235 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2/*3 * sampleip: sample instruction pointer and frequency count in a BPF map.4 *5 * Copyright 2016 Netflix, Inc.6 */7#include <stdio.h>8#include <stdlib.h>9#include <unistd.h>10#include <errno.h>11#include <signal.h>12#include <string.h>13#include <linux/perf_event.h>14#include <linux/ptrace.h>15#include <linux/bpf.h>16#include <bpf/bpf.h>17#include <bpf/libbpf.h>18#include "perf-sys.h"19#include "trace_helpers.h"20 21#define DEFAULT_FREQ 9922#define DEFAULT_SECS 523#define MAX_IPS 819224 25static int map_fd;26static int nr_cpus;27static long _text_addr;28 29static void usage(void)30{31 printf("USAGE: sampleip [-F freq] [duration]\n");32 printf(" -F freq # sample frequency (Hertz), default 99\n");33 printf(" duration # sampling duration (seconds), default 5\n");34}35 36static int sampling_start(int freq, struct bpf_program *prog,37 struct bpf_link *links[])38{39 int i, pmu_fd;40 41 struct perf_event_attr pe_sample_attr = {42 .type = PERF_TYPE_SOFTWARE,43 .freq = 1,44 .sample_period = freq,45 .config = PERF_COUNT_SW_CPU_CLOCK,46 .inherit = 1,47 };48 49 for (i = 0; i < nr_cpus; i++) {50 pmu_fd = sys_perf_event_open(&pe_sample_attr, -1 /* pid */, i,51 -1 /* group_fd */, 0 /* flags */);52 if (pmu_fd < 0) {53 fprintf(stderr, "ERROR: Initializing perf sampling\n");54 return 1;55 }56 links[i] = bpf_program__attach_perf_event(prog, pmu_fd);57 if (libbpf_get_error(links[i])) {58 fprintf(stderr, "ERROR: Attach perf event\n");59 links[i] = NULL;60 close(pmu_fd);61 return 1;62 }63 }64 65 return 0;66}67 68static void sampling_end(struct bpf_link *links[])69{70 int i;71 72 for (i = 0; i < nr_cpus; i++)73 bpf_link__destroy(links[i]);74}75 76struct ipcount {77 __u64 ip;78 __u32 count;79};80 81/* used for sorting */82struct ipcount counts[MAX_IPS];83 84static int count_cmp(const void *p1, const void *p2)85{86 return ((struct ipcount *)p1)->count - ((struct ipcount *)p2)->count;87}88 89static void print_ip_map(int fd)90{91 struct ksym *sym;92 __u64 key, next_key;93 __u32 value;94 int i, max;95 96 printf("%-19s %-32s %s\n", "ADDR", "KSYM", "COUNT");97 98 /* fetch IPs and counts */99 key = 0, i = 0;100 while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {101 bpf_map_lookup_elem(fd, &next_key, &value);102 counts[i].ip = next_key;103 counts[i++].count = value;104 key = next_key;105 }106 max = i;107 108 /* sort and print */109 qsort(counts, max, sizeof(struct ipcount), count_cmp);110 for (i = 0; i < max; i++) {111 if (counts[i].ip > _text_addr) {112 sym = ksym_search(counts[i].ip);113 if (!sym) {114 printf("ksym not found. Is kallsyms loaded?\n");115 continue;116 }117 118 printf("0x%-17llx %-32s %u\n", counts[i].ip, sym->name,119 counts[i].count);120 } else {121 printf("0x%-17llx %-32s %u\n", counts[i].ip, "(user)",122 counts[i].count);123 }124 }125 126 if (max == MAX_IPS) {127 printf("WARNING: IP hash was full (max %d entries); ", max);128 printf("may have dropped samples\n");129 }130}131 132static void int_exit(int sig)133{134 printf("\n");135 print_ip_map(map_fd);136 exit(0);137}138 139int main(int argc, char **argv)140{141 int opt, freq = DEFAULT_FREQ, secs = DEFAULT_SECS, error = 1;142 struct bpf_object *obj = NULL;143 struct bpf_program *prog;144 struct bpf_link **links;145 char filename[256];146 147 /* process arguments */148 while ((opt = getopt(argc, argv, "F:h")) != -1) {149 switch (opt) {150 case 'F':151 freq = atoi(optarg);152 break;153 case 'h':154 default:155 usage();156 return 0;157 }158 }159 if (argc - optind == 1)160 secs = atoi(argv[optind]);161 if (freq == 0 || secs == 0) {162 usage();163 return 1;164 }165 166 /* initialize kernel symbol translation */167 if (load_kallsyms()) {168 fprintf(stderr, "ERROR: loading /proc/kallsyms\n");169 return 2;170 }171 172 /* used to determine whether the address is kernel space */173 _text_addr = ksym_get_addr("_text");174 if (!_text_addr) {175 fprintf(stderr, "ERROR: no '_text' in /proc/kallsyms\n");176 return 3;177 }178 179 /* create perf FDs for each CPU */180 nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);181 links = calloc(nr_cpus, sizeof(struct bpf_link *));182 if (!links) {183 fprintf(stderr, "ERROR: malloc of links\n");184 goto cleanup;185 }186 187 snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);188 obj = bpf_object__open_file(filename, NULL);189 if (libbpf_get_error(obj)) {190 fprintf(stderr, "ERROR: opening BPF object file failed\n");191 obj = NULL;192 goto cleanup;193 }194 195 prog = bpf_object__find_program_by_name(obj, "do_sample");196 if (!prog) {197 fprintf(stderr, "ERROR: finding a prog in obj file failed\n");198 goto cleanup;199 }200 201 /* load BPF program */202 if (bpf_object__load(obj)) {203 fprintf(stderr, "ERROR: loading BPF object file failed\n");204 goto cleanup;205 }206 207 map_fd = bpf_object__find_map_fd_by_name(obj, "ip_map");208 if (map_fd < 0) {209 fprintf(stderr, "ERROR: finding a map in obj file failed\n");210 goto cleanup;211 }212 213 signal(SIGINT, int_exit);214 signal(SIGTERM, int_exit);215 216 /* do sampling */217 printf("Sampling at %d Hertz for %d seconds. Ctrl-C also ends.\n",218 freq, secs);219 if (sampling_start(freq, prog, links) != 0)220 goto cleanup;221 222 sleep(secs);223 error = 0;224 225cleanup:226 sampling_end(links);227 /* output sample counts */228 if (!error)229 print_ip_map(map_fd);230 231 free(links);232 bpf_object__close(obj);233 return error;234}235