Received-SPF: pass (google.com: domain of linux-kernel+bounces-140733-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Date: Thu, 11 Apr 2024 08:15:05 -0700
From: Kees Cook <keescook@chromium.org>
To: Marco Elver <elver@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	Eric Biederman <ebiederm@xmission.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Azeem Shaikh <azeemshaikh38@gmail.com>,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH v2] tracing: Add sched_prepare_exec tracepoint
Message-ID: <202404110814.B219872F76@keescook>
References: <20240411102158.1272267-1-elver@google.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240411102158.1272267-1-elver@google.com>

On Thu, Apr 11, 2024 at 12:20:57PM +0200, Marco Elver wrote:
> Add "sched_prepare_exec" tracepoint, which is run right after the point
> of no return but before the current task assumes its new exec identity.
> 
> Unlike the tracepoint "sched_process_exec", the "sched_prepare_exec"
> tracepoint runs before flushing the old exec, i.e. while the task still
> has the original state (such as original MM), but when the new exec
> either succeeds or crashes (but never returns to the original exec).
> 
> Being able to trace this event can be helpful in a number of use cases:
> 
>   * allowing tracing eBPF programs access to the original MM on exec,
>     before current->mm is replaced;
>   * counting exec in the original task (via perf event);
>   * profiling flush time ("sched_prepare_exec" to "sched_process_exec").
> 
> Example of tracing output:
> 
>  $ cat /sys/kernel/debug/tracing/trace_pipe
>     <...>-379  [003] .....  179.626921: sched_prepare_exec: interp=/usr/bin/sshd filename=/usr/bin/sshd pid=379 comm=sshd
>     <...>-381  [002] .....  180.048580: sched_prepare_exec: interp=/bin/bash filename=/bin/bash pid=381 comm=sshd
>     <...>-385  [001] .....  180.068277: sched_prepare_exec: interp=/usr/bin/tty filename=/usr/bin/tty pid=385 comm=bash
>     <...>-389  [006] .....  192.020147: sched_prepare_exec: interp=/usr/bin/dmesg filename=/usr/bin/dmesg pid=389 comm=bash
> 
> Signed-off-by: Marco Elver <elver@google.com>

This looks good to me. If tracing wants to take it:

Acked-by: Kees Cook <keescook@chromium.org>

If not, I can take it in my tree if I get a tracing Ack. :)

-Kees

-- 
Kees Cook