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rulimine/stage23/fs/fat32.s2.c
mintsuki 4a87babe4a misc: Forbid variable shadowing
2021-07-06 05:17:18 +02:00

400 lines
13 KiB
C
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#include <fs/fat32.h>
#include <lib/blib.h>
#include <drivers/disk.h>
#include <lib/libc.h>
#include <lib/print.h>
#include <mm/pmm.h>
#include <stdbool.h>
#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_SECTOR_SIZE 512
#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];
} __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_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));
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;
}
}
if (strncmp((((void *)&bpb) + 0x36), FAT16_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) == 0) {
context->type = 16;
goto valid;
}
if (strncmp((((void *)&bpb) + 0x36), FAT12_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) == 0) {
context->type = 12;
goto valid;
}
return 1;
valid:
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.directory_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), FAT32_SECTOR_SIZE);
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();
}
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 * FAT32_SECTOR_SIZE + (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 * FAT32_SECTOR_SIZE + cluster * sizeof(uint16_t), sizeof(uint16_t));
break;
case 32:
volume_read(context->part, out, context->fat_start_lba * FAT32_SECTOR_SIZE + 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 * FAT32_SECTOR_SIZE;
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) * FAT32_SECTOR_SIZE;
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 * FAT32_SECTOR_SIZE;
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);
if (!read_cluster_chain(context, directory_cluster_chain, directory_entries, 0, dir_chain_len * block_size))
return -1;
} 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 * FAT32_SECTOR_SIZE, context->root_entries * sizeof(struct fat32_directory_entry));
}
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 (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;
}
}
if (!strcmp(current_lfn, name)) {
*file = directory_entries[i+1];
return 0;
}
} else {
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];
return 0;
}
}
}
// file not found
return -1;
}
int fat32_check_signature(struct volume *part) {
struct fat32_context context;
return fat32_init_context(&context, part) == 0;
}
int fat32_open(struct fat32_file_handle* ret, struct volume *part, const char* path) {
struct fat32_context context;
int r = fat32_init_context(&context, part);
if (r) {
print("fat32: context init failure (%d)\n", r);
return r;
}
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, &current_file, current_part)) != 0) {
return r;
}
if (expect_directory) {
_current_directory = current_file;
current_directory = &_current_directory;
} else {
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, FAT32_SECTOR_SIZE);
ret->size_bytes = current_file.file_size_bytes;
size_t file_chain_len;
ret->cluster_chain = cache_cluster_chain(&context, ret->first_cluster, &file_chain_len);
return 0;
}
}
}
int fat32_read(struct fat32_file_handle* file, void* buf, uint64_t loc, uint64_t count) {
return !read_cluster_chain(&file->context, file->cluster_chain, buf, loc, count);
}
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