| Future ABI changes | |
| ================== | |
| This file collects items that require a libperf ABI bump. Each entry | |
| should describe the current limitation, the desired end state, and the | |
| scope of the change so that a future ABI revision can batch them | |
| together. | |
| 1. Widen struct perf_cpu.cpu from int16_t to int | |
| - Current limit: 32767 CPUs. No architecture exceeds this today | |
| (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 | |
| internal array (RC_CHK_ACCESS(map)->map[]) stores struct perf_cpu | |
| directly. Widening changes the struct layout and every function | |
| that returns or accepts struct perf_cpu by value. | |
| - Migration: bump LIBPERF version in libperf.map, audit all | |
| sizeof(struct perf_cpu) assumptions, update perf.data | |
| serialization if needed. |