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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5EAB44CD-482B-485F-A0E0-0AE7937FFF2C@zytor.com>
Date:   Mon, 08 May 2017 11:57:59 -0700
From:   hpa@...or.com
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...capital.net>
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>,
        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 May 8, 2017 7:40:49 AM PDT, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>On Sun, May 07, 2017 at 10:35:28PM -0700, Andy Lutomirski wrote:
>> I think that, if the code were sufficiently robust, it would be handy
>> if the unwinder displayed function arguments.  DWARF can do that to a
>> limited extent.
>
>Honestly I get the feeling that displaying function arguments wouldn't
>be realistic (DWARF or no DWARF).  On x86-64, arguments are passed in
>registers, so tracking down their values is a lot more involved than
>just looking at the stack.
>
>The DWARF CFI only shows you the callee-saved registers.  To figure out
>the other registers you'd have to dive into the other DWARF sections
>and
>examine previous stack frames for clues.  I think it's not a
>deterministic process, based on how often I see gdb complain with
>'<value optimized out>'.  I'd bet it's a lot harder than a basic stack
>dump.
>
>Also, most kernel functions rely on pointer arguments, which are pretty
>much useless without dumping the contents of the structs they point to.
>But then doing that properly would be a whole new level of difficulty.

At some point you are just reinventing k(g)db...
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.