path: root/scripts/setupmbr/setupmbr.c

/*
 * Copyright (C) 2009 Juergen Beisert, Pengutronix
 *
 * 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.
 *
 *
 */

/**
 * @file
 * @brief Write the barebox binary to the MBR and the following disk sectors
 *
 * Also patch dedicated locations in the image to make it work at runtime
 *
 * Current restrictions are:
 * - only installs into MBR and the sectors after it
 * - tested only with QEMU
 * - and maybe some others
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <assert.h>

/* include the info from this barebox release */
#include "../../include/generated/utsrelease.h"
#include "../../arch/x86/mach-i386/include/mach/barebox.lds.h"

/** define to disable integrity tests and debug messages */
#define NDEBUG

/* some infos about our target architecture */
#include "arch.h"

/**
 * "Disk Address Packet Structure" to be used when calling int13,
 * function 0x42
 *
 * @note All entries are in target endianess
 */
struct DAPS
{
	uint8_t size;		/**< size of this data set, 0 marks it as invalid */
	uint8_t res1;		/**< always 0 */
	int8_t count;		/**< number of sectors 0...127 to handle */
	uint8_t res2;		/**< always 0 */
	uint16_t offset;	/**< store address: offset */
	uint16_t segment;	/**< store address: segment */
	uint64_t lba;		/**< start sector number in LBA */
} __attribute__ ((packed));

/**
 * Description of one partition table entry (D*S type)
 *
 * @note All entries are in target endianess
 */
struct partition_entry {
	uint8_t boot_indicator;
	uint8_t chs_begin[3];
	uint8_t type;
	uint8_t chs_end[3];
	uint32_t partition_start;	/* LE */
	uint32_t partition_size;	/* LE */
} __attribute__ ((packed));

#ifndef NDEBUG
static void debugout(const struct DAPS *entry, int supress_entry)
{
	if (supress_entry)
		printf("DAPS entry: ");
	else
		printf("DAPS entry % 3u: ", ((unsigned)entry & ( SECTOR_SIZE - 1)) / sizeof(struct DAPS));

	printf("Size: % 2u, Count: % 3d, Offset: 0x%04hX, Segment: 0x%04hX, LBA: %llu\n",
		entry->size, entry->count,
		target2host_16(entry->offset), target2host_16(entry->segment),
		target2host_64(entry->lba));
}
#else
# define debugout(x,y) (__ASSERT_VOID_CAST(0))
#endif

/**
 * Fill *one* DAPS
 * @param sector The DAPS to fill
 * @param count Sector count
 * @param offset Realmode offset in the segment
 * @param segment Real mode segment
 * @param lba LBA of the first sector to read
 * @return 0 on success
 */
static int fill_daps(struct DAPS *sector, unsigned count, unsigned offset, unsigned segment, uint64_t lba)
{
	assert(sector != NULL);
	assert(count < 128);
	assert(offset < 0x10000);
	assert(segment < 0x10000);

	sector->size = sizeof(struct DAPS);
	sector->res1 = 0;
	sector->count = (int8_t)count;
	sector->res2 = 0;
	sector->offset = host2target_16(offset);
	sector->segment = host2target_16(segment);
	sector->lba = host2target_64(lba);

	return 0;
}

/**
 * Mark a DAPS invalid to let the boot loader code stop at this entry.
 * @param sector The DAPS to be marked as invalid
 *
 * Marking as invalid must be done in accordance to the detection method
 * the assembler routine in the boot loader uses:
 * The current code tests for zero in the first two bytes of the DAPS.
 */
static void invalidate_daps(struct DAPS *sector)
{
	sector->size = MARK_DAPS_INVALID;
	sector->res1 = 0;
}

/**
 * Create the indirect sector with the DAPS entries
 * @param daps_table Where to store the entries
 * @param size Size of the whole image in bytes
 * @param pers_sector_count Count of sectors to skip after MBR for the persistent environment storage
 * @return 0 on success
 *
 * This routine calculates the DAPS entries for the case the whole
 * barebox images fits into the MBR itself and the sectors after it.
 * This means the start of the first partition must keep enough sectors
 * unused.
 * It also skips 'pers_sector_count' sectors after the MBR for special
 * usage if given.
 */
static int barebox_linear_image(struct DAPS *daps_table, off_t size, long pers_sector_count)
{
	unsigned offset = LOAD_AREA, next_offset;
	unsigned segment = LOAD_SEGMENT;
	unsigned chunk_size, i = 0;
	uint64_t lba = 2 + pers_sector_count;
	int rc;

	/*
	 * We can load up to 127 sectors in one chunk. What a bad number...
	 * So, we will load in chunks of 32 kiB.
	 */

	/* at runtime two sectors from the image are already loaded: MBR and indirect */
	size -= 2 * SECTOR_SIZE;
	/* and now round up to multiple of sector size */
	size = (size + SECTOR_SIZE - 1) & ~(SECTOR_SIZE - 1);

	/*
	 * The largest image we can load with this method is:
	 * (SECTOR_SIZE / sizeof(DAPS) - 1) * 32 kiB
	 * For a 512 byte sector and a 16 byte DAPS:
	 * (512 / 16 - 1) * 32 kiB = 992 kiB
	 * Note: '- 1' to consider one entry is required to pad to a 32 kiB boundary
	 */

	if (size >= (SECTOR_SIZE / sizeof(struct DAPS) - 1) * 32 * 1024) {
		fprintf(stderr, "Image too large to boot. Max size is %zu kiB, image size is %lu kiB\n",
			(SECTOR_SIZE / sizeof(struct DAPS) - 1) * 32, size / 1024);
		return -1;
	}

	if (size > 32 * 1024) {
		/* first fill up until the next 32 k boundary */
		next_offset = (offset + 32 * 1024 -1) & ~0x7fff;
		chunk_size = next_offset - offset;
		if (chunk_size & (SECTOR_SIZE-1)) {
			fprintf(stderr, "Unable to pad from %X to %X in multiple of sectors\n", offset, next_offset);
			return -1;
		}

		rc = fill_daps(&daps_table[i], chunk_size / SECTOR_SIZE, offset, segment, lba);
		if (rc != 0)
			return -1;
		debugout(&daps_table[i], 0);

		/* calculate values to enter the loop for the other entries */
		size -= chunk_size;
		i++;
		lba += chunk_size / SECTOR_SIZE;
		offset += chunk_size;
		if (offset >= 0x10000) {
			segment += 4096;
			offset = 0;
		}

		/*
		 * Now load the remaining image part in 32 kiB chunks
		 */
		while (size) {
			if (size >= 32 * 1024 ) {
				if (i >= (SECTOR_SIZE / sizeof(struct DAPS))) {
					fprintf(stderr, "Internal tool error: Too many DAPS entries!\n");
					return -1;
				}
				rc = fill_daps(&daps_table[i], 64, offset, segment, lba);
				if (rc != 0)
					return -1;
				debugout(&daps_table[i], 0);

				size -= 32 * 1024;
				lba += 64;
				offset += 32 * 1024;
				if (offset >= 0x10000) {
					segment += 4096;
					offset = 0;
				}
				i++;
			} else {
				if (i >= (SECTOR_SIZE / sizeof(struct DAPS))) {
					fprintf(stderr, "Internal tool error: Too many DAPS entries!\n");
					return -1;
				}
				rc = fill_daps(&daps_table[i], size / SECTOR_SIZE, offset, segment, lba);
				if (rc != 0)
					return -1;
				debugout(&daps_table[i], 0);
				size = 0;	/* finished */
				i++;
			}
		};
	} else {
		/* less than 32 kiB. Very small image... */
		rc = fill_daps(&daps_table[i], size / SECTOR_SIZE, offset, segment, lba);
		if (rc != 0)
			return -1;
		debugout(&daps_table[i], 0);
		i++;
	}

	/*
	 * Do not mark an entry as invalid if the buffer is full. The
	 * boot code stops if all entries of a buffer are read.
	 */
	if (i >= (SECTOR_SIZE / sizeof(struct DAPS)))
		return 0;

	/* mark the last DAPS invalid */
	invalidate_daps(&daps_table[i]);
	debugout(&daps_table[i], 0);

	return 0;
}

/**
 * Do some simple sanity checks if this sector could be an MBR
 * @param sector Sector with data to check
 * @param size Size of the buffer
 * @return 0 if successfull
 */
static int check_for_valid_mbr(const uint8_t *sector, off_t size)
{
	if (size < SECTOR_SIZE) {
		fprintf(stderr, "MBR too small to be valid\n");
		return -1;
	}

	if ((sector[OFFSET_OF_SIGNATURE] != 0x55) ||
		(sector[OFFSET_OF_SIGNATURE + 1] != 0xAA)) {
		fprintf(stderr, "No MBR signature found\n");
		return -1;
	}

	/* FIXME: try to check if there is a valid partition table */
	return 0;
}

/**
 * Check space between start of the image and the start of the first partition
 * @param hd_image HD image to examine
 * @param size Size of the barebox image
 * @return 0 on success, -1 if the barebox image is too large
 */
static int check_for_space(const void *hd_image, off_t size)
{
	struct partition_entry *partition;
	uint8_t *mbr_disk_sector = (uint8_t*)hd_image;
	off_t spare_sector_count;

	assert(hd_image != NULL);
	assert(size > 0);

	if (check_for_valid_mbr(hd_image, size) != 0)
		return -1;

	/* where to read */
	partition = (struct partition_entry*) &mbr_disk_sector[OFFSET_OF_PARTITION_TABLE];

	/* TODO describes the first entry always the first partition? */
	spare_sector_count = target2host_32(partition->partition_start);

#ifdef DEBUG
	printf("Debug: Required free sectors for barebox prior first partition: %lu, hd image provides: %lu\n",
		(size + SECTOR_SIZE - 1) / SECTOR_SIZE, spare_sector_count);
#endif
	spare_sector_count *= SECTOR_SIZE;
	if (spare_sector_count < size) {
		fprintf(stderr, "Not enough space after MBR to store barebox\n");
		fprintf(stderr, "Move begin of the first partition beyond sector %lu\n", (size + SECTOR_SIZE - 1) / SECTOR_SIZE);
		return -1;
	}

	return 0;
}

/**
 * Setup the persistent environment storage information
 * @param patch_area Where to patch
 * @param pers_sector_start Start sector of the persistent environment storage
 * @param pers_sector_count Count of sectors for the persistent environment storage
 * @return 0 on success
 */
static int store_pers_env_info(void *patch_area, uint64_t pers_sector_start, long pers_sector_count)
{
	uint64_t *start_lba = (uint64_t*)(patch_area + PATCH_AREA_PERS_START);
	uint16_t *count_lba = (uint16_t*)(patch_area + PATCH_AREA_PERS_SIZE);

	assert(patch_area != NULL);
	assert(pers_sector_count >= 0);

	if (pers_sector_count == 0) {
		*count_lba = host2target_16(PATCH_AREA_PERS_SIZE_UNUSED);
		return 0;
	}

	*start_lba = host2target_64(pers_sector_start);
	*count_lba = host2target_16(pers_sector_count);

	return 0;
}

/**
 * Prepare the MBR and indirect sector for runtime
 * @param fd_barebox barebox image to use
 * @param fd_hd Hard disk image to prepare
 * @param pers_sector_count Count of sectors to skip after MBR for the persistent environment storage
 * @return 0 on success
 *
 * This routine expects a prepared hard disk image file with a partition table
 * in its first sector. This method only is currently supported.
 */
static int barebox_overlay_mbr(int fd_barebox, int fd_hd, long pers_sector_count)
{
	const void *barebox_image;
	void *hd_image;
	int rc;
	struct stat sb;
	struct DAPS *embed;	/* part of the MBR */
	struct DAPS *indirect;	/* sector with indirect DAPS */
	off_t required_size;

	if (fstat(fd_barebox, &sb) == -1) {
		perror("fstat");
		return -1;
	}

	/* the barebox image won't be touched */
	barebox_image = mmap(NULL, sb.st_size,  PROT_READ, MAP_SHARED, fd_barebox, 0);
	if (barebox_image == MAP_FAILED) {
		perror("mmap");
		return -1;
	}

	rc = check_for_valid_mbr(barebox_image, sb.st_size);
	if (rc != 0) {
		fprintf(stderr, "barebox image seems not valid: Bad MBR signature\n");
		goto on_error_hd;
	}

	/*
	 * the persistent environment storage is in front of the main
	 * barebox image. To handle both, we need more space in front of the
	 * the first partition.
	 */
	required_size = sb.st_size + pers_sector_count * SECTOR_SIZE;

	/* the hd image will be modified */
	hd_image = mmap(NULL, required_size,  PROT_READ | PROT_WRITE,
					MAP_SHARED, fd_hd, 0);
	if (hd_image == MAP_FAILED) {
		perror("mmap");
		rc = -1;
		goto on_error_hd;
	}

	/* check for space */
	rc = check_for_space(hd_image, required_size);
	if (rc != 0)
		goto on_error_space;

	/* embed barebox's boot code into the disk drive image */
	memcpy(hd_image, barebox_image, OFFSET_OF_PARTITION_TABLE);

	/*
	 * embed the barebox main image into the disk drive image,
	 * but keep the persistent environment storage untouched
	 * (if defined), e.g. store the main image behind this special area.
	 */
	memcpy(hd_image + ((pers_sector_count + 1) * SECTOR_SIZE),
			barebox_image + SECTOR_SIZE, sb.st_size - SECTOR_SIZE);

	/* now, prepare this hard disk image for BIOS based booting */
	embed = hd_image + PATCH_AREA;
	indirect = hd_image + ((pers_sector_count + 1) * SECTOR_SIZE);

	/*
	 * Fill the embedded DAPS to let the basic boot code find the
	 * indirect sector at runtime
	 */
#ifdef DEBUG
	printf("Debug: Fill in embedded DAPS\n");
#endif
	rc = fill_daps(embed, 1, INDIRECT_AREA, INDIRECT_SEGMENT,
				1 + pers_sector_count);
	if (rc != 0)
		goto on_error_space;
	debugout(embed, 1);

#ifdef DEBUG
	printf("Debug: Fill in indirect sector\n");
#endif
	/*
	 * fill the indirect sector with the remaining DAPS to load the
	 * whole barebox image at runtime
	 */
	rc = barebox_linear_image(indirect, sb.st_size, pers_sector_count);
	if (rc != 0)
		goto on_error_space;

	/*
	 * TODO: Replace the fixed LBA starting number by a calculated one,
	 * to support barebox as a chained loader in a different start
	 * sector than the MBR
	 */
	rc = store_pers_env_info(embed, 1, pers_sector_count);
	if (rc != 0)
		goto on_error_space;

on_error_space:
	munmap(hd_image, required_size);

on_error_hd:
	munmap((void*)barebox_image, sb.st_size);

	return rc;
}

static void print_usage(const char *pname)
{
	printf("%s: Preparing a hard disk image for boot with barebox on x86.\n", pname);
	printf("Usage is\n %s [options] -m <barebox image> -d <hd image>\n", pname);
	printf(" [options] are:\n -s <count> sector count of the persistent environment storage\n");
	printf(" <barebox image> barebox's boot image file\n");
	printf(" <hd image> HD image to store the barebox image\n");
	printf(" If no '-s <x>' was given, barebox occupies sectors 0 to n, else sector 0 and x+1 to n\n");
}

int main(int argc, char *argv[])
{
	int rc = 0, c;
	char *barebox_image_filename = NULL, *hd_image_filename = NULL;
	int fd_barebox_image = 0, fd_hd_image = 0;
	long barebox_pers_size = -1;

	if (argc == 1) {
		print_usage(argv[0]);
		exit(0);
	}

	/* handle command line options first */
	while (1) {
		c = getopt(argc, argv, "m:d:s:hv");
		if (c == -1)
			break;

		switch (c) {
		case 's':
			barebox_pers_size = strtol(optarg, NULL, 0);
			break;
		case 'm':
			barebox_image_filename = strdup(optarg);
			break;
		case 'd':
			hd_image_filename = strdup(optarg);
			break;
		case 'h':
			print_usage(argv[0]);
			rc = 0;
			goto on_error;
		case 'v':
			printf("setupmbr for u-boot-v%s\n", UTS_RELEASE);
			printf("Send bug reports to 'barebox@lists.infradead.org'\n");
			rc = 0;
			goto on_error;
		}
	}

	if (barebox_image_filename == NULL) {
		print_usage(argv[0]);
		rc = -1;
		goto on_error;
	}

	fd_barebox_image = open(barebox_image_filename, O_RDONLY);
	if (fd_barebox_image == -1) {
		fprintf(stderr, "Cannot open '%s' for reading\n",
				barebox_image_filename);
		rc = -1;
		goto on_error;
	}

	fd_hd_image = open(hd_image_filename, O_RDWR);
	if (fd_hd_image == -1) {
		fprintf(stderr, "Cannot open '%s'\n", hd_image_filename);
		rc = -1;
		goto on_error;
	}

	if (barebox_pers_size < 0)
		barebox_pers_size = 0;

	rc = barebox_overlay_mbr(fd_barebox_image, fd_hd_image, barebox_pers_size);

on_error:
	if (fd_barebox_image != -1)
		close(fd_barebox_image);
	if (fd_hd_image != -1)
		close(fd_hd_image);

	if (barebox_image_filename != NULL)
		free(barebox_image_filename);
	if (hd_image_filename != NULL)
		free(hd_image_filename);

	return rc;
}