lkml.org 
[lkml]   [2015]   [Apr]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
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@redhat.com>
AuthorDate: Tue, 7 Apr 2015 22:43:44 +0200
Committer: Ingo Molnar <mingo@kernel.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@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1428439424-7258-8-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.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

\
 
 \ /
  Last update: 2015-04-09 11:41    [W:0.119 / U:0.824 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site