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

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Message-ID: <20170523054906.q2x2hib73fo7wibh@gmail.com>
Date:   Tue, 23 May 2017 07:49:06 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     "H. Peter Anvin" <hpa@...or.com>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, 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>,
        Andy Lutomirski <luto@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 7/7] DWARF: add the config option


* H. Peter Anvin <hpa@...or.com> wrote:

> On 05/22/17 04:12, Ingo Molnar wrote:
> \>>
> >> This construct might be useful for other arches, which is why I called
> >> it "FP" instead of "BP".  But then I ruined that with the last 3 :-)
> > 
> > Please call it BP - 'FP' can easily be read as floating-point, making it all 
> > super-confusing. We should use canonical x86 register names and ordering - even
> > if not all registers are used straight away.
> > 
> 
> Seriously, I suspect that at the end of the day we will have reinvented
> DWARF.

Absolutely - the main difference is:

 - the debug-info implementation is _internal_ to the kernel so it can be fixed
   instead of "oh, wait 2 years for the toolchain to fix this particular bug, work
   it around in the kernel meanwhile" kind of crazy flow and dependencies. I.e. 
   the debug-info generation and parsing code is both part of the kernel Git tree 
   and can be iterated (and fixed) at once with.

 - the debug-info is auto-generated for assembly as well, leaving assembly code 
   maintainable.

 - the debug-info has a sane data structure designed for robustness and 
   compactness

So even if it's a subset of the existing complexity of dwarf et al we are still 
literally infinitely better off with this model.

Thanks,

	Ingo