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

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Message-ID: <CALCETrVjpxYYBwFxWq+oQ9XCmnKsnw=xV0p7dxx-DJGvGCCPgA@mail.gmail.com>
Date:   Sat, 20 May 2017 14:56:58 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. J. Lu" <hjl.tools@...il.com>, "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        live-patching@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Jiri Kosina <jikos@...nel.org>
Subject: Re: [PATCH 7/7] DWARF: add the config option

On Sat, May 20, 2017 at 1:16 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Fri, May 19, 2017 at 10:23 PM, Andy Lutomirski <luto@...nel.org> wrote:
>>
>> I personally like the idea of using real DWARF annotations in the
>> entry code because it makes gdb work better (not kgdb -- real gdb
>> attached to KVM).  I bet that we could get entry asm annotations into
>> good shape if we really wanted to.  OTOH, getting DWARF to work well
>> for inline asm is really nasty IIRC.
>
> No. I will NAK *any* attempt to make our asm contain the crazy
> shit-for-brains annotations.
>
> Been there, done that, got the T-shirt, and then doused the T-shirt in
> gasoline and put it on fire.
>
> The amount of unreadable crap and bugs it requires is not worth the
> pain. Not for *any* amount of gain, and the gain here is basically
> zero.

But what if objtool autogenerated the annotations, perhaps with a tiny
bit of help telling it "hardware frame goes here" or "pt_regs goes
here"?