linux-kernel - Re: objtool warnings for kernel/trace/trace_selftest

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Message-ID: <20181217210334.GW25620@tassilo.jf.intel.com>
Date:   Mon, 17 Dec 2018 13:03:34 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: objtool warnings for kernel/trace/trace_selftest_dynamic.o

> > That seems weird. 
> > 
> > Are you sure it's not just because they are empty? AFAIK
> > gcc doesn't necessarily generate frame pointers for empty functions.
> 
> I suspected that it was because they're empty, however I didn't see this
> warning for other leaf functions.  The sancov plugin is presumably
> taking care of adding frame pointers where needed.  Also, adding

That would surprise me. 

> -mno-omit-leaf-frame-pointer didn't fix it.
> 
> And anyway I confirmed that it was fixed by removing __noclone.

So this is with a plugin?

Maybe the plugin does something wrong?

I thought this was just a standard build.

I'm not sure the problem is well enough understood yet
to really do anything.

Do you have a simple standalone test case to show the compiler behavior?


-Andi