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 required_size_out = 0; 12 int written_stack_out = 0; 13 int written_global_out = 0; 14 15 struct { 16 __u64 _a; 17 __u64 _b; 18 __u64 _c; 19 } fpbe[30] = {0}; 20 21 SEC("perf_event") 22 int perf_branches(void *ctx) 23 { 24 __u64 entries[4 * 3] = {0}; 25 int required_size, written_stack, written_global; 26 27 /* write to stack */ 28 written_stack = bpf_read_branch_records(ctx, entries, sizeof(entries), 0); 29 /* ignore spurious events */ 30 if (!written_stack) 31 return 1; 32 33 /* get required size */ 34 required_size = bpf_read_branch_records(ctx, NULL, 0, 35 BPF_F_GET_BRANCH_RECORDS_SIZE); 36 37 written_global = bpf_read_branch_records(ctx, fpbe, sizeof(fpbe), 0); 38 /* ignore spurious events */ 39 if (!written_global) 40 return 1; 41 42 required_size_out = required_size; 43 written_stack_out = written_stack; 44 written_global_out = written_global; 45 valid = 1; 46 47 return 0; 48 } 49 50 char _license[] SEC("license") = "GPL"; 51