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

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Date:   Mon, 8 May 2017 09:50:54 +0200
From:   Vojtech Pavlik <vojtech@...e.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     hpa@...or.com, Ingo Molnar <mingo@...nel.org>,
        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>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Jiri Kosina <jikos@...nel.org>
Subject: Re: [PATCH 7/7] DWARF: add the config option

On Sun, May 07, 2017 at 04:48:36PM -0500, Josh Poimboeuf wrote:

> > Can objtool verify the unwinder at each address in the kernel, or is that an AI-complete problem?
> 
> It can't verify the *unwinder*, but it can verify the data which is fed
> to the unwinder (either DWARF or the structs I proposed above).  For
> each function, it follows every possible code path, and it can keep
> track of the stack pointer while doing so.

In that case, the kernel build process can verify the DWARF data and its
compatibility with the kernel unwinder by running the unwinder against
each kernel code address verifying the output and bail if there is a bug
in the toolchain that affects it.

-- 
Vojtech Pavlik
Director SuSE Labs