| From | Andi Kleen <> | Subject | [PATCH 48/74] x86, lto: Use inline assembler instead of global register variable to get sp | Date | Sat, 18 Aug 2012 19:56:44 -0700 |
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From: Andi Kleen <ak@linux.intel.com>
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 instead.
I verified this generates the same binary (on 64bit) as the original register variable.
Signed-off-by: Andi Kleen <ak@linux.intel.com> --- arch/x86/include/asm/thread_info.h | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index 89f794f..d9fbfa1 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -167,9 +167,11 @@ 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" : "=r" (sp)); \ + sp; \ +}) /* how to get the thread information struct from C */ static inline struct thread_info *current_thread_info(void) -- 1.7.7.6
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