Commit 802b9111 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Will Deacon
Browse files

arm64: kasan: do not instrument stacktrace.c 



Disable KASAN instrumentation of arch/arm64/kernel/stacktrace.c.

This speeds up Generic KASAN by 5-20%.

As a side-effect, KASAN is now unable to detect bugs in the stack trace
collection code. This is taken as an acceptable downside.

Also replace READ_ONCE_NOCHECK() with READ_ONCE() in stacktrace.c.
As the file is now not instrumented, there is no need to use the
NOCHECK version of READ_ONCE().

Suggested-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/c4c944a2a905e949760fbeb29258185087171708.1653317461.git.andreyknvl@google.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent a111daf0

arch/arm64/kernel/Makefile

+5 −0
Original line number Diff line number Diff line
@@ -14,6 +14,11 @@ CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE) 
CFLAGS_REMOVE_syscall.o	 = -fstack-protector -fstack-protector-strong

CFLAGS_syscall.o	+= -fno-stack-protector



# When KASAN is enabled, a stack trace is recorded for every alloc/free, which

# can significantly impact performance. Avoid instrumenting the stack trace

# collection code to minimize this impact.

KASAN_SANITIZE_stacktrace.o := n



# It's not safe to invoke KCOV when portions of the kernel environment aren't

# available or are out-of-sync with HW state. Since `noinstr` doesn't always

# inhibit KCOV instrumentation, disable it for the entire compilation unit.

arch/arm64/kernel/stacktrace.c

+2 −2
Original line number Diff line number Diff line
@@ -124,8 +124,8 @@ static int notrace unwind_next(struct task_struct *tsk, 
	 * Record this frame record's values and location. The prev_fp and

	 * prev_type are only meaningful to the next unwind_next() invocation.

	 */

	state->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));

	state->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));

	state->fp = READ_ONCE(*(unsigned long *)(fp));

	state->pc = READ_ONCE(*(unsigned long *)(fp + 8));

	state->prev_fp = fp;

	state->prev_type = info.type;