Show HN: My CV is also a bootloader | Hacker News Reader

Show HN: My CV is also a bootloader

github.com

255 pointsgef323350 comments

Congrats on a cool project.

As a hiring manager for embedded software engineers, I have a couple of thoughts that maybe helpful. I come at it from an american perspective, and I know europ is different but anyways:

1. I have to be able to read your CV. When I click on the link on github it says error, and I had dig around to figure out how to open it. When I’m scanning applicants I’d probably have just said “oh they don’t even know how to attach a pdf”. I know how cute it is, but I have to able to see your CV.

2. What do you want? Your CV is a good CV, in the sense of it lists what you’ve done. But give me a short executive summary, what do you want, what amazing thing have you done? But it’s also really long for someone with no work experience. Condense it down.

2a. Yes you might include a cover letter, but when I call you I’ll have your CV open, don’t make me hunt for it.

2b. Example: https://www.businessinsider.com/why-this-is-an-excellent-res...

3. Your FAQ, this rubs me really wrron “Writing a boot loader is REALLY HARD.” Ok I’ve writen a few, and it’s real pain in the ass, especially since you’re normally bringing up hardware while doing it that may not work. But it’s a solved problem that’s painful. Tell me you did it to learn and expand your knowledge and learn asm. That’s more impresive imho.

Keep up the good work!

Thanks, that is amazing feedback! I am looking into the issue of the PDF not loading in github, probably I just have to put the magic numbers sooner.

You are also right on the FAQ part, this was more a learning exercise to prove if I could learn and do this more than anything, I have to update the README with further instructions and will most likely address this.

Just put a prominent link with ?raw=true in README.md.

https://github.com/pjimenezmateo/curriculum-bootloader/blob/...

this is impressive. Despite other comments going against the intelligence of recruiters, I got no doubt everyone (even without tech background) will get the point of why this is cool.

if you're interested in Polygots the POC||GTFO¹ pdf's have you covered.

Volume 0x07 is a PDF, a Zip file, a BPG (Better Portable Graphics) and an HTML file all in one.

Even crazier than pocorgtfo07.pdf, the pocorgtfo16.pdf is valid as a PDF document, a ZIP archive, and a Bash script that runs a Python webserver which hosts Kaitai Struct’s WebIDE which, allows you to view the file’s own annotated bytes. The zip archive has further resources to insane reversing deep dives, code to study and more.

For me this is art!

[¹] https://www.alchemistowl.org/pocorgtfo/

I did not know about this! I agree this is art! I am bookmarking this to check it in more detail, thanks!

This is really cool, but if I may make a suggestion: Not everyone actually wants to run the bootloader, and technical hiring managers certainly won't.

Include a video taken with a screen recording tool, from your host workstation, showing the thing booting in a 640x480 QEMU window. Or something similar.

Quick tip - screenshot is good, but add a video of the bootloader in action, it will get you more shares from the visual crowd.

Awesome project.

> a custom bootloader created by me to impress technical recruiters

But do recruiters actually understand what a bootloader is or why this is such a feat? Do you know of a recruiter that has ran it?

That is a very good question, I just finished it today but I guess that at least they would be curious about it and improve my chances :)

I too think it’s an awesome project, I wasn’t going to comment because I didn’t have anything to add so I thought I’d say how neat it was in this thread ;)

Thanks :) actually the positive comments such as yours are very valuable when people present their work, and I appreciate them.

Don't work for a recruiter who doesn't know what this is?

I don't mean to ruin it for gef3233 here, but seeing that it's missing the magic header required for PDFs, I'd be surprised if there are PDF viewers that would try to interpret this. I would even consider trying to interpret this "PDF" without checking for the magic number to be a bug.

Looking at the PDF spec[1], it says:

> The first line of a PDF file shall be a header consisting of the 5 characters %PDF– followed by a version number of the form 1.N, where N is a digit between 0 and 7.

where a line is:

> Each line shall be terminated by an end-of-line (EOL) marker, which may be a CARRIAGE RETURN (0Dh), a LINE FEED (0Ah), or both

On binary data:

> If a PDF file contains binary data, as most do (see 7.2, "Lexical Conventions"), the header line shall be immediately followed by a comment line containing at least four binary characters—that is, characters whose codes are 128 or greater

I'm sorry, but I don't think the file qualifies as a PDF if it doesn't meet these requirements. Still, it's pretty cool if this is PDF-like.

`gunzip`, `tar`, `jpg`, etc. fail when I give them things that don't have the magic header they expect. It's a good convention to use magic numbers to not misinterpret files.

[1] https://www.adobe.com/content/dam/acom/en/devnet/pdf/PDF3200...

So what happens if you try to execute "%PDF-1.<number-between-0-and-7>\n%<4-bytes-above-128>\n" as x86 real-mode machine code anyway? Can't this be modified to simply undo whatever the PDF magic header would do if it was present?

Interestingly, GitHub refuses to display the PDF, saying that it's invalid: https://github.com/pjimenezmateo/curriculum-bootloader/blob/...

The PDF is basically the assembled bootloader + PDF file, which starts after a few bytes.

Some PDF parsers expect the %PDF header at the beginning of the file, which explains why it does not display on Github.

It does work on macOS Preview though. I'm scared of opening any downloaded file, by now ;)

doesnt work for mupdf either

Interesting, I have been testing it and apparently it is Firefox's PDF.js that does not like it. I still don't know why. If you are using chrome (or even Edge) it should work.

I get

"There was an error opening this document. The file is damaged and could not be repaired."

when trying to open with Adobe Reader.

Oh, this one I did not check. Thanks, this is very important document reader, I will look into it.

Doesn’t work in iOS safari.

FWIW, cv.pdf works in emacs (on mac)!

Doesn't work in Adobe Acrobat, so in context of providing it to recuiters, I'd say your effort is futile.

Since this seems to be the "doesn't work on [reader]" thread, this file doesn't open in SumatraPDF either. I saw someone suggest appending "?raw=true" to the PDF download link, but that didn't work for me either.

It should be fixed now!

That is fixed now! :)

This is very cool!

I have one suggestion with your readme. For someone who has used dd and is familiar with what needs to be done to check and change the value of /dev/sdX in your example before using it, this has all the information I need, and it's great that you included a "please be careful" line.

But my suggestion is you might add just one or two more lines of explanation for newbies who might wonder what part of the command they should take care with, and how to check the device name. You really do already have a lot of the necessary information here, I'm just saying that for newbies, given the high stakes of potentially destroying a disk or a system, you might add just a tiny bit more to clarify that when you say "drive" you mean the same thing as "device" and when you say "select" you don't mean select the drive in the UI such as by using the mouse, you instead mean specify the right device in the command line.

    NOTE: Please be very careful with this command. If you 
    select the wrong drive you will lose data.

    Get a USB, check the device name and do:

    sudo dd if=cv.pdf of=/dev/sdX bs=512 count=2880

    where X is your device.

Edited example line(s):

    Get a USB, check the device name (on Linux, for
    example, by using sudo fdisk -l before and after
    inserting the device and comparing the output to
    see how the system identifies the newly plugged
    in device) and do:

I would agree with anyone who said that newbies are not your target audience for this. But in the spirit of open source there are always people out there learning and your project will be fascinating to some of them.

Seeing the comments about incompatibility above, I wonder if docx would be a better format for such a "polyglot format CV". AFAIK docx is a ZIP, and in a ZIP file the header/directory is located at the end of the file, so technically the beginning of the file can be "garbage".

(Not tested)

Edit: rereading, I also did not mean to imply the boot loader = garbage :) More that bytes that comprise a boot loader would look like garbage to the ZIP format.

Cool project

But don't worry, the interviewers will still ask you to do a fizzbuzz on the board, or ask to invert a linked list

Very nice! Two things:

You're assuming the user has dd available. You might want to include instructions for something like Rufus if they're on Windows. Even if they have dd, you should probably add a lot more warnings with regards to its usage. One innocent typo or moment of inattention and their system is toast.

The second is just a small typo here:

>... by two means, in real hardware (I spend a lot of time making it compatible) of in an emulated environment.

Thanks, I think that is a very good idea, I will add instructions for windows and also how to recover your USB to normal usage.

And thanks for the typo, will fix :)

Nice! You might enjoy my bootloader + retro game which fits in a tweet: https://www.quaxio.com/bootable_cd_retro_game_tweet/

It might also help you figure out how to put the pdf first. You'll increase the odds of various viewers being able to render the pdf.

That is an impressive project! Thanks for sharing.

Brilliant things like this make me sad that recruiters almost universally mangle nice pdfs to add their header and remove personal contact details. If you're going direct, though, should be no problem.

Congrats on a project that makes me wish I'd thought of it first.

Surely this offends some virus scanners.

Very impressive. I do hope that a recruiter who understands this sees it.

This is one of the coolest thing I've seen, ever.

That's impressive. Nicely done.

Thanks :) I am very proud of this project.

Put the technologies you used next to the projects you worked on. Just listing "Python" or "SQL" without context isn't meaningful.

Similarly, it's not clear what you actually did in the projects. Write it more like: "Implemented X for Y using Z" and add in some benchmarks such as "reduced overhead by 12%" or "scaled to 100,000 clients", if possible.

> a custom bootloader created by me to impress technical recruiters

Recruiters don't have time to go through the process just to see your CV.

You won't impress them.

I'm not a recruiter, but I am a hiring manager and I'm impressed.

I'm not going to go through the assembly with a fine-grained comb, but I don't need to. The existence of the final result demonstrates someone who persevered to do something novel that required more than a superficial understanding of their tools. It also lends itself to interesting questions for an interview (what was hardest, what would you change, are there other file formats that could work with this).

It's not by itself something that makes me want to hire you, but it certainly makes me want to talk to you.

Thank you! This is exactly what I was aiming to, I don't expect the recruiter to go through the process but at least I can easily show some technical background.

It’s a valid PDF that can also be used as a boot loader.

That’s missing the point. His resume is now on the front page of HN!

Also, the resume opens as a regular PDF, so there’s no extra work to see it unless you want to try the bootloader.

Judging by the emails I receive it doesn’t take much to impress some recruiters. I had one tell me one of my Github projects was impressive. The problem is the repo was literally empty.

Another was impressed by https://github.com/tlrobinson/evil.css/

ಠ_ಠ

I bet the recruiter just looked at the stars and said "yeah that's got to be a cool repo"

I've been contact by recruiters who must've heard from their peers that GitHub 'stars' were a good thing, so they mailed me being impressed by the number of repositories I had starred (which is what shows up in your GH profile page).

"Please don't post shallow dismissals, especially of other people's work."

https://news.ycombinator.com/newsguidelines.html

Especially not in Show HN threads:

https://news.ycombinator.com/showhn.html

The idea behind it is that you don't need to go to the process, I am telling you that it is possible to do this and if you don't believe me you can verify it.

Reply on news.ycombinator.com