srs5694 | e7b4ff9 | 2009-08-18 13:16:10 -0400 | [diff] [blame] | 1 | /* mbr.cc -- Functions for loading, saving, and manipulating legacy MBR partition |
| 2 | data. */ |
| 3 | |
| 4 | /* By Rod Smith, January to February, 2009 */ |
| 5 | |
| 6 | #define __STDC_LIMIT_MACROS |
| 7 | #define __STDC_CONSTANT_MACROS |
| 8 | |
| 9 | #include <stdio.h> |
| 10 | #include <unistd.h> |
| 11 | #include <stdlib.h> |
| 12 | #include <stdint.h> |
| 13 | #include <fcntl.h> |
| 14 | #include <string.h> |
| 15 | #include <time.h> |
| 16 | #include <sys/stat.h> |
| 17 | #include <errno.h> |
| 18 | #include "mbr.h" |
| 19 | #include "support.h" |
| 20 | |
| 21 | using namespace std; |
| 22 | |
| 23 | /**************************************** |
| 24 | * * |
| 25 | * MBRData class and related structures * |
| 26 | * * |
| 27 | ****************************************/ |
| 28 | |
| 29 | MBRData::MBRData(void) { |
| 30 | blockSize = SECTOR_SIZE; |
| 31 | diskSize = 0; |
| 32 | strcpy(device, ""); |
| 33 | state = invalid; |
| 34 | srand((unsigned int) time(NULL)); |
| 35 | EmptyMBR(); |
| 36 | } // MBRData default constructor |
| 37 | |
| 38 | MBRData::MBRData(char *filename) { |
| 39 | blockSize = SECTOR_SIZE; |
| 40 | diskSize = 0; |
| 41 | strcpy(device, filename); |
| 42 | state = invalid; |
| 43 | |
| 44 | srand((unsigned int) time(NULL)); |
| 45 | // Try to read the specified partition table, but if it fails.... |
| 46 | if (!ReadMBRData(filename)) { |
| 47 | EmptyMBR(); |
| 48 | strcpy(device, ""); |
| 49 | } // if |
| 50 | } // MBRData(char *filename) constructor |
| 51 | |
| 52 | MBRData::~MBRData(void) { |
| 53 | } // MBRData destructor |
| 54 | |
| 55 | // Empty all data. Meant mainly for calling by constructors |
| 56 | void MBRData::EmptyMBR(void) { |
| 57 | int i; |
| 58 | |
| 59 | for (i = 0; i < 440; i++) |
| 60 | code[i] = 0; |
| 61 | diskSignature = (uint32_t) rand(); |
| 62 | nulls = 0; |
| 63 | for (i = 0; i < 4; i++) { |
| 64 | partitions[i].status = UINT8_C(0); |
| 65 | partitions[i].firstSector[0] = UINT8_C(0); |
| 66 | partitions[i].firstSector[1] = UINT8_C(0); |
| 67 | partitions[i].firstSector[2] = UINT8_C(0); |
| 68 | partitions[i].partitionType = UINT8_C(0); |
| 69 | partitions[i].lastSector[0] = UINT8_C(0); |
| 70 | partitions[i].lastSector[1] = UINT8_C(0); |
| 71 | partitions[i].lastSector[2] = UINT8_C(0); |
| 72 | partitions[i].firstLBA = UINT32_C(0); |
| 73 | partitions[i].lengthLBA = UINT32_C(0); |
| 74 | } // for |
| 75 | MBRSignature = MBR_SIGNATURE; |
| 76 | |
| 77 | blockSize = SECTOR_SIZE; |
| 78 | diskSize = 0; |
| 79 | for (i = 0; i < NUM_LOGICALS; i++) { |
| 80 | logicals[i].status = UINT8_C(0); |
| 81 | logicals[i].firstSector[0] = UINT8_C(0); |
| 82 | logicals[i].firstSector[1] = UINT8_C(0); |
| 83 | logicals[i].firstSector[2] = UINT8_C(0); |
| 84 | logicals[i].partitionType = UINT8_C(0); |
| 85 | logicals[i].lastSector[0] = UINT8_C(0); |
| 86 | logicals[i].lastSector[1] = UINT8_C(0); |
| 87 | logicals[i].lastSector[2] = UINT8_C(0); |
| 88 | logicals[i].firstLBA = UINT32_C(0); |
| 89 | logicals[i].lengthLBA = UINT32_C(0); |
| 90 | } // for |
| 91 | } // MBRData::EmptyMBR() |
| 92 | |
| 93 | // Read data from MBR. Returns 1 if read was successful (even if the |
| 94 | // data isn't a valid MBR), 0 if the read failed. |
| 95 | int MBRData::ReadMBRData(char* deviceFilename) { |
| 96 | int fd, allOK = 1; |
| 97 | |
| 98 | if ((fd = open(deviceFilename, O_RDONLY)) != -1) { |
| 99 | ReadMBRData(fd); |
| 100 | } else { |
| 101 | allOK = 0; |
| 102 | } // if |
| 103 | |
| 104 | close(fd); |
| 105 | |
| 106 | if (allOK) |
| 107 | strcpy(device, deviceFilename); |
| 108 | |
| 109 | return allOK; |
| 110 | } // MBRData::ReadMBRData(char* deviceFilename) |
| 111 | |
| 112 | // Read data from MBR. |
| 113 | void MBRData::ReadMBRData(int fd) { |
| 114 | int allOK = 1, i; |
| 115 | int err; |
| 116 | |
| 117 | // Clear logical partition array |
| 118 | for (i = 0; i < NUM_LOGICALS; i++) { |
| 119 | logicals[i].status = UINT8_C(0); |
| 120 | logicals[i].firstSector[0] = UINT8_C(0); |
| 121 | logicals[i].firstSector[1] = UINT8_C(0); |
| 122 | logicals[i].firstSector[2] = UINT8_C(0); |
| 123 | logicals[i].partitionType = UINT8_C(0); |
| 124 | logicals[i].lastSector[0] = UINT8_C(0); |
| 125 | logicals[i].lastSector[1] = UINT8_C(0); |
| 126 | logicals[i].lastSector[2] = UINT8_C(0); |
| 127 | logicals[i].firstLBA = UINT32_C(0); |
| 128 | logicals[i].lengthLBA = UINT32_C(0); |
| 129 | } // for |
| 130 | |
| 131 | read(fd, code, 440); |
| 132 | read(fd, &diskSignature, 4); |
| 133 | read(fd, &nulls, 2); |
| 134 | read(fd, partitions, 64); |
| 135 | read(fd, &MBRSignature, 2); |
| 136 | if (MBRSignature != MBR_SIGNATURE) { |
| 137 | allOK = 0; |
| 138 | state = invalid; |
| 139 | fprintf(stderr, "MBR signature invalid; read 0x%04X, but should be 0x%04X\n", |
| 140 | (unsigned int) MBRSignature, (unsigned int) MBR_SIGNATURE); |
| 141 | } /* if */ |
| 142 | |
| 143 | // Find disk size |
| 144 | diskSize = disksize(fd, &err); |
| 145 | |
| 146 | // Find block size |
| 147 | if ((blockSize = GetBlockSize(fd)) == -1) { |
| 148 | blockSize = SECTOR_SIZE; |
| 149 | printf("Unable to determine sector size; assuming %lu bytes!\n", |
| 150 | (unsigned long) SECTOR_SIZE); |
| 151 | } // if |
| 152 | |
| 153 | // Load logical partition data, if any is found.... |
| 154 | if (allOK) { |
| 155 | for (i = 0; i < 4; i++) { |
| 156 | if ((partitions[i].partitionType == 0x05) || (partitions[i].partitionType == 0x0f) |
| 157 | || (partitions[i].partitionType == 0x85)) { |
| 158 | // Found it, so call a recursive algorithm to load everything from them.... |
| 159 | allOK = ReadLogicalPart(fd, partitions[i].firstLBA, UINT32_C(0), 0); |
| 160 | } // if |
| 161 | } // for |
| 162 | if (allOK) { // Loaded logicals OK |
| 163 | state = mbr; |
| 164 | } else { |
| 165 | state = invalid; |
| 166 | } // if |
| 167 | } // if |
| 168 | |
| 169 | /* Check to see if it's in GPT format.... */ |
| 170 | if (allOK) { |
| 171 | for (i = 0; i < 4; i++) { |
| 172 | if (partitions[i].partitionType == UINT8_C(0xEE)) { |
| 173 | state = gpt; |
| 174 | } /* if */ |
| 175 | } /* for */ |
| 176 | } /* if */ |
| 177 | |
| 178 | /* // Tell the user what the MBR state is... |
| 179 | switch (state) { |
| 180 | case invalid: |
| 181 | printf("Information: MBR appears to be empty or invalid.\n"); |
| 182 | break; |
| 183 | case gpt: |
| 184 | printf("Information: MBR holds GPT placeholder partitions.\n"); |
| 185 | break; |
| 186 | case hybrid: |
| 187 | printf("Information: MBR holds hybrid GPT/MBR data.\n"); |
| 188 | break; |
| 189 | case mbr: |
| 190 | printf("Information: MBR data appears to be valid.\n"); |
| 191 | break; |
| 192 | } // switch */ |
| 193 | } // MBRData::ReadMBRData(int fd) |
| 194 | |
| 195 | // Write the MBR data to the default defined device. |
| 196 | int MBRData::WriteMBRData(void) { |
| 197 | int allOK = 1, fd; |
| 198 | |
| 199 | if ((fd = open(device, O_WRONLY | O_CREAT, S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH)) != -1) { |
| 200 | WriteMBRData(fd); |
| 201 | } else { |
| 202 | allOK = 0; |
| 203 | } // if/else |
| 204 | close(fd); |
| 205 | return allOK; |
| 206 | } // MBRData::WriteMBRData(void) |
| 207 | |
| 208 | // Save the MBR data to a file. Note that this function writes ONLY the |
| 209 | // MBR data, not the logical partitions (if any are defined). |
| 210 | void MBRData::WriteMBRData(int fd) { |
| 211 | write(fd, code, 440); |
| 212 | write(fd, &diskSignature, 4); |
| 213 | write(fd, &nulls, 2); |
| 214 | write(fd, partitions, 64); |
| 215 | write(fd, &MBRSignature, 2); |
| 216 | } // MBRData::WriteMBRData(int fd) |
| 217 | |
| 218 | // This is a recursive function to read all the logical partitions, following the |
| 219 | // logical partition linked list from the disk and storing the basic data in |
| 220 | int MBRData::ReadLogicalPart(int fd, uint32_t extendedStart, |
| 221 | uint32_t diskOffset, int partNum) { |
| 222 | int allOK = 1; |
| 223 | struct EBRRecord ebr; |
| 224 | off_t offset; |
| 225 | |
| 226 | offset = (off_t) (extendedStart + diskOffset) * blockSize; |
| 227 | if (lseek64(fd, offset, SEEK_SET) == (off_t) -1) { // seek to EBR record |
| 228 | fprintf(stderr, "Unable to seek to %lu! Aborting!\n", (unsigned long) offset); |
| 229 | allOK = 0; |
| 230 | } |
| 231 | if (read(fd, &ebr, 512) != 512) { // Load the data.... |
| 232 | fprintf(stderr, "Error seeking to or reading logical partition data from %lu!\nAborting!\n", |
| 233 | (unsigned long) offset); |
| 234 | allOK = 0; |
| 235 | } |
| 236 | if (ebr.MBRSignature != MBR_SIGNATURE) { |
| 237 | allOK = 0; |
| 238 | printf("MBR signature in logical partition invalid; read 0x%04X, but should be 0x%04X\n", |
| 239 | (unsigned int) ebr.MBRSignature, (unsigned int) MBR_SIGNATURE); |
| 240 | } /* if */ |
| 241 | |
| 242 | // Copy over the basic data.... |
| 243 | logicals[partNum].status = ebr.partitions[0].status; |
| 244 | logicals[partNum].firstLBA = ebr.partitions[0].firstLBA + diskOffset + extendedStart; |
| 245 | logicals[partNum].lengthLBA = ebr.partitions[0].lengthLBA; |
| 246 | logicals[partNum].partitionType = ebr.partitions[0].partitionType; |
| 247 | |
| 248 | // Find the next partition (if there is one) and recurse.... |
| 249 | if ((ebr.partitions[1].firstLBA != UINT32_C(0)) && allOK) { |
| 250 | allOK = ReadLogicalPart(fd, extendedStart, ebr.partitions[1].firstLBA, |
| 251 | partNum + 1); |
| 252 | } // if |
| 253 | return (allOK); |
| 254 | } // MBRData::ReadLogicalPart() |
| 255 | |
| 256 | // Show the MBR data to the user.... |
| 257 | void MBRData::DisplayMBRData(void) { |
| 258 | int i; |
| 259 | char tempStr[255]; |
| 260 | |
| 261 | printf("MBR disk identifier: 0x%08X\n", (unsigned int) diskSignature); |
| 262 | printf("MBR partitions:\n"); |
| 263 | printf("Number\t Start (block)\t Length (blocks)\tType\n"); |
| 264 | for (i = 0; i < 4; i++) { |
| 265 | if (partitions[i].lengthLBA != 0) { |
| 266 | printf("%4d\t%13lu\t%15lu \t0x%02X\n", i + 1, (unsigned long) partitions[i].firstLBA, |
| 267 | (unsigned long) partitions[i].lengthLBA, partitions[i].partitionType); |
| 268 | } // if |
| 269 | } // for |
| 270 | |
| 271 | // Now display logical partition data.... |
| 272 | for (i = 0; i < NUM_LOGICALS; i++) { |
| 273 | if (logicals[i].lengthLBA != 0) { |
| 274 | printf("%4d\t%13lu\t%15lu \t0x%02X\n", i + 5, (unsigned long) logicals[i].firstLBA, |
| 275 | (unsigned long) logicals[i].lengthLBA, logicals[i].partitionType); |
| 276 | } // if |
| 277 | } // for |
| 278 | printf("\nDisk size is %lu sectors (%s)\n", (unsigned long) diskSize, |
| 279 | BytesToSI(diskSize * (uint64_t) blockSize, tempStr)); |
| 280 | } // MBRData::DisplayMBRData() |
| 281 | |
| 282 | // Create a protective MBR |
| 283 | void MBRData::MakeProtectiveMBR(void) { |
| 284 | int i; |
| 285 | |
| 286 | // Initialize variables |
| 287 | nulls = 0; |
| 288 | MBRSignature = MBR_SIGNATURE; |
| 289 | |
| 290 | partitions[0].status = UINT8_C(0); // Flag the protective part. as unbootable |
| 291 | |
| 292 | // Write CHS data. This maxes out the use of the disk, as much as |
| 293 | // possible -- even to the point of exceeding the capacity of sub-8GB |
| 294 | // disks. The EFI spec says to use 0xffffff as the ending value, |
| 295 | // although normal MBR disks max out at 0xfeffff. FWIW, both GNU Parted |
| 296 | // and Apple's Disk Utility use 0xfeffff, and the latter puts that |
| 297 | // value in for the FIRST sector, too! |
| 298 | partitions[0].firstSector[0] = UINT8_C(0); |
| 299 | partitions[0].firstSector[1] = UINT8_C(1); |
| 300 | partitions[0].firstSector[2] = UINT8_C(0); |
| 301 | partitions[0].lastSector[0] = UINT8_C(255); |
| 302 | partitions[0].lastSector[1] = UINT8_C(255); |
| 303 | partitions[0].lastSector[2] = UINT8_C(255); |
| 304 | |
| 305 | partitions[0].partitionType = UINT8_C(0xEE); |
| 306 | partitions[0].firstLBA = UINT32_C(1); |
| 307 | if (diskSize < UINT32_MAX) { // If the disk is under 2TiB |
| 308 | partitions[0].lengthLBA = diskSize - 1; |
| 309 | } else { // disk is too big to represent, so fake it... |
| 310 | partitions[0].lengthLBA = UINT32_MAX; |
| 311 | } // if/else |
| 312 | |
| 313 | // Zero out three unused primary partitions... |
| 314 | for (i = 1; i < 4; i++) { |
| 315 | partitions[i].status = UINT8_C(0); |
| 316 | partitions[i].firstSector[0] = UINT8_C(0); |
| 317 | partitions[i].firstSector[1] = UINT8_C(0); |
| 318 | partitions[i].firstSector[2] = UINT8_C(0); |
| 319 | partitions[i].partitionType = UINT8_C(0); |
| 320 | partitions[i].lastSector[0] = UINT8_C(0); |
| 321 | partitions[i].lastSector[1] = UINT8_C(0); |
| 322 | partitions[i].lastSector[2] = UINT8_C(0); |
| 323 | partitions[i].firstLBA = UINT32_C(0); |
| 324 | partitions[i].lengthLBA = UINT32_C(0); |
| 325 | } // for |
| 326 | |
| 327 | // Zero out all the logical partitions. Not necessary for data |
| 328 | // integrity on write, but eliminates stray entries if user wants |
| 329 | // to view the MBR after converting the disk |
| 330 | for (i = 0; i < NUM_LOGICALS; i++) { |
| 331 | logicals[i].status = UINT8_C(0); |
| 332 | logicals[i].firstSector[0] = UINT8_C(0); |
| 333 | logicals[i].firstSector[1] = UINT8_C(0); |
| 334 | logicals[i].firstSector[2] = UINT8_C(0); |
| 335 | logicals[i].partitionType = UINT8_C(0); |
| 336 | logicals[i].lastSector[0] = UINT8_C(0); |
| 337 | logicals[i].lastSector[1] = UINT8_C(0); |
| 338 | logicals[i].lastSector[2] = UINT8_C(0); |
| 339 | logicals[i].firstLBA = UINT32_C(0); |
| 340 | logicals[i].lengthLBA = UINT32_C(0); |
| 341 | } // for |
| 342 | |
| 343 | state = gpt; |
| 344 | } // MBRData::MakeProtectiveMBR() |
| 345 | |
| 346 | // Return a pointer to a primary or logical partition, or NULL if |
| 347 | // the partition is out of range.... |
| 348 | struct MBRRecord* MBRData::GetPartition(int i) { |
| 349 | MBRRecord* thePart = NULL; |
| 350 | |
| 351 | if ((i >= 0) && (i < 4)) { // primary partition |
| 352 | thePart = &partitions[i]; |
| 353 | } // if |
| 354 | if ((i >= 4) && (i < (NUM_LOGICALS + 4))) { |
| 355 | thePart = &logicals[i - 4]; |
| 356 | } // if |
| 357 | return thePart; |
| 358 | } // GetPartition() |
| 359 | |
| 360 | // Displays the state, as a word, on stdout. Used for debugging |
| 361 | void MBRData::ShowState(void) { |
| 362 | switch (state) { |
| 363 | case invalid: |
| 364 | printf("invalid"); |
| 365 | break; |
| 366 | case gpt: |
| 367 | printf("gpt"); |
| 368 | break; |
| 369 | case hybrid: |
| 370 | printf("hybrid"); |
| 371 | break; |
| 372 | case mbr: |
| 373 | printf("mbr"); |
| 374 | break; |
| 375 | default: |
| 376 | printf("unknown -- bug!"); |
| 377 | break; |
| 378 | } // switch |
| 379 | } // MBRData::ShowState() |
| 380 | |
| 381 | // Create a primary partition of the specified number, starting LBA, |
| 382 | // and length. This function does *NO* error checking, so it's possible |
| 383 | // to seriously screw up a partition table using this function! It's |
| 384 | // intended as a way to create a hybrid MBR, which is a pretty funky |
| 385 | // setup to begin with.... |
| 386 | void MBRData::MakePart(int num, uint32_t start, uint32_t length, int type, |
| 387 | int bootable) { |
| 388 | |
| 389 | partitions[num].status = (uint8_t) bootable * (uint8_t) 0x80; |
| 390 | partitions[num].firstSector[0] = UINT8_C(0); |
| 391 | partitions[num].firstSector[1] = UINT8_C(0); |
| 392 | partitions[num].firstSector[2] = UINT8_C(0); |
| 393 | partitions[num].partitionType = (uint8_t) type; |
| 394 | partitions[num].lastSector[0] = UINT8_C(0); |
| 395 | partitions[num].lastSector[1] = UINT8_C(0); |
| 396 | partitions[num].lastSector[2] = UINT8_C(0); |
| 397 | partitions[num].firstLBA = start; |
| 398 | partitions[num].lengthLBA = length; |
| 399 | } // MakePart() |
| 400 | |
| 401 | uint8_t MBRData::GetStatus(int i) { |
| 402 | MBRRecord* thePart; |
| 403 | uint8_t retval; |
| 404 | |
| 405 | thePart = GetPartition(i); |
| 406 | if (thePart != NULL) |
| 407 | retval = thePart->status; |
| 408 | else |
| 409 | retval = UINT8_C(0); |
| 410 | return retval; |
| 411 | } // MBRData::GetStatus() |
| 412 | |
| 413 | uint8_t MBRData::GetType(int i) { |
| 414 | MBRRecord* thePart; |
| 415 | uint8_t retval; |
| 416 | |
| 417 | thePart = GetPartition(i); |
| 418 | if (thePart != NULL) |
| 419 | retval = thePart->partitionType; |
| 420 | else |
| 421 | retval = UINT8_C(0); |
| 422 | return retval; |
| 423 | } // MBRData::GetType() |
| 424 | |
| 425 | uint32_t MBRData::GetFirstSector(int i) { |
| 426 | MBRRecord* thePart; |
| 427 | uint32_t retval; |
| 428 | |
| 429 | thePart = GetPartition(i); |
| 430 | if (thePart != NULL) { |
| 431 | retval = thePart->firstLBA; |
| 432 | } else |
| 433 | retval = UINT32_C(0); |
| 434 | return retval; |
| 435 | } // MBRData::GetFirstSector() |
| 436 | |
| 437 | uint32_t MBRData::GetLength(int i) { |
| 438 | MBRRecord* thePart; |
| 439 | uint32_t retval; |
| 440 | |
| 441 | thePart = GetPartition(i); |
| 442 | if (thePart != NULL) { |
| 443 | retval = thePart->lengthLBA; |
| 444 | } else |
| 445 | retval = UINT32_C(0); |
| 446 | return retval; |
| 447 | } // MBRData::GetLength() |