From 48cca7e44f9f8268fdcd4351e2f19ff2275119d1 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 14 Dec 2017 17:55:10 -0800 Subject: [PATCH] libbpf: add support for bpf_call - recognize relocation emitted by llvm - since all regular function will be kept in .text section and llvm takes care of pc-relative offsets in bpf_call instruction simply copy all of .text to relevant program section while adjusting bpf_call instructions in program section to point to newly copied body of instructions from .text - do so for all programs in the elf file - set all programs types to the one passed to bpf_prog_load() Note for elf files with multiple programs that use different functions in .text section we need to do 'linker' style logic. This work is still TBD Signed-off-by: Alexei Starovoitov Acked-by: Daniel Borkmann Signed-off-by: Daniel Borkmann --- tools/include/uapi/linux/bpf.h | 6 ++ tools/lib/bpf/bpf.h | 2 +- tools/lib/bpf/libbpf.c | 170 ++++++++++++++++++++++++--------- 3 files changed, 134 insertions(+), 44 deletions(-) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index cf446c25c0ec..db1b0923a308 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -197,8 +197,14 @@ enum bpf_attach_type { */ #define BPF_F_STRICT_ALIGNMENT (1U << 0) +/* when bpf_ldimm64->src_reg == BPF_PSEUDO_MAP_FD, bpf_ldimm64->imm == fd */ #define BPF_PSEUDO_MAP_FD 1 +/* when bpf_call->src_reg == BPF_PSEUDO_CALL, bpf_call->imm == pc-relative + * offset to another bpf function + */ +#define BPF_PSEUDO_CALL 1 + /* flags for BPF_MAP_UPDATE_ELEM command */ #define BPF_ANY 0 /* create new element or update existing */ #define BPF_NOEXIST 1 /* create new element if it didn't exist */ diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 6534889e2b2f..9f44c196931e 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -40,7 +40,7 @@ int bpf_create_map_in_map(enum bpf_map_type map_type, const char *name, __u32 map_flags); /* Recommend log buffer size */ -#define BPF_LOG_BUF_SIZE 65536 +#define BPF_LOG_BUF_SIZE (256 * 1024) int bpf_load_program_name(enum bpf_prog_type type, const char *name, const struct bpf_insn *insns, size_t insns_cnt, const char *license, diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 65d0d0aff4fa..5b83875b3594 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -174,12 +174,19 @@ struct bpf_program { char *name; char *section_name; struct bpf_insn *insns; - size_t insns_cnt; + size_t insns_cnt, main_prog_cnt; enum bpf_prog_type type; - struct { + struct reloc_desc { + enum { + RELO_LD64, + RELO_CALL, + } type; int insn_idx; - int map_idx; + union { + int map_idx; + int text_off; + }; } *reloc_desc; int nr_reloc; @@ -234,6 +241,7 @@ struct bpf_object { } *reloc; int nr_reloc; int maps_shndx; + int text_shndx; } efile; /* * All loaded bpf_object is linked in a list, which is @@ -375,9 +383,13 @@ bpf_object__init_prog_names(struct bpf_object *obj) size_t pi, si; for (pi = 0; pi < obj->nr_programs; pi++) { - char *name = NULL; + const char *name = NULL; prog = &obj->programs[pi]; + if (prog->idx == obj->efile.text_shndx) { + name = ".text"; + goto skip_search; + } for (si = 0; si < symbols->d_size / sizeof(GElf_Sym) && !name; si++) { @@ -405,7 +417,7 @@ bpf_object__init_prog_names(struct bpf_object *obj) prog->section_name); return -EINVAL; } - +skip_search: prog->name = strdup(name); if (!prog->name) { pr_warning("failed to allocate memory for prog sym %s\n", @@ -795,6 +807,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj) } else if ((sh.sh_type == SHT_PROGBITS) && (sh.sh_flags & SHF_EXECINSTR) && (data->d_size > 0)) { + if (strcmp(name, ".text") == 0) + obj->efile.text_shndx = idx; err = bpf_object__add_program(obj, data->d_buf, data->d_size, name, idx); if (err) { @@ -856,11 +870,14 @@ bpf_object__find_prog_by_idx(struct bpf_object *obj, int idx) } static int -bpf_program__collect_reloc(struct bpf_program *prog, - size_t nr_maps, GElf_Shdr *shdr, - Elf_Data *data, Elf_Data *symbols, - int maps_shndx, struct bpf_map *maps) +bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr, + Elf_Data *data, struct bpf_object *obj) { + Elf_Data *symbols = obj->efile.symbols; + int text_shndx = obj->efile.text_shndx; + int maps_shndx = obj->efile.maps_shndx; + struct bpf_map *maps = obj->maps; + size_t nr_maps = obj->nr_maps; int i, nrels; pr_debug("collecting relocating info for: '%s'\n", @@ -893,8 +910,10 @@ bpf_program__collect_reloc(struct bpf_program *prog, GELF_R_SYM(rel.r_info)); return -LIBBPF_ERRNO__FORMAT; } + pr_debug("relo for %ld value %ld name %d\n", + rel.r_info >> 32, sym.st_value, sym.st_name); - if (sym.st_shndx != maps_shndx) { + if (sym.st_shndx != maps_shndx && sym.st_shndx != text_shndx) { pr_warning("Program '%s' contains non-map related relo data pointing to section %u\n", prog->section_name, sym.st_shndx); return -LIBBPF_ERRNO__RELOC; @@ -903,6 +922,17 @@ bpf_program__collect_reloc(struct bpf_program *prog, insn_idx = rel.r_offset / sizeof(struct bpf_insn); pr_debug("relocation: insn_idx=%u\n", insn_idx); + if (insns[insn_idx].code == (BPF_JMP | BPF_CALL)) { + if (insns[insn_idx].src_reg != BPF_PSEUDO_CALL) { + pr_warning("incorrect bpf_call opcode\n"); + return -LIBBPF_ERRNO__RELOC; + } + prog->reloc_desc[i].type = RELO_CALL; + prog->reloc_desc[i].insn_idx = insn_idx; + prog->reloc_desc[i].text_off = sym.st_value; + continue; + } + if (insns[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) { pr_warning("bpf: relocation: invalid relo for insns[%d].code 0x%x\n", insn_idx, insns[insn_idx].code); @@ -924,6 +954,7 @@ bpf_program__collect_reloc(struct bpf_program *prog, return -LIBBPF_ERRNO__RELOC; } + prog->reloc_desc[i].type = RELO_LD64; prog->reloc_desc[i].insn_idx = insn_idx; prog->reloc_desc[i].map_idx = map_idx; } @@ -962,28 +993,77 @@ bpf_object__create_maps(struct bpf_object *obj) return 0; } +static int +bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj, + struct reloc_desc *relo) +{ + struct bpf_insn *insn, *new_insn; + struct bpf_program *text; + size_t new_cnt; + + if (relo->type != RELO_CALL) + return -LIBBPF_ERRNO__RELOC; + + if (prog->idx == obj->efile.text_shndx) { + pr_warning("relo in .text insn %d into off %d\n", + relo->insn_idx, relo->text_off); + return -LIBBPF_ERRNO__RELOC; + } + + if (prog->main_prog_cnt == 0) { + text = bpf_object__find_prog_by_idx(obj, obj->efile.text_shndx); + if (!text) { + pr_warning("no .text section found yet relo into text exist\n"); + return -LIBBPF_ERRNO__RELOC; + } + new_cnt = prog->insns_cnt + text->insns_cnt; + new_insn = realloc(prog->insns, new_cnt * sizeof(*insn)); + if (!new_insn) { + pr_warning("oom in prog realloc\n"); + return -ENOMEM; + } + memcpy(new_insn + prog->insns_cnt, text->insns, + text->insns_cnt * sizeof(*insn)); + prog->insns = new_insn; + prog->main_prog_cnt = prog->insns_cnt; + prog->insns_cnt = new_cnt; + } + insn = &prog->insns[relo->insn_idx]; + insn->imm += prog->main_prog_cnt - relo->insn_idx; + pr_debug("added %zd insn from %s to prog %s\n", + text->insns_cnt, text->section_name, prog->section_name); + return 0; +} + static int bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj) { - int i; + int i, err; if (!prog || !prog->reloc_desc) return 0; for (i = 0; i < prog->nr_reloc; i++) { - int insn_idx, map_idx; - struct bpf_insn *insns = prog->insns; + if (prog->reloc_desc[i].type == RELO_LD64) { + struct bpf_insn *insns = prog->insns; + int insn_idx, map_idx; - insn_idx = prog->reloc_desc[i].insn_idx; - map_idx = prog->reloc_desc[i].map_idx; + insn_idx = prog->reloc_desc[i].insn_idx; + map_idx = prog->reloc_desc[i].map_idx; - if (insn_idx >= (int)prog->insns_cnt) { - pr_warning("relocation out of range: '%s'\n", - prog->section_name); - return -LIBBPF_ERRNO__RELOC; + if (insn_idx >= (int)prog->insns_cnt) { + pr_warning("relocation out of range: '%s'\n", + prog->section_name); + return -LIBBPF_ERRNO__RELOC; + } + insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD; + insns[insn_idx].imm = obj->maps[map_idx].fd; + } else { + err = bpf_program__reloc_text(prog, obj, + &prog->reloc_desc[i]); + if (err) + return err; } - insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD; - insns[insn_idx].imm = obj->maps[map_idx].fd; } zfree(&prog->reloc_desc); @@ -1026,7 +1106,6 @@ static int bpf_object__collect_reloc(struct bpf_object *obj) Elf_Data *data = obj->efile.reloc[i].data; int idx = shdr->sh_info; struct bpf_program *prog; - size_t nr_maps = obj->nr_maps; if (shdr->sh_type != SHT_REL) { pr_warning("internal error at %d\n", __LINE__); @@ -1040,11 +1119,9 @@ static int bpf_object__collect_reloc(struct bpf_object *obj) return -LIBBPF_ERRNO__RELOC; } - err = bpf_program__collect_reloc(prog, nr_maps, + err = bpf_program__collect_reloc(prog, shdr, data, - obj->efile.symbols, - obj->efile.maps_shndx, - obj->maps); + obj); if (err) return err; } @@ -1197,6 +1274,8 @@ bpf_object__load_progs(struct bpf_object *obj) int err; for (i = 0; i < obj->nr_programs; i++) { + if (obj->programs[i].idx == obj->efile.text_shndx) + continue; err = bpf_program__load(&obj->programs[i], obj->license, obj->kern_version); @@ -1859,7 +1938,7 @@ long libbpf_get_error(const void *ptr) int bpf_prog_load(const char *file, enum bpf_prog_type type, struct bpf_object **pobj, int *prog_fd) { - struct bpf_program *prog; + struct bpf_program *prog, *first_prog = NULL; struct bpf_object *obj; int err; @@ -1867,25 +1946,30 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type, if (IS_ERR(obj)) return -ENOENT; - prog = bpf_program__next(NULL, obj); - if (!prog) { - bpf_object__close(obj); - return -ENOENT; - } - - /* - * If type is not specified, try to guess it based on - * section name. - */ - if (type == BPF_PROG_TYPE_UNSPEC) { - type = bpf_program__guess_type(prog); + bpf_object__for_each_program(prog, obj) { + /* + * If type is not specified, try to guess it based on + * section name. + */ if (type == BPF_PROG_TYPE_UNSPEC) { - bpf_object__close(obj); - return -EINVAL; + type = bpf_program__guess_type(prog); + if (type == BPF_PROG_TYPE_UNSPEC) { + bpf_object__close(obj); + return -EINVAL; + } } + + bpf_program__set_type(prog, type); + if (prog->idx != obj->efile.text_shndx && !first_prog) + first_prog = prog; + } + + if (!first_prog) { + pr_warning("object file doesn't contain bpf program\n"); + bpf_object__close(obj); + return -ENOENT; } - bpf_program__set_type(prog, type); err = bpf_object__load(obj); if (err) { bpf_object__close(obj); @@ -1893,6 +1977,6 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type, } *pobj = obj; - *prog_fd = bpf_program__fd(prog); + *prog_fd = bpf_program__fd(first_prog); return 0; } -- 2.30.2