ipxe/src/arch/i386/image/sdi.c

/*
 * Copyright (C) 2012 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 (at your option) 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.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <realmode.h>
#include <sdi.h>
#include <ipxe/image.h>
#include <ipxe/features.h>

/** @file
 *
 * System Deployment Image (SDI)
 *
 * Based on the MSDN article "RAM boot using SDI in Windows XP
 * Embedded with Service Pack 1", available at the time of writing
 * from:
 *
 *   http://msdn.microsoft.com/en-us/library/ms838543.aspx
 */

FEATURE ( FEATURE_IMAGE, "SDI", DHCP_EB_FEATURE_SDI, 1 );

/**
 * Parse SDI image header
 *
 * @v image		SDI file
 * @v sdi		SDI header to fill in
 * @ret rc		Return status code
 */
static int sdi_parse_header ( struct image *image, struct sdi_header *sdi ) {

	/* Sanity check */
	if ( image->len < sizeof ( *sdi ) ) {
		DBGC ( image, "SDI %p too short for SDI header\n", image );
		return -ENOEXEC;
	}

	/* Read in header */
	copy_from_user ( sdi, image->data, 0, sizeof ( *sdi ) );

	/* Check signature */
	if ( sdi->magic != SDI_MAGIC ) {
		DBGC ( image, "SDI %p is not an SDI image\n", image );
		return -ENOEXEC;
	}

	return 0;
}

/**
 * Execute SDI image
 *
 * @v image		SDI file
 * @ret rc		Return status code
 */
static int sdi_exec ( struct image *image ) {
	struct sdi_header sdi;
	uint32_t sdiptr;
	int rc;

	/* Parse image header */
	if ( ( rc = sdi_parse_header ( image, &sdi ) ) != 0 )
		return rc;

	/* Check that image is bootable */
	if ( sdi.boot_size == 0 ) {
		DBGC ( image, "SDI %p is not bootable\n", image );
		return -ENOTTY;
	}
	DBGC ( image, "SDI %p image at %08lx+%08zx\n",
	       image, user_to_phys ( image->data, 0 ), image->len );
	DBGC ( image, "SDI %p boot code at %08lx+%llx\n", image,
	       user_to_phys ( image->data, sdi.boot_offset ), sdi.boot_size );

	/* Copy boot code */
	memcpy_user ( real_to_user ( SDI_BOOT_SEG, SDI_BOOT_OFF ), 0,
		      image->data, sdi.boot_offset, sdi.boot_size );

	/* Jump to boot code */
	sdiptr = ( user_to_phys ( image->data, 0 ) | SDI_WTF );
	__asm__ __volatile__ ( REAL_CODE ( "ljmp %0, %1\n\t" )
			       : : "i" ( SDI_BOOT_SEG ),
				   "i" ( SDI_BOOT_OFF ),
				   "d" ( sdiptr ) );

	/* There is no way for the image to return, since we provide
	 * no return address.
	 */
	assert ( 0 );

	return -ECANCELED; /* -EIMPOSSIBLE */
}

/**
 * Probe SDI image
 *
 * @v image		SDI file
 * @ret rc		Return status code
 */
static int sdi_probe ( struct image *image ) {
	struct sdi_header sdi;
	int rc;

	/* Parse image */
	if ( ( rc = sdi_parse_header ( image, &sdi ) ) != 0 )
		return rc;

	return 0;
}

/** SDI image type */
struct image_type sdi_image_type __image_type ( PROBE_NORMAL ) = {
	.name = "SDI",
	.probe = sdi_probe,
	.exec = sdi_exec,
};