![Peter Zijlstra](/assets/img/avatar_default.png)
For consistency; we have: find_symbol_by_offset() / find_symbol_containing() find_func_by_offset() / find_containing_func() fix that. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/20200324160924.558470724@infradead.org
798 lines
16 KiB
C
798 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* elf.c - ELF access library
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*
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* Adapted from kpatch (https://github.com/dynup/kpatch):
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* Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
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* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#include "builtin.h"
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#include "elf.h"
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#include "warn.h"
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#define MAX_NAME_LEN 128
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static inline u32 str_hash(const char *str)
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{
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return jhash(str, strlen(str), 0);
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}
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static void rb_add(struct rb_root *tree, struct rb_node *node,
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int (*cmp)(struct rb_node *, const struct rb_node *))
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{
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struct rb_node **link = &tree->rb_node;
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struct rb_node *parent = NULL;
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while (*link) {
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parent = *link;
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if (cmp(node, parent) < 0)
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link = &parent->rb_left;
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else
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link = &parent->rb_right;
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}
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rb_link_node(node, parent, link);
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rb_insert_color(node, tree);
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}
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static struct rb_node *rb_find_first(struct rb_root *tree, const void *key,
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int (*cmp)(const void *key, const struct rb_node *))
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{
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struct rb_node *node = tree->rb_node;
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struct rb_node *match = NULL;
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while (node) {
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int c = cmp(key, node);
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if (c <= 0) {
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if (!c)
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match = node;
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node = node->rb_left;
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} else if (c > 0) {
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node = node->rb_right;
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}
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}
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return match;
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}
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static struct rb_node *rb_next_match(struct rb_node *node, const void *key,
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int (*cmp)(const void *key, const struct rb_node *))
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{
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node = rb_next(node);
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if (node && cmp(key, node))
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node = NULL;
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return node;
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}
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#define rb_for_each(tree, node, key, cmp) \
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for ((node) = rb_find_first((tree), (key), (cmp)); \
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(node); (node) = rb_next_match((node), (key), (cmp)))
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static int symbol_to_offset(struct rb_node *a, const struct rb_node *b)
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{
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struct symbol *sa = rb_entry(a, struct symbol, node);
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struct symbol *sb = rb_entry(b, struct symbol, node);
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if (sa->offset < sb->offset)
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return -1;
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if (sa->offset > sb->offset)
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return 1;
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if (sa->len < sb->len)
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return -1;
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if (sa->len > sb->len)
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return 1;
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sa->alias = sb;
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return 0;
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}
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static int symbol_by_offset(const void *key, const struct rb_node *node)
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{
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const struct symbol *s = rb_entry(node, struct symbol, node);
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const unsigned long *o = key;
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if (*o < s->offset)
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return -1;
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if (*o > s->offset + s->len)
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return 1;
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return 0;
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}
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struct section *find_section_by_name(struct elf *elf, const char *name)
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{
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struct section *sec;
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hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))
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if (!strcmp(sec->name, name))
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return sec;
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return NULL;
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}
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static struct section *find_section_by_index(struct elf *elf,
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unsigned int idx)
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{
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struct section *sec;
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hash_for_each_possible(elf->section_hash, sec, hash, idx)
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if (sec->idx == idx)
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return sec;
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return NULL;
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}
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static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
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{
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struct symbol *sym;
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hash_for_each_possible(elf->symbol_hash, sym, hash, idx)
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if (sym->idx == idx)
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return sym;
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return NULL;
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}
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struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
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{
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struct rb_node *node;
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rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
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struct symbol *s = rb_entry(node, struct symbol, node);
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if (s->offset == offset && s->type != STT_SECTION)
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return s;
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}
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return NULL;
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}
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struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)
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{
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struct rb_node *node;
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rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
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struct symbol *s = rb_entry(node, struct symbol, node);
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if (s->offset == offset && s->type == STT_FUNC)
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return s;
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}
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return NULL;
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}
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struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
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{
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struct rb_node *node;
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rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
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struct symbol *s = rb_entry(node, struct symbol, node);
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if (s->type != STT_SECTION)
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return s;
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}
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return NULL;
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}
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struct symbol *find_func_containing(struct section *sec, unsigned long offset)
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{
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struct rb_node *node;
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rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
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struct symbol *s = rb_entry(node, struct symbol, node);
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if (s->type == STT_FUNC)
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return s;
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}
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return NULL;
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}
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struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
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{
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struct section *sec;
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struct symbol *sym;
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list_for_each_entry(sec, &elf->sections, list)
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list_for_each_entry(sym, &sec->symbol_list, list)
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if (!strcmp(sym->name, name))
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return sym;
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return NULL;
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}
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struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
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unsigned int len)
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{
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struct rela *rela;
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unsigned long o;
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if (!sec->rela)
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return NULL;
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for (o = offset; o < offset + len; o++)
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hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
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if (rela->offset == o)
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return rela;
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return NULL;
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}
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struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)
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{
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return find_rela_by_dest_range(sec, offset, 1);
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}
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static int read_sections(struct elf *elf)
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{
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Elf_Scn *s = NULL;
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struct section *sec;
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size_t shstrndx, sections_nr;
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int i;
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if (elf_getshdrnum(elf->elf, §ions_nr)) {
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WARN_ELF("elf_getshdrnum");
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return -1;
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}
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if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
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WARN_ELF("elf_getshdrstrndx");
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return -1;
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}
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for (i = 0; i < sections_nr; i++) {
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sec = malloc(sizeof(*sec));
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if (!sec) {
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perror("malloc");
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return -1;
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}
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memset(sec, 0, sizeof(*sec));
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INIT_LIST_HEAD(&sec->symbol_list);
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INIT_LIST_HEAD(&sec->rela_list);
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hash_init(sec->rela_hash);
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s = elf_getscn(elf->elf, i);
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if (!s) {
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WARN_ELF("elf_getscn");
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return -1;
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}
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sec->idx = elf_ndxscn(s);
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if (!gelf_getshdr(s, &sec->sh)) {
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WARN_ELF("gelf_getshdr");
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return -1;
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}
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sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
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if (!sec->name) {
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WARN_ELF("elf_strptr");
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return -1;
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}
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if (sec->sh.sh_size != 0) {
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sec->data = elf_getdata(s, NULL);
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if (!sec->data) {
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WARN_ELF("elf_getdata");
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return -1;
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}
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if (sec->data->d_off != 0 ||
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sec->data->d_size != sec->sh.sh_size) {
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WARN("unexpected data attributes for %s",
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sec->name);
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return -1;
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}
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}
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sec->len = sec->sh.sh_size;
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list_add_tail(&sec->list, &elf->sections);
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hash_add(elf->section_hash, &sec->hash, sec->idx);
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hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
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}
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if (stats)
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printf("nr_sections: %lu\n", (unsigned long)sections_nr);
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/* sanity check, one more call to elf_nextscn() should return NULL */
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if (elf_nextscn(elf->elf, s)) {
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WARN("section entry mismatch");
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return -1;
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}
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return 0;
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}
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static int read_symbols(struct elf *elf)
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{
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struct section *symtab, *sec;
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struct symbol *sym, *pfunc;
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struct list_head *entry;
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struct rb_node *pnode;
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int symbols_nr, i;
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char *coldstr;
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symtab = find_section_by_name(elf, ".symtab");
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if (!symtab) {
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WARN("missing symbol table");
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return -1;
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}
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symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
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for (i = 0; i < symbols_nr; i++) {
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sym = malloc(sizeof(*sym));
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if (!sym) {
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perror("malloc");
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return -1;
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}
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memset(sym, 0, sizeof(*sym));
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sym->alias = sym;
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sym->idx = i;
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if (!gelf_getsym(symtab->data, i, &sym->sym)) {
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WARN_ELF("gelf_getsym");
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goto err;
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}
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sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
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sym->sym.st_name);
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if (!sym->name) {
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WARN_ELF("elf_strptr");
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goto err;
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}
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sym->type = GELF_ST_TYPE(sym->sym.st_info);
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sym->bind = GELF_ST_BIND(sym->sym.st_info);
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if (sym->sym.st_shndx > SHN_UNDEF &&
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sym->sym.st_shndx < SHN_LORESERVE) {
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sym->sec = find_section_by_index(elf,
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sym->sym.st_shndx);
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if (!sym->sec) {
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WARN("couldn't find section for symbol %s",
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sym->name);
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goto err;
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}
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if (sym->type == STT_SECTION) {
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sym->name = sym->sec->name;
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sym->sec->sym = sym;
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}
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} else
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sym->sec = find_section_by_index(elf, 0);
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sym->offset = sym->sym.st_value;
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sym->len = sym->sym.st_size;
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rb_add(&sym->sec->symbol_tree, &sym->node, symbol_to_offset);
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pnode = rb_prev(&sym->node);
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if (pnode)
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entry = &rb_entry(pnode, struct symbol, node)->list;
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else
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entry = &sym->sec->symbol_list;
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list_add(&sym->list, entry);
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hash_add(elf->symbol_hash, &sym->hash, sym->idx);
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}
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if (stats)
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printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
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/* Create parent/child links for any cold subfunctions */
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list_for_each_entry(sec, &elf->sections, list) {
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list_for_each_entry(sym, &sec->symbol_list, list) {
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char pname[MAX_NAME_LEN + 1];
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size_t pnamelen;
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if (sym->type != STT_FUNC)
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continue;
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sym->pfunc = sym->cfunc = sym;
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coldstr = strstr(sym->name, ".cold");
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if (!coldstr)
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continue;
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pnamelen = coldstr - sym->name;
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if (pnamelen > MAX_NAME_LEN) {
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WARN("%s(): parent function name exceeds maximum length of %d characters",
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sym->name, MAX_NAME_LEN);
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return -1;
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}
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strncpy(pname, sym->name, pnamelen);
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pname[pnamelen] = '\0';
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pfunc = find_symbol_by_name(elf, pname);
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if (!pfunc) {
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WARN("%s(): can't find parent function",
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sym->name);
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return -1;
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}
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sym->pfunc = pfunc;
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pfunc->cfunc = sym;
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/*
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* Unfortunately, -fnoreorder-functions puts the child
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* inside the parent. Remove the overlap so we can
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* have sane assumptions.
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*
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* Note that pfunc->len now no longer matches
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* pfunc->sym.st_size.
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*/
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if (sym->sec == pfunc->sec &&
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sym->offset >= pfunc->offset &&
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sym->offset + sym->len == pfunc->offset + pfunc->len) {
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pfunc->len -= sym->len;
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}
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}
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}
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return 0;
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err:
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free(sym);
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return -1;
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}
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static int read_relas(struct elf *elf)
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{
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struct section *sec;
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struct rela *rela;
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int i;
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unsigned int symndx;
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unsigned long nr_rela, max_rela = 0, tot_rela = 0;
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list_for_each_entry(sec, &elf->sections, list) {
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if (sec->sh.sh_type != SHT_RELA)
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continue;
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sec->base = find_section_by_name(elf, sec->name + 5);
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if (!sec->base) {
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WARN("can't find base section for rela section %s",
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sec->name);
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return -1;
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}
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sec->base->rela = sec;
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nr_rela = 0;
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for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
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rela = malloc(sizeof(*rela));
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if (!rela) {
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perror("malloc");
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return -1;
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}
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memset(rela, 0, sizeof(*rela));
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if (!gelf_getrela(sec->data, i, &rela->rela)) {
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WARN_ELF("gelf_getrela");
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return -1;
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}
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rela->type = GELF_R_TYPE(rela->rela.r_info);
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rela->addend = rela->rela.r_addend;
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rela->offset = rela->rela.r_offset;
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symndx = GELF_R_SYM(rela->rela.r_info);
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rela->sym = find_symbol_by_index(elf, symndx);
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rela->sec = sec;
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if (!rela->sym) {
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WARN("can't find rela entry symbol %d for %s",
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symndx, sec->name);
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return -1;
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}
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list_add_tail(&rela->list, &sec->rela_list);
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hash_add(sec->rela_hash, &rela->hash, rela->offset);
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nr_rela++;
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}
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max_rela = max(max_rela, nr_rela);
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tot_rela += nr_rela;
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}
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if (stats) {
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printf("max_rela: %lu\n", max_rela);
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printf("tot_rela: %lu\n", tot_rela);
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}
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return 0;
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}
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struct elf *elf_read(const char *name, int flags)
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{
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struct elf *elf;
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Elf_Cmd cmd;
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elf_version(EV_CURRENT);
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elf = malloc(sizeof(*elf));
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if (!elf) {
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perror("malloc");
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return NULL;
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}
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memset(elf, 0, sizeof(*elf));
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hash_init(elf->symbol_hash);
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hash_init(elf->section_hash);
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hash_init(elf->section_name_hash);
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INIT_LIST_HEAD(&elf->sections);
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elf->fd = open(name, flags);
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if (elf->fd == -1) {
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fprintf(stderr, "objtool: Can't open '%s': %s\n",
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name, strerror(errno));
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goto err;
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}
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if ((flags & O_ACCMODE) == O_RDONLY)
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cmd = ELF_C_READ_MMAP;
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else if ((flags & O_ACCMODE) == O_RDWR)
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cmd = ELF_C_RDWR;
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else /* O_WRONLY */
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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_relas(elf))
|
|
goto err;
|
|
|
|
return elf;
|
|
|
|
err:
|
|
elf_close(elf);
|
|
return NULL;
|
|
}
|
|
|
|
struct section *elf_create_section(struct elf *elf, const char *name,
|
|
size_t entsize, int nr)
|
|
{
|
|
struct section *sec, *shstrtab;
|
|
size_t size = entsize * nr;
|
|
Elf_Scn *s;
|
|
Elf_Data *data;
|
|
|
|
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->rela_list);
|
|
hash_init(sec->rela_hash);
|
|
|
|
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;
|
|
|
|
|
|
/* 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;
|
|
}
|
|
|
|
s = elf_getscn(elf->elf, shstrtab->idx);
|
|
if (!s) {
|
|
WARN_ELF("elf_getscn");
|
|
return NULL;
|
|
}
|
|
|
|
data = elf_newdata(s);
|
|
if (!data) {
|
|
WARN_ELF("elf_newdata");
|
|
return NULL;
|
|
}
|
|
|
|
data->d_buf = sec->name;
|
|
data->d_size = strlen(name) + 1;
|
|
data->d_align = 1;
|
|
|
|
sec->sh.sh_name = shstrtab->len;
|
|
|
|
shstrtab->len += strlen(name) + 1;
|
|
shstrtab->changed = true;
|
|
|
|
list_add_tail(&sec->list, &elf->sections);
|
|
hash_add(elf->section_hash, &sec->hash, sec->idx);
|
|
hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
|
|
|
|
return sec;
|
|
}
|
|
|
|
struct section *elf_create_rela_section(struct elf *elf, struct section *base)
|
|
{
|
|
char *relaname;
|
|
struct section *sec;
|
|
|
|
relaname = malloc(strlen(base->name) + strlen(".rela") + 1);
|
|
if (!relaname) {
|
|
perror("malloc");
|
|
return NULL;
|
|
}
|
|
strcpy(relaname, ".rela");
|
|
strcat(relaname, base->name);
|
|
|
|
sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0);
|
|
free(relaname);
|
|
if (!sec)
|
|
return NULL;
|
|
|
|
base->rela = 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;
|
|
}
|
|
|
|
int elf_rebuild_rela_section(struct section *sec)
|
|
{
|
|
struct rela *rela;
|
|
int nr, idx = 0, size;
|
|
GElf_Rela *relas;
|
|
|
|
nr = 0;
|
|
list_for_each_entry(rela, &sec->rela_list, list)
|
|
nr++;
|
|
|
|
size = nr * sizeof(*relas);
|
|
relas = malloc(size);
|
|
if (!relas) {
|
|
perror("malloc");
|
|
return -1;
|
|
}
|
|
|
|
sec->data->d_buf = relas;
|
|
sec->data->d_size = size;
|
|
|
|
sec->sh.sh_size = size;
|
|
|
|
idx = 0;
|
|
list_for_each_entry(rela, &sec->rela_list, list) {
|
|
relas[idx].r_offset = rela->offset;
|
|
relas[idx].r_addend = rela->addend;
|
|
relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type);
|
|
idx++;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int elf_write(struct elf *elf)
|
|
{
|
|
struct section *sec;
|
|
Elf_Scn *s;
|
|
|
|
/* Update section headers for changed sections: */
|
|
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;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* 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;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
void elf_close(struct elf *elf)
|
|
{
|
|
struct section *sec, *tmpsec;
|
|
struct symbol *sym, *tmpsym;
|
|
struct rela *rela, *tmprela;
|
|
|
|
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(rela, tmprela, &sec->rela_list, list) {
|
|
list_del(&rela->list);
|
|
hash_del(&rela->hash);
|
|
free(rela);
|
|
}
|
|
list_del(&sec->list);
|
|
free(sec);
|
|
}
|
|
|
|
free(elf);
|
|
}
|