#include #include #include #include #include #include #include #define FAT32_LFN_MAX_ENTRIES 20 #define FAT32_LFN_MAX_FILENAME_LENGTH (FAT32_LFN_MAX_ENTRIES * 13 + 1) #define FAT32_ATTRIBUTE_SUBDIRECTORY 0x10 #define FAT32_LFN_ATTRIBUTE 0x0F #define FAT32_ATTRIBUTE_VOLLABEL 0x08 struct fat32_context { struct volume *part; int type; char *label; uint16_t bytes_per_sector; uint8_t sectors_per_cluster; uint16_t reserved_sectors; uint8_t number_of_fats; uint32_t hidden_sectors; uint32_t sectors_per_fat; uint32_t fat_start_lba; uint32_t data_start_lba; uint32_t root_directory_cluster; uint16_t root_entries; uint32_t root_start; uint32_t root_size; }; struct fat32_file_handle { struct fat32_context context; uint32_t first_cluster; uint32_t size_bytes; uint32_t size_clusters; uint32_t *cluster_chain; size_t chain_len; }; struct fat32_bpb { 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 { char file_name_and_ext[8 + 3]; uint8_t attribute; uint8_t file_data_1[8]; uint16_t cluster_num_high; uint8_t file_data_2[4]; uint16_t cluster_num_low; uint32_t file_size_bytes; } __attribute__((packed)); struct fat32_lfn_entry { uint8_t sequence_number; char name1[10]; uint8_t attribute; uint8_t type; uint8_t dos_checksum; char name2[12]; uint16_t first_cluster; char name3[4]; } __attribute__((packed)); static int fat32_open_in(struct fat32_context* context, struct fat32_directory_entry* directory, struct fat32_directory_entry* file, const char* name); static int fat32_init_context(struct fat32_context* context, struct volume *part) { context->part = part; struct fat32_bpb bpb; volume_read(context->part, &bpb, 0, sizeof(struct fat32_bpb)); // Checks for FAT12/16 if (strncmp((((void *)&bpb) + 0x36), "FAT", 3) == 0) { goto valid; } // Checks for FAT32 if (strncmp((((void *)&bpb) + 0x52), "FAT", 3) == 0) { goto valid; } // Checks for FAT32 (with 64-bit sector count) if (strncmp((((void *)&bpb) + 0x03), "FAT32", 5) == 0) { 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; context->number_of_fats = bpb.fats_count; context->hidden_sectors = bpb.hidden_sectors_count; 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.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) { case 12: case 16: context->data_start_lba = context->root_start + context->root_size; break; case 32: context->data_start_lba = context->root_start; break; default: __builtin_unreachable(); } // get the volume label struct fat32_directory_entry _current_directory; struct fat32_directory_entry *current_directory; switch (context->type) { case 12: case 16: current_directory = NULL; break; case 32: _current_directory.cluster_num_low = context->root_directory_cluster & 0xFFFF; _current_directory.cluster_num_high = context->root_directory_cluster >> 16; current_directory = &_current_directory; break; default: __builtin_unreachable(); } char *vol_label; if (fat32_open_in(context, current_directory, (struct fat32_directory_entry *)&vol_label, NULL) == 0) { context->label = vol_label; } else { context->label = NULL; } return 0; } static int read_cluster_from_map(struct fat32_context *context, uint32_t cluster, uint32_t *out) { switch (context->type) { case 12: { *out = 0; uint16_t tmp = 0; volume_read(context->part, &tmp, context->fat_start_lba * context->bytes_per_sector + (cluster + cluster / 2), sizeof(uint16_t)); if (cluster % 2 == 0) { *out = tmp & 0xfff; } else { *out = tmp >> 4; } break; } case 16: *out = 0; volume_read(context->part, out, context->fat_start_lba * context->bytes_per_sector + cluster * sizeof(uint16_t), sizeof(uint16_t)); break; case 32: volume_read(context->part, out, context->fat_start_lba * context->bytes_per_sector + cluster * sizeof(uint32_t), sizeof(uint32_t)); *out &= 0x0fffffff; break; default: __builtin_unreachable(); } return 0; } static uint32_t *cache_cluster_chain(struct fat32_context *context, uint32_t initial_cluster, size_t *_chain_length) { uint32_t cluster_limit = (context->type == 12 ? 0xfef : 0) | (context->type == 16 ? 0xffef : 0) | (context->type == 32 ? 0xfffffef : 0); if (initial_cluster < 0x2 || initial_cluster > cluster_limit) return NULL; uint32_t cluster = initial_cluster; size_t chain_length; for (chain_length = 1; ; chain_length++) { read_cluster_from_map(context, cluster, &cluster); if (cluster < 0x2 || cluster > cluster_limit) break; } uint32_t *cluster_chain = ext_mem_alloc(chain_length * sizeof(uint32_t)); cluster = initial_cluster; for (size_t i = 0; i < chain_length; i++) { cluster_chain[i] = cluster; read_cluster_from_map(context, cluster, &cluster); } *_chain_length = chain_length; return cluster_chain; } static bool read_cluster_chain(struct fat32_context *context, uint32_t *cluster_chain, void *buf, uint64_t loc, uint64_t count) { size_t block_size = context->sectors_per_cluster * context->bytes_per_sector; for (uint64_t progress = 0; progress < count;) { uint64_t block = (loc + progress) / block_size; uint64_t chunk = count - progress; uint64_t offset = (loc + progress) % block_size; if (chunk > block_size - offset) chunk = block_size - offset; uint64_t base = ((uint64_t)context->data_start_lba + (cluster_chain[block] - 2) * context->sectors_per_cluster) * context->bytes_per_sector; volume_read(context->part, buf + progress, base + offset, chunk); progress += chunk; } return true; } // Copy ucs-2 characters to char* static void fat32_lfncpy(char* destination, const void* source, unsigned int size) { for (unsigned int i = 0; i < size; i++) { // ignore high bytes *(((uint8_t*) destination) + i) = *(((uint8_t*) source) + (i * 2)); } } static bool fat32_filename_to_8_3(char *dest, const char *src) { int i = 0, j = 0; bool ext = false; for (size_t k = 0; k < 8+3; k++) dest[k] = ' '; while (src[i]) { if (src[i] == '.') { if (ext) { // This is a double extension here, just give up. return false; } ext = true; j = 8; i++; continue; } if (j >= 8+3 || (j >= 8 && !ext)) { // Filename too long, give up. return false; } dest[j++] = toupper(src[i++]); } return true; } static int fat32_open_in(struct fat32_context* context, struct fat32_directory_entry* directory, struct fat32_directory_entry* file, const char* name) { size_t block_size = context->sectors_per_cluster * context->bytes_per_sector; char current_lfn[FAT32_LFN_MAX_FILENAME_LENGTH] = {0}; size_t dir_chain_len; struct fat32_directory_entry *directory_entries; if (directory != NULL) { uint32_t current_cluster_number = directory->cluster_num_low; if (context->type == 32) current_cluster_number |= (uint32_t)directory->cluster_num_high << 16; uint32_t *directory_cluster_chain = cache_cluster_chain(context, current_cluster_number, &dir_chain_len); if (directory_cluster_chain == NULL) return -1; directory_entries = ext_mem_alloc(dir_chain_len * block_size); read_cluster_chain(context, directory_cluster_chain, directory_entries, 0, dir_chain_len * block_size); pmm_free(directory_cluster_chain, dir_chain_len * sizeof(uint32_t)); } else { dir_chain_len = DIV_ROUNDUP(context->root_entries * sizeof(struct fat32_directory_entry), block_size); directory_entries = ext_mem_alloc(dir_chain_len * block_size); volume_read(context->part, directory_entries, context->root_start * context->bytes_per_sector, context->root_entries * sizeof(struct fat32_directory_entry)); } int ret; for (size_t i = 0; i < (dir_chain_len * block_size) / sizeof(struct fat32_directory_entry); i++) { if (directory_entries[i].file_name_and_ext[0] == 0x00) { // no more entries here break; } if (name == NULL) { if (directory_entries[i].attribute != FAT32_ATTRIBUTE_VOLLABEL) { continue; } char *r = ext_mem_alloc(12); memcpy(r, directory_entries[i].file_name_and_ext, 11); // remove trailing spaces for (int j = 10; j >= 0; j--) { if (r[j] == ' ') { r[j] = 0; continue; } break; } *((char **)file) = r; ret = 0; goto out; } if (directory_entries[i].attribute == FAT32_LFN_ATTRIBUTE) { struct fat32_lfn_entry* lfn = (struct fat32_lfn_entry*) &directory_entries[i]; if (lfn->sequence_number & 0b01000000) { // this lfn is the first entry in the table, clear the lfn buffer memset(current_lfn, ' ', sizeof(current_lfn)); } const unsigned int lfn_index = ((lfn->sequence_number & 0b00011111) - 1U) * 13U; if (lfn_index >= FAT32_LFN_MAX_ENTRIES * 13) { continue; } fat32_lfncpy(current_lfn + lfn_index + 00, lfn->name1, 5); fat32_lfncpy(current_lfn + lfn_index + 05, lfn->name2, 6); fat32_lfncpy(current_lfn + lfn_index + 11, lfn->name3, 2); if (lfn_index != 0) continue; // remove trailing spaces for (int j = SIZEOF_ARRAY(current_lfn) - 2; j >= -1; j--) { if (j == -1 || current_lfn[j] != ' ') { current_lfn[j + 1] = 0; break; } } int (*strcmpfn)(const char *, const char *) = case_insensitive_fopen ? strcasecmp : strcmp; if (strcmpfn(current_lfn, name) == 0) { *file = directory_entries[i+1]; ret = 0; goto out; } } if (directory_entries[i].attribute & (1 << 3)) { // It is a volume label, skip continue; } // SFN char fn[8+3]; if (!fat32_filename_to_8_3(fn, name)) { continue; } if (!strncmp(directory_entries[i].file_name_and_ext, fn, 8+3)) { *file = directory_entries[i]; ret = 0; goto out; } } // file not found ret = -1; out: pmm_free(directory_entries, dir_chain_len * block_size); return ret; } char *fat32_get_label(struct volume *part) { struct fat32_context context; if (fat32_init_context(&context, part) != 0) { return NULL; } return context.label; } static void fat32_read(struct file_handle *handle, void *buf, uint64_t loc, uint64_t count); static void fat32_close(struct file_handle *file); struct file_handle *fat32_open(struct volume *part, const char *path) { struct fat32_context context; int r = fat32_init_context(&context, part); if (r) { return NULL; } struct fat32_directory_entry _current_directory; struct fat32_directory_entry *current_directory; struct fat32_directory_entry current_file; unsigned int current_index = 0; char current_part[FAT32_LFN_MAX_FILENAME_LENGTH]; // skip trailing slashes while (path[current_index] == '/') { current_index++; } // walk down the directory tree switch (context.type) { case 12: case 16: current_directory = NULL; break; case 32: _current_directory.cluster_num_low = context.root_directory_cluster & 0xFFFF; _current_directory.cluster_num_high = context.root_directory_cluster >> 16; current_directory = &_current_directory; break; default: __builtin_unreachable(); } for (;;) { bool expect_directory = false; for (unsigned int i = 0; i < SIZEOF_ARRAY(current_part); i++) { if (path[i + current_index] == 0) { memcpy(current_part, path + current_index, i); current_part[i] = 0; expect_directory = false; break; } if (path[i + current_index] == '/') { memcpy(current_part, path + current_index, i); current_part[i] = 0; current_index += i + 1; expect_directory = true; break; } } if ((r = fat32_open_in(&context, current_directory, ¤t_file, current_part)) != 0) { return NULL; } if (expect_directory) { _current_directory = current_file; current_directory = &_current_directory; } else { struct file_handle *handle = ext_mem_alloc(sizeof(struct file_handle)); struct fat32_file_handle *ret = ext_mem_alloc(sizeof(struct fat32_file_handle)); ret->context = context; ret->first_cluster = current_file.cluster_num_low; if (context.type == 32) ret->first_cluster |= (uint64_t)current_file.cluster_num_high << 16; ret->size_clusters = DIV_ROUNDUP(current_file.file_size_bytes, context.bytes_per_sector); ret->size_bytes = current_file.file_size_bytes; ret->cluster_chain = cache_cluster_chain(&context, ret->first_cluster, &ret->chain_len); handle->fd = (void *)ret; handle->read = (void *)fat32_read; handle->close = (void *)fat32_close; handle->size = ret->size_bytes; handle->vol = part; #if uefi == 1 handle->efi_part_handle = part->efi_part_handle; #endif return handle; } } } static void fat32_read(struct file_handle *file, void *buf, uint64_t loc, uint64_t count) { struct fat32_file_handle *f = file->fd; read_cluster_chain(&f->context, f->cluster_chain, buf, loc, count); } static void fat32_close(struct file_handle *file) { struct fat32_file_handle *f = file->fd; pmm_free(f->cluster_chain, f->chain_len * sizeof(uint32_t)); pmm_free(f, sizeof(struct fat32_file_handle)); pmm_free(file, sizeof(struct file_handle)); }