[Bug libc/29770] prctl does not match manual page ABI on powerpc64le-linux-gnu

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29770

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2.40
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Florian Weimer <fweimer at redhat dot com> ---
Fixed for 2.40 via:

commit 6a04404521ac4119ae36827eeb288ea84eee7cf6
Author: Florian Weimer <fweimer@redhat.com>
Date:   Sat Feb 17 09:17:04 2024 +0100

    Linux: Switch back to assembly syscall wrapper for prctl (bug 29770)

    Commit ff026950e280bc3e9487b41b460fb31bc5b57721 ("Add a C wrapper for
    prctl [BZ #25896]") replaced the assembler wrapper with a C function.
    However, on powerpc64le-linux-gnu, the C variadic function
    implementation requires extra work in the caller to set up the
    parameter save area.  Calling a function that needs a parameter save
    area without one (because the prototype used indicates the function is
    not variadic) corrupts the caller's stack.   The Linux manual pages
    project documents prctl as a non-variadic function.  This has resulted
    in various projects over the years using non-variadic prototypes,
    including the sanitizer libraries in LLVm and GCC (GCC PR 113728).

    This commit switches back to the assembler implementation on most
    targets and only keeps the C implementation for x86-64 x32.

    Also add the __prctl_time64 alias from commit
    b39ffab860cd743a82c91946619f1b8158b0b65e ("Linux: Add time64 alias for
    prctl") to sysdeps/unix/sysv/linux/syscalls.list; it was not yet
    present in commit ff026950e280bc3e9487b41b460fb31bc5b57721.

    This restores the old ABI on powerpc64le-linux-gnu, thus fixing
    bug 29770.

    Reviewed-By: Simon Chopin <simon.chopin@canonical.com>


We can consider backporting.

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