Commit dff38e3e authored Oct 22, 2013 by Andi Kleen Committed by H. Peter Anvin Jan 29, 2014

x86: Use inline assembler instead of global register variable to get sp



LTO in gcc 4.6/47. has trouble with global register variables. They were used
to read the stack pointer. Use a simple inline assembler statement with
a mov instead.

This also helps LLVM/clang, which does not support global register
variables.

[ hpa: Ideally this should become a builtin in both gcc and clang. ]

v2: More general asm constraint. Fix description (Jan Beulich)

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1382458079-24450-6-git-send-email-andi@firstfloor.org


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

parent a2e7f0e3

arch/x86/include/asm/thread_info.h

+5 −3

Original line number	Diff line number	Diff line
		@@ -163,9 +163,11 @@ struct thread_info {
		*/
		#ifndef __ASSEMBLY__


		/* how to get the current stack pointer from C */
		register unsigned long current_stack_pointer asm("esp") __used;
		#define current_stack_pointer ({ \
		unsigned long sp; \
		asm("mov %%esp,%0" : "=g" (sp)); \
		sp; \
		})

		/* how to get the thread information struct from C */
		static inline struct thread_info *current_thread_info(void)