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Macro PAGE_OFFSET(0xffff880000000000) in sampleip_user.c is inaccurate, for example, in aarch64 architecture, this value depends on the CONFIG_ARM64_VA_BITS compilation configuration, this value defaults to 48, the corresponding PAGE_OFFSET is 0xffff800000000000, if we use the value defined in sampleip_user.c, then all KSYMs obtained by sampleip are (user) Symbol error due to PAGE_OFFSET error: $ sudo ./sampleip 1 Sampling at 99 Hertz for 1 seconds. Ctrl-C also ends. ADDR KSYM COUNT 0xffff80000810ceb8 (user) 1 0xffffb28ec880 (user) 1 0xffff8000080c82b8 (user) 1 0xffffb23fed24 (user) 1 0xffffb28944fc (user) 1 0xffff8000084628bc (user) 1 0xffffb2a935c0 (user) 1 0xffff80000844677c (user) 1 0xffff80000857a3a4 (user) 1 ... A few examples of addresses in the CONFIG_ARM64_VA_BITS=48 environment in the aarch64 environment: $ sudo head /proc/kallsyms ffff8000080a0000 T _text ffff8000080b0000 t gic_handle_irq ffff8000080b0000 T _stext ffff8000080b0000 T __irqentry_text_start ffff8000080b00b0 t gic_handle_irq ffff8000080b0230 t gic_handle_irq ffff8000080b03b4 T __irqentry_text_end ffff8000080b03b8 T __softirqentry_text_start ffff8000080b03c0 T __do_softirq ffff8000080b0718 T __entry_text_start We just need to replace the PAGE_OFFSET with the address _text in /proc/kallsyms to solve this problem: $ sudo ./sampleip 1 Sampling at 99 Hertz for 1 seconds. Ctrl-C also ends. ADDR KSYM COUNT 0xffffb2892ab0 (user) 1 0xffffb2b1edfc (user) 1 0xffff800008462834 __arm64_sys_ppoll 1 0xffff8000084b87f4 eventfd_read 1 0xffffb28e6788 (user) 1 0xffff8000081e96d8 rcu_all_qs 1 0xffffb2ada878 (user) 1 ... Signed-off-by: Rong Tao <rongtao@cestc.cn> Link: https://lore.kernel.org/r/tencent_A0E82E0BEE925285F8156D540731DF805F05@qq.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
235 lines
5.0 KiB
C
235 lines
5.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* sampleip: sample instruction pointer and frequency count in a BPF map.
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*
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* Copyright 2016 Netflix, Inc.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <signal.h>
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#include <string.h>
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#include <linux/perf_event.h>
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#include <linux/ptrace.h>
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#include <linux/bpf.h>
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#include <bpf/bpf.h>
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#include <bpf/libbpf.h>
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#include "perf-sys.h"
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#include "trace_helpers.h"
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#define DEFAULT_FREQ 99
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#define DEFAULT_SECS 5
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#define MAX_IPS 8192
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static int map_fd;
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static int nr_cpus;
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static long _text_addr;
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static void usage(void)
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{
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printf("USAGE: sampleip [-F freq] [duration]\n");
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printf(" -F freq # sample frequency (Hertz), default 99\n");
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printf(" duration # sampling duration (seconds), default 5\n");
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}
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static int sampling_start(int freq, struct bpf_program *prog,
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struct bpf_link *links[])
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{
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int i, pmu_fd;
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struct perf_event_attr pe_sample_attr = {
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.type = PERF_TYPE_SOFTWARE,
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.freq = 1,
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.sample_period = freq,
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.config = PERF_COUNT_SW_CPU_CLOCK,
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.inherit = 1,
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};
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for (i = 0; i < nr_cpus; i++) {
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pmu_fd = sys_perf_event_open(&pe_sample_attr, -1 /* pid */, i,
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-1 /* group_fd */, 0 /* flags */);
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if (pmu_fd < 0) {
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fprintf(stderr, "ERROR: Initializing perf sampling\n");
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return 1;
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}
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links[i] = bpf_program__attach_perf_event(prog, pmu_fd);
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if (libbpf_get_error(links[i])) {
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fprintf(stderr, "ERROR: Attach perf event\n");
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links[i] = NULL;
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close(pmu_fd);
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return 1;
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}
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}
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return 0;
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}
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static void sampling_end(struct bpf_link *links[])
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{
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int i;
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for (i = 0; i < nr_cpus; i++)
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bpf_link__destroy(links[i]);
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}
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struct ipcount {
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__u64 ip;
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__u32 count;
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};
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/* used for sorting */
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struct ipcount counts[MAX_IPS];
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static int count_cmp(const void *p1, const void *p2)
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{
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return ((struct ipcount *)p1)->count - ((struct ipcount *)p2)->count;
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}
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static void print_ip_map(int fd)
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{
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struct ksym *sym;
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__u64 key, next_key;
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__u32 value;
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int i, max;
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printf("%-19s %-32s %s\n", "ADDR", "KSYM", "COUNT");
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/* fetch IPs and counts */
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key = 0, i = 0;
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while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {
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bpf_map_lookup_elem(fd, &next_key, &value);
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counts[i].ip = next_key;
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counts[i++].count = value;
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key = next_key;
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}
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max = i;
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/* sort and print */
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qsort(counts, max, sizeof(struct ipcount), count_cmp);
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for (i = 0; i < max; i++) {
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if (counts[i].ip > _text_addr) {
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sym = ksym_search(counts[i].ip);
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if (!sym) {
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printf("ksym not found. Is kallsyms loaded?\n");
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continue;
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}
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printf("0x%-17llx %-32s %u\n", counts[i].ip, sym->name,
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counts[i].count);
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} else {
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printf("0x%-17llx %-32s %u\n", counts[i].ip, "(user)",
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counts[i].count);
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}
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}
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if (max == MAX_IPS) {
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printf("WARNING: IP hash was full (max %d entries); ", max);
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printf("may have dropped samples\n");
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}
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}
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static void int_exit(int sig)
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{
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printf("\n");
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print_ip_map(map_fd);
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exit(0);
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}
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int main(int argc, char **argv)
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{
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int opt, freq = DEFAULT_FREQ, secs = DEFAULT_SECS, error = 1;
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struct bpf_object *obj = NULL;
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struct bpf_program *prog;
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struct bpf_link **links;
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char filename[256];
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/* process arguments */
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while ((opt = getopt(argc, argv, "F:h")) != -1) {
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switch (opt) {
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case 'F':
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freq = atoi(optarg);
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break;
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case 'h':
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default:
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usage();
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return 0;
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}
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}
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if (argc - optind == 1)
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secs = atoi(argv[optind]);
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if (freq == 0 || secs == 0) {
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usage();
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return 1;
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}
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/* initialize kernel symbol translation */
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if (load_kallsyms()) {
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fprintf(stderr, "ERROR: loading /proc/kallsyms\n");
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return 2;
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}
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/* used to determine whether the address is kernel space */
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_text_addr = ksym_get_addr("_text");
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if (!_text_addr) {
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fprintf(stderr, "ERROR: no '_text' in /proc/kallsyms\n");
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return 3;
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}
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/* create perf FDs for each CPU */
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nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
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links = calloc(nr_cpus, sizeof(struct bpf_link *));
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if (!links) {
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fprintf(stderr, "ERROR: malloc of links\n");
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goto cleanup;
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}
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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obj = bpf_object__open_file(filename, NULL);
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if (libbpf_get_error(obj)) {
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fprintf(stderr, "ERROR: opening BPF object file failed\n");
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obj = NULL;
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goto cleanup;
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}
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prog = bpf_object__find_program_by_name(obj, "do_sample");
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if (!prog) {
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fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
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goto cleanup;
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}
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/* load BPF program */
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if (bpf_object__load(obj)) {
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fprintf(stderr, "ERROR: loading BPF object file failed\n");
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goto cleanup;
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}
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map_fd = bpf_object__find_map_fd_by_name(obj, "ip_map");
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if (map_fd < 0) {
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fprintf(stderr, "ERROR: finding a map in obj file failed\n");
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goto cleanup;
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}
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signal(SIGINT, int_exit);
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signal(SIGTERM, int_exit);
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/* do sampling */
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printf("Sampling at %d Hertz for %d seconds. Ctrl-C also ends.\n",
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freq, secs);
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if (sampling_start(freq, prog, links) != 0)
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goto cleanup;
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sleep(secs);
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error = 0;
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cleanup:
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sampling_end(links);
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/* output sample counts */
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if (!error)
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print_ip_map(map_fd);
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free(links);
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bpf_object__close(obj);
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return error;
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}
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