| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * elf.c - ELF access library |
| * |
| * Adapted from kpatch (https://github.com/dynup/kpatch): |
| * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com> |
| * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> |
| */ |
| |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <sys/mman.h> |
| #include <fcntl.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <unistd.h> |
| #include <errno.h> |
| #include <objtool/builtin.h> |
| |
| #include <objtool/elf.h> |
| #include <objtool/warn.h> |
| |
| #define MAX_NAME_LEN 128 |
| |
| static inline u32 str_hash(const char *str) |
| { |
| return jhash(str, strlen(str), 0); |
| } |
| |
| #define __elf_table(name) (elf->name##_hash) |
| #define __elf_bits(name) (elf->name##_bits) |
| |
| #define elf_hash_add(name, node, key) \ |
| hlist_add_head(node, &__elf_table(name)[hash_min(key, __elf_bits(name))]) |
| |
| #define elf_hash_for_each_possible(name, obj, member, key) \ |
| hlist_for_each_entry(obj, &__elf_table(name)[hash_min(key, __elf_bits(name))], member) |
| |
| #define elf_alloc_hash(name, size) \ |
| ({ \ |
| __elf_bits(name) = max(10, ilog2(size)); \ |
| __elf_table(name) = mmap(NULL, sizeof(struct hlist_head) << __elf_bits(name), \ |
| PROT_READ|PROT_WRITE, \ |
| MAP_PRIVATE|MAP_ANON, -1, 0); \ |
| if (__elf_table(name) == (void *)-1L) { \ |
| WARN("mmap fail " #name); \ |
| __elf_table(name) = NULL; \ |
| } \ |
| __elf_table(name); \ |
| }) |
| |
| static bool symbol_to_offset(struct rb_node *a, const struct rb_node *b) |
| { |
| struct symbol *sa = rb_entry(a, struct symbol, node); |
| struct symbol *sb = rb_entry(b, struct symbol, node); |
| |
| if (sa->offset < sb->offset) |
| return true; |
| if (sa->offset > sb->offset) |
| return false; |
| |
| if (sa->len < sb->len) |
| return true; |
| if (sa->len > sb->len) |
| return false; |
| |
| sa->alias = sb; |
| |
| return false; |
| } |
| |
| static int symbol_by_offset(const void *key, const struct rb_node *node) |
| { |
| const struct symbol *s = rb_entry(node, struct symbol, node); |
| const unsigned long *o = key; |
| |
| if (*o < s->offset) |
| return -1; |
| if (*o >= s->offset + s->len) |
| return 1; |
| |
| return 0; |
| } |
| |
| struct section *find_section_by_name(const struct elf *elf, const char *name) |
| { |
| struct section *sec; |
| |
| elf_hash_for_each_possible(section_name, sec, name_hash, str_hash(name)) { |
| if (!strcmp(sec->name, name)) |
| return sec; |
| } |
| |
| return NULL; |
| } |
| |
| static struct section *find_section_by_index(struct elf *elf, |
| unsigned int idx) |
| { |
| struct section *sec; |
| |
| elf_hash_for_each_possible(section, sec, hash, idx) { |
| if (sec->idx == idx) |
| return sec; |
| } |
| |
| return NULL; |
| } |
| |
| static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx) |
| { |
| struct symbol *sym; |
| |
| elf_hash_for_each_possible(symbol, sym, hash, idx) { |
| if (sym->idx == idx) |
| return sym; |
| } |
| |
| return NULL; |
| } |
| |
| struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset) |
| { |
| struct rb_node *node; |
| |
| rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) { |
| struct symbol *s = rb_entry(node, struct symbol, node); |
| |
| if (s->offset == offset && s->type != STT_SECTION) |
| return s; |
| } |
| |
| return NULL; |
| } |
| |
| struct symbol *find_func_by_offset(struct section *sec, unsigned long offset) |
| { |
| struct rb_node *node; |
| |
| rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) { |
| struct symbol *s = rb_entry(node, struct symbol, node); |
| |
| if (s->offset == offset && s->type == STT_FUNC) |
| return s; |
| } |
| |
| return NULL; |
| } |
| |
| struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset) |
| { |
| struct rb_node *node; |
| |
| rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) { |
| struct symbol *s = rb_entry(node, struct symbol, node); |
| |
| if (s->type != STT_SECTION) |
| return s; |
| } |
| |
| return NULL; |
| } |
| |
| struct symbol *find_func_containing(struct section *sec, unsigned long offset) |
| { |
| struct rb_node *node; |
| |
| rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) { |
| struct symbol *s = rb_entry(node, struct symbol, node); |
| |
| if (s->type == STT_FUNC) |
| return s; |
| } |
| |
| return NULL; |
| } |
| |
| struct symbol *find_symbol_by_name(const struct elf *elf, const char *name) |
| { |
| struct symbol *sym; |
| |
| elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) { |
| if (!strcmp(sym->name, name)) |
| return sym; |
| } |
| |
| return NULL; |
| } |
| |
| struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec, |
| unsigned long offset, unsigned int len) |
| { |
| struct reloc *reloc, *r = NULL; |
| unsigned long o; |
| |
| if (!sec->reloc) |
| return NULL; |
| |
| sec = sec->reloc; |
| |
| for_offset_range(o, offset, offset + len) { |
| elf_hash_for_each_possible(reloc, reloc, hash, |
| sec_offset_hash(sec, o)) { |
| if (reloc->sec != sec) |
| continue; |
| |
| if (reloc->offset >= offset && reloc->offset < offset + len) { |
| if (!r || reloc->offset < r->offset) |
| r = reloc; |
| } |
| } |
| if (r) |
| return r; |
| } |
| |
| return NULL; |
| } |
| |
| struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset) |
| { |
| return find_reloc_by_dest_range(elf, sec, offset, 1); |
| } |
| |
| static int read_sections(struct elf *elf) |
| { |
| Elf_Scn *s = NULL; |
| struct section *sec; |
| size_t shstrndx, sections_nr; |
| int i; |
| |
| if (elf_getshdrnum(elf->elf, §ions_nr)) { |
| WARN_ELF("elf_getshdrnum"); |
| return -1; |
| } |
| |
| if (elf_getshdrstrndx(elf->elf, &shstrndx)) { |
| WARN_ELF("elf_getshdrstrndx"); |
| return -1; |
| } |
| |
| if (!elf_alloc_hash(section, sections_nr) || |
| !elf_alloc_hash(section_name, sections_nr)) |
| return -1; |
| |
| for (i = 0; i < sections_nr; i++) { |
| sec = malloc(sizeof(*sec)); |
| if (!sec) { |
| perror("malloc"); |
| return -1; |
| } |
| memset(sec, 0, sizeof(*sec)); |
| |
| INIT_LIST_HEAD(&sec->symbol_list); |
| INIT_LIST_HEAD(&sec->reloc_list); |
| |
| s = elf_getscn(elf->elf, i); |
| if (!s) { |
| WARN_ELF("elf_getscn"); |
| return -1; |
| } |
| |
| sec->idx = elf_ndxscn(s); |
| |
| if (!gelf_getshdr(s, &sec->sh)) { |
| WARN_ELF("gelf_getshdr"); |
| return -1; |
| } |
| |
| sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name); |
| if (!sec->name) { |
| WARN_ELF("elf_strptr"); |
| return -1; |
| } |
| |
| if (sec->sh.sh_size != 0) { |
| sec->data = elf_getdata(s, NULL); |
| if (!sec->data) { |
| WARN_ELF("elf_getdata"); |
| return -1; |
| } |
| if (sec->data->d_off != 0 || |
| sec->data->d_size != sec->sh.sh_size) { |
| WARN("unexpected data attributes for %s", |
| sec->name); |
| return -1; |
| } |
| } |
| sec->len = sec->sh.sh_size; |
| |
| if (sec->sh.sh_flags & SHF_EXECINSTR) |
| elf->text_size += sec->len; |
| |
| list_add_tail(&sec->list, &elf->sections); |
| elf_hash_add(section, &sec->hash, sec->idx); |
| elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name)); |
| } |
| |
| if (stats) { |
| printf("nr_sections: %lu\n", (unsigned long)sections_nr); |
| printf("section_bits: %d\n", elf->section_bits); |
| } |
| |
| /* sanity check, one more call to elf_nextscn() should return NULL */ |
| if (elf_nextscn(elf->elf, s)) { |
| WARN("section entry mismatch"); |
| return -1; |
| } |
| |
| return 0; |
| } |
| |
| static void elf_add_symbol(struct elf *elf, struct symbol *sym) |
| { |
| struct list_head *entry; |
| struct rb_node *pnode; |
| |
| sym->type = GELF_ST_TYPE(sym->sym.st_info); |
| sym->bind = GELF_ST_BIND(sym->sym.st_info); |
| |
| sym->offset = sym->sym.st_value; |
| sym->len = sym->sym.st_size; |
| |
| rb_add(&sym->node, &sym->sec->symbol_tree, symbol_to_offset); |
| pnode = rb_prev(&sym->node); |
| if (pnode) |
| entry = &rb_entry(pnode, struct symbol, node)->list; |
| else |
| entry = &sym->sec->symbol_list; |
| list_add(&sym->list, entry); |
| elf_hash_add(symbol, &sym->hash, sym->idx); |
| elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name)); |
| |
| /* |
| * Don't store empty STT_NOTYPE symbols in the rbtree. They |
| * can exist within a function, confusing the sorting. |
| */ |
| if (!sym->len) |
| rb_erase(&sym->node, &sym->sec->symbol_tree); |
| } |
| |
| static int read_symbols(struct elf *elf) |
| { |
| struct section *symtab, *symtab_shndx, *sec; |
| struct symbol *sym, *pfunc; |
| int symbols_nr, i; |
| char *coldstr; |
| Elf_Data *shndx_data = NULL; |
| Elf32_Word shndx; |
| |
| symtab = find_section_by_name(elf, ".symtab"); |
| if (symtab) { |
| symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); |
| if (symtab_shndx) |
| shndx_data = symtab_shndx->data; |
| |
| symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize; |
| } else { |
| /* |
| * A missing symbol table is actually possible if it's an empty |
| * .o file. This can happen for thunk_64.o. Make sure to at |
| * least allocate the symbol hash tables so we can do symbol |
| * lookups without crashing. |
| */ |
| symbols_nr = 0; |
| } |
| |
| if (!elf_alloc_hash(symbol, symbols_nr) || |
| !elf_alloc_hash(symbol_name, symbols_nr)) |
| return -1; |
| |
| for (i = 0; i < symbols_nr; i++) { |
| sym = malloc(sizeof(*sym)); |
| if (!sym) { |
| perror("malloc"); |
| return -1; |
| } |
| memset(sym, 0, sizeof(*sym)); |
| sym->alias = sym; |
| |
| sym->idx = i; |
| |
| if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym, |
| &shndx)) { |
| WARN_ELF("gelf_getsymshndx"); |
| goto err; |
| } |
| |
| sym->name = elf_strptr(elf->elf, symtab->sh.sh_link, |
| sym->sym.st_name); |
| if (!sym->name) { |
| WARN_ELF("elf_strptr"); |
| goto err; |
| } |
| |
| if ((sym->sym.st_shndx > SHN_UNDEF && |
| sym->sym.st_shndx < SHN_LORESERVE) || |
| (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) { |
| if (sym->sym.st_shndx != SHN_XINDEX) |
| shndx = sym->sym.st_shndx; |
| |
| sym->sec = find_section_by_index(elf, shndx); |
| if (!sym->sec) { |
| WARN("couldn't find section for symbol %s", |
| sym->name); |
| goto err; |
| } |
| if (GELF_ST_TYPE(sym->sym.st_info) == STT_SECTION) { |
| sym->name = sym->sec->name; |
| sym->sec->sym = sym; |
| } |
| } else |
| sym->sec = find_section_by_index(elf, 0); |
| |
| elf_add_symbol(elf, sym); |
| } |
| |
| if (stats) { |
| printf("nr_symbols: %lu\n", (unsigned long)symbols_nr); |
| printf("symbol_bits: %d\n", elf->symbol_bits); |
| } |
| |
| /* Create parent/child links for any cold subfunctions */ |
| list_for_each_entry(sec, &elf->sections, list) { |
| list_for_each_entry(sym, &sec->symbol_list, list) { |
| char pname[MAX_NAME_LEN + 1]; |
| size_t pnamelen; |
| if (sym->type != STT_FUNC) |
| continue; |
| |
| if (sym->pfunc == NULL) |
| sym->pfunc = sym; |
| |
| if (sym->cfunc == NULL) |
| sym->cfunc = sym; |
| |
| coldstr = strstr(sym->name, ".cold"); |
| if (!coldstr) |
| continue; |
| |
| pnamelen = coldstr - sym->name; |
| if (pnamelen > MAX_NAME_LEN) { |
| WARN("%s(): parent function name exceeds maximum length of %d characters", |
| sym->name, MAX_NAME_LEN); |
| return -1; |
| } |
| |
| strncpy(pname, sym->name, pnamelen); |
| pname[pnamelen] = '\0'; |
| pfunc = find_symbol_by_name(elf, pname); |
| |
| if (!pfunc) { |
| WARN("%s(): can't find parent function", |
| sym->name); |
| return -1; |
| } |
| |
| sym->pfunc = pfunc; |
| pfunc->cfunc = sym; |
| |
| /* |
| * Unfortunately, -fnoreorder-functions puts the child |
| * inside the parent. Remove the overlap so we can |
| * have sane assumptions. |
| * |
| * Note that pfunc->len now no longer matches |
| * pfunc->sym.st_size. |
| */ |
| if (sym->sec == pfunc->sec && |
| sym->offset >= pfunc->offset && |
| sym->offset + sym->len == pfunc->offset + pfunc->len) { |
| pfunc->len -= sym->len; |
| } |
| } |
| } |
| |
| return 0; |
| |
| err: |
| free(sym); |
| return -1; |
| } |
| |
| static struct section *elf_create_reloc_section(struct elf *elf, |
| struct section *base, |
| int reltype); |
| |
| int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset, |
| unsigned int type, struct symbol *sym, int addend) |
| { |
| struct reloc *reloc; |
| |
| if (!sec->reloc && !elf_create_reloc_section(elf, sec, SHT_RELA)) |
| return -1; |
| |
| reloc = malloc(sizeof(*reloc)); |
| if (!reloc) { |
| perror("malloc"); |
| return -1; |
| } |
| memset(reloc, 0, sizeof(*reloc)); |
| |
| reloc->sec = sec->reloc; |
| reloc->offset = offset; |
| reloc->type = type; |
| reloc->sym = sym; |
| reloc->addend = addend; |
| |
| list_add_tail(&reloc->list, &sec->reloc->reloc_list); |
| elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc)); |
| |
| sec->reloc->changed = true; |
| |
| return 0; |
| } |
| |
| int elf_add_reloc_to_insn(struct elf *elf, struct section *sec, |
| unsigned long offset, unsigned int type, |
| struct section *insn_sec, unsigned long insn_off) |
| { |
| struct symbol *sym; |
| int addend; |
| |
| if (insn_sec->sym) { |
| sym = insn_sec->sym; |
| addend = insn_off; |
| |
| } else { |
| /* |
| * The Clang assembler strips section symbols, so we have to |
| * reference the function symbol instead: |
| */ |
| sym = find_symbol_containing(insn_sec, insn_off); |
| if (!sym) { |
| /* |
| * Hack alert. This happens when we need to reference |
| * the NOP pad insn immediately after the function. |
| */ |
| sym = find_symbol_containing(insn_sec, insn_off - 1); |
| } |
| |
| if (!sym) { |
| WARN("can't find symbol containing %s+0x%lx", insn_sec->name, insn_off); |
| return -1; |
| } |
| |
| addend = insn_off - sym->offset; |
| } |
| |
| return elf_add_reloc(elf, sec, offset, type, sym, addend); |
| } |
| |
| static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx) |
| { |
| if (!gelf_getrel(sec->data, i, &reloc->rel)) { |
| WARN_ELF("gelf_getrel"); |
| return -1; |
| } |
| reloc->type = GELF_R_TYPE(reloc->rel.r_info); |
| reloc->addend = 0; |
| reloc->offset = reloc->rel.r_offset; |
| *symndx = GELF_R_SYM(reloc->rel.r_info); |
| return 0; |
| } |
| |
| static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx) |
| { |
| if (!gelf_getrela(sec->data, i, &reloc->rela)) { |
| WARN_ELF("gelf_getrela"); |
| return -1; |
| } |
| reloc->type = GELF_R_TYPE(reloc->rela.r_info); |
| reloc->addend = reloc->rela.r_addend; |
| reloc->offset = reloc->rela.r_offset; |
| *symndx = GELF_R_SYM(reloc->rela.r_info); |
| return 0; |
| } |
| |
| static int read_relocs(struct elf *elf) |
| { |
| struct section *sec; |
| struct reloc *reloc; |
| int i; |
| unsigned int symndx; |
| unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0; |
| |
| if (!elf_alloc_hash(reloc, elf->text_size / 16)) |
| return -1; |
| |
| list_for_each_entry(sec, &elf->sections, list) { |
| if ((sec->sh.sh_type != SHT_RELA) && |
| (sec->sh.sh_type != SHT_REL)) |
| continue; |
| |
| sec->base = find_section_by_index(elf, sec->sh.sh_info); |
| if (!sec->base) { |
| WARN("can't find base section for reloc section %s", |
| sec->name); |
| return -1; |
| } |
| |
| sec->base->reloc = sec; |
| |
| nr_reloc = 0; |
| for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) { |
| reloc = malloc(sizeof(*reloc)); |
| if (!reloc) { |
| perror("malloc"); |
| return -1; |
| } |
| memset(reloc, 0, sizeof(*reloc)); |
| switch (sec->sh.sh_type) { |
| case SHT_REL: |
| if (read_rel_reloc(sec, i, reloc, &symndx)) |
| return -1; |
| break; |
| case SHT_RELA: |
| if (read_rela_reloc(sec, i, reloc, &symndx)) |
| return -1; |
| break; |
| default: return -1; |
| } |
| |
| reloc->sec = sec; |
| reloc->idx = i; |
| reloc->sym = find_symbol_by_index(elf, symndx); |
| if (!reloc->sym) { |
| WARN("can't find reloc entry symbol %d for %s", |
| symndx, sec->name); |
| return -1; |
| } |
| |
| list_add_tail(&reloc->list, &sec->reloc_list); |
| elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc)); |
| |
| nr_reloc++; |
| } |
| max_reloc = max(max_reloc, nr_reloc); |
| tot_reloc += nr_reloc; |
| } |
| |
| if (stats) { |
| printf("max_reloc: %lu\n", max_reloc); |
| printf("tot_reloc: %lu\n", tot_reloc); |
| printf("reloc_bits: %d\n", elf->reloc_bits); |
| } |
| |
| return 0; |
| } |
| |
| struct elf *elf_open_read(const char *name, int flags) |
| { |
| struct elf *elf; |
| Elf_Cmd cmd; |
| |
| elf_version(EV_CURRENT); |
| |
| elf = malloc(sizeof(*elf)); |
| if (!elf) { |
| perror("malloc"); |
| return NULL; |
| } |
| memset(elf, 0, offsetof(struct elf, sections)); |
| |
| INIT_LIST_HEAD(&elf->sections); |
| |
| elf->fd = open(name, flags); |
| if (elf->fd == -1) { |
| fprintf(stderr, "objtool: Can't open '%s': %s\n", |
| name, strerror(errno)); |
| goto err; |
| } |
| |
| if ((flags & O_ACCMODE) == O_RDONLY) |
| cmd = ELF_C_READ_MMAP; |
| else if ((flags & O_ACCMODE) == O_RDWR) |
| cmd = ELF_C_RDWR; |
| else /* O_WRONLY */ |
| cmd = ELF_C_WRITE; |
| |
| elf->elf = elf_begin(elf->fd, cmd, NULL); |
| if (!elf->elf) { |
| WARN_ELF("elf_begin"); |
| goto err; |
| } |
| |
| if (!gelf_getehdr(elf->elf, &elf->ehdr)) { |
| WARN_ELF("gelf_getehdr"); |
| goto err; |
| } |
| |
| if (read_sections(elf)) |
| goto err; |
| |
| if (read_symbols(elf)) |
| goto err; |
| |
| if (read_relocs(elf)) |
| goto err; |
| |
| return elf; |
| |
| err: |
| elf_close(elf); |
| return NULL; |
| } |
| |
| static int elf_add_string(struct elf *elf, struct section *strtab, char *str) |
| { |
| Elf_Data *data; |
| Elf_Scn *s; |
| int len; |
| |
| if (!strtab) |
| strtab = find_section_by_name(elf, ".strtab"); |
| if (!strtab) { |
| WARN("can't find .strtab section"); |
| return -1; |
| } |
| |
| s = elf_getscn(elf->elf, strtab->idx); |
| if (!s) { |
| WARN_ELF("elf_getscn"); |
| return -1; |
| } |
| |
| data = elf_newdata(s); |
| if (!data) { |
| WARN_ELF("elf_newdata"); |
| return -1; |
| } |
| |
| data->d_buf = str; |
| data->d_size = strlen(str) + 1; |
| data->d_align = 1; |
| |
| len = strtab->len; |
| strtab->len += data->d_size; |
| strtab->changed = true; |
| |
| return len; |
| } |
| |
| struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) |
| { |
| struct section *symtab, *symtab_shndx; |
| struct symbol *sym; |
| Elf_Data *data; |
| Elf_Scn *s; |
| |
| sym = malloc(sizeof(*sym)); |
| if (!sym) { |
| perror("malloc"); |
| return NULL; |
| } |
| memset(sym, 0, sizeof(*sym)); |
| |
| sym->name = strdup(name); |
| |
| sym->sym.st_name = elf_add_string(elf, NULL, sym->name); |
| if (sym->sym.st_name == -1) |
| return NULL; |
| |
| sym->sym.st_info = GELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); |
| // st_other 0 |
| // st_shndx 0 |
| // st_value 0 |
| // st_size 0 |
| |
| symtab = find_section_by_name(elf, ".symtab"); |
| if (!symtab) { |
| WARN("can't find .symtab"); |
| return NULL; |
| } |
| |
| s = elf_getscn(elf->elf, symtab->idx); |
| if (!s) { |
| WARN_ELF("elf_getscn"); |
| return NULL; |
| } |
| |
| data = elf_newdata(s); |
| if (!data) { |
| WARN_ELF("elf_newdata"); |
| return NULL; |
| } |
| |
| data->d_buf = &sym->sym; |
| data->d_size = sizeof(sym->sym); |
| data->d_align = 1; |
| data->d_type = ELF_T_SYM; |
| |
| sym->idx = symtab->len / sizeof(sym->sym); |
| |
| symtab->len += data->d_size; |
| symtab->changed = true; |
| |
| symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); |
| if (symtab_shndx) { |
| s = elf_getscn(elf->elf, symtab_shndx->idx); |
| if (!s) { |
| WARN_ELF("elf_getscn"); |
| return NULL; |
| } |
| |
| data = elf_newdata(s); |
| if (!data) { |
| WARN_ELF("elf_newdata"); |
| return NULL; |
| } |
| |
| data->d_buf = &sym->sym.st_size; /* conveniently 0 */ |
| data->d_size = sizeof(Elf32_Word); |
| data->d_align = 4; |
| data->d_type = ELF_T_WORD; |
| |
| symtab_shndx->len += 4; |
| symtab_shndx->changed = true; |
| } |
| |
| sym->sec = find_section_by_index(elf, 0); |
| |
| elf_add_symbol(elf, sym); |
| |
| return sym; |
| } |
| |
| struct section *elf_create_section(struct elf *elf, const char *name, |
| unsigned int sh_flags, size_t entsize, int nr) |
| { |
| struct section *sec, *shstrtab; |
| size_t size = entsize * nr; |
| Elf_Scn *s; |
| |
| sec = malloc(sizeof(*sec)); |
| if (!sec) { |
| perror("malloc"); |
| return NULL; |
| } |
| memset(sec, 0, sizeof(*sec)); |
| |
| INIT_LIST_HEAD(&sec->symbol_list); |
| INIT_LIST_HEAD(&sec->reloc_list); |
| |
| s = elf_newscn(elf->elf); |
| if (!s) { |
| WARN_ELF("elf_newscn"); |
| return NULL; |
| } |
| |
| sec->name = strdup(name); |
| if (!sec->name) { |
| perror("strdup"); |
| return NULL; |
| } |
| |
| sec->idx = elf_ndxscn(s); |
| sec->len = size; |
| sec->changed = true; |
| |
| sec->data = elf_newdata(s); |
| if (!sec->data) { |
| WARN_ELF("elf_newdata"); |
| return NULL; |
| } |
| |
| sec->data->d_size = size; |
| sec->data->d_align = 1; |
| |
| if (size) { |
| sec->data->d_buf = malloc(size); |
| if (!sec->data->d_buf) { |
| perror("malloc"); |
| return NULL; |
| } |
| memset(sec->data->d_buf, 0, size); |
| } |
| |
| if (!gelf_getshdr(s, &sec->sh)) { |
| WARN_ELF("gelf_getshdr"); |
| return NULL; |
| } |
| |
| sec->sh.sh_size = size; |
| sec->sh.sh_entsize = entsize; |
| sec->sh.sh_type = SHT_PROGBITS; |
| sec->sh.sh_addralign = 1; |
| sec->sh.sh_flags = SHF_ALLOC | sh_flags; |
| |
| /* Add section name to .shstrtab (or .strtab for Clang) */ |
| shstrtab = find_section_by_name(elf, ".shstrtab"); |
| if (!shstrtab) |
| shstrtab = find_section_by_name(elf, ".strtab"); |
| if (!shstrtab) { |
| WARN("can't find .shstrtab or .strtab section"); |
| return NULL; |
| } |
| sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name); |
| if (sec->sh.sh_name == -1) |
| return NULL; |
| |
| list_add_tail(&sec->list, &elf->sections); |
| elf_hash_add(section, &sec->hash, sec->idx); |
| elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name)); |
| |
| elf->changed = true; |
| |
| return sec; |
| } |
| |
| static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base) |
| { |
| char *relocname; |
| struct section *sec; |
| |
| relocname = malloc(strlen(base->name) + strlen(".rel") + 1); |
| if (!relocname) { |
| perror("malloc"); |
| return NULL; |
| } |
| strcpy(relocname, ".rel"); |
| strcat(relocname, base->name); |
| |
| sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rel), 0); |
| free(relocname); |
| if (!sec) |
| return NULL; |
| |
| base->reloc = sec; |
| sec->base = base; |
| |
| sec->sh.sh_type = SHT_REL; |
| sec->sh.sh_addralign = 8; |
| sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx; |
| sec->sh.sh_info = base->idx; |
| sec->sh.sh_flags = SHF_INFO_LINK; |
| |
| return sec; |
| } |
| |
| static struct section *elf_create_rela_reloc_section(struct elf *elf, struct section *base) |
| { |
| char *relocname; |
| struct section *sec; |
| |
| relocname = malloc(strlen(base->name) + strlen(".rela") + 1); |
| if (!relocname) { |
| perror("malloc"); |
| return NULL; |
| } |
| strcpy(relocname, ".rela"); |
| strcat(relocname, base->name); |
| |
| sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0); |
| free(relocname); |
| if (!sec) |
| return NULL; |
| |
| base->reloc = sec; |
| sec->base = base; |
| |
| sec->sh.sh_type = SHT_RELA; |
| sec->sh.sh_addralign = 8; |
| sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx; |
| sec->sh.sh_info = base->idx; |
| sec->sh.sh_flags = SHF_INFO_LINK; |
| |
| return sec; |
| } |
| |
| static struct section *elf_create_reloc_section(struct elf *elf, |
| struct section *base, |
| int reltype) |
| { |
| switch (reltype) { |
| case SHT_REL: return elf_create_rel_reloc_section(elf, base); |
| case SHT_RELA: return elf_create_rela_reloc_section(elf, base); |
| default: return NULL; |
| } |
| } |
| |
| static int elf_rebuild_rel_reloc_section(struct section *sec, int nr) |
| { |
| struct reloc *reloc; |
| int idx = 0, size; |
| void *buf; |
| |
| /* Allocate a buffer for relocations */ |
| size = nr * sizeof(GElf_Rel); |
| buf = malloc(size); |
| if (!buf) { |
| perror("malloc"); |
| return -1; |
| } |
| |
| sec->data->d_buf = buf; |
| sec->data->d_size = size; |
| sec->data->d_type = ELF_T_REL; |
| |
| sec->sh.sh_size = size; |
| |
| idx = 0; |
| list_for_each_entry(reloc, &sec->reloc_list, list) { |
| reloc->rel.r_offset = reloc->offset; |
| reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); |
| gelf_update_rel(sec->data, idx, &reloc->rel); |
| idx++; |
| } |
| |
| return 0; |
| } |
| |
| static int elf_rebuild_rela_reloc_section(struct section *sec, int nr) |
| { |
| struct reloc *reloc; |
| int idx = 0, size; |
| void *buf; |
| |
| /* Allocate a buffer for relocations with addends */ |
| size = nr * sizeof(GElf_Rela); |
| buf = malloc(size); |
| if (!buf) { |
| perror("malloc"); |
| return -1; |
| } |
| |
| sec->data->d_buf = buf; |
| sec->data->d_size = size; |
| sec->data->d_type = ELF_T_RELA; |
| |
| sec->sh.sh_size = size; |
| |
| idx = 0; |
| list_for_each_entry(reloc, &sec->reloc_list, list) { |
| reloc->rela.r_offset = reloc->offset; |
| reloc->rela.r_addend = reloc->addend; |
| reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); |
| gelf_update_rela(sec->data, idx, &reloc->rela); |
| idx++; |
| } |
| |
| return 0; |
| } |
| |
| static int elf_rebuild_reloc_section(struct elf *elf, struct section *sec) |
| { |
| struct reloc *reloc; |
| int nr; |
| |
| nr = 0; |
| list_for_each_entry(reloc, &sec->reloc_list, list) |
| nr++; |
| |
| switch (sec->sh.sh_type) { |
| case SHT_REL: return elf_rebuild_rel_reloc_section(sec, nr); |
| case SHT_RELA: return elf_rebuild_rela_reloc_section(sec, nr); |
| default: return -1; |
| } |
| } |
| |
| int elf_write_insn(struct elf *elf, struct section *sec, |
| unsigned long offset, unsigned int len, |
| const char *insn) |
| { |
| Elf_Data *data = sec->data; |
| |
| if (data->d_type != ELF_T_BYTE || data->d_off) { |
| WARN("write to unexpected data for section: %s", sec->name); |
| return -1; |
| } |
| |
| memcpy(data->d_buf + offset, insn, len); |
| elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY); |
| |
| elf->changed = true; |
| |
| return 0; |
| } |
| |
| int elf_write_reloc(struct elf *elf, struct reloc *reloc) |
| { |
| struct section *sec = reloc->sec; |
| |
| if (sec->sh.sh_type == SHT_REL) { |
| reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); |
| reloc->rel.r_offset = reloc->offset; |
| |
| if (!gelf_update_rel(sec->data, reloc->idx, &reloc->rel)) { |
| WARN_ELF("gelf_update_rel"); |
| return -1; |
| } |
| } else { |
| reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); |
| reloc->rela.r_addend = reloc->addend; |
| reloc->rela.r_offset = reloc->offset; |
| |
| if (!gelf_update_rela(sec->data, reloc->idx, &reloc->rela)) { |
| WARN_ELF("gelf_update_rela"); |
| return -1; |
| } |
| } |
| |
| elf->changed = true; |
| |
| return 0; |
| } |
| |
| int elf_write(struct elf *elf) |
| { |
| struct section *sec; |
| Elf_Scn *s; |
| |
| /* Update changed relocation sections and section headers: */ |
| list_for_each_entry(sec, &elf->sections, list) { |
| if (sec->changed) { |
| if (sec->base && |
| elf_rebuild_reloc_section(elf, sec)) { |
| WARN("elf_rebuild_reloc_section"); |
| return -1; |
| } |
| |
| s = elf_getscn(elf->elf, sec->idx); |
| if (!s) { |
| WARN_ELF("elf_getscn"); |
| return -1; |
| } |
| if (!gelf_update_shdr(s, &sec->sh)) { |
| WARN_ELF("gelf_update_shdr"); |
| return -1; |
| } |
| |
| sec->changed = false; |
| elf->changed = true; |
| } |
| } |
| |
| /* Make sure the new section header entries get updated properly. */ |
| elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY); |
| |
| /* Write all changes to the file. */ |
| if (elf_update(elf->elf, ELF_C_WRITE) < 0) { |
| WARN_ELF("elf_update"); |
| return -1; |
| } |
| |
| elf->changed = false; |
| |
| return 0; |
| } |
| |
| void elf_close(struct elf *elf) |
| { |
| struct section *sec, *tmpsec; |
| struct symbol *sym, *tmpsym; |
| struct reloc *reloc, *tmpreloc; |
| |
| if (elf->elf) |
| elf_end(elf->elf); |
| |
| if (elf->fd > 0) |
| close(elf->fd); |
| |
| list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) { |
| list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) { |
| list_del(&sym->list); |
| hash_del(&sym->hash); |
| free(sym); |
| } |
| list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) { |
| list_del(&reloc->list); |
| hash_del(&reloc->hash); |
| free(reloc); |
| } |
| list_del(&sec->list); |
| free(sec); |
| } |
| |
| free(elf); |
| } |