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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /tools/objtool/elf.c | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tools/objtool/elf.c')
-rw-r--r-- | tools/objtool/elf.c | 1325 |
1 files changed, 1325 insertions, 0 deletions
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c new file mode 100644 index 000000000..a2ea3931e --- /dev/null +++ b/tools/objtool/elf.c @@ -0,0 +1,1325 @@ +// 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 <fcntl.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <errno.h> +#include "builtin.h" + +#include "elf.h" +#include "warn.h" + +#define MAX_NAME_LEN 128 + +static inline u32 str_hash(const char *str) +{ + return jhash(str, strlen(str), 0); +} + +static inline int elf_hash_bits(void) +{ + return vmlinux ? ELF_HASH_BITS : 16; +} + +#define elf_hash_add(hashtable, node, key) \ + hlist_add_head(node, &hashtable[hash_min(key, elf_hash_bits())]) + +static void elf_hash_init(struct hlist_head *table) +{ + __hash_init(table, 1U << elf_hash_bits()); +} + +#define elf_hash_for_each_possible(name, obj, member, key) \ + hlist_for_each_entry(obj, &name[hash_min(key, elf_hash_bits())], member) + +static void rb_add(struct rb_root *tree, struct rb_node *node, + int (*cmp)(struct rb_node *, const struct rb_node *)) +{ + struct rb_node **link = &tree->rb_node; + struct rb_node *parent = NULL; + + while (*link) { + parent = *link; + if (cmp(node, parent) < 0) + link = &parent->rb_left; + else + link = &parent->rb_right; + } + + rb_link_node(node, parent, link); + rb_insert_color(node, tree); +} + +static struct rb_node *rb_find_first(const struct rb_root *tree, const void *key, + int (*cmp)(const void *key, const struct rb_node *)) +{ + struct rb_node *node = tree->rb_node; + struct rb_node *match = NULL; + + while (node) { + int c = cmp(key, node); + if (c <= 0) { + if (!c) + match = node; + node = node->rb_left; + } else if (c > 0) { + node = node->rb_right; + } + } + + return match; +} + +static struct rb_node *rb_next_match(struct rb_node *node, const void *key, + int (*cmp)(const void *key, const struct rb_node *)) +{ + node = rb_next(node); + if (node && cmp(key, node)) + node = NULL; + return node; +} + +#define rb_for_each(tree, node, key, cmp) \ + for ((node) = rb_find_first((tree), (key), (cmp)); \ + (node); (node) = rb_next_match((node), (key), (cmp))) + +static int 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 -1; + if (sa->offset > sb->offset) + return 1; + + if (sa->len < sb->len) + return -1; + if (sa->len > sb->len) + return 1; + + sa->alias = sb; + + return 0; +} + +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(elf->section_name_hash, 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(elf->section_hash, 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(elf->symbol_hash, 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(&sec->symbol_tree, node, &offset, 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(&sec->symbol_tree, node, &offset, 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(&sec->symbol_tree, node, &offset, 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(&sec->symbol_tree, node, &offset, 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(elf->symbol_name_hash, 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(elf->reloc_hash, 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; + } + + 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; + + list_add_tail(&sec->list, &elf->sections); + elf_hash_add(elf->section_hash, &sec->hash, sec->idx); + elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name)); + } + + if (stats) + printf("nr_sections: %lu\n", (unsigned long)sections_nr); + + /* 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->alias = sym; + + 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->sec->symbol_tree, &sym->node, 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(elf->symbol_hash, &sym->hash, sym->idx); + elf_hash_add(elf->symbol_name_hash, &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) { + /* + * A missing symbol table is actually possible if it's an empty + * .o file. This can happen for thunk_64.o. + */ + return 0; + } + + 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; + + 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 (stats) + printf("nr_symbols: %lu\n", (unsigned long)symbols_nr); + + /* 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(elf->reloc_hash, &reloc->hash, reloc_hash(reloc)); + + 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(elf->symbol_hash, &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; + + 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(elf->reloc_hash, &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); + } + + 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_hash_init(elf->symbol_hash); + elf_hash_init(elf->symbol_name_hash); + elf_hash_init(elf->section_hash); + elf_hash_init(elf->section_name_hash); + elf_hash_init(elf->reloc_hash); + + 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; + data->d_type = ELF_T_SYM; + + len = strtab->len; + strtab->len += 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->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(elf->section_hash, &sec->hash, sec->idx); + elf_hash_add(elf->section_name_hash, &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; + GElf_Rel *relocs; + + /* Allocate a buffer for relocations */ + size = nr * sizeof(*relocs); + relocs = malloc(size); + if (!relocs) { + perror("malloc"); + return -1; + } + + sec->data->d_buf = relocs; + sec->data->d_size = size; + + sec->sh.sh_size = size; + + idx = 0; + list_for_each_entry(reloc, &sec->reloc_list, list) { + relocs[idx].r_offset = reloc->offset; + relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); + idx++; + } + + return 0; +} + +static int elf_rebuild_rela_reloc_section(struct section *sec, int nr) +{ + struct reloc *reloc; + int idx = 0, size; + GElf_Rela *relocs; + + /* Allocate a buffer for relocations with addends */ + size = nr * sizeof(*relocs); + relocs = malloc(size); + if (!relocs) { + perror("malloc"); + return -1; + } + + sec->data->d_buf = relocs; + sec->data->d_size = size; + + sec->sh.sh_size = size; + + idx = 0; + list_for_each_entry(reloc, &sec->reloc_list, list) { + relocs[idx].r_offset = reloc->offset; + relocs[idx].r_addend = reloc->addend; + relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); + 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); +} |