diff-zoo VS src

To add to software for #1, look for packages that do forward-mode AD. For Jacobians (many outputs), forward-mode AD is often faster than back-propagation (reverse mode). I use ForwardDiff.jl which usually accepts any function the user might bass in as observation function https://github.com/baggepinnen/LowLevelParticleFilters.jl/blob/master/src/ekf.jl#L45 Here's a nice intro to forward and reverse mode ad https://github.com/MikeInnes/diff-zoo/blob/notebooks/backandforth.ipynb It's the second notebook in a series, might want to read the first as well if you find this topic interesting.

This is an obscure one, but Mike Innes "[automatic] differentiation for hackers" tutorial. It's a code tutorial, not software, if that counts. Both the way it's constructed and the functionality of Julia that gets shown off here.

https://github.com/MikeInnes/diff-zoo

The following repos show how to build a simple reverse mode implementation from scratch: https://github.com/MikeInnes/diff-zoo

The OpenBSD project released 7.4 of their OS on 16 Oct 2023 as their 55th release 💫

Well since https://www.openbsd.org/ still says

> Only two remote holes in the default install, in a heck of a long time!

I'm assuming not, but I could always be mistaken.

> building a cat from scratch

> That would be an interesting project.

Here is the source code of the OpenBSD implementation of cat:

> https://github.com/openbsd/src/blob/master/bin/cat/cat.c

and here of the GNU coreutils implementation:

> https://github.com/coreutils/coreutils/blob/master/src/cat.c

Thus: I don't think building a cat from scratch or creating a tutorial about that topic is particularly hard (even though the HN audience would likely be interested in it). :-)

> I don't know how they define `MAX`, but I'm guessing it's a typical "a>b?a:b"

Indeed: https://github.com/openbsd/src/blob/master/sys/sys/param.h#L...

> Then `SYS_kbind` seems to be a signed int.

It's an untyped #define: https://github.com/openbsd/src/blob/master/sys/sys/syscall.h...

I believe your whole analysis is correct, that running an elf file with an openbsd.syscalls entry with .sysno > INT_MAX will allow an out-of-bounds write.

I can reproduce it. And this is the commit that causes the issue: https://github.com/openbsd/src/commit/d21788ce70be80e9c4ed0c52c149e01147c4a823

This doesn’t really change your conclusion, but I think that’s the wrong file. This is the real doas afaict: https://github.com/openbsd/src/blob/master/usr.bin/doas/doas...

Still just a tidy 1072 lines in that folder though.

I spent 5 minutes staring at your file trying to understand how on earth it does the things in the man page, but of course it doesn’t.

OpenBSD developers are making serious effort to kill off indirect syscalls, the base system is completely clean, take a look at the work Andrew Fresh did to adapt Perl. He write a complete syscall "dispatcher" or emulator for the Perl syscall function so that it calls the libc stubs.

https://github.com/openbsd/src/commit/312e26c80be876012ae979...

The ports tree is also being cleansed of syscall(2) usage, until they're all gone.

msyscall, pinsyscall, recent mandatory IBT/BTI, xonly. OpenBSD is making waves, but people aren't really seeing them yet.

Actually, I got it wrong, too many vulnerabilities in flight. They did fix it: https://github.com/openbsd/src/commit/375ccafb2eb77de6cf240e...