linux-kernel - Re: [PATCH] x86: mostly disable '-maccumulate-outgoing-args'

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Message-ID: <20170316190401.bplktmr53r7rlq55@treble>
Date:   Thu, 16 Mar 2017 14:04:01 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     x86@...nel.org, Andy Lutomirski <luto@...capital.net>,
        Pavel Machek <pavel@....cz>,
        kernel list <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Peter Anvin <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86: mostly disable '-maccumulate-outgoing-args'

On Thu, Mar 16, 2017 at 01:53:05PM -0500, Josh Poimboeuf wrote:
> On Thu, Mar 16, 2017 at 01:36:35PM -0500, Josh Poimboeuf wrote:
> > On Thu, Mar 16, 2017 at 01:32:01PM -0400, Steven Rostedt wrote:
> > > On Thu, 16 Mar 2017 10:42:08 -0500
> > > Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> > > > +	ACCUMULATE_OUTGOING_ARGS := 1
> > > > +    endif
> > > > +  endif
> > > > +endif
> > > > +
> > > > +# Jump labels need '-maccumulate-outgoing-args' for gcc < 4.5.2 to prevent
> > > 
> > > Can we make a test instead? I hate testing versions, and things get
> > > backported all the time. We usually like to have a test case instead of
> > > relying on versions. Not to mention, a newer gcc may one day break.
> > 
> > Tests are generally better, but I'm not sure how to test for this
> > cleanly.  The test is rather big for embedding in a makefile:
> > 
> >   https://gcc.gnu.org/bugzilla/attachment.cgi?id=22199
> > 
> > Any ideas?
> 
> After some snooping I discovered there's some precedent for doing this
> in the scripts/gcc-*.sh files.  So maybe I'll add a test there and call
> it from the Makefile.

But now I realize that those other tests are just build tests, whereas
this one needs to be executed.  That's a no-go for cross compilers.  So
I think we need to do the version check after all.

-- 
Josh