Re: [PATCH -mm] -funsigned-char, x86: make struct p4_event_bind::cntr signed array

From: Jason A. Donenfeld
Date: Thu Oct 20 2022 - 13:34:08 EST


Hi Linus,

On Thu, Oct 20, 2022 at 11:15 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> Can we please try to collect these all in one place?
>
> I see that Andrew picked up the original one for -mm, but I think it
> would be better if we had one specific place for all of this (one
> branch) to collect it all.

Sure. Andrew can drop it from -mm, and I'll collect everything in:

https://git.kernel.org/pub/scm/linux/kernel/git/zx2c4/linux.git/log/?h=unsigned-char&r

And I'll ask Stephen to add that branch to -next.

> I'm actually trying to do a "make allyesconfig" build on x86-64 with
> both signed and unsigned char, and trying to see if I can script
> something sane to show differences.
>
> Doing the build is easy, but the differences end up being huge just
> due to silly constants (ie the whole "one small difference ends up
> changing layout, which then causes hundreds of megs of diff just due
> to hex constants in the disassembly changing".

If you can get a copy of IDA Pro, diaphora is quite nice:
https://github.com/joxeankoret/diaphora

Or sometimes with objdump, I've had more success by keeping debug
symbols, and then trimming offsets from jmps.

Jason