linux-kernel - [PATCH 1/9] x86/asm/entry/64: reuse stub return code

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Date:	Thu,  2 Apr 2015 16:36:10 +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 1/9] x86/asm/entry/64: reuse stub return code

Various flavors of stub_{sigreturn,execve}, six functions in total,
repeat

    movq %rax,RAX(%rsp)
    RESTORE_EXTRA_REGS
    jmp int_ret_from_sys_call

sequence. RESTORE_EXTRA_REGS is six 5-byte insns.

Reuse this code.

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 | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 13185c5..765436c 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -423,6 +423,7 @@ ENTRY(stub_execve)
 	DEFAULT_FRAME 0
 	SAVE_EXTRA_REGS
 	call sys_execve
+return_from_stub:
 	movq %rax,RAX(%rsp)
 	RESTORE_EXTRA_REGS
 	jmp int_ret_from_sys_call
@@ -435,9 +436,7 @@ ENTRY(stub_execveat)
 	DEFAULT_FRAME 0
 	SAVE_EXTRA_REGS
 	call sys_execveat
-	movq %rax,RAX(%rsp)
-	RESTORE_EXTRA_REGS
-	jmp int_ret_from_sys_call
+	jmp  return_from_stub
 	CFI_ENDPROC
 END(stub_execveat)
 
@@ -451,9 +450,7 @@ ENTRY(stub_rt_sigreturn)
 	DEFAULT_FRAME 0
 	SAVE_EXTRA_REGS
 	call sys_rt_sigreturn
-	movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
-	RESTORE_EXTRA_REGS
-	jmp int_ret_from_sys_call
+	jmp  return_from_stub
 	CFI_ENDPROC
 END(stub_rt_sigreturn)
 
@@ -464,9 +461,7 @@ ENTRY(stub_x32_rt_sigreturn)
 	DEFAULT_FRAME 0
 	SAVE_EXTRA_REGS
 	call sys32_x32_rt_sigreturn
-	movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
-	RESTORE_EXTRA_REGS
-	jmp int_ret_from_sys_call
+	jmp  return_from_stub
 	CFI_ENDPROC
 END(stub_x32_rt_sigreturn)
 
@@ -476,9 +471,7 @@ ENTRY(stub_x32_execve)
 	DEFAULT_FRAME 0
 	SAVE_EXTRA_REGS
 	call compat_sys_execve
-	movq %rax,RAX(%rsp)
-	RESTORE_EXTRA_REGS
-	jmp int_ret_from_sys_call
+	jmp  return_from_stub
 	CFI_ENDPROC
 END(stub_x32_execve)
 
@@ -488,9 +481,7 @@ ENTRY(stub_x32_execveat)
 	DEFAULT_FRAME 0
 	SAVE_EXTRA_REGS
 	call compat_sys_execveat
-	movq %rax,RAX(%rsp)
-	RESTORE_EXTRA_REGS
-	jmp int_ret_from_sys_call
+	jmp  return_from_stub
 	CFI_ENDPROC
 END(stub_x32_execveat)
 
-- 
1.8.1.4

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