arm64: only advance singlestep for user instruction traps
authorMark Rutland <mark.rutland@arm.com>
Tue, 3 Apr 2018 10:22:51 +0000 (11:22 +0100)
committerWill Deacon <will.deacon@arm.com>
Tue, 24 Apr 2018 18:07:36 +0000 (19:07 +0100)
commit9478f1927e6ef9ef5e1ad761af1c98aa8e40b7f5
tree585789158e71ac5acce4a4f7146b803a26813e8b
parented231ae384fdfcb546b63b2fe7add65029e3a94c
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 <mark.rutland@arm.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
arch/arm64/kernel/traps.c