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FAT32 support

This commit is contained in:
KrekBuk 2020-05-01 17:19:29 +02:00
parent e3dbdad6c8
commit af1b908d77
6 changed files with 386 additions and 0 deletions
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21
Makefile
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@ -39,3 +39,24 @@ ext2-test: all
rm -rf test_image loopback_dev rm -rf test_image loopback_dev
./qloader2-install src/qloader2.bin test.img 2048 ./qloader2-install src/qloader2.bin test.img 2048
qemu-system-x86_64 -hda test.img -debugcon stdio qemu-system-x86_64 -hda test.img -debugcon stdio
fat32-test: all
$(MAKE) -C test
rm -rf test.img test_image/
mkdir test_image
dd if=/dev/zero bs=1M count=0 seek=64 of=test.img
parted -s test.img mklabel gpt
parted -s test.img mkpart primary 2048s 6143s
parted -s test.img mkpart primary 6144s 131038s
sudo losetup -Pf --show test.img > loopback_dev
sudo mkfs.fat -F 32 `cat loopback_dev`p2
sudo mount `cat loopback_dev`p2 test_image
sudo mkdir test_image/boot
sudo cp test/test.elf test_image/boot/
sudo cp test/qloader2.cfg test_image/
sync
sudo umount test_image/
sudo losetup -d `cat loopback_dev`
rm -rf test_image loopback_dev
./qloader2-install src/qloader2.bin test.img 2048
qemu-system-x86_64 -hda test.img -debugcon stdio

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qloader2.bin
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313
src/fs/fat32.c Normal file
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@ -0,0 +1,313 @@
#include <fs/fat32.h>
#include <lib/blib.h>
#include <drivers/disk.h>
#include <lib/libc.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 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, int disk, int partition) {
context->drive = disk;
get_part(&context->part, disk, partition);
struct fat32_bpb bpb;
read_partition(disk, &context->part, &bpb, 0, sizeof(struct fat32_bpb));
if (bpb.signature != FAT32_VALID_SIGNATURE_1 && bpb.signature != FAT32_VALID_SIGNATURE_2) {
return 1;
}
if (strncmp(bpb.system_identifier, FAT32_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) != 0) {
return 1;
}
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 = bpb.sectors_per_fat_32;
context->root_directory_cluster = bpb.root_directory_cluster;
context->fat_start_lba = bpb.reserved_sectors + bpb.hidden_sectors_count;
context->data_start_lba = context->fat_start_lba + bpb.fats_count * bpb.sectors_per_fat_32;
return 0;
}
static int fat32_read_cluster_from_map(struct fat32_context* context, uint32_t cluster, uint32_t* out) {
const uint32_t sector = cluster / (FAT32_SECTOR_SIZE / 4);
const uint32_t offset = cluster % (FAT32_SECTOR_SIZE / 4);
uint32_t clusters[FAT32_SECTOR_SIZE / sizeof(uint32_t)];
int r = read_partition(context->drive, &context->part, &clusters[0], (context->fat_start_lba + sector) * FAT32_SECTOR_SIZE, sizeof(clusters));
if (r) {
return r;
}
*out = clusters[offset] & 0x0FFFFFFF;
return 0;
}
static int fat32_load_fat_cluster_to_memory(struct fat32_context* context, uint32_t cluster_number, void* buffer, uint32_t offset, uint32_t limit) {
const uint32_t sector = context->data_start_lba + (cluster_number - 2) * context->sectors_per_cluster;
return read_partition(context->drive, &context->part, buffer, ((uint64_t) sector) * FAT32_SECTOR_SIZE + offset, limit);
}
// 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 int fat32_open_in(struct fat32_context* context, struct fat32_directory_entry* directory, struct fat32_directory_entry* file, const char* name) {
int error;
uint32_t current_cluster_number = directory->cluster_num_high << 16 | directory->cluster_num_low;
char current_lfn[FAT32_LFN_MAX_FILENAME_LENGTH] = {0};
bool has_lfn = false;
do {
struct fat32_directory_entry directory_entries[FAT32_SECTOR_SIZE / sizeof(struct fat32_directory_entry)];
error = fat32_load_fat_cluster_to_memory(context, current_cluster_number, directory_entries, 0, sizeof(directory_entries));
if (error != 0) {
return error;
}
for (unsigned int i = 0; i < SIZEOF_ARRAY(directory_entries); i++) {
if (directory_entries[i].file_name_and_ext[0] == 0x00) {
// no more entries here
break;
}
if (directory_entries[i].attribute == FAT32_LFN_ATTRIBUTE) {
has_lfn = true;
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);
continue;
}
if (has_lfn) {
// 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 ((has_lfn && strcmp(current_lfn, name) == 0) || strncmp(directory_entries[i].file_name_and_ext, name, 8 + 3) == 0) {
*file = directory_entries[i];
return 0;
}
if (has_lfn) {
has_lfn = false;
}
}
error = fat32_read_cluster_from_map(context, current_cluster_number, &current_cluster_number);
if (error != 0) {
return error;
}
} while (current_cluster_number >= 0x00000002 && current_cluster_number <= 0x0FFFFEF);
// file not found
return -1;
}
int fat32_check_signature(int disk, int partition) {
struct fat32_context context;
return fat32_init_context(&context, disk, partition) == 0;
}
int fat32_open(struct fat32_file_handle* ret, int disk, int partition, const char* path) {
struct fat32_context context;
int r = fat32_init_context(&context, disk, partition);
if (r) {
print("fat32: context init failure (%d)\n", r);
return r;
}
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
current_directory.cluster_num_low = context.root_directory_cluster & 0xFFFF;
current_directory.cluster_num_high = context.root_directory_cluster >> 16;
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) {
print("fat32: file %s not found\n", path);
return r;
}
if (expect_directory) {
current_directory = current_file;
} else {
ret->context = context;
ret->first_cluster = current_file.cluster_num_high << 16 | current_file.cluster_num_low;
ret->size_clusters = DIV_ROUNDUP(current_file.file_size_bytes, FAT32_SECTOR_SIZE);
ret->size_bytes = current_file.file_size_bytes;
return 0;
}
}
}
int fat32_read(struct fat32_file_handle* file, void* buf, uint64_t loc, uint64_t count) {
int r;
uint32_t cluster_size = file->context.sectors_per_cluster * FAT32_SECTOR_SIZE;
uint32_t current_cluster_number = file->first_cluster;
// skip first clusters
while (loc >= cluster_size) {
r = fat32_read_cluster_from_map(&file->context, current_cluster_number, &current_cluster_number);
if (r != 0) {
print("fat32: failed to read cluster %x from map\n", current_cluster_number);
return r;
}
loc -= cluster_size;
}
uint64_t readTotal = 0;
do {
// find largest read size
uint64_t current_read = count;
if (current_read > cluster_size - loc) {
current_read = cluster_size - loc;
}
r = fat32_load_fat_cluster_to_memory(&file->context, current_cluster_number, buf + readTotal, loc, current_read);
if (r != 0) {
print("fat32: failed to load cluster %x to memory\n", current_cluster_number);
return r;
}
loc = 0;
count -= current_read;
readTotal += current_read;
if (count == 0) {
return 0;
}
// fetch next cluster number
r = fat32_read_cluster_from_map(&file->context, current_cluster_number, &current_cluster_number);
if (r != 0) {
print("fat32: failed to read cluster %x from map\n", current_cluster_number);
return r;
}
} while (current_cluster_number >= 0x00000002 && current_cluster_number <= 0x0FFFFEF);
print("fat32: read failed, unexpected end of cluster chain\n");
return 0;
}

32
src/fs/fat32.h Normal file
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@ -0,0 +1,32 @@
#ifndef __FS__FAT32_H__
#define __FS__FAT32_H__
#include <stdint.h>
#include <lib/part.h>
struct fat32_context {
int drive;
struct part part;
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 root_directory_cluster;
uint32_t fat_start_lba;
uint32_t data_start_lba;
};
struct fat32_file_handle {
struct fat32_context context;
uint32_t first_cluster;
uint32_t size_bytes;
uint32_t size_clusters;
};
int fat32_check_signature(int disk, int partition);
int fat32_open(struct fat32_file_handle *ret, int disk, int partition, const char *path);
int fat32_read(struct fat32_file_handle *file, void *buf, uint64_t loc, uint64_t count);
#endif

18
src/fs/file.c
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@ -3,6 +3,7 @@
#include <fs/file.h> #include <fs/file.h>
#include <fs/echfs.h> #include <fs/echfs.h>
#include <fs/ext2fs.h> #include <fs/ext2fs.h>
#include <fs/fat32.h>
#include <lib/blib.h> #include <lib/blib.h>
int fopen(struct file_handle *ret, int disk, int partition, const char *filename) { int fopen(struct file_handle *ret, int disk, int partition, const char *filename) {
@ -38,6 +39,23 @@ int fopen(struct file_handle *ret, int disk, int partition, const char *filename
return 0; return 0;
} }
if (fat32_check_signature(disk, partition)) {
struct fat32_file_handle *fd = balloc(sizeof(struct fat32_file_handle));
int r = fat32_open(fd, disk, partition, filename);
if (r)
return r;
ret->fd = (void *)fd;
ret->read = (void *)fat32_read;
ret->disk = disk;
ret->partition = partition;
ret->size = fd->size_bytes;
return 0;
}
return -1; return -1;
} }

2
src/lib/blib.h
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@ -32,4 +32,6 @@ uint64_t strtoui(const char *s);
typedef void *symbol[]; typedef void *symbol[];
#define SIZEOF_ARRAY(array) (sizeof(array) / sizeof(array[0]))
#endif #endif