diff options
Diffstat (limited to 'samples/bpf/bpf_load.c')
| -rw-r--r-- | samples/bpf/bpf_load.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c new file mode 100644 index 0000000..1831d23 --- /dev/null +++ b/samples/bpf/bpf_load.c @@ -0,0 +1,203 @@ +#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 <linux/bpf.h> +#include <linux/filter.h> +#include "libbpf.h" +#include "bpf_helpers.h" +#include "bpf_load.h" + +static char license[128]; +static bool processed_sec[128]; +int map_fd[MAX_MAPS]; +int prog_fd[MAX_PROGS]; +int prog_cnt; + +static int load_and_attach(const char *event, struct bpf_insn *prog, int size) +{ + int fd; + bool is_socket = strncmp(event, "socket", 6) == 0; + + if (!is_socket) + /* tracing events tbd */ + return -1; + + fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, + prog, size, license); + + if (fd < 0) { + printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf); + return -1; + } + + prog_fd[prog_cnt++] = 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; + + /* 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, "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, "events/", 7) == 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, "events/", 7) == 0 || + memcmp(shname, "socket", 6) == 0) + load_and_attach(shname, data->d_buf, data->d_size); + } + + close(fd); + return 0; +} |
