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fat: Improve detection code

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This commit is contained in:
mintsuki 2022-05-07 16:24:04 +02:00
parent c22492976a
commit c8973ed681
3 changed files with 84 additions and 42 deletions
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114
common/fs/fat32.s2.c
View File

@ -9,42 +9,42 @@
#define FAT32_LFN_MAX_ENTRIES 20
#define FAT32_LFN_MAX_FILENAME_LENGTH (FAT32_LFN_MAX_ENTRIES * 13 + 1)
#define FAT32_VALID_SIGNATURE_1 0x28
#define FAT32_VALID_SIGNATURE_2 0x29
#define FAT32_VALID_SYSTEM_IDENTIFIER "FAT32 "
#define FAT16_VALID_SYSTEM_IDENTIFIER "FAT16 "
#define FAT12_VALID_SYSTEM_IDENTIFIER "FAT12 "
#define FAT32_ATTRIBUTE_SUBDIRECTORY 0x10
#define FAT32_LFN_ATTRIBUTE 0x0F
struct fat32_bpb {
uint8_t jump[3];
char oem[8];
uint16_t bytes_per_sector;
uint8_t sectors_per_cluster;
uint16_t reserved_sectors;
uint8_t fats_count;
uint16_t directory_entries_count;
uint16_t sector_totals;
uint8_t media_descriptor_type;
uint16_t sectors_per_fat_16;
uint16_t sectors_per_track;
uint16_t heads_count;
uint32_t hidden_sectors_count;
uint32_t large_sectors_count;
uint32_t sectors_per_fat_32;
uint16_t flags;
uint16_t fat_version_number;
uint32_t root_directory_cluster;
uint16_t fs_info_sector;
uint16_t backup_boot_sector;
uint8_t reserved[12];
uint8_t drive_number;
uint8_t nt_flags;
uint8_t signature;
uint32_t volume_serial_number;
char label[11];
char system_identifier[8];
union {
struct {
uint8_t jump[3];
char oem[8];
uint16_t bytes_per_sector;
uint8_t sectors_per_cluster;
uint16_t reserved_sectors;
uint8_t fats_count;
uint16_t root_entries_count;
uint16_t sectors_count_16;
uint8_t media_descriptor_type;
uint16_t sectors_per_fat_16;
uint16_t sectors_per_track;
uint16_t heads_count;
uint32_t hidden_sectors_count;
uint32_t sectors_count_32;
uint32_t sectors_per_fat_32;
uint16_t flags;
uint16_t fat_version_number;
uint32_t root_directory_cluster;
uint16_t fs_info_sector;
uint16_t backup_boot_sector;
uint8_t reserved[12];
uint8_t drive_number;
uint8_t nt_flags;
uint8_t signature;
uint32_t volume_serial_number;
char label[11];
char system_identifier[8];
} __attribute__((packed));
uint8_t padding[512];
};
} __attribute__((packed));
struct fat32_directory_entry {
@ -74,26 +74,56 @@ static int fat32_init_context(struct fat32_context* context, struct volume *part
struct fat32_bpb bpb;
volume_read(context->part, &bpb, 0, sizeof(struct fat32_bpb));
if (strncmp(bpb.system_identifier, FAT32_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) == 0) {
if (bpb.signature == FAT32_VALID_SIGNATURE_1 || bpb.signature == FAT32_VALID_SIGNATURE_2) {
context->type = 32;
goto valid;
}
// Generic check
if (*(uint16_t *)(((void *)&bpb) + 510) != 0xaa55) {
return 1;
}
if (strncmp((((void *)&bpb) + 0x36), FAT16_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) == 0) {
context->type = 16;
// Checks for FAT12/16
if (strncmp((((void *)&bpb) + 0x36), "FAT", 3) == 0) {
if (*(((uint8_t *)&bpb) + 0x26) != 0x29) {
for (size_t i = 0; i < 15; i++) {
if (*(((uint8_t *)&bpb) + 0x27 + i) != 0) {
return 1;
}
}
}
goto valid;
}
if (strncmp((((void *)&bpb) + 0x36), FAT12_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) == 0) {
context->type = 12;
// Checks for FAT32
if (strncmp((((void *)&bpb) + 0x52), "FAT", 3) == 0) {
if (*(((uint8_t *)&bpb) + 0x42) != 0x29) {
for (size_t i = 0; i < 15; i++) {
if (*(((uint8_t *)&bpb) + 0x43 + i) != 0) {
return 1;
}
}
}
goto valid;
}
return 1;
valid:
// The following mess to identify the FAT type is from the FAT spec
// at paragraph 3.5
size_t root_dir_sects = ((bpb.root_entries_count * 32) + (bpb.bytes_per_sector - 1)) / bpb.bytes_per_sector;
size_t data_sects = (bpb.sectors_count_16 ?: bpb.sectors_count_32) - (bpb.reserved_sectors + (bpb.fats_count * (bpb.sectors_per_fat_16 ?: bpb.sectors_per_fat_32)) + root_dir_sects);
size_t clusters_count = data_sects / bpb.sectors_per_cluster;
if (clusters_count < 4085) {
context->type = 12;
} else if (clusters_count < 65525) {
context->type = 16;
} else {
context->type = 32;
}
context->bytes_per_sector = bpb.bytes_per_sector;
context->sectors_per_cluster = bpb.sectors_per_cluster;
context->reserved_sectors = bpb.reserved_sectors;
@ -102,7 +132,7 @@ valid:
context->sectors_per_fat = context->type == 32 ? bpb.sectors_per_fat_32 : bpb.sectors_per_fat_16;
context->root_directory_cluster = bpb.root_directory_cluster;
context->fat_start_lba = bpb.reserved_sectors;
context->root_entries = bpb.directory_entries_count;
context->root_entries = bpb.root_entries_count;
context->root_start = context->reserved_sectors + context->number_of_fats * context->sectors_per_fat;
context->root_size = DIV_ROUNDUP(context->root_entries * sizeof(struct fat32_directory_entry), context->bytes_per_sector);
switch (context->type) {

3
common/lib/part.s2.c
View File

@ -241,6 +241,9 @@ static bool is_valid_mbr(struct volume *volume) {
if (memcmp(hintc, "_ECH_FS_", 8) == 0)
return false;
volume_read(volume, hintc, 54, 3);
if (memcmp(hintc, "FAT", 3) == 0)
return false;
volume_read(volume, hintc, 82, 3);
if (memcmp(hintc, "FAT", 3) == 0)
return false;
volume_read(volume, &hint, 1080, sizeof(uint16_t));

9
limine-deploy/limine-deploy.c
View File

@ -490,6 +490,15 @@ int main(int argc, char *argv[]) {
device_write(hintc, 54, 5);
}
}
device_read(hintc, 82, 3);
if (memcmp(hintc, "FAT", 3) == 0) {
if (!force_mbr) {
mbr = 0;
} else {
memset(hintc, 0, 5);
device_write(hintc, 82, 5);
}
}
device_read(&hint16, 1080, sizeof(uint16_t));
hint16 = ENDSWAP(hint16);
if (hint16 == 0xef53) {