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Date: Thu, 23 Jul 2020 01:56:20 +0200
From: Peter Zijlstra <>
To: Steven Rostedt <>
Cc: Sami Tolvanen <>,
	Masahiro Yamada <>,
	Will Deacon <>,
	Greg Kroah-Hartman <>,
	"Paul E. McKenney" <>,
	Kees Cook <>,
	Nick Desaulniers <>,,,,,,,,, Josh Poimboeuf <>
Subject: Re: [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool

On Wed, Jul 22, 2020 at 03:09:43PM -0400, Steven Rostedt wrote:
> On Wed, 22 Jul 2020 20:41:37 +0200
> Peter Zijlstra <> wrote:
> > > That said, Andi Kleen added an option to gcc called -mnop-mcount which
> > > will have gcc do both create the mcount section and convert the calls
> > > into nops. When doing so, it defines CC_USING_NOP_MCOUNT which will
> > > tell ftrace to expect the calls to already be converted.  
> > 
> > That seems like the much easier solution, then we can forget about
> > recordmcount / objtool entirely for this.
> Of course that was only for some gcc compilers, and I'm not sure if
> clang can do this.
> Or do you just see all compilers doing this in the future, and not
> worrying about record-mcount at all, and bothering with objtool?

I got the GCC version wrong :/ Both -mnop-mcount and -mrecord-mcount
landed in GCC-5, where our minimum GCC is now at 4.9.

Anyway, what do you prefer, I suppose I can make objtool whatever we
need, that patch is trivial. Simply recording the sites and not
rewriting them should be simple enough.

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