[tip: x86/entry] x86/debug: Move kprobe_debug_handler() into exc_debug_kernel()

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     20a6e35a948284b8ab246ed35eefc56d674ad076
Gitweb:        https://git.kernel.org/tip/20a6e35a948284b8ab246ed35eefc56d674ad076
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Wed, 02 Sep 2020 15:25:53 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Fri, 04 Sep 2020 15:12:52 +02:00

x86/debug: Move kprobe_debug_handler() into exc_debug_kernel()

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>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200902133200.847465360@xxxxxxxxxxxxx

---
 arch/x86/include/asm/kprobes.h |  4 ++++
 arch/x86/kernel/traps.c        | 10 ++++------
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index 143bc9a..991a7ad 100644
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -106,5 +106,9 @@ extern int kprobe_exceptions_notify(struct notifier_block *self,
 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 */
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9945642..9cb39d3 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -806,12 +806,6 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user)
 	/* 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_kernel(struct pt_regs *regs,
 	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);