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authorPeter Zijlstra <peterz@infradead.org>2015-08-12 21:04:22 +0200
committerAlex Shi <alex.shi@linaro.org>2016-06-24 21:31:55 +0800
commit46cb70a50bf3b16526dde781197b194f2be84977 (patch)
treed93b67352d69ec980ce4feca4e3ce700c992c20c
parent44069b0826b6f76a8601ad880b10557c7e4968c9 (diff)
downloadlinux-linaro-stable-v4.1/topic/writeback-cg.tar.gz
jump_label/x86: Work around asm build bug on older/backported GCCsv4.1/topic/writeback-cg
Boris reported that gcc version 4.4.4 20100503 (Red Hat 4.4.4-2) fails to build linux-next kernels that have this fresh commit via the locking tree: 11276d5306b8 ("locking/static_keys: Add a new static_key interface") The problem appears to be that even though @key and @branch are compile time constants, it doesn't see the following expression as an immediate value: &((char *)key)[branch] More recent GCCs don't appear to have this problem. In particular, Red Hat backported the 'asm goto' feature into 4.4, 'normal' 4.4 compilers will not have this feature and thus not run into this asm. The workaround is to supply both values to the asm as immediates and do the addition in asm. Suggested-by: H. Peter Anvin <hpa@zytor.com> Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> (cherry picked from commit d420acd816c07c7be31bd19d09cbcb16e5572fa6) Signed-off-by: Alex Shi <alex.shi@linaro.org>
-rw-r--r--arch/x86/include/asm/jump_label.h8
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 28d7a85..5daeca3 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -22,9 +22,9 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
".pushsection __jump_table, \"aw\" \n\t"
_ASM_ALIGN "\n\t"
- _ASM_PTR "1b, %l[l_yes], %c0 \n\t"
+ _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
".popsection \n\t"
- : : "i" (&((char *)key)[branch]) : : l_yes);
+ : : "i" (key), "i" (branch) : : l_yes);
return false;
l_yes:
@@ -38,9 +38,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
"2:\n\t"
".pushsection __jump_table, \"aw\" \n\t"
_ASM_ALIGN "\n\t"
- _ASM_PTR "1b, %l[l_yes], %c0 \n\t"
+ _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
".popsection \n\t"
- : : "i" (&((char *)key)[branch]) : : l_yes);
+ : : "i" (key), "i" (branch) : : l_yes);
return false;
l_yes: