linux-kernel - Re: vmlinux.o: warning: objtool: stackleak_erase()+0x35: call to ftrace_likely

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Message-ID: <20220405093859.05660166@gandalf.local.home>
Date:   Tue, 5 Apr 2022 09:38:59 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: vmlinux.o: warning: objtool: stackleak_erase()+0x35: call to
 ftrace_likely_update() leaves .noinstr.text section

On Tue, 5 Apr 2022 10:03:35 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> > I think I'll just send a patch to nuke the tracer. I'm sure Peter Zijlstra
> > will be happy when I do that. But I still want the profiler, as I find that
> > useful.  
> 
> It'll explode the moment Lai's entry rework goes through. That'll make
> us run C code before we switch to the kernel address space, so your
> counters will not exist/be-mapped and *BOOM*.

We could black list those areas. Just add:

#define DISABLE_BRANCH_PROFILING at the top of any file and it will not
do the profiling.

-- Steve