1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (c) 2019 Facebook 3 4 #include <stddef.h> 5 #include <linux/ptrace.h> 6 #include <linux/bpf.h> 7 #include <bpf/bpf_helpers.h> 8 #include <bpf/bpf_tracing.h> 9 10 int valid = 0; 11 int run_cnt = 0; 12 int required_size_out = 0; 13 int written_stack_out = 0; 14 int written_global_out = 0; 15 16 struct { 17 __u64 _a; 18 __u64 _b; 19 __u64 _c; 20 } fpbe[30] = {0}; 21 22 SEC("perf_event") 23 int perf_branches(void *ctx) 24 { 25 __u64 entries[4 * 3] = {0}; 26 int required_size, written_stack, written_global; 27 28 ++run_cnt; 29 30 /* write to stack */ 31 written_stack = bpf_read_branch_records(ctx, entries, sizeof(entries), 0); 32 /* ignore spurious events */ 33 if (!written_stack) 34 return 1; 35 36 /* get required size */ 37 required_size = bpf_read_branch_records(ctx, NULL, 0, 38 BPF_F_GET_BRANCH_RECORDS_SIZE); 39 40 written_global = bpf_read_branch_records(ctx, fpbe, sizeof(fpbe), 0); 41 /* ignore spurious events */ 42 if (!written_global) 43 return 1; 44 45 required_size_out = required_size; 46 written_stack_out = written_stack; 47 written_global_out = written_global; 48 valid = 1; 49 50 return 0; 51 } 52 53 char _license[] SEC("license") = "GPL"; 54