linux-kernel - Re: [PATCH] ftrace: add simple oneshot function tracer

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: <20190529104552.146fa97c@oasis.local.home>
Date:   Wed, 29 May 2019 10:45:52 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Preisner <linux@...eisner.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: add simple oneshot function tracer

On Wed, 29 May 2019 11:31:23 +0200
Thomas Preisner <linux@...eisner.de> wrote:

> The "oneshot" tracer records every address (ip, parent_ip) exactly once.
> As a result, "oneshot" can be used to efficiently create kernel function
> coverage/usage reports such as in undertaker-tailor[0].
> 
> In order to provide this functionality, "oneshot" uses a
> configurable hashset for blacklisting already recorded addresses. This
> way, no user space application is required to parse the function
> tracer's output and to deactivate functions after they have been
> recorded once. Additionally, the tracer's output is reduced to a bare
> mininum so that it can be passed directly to undertaker-tailor.
> 
> Further information regarding this oneshot function tracer can also be
> found at [1].
> 
> [0]: https://undertaker.cs.fau.de
> [1]: https://tpreisner.de/pub/ba-thesis.pdf
> 
> Signed-off-by: Thomas Preisner <linux@...eisner.de>
>

Hi,

If you are only interested in seeing what functions are called (and
don't care about the order), why not just make another function
profiler (see register_ftrace_profiler and friends)? Then you could
just list the hash table entries instead of having to record into the
ftrace ring buffer.

-- Steve