linux-kernel - [PATCH 6/9] x86/asm/entry/64: reuse stub epilogue by ret_from

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Date:	Thu,  2 Apr 2015 16:36:15 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 6/9] x86/asm/entry/64: reuse stub epilogue by ret_from_fork

ret_from_fork can reuse epilogue at return_from_stub.

Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Ingo Molnar <mingo@...nel.org>
CC: Borislav Petkov <bp@...en8.de>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: Alexei Starovoitov <ast@...mgrid.com>
CC: Will Drewry <wad@...omium.org>
CC: Kees Cook <keescook@...omium.org>
CC: x86@...nel.org
CC: linux-kernel@...r.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

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