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arm64: kasan: do not instrument stacktrace.c

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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: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/c4c944a2a905e949760fbeb29258185087171708.1653317461.git.andreyknvl@google.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Andrey Konovalov 2022-05-23 16:51:51 +02:00 committed by Will Deacon
parent a111daf0c5
commit 802b91118d
2 changed files with 7 additions and 2 deletions
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5
arch/arm64/kernel/Makefile
View File

@ -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.

4
arch/arm64/kernel/stacktrace.c
View File

@ -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;