[PATCH] arm: LLVMLinux: Calculate current_thread_info from fp

[behanw at converseincode.com]

From: Behan Webster <behanw at converseincode.com>

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

Signed-off-by: Mark Charlebois <charlebm at gmail.com>
Signed-off-by: Behan Webster <behanw at converseincode.com>
Reviewed-by: Jan-Simon Möller <dl9pf at gmx.de>
---
 arch/arm/include/asm/thread_info.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index df5e13d..cb50933 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -106,8 +106,9 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__;
 
 static inline struct thread_info *current_thread_info(void)
 {
-	register unsigned long sp asm ("sp");
-	return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
+	return (struct thread_info *)
+		((u32)(__builtin_frame_address(0))
+		& ~(THREAD_SIZE - 1));
 }
 
 #define thread_saved_pc(tsk)	\
-- 
1.8.1.2