summaryrefslogtreecommitdiffstats
path: root/samples/bpf/bpf_load.c
blob: 38dac5a53b518bc71743b32a06ad39391c60066b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libelf.h>
#include <gelf.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/perf_event.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <poll.h>
#include "libbpf.h"
#include "bpf_helpers.h"
#include "bpf_load.h"

#define DEBUGFS "/sys/kernel/debug/tracing/"

static char license[128];
static int kern_version;
static bool processed_sec[128];
int map_fd[MAX_MAPS];
int prog_fd[MAX_PROGS];
int event_fd[MAX_PROGS];
int prog_cnt;

static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
{
	bool is_socket = strncmp(event, "socket", 6) == 0;
	bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
	bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
	enum bpf_prog_type prog_type;
	char buf[256];
	int fd, efd, err, id;
	struct perf_event_attr attr = {};

	attr.type = PERF_TYPE_TRACEPOINT;
	attr.sample_type = PERF_SAMPLE_RAW;
	attr.sample_period = 1;
	attr.wakeup_events = 1;

	if (is_socket) {
		prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
	} else if (is_kprobe || is_kretprobe) {
		prog_type = BPF_PROG_TYPE_KPROBE;
	} else {
		printf("Unknown event '%s'\n", event);
		return -1;
	}

	if (is_kprobe || is_kretprobe) {
		if (is_kprobe)
			event += 7;
		else
			event += 10;

		snprintf(buf, sizeof(buf),
			 "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
			 is_kprobe ? 'p' : 'r', event, event);
		err = system(buf);
		if (err < 0) {
			printf("failed to create kprobe '%s' error '%s'\n",
			       event, strerror(errno));
			return -1;
		}
	}

	fd = bpf_prog_load(prog_type, prog, size, license, kern_version);

	if (fd < 0) {
		printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
		return -1;
	}

	prog_fd[prog_cnt++] = fd;

	if (is_socket)
		return 0;

	strcpy(buf, DEBUGFS);
	strcat(buf, "events/kprobes/");
	strcat(buf, event);
	strcat(buf, "/id");

	efd = open(buf, O_RDONLY, 0);
	if (efd < 0) {
		printf("failed to open event %s\n", event);
		return -1;
	}

	err = read(efd, buf, sizeof(buf));
	if (err < 0 || err >= sizeof(buf)) {
		printf("read from '%s' failed '%s'\n", event, strerror(errno));
		return -1;
	}

	close(efd);

	buf[err] = 0;
	id = atoi(buf);
	attr.config = id;

	efd = perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
	if (efd < 0) {
		printf("event %d fd %d err %s\n", id, efd, strerror(errno));
		return -1;
	}
	event_fd[prog_cnt - 1] = efd;
	ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
	ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);

	return 0;
}

static int load_maps(struct bpf_map_def *maps, int len)
{
	int i;

	for (i = 0; i < len / sizeof(struct bpf_map_def); i++) {

		map_fd[i] = bpf_create_map(maps[i].type,
					   maps[i].key_size,
					   maps[i].value_size,
					   maps[i].max_entries);
		if (map_fd[i] < 0)
			return 1;
	}
	return 0;
}

static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
		   GElf_Shdr *shdr, Elf_Data **data)
{
	Elf_Scn *scn;

	scn = elf_getscn(elf, i);
	if (!scn)
		return 1;

	if (gelf_getshdr(scn, shdr) != shdr)
		return 2;

	*shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
	if (!*shname || !shdr->sh_size)
		return 3;

	*data = elf_getdata(scn, 0);
	if (!*data || elf_getdata(scn, *data) != NULL)
		return 4;

	return 0;
}

static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
				GElf_Shdr *shdr, struct bpf_insn *insn)
{
	int i, nrels;

	nrels = shdr->sh_size / shdr->sh_entsize;

	for (i = 0; i < nrels; i++) {
		GElf_Sym sym;
		GElf_Rel rel;
		unsigned int insn_idx;

		gelf_getrel(data, i, &rel);

		insn_idx = rel.r_offset / sizeof(struct bpf_insn);

		gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);

		if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
			printf("invalid relo for insn[%d].code 0x%x\n",
			       insn_idx, insn[insn_idx].code);
			return 1;
		}
		insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
		insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)];
	}

	return 0;
}

int load_bpf_file(char *path)
{
	int fd, i;
	Elf *elf;
	GElf_Ehdr ehdr;
	GElf_Shdr shdr, shdr_prog;
	Elf_Data *data, *data_prog, *symbols = NULL;
	char *shname, *shname_prog;

	if (elf_version(EV_CURRENT) == EV_NONE)
		return 1;

	fd = open(path, O_RDONLY, 0);
	if (fd < 0)
		return 1;

	elf = elf_begin(fd, ELF_C_READ, NULL);

	if (!elf)
		return 1;

	if (gelf_getehdr(elf, &ehdr) != &ehdr)
		return 1;

	/* clear all kprobes */
	i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");

	/* scan over all elf sections to get license and map info */
	for (i = 1; i < ehdr.e_shnum; i++) {

		if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
			continue;

		if (0) /* helpful for llvm debugging */
			printf("section %d:%s data %p size %zd link %d flags %d\n",
			       i, shname, data->d_buf, data->d_size,
			       shdr.sh_link, (int) shdr.sh_flags);

		if (strcmp(shname, "license") == 0) {
			processed_sec[i] = true;
			memcpy(license, data->d_buf, data->d_size);
		} else if (strcmp(shname, "version") == 0) {
			processed_sec[i] = true;
			if (data->d_size != sizeof(int)) {
				printf("invalid size of version section %zd\n",
				       data->d_size);
				return 1;
			}
			memcpy(&kern_version, data->d_buf, sizeof(int));
		} else if (strcmp(shname, "maps") == 0) {
			processed_sec[i] = true;
			if (load_maps(data->d_buf, data->d_size))
				return 1;
		} else if (shdr.sh_type == SHT_SYMTAB) {
			symbols = data;
		}
	}

	/* load programs that need map fixup (relocations) */
	for (i = 1; i < ehdr.e_shnum; i++) {

		if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
			continue;
		if (shdr.sh_type == SHT_REL) {
			struct bpf_insn *insns;

			if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
				    &shdr_prog, &data_prog))
				continue;

			insns = (struct bpf_insn *) data_prog->d_buf;

			processed_sec[shdr.sh_info] = true;
			processed_sec[i] = true;

			if (parse_relo_and_apply(data, symbols, &shdr, insns))
				continue;

			if (memcmp(shname_prog, "kprobe/", 7) == 0 ||
			    memcmp(shname_prog, "kretprobe/", 10) == 0 ||
			    memcmp(shname_prog, "socket", 6) == 0)
				load_and_attach(shname_prog, insns, data_prog->d_size);
		}
	}

	/* load programs that don't use maps */
	for (i = 1; i < ehdr.e_shnum; i++) {

		if (processed_sec[i])
			continue;

		if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
			continue;

		if (memcmp(shname, "kprobe/", 7) == 0 ||
		    memcmp(shname, "kretprobe/", 10) == 0 ||
		    memcmp(shname, "socket", 6) == 0)
			load_and_attach(shname, data->d_buf, data->d_size);
	}

	close(fd);
	return 0;
}

void read_trace_pipe(void)
{
	int trace_fd;

	trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
	if (trace_fd < 0)
		return;

	while (1) {
		static char buf[4096];
		ssize_t sz;

		sz = read(trace_fd, buf, sizeof(buf));
		if (sz > 0) {
			buf[sz] = 0;
			puts(buf);
		}
	}
}