linux-kernel - [PATCH v13 22/23] x86/uaccess: Add stack frame output operand in get

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Message-Id: <6a3db544faf798cea606230f329678e48c51c461.1442935712.git.jpoimboe@redhat.com>
Date:	Tue, 22 Sep 2015 10:47:13 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:	Chris J Arges <chris.j.arges@...onical.com>,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v13 22/23] x86/uaccess: Add stack frame output operand in get_user inline asm

From: Chris J Arges <chris.j.arges@...onical.com>

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>
---
 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 a8df874..55b8db5 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -176,10 +176,11 @@ __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;			\
 	__ret_gu;							\
-- 
2.4.3

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