Re: [PATCH v4 RESEND 2/7] riscv: stacktrace: disable KASAN and KCOV instrumentation for stacktrace.o

[Shuai Xue <xueshuai@linux.alibaba.com>]

On 6/29/26 3:27 PM, Wang Han wrote:
> 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.
> 
> KCOV instruments every basic-block edge. The unwinder is a hot path,
> especially with KASAN enabled, so KCOV instrumentation has the same kind
> of cost and noise problem here.
> 
> Mark stacktrace.o as not KASAN- or KCOV-instrumented, matching the x86
> treatment of its stack unwinding code. RISC-V keeps the relevant unwinder
> code in stacktrace.o, so a single translation-unit annotation covers the
> equivalent scope. This is a prerequisite preference for the upcoming
> reliable unwinder, but the change is valid on its own.
> 
> Signed-off-by: Wang Han <wanghan@linux.alibaba.com>
> ---
>   arch/riscv/kernel/Makefile | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index cabb99cadfb6..c565a72a36f3 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -44,6 +44,12 @@ CFLAGS_REMOVE_return_address.o	= $(CC_FLAGS_FTRACE)
>   CFLAGS_REMOVE_sbi_ecall.o = $(CC_FLAGS_FTRACE)
>   endif
>   
> +# When KASAN is enabled, a stack trace is recorded for every alloc/free, which
> +# can significantly impact performance. Avoid instrumenting the stack trace
> +# collection code to minimize this impact.
> +KASAN_SANITIZE_stacktrace.o := n
> +KCOV_INSTRUMENT_stacktrace.o := n
> +
>   always-$(KBUILD_BUILTIN) += vmlinux.lds
>   
>   obj-y	+= head.o

Reviewed-by: Shuai Xue <xueshuai@linux.alibaba.com>

Thanks.
Shuai