Re: [PATCH v4 1/3] perf evsel: don't set PERF_SAMPLE_IP for unprivileged tracepoints

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Uprobes silently lose the `PERF_SAMPLE_IP` bit when `perf` is built without `libtraceevent` support, breaking uprobe profiling for unprivileged users.
--

commit 07ebb257f5c9c09215f15379588d99009f389e9e
Author: Anubhav Shelat <ashelat@redhat.com>

perf evsel: don't set PERF_SAMPLE_IP for unprivileged tracepoints

This commit avoids exposing kernel addresses by dropping the PERF_SAMPLE_IP
bit for unprivileged tracepoints. It makes an exception for uprobes since
they expose safe userspace addresses.

> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c

[ ... ]

> @@ -1509,7 +1509,19 @@ void evsel__config(struct evsel *evsel, const struct record_opts *opts,
>  	attr->write_backward = opts->overwrite ? 1 : 0;
>  	attr->read_format   = PERF_FORMAT_LOST;
>  
> -	evsel__set_sample_bit(evsel, IP);
> +	/*
> +	 * Don't set PERF_SAMPLE_IP for unprivileged kernel tracepoints to
> +	 * avoid exposing kernel addresses. Uprobes expose only userspace
> +	 * addresses so they're safe. Detect entry and return uprobes.
> +	 */
> +	if (attr->type != PERF_TYPE_TRACEPOINT || perf_event_paranoid_check(1)
> +#ifdef HAVE_LIBTRACEEVENT
> +	    || evsel__field(evsel, "__probe_ip")
> +	    || evsel__field(evsel, "__probe_ret_ip")
> +#endif
> +	    )
> +		evsel__set_sample_bit(evsel, IP);

Does this silently drop the PERF_SAMPLE_IP bit for unprivileged uprobes when
perf is built without libtraceevent support?

If HAVE_LIBTRACEEVENT is not defined, the uprobe detection logic is compiled
out, meaning the condition evaluates to false for unprivileged uprobes.

Is there a fallback detection mechanism that could be used here (such as
checking the event or PMU name) to ensure uprobe profiling continues to work
for unprivileged users on these builds?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260515194010.93725-2-ashelat@redhat.com?part=1