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/*
* Copyright (c) Facebook, Inc.
* Licensed under the Apache License, Version 2.0 (the "License")
*
* Usage:
* ./TaskIterator
*
* BPF task iterator is available since linux 5.8.
* This example shows how to dump all threads in the system with
* bpf iterator. An example output likes below:
* tid comm
* 1 systemd
* 2 kthreadd
* 3 rcu_gp
* 4 rcu_par_gp
* 6 kworker/0:0H
* ...
* 2613386 sleep
* 2613474 GetCountersCPU6
* 2613587 GetCountersCPU7
* 2613621 CPUThreadPool69
* 2613906 GetCountersCPU5
* 2614140 GetCountersCPU2
* 2614193 CfgrExtension56
* 2614449 ruby-timer-thr
* 2614529 chef-client
* 2615122 systemd-hostnam
* ...
* 2608477 sudo
* 2608478 TaskIterator
*/
#include <unistd.h>
#include <fstream>
#include <iostream>
#include <string>
#include "bcc_version.h"
#include "BPF.h"
const std::string BPF_PROGRAM = R"(
#include <linux/bpf.h>
#include <linux/seq_file.h>
#include <linux/sched.h>
/* the structure is defined in .c file, so explicitly define
* the structure here.
*/
struct bpf_iter__task {
union {
struct bpf_iter_meta *meta;
};
union {
struct task_struct *task;
};
};
struct info_t {
int tid;
char comm[TASK_COMM_LEN];
};
BPF_ITER(task) {
struct seq_file *seq = ctx->meta->seq;
struct task_struct *task = ctx->task;
struct info_t info = {};
if (task == (void *)0)
return 0;
info.tid = task->pid;
__builtin_memcpy(&info.comm, task->comm, sizeof(info.comm));
bpf_seq_write(seq, &info, sizeof(info));
return 0;
}
)";
// linux/sched.h
#define TASK_COMM_LEN 16
struct info_t {
int tid;
char comm[TASK_COMM_LEN];
};
int main() {
ebpf::BPF bpf;
auto res = bpf.init(BPF_PROGRAM);
if (res.code() != 0) {
std::cerr << res.msg() << std::endl;
return 1;
}
int prog_fd;
res = bpf.load_func("bpf_iter__task", BPF_PROG_TYPE_TRACING, prog_fd);
if (res.code() != 0) {
std::cerr << res.msg() << std::endl;
return 1;
}
int link_fd = bcc_iter_attach(prog_fd, NULL, 0);
if (link_fd < 0) {
std::cerr << "bcc_iter_attach failed: " << link_fd << std::endl;
return 1;
}
int iter_fd = bcc_iter_create(link_fd);
if (iter_fd < 0) {
std::cerr << "bcc_iter_create failed: " << iter_fd << std::endl;
close(link_fd);
return 1;
}
// Header.
printf("tid\tcomm\n");
struct info_t info[20];
int len, leftover = 0, info_size = 20 * sizeof(struct info_t);
while ((len = read(iter_fd, (char *)info + leftover, info_size - leftover))) {
if (len < 0) {
if (len == -EAGAIN)
continue;
std::cerr << "read failed: " << len << std::endl;
break;
}
int num_info = len / sizeof(struct info_t);
for (int i = 0; i < num_info; i++) {
printf("%d\t%s\n", info[i].tid, info[i].comm);
}
leftover = len % sizeof(struct info_t);
if (num_info > 0)
memcpy(info, (void *)&info[num_info], leftover);
}
close(iter_fd);
close(link_fd);
return 0;
}
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