The Jury Is In: Monolithic OS Design Is Flawed [pdf]
ts.data61.csiro.au
ts.data61.csiro.au
If I'm sure of one thing, it's that as soon as we decided to build everything as Microkernels, we'd have the same squeaky wheels touting the massive benefits of Monotlithic OS design. We're hilariously cyclical in our preferences.
"Think of all the runtime efficiencies of the shared memory, and how much easier it would be to develop on the shared codebase!"
When we choose a direction, we see all the difficulties that path provides and kind of forget about all of the things it gives us.
And when looking at the other option, we see all the things that would overcome our difficulties while assuming that we get to keep everything good from the current path.
Everything is a trade off.
Also, your phone's baseband processor almost certainly runs a microkernel, and likely so does your car.
It's quite crazy to count all the layers
cpu microcode
cpu isa
hypervisor
os kernel
userspace api
browser runtime
js vm
application
your mouse
...
webassembly vm
(insert variable height custom stack)
application
...
https://source.android.com/devices/architecture/kernel/modul...
https://source.android.com/devices/architecture/hidl/
So everyone running Android Oreo or newer on their phones, not only has a microkernel on their basebase radio, they also have a Linux tamed into a microkernel on their main ARM SOC.
This means most (updated) Android 8 devices in the field are not Project Treble and are running old-style module-less kernels and don't have A/B system partitions.
HALs only seem to be there to abstract over the APIs of different hardware implementations and access to them. Not necessarily their drivers.
I would love to be wrong about this, so I would really appreciate evidence to the contrary here.
[1] https://source.android.com/devices/architecture/kernel/modul...
There are two HALs in Android.
The old HAL, previous to Treble, which was hardly used by OEMs.
And the new HAL, which is enforced by Treble.
On the new HAL, drivers are implemented as Android services using Android IPC via interfaces defined in HIDL, or by using the new shared memory APIs introduced in Oreo as well.
https://source.android.com/devices/architecture/hidl/service...
https://source.android.com/devices/architecture/hidl/binder-...
https://source.android.com/devices/architecture/hidl/memoryb...
https://source.android.com/devices/architecture/configstore/
I'm guessing that the Treble modules expose the traditional /dev and /sys interfaces like before, and these new HALs talk to devices through those, right? Is that not still a runtime-linked monolith, with fairly-thin userspace services between the kernel and the framework?
The bulk of driver code logic (e.g. interfacing with a touchscreen controller) is probably still running in the kernel - show me if I'm wrong. I would think this would be how you define a microkernel. One exception may be the GPU -- those drivers are often very thin in the kernel because of GPL, with a fat userspace library that they can legally keep closed-source.
As I understand it HALs and HIDL are used to provide a standardized way to implement new device features in a compatible way. So a vendor introduces a odor-sensor and can define an HIDL interface for the userspace to call the device driver provided in a kernel module.
I do not see a requirement to implement drivers in userspace, nor provisions for it, like interrupt handling, i2c/spi access or similar.
"Binderized HALs. HALs expressed in HAL interface definition language (HIDL). These HALs replace both conventional and legacy HALs used in earlier versions of Android. In a Binderized HAL, the Android framework and HALs communicate with each other using binder inter-process communication (IPC) calls. All devices launching with Android 8.0 or later must support binderized HALs only.
Passthrough HALs. A HIDL-wrapped conventional or legacy HAL. These HALs wrap existing HALs and can serve the HAL in binderized and same-process (passthrough) modes. Devices upgrading to Android 8.0 can use passthrough HALs. "
https://source.android.com/devices/architecture/hal-types
Here are the user space driver APIs for i2c/spi access on Android Things.
https://developer.android.com/reference/com/google/android/t...
Interprocess RPC is only for Oreo and newer.
Going forward, I expect the vendors to modify their kernel drivers to export the treble API over binder IPC directly while in kernel space.
So I wouldn't be surprised if it ends up that interprocess RPC only ebds up getting used in systems before Oreo.
It if was, there would be documentation on how to write a userspace device driver, but there isn't.
https://lwn.net/Articles/758745/
> Could allow for APK installable kernel drivers, allowing modules to be upgraded (even live)
https://twitter.com/MishaalRahman/status/1029064974805688320
> The Secure Enclave runs an Apple-customized version of the L4 microkernel. This microkernel is signed by Apple, verified as part of the iOS secure boot chain, and updated through a personalized software update process.
https://www.blackhat.com/docs/us-16/materials/us-16-Mandt-De...
> Microkernels are intended to create a minimal set of low-level operations that would be used to build an operating system. While it's popular to slap a monolithic kernel on top of your microkernel, this is not how microkernel based OSes are supposed to be; a real microkernel OS should have lots of separate pieces that used the microkernel services to work with each other. Using a microkernel as not much more than an overgrown MMU and task switching abstraction layer for someone's monolithic kernel is a cheap hack driven by the needs of academic research, not how they are supposed to be.
> By contrast, hypervisors virtualize and emulate hardware at various levels of abstraction. This involves providing some of the same things that microkernels do (eg memory isolation, scheduling), but people interact with hypervisors in very different ways than they interact with microkernels. Even with 'cooperative' hypervisors, where the guest OSes must be guest-aware and make explicit calls to the hypervisor, the guests are far more independent, self-contained, and isolated than they would be in a microkernel. With typical 'hardware emulating' hypervisors this is even more extremely so because much or all of the interaction with the hypervisor is indirect, done by manipulating emulated hardware and then having the hypervisor reverse engineer your manipulations. As a consequence, something like guest to guest communication delays are likely to be several orders of magnitude worse than IPC between processes in a microkernel.
People never seem to want to admit that sometimes, technology just dies, or at least becomes obscure, and so will invent bizarre "connections" between what we used to be working on and what we have now.
https://microkerneldude.wordpress.com/2008/04/03/microkernel...
NOVA is an open-source micro-hypervisor available in GenodeOS that similarly combines hypervisor functionality with a microkernel-like design:
The Xen hypervisor also got many of its design elements from the Nemesis OS, which had a lightweight kernel. There's plenty of overlap possible. A number of research and production systems are also both hypervisors and microkernel-like, too. So, it's more an existing concept than a bizarre, hypothetical connection. For OKL4, also deployed in over a billion phones they claim.
The hardware-like interface to the hypervisor is both inefficient and not very abstract. For instance, a guest kernel attempts to perform a series of manipulations of the page table, each of which traps to the hypervisor, or else it performs an equivalent upcall to manipulate the page tables.
The hardware emulation code ads a lot of potential bugs to the hypervisor. I hope our current hypervisors are an evolutionary transitional form and in the future we'll interact with hypervisors solely through upcalls.
QNX and many embedded OS, some of which driving high integrity software, are all microkernel based.
Including the one most likely handling the real time communication of this mobile radio.
When I was in college, the first assignment was to run a provided benchmark program that jumped all over a gradually growing buffer and graphed average latency vs. buffer size and we had to identify the sizes of thle various caches from the generated graphs. I was tripple-booting Linux Windows, and QNX at the time and did the same assignment on each OS (identical hardware). QNX had more sudden transitions between latency levels due to delaying transition later due to smaller cache footprint.
If your userspace NIC driver and TCP/IP stack are implementee as a library and you are running your high performance application on a dual NIC box, your application can be the driver for one of the NICs and the other NIC can handle everything else. It's hard to beat zero copy/zero context switch I/O. Of course, putting the application in the kernel would yet be faster, at least if in both cases the kernek's cache footpint is tiny.
Assuming you didn't have those mistakes, the difference was likely due to memory allocator choices. Scattering the pages of memory is very different from laying them all out one after another. Scattered pages will cause benchmark results to be less predictable, with evictions seeming to happen at random. QNX probably made one great big allocation, in both the virtual and physical address spaces.
I noticed a later filesystem simulation benchmark for the same class ran faster when I moved my mouse. After a few minutes of investigation, I submitted a patch to prefer /dev/urandom to /dev/random on hosts that had /dev/random.
And I'll throw out there that many times the the term microkernel in a lot of embedded OSs has been contorted by marketing speak into something unrecognizable. Basically if you have multiple threads in the kernel, structure the kernel code into modules (but perhaps don't even allow dynamic loading of modules), and can communicate through async queues, then it's called a microkernel. For instance VXWorks until recently didn't have memory protection between tasks, but still called itself a microkernel.
* https://blog.darknedgy.net/technology/2016/01/01/0/ (https://news.ycombinator.com/item?id=10824382)
But hey, it's lunch and why not.
1) Microkernels are defined by their small size
> In summary, the microkernel provides mechanisms corresponding to hardware features. It doesn’t provide services, just fundamental mechanisms. In particular, it does not duplicate OS services. This misunderstanding was one of the causes for the failure of first-generation microkernels. The OS community understands this.
I'd argue that exokernels fit this model much more effectively. I love XOK's kernel level support for what we'd now call DPDK with BPF (they had user space multiplexed packet queues with an in kernel vm doing filtering). And it's capability based file system cache was an amazing way to address something that no microkernel has tried to, and I've never seen anyone try to replicate anything like that yet. In fact exokernels became so good at multiplexing hardware that Xen came out of the exokernel research.
2) Microkernels are unperformant
He does what most microkernel fans do, which is regurgitate a bunch of papers from the early 90s about how if you use a 486 or early RISC (where trapping to kernel space is only as costly as a branch mispredict) then it's not that expensive. Well guess what, it's not 1992 anymore, trapping to kernel space is on the order of 1000 cycles these days instead of 5, and even outside of microkernels, that bridge has gotten so expensive that you see people not even using the kernel anymore, but instead running drivers inside the user process (see DPDK).
And yes there's a lot of hand waving about FUSE, but nobody claims that FUSE is performant solution just that the slow model that can't crash the kernel is useful in a lot fo cases.
The QNX stuff is a little disingenuous as it's essentially marketing documentation. Yes, if you push everything through a pipe on unix, you won't get the best speed. Let's compare QNX to the Unices performant solutions (ie. mmap and shared memory). Yes they made some microbenchmarks faster, but most of that is viewed as control plane rather than data plane stuff on Unix.
I'll extend a peace offering here and say that a lot of the microkernel is unperformant was a reflection of gen 1 and 2 ukernels like mach that had to do a permission check on every port access. More modern system (specifically thinking about the L4 variants here) have a capability based model that needs far fewer checks at runtime. However what I said about how traps into the kernel have gotten more expensive still hold true.
3) Microkernels are a diversion, because a userland server failure will be just as catastrophic as a kernel failure anyway
Monolithic kernels typically have the same layering internally that Minix calls out. It's about as easy to add layers to linux block device structures as it is on minix, including all of the checksumming, etc.
And neither linux nor minix protects you from logical bugs in filesystems screwing up anything and everything. We like to think of the kernel in a ukernel as being totally separate and pure from the FS and block device drivers, but it had to be loaded from somewhere...
IMO, the monolithic/microkernel dichotomy here is a false one. Neither really address the issue per se, we need to move to type safe machine checkable languages. A recent example of microkernels screwing this stuff up was the original exploit chain that opened the nintendo switch.
4) Microkernels turn well understood memory-protection problems into poorly understood communication problems
He just spends the whole time here handwaving away how difficult distributed systems are because the internet works a lot of the time. Huge red flag for me.
5) Microkernels are a bourgeois plot to undermine free software
I used to write off what he's arguing against here, but I'm really coming around to the idea. Google's Zircon in Fuschia seems specifically designed to remove GPLv2 requirements from systems like ChromeOS and Android. Seems like a net loss for software freedom.
6) Hah, those stupid fucks are running Linux on top of their microkernel! What happened to microkernels being so great, fags?
(Ignoring the slur for the purposes of this discussion) he has a decent argument here, but I'd like to see the argument compared to containers where spinning up new OS spaces is even cheaper than a whole VM for a personality. I think a blend of the techniques a la the NtPicoProcess stuff that makes WSL here is going to be the winner here more than current ukernel design where that code runs in a different address space.
7) If microkernels are so great, why is nobody using them?
This is where he hits that disingenuousness I bring up in my parent post.
TRON isn't a microkernel, hell it doesn't even require an MMU.
OKL4 loves bringing up how basebands they're running on, but how many codebases is that?
Same with MINIX.
Done for now, haver to get back to work
Yeah, no. A kernel has access to all of the data on the machine. A compromised userland is much more strictly limited.
Certainly if a compromised disk driver exposes a lot more data, not so much if you compromise your video driver. Compromising either in a monolithic kernel provides the same level of access. Strong isolation boundaries strictly limit risk.
> 6) Hah, those stupid fucks are running Linux on top of their microkernel! What happened to microkernels being so great, fags?
Driver support is always an issue. I don't see the problem.
> Certainly if a compromised disk driver exposes a lot more data, not so much if you compromise your video driver. Compromising either in a monolithic kernel provides the same level of access. Strong isolation boundaries strictly limit risk.
About the only part of the video drivers that runs in kernel space even on monolithic kernels these days are the drivers for the GPU's MMU. You screw that up and you're right back to where you started, corrupting random memory without regard for protection boundaries regardless of where that code lives. Everything else runs in user space, but not in an isolated process like on a ukernel, but directly in user process code, more like an exokernel.
> Driver support is always an issue. I don't see the problem.
My point underneath was comparing to other paravirtualized kernels was a best case comparison for ukernels, and zones/jails/containers has added a new more performant option for them that doesn't look as good for ukernels.
Strictly speaking, "hard realtime" means strictly bounded latency. Full determinism is overkill.
As was posted elsewhere, they seem to be fast enough for games on the Nintendo Switch: https://news.ycombinator.com/item?id=17768537
>><rant>
>>Why do the file systems have to be so tightly integrated in the "ring0" core? This is one subsystem that screams for standard callouts and "ring1" level.
>></rant off>
> Because only naive people think you can do it efficiently any other way.
> Face it, microkernels and message passing on that level died a long time ago, and that's a GOOD THING.
> Most of the serious processing happens outside the filesystem (ie the VFS layer keeps track of name caches, stat caches, content caches etc), and all of those data structures are totally filesystem-independent (in a well-designed system) and are used heavily by things like memory management. Think mmap - the content caches are exposed to user space etc. But that's not the only thing - the name cache is used extensively to allow people to see where their data comes from (think "pwd", but on steroids), and none of this is anything that the low-level filesystem should ever care about.
> At the same time, all those (ring0 - core) filesystem data structures HAVE TO BE MADE AVAILABLE to the low-level filesystem for any kind of efficient processing. If you think we're going to copy file contents around, you're just crazy. In other words, the filesystem has to be able to directly access the name cache, and the content caches. Which in turn means that it has to be ring0 (core) too.
> If you don't care about performance, you can add call-outs and copy-in and copy-out etc crap. I'm telling you that you would be crazy to do it, but judging from some of the people in academic OS research, you wouldn't be alone in your own delusional world of crap.
> Sorry to burst your bubble.
https://www.youtube.com/watch?v=PYZDl4RNEVE
Maybe they had some stuff in kernel mode in there. They still show you can start with a microkernel as the baseline then optimize from there retaining the architecture with its benefits in average case or most cases.
edit added
> Guys, there is a _reason_ why microkernels suck. This is an example of how things are _not_ "independent". The filesystems depend on the VM, and the VM depends on the filesystem. You can't just split them up as if they were two separate things (or rather: you _can_ split them up, but they still very much need to know about each other in very intimate ways).
That debate would be short and the answer would be "nope, we shouldn't because that would be stupid".
Could you elaborate on this one please?
For one example of such a system: A computerized way to communicate the availability of cargo and space to brokers all over the world, on a good Monday morning several million such messages are sent with a guaranteed maximum time between the first and the last such message sent (to ensure a fair market).
QnX is extremely pervasive and it - and other OS's like it - are so reliable that people tend to forget the systems it powers.
Blackberry made a pretty smart move with their acquisition of QnX, pity that it did not end with QnX being open sourced, that would have been very nice.
- The rhetoric about the world grinding to a halt isn't really pertinent and makes you look unreliable. Also, no, not "literally." I think what you're getting at is that it's chosen for high-reliability systems, with the implication being that it's chosen for its superior reliability(?)
- But I say this because it sounds like you have some knowledge as to how this obscure microkernal is used and sharing that is valuable to the community. It's just a shame if the message gets lost in the delivery.
Neither of those names will ring a bell for people who spend their days with your usual web toolsets.
So, rather grind to a halt, it would all continue running in legacy mode, users would spend more money, and it gets supported or replaced. Lots of precedents for that sort of thing.
Between acquisition price and QNX's revenues, it's unlikely support will be terminated any time soon. We wont get to see the hypothetical tested unless RIM bankrupts with nobody acquiring and supporting their assets. That a losing company acquired QNX did worry me a bit, though.
> Linus "my first, and hopefully last flamefest" Torvalds
> True, linux is monolithic, and I agree that microkernels are nicer.
It's hard to believe that he was only 23 when he wrote this
Unfortunately they were not aware yet that Windows was going to lose the Server OS war and they never pulled Singularity out of research.
Operating Systems is a 2nd year course in most universities.
Times sure have changed
Larger mono kernels: Speed
Micro kernels have advantages such as: smaller privileged attack surface and thus more secure, more crash proof as you can restart user land processes for example device drivers
Take a look at this paper (FlexSC: Flexible System Call Scheduling with Exception-Less System Calls):
https://www.usenix.org/legacy/event/osdi10/tech/full_papers/...
You can make this work by removing the page from the user process before making it available to the kernel, but the synchronization overhead of doing this (especially on a NUMA system) is probably worse than copying moderate amounts of data.
Microkernels don't copy data into the kernel address space, they copy data between userland address spaces. Which still happens in monolithic systems anyway when you're doing IPC. These are typically short messages, often only data passed in registers.
And if copying is going to be a bottleneck, then you negotiate a shared address space just like in Unix, and no more copying.
Except for your tooling. Cloudflare article from a couple years ago on why they don't use user-space network stack: https://blog.cloudflare.com/why-we-use-the-linux-kernels-tcp... and the tl:dr is a profound lack of feature parity. They use everything from iptables to tcpdump. If someone else worked on feature parity (they say it's too expensive for too small a gain for them), I expect they'd change their tune.
Which is impossible when service A and service B are both in user space, because they are in separate spaces.
Ring 0 isn't special, but you need to be monolithic if you want to avoid transitions.
And "embedded CPUs need every precious cycle" is not an argument either. As the paper says modern microkernals have a negligible speed penalty while IoT/networked industrial controllers are a security backwater.
> We have presented what is, to the best of our knowledge, the first quantitative empirical assessment of the security implications of operating system structure, i.e. monolithic vs microkernel-based design.
> Our results provide very strong evidence that operating- system structure has a strong effect on security. 96% of crit- ical Linux exploits would not reach critical severity in a microkernel-based system, 57% would be reduced to low severity, the majority of which would be eliminated alto- gether if the system was based on a verified microkernel. Even without verification, a microkernel-based design alone would completely prevent 29% of exploits.
> Given the limited number of documented exploits, we have to assume our results to have a statistical uncertainty of about nine percentage points. Taking this into account, the results remain strong. The conclusion is inevitable:
> From the security point of view, the monolithic OS design is flawed and a root cause of the majority of compromises. It is time for the world to move to an OS structure appropriate for 21st century security requirements
I mean, kind of, but since maintaining system security and integrity is a core function of the OS -- in fact, it is the primary gatekeeper in terms of all system security -- it means that "being secure" and "being correct" are often synonymous terms for an operating system.
After all, if we don't care about security at all we can all run CP/M or run everything as root.
Now, sure, you can say that the whole thing is bullshit because verified microkernels are so difficult to design that the end result would be an unusable system, but all that suggests is that when you design your kernel you should aim for a hybrid and compromise more on the side of a microkernel where you can.
But they haven't looked at a sample of exploits that were critical on an actual microkernel OS and seen how many would have been less serious (or not arisen) on a hypothetical otherwise-similar monolithic-kernel system.
It reminds me of a nice observation in "Surely you're joking, Mr Feynman". Feynman developed some nonstandard ways of solving mathematical problems. Other people came to him and he repeatedly solved problems they'd been stuck on. "He must be much smarter than us!" But the problems they brought to him were selected as ones they couldn't do, so of course he'd look better than them on those. They never bothered asking him problems he couldn't do but they could, because they'd already done them.
Now, maybe the authors of the paper are confident that there's no way that a microkernel design could encourage or exacerbate vulnerabilities. But so far as I can see they don't offer any actual argument for that proposition.
Cuz they don't exist so far. Microkernel-based systems will have same kinds of bugs as monoliths if coded in same language for same hardware. From there, the microkernel architecture leads less bugs in number (less code), less in severity (more isolation), and sometimes less difficulty in patching or recovery. If looking for microkernel-based bugs, I'd look for errors in concurrency and passing data over IPC. Monolithic system are using more concurrency and middleware than ever now, though. Even more than microkernels from what I see if talking about all the strategies and their implementations vs a few, standardized primitives. So, even those areas central to microkernel design seem like problems shared with modern monoliths.
So, the status quo is that the monoliths mostly add problems and increase their severity. Vice versa, the microkernels mostly subtract them in number and/or severity. The field evidence shows this with most of the data on bugs and vulnerability coming from monolith users. From there, someone might want to try to see if the opposite is true. Burden of proof is on them, though, with the status quo being quite reasonable. And that investigation, as I said, might find "microkernel" problems that hold in how modern monoliths are used (esp service and web architectures). Still worth attempting since they might surprise us with what they find. :)
To be clear, that's all about the architectural patterns. I think combining all the potential benefits of microkernels in a system vs a simple monolith could lead to more bugs in microkernel. Most of the problems in software will come from complexity and QA level regardless of architectural style. So, my post is written with assumption that we're talking about large, complex systems done with one style or the other.
It is a key motivator to ensure drivers remain available and supported well into the future of Linux.
My Asus Netbook no longer gets all the acceleration options that it used to have pre 16.04.
Linux is successful because it is a free beer UNIX clone.
And runnig legacy kernels? No thanks.
> My Asus Netbook no longer gets all the acceleration options that it used to have pre 16.04.
Which holds true, because /dev/radeon no longer offers hardware video decoding support it once did unless I force enable it, and even then it usually leads to random X crashes when watching videos.
And then there is this,
"For one, AMD users can’t use applications that require OpenGL 4.3 or later without the fglrx/Catalyst drivers."
https://www.omgubuntu.co.uk/2016/03/ubuntu-drops-amd-catalys...
I really fail to see how that has anything to do with Linux's unstable kernel driver API.
Graphics drivers are split into three main pieces these days.
1) Kernel space that mainly sets up the GPU's MMU, and adds a context to the GPU's hardware thread scheduler. There'll be some modesetting too, but that piece is really simple (and fglrx never used the main kernel API for that anyway, so it doesn't really matter if it was stable or not. But it actually was pretty stable over the time frame we're talking about).
This piece still works fine on fglrx with a modern kernel.
2) A userspace component that lives with the window manager setting up the actual display output, and accelerating compositing. Stuff like EGL works by making IPC calls to this layer.
This is the piece that broke in your case, and only because the x server decided to change.
3) Another piece that runs in userspace and is ultimately what gets called by graphics APIs and is linked into every process making graphics calls. This is the vast majority of the driver.
Ah, the Linux evangelist blame-game. It's a big advantage of a system being so haphazardly thrown together from separately developed components. Start by blaming the choice of distro, end up at "Linux is just a kernel".
How does that apply here when Linux didn't change and you can still use the same kernel driver, but some other component decided to not work with the driver anymore?
Contrast with when windows changed the video driver architecture in Vista, and the only option you had was to pound sand.
I can either spend thousands of dollars worth of my time on updating the driver, or I can pay someone else thousands of dollars to do it. Or I can spend a fraction of that on a new video card.
Seems like the only solution for Vista users is the only solution I'd ever have gone with, anyway.
I tend to fall on the side of the root poster - if having a stable driver API means Linux gets more commercial driver support, then that's the one that has the highest cost/benefit in my book.
In practical terms, being able to hack on open-source drivers isn't particularly useful to me, but having an easier user experience with Linux on the desktop (and, more generally, having Linux on the desktop be something more than an also-ran) would benefit me immensely.
Any operating system that wishes stability therefore has to put barriers between themselves and the driver. And, preferably, should use drivers that they can audit themselves rather than trusting OEMs.
As an example of this outside of the open source world, the biggest reason why Windows used to have a reputation for BSODs is that they were dependent on third party drivers. Windows made it harder for third parties to take down their OS, shipped tools to audit drivers for bugs, and forced OEMs to clean up their act. (Which they didn't do voluntarily.)
The actual choice is whether to have limited hardware choices or hardware that crashes regularly. Put that way, it is obvious to me that limited hardware is the right answer.
Why? Because what I care about is having a system that works well for me. Limited choices are fine as long as I can determine in advance whether the system that I'm considering will work. (I usually can.) So now my choice boils down to, "Do I want to be able to buy a reliable system, or be forced to put up with a buggy one?"
Put that way, who wants to be forced to put up with bugs?
In that tradeoff, I'll easily pick the marginally smaller market with vastly better drivers.
Creative Fucking Labs.
Someone told me back then that the sound blaster drivers were responsible for more crashes than the next several causes combined, so I started watching and I’ll be damned if I didn’t see the same thing.
I doubt it. Linux desktop's problems run far, far deeper than that one questionable choice.
I am quite convinced that if they kept it that way it was because some unplanned property caused worse driver status with an API; too many delays, improper usage I don't know.
If there's no solid reason, then I'd be happy to have split codebases.
You can have hybrid systems where the code runs in isolation but the pull requests are still self contained instead of split into multiple pieces that have to be coordinated.
When I worked for a NIC hardware vendor, we would ship our driver in 4 forms:
1) source tarball
2) upstream kernel
3) RHEL/Centos kABI compliant source and binary rpms
4) Debian pkg using dkms
The upstream kernel driver wasn't good enough for a variety of reasons. For example, on Ubuntu LTS and RHEL, the in-tree driver was often based on a kernel that was several years old and which lacked support for recent hardware or features.
What claim does it discredit exactly?
https://en.wikipedia.org/wiki/OS4000
The performance wasn't just because Nucleus initially was in hard/firmware; two later software implementations were performant (on faster hardware). Also, as the article is about security: at least the original Nucleus also supported an A1/B3-level secure OS.
I think that's one thing I don't want just reasonable
In real life there are certain parts of the OS that have to work or the whole device stops working. Furthermore: the isolation of dynamic and less tested application code from these parts is generally a good idea, that's why monolithic OSes are so popular; they're simply less demanding.
The goal is to minimize the trusted computing base (TCB) so that it is, at least to some degree, verifiably correct. Then tack on features using isolated components.
So "${thing} is flawed" is not precise enough; an interesting statement would be "${thing} is not the best choice for ${conditions}". A monolithic OS is not the best choice for a high-reliability system on unreliable hardware. A microkernel OS that widely uses hardware memory protection is not the best choice for a controller with 4KB of RAM. A unikernel setup is not the best choice for a desktop system where the user is expected to constantly install new software. Etc, etc.
In other words, the ancient concept of "right tool for the job" still applies.
Or use a multi-tool ;)
In this context, it should be pretty obvious that a design that fails to minimise the trusted computing base is flawed. Even if a kernel vulnerability is unlikely to kill any given user, the sum of all the crashes, hacks, patching effort… is huge.
I bet my hat rewriting the entire kernel for all popular OSes would be far cheaper worldwide than not doing it. (Of course, this won't happen any time soon, because path dependence and network effects. Unless maybe someone works seriously on the 30 million lines problem described by Casey Muratory.)
> In other words, the ancient concept of "right tool for the job" still applies.
Absolutely. Monolithic kernels are clearly the wrong tool for the job.
Says who exactly?
> The security benefits of keeping a system’s trusted computing base (TCB) small has long been accepted as a truism, as has the use of internal protection boundaries for limiting the damage caused by exploits. Applied to the operating system, this argues for a small microkernel as the core of the TCB, with OS services separated into mutually-protected components (servers) – in contrast to “monolithic” designs such as Linux, Windows or MacOS. While intuitive, the benefits of the small TCB have not been quantified to date. We address this by a study of critical Linux CVEs, where we examine whether they would be prevented or mitigated by a microkernel-based design. We find that almost all exploits are at least mitigated to less than critical severity, and 40% completely eliminated by an OS design based on a verified microkernel, such as seL4.
If the effect is that huge, of course security trumps pretty much all other considerations. These are consumer OS kernels we're talking about. One that fails to more or less maximise security is obviously the wrong tool for the job. As the title of the paper suggests, in case you failed to read that as well.
Such as?
The problems are really the flawed mental models people insist on bringing to these problems, despite decades of research showing these models are irreparably flawed.
Security requires to identify yourself with hard-to-fake means, it takes time and effort (recollecting and typing a password, fumbling with a 2FA token); ease of use asks for trusting and immediate response (light switch, tv, etc).
Performance asks for uninterrupted execution and scheduling of tasks based on throughput; ease of use asks for maximum resources given to the interactive application, and scheduling based on lowest interactive latency.
Also feature set vs source code observability, simplicity vs configurability, performance vs modularity, build time vs code size vs code speed, etc.
Every OS is vulnerable to the hardware upon which it runs, but capability security at least makes side channel attacks somewhat more difficult because of least privilege and limiting access to non-deterministic operations, like the clock.
Identity-based security built on an authorization-based model like capabilities also ensures it's difficult to make promises you can't keep. Access list models let you easily claim unenforceable properties and then people are surprised when they are easily violated.
> ease of use asks for maximum resources given to the interactive application, and scheduling based on lowest interactive latency.
That's unnecessary. You need a low latency upper bound, not a "lowest latency". This does not necessarily conflict with throughput, and furthermore, and install requiring high throughput and interactivity rarely overlap.
I'm not even sure what the rest of the properties are supposed to be about. I don't think most of those are mutually exclusive either.
Tech and market pressure will make more capable processors affordable if security is prioritised.
For a small system like that, the shining ideal is probably a formally verified single program with no real OS to speak of.
I'd want to see a solid paper comparing the security of the approach you mention to a microkernel+app. Until then we have this.
But agreed, there are other ways, of varying practicality, to achieving security.
Anyone tried that?
I am not too much about particular alternatives.
See I can make clickbait titled papers also.
* https://news.ycombinator.com/item?id=15642116
* https://news.ycombinator.com/item?id=15634014
This probably sounds trollish, but security isn't that important. An OS architecture has to take into account other things too.