[PATCH 6/9] x86/asm/entry/64: reuse stub epilogue by ret_from_fork

[Denys Vlasenko <dvlasenk@redhat.com>]

ret_from_fork can reuse epilogue at return_from_stub.

Run-tested.

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 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index e8f2aeb..c4304e2 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -428,6 +428,7 @@ return_from_exec:
 	ret
 return_from_stub:
 	addq $8, %rsp
+save_rax_and_restore_extra:
 	movq %rax,RAX(%rsp)
 	RESTORE_EXTRA_REGS
 	jmp int_ret_from_sys_call
@@ -525,9 +526,8 @@ ENTRY(ret_from_fork)
 1:
 	movq %rbp, %rdi
 	call *%rbx
-	movl $0, RAX(%rsp)
-	RESTORE_EXTRA_REGS
-	jmp int_ret_from_sys_call
+	xorl	%eax, %eax
+	jmp	save_rax_and_restore_extra
 	CFI_ENDPROC
 END(ret_from_fork)
 
-- 
1.8.1.4