linux-kernel - Re: [RFC PATCH] ftrace: Skip __fentry__ location of overridden weak functions

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Date: Fri, 7 Jun 2024 11:39:22 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Zheng Yejian <zhengyejian1@...wei.com>, mcgrof@...nel.org,
 mhiramat@...nel.org, mark.rutland@....com, mathieu.desnoyers@...icios.com,
 jpoimboe@...nel.org, linux-modules@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 bpf@...r.kernel.org
Subject: Re: [RFC PATCH] ftrace: Skip __fentry__ location of overridden weak
 functions

On Fri, 7 Jun 2024 17:02:28 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> > There may be following resolutions:  
> 
> Oh gawd, sodding weak functions again.
> 
> I would suggest changing scipts/kallsyms.c to emit readily identifiable
> symbol names for all the weak junk, eg:
> 
>   __weak_junk_NNNNN
> 
> That instantly fixes the immediate problem and Steve's horrid hack can
> go away.

Right. And when I wrote that hack, I specifically said this should be
fixed in kallsyms, and preferably at build time, as that's when the
weak functions should all be resolved.

-- Steve


> 
> Additionally, I would add a boot up pass that would INT3 fill all such
> functions and remove/invalidate all
> static_call/static_jump/fentry/alternative entry that is inside of them.