Messages in this thread Patch in this message | | | Date | Tue, 05 May 2020 15:49:28 +0200 | From | Thomas Gleixner <> | Subject | [patch V4 part 4 02/24] x86/int3: Avoid atomic instrumentation |
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From: Peter Zijlstra <peterz@infradead.org>
Use arch_atomic_*() and READ_ONCE_NOCHECK() to ensure nothing untoward creeps in and ruins things.
That is; this is the INT3 text poke handler, strictly limit the code that runs in it, lest it inadvertenly hits yet another INT3.
Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- arch/x86/kernel/alternative.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -960,9 +960,9 @@ static struct bp_patching_desc *bp_desc; static __always_inline struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp) { - struct bp_patching_desc *desc = READ_ONCE(*descp); /* rcu_dereference */ + struct bp_patching_desc *desc = READ_ONCE_NOCHECK(*descp); /* rcu_dereference */ - if (!desc || !atomic_inc_not_zero(&desc->refs)) + if (!desc || !arch_atomic_inc_not_zero(&desc->refs)) return NULL; return desc; @@ -971,7 +971,7 @@ struct bp_patching_desc *try_get_desc(st static __always_inline void put_desc(struct bp_patching_desc *desc) { smp_mb__before_atomic(); - atomic_dec(&desc->refs); + arch_atomic_dec(&desc->refs); } static __always_inline void *text_poke_addr(struct text_poke_loc *tp)
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