Re: [PATCH perf-tools-next v3 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 BTF type routing test does not actually test BTF symbolization, as it silently falls back to the default kallsyms beautifier.
--

--- Patch [4]: [PATCH perf-tools-next v3 4/4] perf tests: Add shell test for kernel symbol beautifier ---
commit c8c43ea37c4e0f26131dd9e871af4241cd478b77
Author: Aaron Tomlin <[email protected]>

perf tests: Add shell test for kernel symbol beautifier

This commit adds a shell test script, trace_ksym_beautifier.sh, to verify
that perf trace symbolises kernel virtual addresses and function pointers
using 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..30a8429669dd5
> --- /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 kmem:kmalloc --force-btf --max-events=1 2>&1)"

[Severity: Medium]
Does this actually test the BTF type routing as intended?

Looking at the kmem:kmalloc tracepoint, the call_site field is defined as an
unsigned long, rather than a function pointer. When trace__btf_scnprintf()
evaluates this, it determines it is an integer rather than a function
pointer, and returns 0.

This causes perf to silently fall back to the default SCA_KSYM beautifier.
Consequently, the test passes via the fallback path rather than truly
exercising the BTF routing.

Would it be better to use a tracepoint with a field explicitly typed as a
function pointer for the --force-btf test?

> +  if ! echo "$output" | grep -q -E "call_site: [a-zA-Z_][a-zA-Z0-9_]*" || echo "$output" | grep -q -E "call_site: 0x[0-9a-fA-F]+"
> +  then
> +    printf "BTF function symbolization failed, output:\n%s\n" "$output"
> +    err=1
> +  fi
> +}

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