lkml.org 
[lkml]   [2020]   [May]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[patch V4 part 4 02/24] x86/int3: Avoid atomic instrumentation
    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)
    \
     
     \ /
      Last update: 2020-05-05 16:20    [W:4.154 / U:0.228 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site