linux-kernel - [PATCH 1/3] x86/uaccess: Add stack frame output operand in get

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Date:	Thu, 17 Sep 2015 17:14:35 -0500
From:	Chris J Arges <chris.j.arges@...onical.com>
To:	x86@...nel.org, jpoimboe@...hat.com, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com
Cc:	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	mmarek@...e.cz, peterz@...radead.org, luto@...nel.org,
	bp@...en8.de, torvalds@...ux-foundation.org, andi@...stfloor.org,
	palves@...hat.com, namhyung@...il.com, bernd@...rovitsch.priv.at,
	akpm@...ux-foundation.org, konrad.wilk@...cle.com,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	jeremy@...p.org, chrisw@...s-sol.org, akataria@...are.com,
	rusty@...tcorp.com.au, herbert@...dor.apana.org.au,
	davem@...emloft.net, pavel@....cz, rjw@...ysocki.net,
	len.brown@...el.com, matt.fleming@...el.com,
	Chris J Arges <chris.j.arges@...onical.com>,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	"Michael S. Tsirkin" <mst@...hat.com>
Subject: [PATCH 1/3] 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>
---
 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;							\
-- 
1.9.1

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