lkml.org 
[lkml]   [2018]   [Aug]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    Subject[PATCH v3 1/7] x86: refactor kprobes_fault() like kprobe_exceptions_notify()
    From
    This is an extension of commit b506a9d08bae ("x86: code clarification patch
    to Kprobes arch code"). As that commit explains, even though
    kprobe_running() can't be called with preemption enabled, you don't have to
    disable preemption - if preemption is on, you can't be in a kprobe.

    Also, use X86_TRAP_PF instead of 14.

    Signed-off-by: Jann Horn <jannh@google.com>
    ---
    v3:
    - avoid unnecessary branch on return value and split up the checks
    (Borislav Petkov)

    arch/x86/mm/fault.c | 24 +++++++++++++-----------
    1 file changed, 13 insertions(+), 11 deletions(-)

    diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
    index b9123c497e0a..bcdaae1d5bf5 100644
    --- a/arch/x86/mm/fault.c
    +++ b/arch/x86/mm/fault.c
    @@ -44,17 +44,19 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr)

    static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
    {
    - int ret = 0;
    -
    - /* kprobe_running() needs smp_processor_id() */
    - if (kprobes_built_in() && !user_mode(regs)) {
    - preempt_disable();
    - if (kprobe_running() && kprobe_fault_handler(regs, 14))
    - ret = 1;
    - preempt_enable();
    - }
    -
    - return ret;
    + if (!kprobes_built_in())
    + return 0;
    + if (user_mode(regs))
    + return 0;
    + /*
    + * To be potentially processing a kprobe fault and to be allowed to call
    + * kprobe_running(), we have to be non-preemptible.
    + */
    + if (preemptible())
    + return 0;
    + if (!kprobe_running())
    + return 0;
    + return kprobe_fault_handler(regs, X86_TRAP_PF);
    }

    /*
    --
    2.19.0.rc0.228.g281dcd1b4d0-goog
    \
     
     \ /
      Last update: 2018-08-28 22:16    [W:2.786 / U:0.256 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site