linux-kernel - Re: 5.15 ftrace bug when enabling function

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Message-ID: <20220805145333.1360dbbb@gandalf.local.home>
Date:   Fri, 5 Aug 2022 14:53:33 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ivan Babrou <ivan@...udflare.com>
Cc:     Daniel Dao <dqminh@...udflare.com>,
        kernel-team <kernel-team@...udflare.com>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: 5.15 ftrace bug when enabling function_graph

On Fri, 5 Aug 2022 11:37:56 -0700
Ivan Babrou <ivan@...udflare.com> wrote:

> root@foo:~# echo 'bpf_dispatcher_*_func' >
> /sys/kernel/tracing/set_ftrace_notrace
> 
> root@foo:~# trace-cmd record -p function_graph -l handle_mm_fault -P 3367417
> plugin 'function_graph'
> Hit Ctrl^C to stop recording


> [1459709.204253] ------------[ ftrace bug ]------------
> [1459709.204257] ftrace failed to modify
> [1459709.204262] [<ffffffffac3ea960>] bpf_dispatcher_xdp_func+0x0/0x10
> [1459709.204275]  actual:   ffffffe9:ffffff9b:76:ffffffb0:14
> [1459709.204302] Setting ftrace call site to call ftrace function
> [1459709.204305] ftrace record flags: 10000001
> [1459709.204309]  (1)
>                   expected tramp: ffffffffabc4bcb0
> [1459709.204325] ------------[ cut here ]------------

Did you reboot since the error happened? Because the command you showed
should not have touched bpf_dispatcher_xdp_func.

-- Steve