linux-kernel - Re: [RFC PATCH 10/10] x86/unwind: add undwarf unwinder

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: <20170601123609.ku5zq2huhlneq2dn@treble>
Date:   Thu, 1 Jun 2017 07:36:09 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        live-patching@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>, Jiri Slaby <jslaby@...e.cz>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC PATCH 10/10] x86/unwind: add undwarf unwinder

On Thu, Jun 01, 2017 at 02:13:56PM +0200, Peter Zijlstra wrote:
> So we do that lookup for every single frame. That's going to hurt.
> 
> Would it make sense to cache the last 'module' in an attempt to at least
> avoid that lookup again? Something like so:

The only thing with caching the module is, what if the module goes away?

Based on your previous comment I was thinking I would disable preemption
for the entire unwind_next_frame() step, but not *between* steps.  I
suppose we could require the unwind caller to disable preemption but I'd
like to avoid that if possible.

-- 
Josh