3.16.72-rc1 review patch. If anyone has any objections, please let me know.
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From: Aurelien Jarno aurelien@aurel32.net
commit 79b4a9cf0e2ea8203ce777c8d5cfa86c71eae86e upstream.
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 Reviewed-by: Philippe Mathieu-Daudé f4bug@amsat.org Signed-off-by: Paul Burton paul.burton@mips.com Cc: Ralf Baechle ralf@linux-mips.org Cc: James Hogan jhogan@kernel.org Cc: linux-mips@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/mips/kernel/scall64-o32.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/mips/kernel/scall64-o32.S +++ b/arch/mips/kernel/scall64-o32.S @@ -124,7 +124,7 @@ trace_a_syscall: subu t1, v0, __NR_O32_Linux move a1, v0 bnez t1, 1f /* __NR_syscall at offset 0 */ - lw a1, PT_R4(sp) /* Arg1 for __NR_syscall case */ + ld a1, PT_R4(sp) /* Arg1 for __NR_syscall case */ .set pop
1: jal syscall_trace_enter