linux-kernel - Re: [BUG] Failed to obtain stack trace via bpf_get

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Message-Id: <20250924170416.0874e56c2ce99a4de92e05b8@kernel.org>
Date: Wed, 24 Sep 2025 17:04:16 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Feng Yang <yangfeng59949@....com>
Cc: alexei.starovoitov@...il.com, andrii@...nel.org, ast@...nel.org,
 bpf@...r.kernel.org, daniel@...earbox.net, eddyz87@...il.com,
 haoluo@...gle.com, john.fastabend@...il.com, jolsa@...nel.org,
 kpsingh@...nel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, martin.lau@...ux.dev, sdf@...ichev.me,
 song@...nel.org, yonghong.song@...ux.dev
Subject: Re: [BUG] Failed to obtain stack trace via bpf_get_stackid on ARM64
 architecture

On Wed, 24 Sep 2025 14:25:36 +0800
Feng Yang <yangfeng59949@....com> wrote:

> By the way, during my testing, I also noticed that when executing bpf_get_stackid via kprobes or tracepoints, 
> the command bpftrace -e 'kprobe:bpf_get_stackid {printf("bpf_get_stackid\n");}' produces no output. 

I think this is because the bpf_get_stackid is a kind of recursive
event from kprobes. Kprobe handler can not be reentered.

> However, it does output something when bpf_get_stackid is invoked via uprobes. 
> This phenomenon also occurs on the x86 architecture, could this be a bug as well?

Maybe if bpf_get_stackid() is kicked from uprobes, it is not recursive
call from kprobes, so it works.

So it is expected behavior, not a bug. Sorry for confusion.


Thank you,

> 
> Thanks.
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>