/* * 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> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, see <http://www.gnu.org/licenses/>. */ #include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h> #include "elf.h"#include "warn.h" /* * Fallback for systems without this "read, mmaping if possible" cmd. */#ifndef ELF_C_READ_MMAP#define ELF_C_READ_MMAP ELF_C_READ#endif #define WARN_ELF(format, ...)					\	WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1)) struct section *find_section_by_name(struct elf *elf, const char *name){	struct section *sec; 	list_for_each_entry(sec, &elf->sections, list)		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; 	list_for_each_entry(sec, &elf->sections, list)		if (sec->idx == idx)			return sec; 	return NULL;} static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx){	struct section *sec;	struct symbol *sym; 	list_for_each_entry(sec, &elf->sections, list)		hash_for_each_possible(sec->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 symbol *sym; 	list_for_each_entry(sym, &sec->symbol_list, list)		if (sym->type != STT_SECTION &&		    sym->offset == offset)			return sym; 	return NULL;} struct symbol *find_symbol_containing(struct section *sec, unsigned long offset){	struct symbol *sym; 	list_for_each_entry(sym, &sec->symbol_list, list)		if (sym->type != STT_SECTION &&		    offset >= sym->offset && offset < sym->offset + sym->len)			return sym; 	return NULL;} struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,				     unsigned int len){	struct rela *rela;	unsigned long o; 	if (!sec->rela)		return NULL; 	for (o = offset; o < offset + len; o++)		hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)			if (rela->offset == o)				return rela; 	return NULL;} struct rela *find_rela_by_dest(struct section *sec, unsigned long offset){	return find_rela_by_dest_range(sec, offset, 1);} struct symbol *find_containing_func(struct section *sec, unsigned long offset){	struct symbol *func; 	list_for_each_entry(func, &sec->symbol_list, list)		if (func->type == STT_FUNC && offset >= func->offset &&		    offset < func->offset + func->len)			return func; 	return NULL;} 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, &sections_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->rela_list);		hash_init(sec->rela_hash);		hash_init(sec->symbol_hash); 		list_add_tail(&sec->list, &elf->sections); 		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;		} 		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->data->d_size;	} 	/* 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 int read_symbols(struct elf *elf){	struct section *symtab;	struct symbol *sym;	struct list_head *entry, *tmp;	int symbols_nr, i; 	symtab = find_section_by_name(elf, ".symtab");	if (!symtab) {		WARN("missing symbol table");		return -1;	} 	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_getsym(symtab->data, i, &sym->sym)) {			WARN_ELF("gelf_getsym");			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;		} 		sym->type = GELF_ST_TYPE(sym->sym.st_info);		sym->bind = GELF_ST_BIND(sym->sym.st_info); 		if (sym->sym.st_shndx > SHN_UNDEF &&		    sym->sym.st_shndx < SHN_LORESERVE) {			sym->sec = find_section_by_index(elf,							 sym->sym.st_shndx);			if (!sym->sec) {				WARN("couldn't find section for symbol %s",				     sym->name);				goto err;			}			if (sym->type == STT_SECTION) {				sym->name = sym->sec->name;				sym->sec->sym = sym;			}		} else			sym->sec = find_section_by_index(elf, 0); 		sym->offset = sym->sym.st_value;		sym->len = sym->sym.st_size; 		/* sorted insert into a per-section list */		entry = &sym->sec->symbol_list;		list_for_each_prev(tmp, &sym->sec->symbol_list) {			struct symbol *s; 			s = list_entry(tmp, struct symbol, list); 			if (sym->offset > s->offset) {				entry = tmp;				break;			} 			if (sym->offset == s->offset && sym->len >= s->len) {				entry = tmp;				break;			}		}		list_add(&sym->list, entry);		hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);	} 	return 0; err:	free(sym);	return -1;} static int read_relas(struct elf *elf){	struct section *sec;	struct rela *rela;	int i;	unsigned int symndx; 	list_for_each_entry(sec, &elf->sections, list) {		if (sec->sh.sh_type != SHT_RELA)			continue; 		sec->base = find_section_by_name(elf, sec->name + 5);		if (!sec->base) {			WARN("can't find base section for rela section %s",			     sec->name);			return -1;		} 		sec->base->rela = sec; 		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {			rela = malloc(sizeof(*rela));			if (!rela) {				perror("malloc");				return -1;			}			memset(rela, 0, sizeof(*rela)); 			if (!gelf_getrela(sec->data, i, &rela->rela)) {				WARN_ELF("gelf_getrela");				return -1;			} 			rela->type = GELF_R_TYPE(rela->rela.r_info);			rela->addend = rela->rela.r_addend;			rela->offset = rela->rela.r_offset;			symndx = GELF_R_SYM(rela->rela.r_info);			rela->sym = find_symbol_by_index(elf, symndx);			if (!rela->sym) {				WARN("can't find rela entry symbol %d for %s",				     symndx, sec->name);				return -1;			} 			list_add_tail(&rela->list, &sec->rela_list);			hash_add(sec->rela_hash, &rela->hash, rela->offset); 		}	} 	return 0;} struct elf *elf_open(const char *name){	struct elf *elf; 	elf_version(EV_CURRENT); 	elf = malloc(sizeof(*elf));	if (!elf) {		perror("malloc");		return NULL;	}	memset(elf, 0, sizeof(*elf)); 	INIT_LIST_HEAD(&elf->sections); 	elf->fd = open(name, O_RDONLY);	if (elf->fd == -1) {		perror("open");		goto err;	} 	elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, 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;} 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);}