linux-kernel - Re: [PATCH] recordmcount.pl: look for jgnop instruction as well as bcrl on s390

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Date:   Fri, 10 Dec 2021 16:51:35 +0100
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     Jerome Marchand <jmarchan@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] recordmcount.pl: look for jgnop instruction as well as
 bcrl on s390

On Fri, Dec 10, 2021 at 01:31:23PM +0100, Miroslav Benes wrote:
> > > Otherwise I would be surprised that this would make any difference.
> > 
> > How come? I mean, s390 does not define HAVE_C_RECORDMCOUNT which implies 
> > that recordmcount.pl is used (see scripts/Makefile.build and 
> > BUILD_C_RECORDMCOUNT definition in Makefile).
> 
> Ah, sorry, that was too quick.
> 
> I guess you want to say that recordmcount is not used at all and GCC 
> should do it. Because CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT is not set, 
> since FTRACE_MCOUNT_USE_CC should be set.
> 
> What a maze.
> 
> But isn't -mrecord-mcount x86_64-only option?

No, it is (at least) also supported on s390. IIRC that was added with
gcc9. Anyway, this is not too important since the fix makes sense
anyway.