linux-kernel - [tip:x86/debug] x86/uaccess: Add stack frame output operand in get

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Date:	Tue, 23 Feb 2016 01:02:14 -0800
From:	tip-bot for Chris J Arges <tipbot@...or.com>@zytor.com
To:	linux-tip-commits@...r.kernel.org@...or.com
Cc:	tglx@...utronix.de, palves@...hat.com, brgerst@...il.com,
	acme@...nel.org, akpm@...ux-foundation.org, peterz@...radead.org,
	mmarek@...e.cz, bernd@...rovitsch.priv.at, bp@...e.de,
	jslaby@...e.cz, luto@...nel.org, jpoimboe@...hat.com,
	luto@...capital.net, chris.j.arges@...onical.com,
	namhyung@...il.com, torvalds@...ux-foundation.org,
	mingo@...nel.org, linux-kernel@...r.kernel.org, hpa@...or.com,
	bp@...en8.de, dvlasenk@...hat.com
Subject: [tip:x86/debug] x86/uaccess: Add stack frame output operand in get_user() inline asm

Commit-ID:  5e947b38f8ead33bf6aaecc2af20a0a3a988fd02
Gitweb:     http://git.kernel.org/tip/5e947b38f8ead33bf6aaecc2af20a0a3a988fd02
Author:     Chris J Arges <chris.j.arges@...onical.com>
AuthorDate: Thu, 21 Jan 2016 16:49:25 -0600
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 23 Feb 2016 09:03:58 +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@...onical.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Reviewed-by: Borislav Petkov <bp@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Bernd Petrovitsch <bernd@...rovitsch.priv.at>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Jiri Slaby <jslaby@...e.cz>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michal Marek <mmarek@...e.cz>
Cc: Namhyung Kim <namhyung@...il.com>
Cc: Pedro Alves <palves@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: live-patching@...r.kernel.org
Link: http://lkml.kernel.org/r/bc85501f221ee512670797c7f110022e64b12c81.1453405861.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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);					\