Archipelago » qemu

/*

 * QEMU System Emulator block driver

 * 

 * Copyright (c) 2003 Fabrice Bellard

 * 

 * 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 <stdlib.h>

#include <stdio.h>

#include <stdarg.h>

#include <string.h>

#include <getopt.h>

#include <inttypes.h>

#include <unistd.h>

#include <sys/mman.h>

#include <fcntl.h>

#include <signal.h>

#include <time.h>

#include <sys/time.h>

#include <malloc.h>

#include <termios.h>

#include <sys/poll.h>

#include <errno.h>

#include <sys/wait.h>

#include <netinet/in.h>

#include "vl.h"

#define NO_THUNK_TYPE_SIZE

#include "thunk.h"

struct BlockDriverState {

    int fd; /* if -1, only COW mappings */

    int64_t total_sectors;

    int read_only;

    uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */

    uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */

    int cow_bitmap_size;

    int cow_fd;

    int64_t cow_sectors_offset;

    char filename[1024];

};

BlockDriverState *bdrv_open(const char *filename, int snapshot)

{

    BlockDriverState *bs;

    int fd, cow_fd;

    int64_t size;

    char template[] = "/tmp/vl.XXXXXX";

    struct cow_header_v2 cow_header;

    struct stat st;

    bs = malloc(sizeof(BlockDriverState));

    if(!bs)

        return NULL;

    bs->read_only = 0;

    bs->fd = -1;

    bs->cow_fd = -1;

    bs->cow_bitmap = NULL;

    strcpy(bs->filename, filename);

    /* open standard HD image */

    fd = open(filename, O_RDWR | O_LARGEFILE);

    if (fd < 0) {

        /* read only image on disk */

        fd = open(filename, O_RDONLY | O_LARGEFILE);

        if (fd < 0) {

            perror(filename);

            goto fail;

        }

        if (!snapshot)

            bs->read_only = 1;

    }

    bs->fd = fd;

    /* see if it is a cow image */

    if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {

        fprintf(stderr, "%s: could not read header\n", filename);

        goto fail;

    }

    if (cow_header.magic == htonl(COW_MAGIC) &&

        cow_header.version == htonl(COW_VERSION)) {

        /* cow image found */

        size = cow_header.size;

#ifndef WORDS_BIGENDIAN

        size = bswap64(size);

#endif    

        bs->total_sectors = size / 512;

        bs->cow_fd = fd;

        bs->fd = -1;

        if (cow_header.backing_file[0] != '\0') {

            if (stat(cow_header.backing_file, &st) != 0) {

                fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);

                goto fail;

            }

            if (st.st_mtime != htonl(cow_header.mtime)) {

                fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);

                goto fail;

            }

            fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);

            if (fd < 0)

                goto fail;

            bs->fd = fd;

        }

        /* mmap the bitmap */

        bs->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);

        bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size), 

                                   bs->cow_bitmap_size, 

                                   PROT_READ | PROT_WRITE,

                                   MAP_SHARED, bs->cow_fd, 0);

        if (bs->cow_bitmap_addr == MAP_FAILED)

            goto fail;

        bs->cow_bitmap = bs->cow_bitmap_addr + sizeof(cow_header);

        bs->cow_sectors_offset = (bs->cow_bitmap_size + 511) & ~511;

        snapshot = 0;

    } else {

        /* standard raw image */

        size = lseek64(fd, 0, SEEK_END);

        bs->total_sectors = size / 512;

        bs->fd = fd;

    }

    if (snapshot) {

        /* create a temporary COW file */

        cow_fd = mkstemp(template);

        if (cow_fd < 0)

            goto fail;

        bs->cow_fd = cow_fd;

        unlink(template);

        /* just need to allocate bitmap */

        bs->cow_bitmap_size = (bs->total_sectors + 7) >> 3;

        bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size), 

                                   bs->cow_bitmap_size, 

                                   PROT_READ | PROT_WRITE,

                                   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

        if (bs->cow_bitmap_addr == MAP_FAILED)

            goto fail;

        bs->cow_bitmap = bs->cow_bitmap_addr;

        bs->cow_sectors_offset = 0;

    }

    return bs;

 fail:

    bdrv_close(bs);

    return NULL;

}

void bdrv_close(BlockDriverState *bs)

{

    /* we unmap the mapping so that it is written to the COW file */

    if (bs->cow_bitmap_addr)

        munmap(bs->cow_bitmap_addr, bs->cow_bitmap_size);

    if (bs->cow_fd >= 0)

        close(bs->cow_fd);

    if (bs->fd >= 0)

        close(bs->fd);

    free(bs);

}

static inline void set_bit(uint8_t *bitmap, int64_t bitnum)

{

    bitmap[bitnum / 8] |= (1 << (bitnum%8));

}

static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)

{

    return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));

}

/* Return true if first block has been changed (ie. current version is

 * in COW file).  Set the number of continuous blocks for which that

 * is true. */

static int is_changed(uint8_t *bitmap,

                      int64_t sector_num, int nb_sectors,

                      int *num_same)

{

    int changed;

    if (!bitmap || nb_sectors == 0) {

        *num_same = nb_sectors;

        return 0;

    }

    changed = is_bit_set(bitmap, sector_num);

    for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {

        if (is_bit_set(bitmap, sector_num + *num_same) != changed)

            break;

    }

    return changed;

}

/* commit COW file into the raw image */

int bdrv_commit(BlockDriverState *bs)

{

    int64_t i;

    uint8_t *cow_bitmap;

    if (!bs->cow_bitmap) {

        fprintf(stderr, "Already committed to %s\n", bs->filename);

        return 0;

    }

    if (bs->read_only) {

        fprintf(stderr, "Can't commit to %s: read-only\n", bs->filename);

        return -1;

    }

    cow_bitmap = bs->cow_bitmap;

    for (i = 0; i < bs->total_sectors; i++) {

        if (is_bit_set(cow_bitmap, i)) {

            unsigned char sector[512];

            if (bdrv_read(bs, i, sector, 1) != 0) {

                fprintf(stderr, "Error reading sector %lli: aborting commit\n",

                        (long long)i);

                return -1;

            }

            /* Make bdrv_write write to real file for a moment. */

            bs->cow_bitmap = NULL;

            if (bdrv_write(bs, i, sector, 1) != 0) {

                fprintf(stderr, "Error writing sector %lli: aborting commit\n",

                        (long long)i);

                bs->cow_bitmap = cow_bitmap;

                return -1;

            }

            bs->cow_bitmap = cow_bitmap;

        }

    }

    fprintf(stderr, "Committed snapshot to %s\n", bs->filename);

    return 0;

}

/* return -1 if error */

int bdrv_read(BlockDriverState *bs, int64_t sector_num, 

              uint8_t *buf, int nb_sectors)

{

    int ret, n, fd;

    int64_t offset;

    while (nb_sectors > 0) {

        if (is_changed(bs->cow_bitmap, sector_num, nb_sectors, &n)) {

            fd = bs->cow_fd;

            offset = bs->cow_sectors_offset;

        } else {

            fd = bs->fd;

            offset = 0;

        }

        if (fd < 0) {

            /* no file, just return empty sectors */

            memset(buf, 0, n * 512);

        } else {

            offset += sector_num * 512;

            lseek64(fd, offset, SEEK_SET);

            ret = read(fd, buf, n * 512);

            if (ret != n * 512) {

                return -1;

            }

        }

        nb_sectors -= n;

        sector_num += n;

        buf += n * 512;

    }

    return 0;

}

/* return -1 if error */

int bdrv_write(BlockDriverState *bs, int64_t sector_num, 

               const uint8_t *buf, int nb_sectors)

{

    int ret, fd, i;

    int64_t offset, retl;

    if (bs->read_only)

        return -1;

    if (bs->cow_bitmap) {

        fd = bs->cow_fd;

        offset = bs->cow_sectors_offset;

    } else {

        fd = bs->fd;

        offset = 0;

    }

    offset += sector_num * 512;

    retl = lseek64(fd, offset, SEEK_SET);

    if (retl == -1) {

        return -1;

    }

    ret = write(fd, buf, nb_sectors * 512);

    if (ret != nb_sectors * 512) {

        return -1;

    }

    if (bs->cow_bitmap) {

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

            set_bit(bs->cow_bitmap, sector_num + i);

    }

    return 0;

}

void bdrv_get_geometry(BlockDriverState *bs, int64_t *nb_sectors_ptr)

{

    *nb_sectors_ptr = bs->total_sectors;

}