linux-kernel - Re: [PATCH v6 10/10] x86/retpoline: Exclude objtool with retpoline

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Date:   Mon, 8 Jan 2018 07:20:07 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     "Woodhouse, David" <dwmw@...zon.co.uk>
Cc:     Thomas Gleixner <tglx@...utronix.de>, Amit Shah <aams@...zon.de>,
        Andi Kleen <ak@...ux.intel.com>, Paul Turner <pjt@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Kees Cook <keescook@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Jiri Kosina <jikos@...nel.org>, gnomes@...rguk.ukuu.org.uk
Subject: Re: [PATCH v6 10/10] x86/retpoline: Exclude objtool with retpoline

On Mon, Jan 08, 2018 at 10:34:00AM +0000, Woodhouse, David wrote:
> On Mon, 2018-01-08 at 11:25 +0100, Thomas Gleixner wrote:
> > On Sun, 7 Jan 2018, David Woodhouse wrote:
> > 
> > Cc+ Josh Poimboeuf <jpoimboe@...hat.com>
> > 
> > Sigh....
> > 
> > > From: Andi Kleen <ak@...ux.intel.com>
> > > 
> > > objtool's assembler nanny currently cannot deal with the code generated
> > > by the retpoline compiler and throws hundreds of warnings, mostly
> > > because it sees calls that don't have a symbolic target.
> > > 
> > > Exclude all the options that rely on objtool when RETPOLINE is active.
> > > 
> > > This mainly means that we use the frame pointer unwinder and livepatch
> > > is not supported.
> > > 
> > > Eventually objtool can be fixed to handle this.
> 
> I believe Josh is on vacation and I've asked Amit to take a look at
> this, at least as far as ensuring that it doesn't actually disable
> kpatch.

I'm back now and will start looking at it this week.

For future revisions of the patch set, can you add me to CC?  And also
it would be good to add x86@...nel.org as I'm sure the other x86
maintainers (mingo and hpa) want to see these patches.

-- 
Josh