C语言实现GPT头和分区表的读取

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

#define GPT_HEADER_SIGNATURE 0x5452415020494645LL

typedef char *PSTR;
typedef const char *PCSTR;

typedef struct {
    uint64_t signature;//<签名("EFI PART", 45 46 49 20 50 41 52 54)
    int revision;//<版本int header_size;//<头大小
    uint32_t crc_header;//<CRC32 of header
    int reserved;//<保留, must be zero
    uint64_t lba_current;//<第一个EFI PART所在扇区号
    uint64_t lba_backup;//<EFI PART备份所在扇区号
    uint64_t lba_first_usable;//<第一个有效分区起始扇区号
    uint64_t lba_last_usable;
    uint8_t disk_guid[16];
    uint64_t lba_entry_start;
    int entry_count;
    int entry_size;
    uint32_t crc_entries;
    int reserved1[105];
}__attribute__ ((packed)) gpt_header;

typedef struct {
    uint8_t type_guid[16];
    uint8_t unique_guid[16];
    uint64_t lba_first;
    uint64_t lba_last;
    uint64_t attribute;
    uint16_t name[36];
}__attribute__ ((packed)) partition_entry;

typedef struct {
    uint8_t status;
    uint8_t start_head;
    uint16_t start_sector;
    uint8_t part_type;
    uint8_t end_head;
    uint16_t end_sector;
    uint32_t first_abs_sector;
    uint32_t sector_count;
}__attribute__ ((packed)) mbr_part_entry;

typedef struct {
    uint8_t boot_code[440];
    int unique_mbr_signature;
    short unknown;
    mbr_part_entry partition_record[4];
    uint16_t signature;
}__attribute__ ((packed)) legacy_mbr;

static const uint32_t crc32_tab[] = { 0x00000000L, 0x77073096L, 0xee0e612cL,
        0x990951baL, 0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L,
        0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL,
        0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L,
        0xf3b97148L, 0x84be41deL, 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L,
        0x83d385c7L, 0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL,
        0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L,
        0x4c69105eL, 0xd56041e4L, 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L,
        0xd20d85fdL, 0xa50ab56bL, 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L,
        0xacbcf940L, 0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L,
        0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L,
        0x56b3c423L, 0xcfba9599L, 0xb8bda50fL, 0x2802b89eL, 0x5f058808L,
        0xc60cd9b2L, 0xb10be924L, 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL,
        0xb6662d3dL, 0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL,
        0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L,
        0x0f00f934L, 0x9609a88eL, 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL,
        0x91646c97L, 0xe6635c01L, 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L,
        0xf262004eL, 0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L,
        0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL,
        0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL,
        0xa3bc0074L, 0xd4bb30e2L, 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL,
        0xd3d6f4fbL, 0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L,
        0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL,
        0x270241aaL, 0xbe0b1010L, 0xc90c2086L, 0x5768b525L, 0x206f85b3L,
        0xb966d409L, 0xce61e49fL, 0x5edef90eL, 0x29d9c998L, 0xb0d09822L,
        0xc7d7a8b4L, 0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL,
        0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL, 0xead54739L,
        0x9dd277afL, 0x04db2615L, 0x73dc1683L, 0xe3630b12L, 0x94643b84L,
        0x0d6d6a3eL, 0x7a6a5aa8L, 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L,
        0x7d079eb1L, 0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL,
        0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L,
        0x89d32be0L, 0x10da7a5aL, 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L,
        0x17b7be43L, 0x60b08ed5L, 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L,
        0x4fdff252L, 0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL,
        0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L, 0xdf60efc3L,
        0xa867df55L, 0x316e8eefL, 0x4669be79L, 0xcb61b38cL, 0xbc66831aL,
        0x256fd2a0L, 0x5268e236L, 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L,
        0x5505262fL, 0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L,
        0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L,
        0xec63f226L, 0x756aa39cL, 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL,
        0x72076785L, 0x05005713L, 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL,
        0x0cb61b38L, 0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L,
        0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL,
        0xf6b9265bL, 0x6fb077e1L, 0x18b74777L, 0x88085ae6L, 0xff0f6a70L,
        0x66063bcaL, 0x11010b5cL, 0x8f659effL, 0xf862ae69L, 0x616bffd3L,
        0x166ccf45L, 0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L,
        0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL,
        0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L,
        0x47b2cf7fL, 0x30b5ffe9L, 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L,
        0x24b4a3a6L, 0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL,
        0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L,
        0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL };
static uint32_t __efi_crc32(const void *buf, int len, uint32_t seed) {
    int i;
    register uint32_t crc32val;
    const unsigned char *s = buf;
    crc32val = seed;
    for (i = 0; i < len; i++) {
        crc32val = crc32_tab[(crc32val ^ s[i]) & 0xff] ^ (crc32val >> 8);
    }
    return crc32val;
}

uint32_t crc32(const void *buf, int len) {
    return (__efi_crc32(buf, len, ~0L) ^ ~0L);
}

PSTR uuid_to_str(uint8_t *data) {
    PSTR buf = (PSTR) malloc(37);
    PCSTR hex = "0123456789ABCDEF";

    PSTR p = buf;
    uint32_t num = *((uint32_t *) data);
    p += sprintf(p, "%08X-", num);
    data += 4;

    uint16_t num2 = *((uint16_t *) data);
    p += sprintf(p, "%04hX-", num2);
    data += 2;

    num2 = *((uint16_t *) data);
    p += sprintf(p, "%04hX-", num2);
    data += 2;

    int i;
    for (i = 0; i < 8; i++) {
        if (i == 2) *p++ = ‘-‘;
        *p++ = hex[data[i] >> 4];
        *p++ = hex[data[i] & 0xF];
    }

    buf[36] = ‘\0‘;
    return buf;
}

wchar_t *utf16_to_wchar(uint16_t *str, int len) {
    int i = 0;
    wchar_t *buf = (wchar_t *) malloc((len + 1) * sizeof(wchar_t));
    for (; i < len; i++)
        buf[i] = (wchar_t) str[i];
    buf[len] = L‘\0‘;
    return buf;
}

int measure_block_size(int fd, int isAlt) {
    int i = 1, offset, size = 512, whence = isAlt ? SEEK_END : SEEK_SET;
    uint64_t signature;
    for (; i < 9; i++) {
        offset = i * size;
        if (lseek(fd, isAlt ? (-1 * offset) : offset, whence) == -1) {
            perror("Can‘t lseek"); return -1;
        }
        signature = 0;
        if (read(fd, &signature, 8) == -1) {
            perror("read file error"); return -1;
        }
        if (signature == GPT_HEADER_SIGNATURE) return offset;
    }
    return 0;
}

int print_legacy_mbr(int fd) {
    legacy_mbr mbr;
    memset(&mbr, 0, sizeof(legacy_mbr));
    if (read(fd, &mbr, sizeof(legacy_mbr)) == -1) {
        perror("read file error"); return -1;
    }

    mbr_part_entry empty;
    memset(&empty, 0, sizeof(mbr_part_entry));
    mbr_part_entry *p;
    int i = 0;
    for (; i < 4; i++) {
        p = &mbr.partition_record[i];
        if (!memcmp(p, &empty, sizeof(mbr_part_entry))) continue;
        printf("status=%hhu\tstart_head=%hhu\tstart_sector=%hu\tpart_type=0x%hhx\t"
                "end_head=%hhu\tend_sector=%hu\tfirst_abs_sector=%u\tsector_count=%u\n",
                p->status, p->start_head, p->start_sector, p->part_type,
                p->end_head, p->end_sector, p->first_abs_sector,
                p->sector_count);
    }

    printf("signature=0x%hX\n", mbr.signature);
    return 0;
}

int print_gpt_header(int fd, gpt_header *gpt) {
    memset(gpt, 0, sizeof(gpt_header));
    if (read(fd, gpt, sizeof(gpt_header)) == -1) {
        perror("read file error"); return -1;
    }

    char sz[9];
    memcpy(sz, &gpt->signature, 8);
    sz[8] = ‘\0‘;
    printf("signature=%s\n", sz);
    printf("revision=%d\n", gpt->revision);
    printf("header_size=%d\n", gpt->header_size);
    printf("crc_header=0x%X\n", gpt->crc_header);
    printf("lba_current=%lu\n", gpt->lba_current);
    printf("lba_backup=%lu\n", gpt->lba_backup);
    printf("lba_first_usable=%lu\n", gpt->lba_first_usable);
    printf("lba_last_usable=%lu\n", gpt->lba_last_usable);
    PSTR buf = uuid_to_str(gpt->disk_guid);
    printf("disk_guid=%s\n", buf);
    free(buf);
    printf("lba_entry_start=%lu\n", gpt->lba_entry_start);
    printf("entry_count=%d\n", gpt->entry_count);
    printf("entry_size=%d\n", gpt->entry_size);
    printf("crc_entries=0x%X\n", gpt->crc_entries);

    uint32_t oldcrc = gpt->crc_header;
    gpt->crc_header = 0;
    if (crc32(gpt, gpt->header_size) != oldcrc)
        fputs("Bad crc_header.\n", stderr);
    gpt->crc_header = oldcrc;

    return 0;
}

int print_gpt_partitions(int fd, const gpt_header *gpt) {
    int entries_size = gpt->entry_count * gpt->entry_size;
    PSTR buf = (PSTR) malloc(entries_size);
    if (read(fd, buf, entries_size) == -1) {
        perror("read file error"); return -1;
    }

    wchar_t *gpt_entry_name;
    partition_entry *gentry = (partition_entry *) buf;
    partition_entry gentry_empty;
    memset(&gentry_empty, 0, sizeof(partition_entry));

    PSTR tmp;
    int i = 0;
    for (; i < gpt->entry_count; i++) {
        if (!memcmp(gentry, &gentry_empty, sizeof(partition_entry)))
            continue;
        gpt_entry_name = utf16_to_wchar(gentry->name, 36);
        tmp = uuid_to_str(gentry->type_guid);
        printf("type_guid=%s\t", tmp);
        free(tmp);
        tmp = uuid_to_str(gentry->unique_guid);
        printf("unique_guid=%s\t", tmp);
        free(tmp);
        printf("lba_first=%lu\tlba_last=%lu\tattribute=%lu\tname=%ls\n",
                gentry->lba_first, gentry->lba_last, gentry->attribute,
                gpt_entry_name);
        free(gpt_entry_name);
        gentry++;
    }

    if (crc32(buf, entries_size) != gpt->crc_entries)
        fputs("Bad crc_entries.\n", stderr);

    free(buf);
    return 0;
}

/*
 * Usage1: Show primary GPT header and entries
 *         <app> /dev/sda
 * Usage2: Show secondary GPT header and entries
 *         <app> /dev/sda alternate
 */
int main(int argc, PCSTR argv[]) {
    int exitCode = EXIT_SUCCESS;
    PCSTR filename;
    int isAlternate = 0;
    if (argc < 2) {
        fputs("Missing argument.\n", stderr);
        return EXIT_FAILURE;
    } else {
        filename = argv[1];
        if (argc > 2) isAlternate = 1;
    }

    int fd = open(filename, O_RDONLY);
    if (fd == -1) {
        perror("Can‘t open device"); return EXIT_FAILURE;
    }

    int logical_blk_size = measure_block_size(fd, isAlternate);
    if (logical_blk_size < 1) {
        if (!logical_blk_size)
            fputs("Unknown logical block size.\n", stderr);
        exitCode = EXIT_FAILURE; goto END;
    }
    printf("Logical block size: %dbytes\n\n", logical_blk_size);

    if (isAlternate) {
        if (lseek(fd, -1 * logical_blk_size, SEEK_END) == -1) {
            perror("Can‘t lseek"); exitCode = EXIT_FAILURE; goto END;
        }
    } else {
        if (lseek(fd, 0, SEEK_SET) == -1) {
            perror("Can‘t lseek"); exitCode = EXIT_FAILURE; goto END;
        }
        if (print_legacy_mbr(fd)) {
            exitCode = EXIT_FAILURE; goto END;
        }
        putchar(‘\n‘);

        if (lseek(fd, logical_blk_size, SEEK_SET) == -1) {
            perror("Can‘t lseek"); exitCode = EXIT_FAILURE; goto END;
        }
    }

    gpt_header header;
    if (print_gpt_header(fd, &header)) {
        exitCode = EXIT_FAILURE; goto END;
    }
    putchar(‘\n‘);

    if (isAlternate) {
        if (lseek(fd, -1 * (header.entry_count * header.entry_size + logical_blk_size), SEEK_END) == -1) {
            perror("Can‘t lseek"); exitCode = EXIT_FAILURE; goto END;
        }
    } else if (lseek(fd, logical_blk_size * header.lba_entry_start, SEEK_SET) == -1) {
        perror("Can‘t lseek"); exitCode = EXIT_FAILURE; goto END;
    }
    print_gpt_partitions(fd, &header);

END:
    close(fd);
    return exitCode;
}