Messages in this thread Patch in this message |  | | Date | Mon, 27 Aug 2018 20:56:25 +0200 | Subject | [PATCH v2 1/7] x86: refactor kprobes_fault() like kprobe_exceptions_notify() | From | Jann Horn <> |
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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> --- arch/x86/mm/fault.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index b9123c497e0a..2254a30533b9 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -44,17 +44,14 @@ 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; + /* + * To be potentially processing a kprobe fault and to be allowed to call + * kprobe_running(), we have to be non-preemptible. + */ + if (kprobes_built_in() && !user_mode(regs) && !preemptible() && + kprobe_running() && kprobe_fault_handler(regs, X86_TRAP_PF)) + return 1; + return 0; } /* -- 2.19.0.rc0.228.g281dcd1b4d0-goog
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