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

[Florian Weimer <fweimer@redhat.com>]

Commit ff026950e280bc3e9487b41b460fb31bc5b57721 ("Add a C wrapper for
prctl [BZ #25896]") replaced the assembler wrapper with a C function.
However, the C variadic function implementation has a different ABI
on powerpc64le-linux-gnu.  Switch back to the assembler implementation
on most targets and only keep 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.

Notes:

This is just a repost of my previous patch.  I still think it is the
right thing to do.  We now have a second case where the varargs
implementation causes stack corruption on powerpc64le-linux-gnu.  This
time it's the libasan interceptor for prctl:

  libasan uses incorrect prctl prototype
  <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113728>

Thanks,
Florian

---
 sysdeps/unix/sysv/linux/syscalls.list            | 1 +
 sysdeps/unix/sysv/linux/{ => x86_64/x32}/prctl.c | 5 +----
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
index 73e941ef89..9ac42c3436 100644
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -46,6 +46,7 @@ open_tree	EXTRA	open_tree	i:isU	open_tree
 pipe2		-	pipe2		i:fi	__pipe2		pipe2
 pidfd_open	EXTRA	pidfd_open	i:iU	pidfd_open
 pidfd_getfd	EXTRA	pidfd_getfd	i:iiU	pidfd_getfd
+prctl		EXTRA	prctl		i:iiiii	__prctl		prctl __prctl_time64
 pivot_root	EXTRA	pivot_root	i:ss	pivot_root
 pidfd_send_signal	EXTRA	pidfd_send_signal	i:iiPU	pidfd_send_signal
 process_madvise EXTRA   process_madvise i:iPniU process_madvise
diff --git a/sysdeps/unix/sysv/linux/prctl.c b/sysdeps/unix/sysv/linux/x86_64/x32/prctl.c
similarity index 93%
rename from sysdeps/unix/sysv/linux/prctl.c
rename to sysdeps/unix/sysv/linux/x86_64/x32/prctl.c
index 52d234ea0d..4bf1b479a0 100644
--- a/sysdeps/unix/sysv/linux/prctl.c
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/prctl.c
@@ -1,4 +1,4 @@
-/* prctl - Linux specific syscall.
+/* prctl - Linux specific syscall.  x86-64 x32 version.
    Copyright (C) 2020-2024 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -40,6 +40,3 @@ __prctl (int option, ...)
 
 libc_hidden_def (__prctl)
 weak_alias (__prctl, prctl)
-#if __TIMESIZE != 64
-weak_alias (__prctl, __prctl_time64)
-#endif

base-commit: 7c8df0b9441e34928f2d7d70531e3d55e016c32e