| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Peter Zijlstra | 2916 | 44.85% | 25 | 40.32% |
| Josh Poimboeuf | 2492 | 38.33% | 15 | 24.19% |
| Matt Helsley | 694 | 10.68% | 2 | 3.23% |
| Sami Tolvanen | 110 | 1.69% | 3 | 4.84% |
| Michael Forney | 88 | 1.35% | 2 | 3.23% |
| Martin Schwidefsky | 65 | 1.00% | 1 | 1.61% |
| Artem Savkov | 63 | 0.97% | 2 | 3.23% |
| Kristen Carlson Accardi | 18 | 0.28% | 1 | 1.61% |
| Simon Ser | 16 | 0.25% | 1 | 1.61% |
| Petr Vandrovec | 12 | 0.18% | 1 | 1.61% |
| Joe Lawrence | 9 | 0.14% | 1 | 1.61% |
| Ingo Molnar | 6 | 0.09% | 2 | 3.23% |
| Martin Kepplinger | 4 | 0.06% | 1 | 1.61% |
| Vasily Gorbik | 3 | 0.05% | 1 | 1.61% |
| Thomas Gleixner | 2 | 0.03% | 1 | 1.61% |
| Miroslav Benes | 1 | 0.02% | 1 | 1.61% |
| Julien Thierry | 1 | 0.02% | 1 | 1.61% |
| Mikulas Patocka | 1 | 0.02% | 1 | 1.61% |
| Total | 6501 | 62 |
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// 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 symbol_hole { unsigned long key; const struct symbol *sym; }; /* * Find !section symbol where @offset is after it. */ static int symbol_hole_by_offset(const void *key, const struct rb_node *node) { const struct symbol *s = rb_entry(node, struct symbol, node); struct symbol_hole *sh = (void *)key; if (sh->key < s->offset) return -1; if (sh->key >= s->offset + s->len) { if (s->type != STT_SECTION) sh->sym = s; 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; } /* * Returns size of hole starting at @offset. */ int find_symbol_hole_containing(const struct section *sec, unsigned long offset) { struct symbol_hole hole = { .key = offset, .sym = NULL, }; struct rb_node *n; struct symbol *s; /* * Find the rightmost symbol for which @offset is after it. */ n = rb_find(&hole, &sec->symbol_tree, symbol_hole_by_offset); /* found a symbol that contains @offset */ if (n) return 0; /* not a hole */ /* didn't find a symbol for which @offset is after it */ if (!hole.sym) return 0; /* not a hole */ /* @offset >= sym->offset + sym->len, find symbol after it */ n = rb_next(&hole.sym->node); if (!n) return -1; /* until end of address space */ /* hole until start of next symbol */ s = rb_entry(n, struct symbol, node); return s->offset - offset; } 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; } } if (sec->sh.sh_flags & SHF_EXECINSTR) elf->text_size += sec->sh.sh_size; 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 (opts.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; INIT_LIST_HEAD(&sym->pv_target); sym->alias = sym; sym->type = GELF_ST_TYPE(sym->sym.st_info); sym->bind = GELF_ST_BIND(sym->sym.st_info); if (sym->type == STT_FILE) elf->num_files++; 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->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 (opts.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, s64 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->sh.sh_size += sec->reloc->sh.sh_entsize; sec->reloc->changed = true; return 0; } /* * Ensure that any reloc section containing references to @sym is marked * changed such that it will get re-generated in elf_rebuild_reloc_sections() * with the new symbol index. */ static void elf_dirty_reloc_sym(struct elf *elf, struct symbol *sym) { struct section *sec; list_for_each_entry(sec, &elf->sections, list) { struct reloc *reloc; if (sec->changed) continue; list_for_each_entry(reloc, &sec->reloc_list, list) { if (reloc->sym == sym) { sec->changed = true; break; } } } } /* * The libelf API is terrible; gelf_update_sym*() takes a data block relative * index value, *NOT* the symbol index. As such, iterate the data blocks and * adjust index until it fits. * * If no data block is found, allow adding a new data block provided the index * is only one past the end. */ static int elf_update_symbol(struct elf *elf, struct section *symtab, struct section *symtab_shndx, struct symbol *sym) { Elf32_Word shndx = sym->sec ? sym->sec->idx : SHN_UNDEF; Elf_Data *symtab_data = NULL, *shndx_data = NULL; Elf64_Xword entsize = symtab->sh.sh_entsize; int max_idx, idx = sym->idx; Elf_Scn *s, *t = NULL; bool is_special_shndx = sym->sym.st_shndx >= SHN_LORESERVE && sym->sym.st_shndx != SHN_XINDEX; if (is_special_shndx) shndx = sym->sym.st_shndx; s = elf_getscn(elf->elf, symtab->idx); if (!s) { WARN_ELF("elf_getscn"); return -1; } if (symtab_shndx) { t = elf_getscn(elf->elf, symtab_shndx->idx); if (!t) { WARN_ELF("elf_getscn"); return -1; } } for (;;) { /* get next data descriptor for the relevant sections */ symtab_data = elf_getdata(s, symtab_data); if (t) shndx_data = elf_getdata(t, shndx_data); /* end-of-list */ if (!symtab_data) { void *buf; if (idx) { /* we don't do holes in symbol tables */ WARN("index out of range"); return -1; } /* if @idx == 0, it's the next contiguous entry, create it */ symtab_data = elf_newdata(s); if (t) shndx_data = elf_newdata(t); buf = calloc(1, entsize); if (!buf) { WARN("malloc"); return -1; } symtab_data->d_buf = buf; symtab_data->d_size = entsize; symtab_data->d_align = 1; symtab_data->d_type = ELF_T_SYM; symtab->sh.sh_size += entsize; symtab->changed = true; if (t) { shndx_data->d_buf = &sym->sec->idx; shndx_data->d_size = sizeof(Elf32_Word); shndx_data->d_align = sizeof(Elf32_Word); shndx_data->d_type = ELF_T_WORD; symtab_shndx->sh.sh_size += sizeof(Elf32_Word); symtab_shndx->changed = true; } break; } /* empty blocks should not happen */ if (!symtab_data->d_size) { WARN("zero size data"); return -1; } /* is this the right block? */ max_idx = symtab_data->d_size / entsize; if (idx < max_idx) break; /* adjust index and try again */ idx -= max_idx; } /* something went side-ways */ if (idx < 0) { WARN("negative index"); return -1; } /* setup extended section index magic and write the symbol */ if ((shndx >= SHN_UNDEF && shndx < SHN_LORESERVE) || is_special_shndx) { sym->sym.st_shndx = shndx; if (!shndx_data) shndx = 0; } else { sym->sym.st_shndx = SHN_XINDEX; if (!shndx_data) { WARN("no .symtab_shndx"); return -1; } } if (!gelf_update_symshndx(symtab_data, shndx_data, idx, &sym->sym, shndx)) { WARN_ELF("gelf_update_symshndx"); return -1; } return 0; } static struct symbol * elf_create_section_symbol(struct elf *elf, struct section *sec) { struct section *symtab, *symtab_shndx; Elf32_Word first_non_local, new_idx; struct symbol *sym, *old; symtab = find_section_by_name(elf, ".symtab"); if (symtab) { symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); } else { WARN("no .symtab"); return NULL; } sym = calloc(1, sizeof(*sym)); if (!sym) { perror("malloc"); return NULL; } sym->name = sec->name; sym->sec = sec; // st_name 0 sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION); // st_other 0 // st_value 0 // st_size 0 /* * Move the first global symbol, as per sh_info, into a new, higher * symbol index. This fees up a spot for a new local symbol. */ first_non_local = symtab->sh.sh_info; new_idx = symtab->sh.sh_size / symtab->sh.sh_entsize; old = find_symbol_by_index(elf, first_non_local); if (old) { old->idx = new_idx; hlist_del(&old->hash); elf_hash_add(symbol, &old->hash, old->idx); elf_dirty_reloc_sym(elf, old); if (elf_update_symbol(elf, symtab, symtab_shndx, old)) { WARN("elf_update_symbol move"); return NULL; } new_idx = first_non_local; } sym->idx = new_idx; if (elf_update_symbol(elf, symtab, symtab_shndx, sym)) { WARN("elf_update_symbol"); return NULL; } /* * Either way, we added a LOCAL symbol. */ symtab->sh.sh_info += 1; elf_add_symbol(elf, sym); return sym; } 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 = insn_sec->sym; int addend = insn_off; if (!sym) { /* * Due to how weak functions work, we must use section based * relocations. Symbol based relocations would result in the * weak and non-weak function annotations being overlaid on the * non-weak function after linking. */ sym = elf_create_section_symbol(elf, insn_sec); if (!sym) return -1; insn_sec->sym = sym; } 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 (opts.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->sh.sh_size; strtab->sh.sh_size += data->d_size; strtab->changed = true; return len; } 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->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) { struct reloc *reloc; int idx = 0; void *buf; /* Allocate a buffer for relocations */ buf = malloc(sec->sh.sh_size); if (!buf) { perror("malloc"); return -1; } sec->data->d_buf = buf; sec->data->d_size = sec->sh.sh_size; sec->data->d_type = ELF_T_REL; 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); if (!gelf_update_rel(sec->data, idx, &reloc->rel)) { WARN_ELF("gelf_update_rel"); return -1; } idx++; } return 0; } static int elf_rebuild_rela_reloc_section(struct section *sec) { struct reloc *reloc; int idx = 0; void *buf; /* Allocate a buffer for relocations with addends */ buf = malloc(sec->sh.sh_size); if (!buf) { perror("malloc"); return -1; } sec->data->d_buf = buf; sec->data->d_size = sec->sh.sh_size; sec->data->d_type = ELF_T_RELA; 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); if (!gelf_update_rela(sec->data, idx, &reloc->rela)) { WARN_ELF("gelf_update_rela"); return -1; } idx++; } return 0; } static int elf_rebuild_reloc_section(struct elf *elf, struct section *sec) { switch (sec->sh.sh_type) { case SHT_REL: return elf_rebuild_rel_reloc_section(sec); case SHT_RELA: return elf_rebuild_rela_reloc_section(sec); 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; if (opts.dryrun) return 0; /* Update changed relocation sections and section headers: */ list_for_each_entry(sec, &elf->sections, list) { if (sec->changed) { 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; } if (sec->base && elf_rebuild_reloc_section(elf, sec)) { WARN("elf_rebuild_reloc_section"); 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); }
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