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x86/int3: Avoid atomic instrumentation

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Use arch_atomic_*() and __READ_ONCE() 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>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135313.517429268@linutronix.de
This commit is contained in:
Peter Zijlstra 2020-01-24 22:08:45 +01:00 committed by Thomas Gleixner
parent 4979fb53ab
commit ef882bfef9
1 changed files with 3 additions and 3 deletions
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6
arch/x86/kernel/alternative.c
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@ -1014,9 +1014,9 @@ static struct bp_patching_desc *bp_desc;
static __always_inline static __always_inline
struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp) 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(*descp); /* rcu_dereference */
if (!desc || !atomic_inc_not_zero(&desc->refs)) if (!desc || !arch_atomic_inc_not_zero(&desc->refs))
return NULL; return NULL;
return desc; return desc;
@ -1025,7 +1025,7 @@ struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp)
static __always_inline void put_desc(struct bp_patching_desc *desc) static __always_inline void put_desc(struct bp_patching_desc *desc)
{ {
smp_mb__before_atomic(); 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) static __always_inline void *text_poke_addr(struct text_poke_loc *tp)