1f54ce060SArnaldo Carvalho de MeloFuture ABI changes 2f54ce060SArnaldo Carvalho de Melo================== 3f54ce060SArnaldo Carvalho de Melo 4f54ce060SArnaldo Carvalho de MeloThis file collects items that require a libperf ABI bump. Each entry 5f54ce060SArnaldo Carvalho de Meloshould describe the current limitation, the desired end state, and the 6f54ce060SArnaldo Carvalho de Meloscope of the change so that a future ABI revision can batch them 7f54ce060SArnaldo Carvalho de Melotogether. 8f54ce060SArnaldo Carvalho de Melo 9f54ce060SArnaldo Carvalho de Melo1. Widen struct perf_cpu.cpu from int16_t to int 10f54ce060SArnaldo Carvalho de Melo - Current limit: 32767 CPUs. No architecture exceeds this today 11f54ce060SArnaldo Carvalho de Melo (x86_64 max is 8192, arm64 is 4096), but NR_CPUS limits keep 12f54ce060SArnaldo Carvalho de Melo growing. perf clamps to INT16_MAX in set_max_cpu_num() as a 13f54ce060SArnaldo Carvalho de Melo safety net. 14*7435c406SArnaldo Carvalho de Melo - Code simplification: the int16_t forces defensive truncation 15*7435c406SArnaldo Carvalho de Melo checks at every boundary where a wider CPU index (int from 16*7435c406SArnaldo Carvalho de Melo sample->cpu, al->cpu, etc.) is narrowed into struct perf_cpu. 17*7435c406SArnaldo Carvalho de Melo Without these checks, values > 32767 silently wrap to negative 18*7435c406SArnaldo Carvalho de Melo numbers (two's complement), bypassing bounds validation. 19*7435c406SArnaldo Carvalho de Melo Widening to int eliminates this entire class of silent 20*7435c406SArnaldo Carvalho de Melo truncation bugs and removes the need for the INT16_MAX clamp 21*7435c406SArnaldo Carvalho de Melo in set_max_cpu_num(). 22f54ce060SArnaldo Carvalho de Melo - Scope: struct perf_cpu is embedded everywhere — perf_cpu_map__cpu(), 23f54ce060SArnaldo Carvalho de Melo perf_cpu_map__min(), perf_cpu_map__max(), perf_cpu_map__has(), the 24f54ce060SArnaldo Carvalho de Melo for_each_cpu macros, and all internal callers. The perf_cpu_map 25f54ce060SArnaldo Carvalho de Melo internal array (RC_CHK_ACCESS(map)->map[]) stores struct perf_cpu 26f54ce060SArnaldo Carvalho de Melo directly. Widening changes the struct layout and every function 27f54ce060SArnaldo Carvalho de Melo that returns or accepts struct perf_cpu by value. 28f54ce060SArnaldo Carvalho de Melo - Migration: bump LIBPERF version in libperf.map, audit all 29f54ce060SArnaldo Carvalho de Melo sizeof(struct perf_cpu) assumptions, update perf.data 30f54ce060SArnaldo Carvalho de Melo serialization if needed. 31