[Bug string/29234] Bug in rawmemchr-avx2 can return incorrect result

["goldstein.w.n at gmail dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29234

--- Comment #4 from Noah Goldstein <goldstein.w.n at gmail dot com> ---
you spooked me :)


On Thu, Nov 2, 2023 at 11:22 AM carlos at redhat dot com
<sourceware-bugzilla@sourceware.org> wrote:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=29234
>
> Carlos O'Donell <carlos at redhat dot com> changed:
>
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>    Target Milestone|---                         |2.36
>          Resolution|---                         |FIXED
>                  CC|                            |carlos at redhat dot com
>              Status|UNCONFIRMED                 |RESOLVED
>
> --- Comment #3 from Carlos O'Donell <carlos at redhat dot com> ---
> Fixed already.
>
> commit 2c9af8421d2b4a7fcce163e7bc81a118d22fd346
> Author: Noah Goldstein <goldstein.w.n@gmail.com>
> Date:   Wed Jun 8 14:34:59 2022 -0700
>
>     x86: Fix page cross case in rawmemchr-avx2 [BZ #29234]
>
>     commit 6dcbb7d95dded20153b12d76d2f4e0ef0cda4f35
>     Author: Noah Goldstein <goldstein.w.n@gmail.com>
>     Date:   Mon Jun 6 21:11:33 2022 -0700
>
>         x86: Shrink code size of memchr-avx2.S
>
>     Changed how the page cross case aligned string (rdi) in
>     rawmemchr. This was incompatible with how
>     `L(cross_page_continue)` expected the pointer to be aligned and
>     would cause rawmemchr to read data start started before the
>     beginning of the string. What it would read was in valid memory
>     but could count CHAR matches resulting in an incorrect return
>     value.
>
>     This commit fixes that issue by essentially reverting the changes to
>     the L(page_cross) case as they didn't really matter.
>
>     Test cases added and all pass with the new code (and where confirmed
>     to fail with the old code).
>     Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
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