linux-kernel - Re: [PATCH 1/1] stackleak: Disable ftrace for stackleak.c

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Message-Id: <20181113102145.2274aedc6f9edaba681bfd3a@kernel.org>
Date:   Tue, 13 Nov 2018 10:21:45 -0800
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Alexander Popov <alex.popov@...ux.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        kernel-hardening@...ts.openwall.com,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>, Jan Kara <jack@...e.cz>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] stackleak: Disable ftrace for stackleak.c

On Mon, 12 Nov 2018 12:21:48 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Mon, 12 Nov 2018 19:51:00 +0300
> Alexander Popov <alex.popov@...ux.com> wrote:
> 
> > By the way, are there any other tracing/instrumentation mechanisms that should
> > be disabled?
> 
> ftrace and kprobes are pretty much the only ones that currently do self
> modification of code all over the kernel. Kprobes even more so than
> ftrace.

Right, since kprobes uses int3 or sw breakpoint exception for hooking into
the code, it consumes stack much more.

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>