1 /* 2 * qcow2.c --- Functions to generate qcow2 formatted disk images. This 3 * format is used originally by QEMU for virtual machines, and stores the 4 * filesystem data on disk in a packed format to avoid creating sparse 5 * image files that need lots of seeking to read and write. 6 * 7 * The qcow2 format supports zlib compression, but that is not yet 8 * implemented. 9 * 10 * It is possible to directly mount a qcow2 image using qemu-nbd: 11 * 12 * [root]# modprobe nbd max_part=63 13 * [root]# qemu-nbd -c /dev/nbd0 image.img 14 * [root]# mount /dev/nbd0p1 /mnt/qemu 15 * 16 * Format details at http://people.gnome.org/~markmc/qcow-image-format.html 17 * 18 * Copyright (C) 2010 Red Hat, Inc., Lukas Czerner <lczerner (at) redhat.com> 19 * 20 * %Begin-Header% 21 * This file may be redistributed under the terms of the GNU Public 22 * License. 23 * %End-Header% 24 */ 25 26 #define _LARGEFILE_SOURCE 27 #define _LARGEFILE64_SOURCE 28 29 #include <fcntl.h> 30 #include <grp.h> 31 #include <pwd.h> 32 #include <stdio.h> 33 #ifdef HAVE_STDLIB_H 34 #include <stdlib.h> 35 #endif 36 #include <string.h> 37 #include <time.h> 38 #include <unistd.h> 39 #include <fcntl.h> 40 #include <errno.h> 41 #include <sys/stat.h> 42 #include <sys/types.h> 43 #include <assert.h> 44 45 #include "ext2fs/ext2fs.h" 46 #include "qcow2.h" 47 48 /* Functions for converting qcow2 image into raw image */ 49 50 struct ext2_qcow2_hdr *qcow2_read_header(int fd) 51 { 52 void *buffer = NULL; 53 struct ext2_qcow2_hdr *hdr = NULL; 54 size_t size; 55 errcode_t ret; 56 57 ret = ext2fs_get_mem(sizeof(struct ext2_qcow2_hdr), &buffer); 58 if (ret) 59 return NULL; 60 memset(buffer, 0, sizeof(struct ext2_qcow2_hdr)); 61 62 if (ext2fs_llseek(fd, 0, SEEK_SET < 0)) { 63 ext2fs_free_mem(&buffer); 64 return NULL; 65 } 66 67 size = read(fd, buffer, sizeof(struct ext2_qcow2_hdr)); 68 if (size != sizeof(struct ext2_qcow2_hdr)) { 69 ext2fs_free_mem(&buffer); 70 return NULL; 71 } 72 73 hdr = (struct ext2_qcow2_hdr *)(buffer); 74 75 if ((ext2fs_be32_to_cpu(hdr->magic) != QCOW_MAGIC) || 76 (ext2fs_be32_to_cpu(hdr->version) != 2)) { 77 ext2fs_free_mem(&hdr); 78 return NULL; 79 } 80 81 return hdr; 82 } 83 84 static int qcow2_read_l1_table(struct ext2_qcow2_image *img) 85 { 86 int fd = img->fd; 87 size_t size, l1_size = img->l1_size * sizeof(blk64_t); 88 blk64_t *table; 89 errcode_t ret; 90 91 ret = ext2fs_get_memzero(l1_size, &table); 92 if (ret) 93 return ret; 94 95 if (ext2fs_llseek(fd, img->l1_offset, SEEK_SET) < 0) { 96 ext2fs_free_mem(&table); 97 return errno; 98 } 99 100 size = read(fd, table, l1_size); 101 if (size != l1_size) { 102 ext2fs_free_mem(&table); 103 return errno; 104 } 105 106 img->l1_table = table; 107 108 return 0; 109 } 110 111 static int qcow2_read_l2_table(struct ext2_qcow2_image *img, 112 ext2_off64_t offset, blk64_t **l2_table) 113 { 114 int fd = img->fd; 115 size_t size; 116 117 assert(*l2_table); 118 119 if (ext2fs_llseek(fd, offset, SEEK_SET) < 0) 120 return errno; 121 122 size = read(fd, *l2_table, img->cluster_size); 123 if (size != img->cluster_size) 124 return errno; 125 126 return 0; 127 } 128 129 static int qcow2_copy_data(int fdin, int fdout, ext2_off64_t off_in, 130 ext2_off64_t off_out, void *buf, size_t count) 131 { 132 size_t size; 133 134 assert(buf); 135 136 if (ext2fs_llseek(fdout, off_out, SEEK_SET) < 0) 137 return errno; 138 139 if (ext2fs_llseek(fdin, off_in, SEEK_SET) < 0) 140 return errno; 141 142 size = read(fdin, buf, count); 143 if (size != count) 144 return errno; 145 146 size = write(fdout, buf, count); 147 if (size != count) 148 return errno; 149 150 return 0; 151 } 152 153 154 int qcow2_write_raw_image(int qcow2_fd, int raw_fd, 155 struct ext2_qcow2_hdr *hdr) 156 { 157 struct ext2_qcow2_image img; 158 errcode_t ret = 0; 159 unsigned int l1_index, l2_index; 160 ext2_off64_t offset; 161 blk64_t *l1_table, *l2_table = NULL; 162 void *copy_buf = NULL; 163 size_t size; 164 165 if (hdr->crypt_method) 166 return -QCOW_ENCRYPTED; 167 168 img.fd = qcow2_fd; 169 img.hdr = hdr; 170 img.l2_cache = NULL; 171 img.l1_table = NULL; 172 img.cluster_bits = ext2fs_be32_to_cpu(hdr->cluster_bits); 173 img.cluster_size = 1 << img.cluster_bits; 174 img.l1_size = ext2fs_be32_to_cpu(hdr->l1_size); 175 img.l1_offset = ext2fs_be64_to_cpu(hdr->l1_table_offset); 176 img.l2_size = 1 << (img.cluster_bits - 3); 177 img.image_size = ext2fs_be64_to_cpu(hdr->size); 178 179 180 ret = ext2fs_get_memzero(img.cluster_size, &l2_table); 181 if (ret) 182 goto out; 183 184 ret = ext2fs_get_memzero(1 << img.cluster_bits, ©_buf); 185 if (ret) 186 goto out; 187 188 if (ext2fs_llseek(raw_fd, 0, SEEK_SET) < 0) { 189 ret = errno; 190 goto out; 191 } 192 193 ret = qcow2_read_l1_table(&img); 194 if (ret) 195 goto out; 196 197 l1_table = img.l1_table; 198 /* Walk through l1 table */ 199 for (l1_index = 0; l1_index < img.l1_size; l1_index++) { 200 ext2_off64_t off_out; 201 202 offset = ext2fs_be64_to_cpu(l1_table[l1_index]) & 203 ~QCOW_OFLAG_COPIED; 204 205 if ((offset > img.image_size) || 206 (offset <= 0)) 207 continue; 208 209 if (offset & QCOW_OFLAG_COMPRESSED) { 210 ret = -QCOW_COMPRESSED; 211 goto out; 212 } 213 214 ret = qcow2_read_l2_table(&img, offset, &l2_table); 215 if (ret) 216 break; 217 218 /* Walk through l2 table and copy data blocks into raw image */ 219 for (l2_index = 0; l2_index < img.l2_size; l2_index++) { 220 offset = ext2fs_be64_to_cpu(l2_table[l2_index]) & 221 ~QCOW_OFLAG_COPIED; 222 223 if (offset == 0) 224 continue; 225 226 off_out = (l1_index * img.l2_size) + 227 l2_index; 228 off_out <<= img.cluster_bits; 229 ret = qcow2_copy_data(qcow2_fd, raw_fd, offset, 230 off_out, copy_buf, img.cluster_size); 231 if (ret) 232 goto out; 233 } 234 } 235 236 /* Resize the output image to the filesystem size */ 237 if (ext2fs_llseek(raw_fd, img.image_size - 1, SEEK_SET) < 0) 238 return errno; 239 240 ((char *)copy_buf)[0] = 0; 241 size = write(raw_fd, copy_buf, 1); 242 if (size != 1) { 243 ret = errno; 244 goto out; 245 } 246 247 out: 248 if (copy_buf) 249 ext2fs_free_mem(©_buf); 250 if (img.l1_table) 251 ext2fs_free_mem(&img.l1_table); 252 if (l2_table) 253 ext2fs_free_mem(&l2_table); 254 return ret; 255 } 256
