[PATCH 4/8] x86/asm/entry/64: optimize [v]fork/clone stubs

From: Denys Vlasenko
Date: Tue Apr 07 2015 - 16:44:33 EST


Replace "call func; ret" with "jmp func".

Run-tested.

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

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 8e3ba38..6ad30a7 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -407,8 +407,7 @@ ENTRY(stub_\func)
CFI_STARTPROC
DEFAULT_FRAME 0, 8 /* offset 8: return address */
SAVE_EXTRA_REGS 8
- call sys_\func
- ret
+ jmp sys_\func
CFI_ENDPROC
END(stub_\func)
.endm
--
1.8.1.4

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