[tip: x86/build] x86: Ignore stack unwinding in KCOV

[tip-bot2 for Dmitry Vyukov]

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

Commit-ID:     ae94b263f5f69c180347e795fbefa051b65aacc3
Gitweb:        https://git.kernel.org/tip/ae94b263f5f69c180347e795fbefa051b65aacc3
Author:        Dmitry Vyukov <dvyukov@xxxxxxxxxx>
AuthorDate:    Tue, 11 Jun 2024 09:50:33 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 08 Aug 2024 17:36:35 +02:00

x86: Ignore stack unwinding in KCOV

Stack unwinding produces large amounts of uninteresting coverage.
It's called from KASAN kmalloc/kfree hooks, fault injection, etc.
It's not particularly useful and is not a function of system call args.
Ignore that code.

Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/eaf54b8634970b73552dcd38bf9be6ef55238c10.1718092070.git.dvyukov@xxxxxxxxxx

---
 arch/x86/kernel/Makefile | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index a847180..f791898 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -35,6 +35,14 @@ KMSAN_SANITIZE_nmi.o					:= n
 # If instrumentation of the following files is enabled, boot hangs during
 # first second.
 KCOV_INSTRUMENT_head$(BITS).o				:= n
+# These are called from save_stack_trace() on debug paths,
+# and produce large amounts of uninteresting coverage.
+KCOV_INSTRUMENT_stacktrace.o				:= n
+KCOV_INSTRUMENT_dumpstack.o				:= n
+KCOV_INSTRUMENT_dumpstack_$(BITS).o			:= n
+KCOV_INSTRUMENT_unwind_orc.o				:= n
+KCOV_INSTRUMENT_unwind_frame.o				:= n
+KCOV_INSTRUMENT_unwind_guess.o				:= n
 
 CFLAGS_irq.o := -I $(src)/../include/asm/trace