Archipelago » qemu

/*

 * Block driver for Conectix/Microsoft Virtual PC images

 *

 * Copyright (c) 2005 Alex Beregszaszi

 * Copyright (c) 2009 Kevin Wolf <kwolf@suse.de>

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "qemu-common.h"

#include "block_int.h"

/**************************************************************/

#define HEADER_SIZE 512

//#define CACHE

enum vhd_type {

    VHD_FIXED           = 2,

    VHD_DYNAMIC         = 3,

    VHD_DIFFERENCING    = 4,

};

// Seconds since Jan 1, 2000 0:00:00 (UTC)

#define VHD_TIMESTAMP_BASE 946684800

// always big-endian

struct vhd_footer {

    char        creator[8]; // "conectix"

    uint32_t    features;

    uint32_t    version;

    // Offset of next header structure, 0xFFFFFFFF if none

    uint64_t    data_offset;

    // Seconds since Jan 1, 2000 0:00:00 (UTC)

    uint32_t    timestamp;

    char        creator_app[4]; // "vpc "

    uint16_t    major;

    uint16_t    minor;

    char        creator_os[4]; // "Wi2k"

    uint64_t    orig_size;

    uint64_t    size;

    uint16_t    cyls;

    uint8_t     heads;

    uint8_t     secs_per_cyl;

    uint32_t    type;

    // Checksum of the Hard Disk Footer ("one's complement of the sum of all

    // the bytes in the footer without the checksum field")

    uint32_t    checksum;

    // UUID used to identify a parent hard disk (backing file)

    uint8_t     uuid[16];

    uint8_t     in_saved_state;

};

struct vhd_dyndisk_header {

    char        magic[8]; // "cxsparse"

    // Offset of next header structure, 0xFFFFFFFF if none

    uint64_t    data_offset;

    // Offset of the Block Allocation Table (BAT)

    uint64_t    table_offset;

    uint32_t    version;

    uint32_t    max_table_entries; // 32bit/entry

    // 2 MB by default, must be a power of two

    uint32_t    block_size;

    uint32_t    checksum;

    uint8_t     parent_uuid[16];

    uint32_t    parent_timestamp;

    uint32_t    reserved;

    // Backing file name (in UTF-16)

    uint8_t     parent_name[512];

    struct {

        uint32_t    platform;

        uint32_t    data_space;

        uint32_t    data_length;

        uint32_t    reserved;

        uint64_t    data_offset;

    } parent_locator[8];

};

typedef struct BDRVVPCState {

    BlockDriverState *hd;

    uint8_t footer_buf[HEADER_SIZE];

    uint64_t free_data_block_offset;

    int max_table_entries;

    uint32_t *pagetable;

    uint64_t bat_offset;

    uint64_t last_bitmap_offset;

    uint32_t block_size;

    uint32_t bitmap_size;

#ifdef CACHE

    uint8_t *pageentry_u8;

    uint32_t *pageentry_u32;

    uint16_t *pageentry_u16;

    uint64_t last_bitmap;

#endif

} BDRVVPCState;

static uint32_t vpc_checksum(uint8_t* buf, size_t size)

{

    uint32_t res = 0;

    int i;

    for (i = 0; i < size; i++)

        res += buf[i];

    return ~res;

}

static int vpc_probe(const uint8_t *buf, int buf_size, const char *filename)

{

    if (buf_size >= 8 && !strncmp((char *)buf, "conectix", 8))

        return 100;

    return 0;

}

static int vpc_open(BlockDriverState *bs, const char *filename, int flags)

{

    BDRVVPCState *s = bs->opaque;

    int ret, i;

    struct vhd_footer* footer;

    struct vhd_dyndisk_header* dyndisk_header;

    uint8_t buf[HEADER_SIZE];

    uint32_t checksum;

    ret = bdrv_file_open(&s->hd, filename, flags);

    if (ret < 0)

        return ret;

    if (bdrv_pread(s->hd, 0, s->footer_buf, HEADER_SIZE) != HEADER_SIZE)

        goto fail;

    footer = (struct vhd_footer*) s->footer_buf;

    if (strncmp(footer->creator, "conectix", 8))

        goto fail;

    checksum = be32_to_cpu(footer->checksum);

    footer->checksum = 0;

    if (vpc_checksum(s->footer_buf, HEADER_SIZE) != checksum)

        fprintf(stderr, "block-vpc: The header checksum of '%s' is "

            "incorrect.\n", filename);

    // The visible size of a image in Virtual PC depends on the geometry

    // rather than on the size stored in the footer (the size in the footer

    // is too large usually)

    bs->total_sectors = (int64_t)

        be16_to_cpu(footer->cyls) * footer->heads * footer->secs_per_cyl;

    if (bdrv_pread(s->hd, be64_to_cpu(footer->data_offset), buf, HEADER_SIZE)

            != HEADER_SIZE)

        goto fail;

    dyndisk_header = (struct vhd_dyndisk_header*) buf;

    if (strncmp(dyndisk_header->magic, "cxsparse", 8))

        goto fail;

    s->block_size = be32_to_cpu(dyndisk_header->block_size);

    s->bitmap_size = ((s->block_size / (8 * 512)) + 511) & ~511;

    s->max_table_entries = be32_to_cpu(dyndisk_header->max_table_entries);

    s->pagetable = qemu_malloc(s->max_table_entries * 4);

    s->bat_offset = be64_to_cpu(dyndisk_header->table_offset);

    if (bdrv_pread(s->hd, s->bat_offset, s->pagetable,

            s->max_table_entries * 4) != s->max_table_entries * 4)

            goto fail;

    s->free_data_block_offset =

        (s->bat_offset + (s->max_table_entries * 4) + 511) & ~511;

    for (i = 0; i < s->max_table_entries; i++) {

        be32_to_cpus(&s->pagetable[i]);

        if (s->pagetable[i] != 0xFFFFFFFF) {

            int64_t next = (512 * (int64_t) s->pagetable[i]) +

                s->bitmap_size + s->block_size;

            if (next> s->free_data_block_offset)

                s->free_data_block_offset = next;

        }

    }

    s->last_bitmap_offset = (int64_t) -1;

#ifdef CACHE

    s->pageentry_u8 = qemu_malloc(512);

    s->pageentry_u32 = s->pageentry_u8;

    s->pageentry_u16 = s->pageentry_u8;

    s->last_pagetable = -1;

#endif

    return 0;

 fail:

    bdrv_delete(s->hd);

    return -1;

}

/*

 * Returns the absolute byte offset of the given sector in the image file.

 * If the sector is not allocated, -1 is returned instead.

 *

 * The parameter write must be 1 if the offset will be used for a write

 * operation (the block bitmaps is updated then), 0 otherwise.

 */

static inline int64_t get_sector_offset(BlockDriverState *bs,

    int64_t sector_num, int write)

{

    BDRVVPCState *s = bs->opaque;

    uint64_t offset = sector_num * 512;

    uint64_t bitmap_offset, block_offset;

    uint32_t pagetable_index, pageentry_index;

    pagetable_index = offset / s->block_size;

    pageentry_index = (offset % s->block_size) / 512;

    if (pagetable_index >= s->max_table_entries || s->pagetable[pagetable_index] == 0xffffffff)

        return -1; // not allocated

    bitmap_offset = 512 * (uint64_t) s->pagetable[pagetable_index];

    block_offset = bitmap_offset + s->bitmap_size + (512 * pageentry_index);

    // We must ensure that we don't write to any sectors which are marked as

    // unused in the bitmap. We get away with setting all bits in the block

    // bitmap each time we write to a new block. This might cause Virtual PC to

    // miss sparse read optimization, but it's not a problem in terms of

    // correctness.

    if (write && (s->last_bitmap_offset != bitmap_offset)) {

        uint8_t bitmap[s->bitmap_size];

        s->last_bitmap_offset = bitmap_offset;

        memset(bitmap, 0xff, s->bitmap_size);

        bdrv_pwrite(s->hd, bitmap_offset, bitmap, s->bitmap_size);

    }

//    printf("sector: %" PRIx64 ", index: %x, offset: %x, bioff: %" PRIx64 ", bloff: %" PRIx64 "\n",

//        sector_num, pagetable_index, pageentry_index,

//        bitmap_offset, block_offset);

// disabled by reason

#if 0

#ifdef CACHE

    if (bitmap_offset != s->last_bitmap)

    {

        lseek(s->fd, bitmap_offset, SEEK_SET);

        s->last_bitmap = bitmap_offset;

        // Scary! Bitmap is stored as big endian 32bit entries,

        // while we used to look it up byte by byte

        read(s->fd, s->pageentry_u8, 512);

        for (i = 0; i < 128; i++)

            be32_to_cpus(&s->pageentry_u32[i]);

    }

    if ((s->pageentry_u8[pageentry_index / 8] >> (pageentry_index % 8)) & 1)

        return -1;

#else

    lseek(s->fd, bitmap_offset + (pageentry_index / 8), SEEK_SET);

    read(s->fd, &bitmap_entry, 1);

    if ((bitmap_entry >> (pageentry_index % 8)) & 1)

        return -1; // not allocated

#endif

#endif

    return block_offset;

}

/*

 * Writes the footer to the end of the image file. This is needed when the

 * file grows as it overwrites the old footer

 *

 * Returns 0 on success and < 0 on error

 */

static int rewrite_footer(BlockDriverState* bs)

{

    int ret;

    BDRVVPCState *s = bs->opaque;

    int64_t offset = s->free_data_block_offset;

    ret = bdrv_pwrite(s->hd, offset, s->footer_buf, HEADER_SIZE);

    if (ret < 0)

        return ret;

    return 0;

}

/*

 * Allocates a new block. This involves writing a new footer and updating

 * the Block Allocation Table to use the space at the old end of the image

 * file (overwriting the old footer)

 *

 * Returns the sectors' offset in the image file on success and < 0 on error

 */

static int64_t alloc_block(BlockDriverState* bs, int64_t sector_num)

{

    BDRVVPCState *s = bs->opaque;

    int64_t bat_offset;

    uint32_t index, bat_value;

    int ret;

    uint8_t bitmap[s->bitmap_size];

    // Check if sector_num is valid

    if ((sector_num < 0) || (sector_num > bs->total_sectors))

        return -1;

    // Write entry into in-memory BAT

    index = (sector_num * 512) / s->block_size;

    if (s->pagetable[index] != 0xFFFFFFFF)

        return -1;

    s->pagetable[index] = s->free_data_block_offset / 512;

    // Initialize the block's bitmap

    memset(bitmap, 0xff, s->bitmap_size);

    bdrv_pwrite(s->hd, s->free_data_block_offset, bitmap, s->bitmap_size);

    // Write new footer (the old one will be overwritten)

    s->free_data_block_offset += s->block_size + s->bitmap_size;

    ret = rewrite_footer(bs);

    if (ret < 0)

        goto fail;

    // Write BAT entry to disk

    bat_offset = s->bat_offset + (4 * index);

    bat_value = be32_to_cpu(s->pagetable[index]);

    ret = bdrv_pwrite(s->hd, bat_offset, &bat_value, 4);

    if (ret < 0)

        goto fail;

    return get_sector_offset(bs, sector_num, 0);

fail:

    s->free_data_block_offset -= (s->block_size + s->bitmap_size);

    return -1;

}

static int vpc_read(BlockDriverState *bs, int64_t sector_num,

                    uint8_t *buf, int nb_sectors)

{

    BDRVVPCState *s = bs->opaque;

    int ret;

    int64_t offset;

    while (nb_sectors > 0) {

        offset = get_sector_offset(bs, sector_num, 0);

        if (offset == -1) {

            memset(buf, 0, 512);

        } else {

            ret = bdrv_pread(s->hd, offset, buf, 512);

            if (ret != 512)

                return -1;

        }

        nb_sectors--;

        sector_num++;

        buf += 512;

    }

    return 0;

}

static int vpc_write(BlockDriverState *bs, int64_t sector_num,

    const uint8_t *buf, int nb_sectors)

{

    BDRVVPCState *s = bs->opaque;

    int64_t offset;

    int ret;

    while (nb_sectors > 0) {

        offset = get_sector_offset(bs, sector_num, 1);

        if (offset == -1) {

            offset = alloc_block(bs, sector_num);

            if (offset < 0)

                return -1;

        }

        ret = bdrv_pwrite(s->hd, offset, buf, 512);

        if (ret != 512)

            return -1;

        nb_sectors--;

        sector_num++;

        buf += 512;

    }

    return 0;

}

/*

 * Calculates the number of cylinders, heads and sectors per cylinder

 * based on a given number of sectors. This is the algorithm described

 * in the VHD specification.

 *

 * Note that the geometry doesn't always exactly match total_sectors but

 * may round it down.

 */

static void calculate_geometry(int64_t total_sectors, uint16_t* cyls,

    uint8_t* heads, uint8_t* secs_per_cyl)

{

    uint32_t cyls_times_heads;

    if (total_sectors > 65535 * 16 * 255)

        total_sectors = 65535 * 16 * 255;

    if (total_sectors > 65535 * 16 * 63) {

        *secs_per_cyl = 255;

        *heads = 16;

        cyls_times_heads = total_sectors / *secs_per_cyl;

    } else {

        *secs_per_cyl = 17;

        cyls_times_heads = total_sectors / *secs_per_cyl;

        *heads = (cyls_times_heads + 1023) / 1024;

        if (*heads < 4)

            *heads = 4;

        if (cyls_times_heads >= (*heads * 1024) || *heads > 16) {

            *secs_per_cyl = 31;

            *heads = 16;

            cyls_times_heads = total_sectors / *secs_per_cyl;

        }

        if (cyls_times_heads >= (*heads * 1024)) {

            *secs_per_cyl = 63;

            *heads = 16;

            cyls_times_heads = total_sectors / *secs_per_cyl;

        }

    }

    // Note: Rounding up deviates from the Virtual PC behaviour

    // However, we need this to avoid truncating images in qemu-img convert

    *cyls = (cyls_times_heads + *heads - 1) / *heads;

}

static int vpc_create(const char *filename, int64_t total_sectors,

    const char *backing_file, int flags)

{

    uint8_t buf[1024];

    struct vhd_footer* footer = (struct vhd_footer*) buf;

    struct vhd_dyndisk_header* dyndisk_header =

        (struct vhd_dyndisk_header*) buf;

    int fd, i;

    uint16_t cyls;

    uint8_t heads;

    uint8_t secs_per_cyl;

    size_t block_size, num_bat_entries;

    if (backing_file != NULL)

        return -ENOTSUP;

    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);

    if (fd < 0)

        return -EIO;

    // Calculate matching total_size and geometry

    calculate_geometry(total_sectors, &cyls, &heads, &secs_per_cyl);

    total_sectors = (int64_t) cyls * heads * secs_per_cyl;

    // Prepare the Hard Disk Footer

    memset(buf, 0, 1024);

    strncpy(footer->creator, "conectix", 8);

    // TODO Check if "qemu" creator_app is ok for VPC

    strncpy(footer->creator_app, "qemu", 4);

    strncpy(footer->creator_os, "Wi2k", 4);

    footer->features = be32_to_cpu(0x02);

    footer->version = be32_to_cpu(0x00010000);

    footer->data_offset = be64_to_cpu(HEADER_SIZE);

    footer->timestamp = be32_to_cpu(time(NULL) - VHD_TIMESTAMP_BASE);

    // Version of Virtual PC 2007

    footer->major = be16_to_cpu(0x0005);

    footer->minor =be16_to_cpu(0x0003);

    footer->orig_size = be64_to_cpu(total_sectors * 512);

    footer->size = be64_to_cpu(total_sectors * 512);

    footer->cyls = be16_to_cpu(cyls);

    footer->heads = heads;

    footer->secs_per_cyl = secs_per_cyl;

    footer->type = be32_to_cpu(VHD_DYNAMIC);

    // TODO uuid is missing

    footer->checksum = be32_to_cpu(vpc_checksum(buf, HEADER_SIZE));

    // Write the footer (twice: at the beginning and at the end)

    block_size = 0x200000;

    num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);

    if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE)

        return -EIO;

    if (lseek(fd, 1536 + ((num_bat_entries * 4 + 511) & ~511), SEEK_SET) < 0)

        return -EIO;

    if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE)

        return -EIO;

    // Write the initial BAT

    if (lseek(fd, 3 * 512, SEEK_SET) < 0)

        return -EIO;

    memset(buf, 0xFF, 512);

    for (i = 0; i < (num_bat_entries * 4 + 511) / 512; i++)

        if (write(fd, buf, 512) != 512)

            return -EIO;

    // Prepare the Dynamic Disk Header

    memset(buf, 0, 1024);

    strncpy(dyndisk_header->magic, "cxsparse", 8);

    dyndisk_header->data_offset = be64_to_cpu(0xFFFFFFFF);

    dyndisk_header->table_offset = be64_to_cpu(3 * 512);

    dyndisk_header->version = be32_to_cpu(0x00010000);

    dyndisk_header->block_size = be32_to_cpu(block_size);

    dyndisk_header->max_table_entries = be32_to_cpu(num_bat_entries);

    dyndisk_header->checksum = be32_to_cpu(vpc_checksum(buf, 1024));

    // Write the header

    if (lseek(fd, 512, SEEK_SET) < 0)

        return -EIO;

    if (write(fd, buf, 1024) != 1024)

        return -EIO;

    close(fd);

    return 0;

}

static void vpc_close(BlockDriverState *bs)

{

    BDRVVPCState *s = bs->opaque;

    qemu_free(s->pagetable);

#ifdef CACHE

    qemu_free(s->pageentry_u8);

#endif

    bdrv_delete(s->hd);

}

BlockDriver bdrv_vpc = {

    .format_name        = "vpc",

    .instance_size        = sizeof(BDRVVPCState),

    .bdrv_probe                = vpc_probe,

    .bdrv_open                = vpc_open,

    .bdrv_read                = vpc_read,

    .bdrv_write                = vpc_write,

    .bdrv_close                = vpc_close,

    .bdrv_create        = vpc_create,

};