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1// SPDX-License-Identifier: GPL-2.0-only
2/*
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 99
22#define DEFAULT_SECS 5
23#define MAX_IPS 8192
24
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}