linux-kernel - [tip:x86/asm] x86/asm/entry/64: Reduce padding in execve stubs

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Date:	Thu, 9 Apr 2015 02:04:07 -0700
From:	tip-bot for Denys Vlasenko <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	oleg@...hat.com, torvalds@...ux-foundation.org, tglx@...utronix.de,
	brgerst@...il.com, wad@...omium.org, luto@...capital.net,
	linux-kernel@...r.kernel.org, keescook@...omium.org,
	dvlasenk@...hat.com, ast@...mgrid.com, mingo@...nel.org,
	bp@...en8.de, rostedt@...dmis.org, fweisbec@...il.com,
	hpa@...or.com
Subject: [tip:x86/asm] x86/asm/entry/64: Reduce padding in execve stubs

Commit-ID:  a37f34a325d90856314ccd4994e1070dcc6bdcc4
Gitweb:     http://git.kernel.org/tip/a37f34a325d90856314ccd4994e1070dcc6bdcc4
Author:     Denys Vlasenko <dvlasenk@...hat.com>
AuthorDate: Tue, 7 Apr 2015 22:43:44 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 9 Apr 2015 10:31:26 +0200

x86/asm/entry/64: Reduce padding in execve stubs

execve stubs are 7 bytes only. Padding them to 16 bytes is a
waste.

   text	   data	    bss	    dec	    hex	filename
  12594	      0	      0	  12594	   3132	entry_64.o.before
  12530	      0	      0	  12530	   30f2	entry_64.o

Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Drewry <wad@...omium.org>
Link: http://lkml.kernel.org/r/1428439424-7258-8-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/entry_64.S | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index b67f2fc..c7b2384 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -511,8 +511,12 @@ return_from_execve:
 	jmp	int_ret_from_sys_call
 	CFI_ENDPROC
 END(stub_execve)
-
-ENTRY(stub_execveat)
+/*
+ * Remaining execve stubs are only 7 bytes long.
+ * ENTRY() often aligns to 16 bytes, which in this case has no benefits.
+ */
+	.align	8
+GLOBAL(stub_execveat)
 	CFI_STARTPROC
 	DEFAULT_FRAME 0, 8
 	call	sys_execveat
@@ -521,14 +525,16 @@ ENTRY(stub_execveat)
 END(stub_execveat)
 
 #ifdef CONFIG_X86_X32_ABI
-ENTRY(stub_x32_execve)
+	.align	8
+GLOBAL(stub_x32_execve)
 	CFI_STARTPROC
 	DEFAULT_FRAME 0, 8
 	call	compat_sys_execve
 	jmp	return_from_execve
 	CFI_ENDPROC
 END(stub_x32_execve)
-ENTRY(stub_x32_execveat)
+	.align	8
+GLOBAL(stub_x32_execveat)
 	CFI_STARTPROC
 	DEFAULT_FRAME 0, 8
 	call	compat_sys_execveat
@@ -538,13 +544,15 @@ END(stub_x32_execveat)
 #endif
 
 #ifdef CONFIG_IA32_EMULATION
-ENTRY(stub32_execve)
+	.align	8
+GLOBAL(stub32_execve)
 	CFI_STARTPROC
 	call	compat_sys_execve
 	jmp	return_from_execve
 	CFI_ENDPROC
 END(stub32_execve)
-ENTRY(stub32_execveat)
+	.align	8
+GLOBAL(stub32_execveat)
 	CFI_STARTPROC
 	call	compat_sys_execveat
 	jmp	return_from_execve
--
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