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}
235