diff options
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/lib/bpf/Build | 2 | ||||
| -rw-r--r-- | tools/lib/bpf/libbpf.c | 11 | ||||
| -rw-r--r-- | tools/lib/bpf/libbpf.h | 13 | ||||
| -rw-r--r-- | tools/lib/bpf/libbpf.map | 4 | ||||
| -rw-r--r-- | tools/lib/bpf/libbpf_internal.h | 20 | ||||
| -rw-r--r-- | tools/lib/bpf/linker.c | 1176 |
6 files changed, 1215 insertions, 11 deletions
diff --git a/tools/lib/bpf/Build b/tools/lib/bpf/Build index 8136186a453f..9b057cc7650a 100644 --- a/tools/lib/bpf/Build +++ b/tools/lib/bpf/Build @@ -1,3 +1,3 @@ libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o \ netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o hashmap.o \ - btf_dump.o ringbuf.o strset.o + btf_dump.o ringbuf.o strset.o linker.o diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 18ba37164e17..058b643cbcb1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -55,10 +55,6 @@ #include "libbpf_internal.h" #include "hashmap.h" -#ifndef EM_BPF -#define EM_BPF 247 -#endif - #ifndef BPF_FS_MAGIC #define BPF_FS_MAGIC 0xcafe4a11 #endif @@ -1134,11 +1130,6 @@ static void bpf_object__elf_finish(struct bpf_object *obj) obj->efile.obj_buf_sz = 0; } -/* if libelf is old and doesn't support mmap(), fall back to read() */ -#ifndef ELF_C_READ_MMAP -#define ELF_C_READ_MMAP ELF_C_READ -#endif - static int bpf_object__elf_init(struct bpf_object *obj) { int err = 0; @@ -2807,7 +2798,7 @@ static bool ignore_elf_section(GElf_Shdr *hdr, const char *name) return true; /* ignore .llvm_addrsig section as well */ - if (hdr->sh_type == 0x6FFF4C03 /* SHT_LLVM_ADDRSIG */) + if (hdr->sh_type == SHT_LLVM_ADDRSIG) return true; /* no subprograms will lead to an empty .text section, ignore it */ diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 3d690d4e785c..a1a424b9b8ff 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -760,6 +760,19 @@ enum libbpf_tristate { TRI_MODULE = 2, }; +struct bpf_linker_opts { + /* size of this struct, for forward/backward compatiblity */ + size_t sz; +}; +#define bpf_linker_opts__last_field sz + +struct bpf_linker; + +LIBBPF_API struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts *opts); +LIBBPF_API int bpf_linker__add_file(struct bpf_linker *linker, const char *filename); +LIBBPF_API int bpf_linker__finalize(struct bpf_linker *linker); +LIBBPF_API void bpf_linker__free(struct bpf_linker *linker); + #ifdef __cplusplus } /* extern "C" */ #endif diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index d31d8c968097..279ae861f568 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -355,4 +355,8 @@ LIBBPF_0.4.0 { global: btf__add_float; btf__add_type; + bpf_linker__add_file; + bpf_linker__finalize; + bpf_linker__free; + bpf_linker__new; } LIBBPF_0.3.0; diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index e0787900eeca..6017902c687e 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -20,6 +20,26 @@ #include "libbpf.h" +#ifndef EM_BPF +#define EM_BPF 247 +#endif + +#ifndef R_BPF_64_64 +#define R_BPF_64_64 1 +#endif +#ifndef R_BPF_64_32 +#define R_BPF_64_32 10 +#endif + +#ifndef SHT_LLVM_ADDRSIG +#define SHT_LLVM_ADDRSIG 0x6FFF4C03 +#endif + +/* if libelf is old and doesn't support mmap(), fall back to read() */ +#ifndef ELF_C_READ_MMAP +#define ELF_C_READ_MMAP ELF_C_READ +#endif + #define BTF_INFO_ENC(kind, kind_flag, vlen) \ ((!!(kind_flag) << 31) | ((kind) << 24) | ((vlen) & BTF_MAX_VLEN)) #define BTF_TYPE_ENC(name, info, size_or_type) (name), (info), (size_or_type) diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c new file mode 100644 index 000000000000..01b56939a835 --- /dev/null +++ b/tools/lib/bpf/linker.c @@ -0,0 +1,1176 @@ +// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) +/* + * BPF static linker + * + * Copyright (c) 2021 Facebook + */ +#include <stdbool.h> +#include <stddef.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <errno.h> +#include <linux/err.h> +#include <linux/btf.h> +#include <elf.h> +#include <libelf.h> +#include <gelf.h> +#include <fcntl.h> +#include "libbpf.h" +#include "btf.h" +#include "libbpf_internal.h" +#include "strset.h" + +struct src_sec { + const char *sec_name; + /* positional (not necessarily ELF) index in an array of sections */ + int id; + /* positional (not necessarily ELF) index of a matching section in a final object file */ + int dst_id; + /* section data offset in a matching output section */ + int dst_off; + /* whether section is omitted from the final ELF file */ + bool skipped; + + /* ELF info */ + size_t sec_idx; + Elf_Scn *scn; + Elf64_Shdr *shdr; + Elf_Data *data; +}; + +struct src_obj { + const char *filename; + int fd; + Elf *elf; + /* Section header strings section index */ + size_t shstrs_sec_idx; + /* SYMTAB section index */ + size_t symtab_sec_idx; + + /* List of sections. Slot zero is unused. */ + struct src_sec *secs; + int sec_cnt; + + /* mapping of symbol indices from src to dst ELF */ + int *sym_map; +}; + +struct dst_sec { + char *sec_name; + /* positional (not necessarily ELF) index in an array of sections */ + int id; + + /* ELF info */ + size_t sec_idx; + Elf_Scn *scn; + Elf64_Shdr *shdr; + Elf_Data *data; + + /* final output section size */ + int sec_sz; + /* final output contents of the section */ + void *raw_data; + + /* corresponding STT_SECTION symbol index in SYMTAB */ + int sec_sym_idx; +}; + +struct bpf_linker { + char *filename; + int fd; + Elf *elf; + Elf64_Ehdr *elf_hdr; + + /* Output sections metadata */ + struct dst_sec *secs; + int sec_cnt; + + struct strset *strtab_strs; /* STRTAB unique strings */ + size_t strtab_sec_idx; /* STRTAB section index */ + size_t symtab_sec_idx; /* SYMTAB section index */ +}; + +#define pr_warn_elf(fmt, ...) \ +do { \ + libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1)); \ +} while (0) + +static int init_output_elf(struct bpf_linker *linker, const char *file); + +static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, struct src_obj *obj); +static int linker_sanity_check_elf(struct src_obj *obj); +static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj); +static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj); +static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj); + +void bpf_linker__free(struct bpf_linker *linker) +{ + int i; + + if (!linker) + return; + + free(linker->filename); + + if (linker->elf) + elf_end(linker->elf); + + if (linker->fd >= 0) + close(linker->fd); + + strset__free(linker->strtab_strs); + + for (i = 1; i < linker->sec_cnt; i++) { + struct dst_sec *sec = &linker->secs[i]; + + free(sec->sec_name); + free(sec->raw_data); + } + free(linker->secs); + + free(linker); +} + +struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts *opts) +{ + struct bpf_linker *linker; + int err; + + if (!OPTS_VALID(opts, bpf_linker_opts)) + return NULL; + + if (elf_version(EV_CURRENT) == EV_NONE) { + pr_warn_elf("libelf initialization failed"); + return NULL; + } + + linker = calloc(1, sizeof(*linker)); + if (!linker) + return NULL; + + linker->fd = -1; + + err = init_output_elf(linker, filename); + if (err) + goto err_out; + + return linker; + +err_out: + bpf_linker__free(linker); + return NULL; +} + +static struct dst_sec *add_dst_sec(struct bpf_linker *linker, const char *sec_name) +{ + struct dst_sec *secs = linker->secs, *sec; + size_t new_cnt = linker->sec_cnt ? linker->sec_cnt + 1 : 2; + + secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs)); + if (!secs) + return NULL; + + /* zero out newly allocated memory */ + memset(secs + linker->sec_cnt, 0, (new_cnt - linker->sec_cnt) * sizeof(*secs)); + + linker->secs = secs; + linker->sec_cnt = new_cnt; + + sec = &linker->secs[new_cnt - 1]; + sec->id = new_cnt - 1; + sec->sec_name = strdup(sec_name); + if (!sec->sec_name) + return NULL; + + return sec; +} + +static Elf64_Sym *add_new_sym(struct bpf_linker *linker, size_t *sym_idx) +{ + struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx]; + Elf64_Sym *syms, *sym; + size_t sym_cnt = symtab->sec_sz / sizeof(*sym); + + syms = libbpf_reallocarray(symtab->raw_data, sym_cnt + 1, sizeof(*sym)); + if (!syms) + return NULL; + + sym = &syms[sym_cnt]; + memset(sym, 0, sizeof(*sym)); + + symtab->raw_data = syms; + symtab->sec_sz += sizeof(*sym); + symtab->shdr->sh_size += sizeof(*sym); + symtab->data->d_size += sizeof(*sym); + + if (sym_idx) + *sym_idx = sym_cnt; + + return sym; +} + +static int init_output_elf(struct bpf_linker *linker, const char *file) +{ + int err, str_off; + Elf64_Sym *init_sym; + struct dst_sec *sec; + + linker->filename = strdup(file); + if (!linker->filename) + return -ENOMEM; + + linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC, 0644); + if (linker->fd < 0) { + err = -errno; + pr_warn("failed to create '%s': %d\n", file, err); + return err; + } + + linker->elf = elf_begin(linker->fd, ELF_C_WRITE, NULL); + if (!linker->elf) { + pr_warn_elf("failed to create ELF object"); + return -EINVAL; + } + + /* ELF header */ + linker->elf_hdr = elf64_newehdr(linker->elf); + if (!linker->elf_hdr){ + pr_warn_elf("failed to create ELF header"); + return -EINVAL; + } + + linker->elf_hdr->e_machine = EM_BPF; + linker->elf_hdr->e_type = ET_REL; +#if __BYTE_ORDER == __LITTLE_ENDIAN + linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB; +#elif __BYTE_ORDER == __BIG_ENDIAN + linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB; +#else +#error "Unknown __BYTE_ORDER" +#endif + + /* STRTAB */ + /* initialize strset with an empty string to conform to ELF */ + linker->strtab_strs = strset__new(INT_MAX, "", sizeof("")); + if (libbpf_get_error(linker->strtab_strs)) + return libbpf_get_error(linker->strtab_strs); + + sec = add_dst_sec(linker, ".strtab"); + if (!sec) + return -ENOMEM; + + sec->scn = elf_newscn(linker->elf); + if (!sec->scn) { + pr_warn_elf("failed to create STRTAB section"); + return -EINVAL; + } + + sec->shdr = elf64_getshdr(sec->scn); + if (!sec->shdr) + return -EINVAL; + + sec->data = elf_newdata(sec->scn); + if (!sec->data) { + pr_warn_elf("failed to create STRTAB data"); + return -EINVAL; + } + + str_off = strset__add_str(linker->strtab_strs, sec->sec_name); + if (str_off < 0) + return str_off; + + sec->sec_idx = elf_ndxscn(sec->scn); + linker->elf_hdr->e_shstrndx = sec->sec_idx; + linker->strtab_sec_idx = sec->sec_idx; + + sec->shdr->sh_name = str_off; + sec->shdr->sh_type = SHT_STRTAB; + sec->shdr->sh_flags = SHF_STRINGS; + sec->shdr->sh_offset = 0; + sec->shdr->sh_link = 0; + sec->shdr->sh_info = 0; + sec->shdr->sh_addralign = 1; + sec->shdr->sh_size = sec->sec_sz = 0; + sec->shdr->sh_entsize = 0; + + /* SYMTAB */ + sec = add_dst_sec(linker, ".symtab"); + if (!sec) + return -ENOMEM; + + sec->scn = elf_newscn(linker->elf); + if (!sec->scn) { + pr_warn_elf("failed to create SYMTAB section"); + return -EINVAL; + } + + sec->shdr = elf64_getshdr(sec->scn); + if (!sec->shdr) + return -EINVAL; + + sec->data = elf_newdata(sec->scn); + if (!sec->data) { + pr_warn_elf("failed to create SYMTAB data"); + return -EINVAL; + } + + str_off = strset__add_str(linker->strtab_strs, sec->sec_name); + if (str_off < 0) + return str_off; + + sec->sec_idx = elf_ndxscn(sec->scn); + linker->symtab_sec_idx = sec->sec_idx; + + sec->shdr->sh_name = str_off; + sec->shdr->sh_type = SHT_SYMTAB; + sec->shdr->sh_flags = 0; + sec->shdr->sh_offset = 0; + sec->shdr->sh_link = linker->strtab_sec_idx; + /* sh_info should be one greater than the index of the last local + * symbol (i.e., binding is STB_LOCAL). But why and who cares? + */ + sec->shdr->sh_info = 0; + sec->shdr->sh_addralign = 8; + sec->shdr->sh_entsize = sizeof(Elf64_Sym); + + /* add the special all-zero symbol */ + init_sym = add_new_sym(linker, NULL); + if (!init_sym) + return -EINVAL; + + init_sym->st_name = 0; + init_sym->st_info = 0; + init_sym->st_other = 0; + init_sym->st_shndx = SHN_UNDEF; + init_sym->st_value = 0; + init_sym->st_size = 0; + + return 0; +} + +int bpf_linker__add_file(struct bpf_linker *linker, const char *filename) +{ + struct src_obj obj = {}; + int err = 0; + + if (!linker->elf) + return -EINVAL; + + err = err ?: linker_load_obj_file(linker, filename, &obj); + err = err ?: linker_append_sec_data(linker, &obj); + err = err ?: linker_append_elf_syms(linker, &obj); + err = err ?: linker_append_elf_relos(linker, &obj); + + /* free up src_obj resources */ + free(obj.secs); + free(obj.sym_map); + if (obj.elf) + elf_end(obj.elf); + if (obj.fd >= 0) + close(obj.fd); + + return err; +} + +static bool is_dwarf_sec_name(const char *name) +{ + /* approximation, but the actual list is too long */ + return strncmp(name, ".debug_", sizeof(".debug_") - 1) == 0; +} + +static bool is_ignored_sec(struct src_sec *sec) +{ + Elf64_Shdr *shdr = sec->shdr; + const char *name = sec->sec_name; + + /* no special handling of .strtab */ + if (shdr->sh_type == SHT_STRTAB) + return true; + + /* ignore .llvm_addrsig section as well */ + if (shdr->sh_type == SHT_LLVM_ADDRSIG) + return true; + + /* no subprograms will lead to an empty .text section, ignore it */ + if (shdr->sh_type == SHT_PROGBITS && shdr->sh_size == 0 && + strcmp(sec->sec_name, ".text") == 0) + return true; + + /* DWARF sections */ + if (is_dwarf_sec_name(sec->sec_name)) + return true; + + if (strncmp(name, ".rel", sizeof(".rel") - 1) == 0) { + name += sizeof(".rel") - 1; + /* DWARF section relocations */ + if (is_dwarf_sec_name(name)) + return true; + + /* .BTF and .BTF.ext don't need relocations */ + if (strcmp(name, BTF_ELF_SEC) == 0 || + strcmp(name, BTF_EXT_ELF_SEC) == 0) + return true; + } + + return false; +} + +static struct src_sec *add_src_sec(struct src_obj *obj, const char *sec_name) +{ + struct src_sec *secs = obj->secs, *sec; + size_t new_cnt = obj->sec_cnt ? obj->sec_cnt + 1 : 2; + + secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs)); + if (!secs) + return NULL; + + /* zero out newly allocated memory */ + memset(secs + obj->sec_cnt, 0, (new_cnt - obj->sec_cnt) * sizeof(*secs)); + + obj->secs = secs; + obj->sec_cnt = new_cnt; + + sec = &obj->secs[new_cnt - 1]; + sec->id = new_cnt - 1; + sec->sec_name = sec_name; + + return sec; +} + +static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, struct src_obj *obj) +{ +#if __BYTE_ORDER == __LITTLE_ENDIAN + const int host_endianness = ELFDATA2LSB; +#elif __BYTE_ORDER == __BIG_ENDIAN + const int host_endianness = ELFDATA2MSB; +#else +#error "Unknown __BYTE_ORDER" +#endif + int err = 0; + Elf_Scn *scn; + Elf_Data *data; + Elf64_Ehdr *ehdr; + Elf64_Shdr *shdr; + struct src_sec *sec; + + pr_debug("linker: adding object file '%s'...\n", filename); + + obj->filename = filename; + + obj->fd = open(filename, O_RDONLY); + if (obj->fd < 0) { + err = -errno; + pr_warn("failed to open file '%s': %d\n", filename, err); + return err; + } + obj->elf = elf_begin(obj->fd, ELF_C_READ_MMAP, NULL); + if (!obj->elf) { + err = -errno; + pr_warn_elf("failed to parse ELF file '%s'", filename); + return err; + } + + /* Sanity check ELF file high-level properties */ + ehdr = elf64_getehdr(obj->elf); + if (!ehdr) { + err = -errno; + pr_warn_elf("failed to get ELF header for %s", filename); + return err; + } + if (ehdr->e_ident[EI_DATA] != host_endianness) { + err = -EOPNOTSUPP; + pr_warn_elf("unsupported byte order of ELF file %s", filename); + return err; + } + if (ehdr->e_type != ET_REL + || ehdr->e_machine != EM_BPF + || ehdr->e_ident[EI_CLASS] != ELFCLASS64) { + err = -EOPNOTSUPP; + pr_warn_elf("unsupported kind of ELF file %s", filename); + return err; + } + + if (elf_getshdrstrndx(obj->elf, &obj->shstrs_sec_idx)) { + err = -errno; + pr_warn_elf("failed to get SHSTRTAB section index for %s", filename); + return err; + } + + scn = NULL; + while ((scn = elf_nextscn(obj->elf, scn)) != NULL) { + size_t sec_idx = elf_ndxscn(scn); + const char *sec_name; + + shdr = elf64_getshdr(scn); + if (!shdr) { + err = -errno; + pr_warn_elf("failed to get section #%zu header for %s", + sec_idx, filename); + return err; + } + + sec_name = elf_strptr(obj->elf, obj->shstrs_sec_idx, shdr->sh_name); + if (!sec_name) { + err = -errno; + pr_warn_elf("failed to get section #%zu name for %s", + sec_idx, filename); + return err; + } + + data = elf_getdata(scn, 0); + if (!data) { + err = -errno; + pr_warn_elf("failed to get section #%zu (%s) data from %s", + sec_idx, sec_name, filename); + return err; + } + + sec = add_src_sec(obj, sec_name); + if (!sec) + return -ENOMEM; + + sec->scn = scn; + sec->shdr = shdr; + sec->data = data; + sec->sec_idx = elf_ndxscn(scn); + + if (is_ignored_sec(sec)) { + sec->skipped = true; + continue; + } + + switch (shdr->sh_type) { + case SHT_SYMTAB: + if (obj->symtab_sec_idx) { + err = -EOPNOTSUPP; + pr_warn("multiple SYMTAB sections found, not supported\n"); + return err; + } + obj->symtab_sec_idx = sec_idx; + break; + case SHT_STRTAB: + /* we'll construct our own string table */ + break; + case SHT_PROGBITS: + if (strcmp(sec_name, BTF_ELF_SEC) == 0) { + sec->skipped = true; + continue; + } + if (strcmp(sec_name, BTF_EXT_ELF_SEC) == 0) { + sec->skipped = true; + continue; + } + + /* data & code */ + break; + case SHT_NOBITS: + /* BSS */ + break; + case SHT_REL: + /* relocations */ + break; + default: + pr_warn("unrecognized section #%zu (%s) in %s\n", + sec_idx, sec_name, filename); + err = -EINVAL; + return err; + } + } + + err = err ?: linker_sanity_check_elf(obj); + + return err; +} + +static bool is_pow_of_2(size_t x) +{ + return x && (x & (x - 1)) == 0; +} + +static int linker_sanity_check_elf(struct src_obj *obj) +{ + struct src_sec *sec, *link_sec; + int i, j, n; + + if (!obj->symtab_sec_idx) { + pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename); + return -EINVAL; + } + if (!obj->shstrs_sec_idx) { + pr_warn("ELF is missing section headers STRTAB section in %s\n", obj->filename); + return -EINVAL; + } + + for (i = 1; i < obj->sec_cnt; i++) { + sec = &obj->secs[i]; + + if (sec->sec_name[0] == '\0') { + pr_warn("ELF section #%zu has empty name in %s\n", sec->sec_idx, obj->filename); + return -EINVAL; + } + + if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign)) + return -EINVAL; + if (sec->shdr->sh_addralign != sec->data->d_align) + return -EINVAL; + + if (sec->shdr->sh_size != sec->data->d_size) + return -EINVAL; + + switch (sec->shdr->sh_type) { + case SHT_SYMTAB: { + Elf64_Sym *sym; + + if (sec->shdr->sh_entsize != sizeof(Elf64_Sym)) + return -EINVAL; + if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0) + return -EINVAL; + + if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) { + pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n", + sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename); + return -EINVAL; + } + link_sec = &obj->secs[sec->shdr->sh_link]; + if (link_sec->shdr->sh_type != SHT_STRTAB) { + pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n", + sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename); + return -EINVAL; + } + + n = sec->shdr->sh_size / sec->shdr->sh_entsize; + sym = sec->data->d_buf; + for (j = 0; j < n; j++, sym++) { + if (sym->st_shndx + && sym->st_shndx < SHN_LORESERVE + && sym->st_shndx >= obj->sec_cnt) { + pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n", + j, sec->sec_idx, (size_t)sym->st_shndx, obj->filename); + return -EINVAL; + } + if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION) { + if (sym->st_value != 0) + return -EINVAL; + } + } + break; + } + case SHT_STRTAB: + break; + case SHT_PROGBITS: + if (sec->shdr->sh_flags & SHF_EXECINSTR) { + if (sec->shdr->sh_size % sizeof(struct bpf_insn) != 0) + return -EINVAL; + } + break; + case SHT_NOBITS: + break; + case SHT_REL: { + Elf64_Rel *relo; + struct src_sec *sym_sec; + + if (sec->shdr->sh_entsize != sizeof(Elf64_Rel)) + return -EINVAL; + if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0) + return -EINVAL; + + /* SHT_REL's sh_link should point to SYMTAB */ + if (sec->shdr->sh_link != obj->symtab_sec_idx) { + pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n", + sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename); + return -EINVAL; + } + + /* SHT_REL's sh_info points to relocated section */ + if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) { + pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n", + sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename); + return -EINVAL; + } + link_sec = &obj->secs[sec->shdr->sh_info]; + + /* .rel<secname> -> <secname> pattern is followed */ + if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0 + || strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) { + pr_warn("ELF relo section #%zu name has invalid name in %s\n", + sec->sec_idx, obj->filename); + return -EINVAL; + } + + /* don't further validate relocations for ignored sections */ + if (link_sec->skipped) + break; + + /* relocatable section is data or instructions */ + if (link_sec->shdr->sh_type != SHT_PROGBITS + && link_sec->shdr->sh_type != SHT_NOBITS) { + pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n", + sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename); + return -EINVAL; + } + + /* check sanity of each relocation */ + n = sec->shdr->sh_size / sec->shdr->sh_entsize; + relo = sec->data->d_buf; + sym_sec = &obj->secs[obj->symtab_sec_idx]; + for (j = 0; j < n; j++, relo++) { + size_t sym_idx = ELF64_R_SYM(relo->r_info); + size_t sym_type = ELF64_R_TYPE(relo->r_info); + + if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32) { + pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n", + j, sec->sec_idx, sym_type, obj->filename); + return -EINVAL; + } + + if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) { + pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n", + j, sec->sec_idx, sym_idx, obj->filename); + return -EINVAL; + } + + if (link_sec->shdr->sh_flags & SHF_EXECINSTR) { + if (relo->r_offset % sizeof(struct bpf_insn) != 0) { + pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n", + j, sec->sec_idx, sym_idx, obj->filename); + return -EINVAL; + } + } + } + break; + } + case SHT_LLVM_ADDRSIG: + break; + default: + pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n", + sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename); + return -EINVAL; + } + } + + return 0; +} + +static int init_sec(struct bpf_linker *linker, struct dst_sec *dst_sec, struct src_sec *src_sec) +{ + Elf_Scn *scn; + Elf_Data *data; + Elf64_Shdr *shdr; + int name_off; + + dst_sec->sec_sz = 0; + dst_sec->sec_idx = 0; + + scn = elf_newscn(linker->elf); + if (!scn) + return -1; + data = elf_newdata(scn); + if (!data) + return -1; + shdr = elf64_getshdr(scn); + if (!shdr) + return -1; + + dst_sec->scn = scn; + dst_sec->shdr = shdr; + dst_sec->data = data; + dst_sec->sec_idx = elf_ndxscn(scn); + + name_off = strset__add_str(linker->strtab_strs, src_sec->sec_name); + if (name_off < 0) + return name_off; + + shdr->sh_name = name_off; + shdr->sh_type = src_sec->shdr->sh_type; + shdr->sh_flags = src_sec->shdr->sh_flags; + shdr->sh_size = 0; + /* sh_link and sh_info have different meaning for different types of + * sections, so we leave it up to the caller code to fill them in, if + * necessary + */ + shdr->sh_link = 0; + shdr->sh_info = 0; + shdr->sh_addralign = src_sec->shdr->sh_addralign; + shdr->sh_entsize = src_sec->shdr->sh_entsize; + + data->d_type = src_sec->data->d_type; + data->d_size = 0; + data->d_buf = NULL; + data->d_align = src_sec->data->d_align; + data->d_off = 0; + + return 0; +} + +static struct dst_sec *find_dst_sec_by_name(struct bpf_linker *linker, const char *sec_name) +{ + struct dst_sec *sec; + int i; + + for (i = 1; i < linker->sec_cnt; i++) { + sec = &linker->secs[i]; + + if (strcmp(sec->sec_name, sec_name) == 0) + return sec; + } + + return NULL; +} + +static bool secs_match(struct dst_sec *dst, struct src_sec *src) +{ + if (dst->shdr->sh_type != src->shdr->sh_type) { + pr_warn("sec %s types mismatch\n", dst->sec_name); + return false; + } + if (dst->shdr->sh_flags != src->shdr->sh_flags) { + pr_warn("sec %s flags mismatch\n", dst->sec_name); + return false; + } + if (dst->shdr->sh_entsize != src->shdr->sh_entsize) { + pr_warn("sec %s entsize mismatch\n", dst->sec_name); + return false; + } + + return true; +} + +static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec) +{ + if (dst_sec->sec_sz != src_sec->shdr->sh_size) + return false; + if (memcmp(dst_sec->raw_data, src_sec->data->d_buf, dst_sec->sec_sz) != 0) + return false; + return true; +} + +static int extend_sec(struct dst_sec *dst, struct src_sec *src) +{ + void *tmp; + size_t dst_align = dst->shdr->sh_addralign; + size_t src_align = src->shdr->sh_addralign; + size_t dst_align_sz, dst_final_sz; + + if (dst_align == 0) + dst_align = 1; + if (dst_align < src_align) + dst_align = src_align; + + dst_align_sz = (dst->sec_sz + dst_align - 1) / dst_align * dst_align; + + /* no need to re-align final size */ + dst_final_sz = dst_align_sz + src->shdr->sh_size; + + if (src->shdr->sh_type != SHT_NOBITS) { + tmp = realloc(dst->raw_data, dst_final_sz); + if (!tmp) + return -ENOMEM; + dst->raw_data = tmp; + + /* pad dst section, if it's alignment forced size increase */ + memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz); + /* now copy src data at a properly aligned offset */ + memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size); + } + + dst->sec_sz = dst_final_sz; + dst->shdr->sh_size = dst_final_sz; + dst->data->d_size = dst_final_sz; + + dst->shdr->sh_addralign = dst_align; + dst->data->d_align = dst_align; + + src->dst_off = dst_align_sz; + + return 0; +} + +static bool is_data_sec(struct src_sec *sec) +{ + if (!sec || sec->skipped) + return false; + return sec->shdr->sh_type == SHT_PROGBITS || sec->shdr->sh_type == SHT_NOBITS; +} + +static bool is_relo_sec(struct src_sec *sec) +{ + if (!sec || sec->skipped) + return false; + return sec->shdr->sh_type == SHT_REL; +} + +static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj) +{ + int i, err; + + for (i = 1; i < obj->sec_cnt; i++) { + struct src_sec *src_sec; + struct dst_sec *dst_sec; + + src_sec = &obj->secs[i]; + if (!is_data_sec(src_sec)) + continue; + + dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name); + if (!dst_sec) { + dst_sec = add_dst_sec(linker, src_sec->sec_name); + if (!dst_sec) + return -ENOMEM; + err = init_sec(linker, dst_sec, src_sec); + if (err) { + pr_warn("failed to init section '%s'\n", src_sec->sec_name); + return err; + } + } else { + if (!secs_match(dst_sec, src_sec)) { + pr_warn("ELF sections %s are incompatible\n", src_sec->sec_name); + return -1; + } + + /* "license" and "version" sections are deduped */ + if (strcmp(src_sec->sec_name, "license") == 0 + || strcmp(src_sec->sec_name, "version") == 0) { + if (!sec_content_is_same(dst_sec, src_sec)) { + pr_warn("non-identical contents of section '%s' are not supported\n", src_sec->sec_name); + return -EINVAL; + } + src_sec->skipped = true; + src_sec->dst_id = dst_sec->id; + continue; + } + } + + /* record mapped section index */ + src_sec->dst_id = dst_sec->id; + + err = extend_sec(dst_sec, src_sec); + if (err) + return err; + } + + return 0; +} + +static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj) +{ + struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx]; + Elf64_Sym *sym = symtab->data->d_buf, *dst_sym; + int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize; + int str_sec_idx = symtab->shdr->sh_link; + + obj->sym_map = calloc(n + 1, sizeof(*obj->sym_map)); + if (!obj->sym_map) + return -ENOMEM; + + for (i = 0; i < n; i++, sym++) { + struct src_sec *src_sec = NULL; + struct dst_sec *dst_sec = NULL; + const char *sym_name; + size_t dst_sym_idx; + int name_off; + + /* we already have all-zero initial symbol */ + if (sym->st_name == 0 && sym->st_info == 0 && + sym->st_other == 0 && sym->st_shndx == SHN_UNDEF && + sym->st_value == 0 && sym->st_size ==0) + continue; + + sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name); + if (!sym_name) { + pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename); + return -1; + } + + if (sym->st_shndx && sym->st_shndx < SHN_LORESERVE) { + src_sec = &obj->secs[sym->st_shndx]; + if (src_sec->skipped) + continue; + dst_sec = &linker->secs[src_sec->dst_id]; + + /* allow only one STT_SECTION symbol per section */ + if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && dst_sec->sec_sym_idx) { + obj->sym_map[i] = dst_sec->sec_sym_idx; + continue; + } + } + + name_off = strset__add_str(linker->strtab_strs, sym_name); + if (name_off < 0) + return name_off; + + dst_sym = add_new_sym(linker, &dst_sym_idx); + if (!dst_sym) + return -ENOMEM; + + dst_sym->st_name = name_off; + dst_sym->st_info = sym->st_info; + dst_sym->st_other = sym->st_other; + dst_sym->st_shndx = src_sec ? dst_sec->sec_idx : sym->st_shndx; + dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value; + dst_sym->st_size = sym->st_size; + + obj->sym_map[i] = dst_sym_idx; + + if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && dst_sym) { + dst_sec->sec_sym_idx = dst_sym_idx; + dst_sym->st_value = 0; + } + + } + + return 0; +} + +static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj) +{ + struct src_sec *src_symtab = &obj->secs[obj->symtab_sec_idx]; + struct dst_sec *dst_symtab = &linker->secs[linker->symtab_sec_idx]; + int i, err; + + for (i = 1; i < obj->sec_cnt; i++) { + struct src_sec *src_sec, *src_linked_sec; + struct dst_sec *dst_sec, *dst_linked_sec; + Elf64_Rel *src_rel, *dst_rel; + int j, n; + + src_sec = &obj->secs[i]; + if (!is_relo_sec(src_sec)) + continue; + + /* shdr->sh_info points to relocatable section */ + src_linked_sec = &obj->secs[src_sec->shdr->sh_info]; + if (src_linked_sec->skipped) + continue; + + dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name); + if (!dst_sec) { + dst_sec = add_dst_sec(linker, src_sec->sec_name); + if (!dst_sec) + return -ENOMEM; + err = init_sec(linker, dst_sec, src_sec); + if (err) { + pr_warn("failed to init section '%s'\n", src_sec->sec_name); + return err; + } + } else if (!secs_match(dst_sec, src_sec)) { + pr_warn("Secs %s are not compatible\n", src_sec->sec_name); + return -1; + } + + /* shdr->sh_link points to SYMTAB */ + dst_sec->shdr->sh_link = linker->symtab_sec_idx; + + /* shdr->sh_info points to relocated section */ + dst_linked_sec = &linker->secs[src_linked_sec->dst_id]; + dst_sec->shdr->sh_info = dst_linked_sec->sec_idx; + + src_sec->dst_id = dst_sec->id; + err = extend_sec(dst_sec, src_sec); + if (err) + return err; + + src_rel = src_sec->data->d_buf; + dst_rel = dst_sec->raw_data + src_sec->dst_off; + n = src_sec->shdr->sh_size / src_sec->shdr->sh_entsize; + for (j = 0; j < n; j++, src_rel++, dst_rel++) { + size_t src_sym_idx = ELF64_R_SYM(src_rel->r_info); + size_t sym_type = ELF64_R_TYPE(src_rel->r_info); + Elf64_Sym *src_sym, *dst_sym; + size_t dst_sym_idx; + + src_sym_idx = ELF64_R_SYM(src_rel->r_info); + src_sym = src_symtab->data->d_buf + sizeof(*src_sym) * src_sym_idx; + + dst_sym_idx = obj->sym_map[src_sym_idx]; + dst_sym = dst_symtab->raw_data + sizeof(*dst_sym) * dst_sym_idx; + dst_rel->r_offset += src_linked_sec->dst_off; + sym_type = ELF64_R_TYPE(src_rel->r_info); + dst_rel->r_info = ELF64_R_INFO(dst_sym_idx, sym_type); + + if (ELF64_ST_TYPE(src_sym->st_info) == STT_SECTION) { + struct src_sec *sec = &obj->secs[src_sym->st_shndx]; + struct bpf_insn *insn; + + if (src_linked_sec->shdr->sh_flags & SHF_EXECINSTR) { + /* calls to the very first static function inside + * .text section at offset 0 will + * reference section symbol, not the + * function symbol. Fix that up, + * otherwise it won't be possible to + * relocate calls to two different + * static functions with the same name + * (rom two different object files) + */ + insn = dst_linked_sec->raw_data + dst_rel->r_offset; + if (insn->code == (BPF_JMP | BPF_CALL)) + insn->imm += sec->dst_off / sizeof(struct bpf_insn); + else + insn->imm += sec->dst_off; + } else { + pr_warn("relocation against STT_SECTION in non-exec section is not supported!\n"); + return -EINVAL; + } + } + + } + } + + return 0; +} + +int bpf_linker__finalize(struct bpf_linker *linker) +{ + struct dst_sec *sec; + size_t strs_sz; + const void *strs; + int err, i; + + if (!linker->elf) + return -EINVAL; + + /* Finalize strings */ + strs_sz = strset__data_size(linker->strtab_strs); + strs = strset__data(linker->strtab_strs); + + sec = &linker->secs[linker->strtab_sec_idx]; + sec->data->d_align = 1; + sec->data->d_off = 0LL; + sec->data->d_buf = (void *)strs; + sec->data->d_type = ELF_T_BYTE; + sec->data->d_size = strs_sz; + sec->shdr->sh_size = strs_sz; + + for (i = 1; i < linker->sec_cnt; i++) { + sec = &linker->secs[i]; + + /* STRTAB is handled specially above */ + if (sec->sec_idx == linker->strtab_sec_idx) + continue; + + sec->data->d_buf = sec->raw_data; + } + + /* Finalize ELF layout */ + if (elf_update(linker->elf, ELF_C_NULL) < 0) { + err = -errno; + pr_warn_elf("failed to finalize ELF layout"); + return err; + } + + /* Write out final ELF contents */ + if (elf_update(linker->elf, ELF_C_WRITE) < 0) { + err = -errno; + pr_warn_elf("failed to write ELF contents"); + return err; + } + + elf_end(linker->elf); + close(linker->fd); + + linker->elf = NULL; + linker->fd = -1; + + return 0; +} |