Re: [PATCH perf-tools-next v5 4/4] perf tests: Add shell test for kernel symbol beautifier

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The test script `trace_ksym_beautifier.sh` intends to verify BTF type routing for function pointers using the `timer:hrtimer_start` tracepoint, but this tracepoint's `function` field is of type `void *`, which bypasses the BTF function pointer routing logic. The test only passes due to a hardcoded fallback for arguments named 'function'.
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--- Patch [4]: [PATCH perf-tools-next v5 4/4] perf tests: Add shell test for kernel symbol beautifier ---
commit e969790d116081081634b0e3ece5c71834b3fe8f
Author: Aaron Tomlin <[email protected]>

perf tests: Add shell test for kernel symbol beautifier

This commit introduces a shell test script to verify that perf trace properly
symbolizes kernel virtual addresses and function pointers. It checks both
the default kallsyms beautifier and BTF type routing.

> diff --git a/tools/perf/tests/shell/trace_ksym_beautifier.sh b/tools/perf/tests/shell/trace_ksym_beautifier.sh
> new file mode 100755
> index 0000000000000..45c803338d4ca
> --- /dev/null
> +++ b/tools/perf/tests/shell/trace_ksym_beautifier.sh

[ ... ]

> +test_ksym_btf() {
> +  echo "Testing perf trace kernel symbol beautifier (BTF)"
> +  if [ ! -f /sys/kernel/btf/vmlinux ]; then
> +    echo "Skipping BTF test due to missing vmlinux BTF"
> +    return
> +  fi
> +
> +  output="$(perf trace -e timer:hrtimer_start --force-btf --max-events=1 -- sleep 0.01 2>&1)"

[Severity: Medium]
Does this test actually verify BTF type routing?

For the timer:hrtimer_start tracepoint, the function field is declared as
a void pointer in both BTF and tracefs. This means btf_is_func_ptr()
will evaluate to false, and trace__btf_scnprintf() will return 0.

The output is successfully symbolized here only because builtin-trace.c
contains a hardcoded fallback array, syscall_arg_fmts__by_name, that maps
any field named function to SCA_KSYM.

Could a different tracepoint be used here that has an actual function
pointer type in BTF, to ensure the BTF type routing logic is being properly
exercised instead of the hardcoded fallback?

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=4