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 <sys/syscall.h>
  16 #include <sys/ioctl.h>
  17 #include <sys/mman.h>
  18 #include <poll.h>
  19 #include <ctype.h>
  20 #include "libbpf.h"
  21 #include "bpf_helpers.h"
  22 #include "bpf_load.h"
  23
  24 #define DEBUGFS "/sys/kernel/debug/tracing/"
  25
  26 static char license[128];
  27 static int kern_version;
  28 static bool processed_sec[128];
  29 int map_fd[MAX_MAPS];
  30 int prog_fd[MAX_PROGS];
  31 int event_fd[MAX_PROGS];
  32 int prog_cnt;
  33 int prog_array_fd = -1;
  34
  35 static int populate_prog_array(const char *event, int prog_fd)
  36 {
  37         int ind = atoi(event), err;
  38
  39         err = bpf_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY);
  40         if (err < 0) {
  41                 printf("failed to store prog_fd in prog_array\n");
  42                 return -1;
  43         }
  44         return 0;
  45 }
  46
  47 static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
  48 {
  49         bool is_socket = strncmp(event, "socket", 6) == 0;
  50         bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
  51         bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
  52         enum bpf_prog_type prog_type;
  53         char buf[256];
  54         int fd, efd, err, id;
  55         struct perf_event_attr attr = {};
  56
  57         attr.type = PERF_TYPE_TRACEPOINT;
  58         attr.sample_type = PERF_SAMPLE_RAW;
  59         attr.sample_period = 1;
  60         attr.wakeup_events = 1;
  61
  62         if (is_socket) {
  63                 prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
  64         } else if (is_kprobe || is_kretprobe) {
  65                 prog_type = BPF_PROG_TYPE_KPROBE;
  66         } else {
  67                 printf("Unknown event '%s'\n", event);
  68                 return -1;
  69         }
  70
  71         fd = bpf_prog_load(prog_type, prog, size, license, kern_version);
  72         if (fd < 0) {
  73                 printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
  74                 return -1;
  75         }
  76
  77         prog_fd[prog_cnt++] = fd;
  78
  79         if (is_socket) {
  80                 event += 6;
  81                 if (*event != '/')
  82                         return 0;
  83                 event++;
  84                 if (!isdigit(*event)) {
  85                         printf("invalid prog number\n");
  86                         return -1;
  87                 }
  88                 return populate_prog_array(event, fd);
  89         }
  90
  91         if (is_kprobe || is_kretprobe) {
  92                 if (is_kprobe)
  93                         event += 7;
  94                 else
  95                         event += 10;
  96
  97                 if (*event == 0) {
  98                         printf("event name cannot be empty\n");
  99                         return -1;
 100                 }
 101
 102                 if (isdigit(*event))
 103                         return populate_prog_array(event, fd);
 104
 105                 snprintf(buf, sizeof(buf),
 106                          "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
 107                          is_kprobe ? 'p' : 'r', event, event);
 108                 err = system(buf);
 109                 if (err < 0) {
 110                         printf("failed to create kprobe '%s' error '%s'\n",
 111                                event, strerror(errno));
 112                         return -1;
 113                 }
 114         }
 115
 116         strcpy(buf, DEBUGFS);
 117         strcat(buf, "events/kprobes/");
 118         strcat(buf, event);
 119         strcat(buf, "/id");
 120
 121         efd = open(buf, O_RDONLY, 0);
 122         if (efd < 0) {
 123                 printf("failed to open event %s\n", event);
 124                 return -1;
 125         }
 126
 127         err = read(efd, buf, sizeof(buf));
 128         if (err < 0 || err >= sizeof(buf)) {
 129                 printf("read from '%s' failed '%s'\n", event, strerror(errno));
 130                 return -1;
 131         }
 132
 133         close(efd);
 134
 135         buf[err] = 0;
 136         id = atoi(buf);
 137         attr.config = id;
 138
 139         efd = perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
 140         if (efd < 0) {
 141                 printf("event %d fd %d err %s\n", id, efd, strerror(errno));
 142                 return -1;
 143         }
 144         event_fd[prog_cnt - 1] = efd;
 145         ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
 146         ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
 147
 148         return 0;
 149 }
 150
 151 static int load_maps(struct bpf_map_def *maps, int len)
 152 {
 153         int i;
 154
 155         for (i = 0; i < len / sizeof(struct bpf_map_def); i++) {
 156
 157                 map_fd[i] = bpf_create_map(maps[i].type,
 158                                            maps[i].key_size,
 159                                            maps[i].value_size,
 160                                            maps[i].max_entries);
 161                 if (map_fd[i] < 0)
 162                         return 1;
 163
 164                 if (maps[i].type == BPF_MAP_TYPE_PROG_ARRAY)
 165                         prog_array_fd = map_fd[i];
 166         }
 167         return 0;
 168 }
 169
 170 static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
 171                    GElf_Shdr *shdr, Elf_Data **data)
 172 {
 173         Elf_Scn *scn;
 174
 175         scn = elf_getscn(elf, i);
 176         if (!scn)
 177                 return 1;
 178
 179         if (gelf_getshdr(scn, shdr) != shdr)
 180                 return 2;
 181
 182         *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
 183         if (!*shname || !shdr->sh_size)
 184                 return 3;
 185
 186         *data = elf_getdata(scn, 0);
 187         if (!*data || elf_getdata(scn, *data) != NULL)
 188                 return 4;
 189
 190         return 0;
 191 }
 192
 193 static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
 194                                 GElf_Shdr *shdr, struct bpf_insn *insn)
 195 {
 196         int i, nrels;
 197
 198         nrels = shdr->sh_size / shdr->sh_entsize;
 199
 200         for (i = 0; i < nrels; i++) {
 201                 GElf_Sym sym;
 202                 GElf_Rel rel;
 203                 unsigned int insn_idx;
 204
 205                 gelf_getrel(data, i, &rel);
 206
 207                 insn_idx = rel.r_offset / sizeof(struct bpf_insn);
 208
 209                 gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
 210
 211                 if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
 212                         printf("invalid relo for insn[%d].code 0x%x\n",
 213                                insn_idx, insn[insn_idx].code);
 214                         return 1;
 215                 }
 216                 insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
 217                 insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)];
 218         }
 219
 220         return 0;
 221 }
 222
 223 int load_bpf_file(char *path)
 224 {
 225         int fd, i;
 226         Elf *elf;
 227         GElf_Ehdr ehdr;
 228         GElf_Shdr shdr, shdr_prog;
 229         Elf_Data *data, *data_prog, *symbols = NULL;
 230         char *shname, *shname_prog;
 231
 232         if (elf_version(EV_CURRENT) == EV_NONE)
 233                 return 1;
 234
 235         fd = open(path, O_RDONLY, 0);
 236         if (fd < 0)
 237                 return 1;
 238
 239         elf = elf_begin(fd, ELF_C_READ, NULL);
 240
 241         if (!elf)
 242                 return 1;
 243
 244         if (gelf_getehdr(elf, &ehdr) != &ehdr)
 245                 return 1;
 246
 247         /* clear all kprobes */
 248         i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
 249
 250         /* scan over all elf sections to get license and map info */
 251         for (i = 1; i < ehdr.e_shnum; i++) {
 252
 253                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 254                         continue;
 255
 256                 if (0) /* helpful for llvm debugging */
 257                         printf("section %d:%s data %p size %zd link %d flags %d\n",
 258                                i, shname, data->d_buf, data->d_size,
 259                                shdr.sh_link, (int) shdr.sh_flags);
 260
 261                 if (strcmp(shname, "license") == 0) {
 262                         processed_sec[i] = true;
 263                         memcpy(license, data->d_buf, data->d_size);
 264                 } else if (strcmp(shname, "version") == 0) {
 265                         processed_sec[i] = true;
 266                         if (data->d_size != sizeof(int)) {
 267                                 printf("invalid size of version section %zd\n",
 268                                        data->d_size);
 269                                 return 1;
 270                         }
 271                         memcpy(&kern_version, data->d_buf, sizeof(int));
 272                 } else if (strcmp(shname, "maps") == 0) {
 273                         processed_sec[i] = true;
 274                         if (load_maps(data->d_buf, data->d_size))
 275                                 return 1;
 276                 } else if (shdr.sh_type == SHT_SYMTAB) {
 277                         symbols = data;
 278                 }
 279         }
 280
 281         /* load programs that need map fixup (relocations) */
 282         for (i = 1; i < ehdr.e_shnum; i++) {
 283
 284                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 285                         continue;
 286                 if (shdr.sh_type == SHT_REL) {
 287                         struct bpf_insn *insns;
 288
 289                         if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
 290                                     &shdr_prog, &data_prog))
 291                                 continue;
 292
 293                         insns = (struct bpf_insn *) data_prog->d_buf;
 294
 295                         processed_sec[shdr.sh_info] = true;
 296                         processed_sec[i] = true;
 297
 298                         if (parse_relo_and_apply(data, symbols, &shdr, insns))
 299                                 continue;
 300
 301                         if (memcmp(shname_prog, "kprobe/", 7) == 0 ||
 302                             memcmp(shname_prog, "kretprobe/", 10) == 0 ||
 303                             memcmp(shname_prog, "socket", 6) == 0)
 304                                 load_and_attach(shname_prog, insns, data_prog->d_size);
 305                 }
 306         }
 307
 308         /* load programs that don't use maps */
 309         for (i = 1; i < ehdr.e_shnum; i++) {
 310
 311                 if (processed_sec[i])
 312                         continue;
 313
 314                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 315                         continue;
 316
 317                 if (memcmp(shname, "kprobe/", 7) == 0 ||
 318                     memcmp(shname, "kretprobe/", 10) == 0 ||
 319                     memcmp(shname, "socket", 6) == 0)
 320                         load_and_attach(shname, data->d_buf, data->d_size);
 321         }
 322
 323         close(fd);
 324         return 0;
 325 }
 326
 327 void read_trace_pipe(void)
 328 {
 329         int trace_fd;
 330
 331         trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
 332         if (trace_fd < 0)
 333                 return;
 334
 335         while (1) {
 336                 static char buf[4096];
 337                 ssize_t sz;
 338
 339                 sz = read(trace_fd, buf, sizeof(buf));
 340                 if (sz > 0) {
 341                         buf[sz] = 0;
 342                         puts(buf);
 343                 }
 344         }
 345 }