linux-kernel - Re: [PATCH -mm] -funsigned-char, x86: make struct p4_event

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Message-ID: <CAHmME9qBZqTd0D_gr8nE+DUzCrC0fxZNZK=7u+21jbgtFgAJBg@mail.gmail.com>
Date:   Thu, 20 Oct 2022 11:33:39 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Alexey Dobriyan <adobriyan@...il.com>, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, mm-commits@...r.kernel.org,
        masahiroy@...nel.org, keescook@...omium.org,
        gregkh@...uxfoundation.org, andriy.shevchenko@...ux.intel.com,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH -mm] -funsigned-char, x86: make struct p4_event_bind::cntr
 signed array

Hi Linus,

On Thu, Oct 20, 2022 at 11:15 AM Linus Torvalds
<torvalds@...ux-foundation.org> 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