linux-kernel - [PATCH] arm: LLVMLinux: Calculate pt

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Date:	Fri,  6 Sep 2013 17:42:41 -0400
From:	behanw@...verseincode.com
To:	linux@....linux.org.uk
Cc:	behanw@...verseincode.com, Mark Charlebois <charlebm@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Jones <davej@...hat.com>,
	linux-arm-kernel@...ts.infradead.org (moderated list:ARM PORT),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] arm: LLVMLinux: Calculate pt_regs address from fp

From: Behan Webster <behanw@...verseincode.com>

Use the frame pointer to calculate the end of the stack for current_pt_regs()
The existing code uses the stack pointer to do this calculation.
Using the frame pointer yeilds the same value in a more portable way.
This change supports being able to compile the kernel with gcc and clang.

Signed-off-by: Mark Charlebois <charlebm@...il.com>
Signed-off-by: Behan Webster <behanw@...verseincode.com>
Reviewed-by: Jan-Simon Möller <dl9pf@....de>
---
 arch/arm/include/asm/ptrace.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index 04c99f3..8aec2db 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -138,9 +138,9 @@ static inline unsigned long user_stack_pointer(struct pt_regs *regs)
 	return regs->ARM_sp;
 }
 
-#define current_pt_regs(void) ({				\
-	register unsigned long sp asm ("sp");			\
-	(struct pt_regs *)((sp | (THREAD_SIZE - 1)) - 7) - 1;	\
+#define current_pt_regs(void) ({					\
+	(struct pt_regs *)(((unsigned long)(__builtin_frame_address(0))	\
+		| (THREAD_SIZE - 1)) - 7) - 1;				\
 })
 
 #endif /* __ASSEMBLY__ */
-- 
1.8.1.2

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