linux-kernel - Re: [PATCH 7/7] DWARF: add the config option

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Message-ID: <20170509033831.6zoplbhnidbix5ua@treble>
Date:   Mon, 8 May 2017 22:38:31 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        live-patching@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Jiri Kosina <jikos@...nel.org>
Subject: Re: [PATCH 7/7] DWARF: add the config option

On Mon, May 08, 2017 at 07:31:50PM -0700, Andy Lutomirski wrote:
> On Mon, May 8, 2017 at 6:38 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >> Also, don't you need some indication of which reg is the base from
> >> which you find previous frame?  After all, sometimes GCC will emit a
> >> frame pointer even in an otherwise frame-pointer-omitting kernel.
> >
> > I don't think we *need* to do that.  I believe the base reg can just
> > always[*] be the stack pointer, even with frame pointers.
> 
> What if there are functions that use alloca or variable length arrays
> on the stack?  Functions using AHASH_REQUEST_ON_STACK come to mind.

Wow, mind blown.  This is why I added you to CC!

Ok, I guess we'll need to be able to use the frame pointer as a base
reg.  It should be easy anyway.

-- 
Josh