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examples/c: add bootstrap_legacy for compatibility with older kernels
Signed-off-by: Runlong Lin <[email protected]>
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‎README.md‎

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@@ -108,6 +108,22 @@ TIME EVENT COMM PID PPID FILENAME/EXIT CODE
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...
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```
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## bootstrap_legacy
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`bootstrap_legacy` is a version of `bootstrap` modified to run on older kernels that do not support BPF ring buffer maps (BPF_MAP_TYPE_RINGBUF) introduced in kernel 5.8. `bootstrap_legacy` replaces the ring buffer maps with perf event array (BPF_MAP_TYPE_PERF_EVENT_ARRAY) for compatibility with older kernel versions.
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```shell
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$ cd examples/c
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$ make bootstrap_legacy
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$ sudo ./bootstrap_legacy
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TIME EVENT COMM PID PPID FILENAME/EXIT CODE
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10:26:32 EXEC sh 4101543 4054526 /bin/sh
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10:26:32 EXEC python 4101545 4101543 /usr/bin/python
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10:26:32 EXIT python 4101545 4101543 [0] (9ms)
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10:26:32 EXIT sh 4101543 4054526 [0] (10ms)
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...
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```
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## uprobe
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`uprobe` is an example of dealing with user-space entry and exit (return) probes,

‎examples/c/Makefile‎

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@@ -24,7 +24,7 @@ INCLUDES := -I$(OUTPUT) -I../../libbpf/include/uapi -I$(dir $(VMLINUX)) -I$(LIBB
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CFLAGS := -g -Wall
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ALL_LDFLAGS := $(LDFLAGS) $(EXTRA_LDFLAGS)
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APPS = minimal minimal_legacy minimal_ns bootstrap uprobe kprobe fentry \
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APPS = minimal minimal_legacy minimal_ns bootstrap bootstrap_legacy uprobe kprobe fentry \
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usdt sockfilter tc ksyscall task_iter lsm
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CARGO ?= $(shell which cargo)

‎examples/c/bootstrap_legacy.bpf.c‎

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// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
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/* Copyright (c) 2020 Facebook */
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#include "vmlinux.h"
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_core_read.h>
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#include "bootstrap.h"
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char LICENSE[] SEC("license") = "Dual BSD/GPL";
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, 8192);
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__type(key, pid_t);
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__type(value, u64);
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} exec_start SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
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__uint(key_size, sizeof(u32));
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__uint(value_size, sizeof(u32));
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} pe SEC(".maps");
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const volatile unsigned long long min_duration_ns = 0;
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SEC("tp/sched/sched_process_exec")
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int handle_exec(struct trace_event_raw_sched_process_exec *ctx)
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{
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struct task_struct *task;
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unsigned fname_off;
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struct event *e = &(struct event){};
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pid_t pid;
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u64 ts;
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/* remember time exec() was executed for this PID */
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pid = bpf_get_current_pid_tgid() >> 32;
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ts = bpf_ktime_get_ns();
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bpf_map_update_elem(&exec_start, &pid, &ts, BPF_ANY);
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/* don't emit exec events when minimum duration is specified */
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if (min_duration_ns)
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return 0;
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/* fill out the sample with data */
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task = (struct task_struct *)bpf_get_current_task();
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e->exit_event = false;
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e->pid = pid;
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e->ppid = BPF_CORE_READ(task, real_parent, tgid);
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bpf_get_current_comm(&e->comm, sizeof(e->comm));
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fname_off = ctx->__data_loc_filename & 0xFFFF;
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bpf_probe_read_str(&e->filename, sizeof(e->filename), (void *)ctx + fname_off);
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/* use perf event output to send data to user-space for post-processing */
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bpf_perf_event_output(ctx, &pe, BPF_F_CURRENT_CPU, e, sizeof(*e));
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return 0;
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}
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SEC("tp/sched/sched_process_exit")
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int handle_exit(struct trace_event_raw_sched_process_template *ctx)
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{
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struct task_struct *task;
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struct event *e = &(struct event){};
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pid_t pid, tid;
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u64 id, ts, *start_ts, duration_ns = 0;
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/* get PID and TID of exiting thread/process */
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id = bpf_get_current_pid_tgid();
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pid = id >> 32;
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tid = (u32)id;
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/* ignore thread exits */
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if (pid != tid)
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return 0;
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/* if we recorded start of the process, calculate lifetime duration */
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start_ts = bpf_map_lookup_elem(&exec_start, &pid);
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if (start_ts)
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duration_ns = bpf_ktime_get_ns() - *start_ts;
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else if (min_duration_ns)
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return 0;
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bpf_map_delete_elem(&exec_start, &pid);
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/* if process didn't live long enough, return early */
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if (min_duration_ns && duration_ns < min_duration_ns)
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return 0;
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/* fill out the sample with data */
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task = (struct task_struct *)bpf_get_current_task();
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e->exit_event = true;
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e->duration_ns = duration_ns;
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e->pid = pid;
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e->ppid = BPF_CORE_READ(task, real_parent, tgid);
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e->exit_code = (BPF_CORE_READ(task, exit_code) >> 8) & 0xff;
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bpf_get_current_comm(&e->comm, sizeof(e->comm));
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/* use perf event output to send data to user-space for post-processing */
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bpf_perf_event_output(ctx, &pe, BPF_F_CURRENT_CPU, e, sizeof(*e));
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return 0;
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}

‎examples/c/bootstrap_legacy.c‎

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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
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/* Copyright (c) 2020 Facebook */
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#include <argp.h>
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#include <signal.h>
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#include <stdio.h>
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#include <time.h>
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#include <sys/resource.h>
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#include <bpf/libbpf.h>
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#include "bootstrap.h"
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#include "bootstrap_legacy.skel.h"
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static struct env {
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bool verbose;
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long min_duration_ms;
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} env;
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const char *argp_program_version = "bootstrap 0.0";
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const char *argp_program_bug_address = "<[email protected]>";
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const char argp_program_doc[] = "BPF bootstrap demo application.\n"
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"\n"
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"It traces process start and exits and shows associated \n"
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"information (filename, process duration, PID and PPID, etc).\n"
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"\n"
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"USAGE: ./bootstrap [-d <min-duration-ms>] [-v]\n";
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static const struct argp_option opts[] = {
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{ "verbose", 'v', NULL, 0, "Verbose debug output" },
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{ "duration", 'd', "DURATION-MS", 0, "Minimum process duration (ms) to report" },
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{},
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};
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static error_t parse_arg(int key, char *arg, struct argp_state *state)
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{
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switch (key) {
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case 'v':
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env.verbose = true;
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break;
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case 'd':
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errno = 0;
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env.min_duration_ms = strtol(arg, NULL, 10);
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if (errno || env.min_duration_ms <= 0) {
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fprintf(stderr, "Invalid duration: %s\n", arg);
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argp_usage(state);
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}
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break;
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case ARGP_KEY_ARG:
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argp_usage(state);
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break;
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default:
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return ARGP_ERR_UNKNOWN;
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}
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return 0;
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}
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static const struct argp argp = {
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.options = opts,
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.parser = parse_arg,
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.doc = argp_program_doc,
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};
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static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
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{
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if (level == LIBBPF_DEBUG && !env.verbose)
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return 0;
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return vfprintf(stderr, format, args);
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}
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static volatile bool exiting = false;
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static void sig_handler(int sig)
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{
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exiting = true;
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}
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static void handle_event(void *ctx, int cpu, void *data, __u32 data_sz)
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{
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const struct event *e = data;
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struct tm *tm;
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char ts[32];
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time_t t;
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time(&t);
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tm = localtime(&t);
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strftime(ts, sizeof(ts), "%H:%M:%S", tm);
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if (e->exit_event) {
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printf("%-8s %-5s %-16s %-7d %-7d [%u]", ts, "EXIT", e->comm, e->pid, e->ppid,
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e->exit_code);
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if (e->duration_ns)
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printf(" (%llums)", e->duration_ns / 1000000);
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printf("\n");
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} else {
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printf("%-8s %-5s %-16s %-7d %-7d %s\n", ts, "EXEC", e->comm, e->pid, e->ppid,
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e->filename);
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}
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}
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int main(int argc, char **argv)
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{
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// struct ring_buffer *rb = NULL;
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struct perf_buffer *pe = NULL;
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struct bootstrap_legacy_bpf *skel;
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int err;
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/* Parse command line arguments */
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err = argp_parse(&argp, argc, argv, 0, NULL, NULL);
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if (err)
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return err;
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/* Set up libbpf errors and debug info callback */
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libbpf_set_print(libbpf_print_fn);
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/* Cleaner handling of Ctrl-C */
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signal(SIGINT, sig_handler);
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signal(SIGTERM, sig_handler);
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/* Load and verify BPF application */
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skel = bootstrap_legacy_bpf__open();
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if (!skel) {
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fprintf(stderr, "Failed to open and load BPF skeleton\n");
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return 1;
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}
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/* Parameterize BPF code with minimum duration parameter */
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skel->rodata->min_duration_ns = env.min_duration_ms * 1000000ULL;
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/* Load & verify BPF programs */
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err = bootstrap_legacy_bpf__load(skel);
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if (err) {
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fprintf(stderr, "Failed to load and verify BPF skeleton\n");
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goto cleanup;
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}
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/* Attach tracepoints */
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err = bootstrap_legacy_bpf__attach(skel);
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if (err) {
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fprintf(stderr, "Failed to attach BPF skeleton\n");
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goto cleanup;
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}
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/* Set up perf buffer polling */
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pe = perf_buffer__new(bpf_map__fd(skel->maps.pe), 8, handle_event, NULL, NULL, NULL);
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if (!pe) {
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err = -1;
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fprintf(stderr, "Failed to create perf event buffer\n");
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goto cleanup;
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}
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/* Process events */
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printf("%-8s %-5s %-16s %-7s %-7s %s\n", "TIME", "EVENT", "COMM", "PID", "PPID",
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"FILENAME/EXIT CODE");
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while (!exiting) {
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err = perf_buffer__poll(pe, 100 /* timeout, ms */);
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/* Ctrl-C will cause -EINTR */
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if (err == -EINTR) {
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err = 0;
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break;
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}
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if (err < 0) {
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printf("Error polling perf buffer: %d\n", err);
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break;
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}
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}
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cleanup:
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/* Clean up */
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perf_buffer__free(pe);
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bootstrap_legacy_bpf__destroy(skel);
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return err < 0 ? -err : 0;
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}

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