Re: [PATCH v2] tracing: Add sched_prepare_exec tracepoint

Kees Cook
2024-04-11T15:15:10Z

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