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370 lines
8.8 KiB
370 lines
8.8 KiB
/* Test program for copying a whole ELF file using libelf.
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Copyright (C) 2018 Red Hat, Inc.
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This file is part of elfutils.
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This file is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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elfutils is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <errno.h>
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#include <fcntl.h>
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#include <inttypes.h>
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#include <stdbool.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 <sys/types.h>
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#include <sys/stat.h>
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#include ELFUTILS_HEADER(elf)
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#include <gelf.h>
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/* shstrndx is special, might overflow into section zero header sh_link. */
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static int
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setshstrndx (Elf *elf, size_t ndx)
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{
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printf ("setshstrndx: %zd\n", ndx);
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GElf_Ehdr ehdr_mem;
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GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
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if (ehdr == NULL)
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return -1;
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if (ndx < SHN_LORESERVE)
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ehdr->e_shstrndx = ndx;
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else
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{
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ehdr->e_shstrndx = SHN_XINDEX;
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Elf_Scn *zscn = elf_getscn (elf, 0);
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GElf_Shdr zshdr_mem;
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GElf_Shdr *zshdr = gelf_getshdr (zscn, &zshdr_mem);
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if (zshdr == NULL)
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return -1;
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zshdr->sh_link = ndx;
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if (gelf_update_shdr (zscn, zshdr) == 0)
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return -1;
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}
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if (gelf_update_ehdr (elf, ehdr) == 0)
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return -1;
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return 0;
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}
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/* Copies all elements of an ELF file either using mmap or read. */
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static void
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copy_elf (const char *in, const char *out, bool use_mmap, bool reverse_offs)
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{
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printf ("\ncopy_elf: %s -> %s (%s,%s)\n", in, out,
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use_mmap ? "mmap" : "read",
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reverse_offs ? "reverse" : "same");
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/* Existing ELF file. */
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int fda = open (in, O_RDONLY);
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if (fda < 0)
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{
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fprintf (stderr, "Couldn't open file '%s': %s\n",
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in, strerror (errno));
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exit (1);
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}
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Elf *elfa = elf_begin (fda, use_mmap ? ELF_C_READ_MMAP : ELF_C_READ, NULL);
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if (elfa == NULL)
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{
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fprintf (stderr, "Couldn't open ELF file '%s': %s\n",
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in, elf_errmsg (-1));
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exit (1);
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}
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/* Open new file. */
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int fdb = open (out, O_RDWR | O_CREAT | O_TRUNC, 0644);
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if (fdb < 0)
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{
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fprintf (stderr, "Couldn't create file '%s': %s\n",
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out, strerror (errno));
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exit (1);
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}
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Elf *elfb = elf_begin (fdb, use_mmap ? ELF_C_WRITE_MMAP : ELF_C_WRITE, NULL);
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if (elfb == NULL)
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{
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fprintf (stderr, "Couldn't create ELF file '%s': %s\n",
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out, elf_errmsg (-1));
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exit (1);
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}
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// Copy ELF header.
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GElf_Ehdr ehdr_mema;
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GElf_Ehdr *ehdra = gelf_getehdr (elfa, &ehdr_mema);
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if (ehdra == NULL)
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{
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printf ("cannot get ELF header: %s\n", elf_errmsg (-1));
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exit (1);
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}
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int class = gelf_getclass (elfa);
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// Create an ELF header.
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if (gelf_newehdr (elfb, class) == 0)
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{
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printf ("cannot create ELF header: %s\n", elf_errmsg (-1));
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exit (1);
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}
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/* New elf header is an exact copy. */
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GElf_Ehdr ehdr_memb;
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GElf_Ehdr *ehdrb = &ehdr_memb;
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*ehdrb = *ehdra;
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if (gelf_update_ehdr (elfb, ehdrb) == 0)
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{
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printf ("cannot update ELF header: %s\n", elf_errmsg (-1));
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exit (1);
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}
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/* shstrndx is special. (Technically phdrnum and shdrnum are also
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special, but they are handled by libelf.) */
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size_t shstrndx;
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if (elf_getshdrstrndx (elfa, &shstrndx) < 0)
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{
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printf ("cannot get shstrndx: %s\n", elf_errmsg (-1));
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exit (1);
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}
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if (setshstrndx (elfb, shstrndx) < 0)
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{
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printf ("cannot set shstrndx: %s\n", elf_errmsg (-1));
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exit (1);
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}
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/* If there are phdrs, copy them over. */
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size_t phnum;
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if (elf_getphdrnum (elfa, &phnum) != 0)
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{
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printf ("cannot get phdrs: %s\n", elf_errmsg (-1));
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exit (1);
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}
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if (phnum > 0)
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{
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if (gelf_newphdr (elfb, phnum) == 0)
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{
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printf ("cannot create phdrs: %s\n", elf_errmsg (-1));
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exit (1);
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}
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for (size_t cnt = 0; cnt < phnum; ++cnt)
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{
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GElf_Phdr phdr_mem;
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GElf_Phdr *phdr = gelf_getphdr (elfa, cnt, &phdr_mem);
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if (phdr == NULL)
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{
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printf ("couldn't get phdr %zd: %s\n", cnt, elf_errmsg (-1));
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exit (1);
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}
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if (gelf_update_phdr (elfb, cnt, phdr) == 0)
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{
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printf ("couldn't update phdr %zd: %s\n", cnt, elf_errmsg (-1));
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exit (1);
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}
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}
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}
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GElf_Off *offs = NULL;
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size_t shnum;
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if (reverse_offs)
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{
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if (elf_getshdrnum (elfa, &shnum) < 0)
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{
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printf ("couldn't get shdrnum: %s\n", elf_errmsg (-1));
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exit (1);
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}
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offs = (GElf_Off *) malloc (shnum * sizeof (GElf_Off));
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if (offs == NULL)
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{
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printf ("couldn't allocate memory for offs\n");
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exit (1);
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}
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}
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/* Copy all sections, headers and data. */
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Elf_Scn *scn = NULL;
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size_t last_off = 0;
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GElf_Shdr last_shdr = { .sh_type = SHT_NULL };
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while ((scn = elf_nextscn (elfa, scn)) != NULL)
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{
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/* Get the header. */
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GElf_Shdr shdr;
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if (gelf_getshdr (scn, &shdr) == NULL)
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{
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printf ("couldn't get shdr: %s\n", elf_errmsg (-1));
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exit (1);
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}
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if (reverse_offs)
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{
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offs[last_off] = shdr.sh_offset;
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if (last_shdr.sh_type != SHT_NULL
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&& last_shdr.sh_addralign == shdr.sh_addralign
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&& shdr.sh_addralign == 1
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&& last_shdr.sh_type != SHT_NOBITS
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&& shdr.sh_type != SHT_NOBITS
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&& last_shdr.sh_offset + last_shdr.sh_size == shdr.sh_offset
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&& (phnum == 0
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|| ((shdr.sh_flags & SHF_ALLOC) == 0
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&& (last_shdr.sh_flags & SHF_ALLOC) == 0)))
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{
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printf ("Swapping offsets of section %zd and %zd\n",
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last_off, last_off + 1);
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GElf_Word off = offs[last_off - 1];
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offs[last_off - 1] = off + shdr.sh_size;
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offs[last_off] = off;
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last_shdr.sh_type = SHT_NULL;
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}
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else
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{
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last_shdr = shdr;
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offs[last_off] = shdr.sh_offset;
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}
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last_off++;
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}
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/* Create new section. */
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Elf_Scn *new_scn = elf_newscn (elfb);
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if (new_scn == NULL)
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{
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printf ("couldn't create new section: %s\n", elf_errmsg (-1));
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exit (1);
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}
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if (gelf_update_shdr (new_scn, &shdr) == 0)
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{
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printf ("couldn't update shdr: %s\n", elf_errmsg (-1));
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exit (1);
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}
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/* Copy over section data. */
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Elf_Data *data = NULL;
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while ((data = elf_getdata (scn, data)) != NULL)
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{
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Elf_Data *new_data = elf_newdata (new_scn);
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if (new_data == NULL)
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{
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printf ("couldn't create new section data: %s\n",
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elf_errmsg (-1));
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exit (1);
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}
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*new_data = *data;
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}
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}
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if (reverse_offs)
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{
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last_off = 0;
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scn = NULL;
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while ((scn = elf_nextscn (elfb, scn)) != NULL)
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{
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GElf_Shdr shdr;
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if (gelf_getshdr (scn, &shdr) == NULL)
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{
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printf ("couldn't get shdr for updating: %s\n", elf_errmsg (-1));
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exit (1);
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}
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shdr.sh_offset = offs[last_off++];
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if (gelf_update_shdr (scn, &shdr) == 0)
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{
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printf ("couldn't update shdr sh_off: %s\n", elf_errmsg (-1));
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exit (1);
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}
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}
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free (offs);
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}
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/* Write everything to disk. If there are any phdrs, or we want to
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update the offsets, then we want the exact same layout. Do we
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want ELF_F_PERMISSIVE? */
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if (phnum > 0 || reverse_offs)
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elf_flagelf (elfb, ELF_C_SET, ELF_F_LAYOUT);
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if (elf_update (elfb, ELF_C_WRITE) < 0)
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{
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printf ("failure in elf_update: %s\n", elf_errmsg (-1));
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exit (1);
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}
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if (elf_end (elfa) != 0)
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{
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printf ("couldn't cleanup elf '%s': %s\n", in, elf_errmsg (-1));
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exit (1);
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}
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if (close (fda) != 0)
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{
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printf ("couldn't close '%s': %s\n", in, strerror (errno));
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exit (1);
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}
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if (elf_end (elfb) != 0)
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{
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printf ("couldn't cleanup elf '%s': %s\n", out, elf_errmsg (-1));
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exit (1);
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}
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if (close (fdb) != 0)
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{
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printf ("couldn't close '%s': %s\n", out, strerror (errno));
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exit (1);
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}
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}
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int
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main (int argc, const char *argv[])
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{
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elf_version (EV_CURRENT);
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/* Takes the given file, and create a new identical one. */
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if (argc < 3 || argc > 5)
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{
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fprintf (stderr, "elfcopy [--mmap] [--reverse-offs] in.elf out.elf\n");
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exit (1);
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}
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int argn = 1;
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bool use_mmap = false;
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if (strcmp (argv[argn], "--mmap") == 0)
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{
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use_mmap = true;
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argn++;
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}
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bool reverse_offs = false;
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if (strcmp (argv[argn], "--reverse-offs") == 0)
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{
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reverse_offs = true;
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argn++;
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}
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const char *in = argv[argn++];
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const char *out = argv[argn];
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copy_elf (in, out, use_mmap, reverse_offs);
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return 0;
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}
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