Re: [RFC v1 18/19] ptwrite uprobes / perf tools script: Add ptwrite uprobes decoder

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The script queries the local host's `/sys/kernel/tracing` to map dynamic event IDs, which silently breaks offline and cross-platform analysis of `perf.data` files.
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commit cc31146d83897ea76d8b39eb7c2282185b7e63ac
Author: Andi Kleen <ak@kernel.org>

ptwrite uprobes / perf tools script: Add ptwrite uprobes decoder

Add a decoder for the PTWRITE records generated by ptwrite uprobes.
This runs as a python script in perf script.

> diff --git a/tools/perf/scripts/python/uprobe-ptwrite-decode.py b/tools/perf/scripts/python/uprobe-ptwrite-decode.py
> new file mode 100755
> index 0000000000000..22f21cb168e12
> --- /dev/null
> +++ b/tools/perf/scripts/python/uprobe-ptwrite-decode.py
> @@ -0,0 +1,416 @@
[ ... ]
> +TRACEFS = "/sys/kernel/tracing"
[ ... ]
> +def load_events(root=TRACEFS):
> +    """Scan tracefs for (event_id -> (name, [(arg name, type)]))."""
> +    events = {}
> +    try:
> +        groups = os.listdir(root + "/events")

[Severity: Medium]
Does coupling the event decoding logic to the host machine's live tracefs
state break offline cross-platform analysis of perf.data files?

Trace event IDs are dynamically assigned by the kernel and can differ across
machines or reboots. When a perf.data file is analyzed offline on a different
machine, the embedded ptwrite payload event IDs (which were generated on the
recording machine) will be incorrectly mapped to whatever unrelated events
happen to share those IDs in the local host's /sys/kernel/tracing. This can
lead to garbage decoding output.

Could the script be modified to extract event definitions from the perf.data
header instead of silently defaulting to the host's tracefs?

> +    except OSError:
> +        return events
> +    for g in groups:
> +        gdir = root + "/events/" + g
> +        if not os.path.isdir(gdir):
> +            continue

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Sashiko AI review · https://sashiko.dev/#/patchset/20260831150651.1134594-1-ak@kernel.org?part=18