[tip:x86/debug] x86/uaccess: Add stack frame output operand in get_user() inline asm

[tip-bot for Chris J Arges]

Commit-ID:  f05058c4d652b619adfda6c78d8f5b341169c264
Gitweb:     http://git.kernel.org/tip/f05058c4d652b619adfda6c78d8f5b341169c264
Author:     Chris J Arges <chris.j.arges@xxxxxxxxxxxxx>
AuthorDate: Thu, 21 Jan 2016 16:49:25 -0600
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 24 Feb 2016 08:35:43 +0100

x86/uaccess: Add stack frame output operand in get_user() inline asm

Numerous 'call without frame pointer save/setup' warnings are introduced
by stacktool because of functions using the get_user() macro. Bad stack
traces could occur due to lack of or misplacement of stack frame setup
code.

This patch forces a stack frame to be created before the inline asm code
if CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an
output operand for the get_user() inline assembly statement.

Signed-off-by: Chris J Arges <chris.j.arges@xxxxxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Bernd Petrovitsch <bernd@xxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Marek <mmarek@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxx>
Cc: Pedro Alves <palves@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: live-patching@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/bc85501f221ee512670797c7f110022e64b12c81.1453405861.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/include/asm/uaccess.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a4a30e4..9bbb3b2 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -179,10 +179,11 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
 ({									\
 	int __ret_gu;							\
 	register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);		\
+	register void *__sp asm(_ASM_SP);				\
 	__chk_user_ptr(ptr);						\
 	might_fault();							\
-	asm volatile("call __get_user_%P3"				\
-		     : "=a" (__ret_gu), "=r" (__val_gu)			\
+	asm volatile("call __get_user_%P4"				\
+		     : "=a" (__ret_gu), "=r" (__val_gu), "+r" (__sp)	\
 		     : "0" (ptr), "i" (sizeof(*(ptr))));		\
 	(x) = (__force __typeof__(*(ptr))) __val_gu;			\
 	__builtin_expect(__ret_gu, 0);					\