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>
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Ingo Molnar
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3f0116c323
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@ -16,7 +16,7 @@
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static __always_inline bool arch_static_branch(struct static_key *key)
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{
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asm goto("1:\n\t"
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asm_volatile_goto("1:\n\t"
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JUMP_LABEL_NOP "\n\t"
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".pushsection __jump_table, \"aw\"\n\t"
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".word 1b, %l[l_yes], %c0\n\t"
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@ -22,7 +22,7 @@
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static __always_inline bool arch_static_branch(struct static_key *key)
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{
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asm goto("1:\tnop\n\t"
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asm_volatile_goto("1:\tnop\n\t"
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"nop\n\t"
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".pushsection __jump_table, \"aw\"\n\t"
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WORD_INSN " 1b, %l[l_yes], %0\n\t"
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@ -19,7 +19,7 @@
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static __always_inline bool arch_static_branch(struct static_key *key)
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{
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asm goto("1:\n\t"
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asm_volatile_goto("1:\n\t"
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"nop\n\t"
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".pushsection __jump_table, \"aw\"\n\t"
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JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
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@ -15,7 +15,7 @@
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static __always_inline bool arch_static_branch(struct static_key *key)
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{
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asm goto("0: brcl 0,0\n"
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asm_volatile_goto("0: brcl 0,0\n"
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".pushsection __jump_table, \"aw\"\n"
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ASM_ALIGN "\n"
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ASM_PTR " 0b, %l[label], %0\n"
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@ -9,7 +9,7 @@
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static __always_inline bool arch_static_branch(struct static_key *key)
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{
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asm goto("1:\n\t"
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asm_volatile_goto("1:\n\t"
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"nop\n\t"
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"nop\n\t"
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".pushsection __jump_table, \"aw\"\n\t"
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@ -374,7 +374,7 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
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* Catch too early usage of this before alternatives
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* have run.
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*/
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asm goto("1: jmp %l[t_warn]\n"
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asm_volatile_goto("1: jmp %l[t_warn]\n"
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"2:\n"
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".section .altinstructions,\"a\"\n"
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" .long 1b - .\n"
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@ -388,7 +388,7 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
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#endif
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asm goto("1: jmp %l[t_no]\n"
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asm_volatile_goto("1: jmp %l[t_no]\n"
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"2:\n"
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".section .altinstructions,\"a\"\n"
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" .long 1b - .\n"
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@ -453,7 +453,7 @@ static __always_inline __pure bool _static_cpu_has_safe(u16 bit)
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* have. Thus, we force the jump to the widest, 4-byte, signed relative
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* offset even though the last would often fit in less bytes.
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*/
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asm goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
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asm_volatile_goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
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"2:\n"
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".section .altinstructions,\"a\"\n"
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" .long 1b - .\n" /* src offset */
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@ -18,7 +18,7 @@
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static __always_inline bool arch_static_branch(struct static_key *key)
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{
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asm goto("1:"
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asm_volatile_goto("1:"
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".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
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".pushsection __jump_table, \"aw\" \n\t"
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_ASM_ALIGN "\n\t"
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@ -20,7 +20,7 @@
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static inline void __mutex_fastpath_lock(atomic_t *v,
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void (*fail_fn)(atomic_t *))
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{
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asm volatile goto(LOCK_PREFIX " decl %0\n"
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asm_volatile_goto(LOCK_PREFIX " decl %0\n"
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" jns %l[exit]\n"
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: : "m" (v->counter)
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: "memory", "cc"
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@ -75,7 +75,7 @@ static inline int __mutex_fastpath_lock_retval(atomic_t *count)
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static inline void __mutex_fastpath_unlock(atomic_t *v,
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void (*fail_fn)(atomic_t *))
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{
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asm volatile goto(LOCK_PREFIX " incl %0\n"
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asm_volatile_goto(LOCK_PREFIX " incl %0\n"
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" jg %l[exit]\n"
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: : "m" (v->counter)
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: "memory", "cc"
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@ -65,6 +65,21 @@
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#define __visible __attribute__((externally_visible))
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#endif
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/*
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* GCC 'asm goto' miscompiles certain code sequences:
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*
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* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
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*
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* Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
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* Fixed in GCC 4.8.2 and later versions.
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*
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* (asm goto is automatically volatile - the naming reflects this.)
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*/
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#if GCC_VERSION <= 40801
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# define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
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#else
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# define asm_volatile_goto(x...) do { asm goto(x); } while (0)
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#endif
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#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
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#if GCC_VERSION >= 40400
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