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Subject[PATCH v2 1/7] x86: refactor kprobes_fault() like kprobe_exceptions_notify()
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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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