elf.c revision a734c64bff58bda2fa48c2795453e092167b0ff7
/*
* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
/**
* @file
*
* ELF image format
*
* A "pure" ELF image is not a bootable image. There are various
* bootable formats based upon ELF (e.g. Multiboot), which share
* common ELF-related functionality.
*/
#include <errno.h>
#include <elf.h>
#include <ipxe/uaccess.h>
#include <ipxe/segment.h>
#include <ipxe/image.h>
#include <ipxe/elf.h>
typedef Elf32_Ehdr Elf_Ehdr;
typedef Elf32_Phdr Elf_Phdr;
typedef Elf32_Off Elf_Off;
#define ELFCLASS ELFCLASS32
/**
* Load ELF segment into memory
*
* @v image ELF file
* @v phdr ELF program header
* @v ehdr ELF executable header
* @ret entry Entry point, if found
* @ret max Maximum used address
* @ret rc Return status code
*/
static int elf_load_segment ( struct image *image, Elf_Phdr *phdr,
Elf_Ehdr *ehdr, physaddr_t *entry,
physaddr_t *max ) {
physaddr_t dest;
physaddr_t end;
userptr_t buffer;
unsigned long e_offset;
int rc;
/* Do nothing for non-PT_LOAD segments */
if ( phdr->p_type != PT_LOAD )
return 0;
/* Check segment lies within image */
if ( ( phdr->p_offset + phdr->p_filesz ) > image->len ) {
DBGC ( image, "ELF %p segment outside image\n", image );
return -ENOEXEC;
}
/* Find start address: use physical address for preference,
* fall back to virtual address if no physical address
* supplied.
*/
dest = phdr->p_paddr;
if ( ! dest )
dest = phdr->p_vaddr;
if ( ! dest ) {
DBGC ( image, "ELF %p segment loads to physical address 0\n",
image );
return -ENOEXEC;
}
buffer = phys_to_user ( dest );
end = ( dest + phdr->p_memsz );
DBGC ( image, "ELF %p loading segment [%x,%x) to [%x,%x,%x)\n", image,
phdr->p_offset, ( phdr->p_offset + phdr->p_filesz ),
phdr->p_paddr, ( phdr->p_paddr + phdr->p_filesz ),
( phdr->p_paddr + phdr->p_memsz ) );
/* Verify and prepare segment */
if ( ( rc = prep_segment ( buffer, phdr->p_filesz,
phdr->p_memsz ) ) != 0 ) {
DBGC ( image, "ELF %p could not prepare segment: %s\n",
image, strerror ( rc ) );
return rc;
}
/* Update maximum used address, if applicable */
if ( end > *max )
*max = end;
/* Copy image to segment */
memcpy_user ( buffer, 0, image->data, phdr->p_offset, phdr->p_filesz );
/* Set execution address, if it lies within this segment */
if ( ( e_offset = ( ehdr->e_entry - dest ) ) < phdr->p_filesz ) {
*entry = ehdr->e_entry;
DBGC ( image, "ELF %p found physical entry point at %lx\n",
image, *entry );
} else if ( ( e_offset = ( ehdr->e_entry - phdr->p_vaddr ) )
< phdr->p_filesz ) {
if ( ! *entry ) {
*entry = ( dest + e_offset );
DBGC ( image, "ELF %p found virtual entry point at %lx"
" (virt %lx)\n", image, *entry,
( ( unsigned long ) ehdr->e_entry ) );
}
}
return 0;
}
/**
* Load ELF image into memory
*
* @v image ELF file
* @ret entry Entry point
* @ret max Maximum used address
* @ret rc Return status code
*/
int elf_load ( struct image *image, physaddr_t *entry, physaddr_t *max ) {
static const uint8_t e_ident[] = {
[EI_MAG0] = ELFMAG0,
[EI_MAG1] = ELFMAG1,
[EI_MAG2] = ELFMAG2,
[EI_MAG3] = ELFMAG3,
[EI_CLASS] = ELFCLASS,
};
Elf_Ehdr ehdr;
Elf_Phdr phdr;
Elf_Off phoff;
unsigned int phnum;
int rc;
/* Read ELF header */
copy_from_user ( &ehdr, image->data, 0, sizeof ( ehdr ) );
if ( memcmp ( &ehdr.e_ident[EI_MAG0], e_ident,
sizeof ( e_ident ) ) != 0 ) {
DBGC ( image, "ELF %p has invalid signature\n", image );
return -ENOEXEC;
}
/* Initialise maximum used address */
*max = 0;
/* Invalidate entry point */
*entry = 0;
/* Read ELF program headers */
for ( phoff = ehdr.e_phoff , phnum = ehdr.e_phnum ; phnum ;
phoff += ehdr.e_phentsize, phnum-- ) {
if ( phoff > image->len ) {
DBGC ( image, "ELF %p program header %d outside "
"image\n", image, phnum );
return -ENOEXEC;
}
copy_from_user ( &phdr, image->data, phoff, sizeof ( phdr ) );
if ( ( rc = elf_load_segment ( image, &phdr, &ehdr,
entry, max ) ) != 0 ) {
return rc;
}
}
/* Check for a valid execution address */
if ( ! *entry ) {
DBGC ( image, "ELF %p entry point %lx outside image\n",
image, ( ( unsigned long ) ehdr.e_entry ) );
return -ENOEXEC;
}
return 0;
}