linux.git/tools/lib/perf/TODO, branch master Linux kernel source tree libperf: Document code simplification case for widening struct perf_cpu 2026-06-10T18:23:54+00:00 Arnaldo Carvalho de Melo acme@redhat.com 2026-06-08T18:32:32+00:00 7435c4069a546a5d2421407b3d43fdc1790ce6cc 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> 
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>
libperf: Document struct perf_cpu int16_t ABI limitation 2026-06-06T17:46:37+00:00 Arnaldo Carvalho de Melo acme@redhat.com 2026-06-06T17:42:09+00:00 f54ce06049bf716f6b1e3a78e72360d583ea2acb struct perf_cpu.cpu is int16_t, limiting perf to 32767 CPUs. This is part of the libperf ABI (returned by value from perf_cpu_map__cpu() and friends), so widening it requires an ABI bump. Add a comment on the struct definition noting this, and create a TODO file to collect future ABI changes so they can be batched into a single version bump. 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> 
struct perf_cpu.cpu is int16_t, limiting perf to 32767 CPUs.  This is
part of the libperf ABI (returned by value from perf_cpu_map__cpu() and
friends), so widening it requires an ABI bump.

Add a comment on the struct definition noting this, and create a TODO
file to collect future ABI changes so they can be batched into a single
version bump.

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>