compiler/gcc4: Add quirk for 'asm goto' miscompilation bug

Fengguang Wu, Oleg Nesterov and Peter Zijlstra tracked down
a kernel crash to a GCC bug: GCC miscompiles certain 'asm goto'
constructs, as outlined here:

  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670

Implement a workaround suggested by Jakub Jelinek.

Reported-and-tested-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Suggested-by: Jakub Jelinek <jakub@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index d3f5c63078d8..89270b4318db 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -374,7 +374,7 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
                  * Catch too early usage of this before alternatives
                  * have run.
                  */
-                asm goto("1: jmp %l[t_warn]\n"
+                asm_volatile_goto("1: jmp %l[t_warn]\n"
                          "2:\n"
                          ".section .altinstructions,\"a\"\n"
                          " .long 1b - .\n"
@@ -388,7 +388,7 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
 
 #endif
 
-                asm goto("1: jmp %l[t_no]\n"
+                asm_volatile_goto("1: jmp %l[t_no]\n"
                          "2:\n"
                          ".section .altinstructions,\"a\"\n"
                          " .long 1b - .\n"
@@ -453,7 +453,7 @@ static __always_inline __pure bool _static_cpu_has_safe(u16 bit)
  * have. Thus, we force the jump to the widest, 4-byte, signed relative
  * offset even though the last would often fit in less bytes.
  */
-                asm goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
+                asm_volatile_goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
                          "2:\n"
                          ".section .altinstructions,\"a\"\n"
                          " .long 1b - .\n"              /* src offset */