[PATCH 4.14 040/159] x86/entry/64: Use pop instead of movq in syscall_return_via_sysret

Greg Kroah-Hartman
2017-12-22T09:00:15Z

From: Andy Lutomirski <luto@kernel.org>

commit 4fbb39108f972437c44e5ffa781b56635d496826 upstream.

Saves 64 bytes.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/6609b7f74ab31c36604ad746e019ea8495aec76c.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/entry/entry_64.S | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -316,10 +316,18 @@ return_from_SYSCALL_64:
*/
syscall_return_via_sysret:
/* rcx and r11 are already restored (see code above) */
- RESTORE_EXTRA_REGS
- RESTORE_C_REGS_EXCEPT_RCX_R11
- movq RSP(%rsp), %rsp
UNWIND_HINT_EMPTY
+ POP_EXTRA_REGS
+ popq %rsi /* skip r11 */
+ popq %r10
+ popq %r9
+ popq %r8
+ popq %rax
+ popq %rsi /* skip rcx */
+ popq %rdx
+ popq %rsi
+ popq %rdi
+ movq RSP-ORIG_RAX(%rsp), %rsp
USERGS_SYSRET64
END(entry_SYSCALL_64)