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libisofs/libisofs/system_area.c

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/*
* Copyright (c) 2008 Vreixo Formoso
* Copyright (c) 2010 Thomas Schmitt
*
* This file is part of the libisofs project; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* or later as published by the Free Software Foundation.
* See COPYING file for details.
*/
#ifdef HAVE_CONFIG_H
#include "../config.h"
#endif
#include "system_area.h"
#include "eltorito.h"
#include "filesrc.h"
#include <string.h>
#include <stdio.h>
/*
* Create a MBR for an isohybrid enabled ISOLINUX boot image.
* See libisofs/make_isohybrid_mbr.c
* Deprecated.
*/
int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
/*
* The New ISOLINUX MBR Producer.
* Be cautious with changing parameters. Only few combinations are tested.
*
*/
int make_isolinux_mbr(uint32_t *img_blocks, uint32_t boot_lba,
uint32_t mbr_id, int head_count, int sector_count,
int part_offset, int part_number, int fs_type,
uint8_t *buf, int flag);
/*
* @param flag bit0= img_blocks is start address rather than end address:
do not subtract 1
*/
static
void iso_compute_cyl_head_sec(uint32_t *img_blocks, int hpc, int sph,
uint32_t *end_lba, uint32_t *end_sec,
uint32_t *end_head, uint32_t *end_cyl, int flag)
{
uint32_t secs;
/* Partition table unit is 512 bytes per sector, ECMA-119 unit is 2048 */
if (*img_blocks >= 0x40000000)
*img_blocks = 0x40000000 - 1; /* truncate rather than roll over */
if (flag & 1)
secs = *end_lba = *img_blocks * 4; /* first valid 512-lba */
else
secs = *end_lba = *img_blocks * 4 - 1; /* last valid 512-lba */
*end_cyl = secs / (sph * hpc);
secs -= *end_cyl * sph * hpc;
*end_head = secs / sph;
*end_sec = secs - *end_head * sph + 1; /* Sector count starts by 1 */
if (*end_cyl >= 1024) {
*end_cyl = 1023;
*end_head = hpc - 1;
*end_sec = sph;
}
}
/* This is the gesture of grub-mkisofs --protective-msdos-label as explained by
Vladimir Serbinenko <phcoder@gmail.com>, 2 April 2010, on grub-devel@gnu.org
"Currently we use first and not last entry. You need to:
1) Zero-fill 446-510
2) Put 0x55, 0xAA into 510-512
3) Put 0x80 (for bootable partition), 0, 2, 0 (C/H/S of the start), 0xcd
(partition type), [3 bytes of C/H/S end], 0x01, 0x00, 0x00, 0x00 (LBA
start in little endian), [LBA end in little endian] at 446-462
"
"C/H/S end" means the CHS address of the last block in the partition.
It seems that not "[LBA end in little endian]" but "number of blocks"
should go into bytes 458-461. But with a start lba of 1, this is the
same number.
See also http://en.wikipedia.org/wiki/Master_boot_record
flag bit0= do not write 0x55, 0xAA to 510,511
bit1= do not mark partition as bootable
*/
static
int make_grub_msdos_label(uint32_t img_blocks, uint8_t *buf, int flag)
{
uint8_t *wpt;
uint32_t end_lba, end_sec, end_head, end_cyl;
int sph = 63, hpc = 255, i;
iso_compute_cyl_head_sec(&img_blocks, hpc, sph,
&end_lba, &end_sec, &end_head, &end_cyl, 0);
/* 1) Zero-fill 446-510 */
wpt = buf + 446;
memset(wpt, 0, 64);
if (!(flag & 1)) {
/* 2) Put 0x55, 0xAA into 510-512 (actually 510-511) */
buf[510] = 0x55;
buf[511] = 0xAA;
}
if (!(flag & 2)) {
/* 3) Put 0x80 (for bootable partition), */
*(wpt++) = 0x80;
} else {
*(wpt++) = 0;
}
/* 0, 2, 0 (C/H/S of the start), */
*(wpt++) = 0;
*(wpt++) = 2;
*(wpt++) = 0;
/* 0xcd (partition type) */
*(wpt++) = 0xcd;
/* [3 bytes of C/H/S end], */
*(wpt++) = end_head;
*(wpt++) = end_sec | ((end_cyl & 0x300) >> 2);
*(wpt++) = end_cyl & 0xff;
/* 0x01, 0x00, 0x00, 0x00 (LBA start in little endian), */
*(wpt++) = 0x01;
*(wpt++) = 0x00;
*(wpt++) = 0x00;
*(wpt++) = 0x00;
/* [LBA end in little endian] */
for (i = 0; i < 4; i++)
*(wpt++) = (end_lba >> (8 * i)) & 0xff;
/* at 446-462 */
if (wpt - buf != 462) {
fprintf(stderr,
"libisofs: program error in make_grub_msdos_label: \"assert 462\"\n");
return ISO_ASSERT_FAILURE;
}
return ISO_SUCCESS;
}
/* @param flag bit0= zeroize partitions entries 2, 3, 4
*/
static
int iso_offset_partition_start(uint32_t img_blocks, uint32_t partition_offset,
int sph_in, int hpc_in, uint8_t *buf, int flag)
{
uint8_t *wpt;
uint32_t end_lba, end_sec, end_head, end_cyl;
uint32_t start_lba, start_sec, start_head, start_cyl;
int sph = 63, hpc = 255, i;
if (sph_in > 0)
sph = sph_in;
if (hpc_in > 0)
hpc = hpc_in;
iso_compute_cyl_head_sec(&partition_offset, hpc, sph,
&start_lba, &start_sec, &start_head, &start_cyl, 1);
iso_compute_cyl_head_sec(&img_blocks, hpc, sph,
&end_lba, &end_sec, &end_head, &end_cyl, 0);
wpt = buf + 446;
/* Let pass only legal bootability values */
if (*wpt != 0 && *wpt != 0x80)
(*wpt) = 0;
wpt++;
/* C/H/S of the start */
*(wpt++) = start_head;
*(wpt++) = start_sec | ((start_cyl & 0x300) >> 2);
*(wpt++) = end_cyl & 0xff;
/* (partition type) */
wpt++;
/* 3 bytes of C/H/S end */
*(wpt++) = end_head;
*(wpt++) = end_sec | ((end_cyl & 0x300) >> 2);
*(wpt++) = end_cyl & 0xff;
/* LBA start in little endian */
for (i = 0; i < 4; i++)
*(wpt++) = (start_lba >> (8 * i)) & 0xff;
/* Number of sectors in partition, little endian */
end_lba = end_lba - start_lba + 1;
for (i = 0; i < 4; i++)
*(wpt++) = (end_lba >> (8 * i)) & 0xff;
if (wpt - buf != 462) {
fprintf(stderr,
"libisofs: program error in iso_offset_partition_start: \"assert 462\"\n");
return ISO_ASSERT_FAILURE;
}
if (flag & 1) /* zeroize the other partition entries */
memset(wpt, 0, 3 * 16);
return ISO_SUCCESS;
}
int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
{
int ret, int_img_blocks;
uint32_t img_blocks;
if ((t == NULL) || (buf == NULL)) {
return ISO_NULL_POINTER;
}
/* set buf to 0s */
memset(buf, 0, 16 * BLOCK_SIZE);
img_blocks = t->curblock;
if (t->system_area_data != NULL) {
/* Write more or less opaque boot image */
memcpy(buf, t->system_area_data, 16 * BLOCK_SIZE);
} else if (t->catalog != NULL &&
(t->catalog->bootimages[0]->isolinux_options & 0x0a) == 0x02) {
/* Check for isolinux image with magic number of 3.72 and produce
an MBR from our built-in template. (Deprecated since 31 Mar 2010)
*/
if (img_blocks < 0x80000000) {
int_img_blocks= img_blocks;
} else {
int_img_blocks= 0x7ffffff0;
}
ret = make_isohybrid_mbr(t->bootsrc[0]->sections[0].block,
&int_img_blocks, (char*)buf, 0);
if (ret != 1) {
/* error, it should never happen */
return ISO_ASSERT_FAILURE;
}
return ISO_SUCCESS;
}
if (t->system_area_options & 1) {
/* Write GRUB protective msdos label, i.e. a simple partition table */
ret = make_grub_msdos_label(img_blocks, buf, 0);
if (ret != ISO_SUCCESS) /* error should never happen */
return ISO_ASSERT_FAILURE;
} else if(t->system_area_options & 2) {
/* Patch externally provided system area as isohybrid MBR */
if (t->catalog == NULL || t->system_area_data == NULL) {
/* isohybrid makes only sense together with ISOLINUX boot image
and externally provided System Area.
*/
return ISO_ISOLINUX_CANT_PATCH;
}
ret = make_isolinux_mbr(&img_blocks, t->bootsrc[0]->sections[0].block,
(uint32_t) 0, 64, 32, 0, 1, 0x17, buf, 1);
if (ret != 1)
return ret;
} else if(t->partition_offset > 0) {
/* Write a simple partition table. */
ret = make_grub_msdos_label(img_blocks, buf, 2);
if (ret != ISO_SUCCESS) /* error should never happen */
return ISO_ASSERT_FAILURE;
}
if (t->partition_offset > 0) {
/* Adjust partition table to partition offset */
img_blocks = t->curblock; /* value might be altered */
ret = iso_offset_partition_start(img_blocks, t->partition_offset,
t->partition_secs_per_head,
t->partition_heads_per_cyl, buf, 1);
if (ret != ISO_SUCCESS) /* error should never happen */
return ISO_ASSERT_FAILURE;
}
return ISO_SUCCESS;
}
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