| /* |
| * FollyRequestContextSwitch Monitor RequestContext switch events for any binary |
| * uses the class from [folly](http://bit.ly/2h6S1yx). |
| * For Linux, uses BCC, eBPF. Embedded C. |
| * |
| * Basic example of using USDT with BCC. |
| * |
| * USAGE: FollyRequestContextSwitch PATH_TO_BINARY |
| * |
| * Copyright (c) Facebook, Inc. |
| * Licensed under the Apache License, Version 2.0 (the "License") |
| */ |
| |
| #include <signal.h> |
| #include <iostream> |
| #include <vector> |
| |
| #include "BPF.h" |
| |
| const std::string BPF_PROGRAM = R"( |
| #include <linux/sched.h> |
| #include <uapi/linux/ptrace.h> |
| |
| struct event_t { |
| int pid; |
| char name[16]; |
| uint64_t old_addr; |
| uint64_t new_addr; |
| }; |
| |
| BPF_PERF_OUTPUT(events); |
| |
| int on_context_switch(struct pt_regs *ctx) { |
| struct event_t event = {}; |
| |
| event.pid = bpf_get_current_pid_tgid(); |
| bpf_get_current_comm(&event.name, sizeof(event.name)); |
| |
| bpf_usdt_readarg(1, ctx, &event.old_addr); |
| bpf_usdt_readarg(2, ctx, &event.new_addr); |
| |
| events.perf_submit(ctx, &event, sizeof(event)); |
| return 0; |
| } |
| )"; |
| |
| // Define the same struct to use in user space. |
| struct event_t { |
| int pid; |
| char name[16]; |
| uint64_t old_addr; |
| uint64_t new_addr; |
| }; |
| |
| void handle_output(void* cb_cookie, void* data, int data_size) { |
| auto event = static_cast<event_t*>(data); |
| std::cout << "PID " << event->pid << " (" << event->name << ") "; |
| std::cout << "folly::RequestContext switch from " << event->old_addr << " to " |
| << event->new_addr << std::endl; |
| } |
| |
| ebpf::BPF* bpf; |
| |
| void signal_handler(int s) { |
| std::cerr << "Terminating..." << std::endl; |
| delete bpf; |
| exit(0); |
| } |
| |
| int main(int argc, char** argv) { |
| if (argc != 2) { |
| std::cout << "USAGE: FollyRequestContextSwitch PATH_TO_BINARY" << std::endl; |
| exit(1); |
| } |
| std::string binary_path(argv[1]); |
| |
| std::vector<ebpf::USDT> u; |
| u.emplace_back(binary_path, "folly", "request_context_switch_before", |
| "on_context_switch"); |
| auto usdt_init_res = u[0].init(); |
| if (usdt_init_res.code() != 0) { |
| std::cerr << usdt_init_res.msg() << std::endl; |
| return 1; |
| } |
| |
| bpf = new ebpf::BPF(); |
| auto init_res = bpf->init(BPF_PROGRAM, {}, u); |
| if (init_res.code() != 0) { |
| std::cerr << init_res.msg() << std::endl; |
| return 1; |
| } |
| |
| auto attach_res = bpf->attach_usdt(u[0]); |
| if (attach_res.code() != 0) { |
| std::cerr << attach_res.msg() << std::endl; |
| return 1; |
| } else { |
| std::cout << "Attached to USDT " << u[0]; |
| } |
| |
| auto open_res = bpf->open_perf_buffer("events", &handle_output); |
| if (open_res.code() != 0) { |
| std::cerr << open_res.msg() << std::endl; |
| return 1; |
| } |
| |
| signal(SIGINT, signal_handler); |
| std::cout << "Started tracing, hit Ctrl-C to terminate." << std::endl; |
| auto perf_buffer = bpf->get_perf_buffer("events"); |
| if (perf_buffer) |
| while (true) |
| // 100ms timeout |
| perf_buffer->poll(100); |
| |
| return 0; |
| } |