Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH 2/2] x86/asm/entry/32: Shorten __audit_syscall_entry args preparation | Date | Tue, 9 Jun 2015 15:52:55 +0200 |
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We use three MOVs to swap edx and ecx. We can use one XCHG instead.
Expand the comments. It's difficult to keep track which arg# every register corresponds to, so spell it out.
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/entry/entry_64_compat.S | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 411407a..d0b6494 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -178,12 +178,16 @@ sysexit_from_sys_call: #ifdef CONFIG_AUDITSYSCALL .macro auditsys_entry_common - movl %esi, %r8d /* 5th arg: 4th syscall arg */ - movl %ecx, %r9d /* swap with edx */ - movl %edx, %ecx /* 4th arg: 3rd syscall arg */ - movl %r9d, %edx /* 3rd arg: 2nd syscall arg */ - movl %ebx, %esi /* 2nd arg: 1st syscall arg */ - movl %eax, %edi /* 1st arg: syscall number */ + /* + * At this point, registers hold syscall args in 32-bit ABI: + * eax is syscall#, args are in ebx,ecx,edx,esi,edi,ebp. + * Shuffle them to match what __audit_syscall_entry() wants. + */ + movl %esi, %r8d /* arg5 (r8): 4th syscall arg */ + xchg %ecx, %edx /* arg4 (rcx): 3rd syscall arg (edx) */ + /* arg3 (rdx): 2nd syscall arg (ecx) */ + movl %ebx, %esi /* arg2 (rsi): 1st syscall arg */ + movl %eax, %edi /* arg1 (rdi): syscall number */ call __audit_syscall_entry /* * We are going to jump back to syscall dispatch. -- 1.8.1.4
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