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/*
* RandomRead Monitor random number read events.
* For Linux, uses BCC, eBPF. Embedded C.
*
* Basic example of BCC Tracepoint and perf buffer.
*
* USAGE: RandomRead
*
* Copyright (c) Facebook, Inc.
* Licensed under the Apache License, Version 2.0 (the "License")
*/
#include <signal.h>
#include <sys/resource.h>
#include <iostream>
#include "BPF.h"
const std::string BPF_PROGRAM = R"(
#include <linux/sched.h>
#include <uapi/linux/ptrace.h>
#ifndef CGROUP_FILTER
#define CGROUP_FILTER 0
#endif
struct event_t {
int pid;
char comm[16];
int cpu;
int got_bits;
};
BPF_PERF_OUTPUT(events);
BPF_CGROUP_ARRAY(cgroup, 1);
int on_urandom_read(struct bpf_raw_tracepoint_args *ctx) {
if (CGROUP_FILTER && (cgroup.check_current_task(0) != 1))
return 0;
struct event_t event = {};
event.pid = bpf_get_current_pid_tgid();
bpf_get_current_comm(&event.comm, sizeof(event.comm));
event.cpu = bpf_get_smp_processor_id();
// from include/trace/events/random.h:
// TP_PROTO(int got_bits, int pool_left, int input_left)
event.got_bits = ctx->args[0];
events.perf_submit(ctx, &event, sizeof(event));
return 0;
}
)";
// Define the same struct to use in user space.
struct event_t {
int pid;
char comm[16];
int cpu;
int got_bits;
};
void handle_output(void* cb_cookie, void* data, int data_size) {
auto event = static_cast<event_t*>(data);
std::cout << "PID: " << event->pid << " (" << event->comm << ") on CPU "
<< event->cpu << " read " << event->got_bits << " bits"
<< std::endl;
}
ebpf::BPF* bpf;
void signal_handler(int s) {
std::cerr << "Terminating..." << std::endl;
delete bpf;
exit(0);
}
void usage(void) {
std::cerr << "USAGE: RandomRead [{-r|-u} [cgroup2_path]]" << std::endl;
}
int main(int argc, char** argv) {
if (argc > 3) {
usage();
return 1;
}
bool allow_rlimit = true;
if (argc >= 2) {
// Set a small rlimit for MEMLOCK
struct rlimit rlim_new = {4096, 4096};
setrlimit(RLIMIT_MEMLOCK, &rlim_new);
if (strcmp(argv[1], "-r") == 0) {
allow_rlimit = false;
} else if (strcmp(argv[1], "-u") == 0) {
allow_rlimit = true;
} else {
usage();
return 1;
}
}
std::vector<std::string> cflags = {};
if (argc == 3)
cflags.emplace_back("-DCGROUP_FILTER=1");
bpf = new ebpf::BPF(0, nullptr, true, "", allow_rlimit);
auto init_res = bpf->init(BPF_PROGRAM, cflags, {});
if (init_res.code() != 0) {
std::cerr << init_res.msg() << std::endl;
return 1;
}
if (argc == 3) {
auto cgroup_array = bpf->get_cgroup_array("cgroup");
auto update_res = cgroup_array.update_value(0, argv[2]);
if (update_res.code() != 0) {
std::cerr << update_res.msg() << std::endl;
return 1;
}
}
auto attach_res =
bpf->attach_raw_tracepoint("urandom_read", "on_urandom_read");
if (attach_res.code() != 0) {
std::cerr << attach_res.msg() << std::endl;
return 1;
}
auto open_res = bpf->open_perf_buffer("events", &handle_output);
if (open_res.code() != 0) {
std::cerr << open_res.msg() << std::endl;
return 1;
}
// done with all initial work, free bcc memory
if (bpf->free_bcc_memory()) {
std::cerr << "Failed to free llvm/clang memory" << std::endl;
return 1;
}
signal(SIGINT, signal_handler);
std::cout << "Started tracing, hit Ctrl-C to terminate." << std::endl;
while (true)
bpf->poll_perf_buffer("events");
return 0;
}
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