Re: [PATCH 3/4] x86/asm/entry/64: use smaller insns

Andy Lutomirski
2015-03-25T18:03:34Z

On Wed, Mar 25, 2015 at 10:18 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
> The $AUDIT_ARCH_X86_64 parameter to syscall_trace_enter_phase1/2
> is a 32-bit constant, loading it with 32-bit MOV produces 5-byte insn
> instead of 10-byte one.

Acked-by: Andy Lutomirski <luto@kernel.org>

>
> Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Steven Rostedt <rostedt@goodmis.org>
> CC: Ingo Molnar <mingo@kernel.org>
> CC: Borislav Petkov <bp@alien8.de>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: Alexei Starovoitov <ast@plumgrid.com>
> CC: Will Drewry <wad@chromium.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: x86@kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
> arch/x86/kernel/entry_64.S | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index 11b7339..23aa43e 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -306,7 +306,7 @@ system_call_fastpath:
> /* Do syscall entry tracing */
> tracesys:
> movq %rsp, %rdi
> - movq $AUDIT_ARCH_X86_64, %rsi
> + movl $AUDIT_ARCH_X86_64, %esi
> call syscall_trace_enter_phase1
> test %rax, %rax
> jnz tracesys_phase2 /* if needed, run the slow path */
> @@ -317,7 +317,7 @@ tracesys:
> tracesys_phase2:
> SAVE_EXTRA_REGS
> movq %rsp, %rdi
> - movq $AUDIT_ARCH_X86_64, %rsi
> + movl $AUDIT_ARCH_X86_64, %esi
> movq %rax,%rdx
> call syscall_trace_enter_phase2
>
> --
> 1.8.1.4
>

--
Andy Lutomirski
AMA Capital Management, LLC