Re: [PATCH] MIPS: scall64-o32: Fix indirect syscall number load

[Paul Burton <paul.burton@mips.com>]

Hello,

Aurelien Jarno wrote:
> Commit 4c21b8fd8f14 (MIPS: seccomp: Handle indirect system calls (o32))
> added indirect syscall detection for O32 processes running on MIPS64,
> but it did not work correctly for big endian kernel/processes. The
> reason is that the syscall number is loaded from ARG1 using the lw
> instruction while this is a 64-bit value, so zero is loaded instead of
> the syscall number.
> 
> Fix the code by using the ld instruction instead. When running a 32-bit
> processes on a 64 bit CPU, the values are properly sign-extended, so it
> ensures the value passed to syscall_trace_enter is correct.
> 
> Recent systemd versions with seccomp enabled whitelist the getpid
> syscall for their internal  processes (e.g. systemd-journald), but call
> it through syscall(SYS_getpid). This fix therefore allows O32 big endian
> systems with a 64-bit kernel to run recent systemd versions.
> 
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> Cc: <stable@vger.kernel.org> # v3.15+
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Applied to mips-fixes.

Thanks,
    Paul

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