diff options
| -rw-r--r-- | samples/bpf/bpf_load.c | 224 |
1 files changed, 155 insertions, 69 deletions
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c index 4221dc359453..fedec29c7817 100644 --- a/samples/bpf/bpf_load.c +++ b/samples/bpf/bpf_load.c @@ -39,6 +39,16 @@ int event_fd[MAX_PROGS]; int prog_cnt; int prog_array_fd = -1; +/* Keeping relevant info on maps */ +struct bpf_map_data { + int fd; + char *name; + size_t elf_offset; + struct bpf_map_def def; +}; +struct bpf_map_data map_data[MAX_MAPS]; +int map_data_count = 0; + static int populate_prog_array(const char *event, int prog_fd) { int ind = atoi(event), err; @@ -186,42 +196,39 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size) return 0; } -static int load_maps(struct bpf_map_def *maps, int nr_maps, - const char **map_names, fixup_map_cb fixup_map) +static int load_maps(struct bpf_map_data *maps, int nr_maps, + fixup_map_cb fixup_map) { int i; - /* - * Warning: Using "maps" pointing to ELF data_maps->d_buf as - * an array of struct bpf_map_def is a wrong assumption about - * the ELF maps section format. - */ + for (i = 0; i < nr_maps; i++) { if (fixup_map) - fixup_map(&maps[i], map_names[i], i); + fixup_map(&maps[i].def, maps[i].name, i); - if (maps[i].type == BPF_MAP_TYPE_ARRAY_OF_MAPS || - maps[i].type == BPF_MAP_TYPE_HASH_OF_MAPS) { - int inner_map_fd = map_fd[maps[i].inner_map_idx]; + if (maps[i].def.type == BPF_MAP_TYPE_ARRAY_OF_MAPS || + maps[i].def.type == BPF_MAP_TYPE_HASH_OF_MAPS) { + int inner_map_fd = map_fd[maps[i].def.inner_map_idx]; - map_fd[i] = bpf_create_map_in_map(maps[i].type, - maps[i].key_size, - inner_map_fd, - maps[i].max_entries, - maps[i].map_flags); + map_fd[i] = bpf_create_map_in_map(maps[i].def.type, + maps[i].def.key_size, + inner_map_fd, + maps[i].def.max_entries, + maps[i].def.map_flags); } else { - map_fd[i] = bpf_create_map(maps[i].type, - maps[i].key_size, - maps[i].value_size, - maps[i].max_entries, - maps[i].map_flags); + map_fd[i] = bpf_create_map(maps[i].def.type, + maps[i].def.key_size, + maps[i].def.value_size, + maps[i].def.max_entries, + maps[i].def.map_flags); } if (map_fd[i] < 0) { printf("failed to create a map: %d %s\n", errno, strerror(errno)); return 1; } + maps[i].fd = map_fd[i]; - if (maps[i].type == BPF_MAP_TYPE_PROG_ARRAY) + if (maps[i].def.type == BPF_MAP_TYPE_PROG_ARRAY) prog_array_fd = map_fd[i]; } return 0; @@ -251,7 +258,8 @@ static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname, } static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols, - GElf_Shdr *shdr, struct bpf_insn *insn) + GElf_Shdr *shdr, struct bpf_insn *insn, + struct bpf_map_data *maps, int nr_maps) { int i, nrels; @@ -261,6 +269,8 @@ static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols, GElf_Sym sym; GElf_Rel rel; unsigned int insn_idx; + bool match = false; + int j, map_idx; gelf_getrel(data, i, &rel); @@ -274,11 +284,21 @@ static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols, return 1; } insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD; - /* - * Warning: Using sizeof(struct bpf_map_def) here is a - * wrong assumption about ELF maps section format - */ - insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)]; + + /* Match FD relocation against recorded map_data[] offset */ + for (map_idx = 0; map_idx < nr_maps; map_idx++) { + if (maps[map_idx].elf_offset == sym.st_value) { + match = true; + break; + } + } + if (match) { + insn[insn_idx].imm = maps[map_idx].fd; + } else { + printf("invalid relo for insn[%d] no map_data match\n", + insn_idx); + return 1; + } } return 0; @@ -297,40 +317,112 @@ static int cmp_symbols(const void *l, const void *r) return 0; } -static int get_sorted_map_names(Elf *elf, Elf_Data *symbols, int maps_shndx, - int strtabidx, char **map_names) +static int load_elf_maps_section(struct bpf_map_data *maps, int maps_shndx, + Elf *elf, Elf_Data *symbols, int strtabidx) { - GElf_Sym map_symbols[MAX_MAPS]; - int i, nr_maps = 0; + int map_sz_elf, map_sz_copy; + bool validate_zero = false; + Elf_Data *data_maps; + int i, nr_maps; + GElf_Sym *sym; + Elf_Scn *scn; + int copy_sz; + + if (maps_shndx < 0) + return -EINVAL; + if (!symbols) + return -EINVAL; + + /* Get data for maps section via elf index */ + scn = elf_getscn(elf, maps_shndx); + if (scn) + data_maps = elf_getdata(scn, NULL); + if (!scn || !data_maps) { + printf("Failed to get Elf_Data from maps section %d\n", + maps_shndx); + return -EINVAL; + } - for (i = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) { - assert(nr_maps < MAX_MAPS); - if (!gelf_getsym(symbols, i, &map_symbols[nr_maps])) + /* For each map get corrosponding symbol table entry */ + sym = calloc(MAX_MAPS+1, sizeof(GElf_Sym)); + for (i = 0, nr_maps = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) { + assert(nr_maps < MAX_MAPS+1); + if (!gelf_getsym(symbols, i, &sym[nr_maps])) continue; - if (map_symbols[nr_maps].st_shndx != maps_shndx) + if (sym[nr_maps].st_shndx != maps_shndx) continue; + /* Only increment iif maps section */ nr_maps++; } - qsort(map_symbols, nr_maps, sizeof(GElf_Sym), cmp_symbols); + /* Align to map_fd[] order, via sort on offset in sym.st_value */ + qsort(sym, nr_maps, sizeof(GElf_Sym), cmp_symbols); + + /* Keeping compatible with ELF maps section changes + * ------------------------------------------------ + * The program size of struct bpf_map_def is known by loader + * code, but struct stored in ELF file can be different. + * + * Unfortunately sym[i].st_size is zero. To calculate the + * struct size stored in the ELF file, assume all struct have + * the same size, and simply divide with number of map + * symbols. + */ + map_sz_elf = data_maps->d_size / nr_maps; + map_sz_copy = sizeof(struct bpf_map_def); + if (map_sz_elf < map_sz_copy) { + /* + * Backward compat, loading older ELF file with + * smaller struct, keeping remaining bytes zero. + */ + map_sz_copy = map_sz_elf; + } else if (map_sz_elf > map_sz_copy) { + /* + * Forward compat, loading newer ELF file with larger + * struct with unknown features. Assume zero means + * feature not used. Thus, validate rest of struct + * data is zero. + */ + validate_zero = true; + } + /* Memcpy relevant part of ELF maps data to loader maps */ for (i = 0; i < nr_maps; i++) { - char *map_name; - - map_name = elf_strptr(elf, strtabidx, map_symbols[i].st_name); - if (!map_name) { - printf("cannot get map symbol\n"); - return -1; - } - - map_names[i] = strdup(map_name); - if (!map_names[i]) { + unsigned char *addr, *end; + struct bpf_map_def *def; + const char *map_name; + size_t offset; + + map_name = elf_strptr(elf, strtabidx, sym[i].st_name); + maps[i].name = strdup(map_name); + if (!maps[i].name) { printf("strdup(%s): %s(%d)\n", map_name, strerror(errno), errno); - return -1; + free(sym); + return -errno; + } + + /* Symbol value is offset into ELF maps section data area */ + offset = sym[i].st_value; + def = (struct bpf_map_def *)(data_maps->d_buf + offset); + maps[i].elf_offset = offset; + memset(&maps[i].def, 0, sizeof(struct bpf_map_def)); + memcpy(&maps[i].def, def, map_sz_copy); + + /* Verify no newer features were requested */ + if (validate_zero) { + addr = (unsigned char*) def + map_sz_copy; + end = (unsigned char*) def + map_sz_elf; + for (; addr < end; addr++) { + if (*addr != 0) { + free(sym); + return -EFBIG; + } + } } } + free(sym); return nr_maps; } @@ -341,7 +433,8 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map) GElf_Ehdr ehdr; GElf_Shdr shdr, shdr_prog; Elf_Data *data, *data_prog, *data_maps = NULL, *symbols = NULL; - char *shname, *shname_prog, *map_names[MAX_MAPS] = { NULL }; + char *shname, *shname_prog; + int nr_maps = 0; /* reset global variables */ kern_version = 0; @@ -389,8 +482,12 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map) } memcpy(&kern_version, data->d_buf, sizeof(int)); } else if (strcmp(shname, "maps") == 0) { + int j; + maps_shndx = i; data_maps = data; + for (j = 0; j < MAX_MAPS; j++) + map_data[j].fd = -1; } else if (shdr.sh_type == SHT_SYMTAB) { strtabidx = shdr.sh_link; symbols = data; @@ -405,27 +502,17 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map) } if (data_maps) { - int nr_maps; - int prog_elf_map_sz; - - nr_maps = get_sorted_map_names(elf, symbols, maps_shndx, - strtabidx, map_names); - if (nr_maps < 0) - goto done; - - /* Deduce map struct size stored in ELF maps section */ - prog_elf_map_sz = data_maps->d_size / nr_maps; - if (prog_elf_map_sz != sizeof(struct bpf_map_def)) { - printf("Error: ELF maps sec wrong size (%d/%lu)," - " old kern.o file?\n", - prog_elf_map_sz, sizeof(struct bpf_map_def)); + nr_maps = load_elf_maps_section(map_data, maps_shndx, + elf, symbols, strtabidx); + if (nr_maps < 0) { + printf("Error: Failed loading ELF maps (errno:%d):%s\n", + nr_maps, strerror(-nr_maps)); ret = 1; goto done; } - - if (load_maps(data_maps->d_buf, nr_maps, - (const char **)map_names, fixup_map)) + if (load_maps(map_data, nr_maps, fixup_map)) goto done; + map_data_count = nr_maps; processed_sec[maps_shndx] = true; } @@ -453,7 +540,8 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map) processed_sec[shdr.sh_info] = true; processed_sec[i] = true; - if (parse_relo_and_apply(data, symbols, &shdr, insns)) + if (parse_relo_and_apply(data, symbols, &shdr, insns, + map_data, nr_maps)) continue; if (memcmp(shname_prog, "kprobe/", 7) == 0 || @@ -488,8 +576,6 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map) ret = 0; done: - for (i = 0; i < MAX_MAPS; i++) - free(map_names[i]); close(fd); return ret; } |