in automotive, the autosar design(s) where probably the ones software people were mostly complaining about.
I am no expert there, learned it from their presentation at FOSDEM last year.
https://archive.fosdem.org/2017/schedule/event/succes_failur...
Page 12 on the second slideset.
This is a weak form of checking for a kernel. L4 Hazelnut was written in C++ for this reason, but they didn't use it much, mirroring Shapiro's experience with EROS. And when they had to revise the kernel design to plug security holes and they wanted to formally verify its properties, they switched to C because C++ was too complex and left too much behaviour unspecified, and thus we got verified seL4 written in C.
{
Resource foo(path);
if … {
return -ENOMEM
}
return 0;
}
{
Resource* foo = acquire(path);
if … {
release(foo);
return -ENOMEM
}
release(foo);
return 0;
}
{
Resource* foo = acquire(path);
int rc = 0;
if … {
rc = -ENOMEM
goto out;
}
out:
release(foo);
return rc;
}No. For that you need a better type system. Linear types show great promise for this.
[1] http://homepages.inf.ed.ac.uk/wadler/papers/linearuse/linear...
This kind of pattern doesn't exist in a microkernel. I agree it might be useful in a monolothic kernel, but that's not the context here.
No, they aren't. A microkernel is responsibe for basic thread management and IPC. Both of which are highly dynamic in nature.
You seem to be confusing the system that decides when to make a scheduling decision (userspace process - although still part of the microkernel project, so still included in all this anyway), with the system that actually executes that decision (the microkernel itself). And in the case of systems like QNX the kernel will even do its own decisions independent of the scheduler service, such as switching the active thread on MsgSend.
But whether or not it's in ring0 or ring3 is independent of whether or not it's part of a microkernel. A microkernel delegates responsibility to ring3 processes, but those processes are part of the microkernel system - they are in fact a very critical aspect of any microkernel project, as without them you end up building a bootloader with aspirations of something bigger than a kernel.
I disagree. Certainly you won't get a usable system without some core services, but the fact that you can replace these services with your own as long as you satisfy the protocol means there's a strong isolation boundary separating them from the kernel. Certainly they are essential components of the OS, just not the kernel.
As for the alleged dynamism of thread management and IPC, I don't see how it's relevant. There exist asynchronous/non-blocking IPC microkernel designs like VSTa and Minix in which the kernel allocates and manages storage for asynchronous message sends, but it's long since proven that such designs are hopelessly insecure. At the very least, it's trivial to DoS such a system.
Only bounded message sends with send/receive buffers provided by processes can you avoid this inevitability. If the idea with Fuchsia is to reimagine consumer operating systems, avoiding the same old mistakes seems like a good idea.
As for scheduling, that's typically part of the kernel logic, not a user space process. Yes, message sends can donate time slices/migrate threads, but there are priority inversion problems if you don't do this right, as L4 found out and avoided in the seL4 redesign. I honestly don't know why Google just didn't use or acquire seL4 for Fuchsia.
ESR was recently making some generalized observations in this direction: http://esr.ibiblio.org/?p=7804
* Donald Knuth: http://tex.loria.fr/litte/knuth-interview
* Linus Torvalds: http://harmful.cat-v.org/software/c++/linus
* Martin Sústrik: http://250bpm.com/blog:4
If I were to start a project today, I'd rely heavily on optional and result types and use exceptions only for serious errors, when it makes sense to unwind ans start from a clean slate.
He then criticises exceptions thrown in constructors and favors a init-function style. I never had any problem with this because I follow the rule that there shouldn't be much code in the constructor. The one and only task of a constructor is to establish the object's invariant. If that is not possible, then the object is not usable and the caller needs to react and shall not use the object.
In the second series, he first compares apples (intrusive containers) and oranges (non-intrusive containers), and then argues that the language forces him to design his software that way. Basically he argues that encapsulation makes it impossible in his case to write efficient code, and that you have to sacrifice it for performance.
However, with C++, you can extract the property of being an object in an intrusive list into a re-usable component, e.g. a mix-in, and then use your intrusive list with all other types. I can't do this in C in a type-safe manner, or I have to modify the structs to contain pointers, but why should they have anything to do with a container at all?
Besides that, I think that Martin is a greate programmer who did an amazing job with ZeroMQ. But I have the impression that he is wrong in this case.
I don't really like C++ and I haven't been forced to use it (with C and C++ you are basically forced to use them, few people use them for greenfield projects willingly, same for JavaScript; this of course doesn't apply for people who are already C/C++/JavaScript programmers), but from everything I've seen about modern C++ they are moving to a more consistent programming style.
Criticizing C++ in 2018 with arguments from back in 1993 feels dishonest.
"The problem that I have with them today is that... C++ is too complicated. At the moment, it's impossible for me to write portable code that I believe would work on lots of different systems, unless I avoid all exotic features. Whenever the C++ language designers had two competing ideas as to how they should solve some problem, they said "OK, we'll do them both". So the language is too baroque for my taste. But each user of C++ has a favorite subset, and that's fine."
In fact, they do so even better than they did back then. E.g. I eagerly anticipated C++11, but virtually every codebase that's older than three or four years and not a hobby project is now a mixture of modules that use C++11 features like unique_ptr and modules that don't. Debugging code without smart pointer semantics sucked, but debugging code that has both smart pointer semantics and raw pointers sucks even harder.
There's a huge chasm between how a language is standardized and how it's used in real life, in non-trivial projects that have to be maintained for years, or even decades.
Debugging pointers seems a poor reason to criticize an entire language!
C++ may be complicated but the English language is also complicated; just because people tend to use a smaller vocabulary than others doesn't make the language irrelevant or worthless.
Looking at how English has been used to create a raft of rich and diverse poetry, plays, prose and literature in general, the same should be applied to C++ because the unique use of it in a variety of varying circumstances surely is its beauty.
I don't think this is a valid argument, though. Natural languages have to be rich. Programming languages should be terse and concise because we have to keep most of them in our heads at one time and our brain capacity is limited. You don't need to know all of English/French/Romanian but you kind of need to know all of C++/Python/Javascript to do your job well when developing C++/Python/Javascript.
I think the C++ designers lately kind of agree with me but the backward compatibility requirements are really stringent and they can't just deprecate a lot of the older features.
Legalese uses a ton of latin ididoms, arcane rights and philosophies. This is comparable to the cruft of C or C++ standards. For a microkernel of some thousand LOC you shouldn't need a multi-paradigm language.
seL4 did it in Haskel, which is a step in the right direction. Then it was ported to a provably safe subset of C.
"At the moment, it's impossible for me to write portable code that I believe would work on lots of different systems, unless I avoid all exotic features."
Is just not remotely true anymore. Modern toolchains entirely obsoleted that. Modern C++ compilers are nothing like what Knuth used in 1993.
If anything it's easier to write portable C++ than it is portable C due to C++'s STL increasingly covering much of the POSIX space these days.
That statement itself seems intellectually dishonest. What has changed that invalidates his arguments? After all, C++17 is still backwards compatible to the C++ of 1993.
Pardon me for finding this humorous, but stating that I can’t use a Donald Knuth quote in a computer science topic because it’s an old is like saying I can’t quote Sun Tzu when talking about modern events because the Art of War is an old book.
https://en.m.wikipedia.org/wiki/The_Art_of_Computer_Programm...
So to change your analogy, it would be like quoting Sun Tzu about the disadvantages of modern main battle tanks, using the Art of War. Sure, the principles in the Art of War are solid, but are we sure that they really apply to a discussion about Leopard 2 vs M1 Abrams?
That said, I'm not a fan of C++ either. I think its problems are intractable because they'd have to break backwards compatibility to clean the language and I'm not sure they can do that, unless they want to "Perl 6"-it (aka kill the language).
In any event, Knuth specifically made statements dismissive of C++ 25 years ago that I believe are still valid today. I must have missed reading Sun Tzu's missive on mechanized warfare from the 6th century BC. ;)
Indeed, we can both agree on the backwards compatibility problem. I'm waiting on a C++ build as I type this. Also, I really like the new language features like std::unique_ptr std::function and lambdas.
I'd still rather do my true low-level programming in C bound with a garbage-collected higher-level language for less hardware-focused or performance-critical work instead of bolting those features on to C by committee over the span of decades. For example, C shared libraries with Lua bindings or LuaJIT FFI are bliss in my humble opinion.
Did you know that code in C++ can run outside of main()?
I used to be a C++ believer, and advocated for C++ over our companies use of Java.
One day, they decided they wanted to "optimize" the build, by compiling and linking objects in alphabetical order. The compile and link worked great, the program crashed when it ran. I was brought in to figure it out.
It turned out to be the C++ "static order initialization fiasco":
https://yosefk.com/c++fqa/ctors.html#fqa-10.12
If you've ever seen it, C++ crashes before main(). Why? Because ctors are getting run before main(), but before other dependent statics have been constructed.
Changing the linking order of the binary objects fixed it. Remember nothing else failed. No compiler or linker errors/warnings at the time, no nothing. But one was a valid C++ program and one was not.
You might think that is inflammatory, but I considered that behavior insane, because main() hadn't yet even run, and the program cored leaving me with trying to figure out what went wrong.
>> Furthermore, you don't want exceptions in kernel code.
>Nobody said anything about C++ throw/catch exceptions.
I'd like to add that if you're finding yourself restricting primary language features (e.g. templates, statics ctors, operator overloading, etc.) because the implementation of those features are bad, maybe using that language is the wrong choice for the project you're working on.
After I read the C++ FAQ lite [1] and the C++ FQA [2], I realized the determinism that C provides is kind of a beautiful thing. And yes. For a kernel, I'd argue C over C++ for that reason.
[1] C++ FAQ Lite: http://www.dietmar-kuehl.de/mirror/c++-faq/
[2] C++ Frequently Questioned Answers: https://yosefk.com/c++fqa/
I think that there are stronger arguments against C++: the continued presence of the complete C preprocessor restricting the effectiveness of automatic refactoring, the sometimes extremely cumbersome template syntax, SFINAE as a feature, no modules (yet!)...
Still, C++ hits a sweet spot between allowing nasty hardware-related programming hacks and useful abstractions in the program design.
So parsing your sentence. I'm right, and you're blaming me for not knowing a language as expertly as you. I can live with that.
Edited to add:
I admit it's a little snarky perhaps, but the c++ standard is 1300 pages long. It took my browser in 2018 1 minute to open it.
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n379...
I really do not have time to read a document like that to figure out whether or not that behavior is spelled out in the standard. So yes, I'll let you be the expert on this.
There are worse pitfalls than unstable order with static initializers specifically. If you dynamically load shared libraries at runtme on Linux, you risk static initializers being run multiple times for the same library. This is platform specific behavior that is AFAIK present on other UNIX systems as well and I'm certain that you won't find that in the standard.
Water under the bridge.
While I did say I was brought in to fix it, what I didn't say was that the group's management thought that Java coders could code in C++. D'oh.
It is funny how many issues people blame on C++ that are usually inherited from C semantics compatibility, or existing C extensions at the time C++ started to get adopted.
Let's try to write the equivalent of this error in C:
int myfunc() {
return 5;
}
static int x;
static int y = 4;
static int z = myfunc();
int main()
{};
main.c:8:16: error: initializer element is not constant
static int z = myfunc();
^~~~~~
Edited to add:
You're correct that 5.1.2 does not specify memcpy() as a form of initialization. But see my reply below about C11 and static storage classes.
That's why it gives you a compiler warning, and why your IDE marks it in yellow.
The same issue occurs in any language with static constructors, including Java.
Also add common C extensions into the soup like constructor function attributes.
Finally ISO/IEC 9899:2011, section 5.1.2.
"All objects with static storage duration shall be initialized (set to their initial values) before program startup. The manner and timing of such initialization are otherwise unspecified. Program termination returns control to the execution environment."
Don't mix what your compiler does, with what the standard requires.
Doing so only leads to unportable programs and misunderstandings.
Read section 6.7.9, constraint 4:
All the expressions in an initializer for an object that
has static or thread storage duration shall be constant
expressions or string literals.
And that makes sense. However the memory is initialized before runtime could be via memcpy() it could be loaded as part of the executable and then mapped dynamically at runtime. That's what 5.1.2 is saying.
What 6.7.9 constraint 4 is saying, is that static variables can only be constant expressions.
C++ has to run code before main if a ctor is in a class that's static. There's no other way to initialize that static object.
C prevents this by requiring static storage to be initialized with constants.
namespace {
int myfunc() {
return 5;
}
int x;
int y = 4;
int z = myfunc();
};
int main()
{}
For example, the dreaded singleton using a static variable inside a function:
Singleton& get_singleton() {
static Singleton instance;
return instance;
}
#include <stdio.h>
static volatile int* x; static int y = 42;
void __attribute__((constructor)) foo() { printf("[foo] x = %p\n", x); }
int main() { x = &y; printf("[main] x = %p\n", x); return 0; }
And before you complain about that being a compiler extension yes, it is, but it's also not rare, either, and you're probably using C libraries that do this.
[1]: https://www.geeksforgeeks.org/__attribute__constructor-__att...
e.g. All Linux kernel modules use this for initialising static structs for interfacing with the kernel.
void _start(){ / bla bla / exit(main(argc, argv)); }
The better I get at C++, the less of it I actually use.
In my opinion, it's better to not rely on static constructors for anything non-trivial (singleton or not). They can be such a pain in the ass to debug.
That applies to both C and C++ though.
The trick to use C++, is to use less of it. C with classes and namespaces. Oh and smart pointers.
- "In general case code should be readable to anyone who is familiar with C language". Why should it? C++ is a different language than C. I speak german, but I cannot read e.g. French unless I learned it even though they are related.
- "Don't use exceptions". Why? There is no performance penalty in the non-except case, and the exception case should be rare because it is exceptional. I can see arguments for real-time systems, and for embedded systems were code size matters. The alternative is C-style return codes and output parameters. Exceptions are better in that case because you cannot just go on after an error condition, and functions with output parameters are harder to reason about because they loose referential transparancy. Of course, in modern C++ one could use optional or expected types.
- "Don't use RTTI". I never needed RTTI in my professional life.
- "Don't use C++ runtime wrapper for C runtime includes". C++ wrappers have some benefits over the C headers. They put everything in namespace std, so you don't need to use stupid prefixes to prevent name clases, and they define overloads for some of the C functions, e.g. std::abs(int) and std::abs(long) instead of abs(int) and labs(long).
- "Don't use stream, use printf style functions instead". If this means to use a type-safe printf variant I could agree to some point, although custom operator(<<|>>) for custom types are sometimes nice. If it means to use C printf etc I would strongly object.
- "Don't use anything from STL that allocates memory, unless you don't care about memory management". You can use allocators to use e.g. pre-allocated storage. The STL also contains more than containers, why would you not use e.g. the algorithms and implement them yourself?
Systemd uses it: https://github.com/systemd/systemd/blob/5809f340fd7e5e6c76e2...
Some people rather use official language features.
... i suppose this project is locked into G-standard C++ and with lots of good reasons (e.g. toolchain). although i'm an anti-C++ person, i suppose the sorts of tools available internal to Alphabet make it much more manageable.
anyway, for an example of the original premise: i'm slowly learning some things about plan 9 C via 9front.. there are some departures from ANSI C, including additional features like (completely undocumented, except for the relatively compact source) operator overloading. equally important for the type of person that finds C++ too busy, some features (e.g. certain preprocessor features) are removed.
It makes managing any resource with acquire/release semantics very easy. It also prevents errors when the code is modified later because you cannot forget to call cleanup code as it is done automatically. I have no experience with kernel programming, but acquire/release seems to be something that is done in the kernel.
Agreed. But microkernels generally don't acquire or release resources. Most people arguing against this point seem to have a monolithic kernel mindset, but microkernels are a whole different beast.
If a kernel owns any kind of resources, that leaves the whole system vulnerable to denial of service attacks. Therefore, microkernels have long since adopted designs where the kernel does not own or allocate anything, and all resources belong to processes (which incidentally makes identifying misbehaving processes easy, something not easy on UNIX kernels).
Any data the kernel requires for its operation is allocated at boot time and lives until the system halts.
You wouldn't be doing much memory management in such a kernel. And where you would, you wouldn't let it to C++.
- most C code compiles magnitudes faster than most C++ code (unless you don't use templates or the C++ stdlib)
- you need C headers anyway for the public API, because the C++ ABI is not standardized (and a mess), trying to do shared libraries with C++ would result in such abominations like COM
- about half of features that C++ adds on top of C only make sense if you do OOP and encourage bad practices
- C is a much simpler and "complete" language, there's less room for debating about coding style, what C++ subset to use etc... (that's one thing that Go got right).
Also, Eric S.Raymond's "informed rant" on C++ is relevant: http://esr.ibiblio.org/?p=7724
I'd really like to see a simple language which fixes C's (very few) flaws succeed, but C++ ain't that.
Most of the problems C++ has are coming from being backward-compatible with outdated language features, explicitly the C-subset. Even the problems with the toolchain are more less inherited from the C compile-link model and its use of the preprocessor as a "module" system.
If you use the language as intended, e.g. in the C++ core guidelines, you will se very nice language emerging which enables to write very efficient and elegant code, sometimes doing things that C cannot do, such as expression templates.
JavaScript is also an ongoing effort to extract and evolve a good working language out of a mass of features. It's obviously doable, but not easy, and there are a lot of problems in practice.
Formal verification is one reason. There is still no formal model of C++ and C formal tools are light years ahead.
Huh? NT has done this for 25 years.
I believe the NT kernel still checks permissions against ACLs for handles. This violates capability security, but you can build a capability OS on top of ACLs: http://www.webstart.com/jed/papers/Managing-Domains/
It's important standards, it's important sometimes (SOMETIMES) compatibility. But not all this stuff defined in POSIX it's important. POSIX sucks sometimes [2], only GNU can be worse about being bloated [3].
Only users which don't touch in code can think that Linux, POSIX and GNU are entities following principles based in simplicity. Linux following Unix guidelines? This only can be a joke of Linus.
Creating custom software, maintaining and other stuff on things THAT YOU DON'T UNDERSTAND has a massive cost. As well, the cost to understand complex things, it's even worse.
Sometimes it's even more simple re-inventing the wheel than understand why a wheel was build with a fractal design [4].
[1] Linux LOC overtime https://www.linuxcounter.net/statistics/kernel
[2] POSIX has become outdated http://www.cs.columbia.edu/~vatlidak/resources/POSIXmagazine...
[3] Code inflation about /usr/bin/true https://pdfs.semanticscholar.org/a417/055105f9b3486c2ae7aec2...
[4] The Linux Programming Interface https://doc.lagout.org/programmation/unix/The%20Linux%20Prog... (that cover of book has a reason and yes: it is what you think)
Ugh, tell me about it. Just dealing with a relatively simple situation where you've got signals coming in while reading a pipe is a hassle to get completely correct.
I am so there for an operating system API that is relatively simple and sane. Where writing correct programs is, if not the easy path, at least not the hard and obscure path.
That can't be very good for debuggability.
[1]: http://cr.yp.to/docs/selfpipe.html [2]: http://man7.org/linux/man-pages/man2/signalfd.2.html
Of course, it's pretty hard to deal with a setup like that from plain C + libc + libpthread code, so OSes shy away from it. But if your OS also has OS-global sandboxed task-thread pools (like macOS's libdispatch)—and people are willing to use languages slightly higher-level than C where tasks built on those thread-pools are exposed as primitives—then it's not out of the question to write rather low-level code (i.e. code without any intermediating virtual-machine abstraction) that interacts with such a system.
Wasn't QNX like that?
Edit: in essence QNX messages work like syscalls, with the difference that there are multiple "systems" that accept "syscalls". For what it's worth Solaris has quite similar IPC mechanism that is mostly unused.
Sure, you can use ALPC, but only by using undocumented unstable NT API...
Sigh.
I'm not convinced that even Google has the resources to build something like that successfully. Except perhaps if they target a very specific use case.
I'm certain you can find complexities and bloat in there too, if you look.
OS X has tons of weird quirks and compatibility mindfucks going back to their transition from OS 9 (all those .DS_Store and _filename files for "resource forks")
Backwards compatibility is #1 reason for increasing complexity. Apple is sometimes good in cutting away compatibility for the sake of cleaning up, but there are still weird issues poking now and then
hell the whole NSEverything is a compatibility thing with NextStep, which is long dead.
Which is the worst of both worlds.
It might not be backwards compatible but from a developers perspective it is nice to be able to reuse old knowledge.
I think Apple has been much better than MS or Linux in continously modernizing and upgrading what they have. On windows and linux things tend to become dead ends as new flashy APIs appear.
Sure old win32 and motif apps might still run but nobody really develops using these APIs anymore.
On windows I first use win32, then MFC, then it was WinForms. Then all of that got depricated and we got WPF, silverlight and then I sort of lost track of what was going on. Meanwhile on Linux people used tcl/tk for GUIs early on. And there was motif, wxeindows. KDE and Gnome went through several full rewrites.
If we look at MacOS X as the modern version of NeXTSTEP the core technology has been remarkable stable.
Sure they have broken compatibility plenty of times but the principles and API are at their core the same.
One just needs to look into the right spot.
I don't have much experience with them but I think VxWorks and QNX are good examples of simpler OSs. I do have some experience with Minix3 and it is certainly one. I guess the BSDs stand somewhere in the middle.
In theory it makes me wonder if iphone's storage is slightly faster than the latest galaxy or if the process by which one loads an iphone app is slightly faster/more efficient than the one by which an android app is loaded or if the tiny selection of apps the reviewer picked are just better optimized for iphone. Nobody smoked anyone and nothing of note was learned by anyone. So much so that I wonder why you bothered to watch said link or paste it here.
I said half an OS because its built on technologies like linux and java not because its half assed even though it is.
Certain apps were slower to load on the Samsung device. Additionally, the Samsung device encoded the 4K siginificantly video faster and took round 1 by 14 seconds and round 2 by 16 seconds.
>In theory it makes me wonder if iphone's storage is slightly faster than the latest galaxy or if the process by which one loads an iphone app is slightly faster/more efficient than the one by which an android app is loaded or if the tiny selection of apps the reviewer picked are just better optimized for iphone. Nobody smoked anyone and nothing of note was learned by anyone. So much so that I wonder why you bothered to watch said link or paste it here.
The iPhone X has faster storage and a significantly faster SoC. A 30 second win by the Samsung phone is what I could call getting smoked.
>I said half an OS because its built on technologies like linux and java not because its half assed even though it is.
And iOS is was a decedent of MacOS which itself is a decedent of NeXTSTEP. It also uses a language 11 years older than Java. So it sounds like iOS also meets your criteria of being "half assed".
Didn't Mach start out as a replacement kernel for BSD? Building a Unix on top of Mach is like building a truck over truck chassis.
In late 80's/early 90's there were various projects that attemted to build unix on top of that as true micro kernel architecture with separate servers for each system service. Performance of such design was horrible and there are two things that resulted from that that are still somewhat relevant: running whole BSD/SysV kernel as Mach task, which today means OS X and Tru64 (at the time both systems had same origin as both are implementations of OSF Unix) and just ignoring the problem which is approach taken by GNU/Hurd.
Worth noting that's because Mach IPC is extremely slow, an order of magnitude slower than L4 family.
Next's VP of Software Engineering, Avie Tevanian, was one of the Mach project leads. Richard Rashid, who lead the Mach project ended up running Microsoft Research's worldwide operations.
Their work on a virtual memory subsystem got rolled back into BSD.
https://en.wikipedia.org/wiki/Mach_(kernel)
The Computer History Museum has an interesting long form interview with Avie:
Part 1: https://www.youtube.com/watch?v=vwCdKU9uYnE Part 2: https://www.youtube.com/watch?v=NtpIFrOGTHk
Google CAN'T do something small, simple and elegant, partly for the very reason that they're too big.
Had Go been released at AT&T and it would have shared the same fate as Limbo.
This is beyond belief. What companies are using Go with the hopes of being acquired by Google? Does anyone honestly believe that Google's acquisitions teams know or care about programming languages? Any business that acquires companies on that basis is doomed to failure, as is any company that hopes to be acquired on that basis.
So, quite a lot if that experience is anything to go by.
They obliged with a full crate of first generation Motorola phones, each one preloaded with a 30 day free Verizon plan. Every person who took that class got one, and surely all of them made it back into the school's hands at the end of the quarter.
(I'm not sure how many people actually ever compiled and executed any go binaries on arm that year; we all learned Go, and it was a great class! But as far as the class, the phones were completely unnecessary. I think that they did make a more relevant class where the phones were able to be used again the year after that.)
Systems does mean that. There are 2 broad categories of software you can write. One is software that provides a service to the user directly. That is an application. The other kind is software that provides a service to applications. That's systems software. Do you think there's something wrong with this notion? It's pretty well accepted over the decades:
https://www.linux.com/news/event/open-source-summit-na/2017/...
In the video, it is show that the binary size of "core" linux has barely grown
I agree that there is much to be explored yet in OS design. However it needs deep pockets to actually support wide array of hardware. Or a long time.
I cheer for Toybox and Oil shell regarding the GNU userland.
When I see all the openat(2) and friends family of functions or chmod/fchmod, chdir/fchdir, barbaz/fbarbaz I'm thinking that it all needs a bit of a clean up. Some batching system call would be appreciated as after Meltdown syscalls are more expensive.
I personally like and keep my fingers crossed for DragonflyBSD. They are doing things that are innovative while keeping conservative core for the lack of better words. But at the same time DragonflyBSD has minuscule hardware support comparing to Linux.
I don't know what this thing is, but it doesn't look very appealing.
Consider showing a webpage. You have a network stack, a graphics driver, and the threads of the actual browser process itself. It's substantially easier to about bottlenecking through one or more locks (for, say an open file table, or path lookup, etc) when the parts of the pipeline are more separated than a monolithic kernel.
Lock-free concurrency is also achievable.
Again, this isn’t the user land we’re talking about, in the sense that the kernel is expected to be highly optimized.
Granted, a multi process architecture does have virtues, like stability and security. But performance is not one of them.
Lock free concurrency is typically via spinning and retrying, suboptimal when you have real contention. It's better not to contend.
Kernel code isn't magic, its performance is dominated by cache just like user space.
High performance applications get the kernel out of the way because it slows things down.
Lock free concurrency is typically done by distributing the contention between multiple memory locations / actors, being wait free for the happy path at least. The simple compare-and-set schemes have limited utility.
Also actual lock implementations at the very least start by spinning and retrying, falling back to a scheme where the threads get put to sleep after a number of failed retries. More advanced schemes that do "optimistic locking" are available, for the cases in which you have no contention, but those have decreased performance in contention scenarios.
> Handing off means to stop using it and letting someone else use it. Only copy in rare cases.
You can't just let "someone else use it", because blocks of memory are usually managed by a single process. Transferring control of a block of memory to another process is a recipe for disaster.
Of course there are copy on write schemes, but note that they are managed by the kernel and they don't work in the presence of garbage collectors or more complicated memory pools, in essence the problem being that if you're not in charge of a memory location for its entire lifetime, then you can't optimize the access to it.
In other words, if you want to share data between processes, you have to stream it. And if those processes have to cooperate, then data has to be streamed via pipes.
> High performance applications get the kernel out of the way because it slows things down.
Not because the kernel itself is slow, but because system calls are. System calls are expensive because they lead to context switches, thrashing caches and introducing latency due to blocking on I/O. So the performance of the kernel has nothing to do with it.
You know what else introduces unnecessary context switches? Having multiple processes running in parallel, because in the context of a single process making use of multiple threads you can introduce scheduling schemes (aka cooperative multi-threading) that are optimal for your process.
It's possible to be more efficient at showing a bit of text and graphics which is what mobile phones do a lot more of than raw number crunching, except for games, except for games of course.
Not sure about display though, but don't expect monolithic kernel to help here somehow either.
GPUs don't have much security at all, there is lots of DMA or mapped memory. Though on most modern monolithic kernels a lot of this work is either in modules (AMDGPU on Linux is usually a module not compiled into the kernel) or even userspace (AMDGPU-Pro in this case). Mesa probably also counts.
Microkernels aren't the ideal kernel design. Monolithic isn't either. I put most of my bets on either Modular Kernels if CPUs can get more granual security (MILL CPU looks promising) or Hybrid Kernels like NT where some stuff runs in Ring 0 where it's beneficial and the res in userspace.
Of course they can share an interface, I even pointed out the vale switch as an example of this [1]. And it is very fast.
The thing is isolation and granularity that microkernels happen to have force certain design and implementation choices that benefit both performance and security on modern systems. And monolithic kernels while theoretically can be as fast and as secure actually discourage good designs.
[1] http://www.openvswitch.org/support/ovscon2014/18/1630-ovs-ri...
I also severely doubt that microkernels encourage efficient design. I'll give you secure but it's not inherent to microkernels either (NT is a microkernel, somewhat, and has had lots of vuln's over the years, the difference between microkernels and monolithic or hybrids like NT is that most microkernels don't have enough exposure to even get a sensible comparison going)
IMO microkernels encourage inefficient designs as everything becomes IPC and all device drivers need to switch ring when they need to do something sensitive (like writing to an IO Port unless the kernel punches holes into ring 0 that definitely don't encourage security).
Monolithic kernels don't necessarily encourage security but definitely efficiency/performance. A kernel like Linux doesn't have to switch priv ring to do DMA to the harddisk and it can perform tasks entirely in one privilege level (esp. with Meltdown, switching ring is a performance sensitive operation unless you punch holes into security).
I don't think monolithic kernels encourage bad design. I think they are what people intuitively do when they write a kernel. Most of them then converge into hybrid or modular designs which offer the advantages of microkernels without the drawbacks.
A monolithic, hybrid or modular kernel can significantly reduce this overhead while still being able to employ the same methods to amortize the cost that exists.
A microkernel is by nature incapable of being more efficient than a monolithic kernel. That is true as long as switching processes or going into priv has a non-zero cost.
The easy escape hatch is to allow a microkernel to run processes in priv ring and in the kernel address so the kernel doesn't have to switch out any page tables or switch privs any more than necessary while retaining the ability to somewhat control and isolate the module (with some PT trickery you can prevent the module from corrupting memory due to bugs or malware)
It's not an automatic security win.
So from a security standpoint MacOS X is mostly in the kenel camp, not the microkernel one.
The project at Carnegie Mellon ran from 1985 to 1994, ending with Mach 3.0, which is a true microkernel. Mach was developed as a replacement for the kernel in the BSD version of Unix, so no new operating system would have to be designed around it. Experimental research on Mach appears to have ended, although Mach and its derivatives exist within a number of commercial operating systems. These include all using the XNU operating system kernel which incorporates an earlier, non-microkernel, Mach as a major component. The Mach virtual memory management system was also adopted in 4.4BSD by the BSD developers at CSRG,[2] and appears in modern BSD-derived Unix systems, such as FreeBSD.
https://unix.stackexchange.com/a/223763
With regards to POSIX, it is amazing how well this API is holding up. There are quite a few implementions from GNU, BSDs, Microsoft (at least partial support in MSVC) and a few others (e.g. musl). So POSIX support is a given on most systems. Why replace it with something that breaks existing code?
https://www.musl-libc.org/faq.html
Not to say there is no bloat. But some bloat is the patina that all succesful systems take on over time. Is the bloat small enough to be managed and/or contained? I say yes.
You're not necessarily breaking existing code. Both macOS and Windows are built on non-POSIX primitives that have POSIX compatibility layers.
It seems that the conclusion most of industry has reached is that, whether or not POSIX is a useful API for your average piece of software, there are still better base-layer semantics to architect your kernel, IPC mechanisms, etc. in terms of than the POSIX ones. You can always support a POSIX "flavor" or "branded zone" or "compatibility subsystem" or whatever you want to call it, to run other people's code, after you've written all your code against the nicer set of primitives.
An potentially-enlightening analogy: POSIX is like OpenGL. Why do people want Vulkan if OpenGL exists? Well, because Vulkan is a more flexible base-layer with better semantics for high-efficiency use-cases. And if you start with Vulkan, the OpenGL APIs can still be implemented (efficiently!) in terms of them; whereas if you start with an OpenGL-based graphics driver, you can't "get to" (efficient) Vulkan support from there.
All that aside, though, I would expect that the real argument is: Fuchsia is for ChromeOS. Google are happy to be the sole maintainers of ChromeOS's kernel and all of its system services, so why not rewrite them all to take advantage of better system-primitive semantics? And Google doesn't have to worry about what apps can run on a Fuchsia-based ChromeOS, because the two ways apps currently run on ChromeOS are "as web-apps in Chrome", or "as Linux ELF executables inside a Linux ABI (or now also Android ABI) sandbox." There is no "ChromeOS software" that needs to be ported to Fuchsia, other than Chrome itself, and the container daemon.
If all you wanted to do was support chromeOS - well, typically you can add hacks even to a messy codebase to support specific usecases. And there are a bunch of linux and ?BSD distros that demonstrate that you can adapt such a system to even very small devices; small enough that there's not much niche left below. Moore's Law/Denard scaling may be comatose on the high-end; but lot's of long-tail stuff is generations behind; which implies that even really low-power IoT stuff that linux is currently ill-suited for will likely be able to run linux without too many tradeoffs. I mean; the original raspberry pi was a 65nm chip@700MHz - that's clearly overkill; and even if chip development never has a breakthrough again, there's clearly a lot of room for those kind of devices to catch up, and a lot of "spare silicon" even in really tiny stuff once you get to small process nodes.
But "being able to run linux" doesn't mean it'll be ideal or easy. And efficiency may not be the only issue; security; cost; reliable low latency... there are a whole bunch of things where improvements may be possible.
I'm guessing Fuchsia is going to be worse than linux for ChromeOS - in the sense that if ChromeOS really was what google wants it for, they could have gotten better results with linux than they'll be able to get with Fuchsia in the next few years and at a fraction of the cost. Linux just isn't that bad; and a whole new OS including all the interop and user-space and re-education pain is a huge price to pay. But the thing is: if they take that route they may end up with a well tuned linux, but that's it.
So my bet is that you'd only ever invest in something like Fuchsia if you're in it for the long run. They're not doing this "for" ChromeOS, even if that may be the first high-profile usage. They're doing this to be enable future savings and quality increases for use cases they probably don't even know they have, yet. In essence: it's a gamble that might pay off in the long run, with some applicability in the medium term - but the medium term alone just doesn't warrant the investment (and risk).
ChromeOS has already gained the ability to run containerized Android apps; and is expecting to begin allowing developers to publish such containerized Android apps to the Chrome Web Store as ChromeOS apps. This means that Android apps will continue to run on ChromeOS, without depending on any of the architectural details of ChromeOS. Android-apps-on-Android prevent Android from getting away from legacy decisions (like being Linux-based); Android-apps-on-ChromeOS have no such effect.
I suspect that in the near term, you'll see Google introducing a Chrome Web Store for Android, allowing these containerized, CWS-packaged Android apps to be run on Android itself; and then, soon after that, deprecating the Play Store altogether in favor of the Chrome Web Store. At that point, all Android apps will actually "be" ChromeOS apps. Just, ones that contain Android object files.
At that point, Google can take a Fuchsia-based ChromeOS and put it on the more powerful mobile devices as "the new Android", where the Android apps will run through Linux ABI translation. But in this new Android (i.e. rebranded ChromeOS), you'll now also have the rest of the Chrome Web Store of apps available.
Google will, along with the "new Android", introduce a new "Android Native SDK" that uses the semantics of Fuchsia. Google will also build a Fuchsia ABI layer for Linux—to serve as a simulator for development, yes, but more importantly to allow people to install these new Fuchsia-SDK-based apps to run on their older Android devices. They'll run... if slowly.
Then, Google will wait a phone generation or two. Let the old Android devices rot away. Let people get mad as the apps written for the new SDK make their phones seem slow.
And then, after people are fed up, they'll just deprecate the old Android ABI on the Chrome Web Store, and require that all new (native) apps published to the CWS have to use the Fuchsia-based SDK.
And, two years after that, it'll begin to make sense again to run "the new Android" on low-end mobile devices, since now all the native apps in the CWS will be optimized for Fuchsia, which will—presumably—have better performance than native Android apps had on Android.
Seems more likely they'll allow HTML apps into the Play Store, eventually getting rid of the Web Store entirely. They've already done the WebAPK stuff to glue HTML apps into Android.
But they wouldn't keep the current content of the Play (Software) Store. The fact that every Android store—even including Google's own—are festering pits of malware and phishing attempts, is a sore spot for Google. And, given their "automated analysis first; hiring human analysts never (or only when legally mandated)" service scaling philosophy, they can't exactly fix it with manual curation. But they would dearly love to fix it.
Resetting the Android software catalogue entirely, with a new generation of "apps" consisting of only web-apps and much-more-heavily-containerized native apps (that can no longer do nearly the number of things to the OS that old native apps can do!) allows Google to move toward a more iOS-App-Store-like level of "preventing users from hurting themselves" without much effort on their part, and without the backlash they'd receive if they did so as an end unto itself. (Contrast: the backlash when Microsoft tried that in Windows 8 with an app store containing only Metro apps.)
I expect that the user experience would be that, on Fuchsia-based devices, you'd have to either click into a "More..." link in the CWS-branded-as-Play-Store, or even turn on some setting, to get access to the "legacy" Play Store, once they deprecate it. It'd still be there—goodness knows people would still need certain abandonware things from it, and be mad if it was just gone entirely; and it'd always need to stick around to serve the devices stuck on "old Android"—but it'd be rather out-of-the-way, with the New apps (of which old Chrome Apps from the CWS would likely be considered just as "new" as newly-published Fuchsia apps upon the store's launch) made front and centre.
> Seems more likely they'll allow HTML apps into the Play Store, eventually getting rid of the Web Store entirely.
I would agree if this was Apple we were talking about (who is of a "native apps uber alles" bent) but this is Google. Google want everyone to be making web-apps rather than native apps, because Google can (with enough cleverness repurposed from Chrome's renderer) spider and analyze web-apps, in a way it can't spider and analyze native apps. Android native apps are to Google as those "home-screen HTML5 bookmark apps" are to Apple: something they wish they could take back, because it really doesn't fit their modern business model.
Lol, citation needed.
Ironically they have two sessions named "The future of the Android app model and distribution on Google Play".
That would be lost which is a huge deal. The new gnu/Linux on ChromeOS would be fine as it runs on a VM and would still work.
Now they could move Android to using a VM but that it less efficient and most importantly takes more RAM and CBs do not normally have a ton of RAM.
In fact, starting with Android 7 they have started to lock down NDK apps that try to use APIs not listed as stable.
I was under the impression that MacOS was built from a POSIX kernel, all the way down.
XNU does embed BSD (and so POSIX) semantics into the kernel—some of which are their own efficient primitives, since there's no way to efficiently implement them in terms of Mach. But whatever BSD syscalls can be implemented kernel-side in terms of Mach primitives, are.
I am not convinced a micro kernel would be able to achieve.
POSIX says that usernames and uids can overlap, and if a program takes either, it should accept the other a well. And if something could be a username or uid, it should be presumed to be a username, and resolved to a UID.
Now assume you have a user "1000" with uid 2000, and a user "2000" with uid 1000... you can see where this goes.
And this is why the BSDs have broken POSIX compatibility and require uids to be prefixed with # when they’re used on the CLI.
Nor is what you claim about the BSDs true. Aside from the fact that using the shell's comment character would be markedly inconvenient, especially since the colon is a far better choice for such a marker (c.f. Gerrit Pape's chpst), the OpenBSD and FreeBSD implementations of chown and newgrp do not have such a marker either documented or implemented, and in fact operate as the SUS says.
User names and user IDs are, by contrast, explicitly called out by the standard as strings and integers, two quite different things which have no overlap.
* http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_...
* http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_...
What a nice analogy.
Because POSIX has horrible security properties, and does not provide enough guarantees to create truly robust software. See for instance, the recent article on how you simply cannot implement atomic file operations in POSIX -- sqlite has to jump through 1,000 hoops to get something pretty robust, but it shouldn't be this way.
The goal is to avoid blocking, not to offer async also. That's a lost cause.
Fuchsia once had the goal to offer async only, but then some manager decided that he needs some blocking, and then it was gone.
non-blocking only is lower level than blocking. You can always wait indefinitely for that callback, but usually you have a default timeout. L4 for example offers that API.
You don't need async for a proper concurrent system. Systems have been concurrent before async IO. The trick is that when a process does an IO you yield it and put it on a wait list and run literally anything else until the kernel receives the OK from the hardware control and resumes the process.
Using Async IO in Linux merely means your specific thread won't be immediately suspended until you get data (or it's in a reasonably close cache)
It would be quite silly if Linux would wait for every IO synchronously, any single core system would immediately grind to a halt.
http://pubs.opengroup.org/onlinepubs/009695399/basedefs/aio....
But Async IO is part of POSIX.
I was mostly responding to the comment which cited synchronous IO as a problem with POSIX. Linux is most widely used so on top of being my primary domain on the issue, it's going to ensure best understanding.
See here: https://linux.die.net/man/7/aio
AFAIK, system-specific APIs such as epoll or kqueue are the way to go if you're serious about performing asynchronous IO?
> Linux kernel has Async IO
In a fully async platform you would be able to do general-purpose programming without ever needing to use multithreading.
Example of a situation you can't do in linux: have a program doing select(2) or equivalent on both keyboard input and network input, in a single thread.
Since linux does not support this, you are steered to adapt solutions that are more complicated than a pure async model would be,
* Spin constantly looking for activity. These heats up your computer and uses battery.
* Have short timeouts on epoll, and then glance for keyboard input. This leads to jerky IO.
* Have child processes block on these operations and use unix domain sockets to feed back to a multiplexor (fiddly, kernel contention).
* The child-process thing but with shmem (fiddly)
* Something equivalent to the child process thing, but with multiple threads in a single process. (fiddly)
You would think that x-windows might help out here. What if you had a socket to X, and then multiplexed on that, instead of looking for keyboard input from a terminal? This opens new issues: what if X has only written half of an event to your socket when select notifies you? Will your X library handle this without crashing?
Rurban's comment above is correct. Linux is not async throughout.
On OSs that offer kevent you can get a fair bit further, but (I believe) you still can't do file creation/deletion asynchronously.
You're not the only task running.
Or do you expect Linux to pause the system when you read a file until the DMA is answered?
Linux itself is fully async, anything blocking (even interrupts to some extend) will be scheduled to resume when the reason it blocked is gone or alternatively check back regularly to resume.
A program running on Linux can do a lot of things async as mentioned via POSIX AIO. It's not impossible, go seems to do fine on that front too (goroutines are put to sleep when doing blocking syscalls unless you do RawSyscall).
The conclusion that lack of 100% asynchronity means it can't be properly concurrent is also wrong. As evident that sending something to disk also doesn't not halt the kernel.
POSIX is a lowest common denominator API, its under specified and loosely interpreted. Which follows from its initial goals, which was basically to specify the bits common between various UNIX implementations. Those implementations obviously didn't want to change their implementation to match a rigid standard, so a lot of wiggle room exists in the standard.
The end result is that is pretty much useless for anything beyond "hello world" kinds of applications, both in terms of portability, as well as actual behavior (I could list a lot of cases, but lets leave that to google, with the starting idea to look at a couple posix API's, say close()'s errno's and the differing cases and what causes them on different OS's/filesystems). That is why there isn't a single OS out there that is _ONLY_ POSIX compliant. You need look no further than the 15 year old https://personal.opengroup.org/~ajosey/tr28-07-2003.txt and consider that the gap has widened as more performance or security oriented core API's have been introduced and linux's POSIX layer is further refined upon them.
Plus, the core API's in no way reflect the hard reality of modern hardware, leaving the standard even more under specified in the case of threads and async IO, which have been poorly bolted on.
Then there are all the bits everyone ignores, like the bits about the posix shell (ksh), and how certain utilities behave, while completely ignoring important things like determining metadata about the hardware one is running on.
I leave you with: https://stackoverflow.com/questions/2693948/how-do-i-retriev...
and https://stackoverflow.com/questions/150355/programmatically-...
Which is pretty basic information about a modern machine.
Only useful for CLI tty old style apps and daemons.
I quite like Linux but I would not say the current state of the core kernel is "really" nice. Somewhat nice, maybe, but "really" nice? You just have to look around to see exemples of non-nice things (too much things in some headers, jumping between source files back and forth for no reason, excessive use of hand coded vtables, internal "framework" that are not as simple as they should, at other time lack of abstractions and excessive access to internals of structures, etc). Granted, it is way less buggy than some other softwares, but I think I'll know when I read a really nice core, and for now I've never had the feeling that Linux has one.
Still find it quite good, to be clear.
https://github.com/mpv-player/mpv/commit/1e70e82baa9193f6f02...
https://doc.lagout.org/ looks quite shady, so I guess someone uploaded their copy without copyright holder's permission.
When I saw your comment I immediately was reminded of Joel on Software: "The single worst strategic mistake that any software company can make is to rewrite the code from scratch."[1]
[1] https://www.joelonsoftware.com/2000/04/06/things-you-should-...
Althought in OS space one might argue that second generation of time sharing OSes (TOPS-10, ITS, MCP...) got more things right than are right in Unix and such.
A rewrite made no sense to me since I'd end up maintaining version A alongside version B with B constantly lagging A unless I severely restricted the scope of B in which case it'd be an incomplete (though better written/more maintainable A).
Instead I went the isolate (not always easy), shim, rewrite, replace, remove shim approach.
It does feel a bit like spinning plates blindfold sometimes in the sense I'm always expect to hear a crash.
So far I've replaced the auth system, the reports generation system, refactored a chunk of the database, implemented an audit system, changed the language version, brought in proper dependency management, replaced a good chunk of the front end (jquery soup to Vue/Typescript), rewritten the software that controls two production units and implemented an API for that software so that it isn't calling directly into the production database.. and done it without any unplanned down time (though I'm still not sure how - mostly through extensive testing and spending a lot of time on planning each stage).
It's slower because I have to balance new features against refactor time but I have management buy-in and have kept it, mostly through been extremely clear about what I'm working on and what the benefits are and have built up some nice momentum in terms of deploying new stuff that fixes problems for users.
The really funny part is that even though I'm re-factoring ~40% of the time I'm deploying new features faster than previous dev who wrote the mess...because I spent the time fixing the foundations in places I knew I'd need for new features going forwards.
If you're Google and you have people with these abilities kicking about, it's probably not a crazy investment to see what happens. We've got a HN story elsewhere in the list on post-quantum key agreement experiments in Chrome, again there's a fair chance this ends up going nowhere but if I was Google if throw a few resources at this just in case.
But on the whole I expect Fuchsia to quietly get deprecated while Linux lives on, even if there's lots to like about Fuchsia.
Link for reference: https://news.ycombinator.com/item?id=16811554
1) Get yourself placed on the "Legacy team" that is supposed to "minimally support the application while we transition to the new system".
2) Do whatever the hell you want with the code base (i.e., refactor as much as you want) because nobody cares about the boring legacy system.
3) Respond directly to user/customer needs without having to worry about what upper management wants (because they are distracted by the beautiful green-field rewrite).
4) Retain your job (and probably get a promotion) when they cancel the rewrite.
1) Get stuck on the "Legacy team", as expensive contractors are called in to produce the rewritten version from scratch in an unrealistically small fraction of the time the original took.
2) Be told you can only fix bugs (with more layers of short term hacks), not waste time with refactors that have "no business value" for a code base that will be scrapped "soon".
3) Don't add any new features, to prevent the legacy system becoming a perpetually moving target that would delay the beautiful green-field rewrite even longer.
4) Hate your job, and watch your coworkers leave in disgust, further starving the team of resources, until you end up quitting too.
The programmers with the political skills to get put in the "Rewrite team" will have had their jobs in the "Legacy team" protected in case of project cancellation. Or they will knife you in the back to get their old jobs back -- they will know about the cancellation and have plenty of time to maneuver before you know what's going on.
1) Get on the new team
2) Ensure to get into the more interesting tech modules
3) Improve your CV
4) Use your soft skills to mingle with everyone and be aware of where the wind blows
5) In case of iceberg ahead, jump ship to a better job taking advantage of the new skills
1) Do a startup
1) Quit job 2) move to the woods 3) shun all electrical devices 4) mediate until you become one with the universe
Firefox started as a fresh UI reskin for the old browser interface, and indeed continued as "mostly a skin" for years (incidentally, so did Chrome).
(You can still get the non-firefox skin incidentally, it's "Mozilla Seamonkey")
Then the Rust rewrite. Rust was a hobby project, and they rewrote layout engine interface, and nothing more than that. Then CSS.
Now it's an HTML parser, a layout engine, a parallel CSS engine, and a GPU webpage renderer (still "missing"/non-rust are 2d compositing and javascript). Each of those components replaced another in a working version and there were at least beta versions of firefox of all the parts.
Mainly, I'm just getting tired of people trying to cut things out of the solution by cutting them out of the problem.
Saying that it's possible to solve a problem in a simpler fashion is fine. Saying a problem shouldn't be solved, that nobody should have that problem, so therefore we won't solve it, is not fine if you then turn around and compare your cut-down solution to the full solution.
And the borrow checker, along with move semantics by default and the Send and Sync traits, help with several other aspects of safety as well; the Send and Sync traits encode information on what can safely be moved or shared between threads, and move semantics by default (and checked by the compiler, instead of at runtime as in C++), make it easier to encode state transitions on objects in ways that you can't try to perform operations on an invalid state.
But as others point out, Zircon, the Fuchsia kernel, was written before Rust 1.0 was released, and even after Rust 1.0 was released and stable it was still a bit rough to work with for a little while.
If you were starting a new project from scratch today, I'd seriously ask why not Rust, though of course there are other reasons why you might not choose it. But given the history, and how new Rust was at the time when this project was started, it makes a lot of sense.
While I'm not saying that rust is bad, Rust as a kernel language won't help you here. The simple proof is that Redox-os (which is a microkernel built in Rust) was found with the same class of bugs your average OS had.
Source? I haven't heard about these vulnerabilities.
In a kernel, there are several places where Rust won't help you. There are certain things you have to do that are going to need unsafe code, and need to be audited just as much as code written in any other language. The kernel is also a place ripe for logical vulnerabilities to creep in; it is the main arbiter of what is allowed and is not allowed from processes, so many possible vulnerabilities are logical, not memory safety issues.
On the other hand, when a kernel gets complex enough, there are places where memory safety or thread safety issues can come up even in code which doesn't require particular unsafe features and which is not involved in a security role; just things like manipulating complex data structures in multiple threads. This kind of code is the kind of code in which Rust can help catch issues; and it definitely still happens even when very good programmers, with good code review, work on the kernel.
Rust is not a panacea; it is not a cure-all. But it reduces the attack surface considerably, by containing the amount of code that is exposed to certain very common classes of bugs.
Edit: to clarify ... I don't mean that they won't be able to understand the concepts ... I mean that they will lose a lot of productivity up front and won't appreciate the backend gains enough for there to be a political consensus to switch.
One of the advantages of a microkernel architecture is that it is relatively easy for different components to be written in different languages.
Fuschia will become another monolith where the assumptions no longer matter given tech of 2035 or whatever, and something new will happen
IMO the better model would be a simple hardware BIOS type thing with a standardized build system embedded that enables completely custom environment builds from whatever source repo people want
These big monoliths seemed more valuable in a pre-internet is everywhere world, so they include the kitchen sink too
I’m talking to the commentary about a dated cultural artifact sucking, championing of new hotness, a new culture that will develop around it and eventually fade as technology changes and the peddlers of the latest and greatest will largely say the same “wtf @ this mess”
But downvote reality of human progress that has occurred over and over
The opinionated nature of humans is bizarre, given that we keep, in a social way, repeating our dead relatives
We can fix the future from a past that won’t live to see it
It’s all nonsense for the majority of humans, but this little microcosm called HN has its finger in the pulse of what we’ll need in 2040!
1. They want a modular microkernel OS with modern capabilities.
2. They want to eventually replace their internal Linux based OS with Fuchsia.
3. Fuchsia, or parts of it, will be the basis for all of their products.
4. They want to control the direction of their own OS.
It's not just the kernel design, it's the driver design as well. Fuschia has drivers being ELF binaries that hook into Device Manager process[0]. I believe they are developing a standard API for how drivers interact with Fuschia.
Linux doesn't really have this today, which means that the driver must be in the kernel tree to have it keep up with the kernel's interface. And with ARM lacking something like a BIOS for phones, each chip that Qualcomm et al make requires a full BSP to get it working. And from what I understand, Linus and others don't want these (relatively) short-lived processors to be checked into mainline linux (plus you have the lag time of that code being available). Android's Project Treble[1] aims to address this some by creating a stable API for hardware makers to use to talk with Linux, but it is not an ideal solution.
[0] https://fuchsia.googlesource.com/zircon/+/HEAD/docs/ddk/over...
[1] https://android-developers.googleblog.com/2017/05/here-comes...
I don't think that's true. e.g. 4.17 is accepting code to run Samsung Galaxy S3 (released nearly 5 years ago). It is left to volunteers since most vendors dump a source release to comply with the GPL but themselves don't upstream it to Linus.
But, the core idea behind SBSA and SBBR is to form a common platform to which the vendors conform their machines so they don't have to keep up-streaming special little drivers for their special little SOCs. Only time will tell if its a success, but a large part of the community has effectively declared that they aren't really going to conform to the ideals of a standard platform. So, the ball keeps rolling and new DT properties keep getting added, and new pieces of core platform IP keep showing up. At this point arm64, despite just being a few years old already looks as crufty as much older architectures with regard to GIC versions, dozens of firmware interfaces, etc due to the lack of a coherent platform/firmware isolation strategy.
Problem solved!
Say what you will about how terrible POSIX is, Be recognized the tremendous value in supporting POSIX: being able to support the mounds and mounds of software written for POSIX. It chose to keep enough POSIX compatibility to make it possible to port many common UNIX shells and utilities over, while Be developers could focus on more interesting things.
So where were the problems?
One huge problem was drivers, particularly once BeOS broke into the Intel PC space. Its driver interface and model was pretty darn slick, but it was different, and vendors wouldn't support it (take the problems of a Linux developer getting a spec or reference implementation from a vendor and multiply). This cost Be, and its developer and user community, quite a bit of blood, sweat, and tears.
Another big problem was networking. Initially, socket FDs were not the same thing as filesystem FDs, which had a huge impact on the difficulty of porting networked software over to BeOS. Eventually, BeOS fixed this problem, as the lack of compatibility was causing major headaches.
The lesson: if you are looking to make an OS that will grow quickly, where you will not be forced to reinvent the wheel over and over and over again, compatibility is no small consideration.
A truck is not more complex than a car. A truck is bigger because it is designed to carry more load.
Yes the Linux kernel is bloated, bloated with tons of code responsible for making it work on exotic hardware. Yes x86 is bloated, let's just remove those useless AVX instructions. Yes MS Excel is bloated, who the hell is using all those features [1]?!
You can only have two alternatives : either your software is “bloated”, or then it will be replaced by something else, which is more “bloated” and works for more people.
Notice than I'm just criticizing the “bloat” argument, I'm just not criticizing Google for creating a new OS from scratch, which can bring a lot on the table, if done properly and includes innovations from the past 30 years, like was done when creating Rust for instance.
[1]: https://www.joelonsoftware.com/2001/03/23/strategy-letter-iv...
Google spends a lot of money on research. One thing about research is that a lot of stuff you do ends up completely useless in the short term even if you cover all your bases initially. Even if this project fails, I hope something good can be learned from why it failed; maybe someone in the future can learn from those mistakes and try again.
I'm certainly no fan of Google nor of the way they make money. But I am very happy they use that money for stuff like this.
It reminds me of NFL fans. No one talks trash about the crappy quarterbacks of their opponents teams. Everyone talks trash about Tom Brady, and Peyton Manning, Cam Newton, etc.
This is also a general negotiating tactic. Start with a bold initial offer, and then negotiate back to what you wanted in the first place.
Where did anyone say that Fuchsia was better than Linux?
The title of this document, "Fuchsia is not Linux", is a play on the "GNU's not Unix" backronym for the GNU project, as well as being a way of pointing out that unlike Android, Fuchsia is an entirely different kernel.
I mean, obviously they would write it because they thought it would be better for certain applications than Linux, or better for trying out new ideas, or the like, but I don't see anything claiming that Fuchsia is better.
In fact, Fuchsia has been done as a pretty low-key project for a while, slowly opening up parts but without much fanfare, just repositories being available, and slowly posting more documentation like the link in the OP. I don't really see very much marketing about it, just low key releases of code and more technical information to give people a taste and show the direction they're trying to go in.
As a nice byproduct Google has a hedge against Linus dying and his replacement being incompetent at managing the community.
https://k8s.devstats.cncf.io/d/8/companies-statistics-reposi...
(Disclosure: I'm executive director of CNCF. We also build that DevStats tool.)
The problem with legacy support is that it drags in the braindamage you were trying to avoid by rewriting the OS in the first place. But without legacy support it's almost impossible to grow beyond the toy OS stage. It's the whole "So, what do I do with it?" factor.
[1] https://discuss.haiku-os.org/t/fuchsia-a-new-google-kernel-c... [2] https://echelog.com/logs/browse/haiku/1471125600 [3] https://discuss.haiku-os.org/t/fuchsia-a-new-google-kernel-c...
It was super cool and could make these absolutely insane multimedia demos, but he was forever trying to get software to work on it. Whatever POSIX compatibility it had was absolutely insufficient for modern (at the time) applications. Everything required some rewriting by hand, and there were definitely crashes. Worse, Netscape didn't release a BeOS version of Navigator so he was always hacking up the latest Mosaic release to try to get it working. I was running FreeBSD at the time and it was the polar opposite. Sound barely worked, the only video players were slow and unreliable open sourced school projects, but it was front and center on the newfangled Internet thing that was going around at the time.
Google is also developing Fuchsia openly, if quietly, giving developers a preview of where they are going. Microsoft developed Midori mostly in secret, and while we've heard a little bit about what they did in that project from blog posts and Twitter threads, nothing official has ever been released publicly.
And on the server side, virtualization and containerization are huge and growing, as many people find the benefits in flexibility, repeatability of deployment, and incremental billing to outweigh the absolute overhead over bare-metal performance. Fuchsia seems to support virtualization as a core part of the API, allowing you to run Linux VMs when you need to, and it could be possible to port containerized applications piecemeal to Fuchsia with some components still running on Linux on co-located or even the same hardware.
I feel like this is one of the benefits of the relatively simpler POSIX style API design, and extensive use of sockets for IPC, over the fairly complex, heaviweight Win32 API and NT kernel. I feel like a lot more software that runs on Linux (and is generally portable to several other POSIX-ish OS's) would be a lot easier to port to Fuchsia, and in an incremental way, than all of the software that runs on Windows systems would be to port to Midori.
Joe mentioned at his Rustconf talk how hard it was to convince the Windows team, even with the system running in front of them.
When people are religiously against something, no amount of technical achievements is going to change their mind.
RustConf 2017 - Closing Keynote: Safe Systems Software and the Future of Computing by Joe Duffy
https://www.youtube.com/watch?v=EVm938gMWl0
You can get more glimpses of how things went when reading between the lines on his Midori postmortem, InfoQ content or occasional twitter comments.
Ah, but that is exactly why I'm paying attention Fuchsia even though in general I ignore new OSes: it would not be hard for the organization behind Fuchsia to instruct the 1000-or-so developers it employs who maintain a web browser to make the web browse runs on Fuchsia.
(and it is open-source).
Is that a hint that Fuchsia is a VR-first operating system?
(This is my assumption anyway - I haven't tried running it)
Android already does physically correct soft shadows in real time.
The initial design of material would have allowed way more space manipulations, like making a view rotate on any axis.
So the shadow implementation allows to remain correct even in this kind of case.
It is kinda sad that the final design forbids this, a simple raster shadow would have been enough to just signify the elevation.
Augmented reality pretty much requires us to shrink displays down to contact lens sizes because we already figured out almost nobody will pay to strap a smartphone to their face.
Then it requires us to create and popularize an entire new method of interacting with your computer.
Then this needs to be cheap enough to get in everyone's hands.
It would be surprising if this only took 20 years.
This is about drawing dumb drop shadows.
We could argue about the difference between OS and presentation layer but that battle may already be lost.
https://9to5google.com/2018/04/06/fuchsia-friday-graphics-ga...
Scenic will have support for what it’s calling “stereo cameras.” What this means is there can be two views into the same scene. Each camera can also be independently moved or turned for a different view. The most obvious reason for this capability is virtual reality.
https://msdn.microsoft.com/en-us/library/windows/desktop/aa9...
And it's what enables effects like this in Windows 10:
https://docs.microsoft.com/en-us/windows/uwp/design/style/re...
Disclaimer: I work for Microsoft
[1]: https://material.io/guidelines/material-design/elevation-sha...
I'm assuming the Fuchsia development is 100% about not having to use any GPL software. Look how hobbled the Android and ChromiumOS communities are compared to the Linux world at large.
As soon as someone outside of Google produces anything of any novelty around Fuchsia, I might change my mind, but for now I'm viewing it as a going-nowhere software project that's all hype and will never be 100% Free and Open Source.
This. Everyone wants to distance themselves from the GPL. The reality is that the ideas the 90s open source movements were founded on are far from what we see today. We don't see OSS end user applications; at least not a lot in mainstream use. Instead, we just see OSS middleware.
In the early 2000s, people though one day we'd see Gimp be on par with Photoshop and StarOffice/Libreoffice take on Word and Excel. We've come a long way, but those ideas were never realized.
Are they ? GPL is about protecting users' freedom. It's still a valid aim to me, probably even more so.
What has changed is that the web is much bigger than the desktop and so the GPL has less ground to grow on, so its effect may have been weakened. But only the effect, not the goal.
(I 100% admit I am more an idealist than a pragmatic)
So most important corporations, etc. Copyleft was a very clever idea; but deciding to go to war against all intellectual property was a step too far. Immense billions have been spent already replacing GPL software with truly free software under a freer, more liberal license.
But those activists still exist, and their code is still written in GPL to avoid being “weaponized” by big corporations. The main difference is that they don't need to write all the tools they need on their own, since private corporations now release open-source code. And because of that, it's easier than ever to run with almost 100% free software on your desktop.
These people never _thought_ “StarOffice/Libreoffice take on Word and Excel”, they _wished_ there would be a political movement that make it happen, like socialists wish the Revolution occurs. And in the 90ies − early 2000s it really looked impossible, because the technical challenge was too big: everything had to be built from scratch to compete with a relentless private industry that kept moving forward: even the _programming language_ and the build tools were proprietary. RMS wanted to write a free printer driver, and first he had to the whole GNU stuff, with GCC and Emacs!
If you look where we are now, you can see it's way better ;).
If Google wanted to avoid GPL software, they could have used a BSD UNIX successor. It certainly would have been far easier to do.
And for that reason, as an end-user, I’d be extremely weary of buying any Fuchia-based device.
You can be 100% assured the source for the required HW-drivers to use the device for anything else wont be available.
The biggest sin of Linux API remains ioctl (and its variants). Zircon commits the same mistake with its `object_get_prop` [1] and `object_get_info` [2]. If you pretend to be type safe (have different getters for different obj-types), you can in the long run replace these calls with in-userland static calls where possible to accelerate performance (like linux does for futex and time).
Instead you get his "It does A if you give it B, it does C if you give it D" this is pretty bad API design as it NEEDS a void pointer. I'd rather see _a lot_ of simple with numbers related to the call. You have 4 million of them FFS (if you care about 32bit compatibility).
It just leaves a bad taste in my mouth. The API design is extremely nice otherwise, and these methods feel like such an after thought.
---
To be clear I really don't care about POSIX compatibility, its easy to shoe horn in after you have a solid OS. The Windows-NT kernel has done it twice now (NT4.0 and Windows10).
[1] https://fuchsia.googlesource.com/zircon/+/master/docs/syscal...
[2] https://fuchsia.googlesource.com/zircon/+/master/docs/syscal...
A lot of people say "capability based" and really mean some very fine grained access control system. (A confusion encouraged by POSIX "capabilities".) What I hope that they mean is the one that solves the https://en.wikipedia.org/wiki/Confused_deputy_problem
There are two VERY different meanings of the phrase. The one that I'm hoping for can be thought of like this.
OTOH the OP's table of contents gives me the impression that Fuchsia is more complex than the older capability OSes (KeyKOS family, seL4).
Highly recommend it.
Or is this just a research operating system designed to test new ideas out?
Other than that, for Google this would obviously bring total control over the codebase, allowing them to do whatever they want, and super quickly, not needing to convince Linus or anybody else.
- "capabilities": ok, I think I get the misunderstanding. The "capabilities" here are completely unrelated to "hardware capabilities" or "machine capabilities", a.k.a "what features does my phone have". The word has a totally different meaning in the technical jargon of OS development. It's a security architecture concept; as a first approximation, I'd say "capabilities" are somewhat akin to "permissions" on Android/iOS. You could maybe call them "permission lease": as an app, if you got some permission ("capability token"), you can choose to sublease/share/extend it to another app you run. See: https://en.wikipedia.org/wiki/Capability-based_security
- microkernels are a general architecture approach; they can perfectly well be used for regular server/desktop OS. It's just that writing a new OS for an embedded system is easier as a "first step", because you can start smaller. A full-blown "general purpose" server/desktop OS is much more complex; enough to say that it must have very wide driver support for shitloads of different hardware existing in the world. (But there are also other challenges, like multiple user management.) Microkernels were long believed to have worse performance than monolithic kernels in popular perception, thus their historical unpopularity. However, this notion was challenged by the L4 kernel (https://en.wikipedia.org/wiki/L4_kernel), which was I believe the reason for the revived interest. L4 was apparently published ~1993, and there was QNX long before that; I'm not actually sure why it hasn't become more popular earlier. Maybe unfamliarity to programmers? I believe microkernels enforce somewhat stricter development standards than monolithic kernels (where it's probably easier to "just hack around" and duct-tape a new feature), thus probably raising the perceived development costs somewhat (I believe it's similar as if we compared e.g. Rust vs. C/C++).
edit: ah, a good example could be the L4-based L4Linux (https://en.wikipedia.org/wiki/L4Linux) kernel, which is said to be a more or less "drop-in" replacement for the "classical" monolithic Linux kernel, so you should be able to run any Linux distro on it. Though I personally never tried it (yet).
The GenodeOS folks are also working towards building a usable "general purpose" desktop OS based on a microkernel, see e.g. chronologically:
- https://github.com/genodelabs/genode/issues/1552
It's entirely possible Google don't know either, they're just trying some things out and doing it in the open for whatever reason, and don't want to publicly commit to anything.
It certainly gets them some interested coverage from time to time.
* They may find it easier to work with hardware vendors when they all aren't subject to the GPL
* Oracle
* The non-system calls overhead in Linux that may not be suited for mobile phones
* Wanting to better couple the OS with the hardware, and not have to run in a VM on top of the Kernel
* Oracle
* Changing business philosophies as they start building out their own hardware
* Oracle
* Wanting stricter control of the OS application stack
* Protecting proprietary hardware components without using blob drivers
* Did I mention Oracle?
[0] https://fuchsia.googlesource.com/docs/+/master/the-book/#Zir...
I'd say it's more like using the per process FD table for everything, rather than having global tables like for PIDs. Which is really cool, IMO. Containerization is all about adding indirection to the global tables, but of there are no global tables, you get all of that for free.
They should have used seL4.
This may seem trivial, but closed device drivers make 100% impossible neither to update them to more modern versions once the Android version is declared obsolete, nor install natively a different operating system on the device. This practice, security concerns aside, is responsible for a huge load of old -otherwise perfectly usable- devices being scrapped in landfills.
So, dear Google, will you keep the lowest, smallest but most important layers of the OS open or rather will prevent people to do what they want with the devices they purchased even at the cost of contributing to more pollution?
From my reading so far, it looks like Fuchsia takes some of the better parts of the POSIX model, the way file descriptors can be uses as capabilities, and extends its usage more consistently over the API so that it is used in a lot more places. In Fuchsia they are handles, which are arbitrary 32 bit integers, but they act a lot like somewhat richer, more consistent file descriptors. You can clone them, possibly with limited rights like read only, you can send them over IPC channels, etc.
There are some differences, in that there's no absolute path handling directly in the kernel; instead, you always open relative to some particular file handle. A process may be given two that can be used to emulate POSIX style path resolution, by being given a root directory handle and a current working directory handle, though there may not be a guarantee that one contains the other; it sounds like more commonly application will just be given handles for the files or directories they are supposed to access, rather than having everything go through path resolution.
Signal handling is done consistently with waiting for data on handles; handles just have various states they can be in, like ready for reading, ready for writing (for file handles), running or stopped (for process handles), etc, and you can wait for changes of state on any of a variety of different handles.
Memory mapping can be done by allocating a virtual memory object, which you could either not map (treat it as an anonymous temporary file), write to, and then pass to another process, or you could map it into your process, manipulate it, clone the handle, and pass that to another process. Basically seems like a cleaner design for shared memory handling than POSIX, though something a lot like it can be done in Linux these days with anonymous shared memory and sealing.
Jobs, processes, and threads are also all handles. Jobs contain processes and other jobs, and processes contain threads. Jobs group together resource limitations (things like limits on numbers of handles, limits on total memory used, bandwidth limits, etc), processes are separate address spaces, and threads are separate threads of execution in one address space. The fact that jobs and processes are all handles, instead of IDs, means that you don't have to worry about all of the weird race conditions of trying to track things by PID when that PID may no longer exist and could be reused in the future.
An interesting part is how program loading happens. In POSIX like OSes, you fork your process, which creates a clone of the process, and then exec, which asks the kernel to replace the running program with one loaded from another file. You give the kernel the path to a file, and the kernel calls the dynamic linker on that path to link the shared libraries together and then execute the result. In Fuchsia, you just build the new address space in the parent process, and then ask the kernel to start a new process in that address space, with execution starting at a particular point in it and some parameters loaded into particular registers. This basically means that the dynamic linker will now be done by a library call in the parent process; which could be really advantageous for those processes that fork the same executable as a subprocess many times, as they can link the executable once into some read only pages, and then very quickly spawn multiple processes from that same already linked program. I'm sure that ld.so and friends on Linux and other POSIX-like OSs have a lot of caching optimizations to make this faster, but it sounds to me that the Fuchsia model of just having the parent process do the linking as a library call could be a lot faster.
(edit to add: hmm, upon further reading, it looks like they expect process creation to happen from a single central system process, rather than providing the dynamic linker API, "launchpad", as a supported API; but for now it looks like you can use the launchpad library)
It basically looks a lot like what you would wish the POSIX API worked like with a lot of hindsight. A lot simpler and more consistent, and does a much better job of "everything is a file" than the POSIX API ever did (of course, it's "everything is a handle," but that's fine, the point is that there's one consistent way to work with everything).
What is your sense of the latency guarantees/scheduling to user space graphics and input? This is an area that everything else kind of fails at. "No drawing the groundplane and every possible frame for this user you have in your VR grasp is not optional".
Is the security actually in use or just someday?
edit: security looks baked in but tbd
It looks like the isolation of different applications, and capability based security, is pretty baked in. There do seem to be some TBD parts, like right now just like on Android apps can either have access to all of /data or none of it, and fixing that is something they list that they want to do but haven't yet.
I am failing to see how this is more consistent. With UNIX, because everything is like a file, you operate on them the same manner. A file, a socket, a pipe, shared memory, ... you open them then you use the system calls for operating on files: read(), write(), poll(), dup(),... which then allow you to use operations built on these syscalls such as fprintf, fscanf,... but also all the tools like cat, head, grep,... This is what i would call consistency.
If i implement a new feature as a file in linux, for example a virtual filesystem like /proc/, all the cited operations would already be available out of the box.
In a sense, we only treat everything as a file the same way some languages have a toString method for everything. You can get something out of it no matter what it is, but there's no guarantee that something is going to be in any way useful and you still have to interact with it in a way that doesn't treat it like a generic string.
- Non mmap'd memory: what do you do with memory retrieved by [s]brk(2)?
- Signals: are they files or not? Signalfd is provided in addition to lots of other complicated other facilities for handling around the same things. And that's before getting into realtime signals and the like.
- Timers/events: are they files? vDSOs? Available via files? No? Depends on which syscalls/APIs you're using.
Additionally, many of the non-file-ish APIs in POSIX implementations are a massive hassle to use across multiple threads. Even the file-based APIs for eventing (select/poll/epoll.) have substantially different behavior with regards to edge/level triggering, and different behavior when used across multiple processes (shared fia fork or non-CLOEXEC handles) or threads. Can you master them and use them correctly? Sure. But there are so many ways to achieve very similar things, and, while each method has its niche, there's no unifying thought model that ties them together in the same way that "everything is a file" was promised to tie together UNIX operating systems.
Oh, and /proc is being moved away from/found to have limitations because it's a file descriptor exhaustion hot-spot, among other things. So the plan9-style of "expose the internals as a filesystem" appears not to be the route that the Linux community is pursuing.
TL;DR if you're writing simple, non-concurrent standalone utilities or working at a very high level then sure, you can pretend everything is a file. Below that, or in more complex applications, those abstractions break down in surmountable-but-annoying ways.
Even on UNIX like systems, you can't read or write on every file; for instance, you can open directory, but you can only readdir on that, not read from it. But they are still file descriptors like everything else, so you can call dup(), fstat(), pass them between processes on Unix sockets, etc.
There are plenty of other operations which can only be done on certain types of files in UNIX-like systems; for instance, you can only recv() or recvmsg() on a socket.
The difference is that in Fuchsia, more things have handles, and so more things can be treated consistently. For instance, jobs, processes, and threads all have such handles; so instead of getting a signal that you have to handle in an extremely restrictive environment in a signal handler or having to call wait4() to learn about the status of a child process, you can just wait on signals to be asserted on the child process using zx_object_wait(), which is the equivalent of select() or poll(). This means no more jumping through hoops to get signal handling to work with an event loop; it just works.
Of course, the other difference in Fuchsia is that there is not a single namespace. Every component in Fuchsia has its own namespace, with just the things it needs access to; there is no "root" namespace. This is good for isolation, both for security reasons and reducing accidental dependencies, though I do wonder how much of a pain it would make debugging and administering a system.
vmo_read - read from a vmo
vmo_write - write to a vmo
fifo_read - read data from a fifo
fifo_write - write data to a fifo
socket_read - read data from a socket
socket_write - write data to a socket
channel_read - receive a message from a channe
channel_write - write a message to a channel
log_write - write log entry to log
log_read - read log entries from log
Treating everything like an undifferentiated sequence of bytes can cause impedence mismatches; each of these types of handles has very different ways that you work with it. For instance, a VMO is just a region in memory. A FIFO is a very small queue for short equally sized messages between processes. A socket is an undifferentiated stream of bytes. A channel is a datagram oriented channel with the ability to pass handles. The log is for kernel and low level device driver logging.
In fact, it looks like the Zircon kernel has no actual knowledge of filesystem files or directories; they are actually channels that talk to the filesystem driver (another userspace process) over a particular protocol.
The thing about having one single universal interface like read() and write() to a lot of fairly different things is that they each actually support different operations; you can't actually cat or echo to a socket (not without piping into nc, which does that for you). Or you can't just echo data into most device files and expect it to work; some of them you can, like block devices, but others you need to manipulate with ioctls to configure properly.
What Fuchsia is doing here is acknowledging the different nature of the different types of IPC mechanisms, and so giving them each APIs that better matches what they represent. A VMO can be randomly read and written to; none of the others can. A FIFO can only accept messages in an integral number of equal size pieces that are smaller than the FIFO size, which is limited at a maximum of 4096 bytes; it is used for very small signals to be used in conjunction with other mechansims like VMOs. A socket provides the traditional stream abstraction, like a pipe or SOCK_STREAM on UNIX, in which you can read or write new data but can't seek at all. A channel provides datagram based messages along with passing handles.
One of the big things that I think the Unix model makes hard is telling when something is going to block; because read and write assume that the file is one big undifferentiated blob of bytes, it can be hard to tell when it's safe to do so without blocking. On the other hand, each of these is able to have particular guarantees about what you can do when they report that there is space available.
I admit that the log ones seem redundant; I would think they would make more sense as just a particular protocol over channels. I don't see any reason for that one to exist separately.
I wonder why you would think it would be better to have one interface that isn't an exact match for a lot of different IPC types, than separate specific interfaces that match them? They are all tied together by being handles, so you can dup them, send them to other processes, and select on them just the same, but the read and write operations behave quite differently on each so having an API that reflects that seems reasonable.
If you like to think in object oriented terms, think of them as subclasses of handle. If you like to think in terms of traits or interfaces, think of there being one generic handle interface, plus specific operations for each type of handle.
The "every thing is a file, and a file is an undifferentiated bag of bytes" is in some ways a strength of UNIX, but in other ways a weakness. You then have to build protocols and formats on top of that, kernel buffer boundaries don't necessarily match up with the framing of the protocol on top, and so on.
And all it takes to give you the power to manipulate things in the shell is appropriate adapter tools. Just like nc on UNIX allows you to pipe in to something that will send the data out on a socket, you need some adapter programs that can translate from one of these to another (and from filesystem files, since those don't even exist at this abstraction level); of course, in many cases, you're probably going to need some serialization format for things like channel datagram boundaries, and there are some things that just can't be translated from a plain text bag of bytes (like handles).
Multiple signallable states per handle, rather than a single bit's worth of "signalled", is slightly novel. It's a fairly obvious generalization of WaitForMultipleObjects once one realizes that there are multiple ways in which one can wait on a handle. It's one that I implemented in a hobby operating system about 10 years ago, and I certainly didn't consider it groundbreaking.
That program loading mechanism isn't novel, contrastingly. Again, I did much the same for my hobby operating system. It's almost an inevitable design given the a desire to support an API with "spawn" (as opposed to "fork") semantics. And it has been in Windows NT all of these years, which from the start had to provide underlying mechanisms to support both models as required by its POSIX, OS/2, and Win32 subsystems. One can create a process object as a blank canvas and then something that has the handle can populate it with what are to be its program images; or one can create a process object that is "copy constructed" (as it were) complete with program images from an existing process. Your consequent forking-of-a-spawned-template idea for worker processes is interesting, but consider that an operating system capable of doing that has existed for quarter of a century now, and people haven't really made use of it in the real world. Not even the Cygnus people. (-:
More interesting from the operating systems design perspective are things that you've overlooked. One of the things that also happened in the 1980s was a reinvention/replacement of the concept of a POSIX terminal. OS/2 got some VIO, MOU, and KBD subsystems, and the applications-software level concepts of directly-addressable video buffers and queues of mouse/keyboard input events that encompassed all of the keys on a keyboard including function/editing keys. Windows NT took that further with its "console" model, unifying mouse, keyboard, and other input events into a single structure and unifying input and output (albeit with some kludges under the covers) into the waitable handles model. GNU Hurd contrastingly retains the POSIX terminal model, albeit that it is all implemented outwith the kernel, without even a pseudo-terminal mechanism or a line discipline within the kernel, and the console dæmons do have cell arrays that could in principle be accessed by applications softwares.
* http://jdebp.eu./FGA/tui-console-and-terminal-paradigms.html
* http://jdebp.eu./FGA/hurd-daemons.html
* http://jdebp.eu./Softwares/nosh/user-vt-screenshots.html
It's worth considering what design choices Google et al. have made in this area.
Then there are other lessons to learn from Windows NT. WaitForSingle/MultipleObjects having more than 1 bit's worth of "signalled" is one improvement that hindsight yields, as I have mentioned. Another is the lesson of Get/SetStdHandle. The Win32 API only supported three handles. And so language implementations that wanted to provide POSIX semantics in their runtime libraries had to implement the same sort of bodges with "invisible" environment variables that they did to make it appear as though there was more than a single current directory. They implemented their own extensible Get/SetStdHandle mechanism in effect, which only worked for coöperating runtime libraries, when it would have been far better for this to be provided by Win32.
* http://jdebp.eu./FGA/redirecting-standard-io.html#SystemAPIW...
* https://github.com/open-watcom/open-watcom-v2/blob/e5a5cab04...
* https://unix.stackexchange.com/a/251215/5132
* https://unix.stackexchange.com/a/413225/5132
Again, it's worth looking to see whether Google et al. have learned from this and provided a common language-neutral descriptor-to-handle mapping mechanism, and a means for that table to be inherited by child processes.
https://fuchsia.googlesource.com/topaz/+/master
There is no documentation at all but there is a few application examples in /app/. The bindings for fuchsia and zircon (kernel) are in /public/dart-pkg/
The author (Raph Levine) has a very interesting series of posts on data structures and algorithms used in the editor (like rope data structures)
The problem with most languages, including the ubiquitous C, C++, Java et al, is that there are implementation defined behaviours and undefined behaviours that are specifically placed in these languages.
A previous discussion, which I can't locate at the moment, did discuss this in detail. Most programmers have a serious flaw in that they do not document. They may produce documents but they do not document. Every assumption, every trick and why it is used, every implementation defined behaviour, every reasoning as to the use of specific algorithms should be documented and is not.
I have seen incredibly detailed documents for programs that just miss some of the basic essential assumptions because "everyone knows them".
In everyday communications, we use language in a dynamic way, meanings can be changed subtly and we get around the errors. With the programming of machines, there is no such leeway ever. Our languages should be defined completely so that we will know that what we have written has actual meaning.
the reality, of course, is that this is a "pipe-dream" and won't happen. But as programmers, we could start calling for such completeness of definition of the languages we use.
Important context is the Google C++ style guide: https://google.github.io/styleguide/cppguide.html
Just because you don't consciously interact with them on a daily basis, does not mean they do not exist. My guess is that QNX and kernels like it are the reason you can take for granted such obvious things as your car braking correctly, your train not derailing, and your robot surgeon not crashing.
In today's world, we're so used to software breaking that if it doesn't break, we oftentimes think it must not exist. But, there is a whole world of reliable software out there that can actually be trusted. You don't hear about it often, because they work so well.
Even the parts written in straight C and C++ code have issues in performance woes on Android, as everyone that has wanted to do real time audio on Android painfully knows.
The whole architecture has been a mess.
Did they fired you?
If you had any Android developer experience, you would surely know that Google had a few failed attempts at real time audio, needed help from Samsung to implement them, and the final API was C only, with devs asking for a C++ one, wich was later dumped on github as side project and isn't part of the official NDK APIs, but alas you don't.
Would you mind to explain what happened completely? I am very curious about it.
Thank you so much ;)
Originally Android only had the Java media APIs, with a quite complex state.
https://developer.android.com/reference/android/media/MediaP...
Android 2.3 introduced OpenSL ES into the NDK and Android 4.0 got OpenMAX.
All of them weren't up to the game of realtime audio due to the Android architecture.
http://superpowered.com/androidaudiopathlatency
https://nsr.cse.buffalo.edu/wp-content/uploads/2016/10/rtdro...
https://www.androidauthority.com/android-6-0-marshmallow-aud...
There are plenty of other articles online when you search for audio issues on Android.
There was even a Google IO 2013 talk about it.
https://www.youtube.com/watch?v=d3kfEeMZ65c
Meanwhile Samsung had customized their Android versions to properly support real time audio and offered an SDK for their handsets.
http://developer.samsung.com/galaxy/professional-audio
At Google IO 2016 the problem was again discussed, with the Samsung team from Professional Audio being called on stage to discuss their collaboration.
https://www.youtube.com/watch?v=F2ZDp-eNrh4
Finally last year at Google IO 2017, the new real time audio was announced, as C only lib.
https://www.youtube.com/watch?v=C0BPXZIvG-Q
https://developer.android.com/ndk/guides/audio/index.html
The announced C++ wrapper ended up being an external project on github, detached from the NDK, that you need to integrate yourself, without any guarantees how long Google will care to maintain it.
Oh, to make things even better, it is already clear from Android P draft documentation that new audio APIs are on their way.
I'm just trying to correct all of the misinformation you like to post about Google and Android.
>If you had any Android developer experience, you would surely know that Google had a few failed attempts at real time audio, needed help from Samsung to implement them.
Unfortunately, your lack of Android development experience and your lack of exposure to development on Samsung devices has caused you to be disingenuous once again. Samsung didn't help Google nor did they contribute any of their code to AOSP. They implemented their own proprietary audio solution called SAPA. Unfortunately, it was limited to their platform and the audio latency wasn't very good in comparison to the iPhone.
>and the final API was C only with devs asking for a C++ one, wich was later dumped on github as side project and isn't part of the official NDK APIs, but alas you don't.
AAudio is indeed coded in C, but at least you can use the Oboe C++ wrapper. What were the low latency audio solutions for Windows phone again? Oh that's right, there weren't any. No wonder there were no low latency audio apps on that platform.
It's just that despite all the good arguments for 30+ years, microkernels somehow seem to have failed to reach their full potential. That's why it's going to be interesting to see how Fuchsia pans out, being written from the scratch with all the cumulated knowledge and experience. Not to mention Google's resources and talent pool.
Ultimately, kernel popularity is largely going to be a network effect. Linux is popular on servers because it is both free and popular; not really for any inherent technical merit. Windows is popular because no one loses their job for choosing Microsoft.
On the other hand, there are several microkernel operating systems with notable features and significant, dedicated fan bases. For example, AmigaOS is well-known for its responsiveness, and despite not being in production for decades, still has a dedicated fan base. QNX is used in a lot of critical, performance-oriented workflows. OS X is a partial microkernel as well.
Nevertheless, the only microkernel that has really failed is GNU/Hurd. Minix fulfilled what it set out to be (educational) and Symbian was successful enough on mobile.
If I remember right, Linus's main argument against Tanenbaum was that the overall state gets so dispersed between the various services that make up a full-fledged OS, that eventually a microkernel-based system just gets unpredictable or starts performing poorly. I think the discussion was inconclusive, although for me Linus's argument sounded intuitively convincing.
Ultimately, Linux also is not all that popular except in two niches: servers and cell phones.
Windows is also not popular except in a niche: desktop computing.
Ultimately, you have arbitrarily declared several very prevalent forms of computing to be 'niche', while declaring several equally prevalent forms to be 'popular'. One of my hypotheses above is that we tend to dismiss reliable forms of computing as 'not really computing', because we expect computers to fail. When computers work, we think of them as mechanical machines or devices (the way we might view eyeglasses for example). I feel like your subjective opinion of what is and isn't niche just further demonstrates this point.
My guess is that there are more instances of QNX (and systems like it) than we realize. There could easily be as many as Windows or OS X (almost certainly the latter, I feel).
You are totally right that microkernels have been very successful in many different areas. I am afraid to even mention, that to me it seems they are most often pretty specialized areas with targeted applications and hardware choices. Which is why I'll welcome Fuchsia, especially if it is meant to be a general purpose, open source OS for a wide area of applications running on commodity consumer-grade hardware. That's all.
Well, large parts of the Linux world ended up with systemd, and I haven't yet met a person who had NOT had his fair share of issues with it.
They're generally used for different purposes, but if you mean number of deployed systems, then microkernels have won hands down. Firmware in nearly every device runs a microkernel like L4. Hypervisors like VMWare and Xen are also microkernels.
Microkernels are everywhere, it's only the desktop that's still dominated by monoltihic kernels (Mac OS X's Xnu/Mach is not a microkernel).
VMWare calls their system a microkernel (and so Wiki's rules therefore repeat that without other research), but the stack trace on the ESX wiki page pretty clearly shows a network card driver being called inside kernel context, so they have to be playing fast and loose with the term. From the outside it looks like earlier Vxworks; it's somehow a microkernel despite all of the code living in the same address space with no real permissions differences because it has multiple kernel threads and loadable modules. By that definition Linux is a microkernel too.
Xen has far too much in-kernel code to be considered an exokernel. Linux on L4 had even less overhead than paravirtualized Xen. If exokernels truly efficiently multiplex the hardware in the most minimal manner possible, this wouldn't be possible.
I can't comment on VMware beyond published documents since I'm not as familiar with it.
And Linux on which L4?
Far as NOVA, here's the dissertation that goes into a lot more detail on design considerations than most of the whitepapers.
https://www.researchgate.net/publication/275031217_Improving...
Of course, the number of hardware and firmware type of attacks on mainstream platforms made NSA retire the SKPP for doing separation on them. Even a perfect hypervisor cant be trusted to maintain that when its dependencies are garbage. That was even noted in 1992-1993 papers on VAX Secure VMM. Even secure digital desigms might have analog or RF attacks.
So, the current recommendation is to build things that way just to reduce number of attacks with monitoring and recovery as usual. Those two, though, could run on simpler, verified platforms. There's a lot of precedent for such split architectures.
That is not enough emperical data?
The BeOS demo toward the end is similar where they fire up a load of 3D apps, videos, etc with the system gradually slowing but still handling the load. That was on mid-90's hardware.
EROS was a capability-secure microkernel with persistence for saving or restoring running state of system. One thing they liked doing at demos was unplugging it during file transfers. After it restarted, the system would pick up where it left off.
In security side, there's been a few security and separation kernels to never have a reported breach in the field. They passed 2-5 years of pentesting by evaluators, too, doing many times better than monolithic kernels in defects found. Also easier to mitigate covert channels or do formal verification since they're small enough to analyze to begin with.
https://arstechnica.com/information-technology/2008/02/first...
https://news.ycombinator.com/item?id=10957020
It also had the kind of compile-time slowdowns one expects with a lot of context switches on older CPU's. So, what's your source that there's not a microkernel at the center?
Did it have nothing of the sort? A microkernel-like component in center of monolith like NT? Microkernel architecture with key stuff in kernel mode for performance like hybrids do? Did you see anything fitting the term in any BeOS release? And how would you classify its architecture?
Haiku's kernel is also monolithic, although we have a few hybrid tendencies (FUSE, but it's not widely used) and even more modularity than BeOS had, but we are still mostly source-compatible with the BeOS kernel.
I don't know why people say it's a microkernel; people say the same of Haiku, but it's just not the case. Perhaps it's because the dynamic kernel module system is built-in and virtually all kernel modules are stored as shared objects and loaded on startup, vs. Linux's more static approach, at least historically? That's not at all what's meant by the term "monolithic", but popular perception is often wrong...
Linux is in places that have higher mindshare than the places that microkernels occupy. When was the last time you thought “I wonder how the hypervisor powering AWS is designed” or “I wonder how my cellphone’s baseband is designed”. The latter being a question that I wish people would ask.
What is this for? Is there a precedent?
You can see part of it here: https://github.com/torvalds/linux/blob/master/arch/x86/inclu...
Continuing to see this parroted is about as silly as the "Android OS includes ads" which is another comment that lets me know the author hasn't actually used the platform for themselves.
* https://news.ycombinator.com/item?id=15634014
* https://news.ycombinator.com/item?id=15641592
Currently looking to see if this would be suitable for our high performance networking needs, haven't seen anyone else actually using it though.
Could anybody please explain me why microkernels are so great, when practically they do nothing more but push the overhead of switching threads to extreme? Basically, everything that program does requires waiting for scheduler to execute whatever service we send messages to. Disk, sockets, devices - everything. All of which is made in the name of memory safety.
On the other hand, unikernels that execute nothing but managed code (e.g. not code of CPU, but code for some virtual machine such JVM or .Net, which is forbidden to read other processes' memory on the syntax level) solve the same problem of protecting system memory, while carrying much less overhead. I guess this approach would be more preferable for creating a new mobile-oriented OS that requires good performance and low power consumption, no?
Any "bloat" or slowness on Android seems more likely to be Java, or something other than the base OS.
Maybe I'm missing something?
.. but where do you find any reference to him in that video?
This is due to the development practices and tools employed, not intrinsic to the construction of new operating systems. There are much better tools now. For instance, Google could have built this on seL4, a verified microkernel instead building their own from scratch and they would have hit the ground running instead of the slower build up they're now going to face.
For what benefit exactly?
That would seem like a massive slap in the face to the cause of freedom, if so.
The other huge Google OS (Android) doesn't benefit from POSIX either at all - the POSIX interface isn't even exposed to the user applications.
ANSI C and POSIX do overlap, but aren't the same thing.
Nevertheless, vast majority of applications will never include NDK code and even if they will, they probably won't really talk to POSIX calls directly either. For the type of OS Android is, it doesn't really gain anything by being POSIX compliant far away from developer APIs. And Fuchsia, if anything, is trying to be an Android type OS.
Not being POSIX doesn't mean it's going to be entirely foreign or that it will have no compatibility with software that is already written for POSIX-like platforms. It just means that the basic process management, IPC mechanisms, permissions handling, and so on uses a model which is akin to a cleaned-up subset of POSIX; everything is done via handles, which are a lot like file descriptors but work in a somewhat more uniform way, there is cleaned up management of resource allocations to jobs, memory mapping of processes, and thread management, and so on.
It's not terribly hard to build a POSIX-like layer on top of this; said layer isn't necessarily going to support some of the real warts of POSIX, like the really broken way signals work in POSIX, so some software that intimately depends on this may have to be factored out to support the way that Fuscia handles signals, but for most software this will be a big improvement. Software on POSIX systems nowadays has to jump through hoops to make signals play well with event loops, frequently allocating a pipe that gets written to in a signal handler, so the event loop can pick up that notification later, while in Fuscia that's how signals already work, it's just a state change on a handle that can be waited for in Fuscia's equivalent of select/poll. So in cases like this, Fuscia will add a new code path that is simpler and more maintainable than the one on POSIX-like systems.
How small this POSIX interface can be depends on how much of POSIX legacy you want to reimplement.
It has some convenience functions for decoding files given a path or FD, but I'm sure Fuscia's limited POSIX compatibility layer will support that, basic file access is relatively easy to provide in a POSIX library wrapping Fuscia's file handling.
Likewise, I'd be willing to bet that curl and Git would mostly work on top of the limited POSIX compatibility layer; they might need a few tweaks, but likely not much more than the tweaks needed in porting to the various BSDs and OS X, and likely a lot less than is needed to provide them natively on Windows.
$ git diff --stat origin/upstream/master origin/master
BUILD.gn | 438 ++
include/curl/curlbuild.h.fuchsia | 198 +
lib/curl_config.h.fuchsia | 1034 +++++
src/.gitignore | 1 -
src/tool_hugehelp.c | 9000 ++++++++++++++++++++++++++++++++++++++
5 files changed, 10670 insertions(+), 1 deletion(-)
So it looks like they have had to make zero actual source changes to cURL; the POSIX compatibility layer and setting the appropriate defines in cURL's config files are sufficient.
Many Android apps drop down to the NDK, where POSIX does matter.
> Linux isn't fully posix anyway
It's close enough that the difference really is just an issue of not getting certification.
Everything else on the NDK has nothing to do with POSIX.
Newer is rarely better. Besides, in computing, so many "new" things are just rehashes of old (and not so old) ideas.
I really wish we could get away from the "that software is old" meme in this industry.
New software, otoh, hasn't been through a 40-year shakedown cruise.
Neither of these things has any bearing on the quality of Linux, or lack thereof.
Also their goal is not to run 100% of POSIX or Linux specific software, rather achieve a good enough compatibility to run majority of well known projects and utilities.
A lot of security-interested programmers think it easier to secure a small microkernel like Fuchsia than to secure the older generation of operating systems and the baggage they have acquired.
Google want everyone to trust the Internet. If consumers are scared to shop online, Google dies. This is why they put so much effort into securing it.
Wouldn't surprise me if the unofficial reason is because it's more fun.
Not gonna use an OS from that company.
Not to mention that the fat profits capitalism bestows on Google FUNDS fuchsia
> Capitalism is an ethical, meritorious system rewarding hard-work
Did you drop an /s or something?
Captialism doesn't give a shit about eithics or merit either way. The only thing worth a damn is capital, which is a pretty good motivator for all kinds of unethical and corrupt practices.
Not that GPL would necessarily be a good thing in this case.
That's the point (or at least one of them). Though I personally don't care if it is GPL or not, as someone interested in perhaps using this OS for commercial purposes at some point it's not being GPL is a slight plus for me.
However, one key point of the GPL is to create a commons (of software, hardware, protocols, etc.) that can't be exploited for gain by capitalists, that can't be exploited for economic rent, that can't be laden down with copyrights and patents. A system that is actually, truly free (as in freedom). Which is important to understand if you want to be intellectually honest.
As a point of fact, it doesn't. Stallman himself sold GNU Emacs in the early days, and it was GPL'd from the start.
Capitalism is not "the economic system in which things are bought and sold with money", it's a much more particular subset of all those types of economies (namely, capitalism is the type where the primary resources and means of production are privately owned).
It's incidentally TRUE that GPL is not anti-capitalist. But it's also true that you can consistently both sell things and be anti-capitalist. Selling things happens in most economic systems, capitalist or not.
Well, at least according to Marx (c.f. Capital) capitalism is the system where things are bought and sold with money. If you read first few chapters of Capital you'll see that Marx explains this in various ways such as characterizing capitalism with division of labour where instead of producing bunch of commodities, workers produce one commodity and sell it for money with which they can buy other commodities. And according to, again, his definition communism is the society after this type of commodity production, i.e. the mechanism that produces value (money) is stopped in the sense that people stopped exchanging things for money.
You may not care of Marx's definition, but I just wanted to note for completeness.
We can describe the idea of buying and selling with money as certainly being a characteristic of Capitalism without asserting that it's a defining characteristic that is absent in other systems.
To be blunt, buying and selling with money is FAR older than Capitalism.
https://en.wikipedia.org/wiki/Capitalism is actually pretty good and neutral
Capital starts by explaining commodities. This is because: (1) Marx tries to explain some bit of the terminology of his period's economic terminology so he needs to do some ground work; (2) commodity production is an important aspect of capitalism that he refers all throughout his works. My main point is that the force that made capitalism possible and the force that sustains capitalism is one, which is the accumulation of value. As Marx explains in later chapters, a things will have different types of values. For Marx, nothing has any intrinsic value and its money-value is determined at the moment of trade. That is the force that generates value inside economy is the act of selling commodities. The same force causes the distinction between bourgeousie and prolateriat (c.f. Marx's definitions of social classes) and the same force caused the transformation from earlier economic system to capitalism (which answers your complaint). Now this brings us to the end of capitalism, which Marx very insistantly argues that end of capitalism is the seizure of value generation which is equivalent to saying society being moneyless. E.g. one misconception people have is that Marx was also against labor-vouchers, but this is not true, as explained in Critique of Gotha's Programme, since labor-vouchers do not generate/accumulate value, their value is not determined at the moment of trade. Anyway, this also relates to Marxist criticism of anarchism. For anarchism capitalism --> communism is the seizure of capitalist state. But Marxism thinks this is fundamentally wrong because capitalist state is generated by capitalist mode of production. So, you will want to eliminate the capitalist mode of production instead of the state itself, because as long as c.m.p exists there is no way to kill capitalism, so state will revive. For Marxism you first need to eliminate the economic system that makes capitalism possible, i.e. accumulation of value, and then ultimately kill the State and class society as they're caused by capitalism.
This belongs on some a list of "naive things Americans believe"
Nothing forces anyone from using someone else's GPL software. You aren't prevented from using GPL software either. In fact, it has a price, and that price is you contributing changes and directly interfaced software back into GPL. The price isn't money.
Beyond this, open-source/floss is meant to create a commons in terms of libraries and software that aren't commercially encumbered. Way too many things (particularly drivers) are locked away and stop working.
Please also check Zircon's kernel license [2]. The PATENTS thing doesn't look though.
Or did you meant that it doesn't have a GNU license with a clause that forces others to distribute the source?
Probably it doesn't matter that much to them as by being the developers of the software they can make changes in their software and just not share it.
Anyway, I'm not happy with more Googlification and them having the "expertise monopoly" in yet another piece of tech.
Things like ChromeOS and Chromecast shows that they're not willing to create an open OS.
[1] https://en.wikipedia.org/wiki/Google_Fuchsia [2] https://fuchsia.googlesource.com/zircon/+/master/LICENSE
If Fuchsia shipped on phones in binary form, consumers receiving those phones would have no legal basis for requesting the source code of precisely what they received.
GPL-compatibility only speaks to the mixing of code having one license with GPL code.
Of course a non GPL license would put us in a worse position but the current situations also has limitations.
I wonder if GNUv3 could solve the blobs drivers issue.
It's pretty much the norm today for everyone.
Which doesn't justify the universal, present-tense claim upthread.
How is this not the latest iteration of not invented here syndrome? Any system like Linux or Python that has the "Benevolent Dictator For Life" holding the reins is inherently saying that they favor quality over quantity. Its almost like the US Senate, in that the very goal is to go only as fast as prudent.
As I see it, is all about driver support; just because is the bigger effort. That is why vendors (and the community) focus in only one or two options (Windows/Linux).
Anybody can come up with new fancy OSs, as a matter of fact many people does. Problem is, there is no incentive for vendors to produce specific drivers for those, and the communities are just to small to cope with the huge amount of hardware support to make them useful.
I just don't see the point of coming up with new OSs as long as Windows/Linux just work as intended.
I do like the minimization that a lot of OS/Systems are undergoing though. I still remember when VMWare VM's came along and my mind was blown. Similar feeling on seeing Docker, but it was tempered somewhat until kubernetes came out. Very excited to see what comes next in the future.