linux-kernel - Re: [PATCH] ftrace: make ftrace

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Message-ID: <CADxym3bjjp8edgbpAct0GKno3NGLxs2Pd0hod94r7u_2jGUC5w@mail.gmail.com>
Date: Wed, 16 Apr 2025 09:45:54 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: mhiramat@...nel.org, mark.rutland@....com, mathieu.desnoyers@...icios.com, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Jin Guo <guoj17@...natelecom.cn>
Subject: Re: [PATCH] ftrace: make ftrace_location() more accurate

On Tue, Apr 15, 2025 at 7:45 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 15 Apr 2025 19:27:50 +0800
> Jin Guo <menglong8.dong@...il.com> wrote:
>
> > The function ftrace_location is used to lookup the ftrace location with an
> > ip. However, the result that it returns can be wrong in some case.
> >
> > Let's image that we have the following kallsyms:
> >
> >   ffffffff812c35f0 T sys_ni_syscall
> >   ffffffff812c38b0 W __pfx___x64_sys_io_pgetevents_time32
> >   ffffffff812c38c0 W __x64_sys_io_pgetevents_time32
>
> Have you tried the latest kernel? because on x86, weak functions that are
> not used should no longer be in the ftrace table. That is, you should never
> see __ftrace_invalid_addres_* anymore.
>
> See https://lore.kernel.org/all/20250218195918.255228630@goodmis.org/
>
> That was just added this merge window, which would make your patch obsolete.

Hi, Steve

you are right, I haven't updated my code in over a month, and
the latest kernel works fine.

>
> -- Steve