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/* $OpenBSD: copy_elf.c,v 1.1 2013/10/28 09:00:06 patrick Exp $ */
/*
* Copyright (c) 2013 Miodrag Vallat.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdio.h>
#include <err.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/exec_elf.h>
struct image_header;
#define roundup(x, y) ((((x)+((y)-1))/(y))*(y))
extern u_long copy_data(int, const char *, int, const char *, u_long,
struct image_header *, Elf_Word);
u_long copy_mem(void *, int, const char *, u_long, struct image_header *,
Elf_Word);
extern u_long fill_zeroes(int, const char *, u_long, struct image_header *, Elf_Word);
u_long
ELFNAME(copy_elf)(int ifd, const char *iname, int ofd, const char *oname, u_long crc,
struct image_header *ih)
{
ssize_t nbytes;
Elf_Ehdr ehdr, elf;
Elf_Phdr phdr;
Elf_Addr vaddr, ovaddr, svaddr, off, ssym;
Elf_Shdr *shp, *wshp;
Elf_Addr esym = 0, esymval;
int i, sz, havesyms;
nbytes = read(ifd, &ehdr, sizeof ehdr);
if (nbytes == -1)
err(1, "%s", iname);
if (nbytes != sizeof ehdr)
return 0;
elf = ehdr;
if (lseek(ifd, (off_t)elf.e_shoff, SEEK_SET) == -1) {
err(1, "%s unable to seek to section header", iname);
}
sz = elf.e_shnum * sizeof(Elf_Shdr);
shp = calloc(sz, 1);
if (read(ifd, shp, sz) != sz) {
err(1, "%s: read section headers", iname);
}
wshp = calloc(sz, 1);
memcpy(wshp, shp, sz);
/* first walk the load sections to find the kernel addresses */
/* next we walk the sections to find the
* location of esym (first address of data space
*/
for (i = 0; i < ehdr.e_phnum; i++) {
if (lseek(ifd, ehdr.e_phoff + i * ehdr.e_phentsize, SEEK_SET) ==
(off_t)-1)
err(1, "%s", iname);
if (read(ifd, &phdr, sizeof phdr) != sizeof(phdr))
err(1, "%s", iname);
/* assumes it loads in incrementing address order */
if (phdr.p_type == PT_LOAD)
vaddr = phdr.p_vaddr + phdr.p_memsz;
}
/* ok, we need to write the elf header and section header
* which contains info about the not yet written section data
* however due to crc the data all has to be written in order
* which means walking the structures twice once to precompute
* the data, once to write the data.
*/
ssym = vaddr;
vaddr += roundup((sizeof(Elf_Ehdr) + sz), sizeof(Elf_Addr));
off = roundup((sizeof(Elf_Ehdr) + sz), sizeof(Elf_Addr));
for (i = 0; i < elf.e_shnum; i++) {
if (esym == 0 && shp[i].sh_flags & SHF_WRITE) {
esym = shp[i].sh_addr;
}
if (shp[i].sh_type == SHT_SYMTAB ||
shp[i].sh_type == SHT_STRTAB) {
#ifdef DEBUG
fprintf(stderr, "shdr %d %d/%d off %lx\n", i, shp[i].sh_type,
roundup(shp[i].sh_size, sizeof(Elf_Addr)), off);
#endif
/* data is at shp[i].sh_offset of len shp[i].sh_size */
wshp[i].sh_offset = off;
off += roundup(shp[i].sh_size, sizeof(Elf_Addr));
vaddr += roundup(shp[i].sh_size, sizeof(Elf_Addr));
}
}
esymval = vaddr;
#ifdef DEBUG
fprintf(stderr, "esymval %lx size %ld\n", esymval, esymval - ssym);
#endif
for (i = 0; i < ehdr.e_phnum; i++) {
#ifdef DEBUG
fprintf(stderr, "phdr %d/%d\n", i, ehdr.e_phnum);
#endif
if (lseek(ifd, ehdr.e_phoff + i * ehdr.e_phentsize, SEEK_SET) ==
(off_t)-1)
err(1, "%s", iname);
if (read(ifd, &phdr, sizeof phdr) != sizeof(phdr))
err(1, "%s", iname);
#ifdef DEBUG
fprintf(stderr, "vaddr %p offset %p filesz %p memsz %p\n",
phdr.p_vaddr, phdr.p_offset, phdr.p_filesz, phdr.p_memsz);
#endif
if (i == 0)
vaddr = phdr.p_vaddr;
else if (vaddr != phdr.p_vaddr) {
#ifdef DEBUG
fprintf(stderr, "gap %p->%p\n", vaddr, phdr.p_vaddr);
#endif
/* fill the gap between the previous phdr if any */
crc = fill_zeroes(ofd, oname, crc, ih,
phdr.p_vaddr - vaddr);
vaddr = phdr.p_vaddr;
}
if (phdr.p_filesz != 0) {
#ifdef DEBUG
fprintf(stderr, "copying %p from infile %p\n",
phdr.p_filesz, phdr.p_offset);
#endif
/* esym will be in the data portion of a region */
if (esym >= phdr.p_vaddr &&
esym < phdr.p_vaddr + phdr.p_filesz) {
/* load the region up to the esym
* (may be empty)
*/
Elf_Addr loadlen = esym - phdr.p_vaddr;
if (lseek(ifd, phdr.p_offset, SEEK_SET) ==
(off_t)-1)
err(1, "%s", iname);
crc = copy_data(ifd, iname, ofd, oname, crc,
ih, loadlen);
crc = copy_mem(&esymval, ofd, oname, crc, ih,
sizeof(esymval));
if (lseek(ifd, phdr.p_offset + loadlen +
sizeof(esymval), SEEK_SET) == (off_t)-1)
err(1, "%s", iname);
crc = copy_data(ifd, iname, ofd, oname, crc,
ih, phdr.p_filesz - loadlen -
sizeof(esymval));
} else {
if (lseek(ifd, phdr.p_offset, SEEK_SET) ==
(off_t)-1)
err(1, "%s", iname);
crc = copy_data(ifd, iname, ofd, oname, crc,
ih, phdr.p_filesz);
}
if (phdr.p_memsz - phdr.p_filesz != 0) {
#ifdef DEBUG
fprintf(stderr, "zeroing %p\n",
phdr.p_memsz - phdr.p_filesz);
#endif
crc = fill_zeroes(ofd, oname, crc, ih,
phdr.p_memsz - phdr.p_filesz);
}
ovaddr = vaddr + phdr.p_memsz;
} else {
ovaddr = vaddr;
}
/*
* If p_filesz == 0, this is likely .bss, which we do not
* need to provide. If it's not the last phdr, the gap
* filling code will output the necessary zeroes anyway.
*/
vaddr += phdr.p_memsz;
}
vaddr = roundup(vaddr, sizeof(Elf_Addr));
if (vaddr != ovaddr) {
#ifdef DEBUG
fprintf(stderr, "gap %p->%p\n", vaddr, phdr.p_vaddr);
#endif
/* fill the gap between the previous phdr if not aligned */
crc = fill_zeroes(ofd, oname, crc, ih, vaddr - ovaddr);
}
for (havesyms = i = 0; i < elf.e_shnum; i++)
if (shp[i].sh_type == SHT_SYMTAB)
havesyms = 1;
if (havesyms == 0)
return crc;
elf.e_phoff = 0;
elf.e_shoff = sizeof(Elf_Ehdr);
elf.e_phentsize = 0;
elf.e_phnum = 0;
crc = copy_mem(&elf, ofd, oname, crc, ih, sizeof(elf));
crc = copy_mem(wshp, ofd, oname, crc, ih, sz);
off = sizeof(elf) + sz;
off = roundup((sizeof(Elf_Ehdr) + sz), sizeof(Elf_Addr));
for (i = 0; i < elf.e_shnum; i++) {
if (shp[i].sh_type == SHT_SYMTAB ||
shp[i].sh_type == SHT_STRTAB) {
/* data is at shp[i].sh_offset of len shp[i].sh_size */
if (lseek(ifd, shp[i].sh_offset, SEEK_SET) == -1) {
err(1, "%s", iname);
}
off += shp[i].sh_size;
crc = copy_data(ifd, iname, ofd, oname, crc, ih,
shp[i].sh_size);
}
}
return crc;
}
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