[PATCH 3/8] riscv: stacktrace: disable KASAN instrumentation for stacktrace.o

[Wang Han]

KASAN records stack traces for every alloc/free, which means it walks
the unwinder very frequently. Instrumenting the stack trace collection
code itself adds substantial overhead and makes the traces themselves
noisier.

Mark stacktrace.o as not KASAN-instrumented, matching the arm, arm64
and x86 treatment of their stack unwinding code. This is a prerequisite
preference for the upcoming reliable unwinder, but the change is valid
on its own.

Signed-off-by: Wang Han <wanghan@xxxxxxxxxxxxxxxxx>
---
 arch/riscv/kernel/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index cabb99cadfb6..1cb6c9ab2981 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -44,6 +44,11 @@ CFLAGS_REMOVE_return_address.o	= $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_sbi_ecall.o = $(CC_FLAGS_FTRACE)
 endif
 
+# 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
+
 always-$(KBUILD_BUILTIN) += vmlinux.lds
 
 obj-y	+= head.o
-- 
2.43.0