[PATCH 16/17] x86: entry_64.S: trivial optimization for ENOSYS

From: Denys Vlasenko
Date: Fri Aug 08 2014 - 13:46:50 EST

This code uses a slightly shorter insn.

Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: Oleg Nesterov <oleg@xxxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CC: X86 ML <x86@xxxxxxxxxx>
CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
CC: Will Drewry <wad@xxxxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: linux-kernel@xxxxxxxxxxxxxxx
arch/x86/kernel/entry_64.S | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 7bc8c24..5d639a6 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -272,6 +272,7 @@ system_call_fastpath:
ja badsys
movq %r10,%rcx
call *sys_call_table(,%rax,8) # XXX: rip relative
movq %rax,RAX(%rsp)
* Syscall return path ending with SYSRET (fast path)
@@ -334,8 +335,8 @@ sysret_signal:
jmp int_check_syscall_exit_work

- movq $-ENOSYS,RAX(%rsp)
- jmp ret_from_sys_call
+ movq $-ENOSYS,%rax
+ jmp from_badsys


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