[PATCH v3] Linux: Switch back to assembly syscall wrapper for prctl (bug 29770)

[PATCH v3] Linux: Switch back to assembly syscall wrapper for prctl (bug 29770)

[Florian Weimer]

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.

---
v3: Commit message updated.

 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: 491e55beab7457ed310a4a47496f4a333c5d1032

RE: [PATCH v3] Linux: Switch back to assembly syscall wrapper for prctl (bug 29770)

[Simon Chopin]

Hi Florian,

On mer. 14 févr. 2024 16:55:10, Florian Weimer wrote:
> 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.
>
> ---
> v3: Commit message updated.
>
>  sysdeps/unix/sysv/linux/syscalls.list            | 1 +
>  sysdeps/unix/sysv/linux/{ => x86_64/x32}/prctl.c | 5 +----
>  2 files changed, 2 insertions(+), 4 deletions(-)

LGTM, the extra info in the commit logs are much appreciated :)

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

>
> 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: 491e55beab7457ed310a4a47496f4a333c5d1032
>