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

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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>
This commit is contained in:
Andi Kleen 2013-10-22 09:07:57 -07:00 committed by H. Peter Anvin
parent a2e7f0e3a4
commit dff38e3e93
1 changed files with 5 additions and 3 deletions
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8
arch/x86/include/asm/thread_info.h
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@ -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)