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| author | Arnaldo Carvalho de Melo <acme@redhat.com> | 2026-06-08 15:32:32 -0300 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2026-06-10 15:23:54 -0300 |
| commit | 7435c4069a546a5d2421407b3d43fdc1790ce6cc (patch) | |
| tree | 409c0d87050bfb5804a8b72c382cd49001a875b7 /tools | |
| parent | e33711d5e757011bb6d3506af4d6c97dad412b8f (diff) | |
| download | linux-next-7435c4069a546a5d2421407b3d43fdc1790ce6cc.tar.gz linux-next-7435c4069a546a5d2421407b3d43fdc1790ce6cc.zip | |
libperf: Document code simplification case for widening struct perf_cpu
Add a bullet point to the libperf ABI TODO explaining the code
simplification benefit of widening struct perf_cpu.cpu from int16_t
to int: the narrow type forces defensive truncation checks at every
boundary where wider CPU indices are narrowed, and values > 32767
silently wrap to negative numbers (two's complement), bypassing
bounds validation without them.
Acked-by: Ian Rogers <irogers@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/lib/perf/TODO | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/tools/lib/perf/TODO b/tools/lib/perf/TODO index 486dd95dc572..e179728697d8 100644 --- a/tools/lib/perf/TODO +++ b/tools/lib/perf/TODO @@ -11,6 +11,14 @@ together. (x86_64 max is 8192, arm64 is 4096), but NR_CPUS limits keep growing. perf clamps to INT16_MAX in set_max_cpu_num() as a safety net. + - Code simplification: the int16_t forces defensive truncation + checks at every boundary where a wider CPU index (int from + sample->cpu, al->cpu, etc.) is narrowed into struct perf_cpu. + Without these checks, values > 32767 silently wrap to negative + numbers (two's complement), bypassing bounds validation. + Widening to int eliminates this entire class of silent + truncation bugs and removes the need for the INT16_MAX clamp + in set_max_cpu_num(). - Scope: struct perf_cpu is embedded everywhere — perf_cpu_map__cpu(), perf_cpu_map__min(), perf_cpu_map__max(), perf_cpu_map__has(), the for_each_cpu macros, and all internal callers. The perf_cpu_map |