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Linux/samples/bpf/bpf_load.c

  1 #include <stdio.h>
  2 #include <sys/types.h>
  3 #include <sys/stat.h>
  4 #include <fcntl.h>
  5 #include <libelf.h>
  6 #include <gelf.h>
  7 #include <errno.h>
  8 #include <unistd.h>
  9 #include <string.h>
 10 #include <stdbool.h>
 11 #include <stdlib.h>
 12 #include <linux/bpf.h>
 13 #include <linux/filter.h>
 14 #include <linux/perf_event.h>
 15 #include <linux/netlink.h>
 16 #include <linux/rtnetlink.h>
 17 #include <sys/types.h>
 18 #include <sys/socket.h>
 19 #include <sys/syscall.h>
 20 #include <sys/ioctl.h>
 21 #include <sys/mman.h>
 22 #include <poll.h>
 23 #include <ctype.h>
 24 #include "libbpf.h"
 25 #include "bpf_load.h"
 26 #include "perf-sys.h"
 27 
 28 #define DEBUGFS "/sys/kernel/debug/tracing/"
 29 
 30 static char license[128];
 31 static int kern_version;
 32 static bool processed_sec[128];
 33 char bpf_log_buf[BPF_LOG_BUF_SIZE];
 34 int map_fd[MAX_MAPS];
 35 int prog_fd[MAX_PROGS];
 36 int event_fd[MAX_PROGS];
 37 int prog_cnt;
 38 int prog_array_fd = -1;
 39 
 40 struct bpf_map_def {
 41         unsigned int type;
 42         unsigned int key_size;
 43         unsigned int value_size;
 44         unsigned int max_entries;
 45         unsigned int map_flags;
 46 };
 47 
 48 static int populate_prog_array(const char *event, int prog_fd)
 49 {
 50         int ind = atoi(event), err;
 51 
 52         err = bpf_map_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY);
 53         if (err < 0) {
 54                 printf("failed to store prog_fd in prog_array\n");
 55                 return -1;
 56         }
 57         return 0;
 58 }
 59 
 60 static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
 61 {
 62         bool is_socket = strncmp(event, "socket", 6) == 0;
 63         bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
 64         bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
 65         bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0;
 66         bool is_xdp = strncmp(event, "xdp", 3) == 0;
 67         bool is_perf_event = strncmp(event, "perf_event", 10) == 0;
 68         bool is_cgroup_skb = strncmp(event, "cgroup/skb", 10) == 0;
 69         bool is_cgroup_sk = strncmp(event, "cgroup/sock", 11) == 0;
 70         size_t insns_cnt = size / sizeof(struct bpf_insn);
 71         enum bpf_prog_type prog_type;
 72         char buf[256];
 73         int fd, efd, err, id;
 74         struct perf_event_attr attr = {};
 75 
 76         attr.type = PERF_TYPE_TRACEPOINT;
 77         attr.sample_type = PERF_SAMPLE_RAW;
 78         attr.sample_period = 1;
 79         attr.wakeup_events = 1;
 80 
 81         if (is_socket) {
 82                 prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
 83         } else if (is_kprobe || is_kretprobe) {
 84                 prog_type = BPF_PROG_TYPE_KPROBE;
 85         } else if (is_tracepoint) {
 86                 prog_type = BPF_PROG_TYPE_TRACEPOINT;
 87         } else if (is_xdp) {
 88                 prog_type = BPF_PROG_TYPE_XDP;
 89         } else if (is_perf_event) {
 90                 prog_type = BPF_PROG_TYPE_PERF_EVENT;
 91         } else if (is_cgroup_skb) {
 92                 prog_type = BPF_PROG_TYPE_CGROUP_SKB;
 93         } else if (is_cgroup_sk) {
 94                 prog_type = BPF_PROG_TYPE_CGROUP_SOCK;
 95         } else {
 96                 printf("Unknown event '%s'\n", event);
 97                 return -1;
 98         }
 99 
100         fd = bpf_load_program(prog_type, prog, insns_cnt, license, kern_version,
101                               bpf_log_buf, BPF_LOG_BUF_SIZE);
102         if (fd < 0) {
103                 printf("bpf_load_program() err=%d\n%s", errno, bpf_log_buf);
104                 return -1;
105         }
106 
107         prog_fd[prog_cnt++] = fd;
108 
109         if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk)
110                 return 0;
111 
112         if (is_socket) {
113                 event += 6;
114                 if (*event != '/')
115                         return 0;
116                 event++;
117                 if (!isdigit(*event)) {
118                         printf("invalid prog number\n");
119                         return -1;
120                 }
121                 return populate_prog_array(event, fd);
122         }
123 
124         if (is_kprobe || is_kretprobe) {
125                 if (is_kprobe)
126                         event += 7;
127                 else
128                         event += 10;
129 
130                 if (*event == 0) {
131                         printf("event name cannot be empty\n");
132                         return -1;
133                 }
134 
135                 if (isdigit(*event))
136                         return populate_prog_array(event, fd);
137 
138                 snprintf(buf, sizeof(buf),
139                          "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
140                          is_kprobe ? 'p' : 'r', event, event);
141                 err = system(buf);
142                 if (err < 0) {
143                         printf("failed to create kprobe '%s' error '%s'\n",
144                                event, strerror(errno));
145                         return -1;
146                 }
147 
148                 strcpy(buf, DEBUGFS);
149                 strcat(buf, "events/kprobes/");
150                 strcat(buf, event);
151                 strcat(buf, "/id");
152         } else if (is_tracepoint) {
153                 event += 11;
154 
155                 if (*event == 0) {
156                         printf("event name cannot be empty\n");
157                         return -1;
158                 }
159                 strcpy(buf, DEBUGFS);
160                 strcat(buf, "events/");
161                 strcat(buf, event);
162                 strcat(buf, "/id");
163         }
164 
165         efd = open(buf, O_RDONLY, 0);
166         if (efd < 0) {
167                 printf("failed to open event %s\n", event);
168                 return -1;
169         }
170 
171         err = read(efd, buf, sizeof(buf));
172         if (err < 0 || err >= sizeof(buf)) {
173                 printf("read from '%s' failed '%s'\n", event, strerror(errno));
174                 return -1;
175         }
176 
177         close(efd);
178 
179         buf[err] = 0;
180         id = atoi(buf);
181         attr.config = id;
182 
183         efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
184         if (efd < 0) {
185                 printf("event %d fd %d err %s\n", id, efd, strerror(errno));
186                 return -1;
187         }
188         event_fd[prog_cnt - 1] = efd;
189         ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
190         ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
191 
192         return 0;
193 }
194 
195 static int load_maps(struct bpf_map_def *maps, int len)
196 {
197         int i;
198 
199         for (i = 0; i < len / sizeof(struct bpf_map_def); i++) {
200 
201                 map_fd[i] = bpf_create_map(maps[i].type,
202                                            maps[i].key_size,
203                                            maps[i].value_size,
204                                            maps[i].max_entries,
205                                            maps[i].map_flags);
206                 if (map_fd[i] < 0) {
207                         printf("failed to create a map: %d %s\n",
208                                errno, strerror(errno));
209                         return 1;
210                 }
211 
212                 if (maps[i].type == BPF_MAP_TYPE_PROG_ARRAY)
213                         prog_array_fd = map_fd[i];
214         }
215         return 0;
216 }
217 
218 static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
219                    GElf_Shdr *shdr, Elf_Data **data)
220 {
221         Elf_Scn *scn;
222 
223         scn = elf_getscn(elf, i);
224         if (!scn)
225                 return 1;
226 
227         if (gelf_getshdr(scn, shdr) != shdr)
228                 return 2;
229 
230         *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
231         if (!*shname || !shdr->sh_size)
232                 return 3;
233 
234         *data = elf_getdata(scn, 0);
235         if (!*data || elf_getdata(scn, *data) != NULL)
236                 return 4;
237 
238         return 0;
239 }
240 
241 static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
242                                 GElf_Shdr *shdr, struct bpf_insn *insn)
243 {
244         int i, nrels;
245 
246         nrels = shdr->sh_size / shdr->sh_entsize;
247 
248         for (i = 0; i < nrels; i++) {
249                 GElf_Sym sym;
250                 GElf_Rel rel;
251                 unsigned int insn_idx;
252 
253                 gelf_getrel(data, i, &rel);
254 
255                 insn_idx = rel.r_offset / sizeof(struct bpf_insn);
256 
257                 gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
258 
259                 if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
260                         printf("invalid relo for insn[%d].code 0x%x\n",
261                                insn_idx, insn[insn_idx].code);
262                         return 1;
263                 }
264                 insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
265                 insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)];
266         }
267 
268         return 0;
269 }
270 
271 int load_bpf_file(char *path)
272 {
273         int fd, i;
274         Elf *elf;
275         GElf_Ehdr ehdr;
276         GElf_Shdr shdr, shdr_prog;
277         Elf_Data *data, *data_prog, *symbols = NULL;
278         char *shname, *shname_prog;
279 
280         if (elf_version(EV_CURRENT) == EV_NONE)
281                 return 1;
282 
283         fd = open(path, O_RDONLY, 0);
284         if (fd < 0)
285                 return 1;
286 
287         elf = elf_begin(fd, ELF_C_READ, NULL);
288 
289         if (!elf)
290                 return 1;
291 
292         if (gelf_getehdr(elf, &ehdr) != &ehdr)
293                 return 1;
294 
295         /* clear all kprobes */
296         i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
297 
298         /* scan over all elf sections to get license and map info */
299         for (i = 1; i < ehdr.e_shnum; i++) {
300 
301                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
302                         continue;
303 
304                 if (0) /* helpful for llvm debugging */
305                         printf("section %d:%s data %p size %zd link %d flags %d\n",
306                                i, shname, data->d_buf, data->d_size,
307                                shdr.sh_link, (int) shdr.sh_flags);
308 
309                 if (strcmp(shname, "license") == 0) {
310                         processed_sec[i] = true;
311                         memcpy(license, data->d_buf, data->d_size);
312                 } else if (strcmp(shname, "version") == 0) {
313                         processed_sec[i] = true;
314                         if (data->d_size != sizeof(int)) {
315                                 printf("invalid size of version section %zd\n",
316                                        data->d_size);
317                                 return 1;
318                         }
319                         memcpy(&kern_version, data->d_buf, sizeof(int));
320                 } else if (strcmp(shname, "maps") == 0) {
321                         processed_sec[i] = true;
322                         if (load_maps(data->d_buf, data->d_size))
323                                 return 1;
324                 } else if (shdr.sh_type == SHT_SYMTAB) {
325                         symbols = data;
326                 }
327         }
328 
329         /* load programs that need map fixup (relocations) */
330         for (i = 1; i < ehdr.e_shnum; i++) {
331 
332                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
333                         continue;
334                 if (shdr.sh_type == SHT_REL) {
335                         struct bpf_insn *insns;
336 
337                         if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
338                                     &shdr_prog, &data_prog))
339                                 continue;
340 
341                         if (shdr_prog.sh_type != SHT_PROGBITS ||
342                             !(shdr_prog.sh_flags & SHF_EXECINSTR))
343                                 continue;
344 
345                         insns = (struct bpf_insn *) data_prog->d_buf;
346 
347                         processed_sec[shdr.sh_info] = true;
348                         processed_sec[i] = true;
349 
350                         if (parse_relo_and_apply(data, symbols, &shdr, insns))
351                                 continue;
352 
353                         if (memcmp(shname_prog, "kprobe/", 7) == 0 ||
354                             memcmp(shname_prog, "kretprobe/", 10) == 0 ||
355                             memcmp(shname_prog, "tracepoint/", 11) == 0 ||
356                             memcmp(shname_prog, "xdp", 3) == 0 ||
357                             memcmp(shname_prog, "perf_event", 10) == 0 ||
358                             memcmp(shname_prog, "socket", 6) == 0 ||
359                             memcmp(shname_prog, "cgroup/", 7) == 0)
360                                 load_and_attach(shname_prog, insns, data_prog->d_size);
361                 }
362         }
363 
364         /* load programs that don't use maps */
365         for (i = 1; i < ehdr.e_shnum; i++) {
366 
367                 if (processed_sec[i])
368                         continue;
369 
370                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
371                         continue;
372 
373                 if (memcmp(shname, "kprobe/", 7) == 0 ||
374                     memcmp(shname, "kretprobe/", 10) == 0 ||
375                     memcmp(shname, "tracepoint/", 11) == 0 ||
376                     memcmp(shname, "xdp", 3) == 0 ||
377                     memcmp(shname, "perf_event", 10) == 0 ||
378                     memcmp(shname, "socket", 6) == 0 ||
379                     memcmp(shname, "cgroup/", 7) == 0)
380                         load_and_attach(shname, data->d_buf, data->d_size);
381         }
382 
383         close(fd);
384         return 0;
385 }
386 
387 void read_trace_pipe(void)
388 {
389         int trace_fd;
390 
391         trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
392         if (trace_fd < 0)
393                 return;
394 
395         while (1) {
396                 static char buf[4096];
397                 ssize_t sz;
398 
399                 sz = read(trace_fd, buf, sizeof(buf));
400                 if (sz > 0) {
401                         buf[sz] = 0;
402                         puts(buf);
403                 }
404         }
405 }
406 
407 #define MAX_SYMS 300000
408 static struct ksym syms[MAX_SYMS];
409 static int sym_cnt;
410 
411 static int ksym_cmp(const void *p1, const void *p2)
412 {
413         return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
414 }
415 
416 int load_kallsyms(void)
417 {
418         FILE *f = fopen("/proc/kallsyms", "r");
419         char func[256], buf[256];
420         char symbol;
421         void *addr;
422         int i = 0;
423 
424         if (!f)
425                 return -ENOENT;
426 
427         while (!feof(f)) {
428                 if (!fgets(buf, sizeof(buf), f))
429                         break;
430                 if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
431                         break;
432                 if (!addr)
433                         continue;
434                 syms[i].addr = (long) addr;
435                 syms[i].name = strdup(func);
436                 i++;
437         }
438         sym_cnt = i;
439         qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
440         return 0;
441 }
442 
443 struct ksym *ksym_search(long key)
444 {
445         int start = 0, end = sym_cnt;
446         int result;
447 
448         while (start < end) {
449                 size_t mid = start + (end - start) / 2;
450 
451                 result = key - syms[mid].addr;
452                 if (result < 0)
453                         end = mid;
454                 else if (result > 0)
455                         start = mid + 1;
456                 else
457                         return &syms[mid];
458         }
459 
460         if (start >= 1 && syms[start - 1].addr < key &&
461             key < syms[start].addr)
462                 /* valid ksym */
463                 return &syms[start - 1];
464 
465         /* out of range. return _stext */
466         return &syms[0];
467 }
468 
469 int set_link_xdp_fd(int ifindex, int fd)
470 {
471         struct sockaddr_nl sa;
472         int sock, seq = 0, len, ret = -1;
473         char buf[4096];
474         struct nlattr *nla, *nla_xdp;
475         struct {
476                 struct nlmsghdr  nh;
477                 struct ifinfomsg ifinfo;
478                 char             attrbuf[64];
479         } req;
480         struct nlmsghdr *nh;
481         struct nlmsgerr *err;
482 
483         memset(&sa, 0, sizeof(sa));
484         sa.nl_family = AF_NETLINK;
485 
486         sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
487         if (sock < 0) {
488                 printf("open netlink socket: %s\n", strerror(errno));
489                 return -1;
490         }
491 
492         if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
493                 printf("bind to netlink: %s\n", strerror(errno));
494                 goto cleanup;
495         }
496 
497         memset(&req, 0, sizeof(req));
498         req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
499         req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
500         req.nh.nlmsg_type = RTM_SETLINK;
501         req.nh.nlmsg_pid = 0;
502         req.nh.nlmsg_seq = ++seq;
503         req.ifinfo.ifi_family = AF_UNSPEC;
504         req.ifinfo.ifi_index = ifindex;
505         nla = (struct nlattr *)(((char *)&req)
506                                 + NLMSG_ALIGN(req.nh.nlmsg_len));
507         nla->nla_type = NLA_F_NESTED | 43/*IFLA_XDP*/;
508 
509         nla_xdp = (struct nlattr *)((char *)nla + NLA_HDRLEN);
510         nla_xdp->nla_type = 1/*IFLA_XDP_FD*/;
511         nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
512         memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
513         nla->nla_len = NLA_HDRLEN + nla_xdp->nla_len;
514 
515         req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
516 
517         if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
518                 printf("send to netlink: %s\n", strerror(errno));
519                 goto cleanup;
520         }
521 
522         len = recv(sock, buf, sizeof(buf), 0);
523         if (len < 0) {
524                 printf("recv from netlink: %s\n", strerror(errno));
525                 goto cleanup;
526         }
527 
528         for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
529              nh = NLMSG_NEXT(nh, len)) {
530                 if (nh->nlmsg_pid != getpid()) {
531                         printf("Wrong pid %d, expected %d\n",
532                                nh->nlmsg_pid, getpid());
533                         goto cleanup;
534                 }
535                 if (nh->nlmsg_seq != seq) {
536                         printf("Wrong seq %d, expected %d\n",
537                                nh->nlmsg_seq, seq);
538                         goto cleanup;
539                 }
540                 switch (nh->nlmsg_type) {
541                 case NLMSG_ERROR:
542                         err = (struct nlmsgerr *)NLMSG_DATA(nh);
543                         if (!err->error)
544                                 continue;
545                         printf("nlmsg error %s\n", strerror(-err->error));
546                         goto cleanup;
547                 case NLMSG_DONE:
548                         break;
549                 }
550         }
551 
552         ret = 0;
553 
554 cleanup:
555         close(sock);
556         return ret;
557 }
558 

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