linux-kernel - Re: [PATCH 1/8] riscv: stacktrace: convert arch_stack

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Date: Tue, 18 Jun 2024 11:55:32 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Andy Chiu <andy.chiu@...ive.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
 Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alexghiti@...osinc.com>,
 Zong Li <zong.li@...ive.com>, Steven Rostedt <rostedt@...dmis.org>,
 Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
 <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Puranjay Mohan <puranjay@...nel.org>
Cc: Palmer Dabbelt <palmer@...osinc.com>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 llvm@...ts.linux.dev
Subject: Re: [PATCH 1/8] riscv: stacktrace: convert arch_stack_walk() to
 noinstr

Hi Andy,

On 13/06/2024 09:11, Andy Chiu wrote:
> arch_stack_walk() is called intensively in function_graph when the
> kernel is compiled with CONFIG_TRACE_IRQFLAGS. As a result, the kernel
> logs a lot of arch_stack_walk and its sub-functions into the ftrace
> buffer. However, these functions should not appear on the trace log
> because they are part of the ftrace itself. This patch references what
> arm64 does for the smae function. So it further prevent the re-enter
> kprobe issue, which is also possible on riscv.
>
> Related-to: commit 0fbcd8abf337 ("arm64: Prohibit instrumentation on arch_stack_walk()")
> Fixes: 680341382da5 ("riscv: add CALLER_ADDRx support")
> Signed-off-by: Andy Chiu <andy.chiu@...ive.com>
> ---
>   arch/riscv/kernel/stacktrace.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
> index 528ec7cc9a62..0d3f00eb0bae 100644
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -156,7 +156,7 @@ unsigned long __get_wchan(struct task_struct *task)
>   	return pc;
>   }
>   
> -noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
> +noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
>   		     struct task_struct *task, struct pt_regs *regs)
>   {
>   	walk_stackframe(task, regs, consume_entry, cookie);
>

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

I'll try to make this go into -fixes, this is in my fixes branch at least.

Thanks,

Alex