linux-kernel - [PATCH 1/7] x86/vdso32: Separate sigreturn code

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Date:	Sat, 29 Aug 2015 11:20:20 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 1/7] x86/vdso32: Separate sigreturn code

Compile a separate sigreturn.o instead of including it in the three
syscall entry stub files.  Use alternatives to patch in a syscall
instruction when supported.

Signed-off-by: Brian Gerst <brgerst@...il.com>
---
 arch/x86/entry/vdso/Makefile           | 3 ++-
 arch/x86/entry/vdso/vdso32/int80.S     | 5 +----
 arch/x86/entry/vdso/vdso32/sigreturn.S | 9 +++++++--
 arch/x86/entry/vdso/vdso32/syscall.S   | 7 +------
 arch/x86/entry/vdso/vdso32/sysenter.S  | 5 +----
 5 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index a3d0767..b4cd431 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -140,7 +140,7 @@ override obj-dirs = $(dir $(obj)) $(obj)/vdso32/
 
 targets += vdso32/vdso32.lds
 targets += vdso32/note.o vdso32/vclock_gettime.o $(vdso32.so-y:%=vdso32/%.o)
-targets += vdso32/vclock_gettime.o
+targets += vdso32/vclock_gettime.o vdso32/sigreturn.o
 
 $(obj)/vdso32.o: $(vdso32-images:%=$(obj)/%)
 
@@ -163,6 +163,7 @@ $(vdso32-images:%=$(obj)/%.dbg): $(obj)/vdso32-%.so.dbg: FORCE \
 				 $(obj)/vdso32/vdso32.lds \
 				 $(obj)/vdso32/vclock_gettime.o \
 				 $(obj)/vdso32/note.o \
+				 $(obj)/vdso32/sigreturn.o \
 				 $(obj)/vdso32/%.o
 	$(call if_changed,vdso)
 
diff --git a/arch/x86/entry/vdso/vdso32/int80.S b/arch/x86/entry/vdso/vdso32/int80.S
index b15b7c0..e40af1c 100644
--- a/arch/x86/entry/vdso/vdso32/int80.S
+++ b/arch/x86/entry/vdso/vdso32/int80.S
@@ -1,10 +1,7 @@
 /*
  * Code for the vDSO.  This version uses the old int $0x80 method.
- *
- * First get the common code for the sigreturn entry points.
- * This must come first.
  */
-#include "sigreturn.S"
+#include <linux/linkage.h>
 
 	.text
 	.globl __kernel_vsyscall
diff --git a/arch/x86/entry/vdso/vdso32/sigreturn.S b/arch/x86/entry/vdso/vdso32/sigreturn.S
index d7ec4e2..ca0e6ca 100644
--- a/arch/x86/entry/vdso/vdso32/sigreturn.S
+++ b/arch/x86/entry/vdso/vdso32/sigreturn.S
@@ -9,9 +9,14 @@
 #include <linux/linkage.h>
 #include <asm/unistd_32.h>
 #include <asm/asm-offsets.h>
+#include <asm/alternative-asm.h>
+#include <asm/cpufeature.h>
 
-#ifndef SYSCALL_ENTER_KERNEL
-#define	SYSCALL_ENTER_KERNEL	int $0x80
+#ifdef CONFIG_COMPAT
+#define SYSCALL_ENTER_KERNEL \
+	ALTERNATIVE "int $0x80", "syscall", X86_FEATURE_SYSCALL32
+#else
+#define SYSCALL_ENTER_KERNEL int $0x80
 #endif
 
 	.text
diff --git a/arch/x86/entry/vdso/vdso32/syscall.S b/arch/x86/entry/vdso/vdso32/syscall.S
index 6b286bb..75545ec 100644
--- a/arch/x86/entry/vdso/vdso32/syscall.S
+++ b/arch/x86/entry/vdso/vdso32/syscall.S
@@ -1,12 +1,7 @@
 /*
  * Code for the vDSO.  This version uses the syscall instruction.
- *
- * First get the common code for the sigreturn entry points.
- * This must come first.
  */
-#define SYSCALL_ENTER_KERNEL	syscall
-#include "sigreturn.S"
-
+#include <linux/linkage.h>
 #include <asm/segment.h>
 
 	.text
diff --git a/arch/x86/entry/vdso/vdso32/sysenter.S b/arch/x86/entry/vdso/vdso32/sysenter.S
index e354bce..e99c7699 100644
--- a/arch/x86/entry/vdso/vdso32/sysenter.S
+++ b/arch/x86/entry/vdso/vdso32/sysenter.S
@@ -1,10 +1,7 @@
 /*
  * Code for the vDSO.  This version uses the sysenter instruction.
- *
- * First get the common code for the sigreturn entry points.
- * This must come first.
  */
-#include "sigreturn.S"
+#include <linux/linkage.h>
 
 /*
  * The caller puts arg2 in %ecx, which gets pushed. The kernel will use
-- 
2.4.3

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