elfboot.c

/*
 * Copyright (C) 2008 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <errno.h>
#include <elf.h>
#include <ipxe/image.h>
#include <ipxe/elf.h>
#include <ipxe/features.h>
#include <ipxe/init.h>

/**
 * @file
 *
 * ELF bootable image
 *
 */

FEATURE ( FEATURE_IMAGE, "ELF", DHCP_EB_FEATURE_ELF, 1 );

/**
 * Execute ELF image
 *
 * @v image		ELF image
 * @ret rc		Return status code
 */
static int elfboot_exec ( struct image *image ) {
	physaddr_t entry;
	physaddr_t max;
	int rc;

	/* Load the image using core ELF support */
	if ( ( rc = elf_load ( image, &entry, &max ) ) != 0 ) {
		DBGC ( image, "ELF %p could not load: %s\n",
		       image, strerror ( rc ) );
		return rc;
	}

	/* An ELF image has no callback interface, so we need to shut
	 * down before invoking it.
	 */
	shutdown_boot();

	/* Jump to OS with flat physical addressing */
	DBGC ( image, "ELF %p starting execution at %lx\n", image, entry );
	__asm__ __volatile__ ( PHYS_CODE ( "pushl %%ebp\n\t" /* gcc bug */
					   "call *%%edi\n\t"
					   "popl %%ebp\n\t" /* gcc bug */ )
			       : : "D" ( entry )
			       : "eax", "ebx", "ecx", "edx", "esi", "memory" );

	DBGC ( image, "ELF %p returned\n", image );

	/* It isn't safe to continue after calling shutdown() */
	while ( 1 ) {}

	return -ECANCELED;  /* -EIMPOSSIBLE, anyone? */
}

/**
 * Check that ELF segment uses flat physical addressing
 *
 * @v image		ELF file
 * @v phdr		ELF program header
 * @v dest		Destination address
 * @ret rc		Return status code
 */
static int elfboot_check_segment ( struct image *image, Elf_Phdr *phdr,
				   physaddr_t dest ) {

	/* Check that ELF segment uses flat physical addressing */
	if ( phdr->p_vaddr != dest ) {
		DBGC ( image, "ELF %p uses virtual addressing (phys %x, "
		       "virt %x)\n", image, phdr->p_paddr, phdr->p_vaddr );
		return -ENOEXEC;
	}

	return 0;
}

/**
 * Probe ELF image
 *
 * @v image		ELF file
 * @ret rc		Return status code
 */
static int elfboot_probe ( struct image *image ) {
	Elf32_Ehdr ehdr;
	static const uint8_t e_ident[] = {
		[EI_MAG0]	= ELFMAG0,
		[EI_MAG1]	= ELFMAG1,
		[EI_MAG2]	= ELFMAG2,
		[EI_MAG3]	= ELFMAG3,
		[EI_CLASS]	= ELFCLASS32,
		[EI_DATA]	= ELFDATA2LSB,
		[EI_VERSION]	= EV_CURRENT,
	};
	physaddr_t entry;
	physaddr_t max;
	int rc;

	/* Read ELF header */
	copy_from_user ( &ehdr, image->data, 0, sizeof ( ehdr ) );
	if ( memcmp ( ehdr.e_ident, e_ident, sizeof ( e_ident ) ) != 0 ) {
		DBGC ( image, "Invalid ELF identifier\n" );
		return -ENOEXEC;
	}

	/* Check that this image uses flat physical addressing */
	if ( ( rc = elf_segments ( image, &ehdr, elfboot_check_segment,
				   &entry, &max ) ) != 0 ) {
		DBGC ( image, "Unloadable ELF image\n" );
		return rc;
	}

	return 0;
}

/** ELF image type */
struct image_type elfboot_image_type __image_type ( PROBE_NORMAL ) = {
	.name = "ELF",
	.probe = elfboot_probe,
	.exec = elfboot_exec,
};