[PATCH v2 3/8] x86/debug: Move kprobe_debug_handler() into exc_debug_kernel()

From: Peter Zijlstra
Date: Fri Aug 21 2020 - 06:21:56 EST


Kprobes are on kernel text, and thus only matter for #DB-from-kernel.
Kprobes are ordered before the generic notifier, preserve that order.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/include/asm/kprobes.h | 4 ++++
arch/x86/kernel/traps.c | 10 ++++------
2 files changed, 8 insertions(+), 6 deletions(-)

--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -106,5 +106,9 @@ extern int kprobe_exceptions_notify(stru
extern int kprobe_int3_handler(struct pt_regs *regs);
extern int kprobe_debug_handler(struct pt_regs *regs);

+#else
+
+static inline int kprobe_debug_handler(struct pt_regs *regs) { return 0; }
+
#endif /* CONFIG_KPROBES */
#endif /* _ASM_X86_KPROBES_H */
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -806,12 +806,6 @@ static void handle_debug(struct pt_regs
/* Store the virtualized DR6 value */
tsk->thread.debugreg6 = dr6;

-#ifdef CONFIG_KPROBES
- if (kprobe_debug_handler(regs)) {
- return;
- }
-#endif
-
if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0,
SIGTRAP) == NOTIFY_STOP) {
return;
@@ -877,8 +871,12 @@ static __always_inline void exc_debug_ke
if ((dr6 & DR_STEP) && is_sysenter_singlestep(regs))
dr6 &= ~DR_STEP;

+ if (kprobe_debug_handler(regs))
+ goto out;
+
handle_debug(regs, dr6, false);

+out:
instrumentation_end();
idtentry_exit_nmi(regs, irq_state);