335 lines
8.7 KiB
C
335 lines
8.7 KiB
C
/* $NetBSD: exec_elf32.c,v 1.15 2022/07/08 17:47:47 andvar Exp $ */
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/*
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* Copyright (c) 1997, 1998 Christopher G. Demetriou
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed for the
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* NetBSD Project. See http://www.NetBSD.org/ for
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* information about NetBSD.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
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*/
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#include <sys/cdefs.h>
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#ifndef lint
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__RCSID("$NetBSD: exec_elf32.c,v 1.15 2022/07/08 17:47:47 andvar Exp $");
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#endif
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#ifndef ELFSIZE
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#define ELFSIZE 32
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#endif
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <errno.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 "extern.h"
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#if (defined(NLIST_ELF32) && (ELFSIZE == 32)) || \
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(defined(NLIST_ELF64) && (ELFSIZE == 64))
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#include <sys/exec_elf.h>
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struct listelem {
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struct listelem *next;
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void *mem;
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off_t file;
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size_t size;
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};
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static ssize_t
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xreadatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
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{
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ssize_t rv;
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if (lseek(fd, off, SEEK_SET) != off) {
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perror(fn);
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return -1;
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}
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if ((size_t)(rv = read(fd, buf, size)) != size) {
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fprintf(stderr, "%s: read error: %s\n", fn,
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rv == -1 ? strerror(errno) : "short read");
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return -1;
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}
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return size;
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}
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static ssize_t
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xwriteatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
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{
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ssize_t rv;
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if (lseek(fd, off, SEEK_SET) != off) {
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perror(fn);
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return -1;
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}
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if ((size_t)(rv = write(fd, buf, size)) != size) {
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fprintf(stderr, "%s: write error: %s\n", fn,
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rv == -1 ? strerror(errno) : "short write");
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return -1;
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}
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return size;
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}
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static void *
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xmalloc(size_t size, const char *fn, const char *use)
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{
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void *rv;
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rv = malloc(size);
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if (rv == NULL)
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fprintf(stderr, "%s: out of memory (allocating for %s)\n",
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fn, use);
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return (rv);
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}
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static void *
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xrealloc(void *ptr, size_t size, const char *fn, const char *use)
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{
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void *rv;
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rv = realloc(ptr, size);
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if (rv == NULL) {
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free(ptr);
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fprintf(stderr, "%s: out of memory (reallocating for %s)\n",
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fn, use);
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}
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return (rv);
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}
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int
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ELFNAMEEND(check)(int fd, const char *fn)
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{
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Elf_Ehdr eh;
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struct stat sb;
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/*
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* Check the header to make sure it's an ELF file (of the
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* appropriate size).
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*/
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if (fstat(fd, &sb) == -1)
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return 0;
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if (sb.st_size < (off_t)(sizeof eh))
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return 0;
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if (read(fd, &eh, sizeof eh) != sizeof eh)
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return 0;
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if (memcmp(eh.e_ident, ELFMAG, SELFMAG) != 0 ||
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eh.e_ident[EI_CLASS] != ELFCLASS)
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return 0;
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switch (eh.e_machine) {
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ELFDEFNNAME(MACHDEP_ID_CASES)
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default:
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return 0;
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}
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return 1;
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}
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/*
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* This function 'hides' (some of) ELF executable file's symbols.
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* It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
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* Symbols in the global keep list, or which are marked as being undefined,
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* are left alone.
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*
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* An old version of this code shuffled various tables around, turning
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* global symbols to be hidden into local symbols. That lost on the
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* mips, because CALL16 relocs must reference global symbols, and, if
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* those symbols were being hidden, they were no longer global.
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*
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* The new renaming behaviour doesn't take global symbols out of the
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* namespace. However, it's ... unlikely that there will ever be
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* any collisions in practice because of the new method.
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*/
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int
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ELFNAMEEND(hide)(int fd, const char *fn)
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{
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Elf_Ehdr ehdr;
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Elf_Shdr *shdrp = NULL;
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int symtabsnum, strtabsnum;
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Elf_Sym *symtabp = NULL;
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char *strtabp = NULL, *nstrtabp = NULL;
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Elf_Word j, nsyms;
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Elf_Off stroff, maxoff;
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const char *weirdreason;
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ssize_t shdrsize;
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size_t nstrtab_size, nstrtab_nextoff, fn_size;
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int rv, i, weird;
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rv = 0;
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if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
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goto bad;
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shdrsize = ehdr.e_shnum * ehdr.e_shentsize;
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if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL)
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goto bad;
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if (xreadatoff(fd, shdrp, ehdr.e_shoff, shdrsize, fn) != shdrsize)
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goto bad;
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symtabsnum = strtabsnum = -1;
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maxoff = stroff = 0;
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weird = 0;
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weirdreason = "???";
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for (i = 0; i < ehdr.e_shnum; i++) {
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if (shdrp[i].sh_offset > maxoff) {
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maxoff = shdrp[i].sh_offset;
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}
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switch (shdrp[i].sh_type) {
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case SHT_SYMTAB:
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if (!weird && symtabsnum != -1) {
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weird = 1;
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weirdreason = "multiple symbol tables";
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}
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symtabsnum = i;
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strtabsnum = shdrp[i].sh_link;
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stroff = shdrp[strtabsnum].sh_offset;
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if (!weird && strtabsnum != (ehdr.e_shnum - 1)) {
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weird = 1;
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weirdreason = "string table not last section";
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}
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break;
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}
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}
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if (symtabsnum == -1)
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goto out;
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if (!weird && strtabsnum == -1) {
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weird = 1;
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weirdreason = "no string table found";
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}
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if (!weird && stroff != maxoff) {
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weird = 1;
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weirdreason = "string table section not last in file";
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}
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if (weird) {
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fprintf(stderr, "%s: weird executable (%s); unsupported\n", fn,
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weirdreason);
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goto bad;
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}
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/*
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* load up everything we need
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*/
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/* symbol table */
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if ((symtabp = xmalloc(shdrp[symtabsnum].sh_size, fn, "symbol table"))
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== NULL)
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goto bad;
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if ((size_t)xreadatoff(fd, symtabp, shdrp[symtabsnum].sh_offset,
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shdrp[symtabsnum].sh_size, fn) != shdrp[symtabsnum].sh_size)
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goto bad;
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/* string table */
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if ((strtabp = xmalloc(shdrp[strtabsnum].sh_size, fn, "string table"))
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== NULL)
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goto bad;
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if ((size_t)xreadatoff(fd, strtabp, shdrp[strtabsnum].sh_offset,
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shdrp[strtabsnum].sh_size, fn) != shdrp[strtabsnum].sh_size)
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goto bad;
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nsyms = shdrp[symtabsnum].sh_size / shdrp[symtabsnum].sh_entsize;
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nstrtab_size = 256;
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nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
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if (nstrtabp == NULL)
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goto bad;
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nstrtab_nextoff = 0;
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fn_size = strlen(fn);
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for (j = 0; j < nsyms; j++) {
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Elf_Sym *sp = &symtabp[j];
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const char *symname = strtabp + sp->st_name;
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size_t newent_len;
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/*
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* make sure there's size for the next entry, even if it's
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* as large as it can be.
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*
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* "_$$hide$$ <filename> <symname><NUL>" ->
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* 9 + 3 + sizes of fn and sym name
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*/
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while ((nstrtab_size - nstrtab_nextoff) <
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strlen(symname) + fn_size + 12) {
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nstrtab_size *= 2;
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nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
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"new string table");
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if (nstrtabp == NULL)
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goto bad;
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}
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sp->st_name = nstrtab_nextoff;
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/* if it's a keeper or is undefined, don't rename it. */
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if (in_keep_list(symname) ||
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sp->st_shndx == SHN_UNDEF) {
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newent_len = sprintf(nstrtabp + nstrtab_nextoff,
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"%s", symname) + 1;
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} else {
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newent_len = sprintf(nstrtabp + nstrtab_nextoff,
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"_$$hide$$ %s %s", fn, symname) + 1;
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}
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nstrtab_nextoff += newent_len;
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}
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shdrp[strtabsnum].sh_size = nstrtab_nextoff;
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/*
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* write new tables to the file
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*/
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if (xwriteatoff(fd, shdrp, ehdr.e_shoff, shdrsize, fn) != shdrsize)
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goto bad;
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if ((size_t)xwriteatoff(fd, symtabp, shdrp[symtabsnum].sh_offset,
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shdrp[symtabsnum].sh_size, fn) != shdrp[symtabsnum].sh_size)
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goto bad;
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if ((size_t)xwriteatoff(fd, nstrtabp, shdrp[strtabsnum].sh_offset,
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shdrp[strtabsnum].sh_size, fn) != shdrp[strtabsnum].sh_size)
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goto bad;
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out:
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if (shdrp != NULL)
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free(shdrp);
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if (symtabp != NULL)
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free(symtabp);
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if (strtabp != NULL)
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free(strtabp);
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if (nstrtabp != NULL)
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free(nstrtabp);
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return (rv);
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bad:
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rv = 1;
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goto out;
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}
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#endif /* include this size of ELF */
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