From 9478f1927e6ef9ef5e1ad761af1c98aa8e40b7f5 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Tue, 3 Apr 2018 11:22:51 +0100 Subject: [PATCH] arm64: only advance singlestep for user instruction traps Our arm64_skip_faulting_instruction() helper advances the userspace singlestep state machine, but this is also called by the kernel BRK handler, as used for WARN*(). Thus, if we happen to hit a WARN*() while the user singlestep state machine is in the active-no-pending state, we'll advance to the active-pending state without having executed a user instruction, and will take a step exception earlier than expected when we return to userspace. Let's fix this by only advancing the state machine when skipping a user instruction. Signed-off-by: Mark Rutland Cc: Andrey Konovalov Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon --- arch/arm64/kernel/traps.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 1cb2749a72bf..8bbdc17e49df 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -277,7 +277,8 @@ void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size) * If we were single stepping, we want to get the step exception after * we return from the trap. */ - user_fastforward_single_step(current); + if (user_mode(regs)) + user_fastforward_single_step(current); } static LIST_HEAD(undef_hook); -- 2.30.2