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Diffstat (limited to 'tests/qemu-iotests/fat16.py')
| -rw-r--r-- | tests/qemu-iotests/fat16.py | 690 |
1 files changed, 690 insertions, 0 deletions
diff --git a/tests/qemu-iotests/fat16.py b/tests/qemu-iotests/fat16.py new file mode 100644 index 0000000..7d2d052 --- /dev/null +++ b/tests/qemu-iotests/fat16.py @@ -0,0 +1,690 @@ +# A simple FAT16 driver that is used to test the `vvfat` driver in QEMU. +# +# Copyright (C) 2024 Amjad Alsharafi <amjadsharafi10@gmail.com> +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 2 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. + +from typing import Callable, List, Optional, Protocol, Set +import string + +SECTOR_SIZE = 512 +DIRENTRY_SIZE = 32 +ALLOWED_FILE_CHARS = set( + "!#$%&'()-@^_`{}~" + string.digits + string.ascii_uppercase +) + + +class MBR: + def __init__(self, data: bytes): + assert len(data) == 512 + self.partition_table = [] + for i in range(4): + partition = data[446 + i * 16 : 446 + (i + 1) * 16] + self.partition_table.append( + { + "status": partition[0], + "start_head": partition[1], + "start_sector": partition[2] & 0x3F, + "start_cylinder": ((partition[2] & 0xC0) << 2) + | partition[3], + "type": partition[4], + "end_head": partition[5], + "end_sector": partition[6] & 0x3F, + "end_cylinder": ((partition[6] & 0xC0) << 2) + | partition[7], + "start_lba": int.from_bytes(partition[8:12], "little"), + "size": int.from_bytes(partition[12:16], "little"), + } + ) + + def __str__(self): + return "\n".join( + [ + f"{i}: {partition}" + for i, partition in enumerate(self.partition_table) + ] + ) + + +class FatBootSector: + # pylint: disable=too-many-instance-attributes + def __init__(self, data: bytes): + assert len(data) == 512 + self.bytes_per_sector = int.from_bytes(data[11:13], "little") + self.sectors_per_cluster = data[13] + self.reserved_sectors = int.from_bytes(data[14:16], "little") + self.fat_count = data[16] + self.root_entries = int.from_bytes(data[17:19], "little") + total_sectors_16 = int.from_bytes(data[19:21], "little") + self.media_descriptor = data[21] + self.sectors_per_fat = int.from_bytes(data[22:24], "little") + self.sectors_per_track = int.from_bytes(data[24:26], "little") + self.heads = int.from_bytes(data[26:28], "little") + self.hidden_sectors = int.from_bytes(data[28:32], "little") + total_sectors_32 = int.from_bytes(data[32:36], "little") + assert ( + total_sectors_16 == 0 or total_sectors_32 == 0 + ), "Both total sectors (16 and 32) fields are non-zero" + self.total_sectors = total_sectors_16 or total_sectors_32 + self.drive_number = data[36] + self.volume_id = int.from_bytes(data[39:43], "little") + self.volume_label = data[43:54].decode("ascii").strip() + self.fs_type = data[54:62].decode("ascii").strip() + + def root_dir_start(self): + """ + Calculate the start sector of the root directory. + """ + return self.reserved_sectors + self.fat_count * self.sectors_per_fat + + def root_dir_size(self): + """ + Calculate the size of the root directory in sectors. + """ + return ( + self.root_entries * DIRENTRY_SIZE + self.bytes_per_sector - 1 + ) // self.bytes_per_sector + + def data_sector_start(self): + """ + Calculate the start sector of the data region. + """ + return self.root_dir_start() + self.root_dir_size() + + def first_sector_of_cluster(self, cluster: int) -> int: + """ + Calculate the first sector of the given cluster. + """ + return ( + self.data_sector_start() + (cluster - 2) * self.sectors_per_cluster + ) + + def cluster_bytes(self): + """ + Calculate the number of bytes in a cluster. + """ + return self.bytes_per_sector * self.sectors_per_cluster + + def __str__(self): + return ( + f"Bytes per sector: {self.bytes_per_sector}\n" + f"Sectors per cluster: {self.sectors_per_cluster}\n" + f"Reserved sectors: {self.reserved_sectors}\n" + f"FAT count: {self.fat_count}\n" + f"Root entries: {self.root_entries}\n" + f"Total sectors: {self.total_sectors}\n" + f"Media descriptor: {self.media_descriptor}\n" + f"Sectors per FAT: {self.sectors_per_fat}\n" + f"Sectors per track: {self.sectors_per_track}\n" + f"Heads: {self.heads}\n" + f"Hidden sectors: {self.hidden_sectors}\n" + f"Drive number: {self.drive_number}\n" + f"Volume ID: {self.volume_id}\n" + f"Volume label: {self.volume_label}\n" + f"FS type: {self.fs_type}\n" + ) + + +class FatDirectoryEntry: + # pylint: disable=too-many-instance-attributes + def __init__(self, data: bytes, sector: int, offset: int): + self.name = data[0:8].decode("ascii").strip() + self.ext = data[8:11].decode("ascii").strip() + self.attributes = data[11] + self.reserved = data[12] + self.create_time_tenth = data[13] + self.create_time = int.from_bytes(data[14:16], "little") + self.create_date = int.from_bytes(data[16:18], "little") + self.last_access_date = int.from_bytes(data[18:20], "little") + high_cluster = int.from_bytes(data[20:22], "little") + self.last_mod_time = int.from_bytes(data[22:24], "little") + self.last_mod_date = int.from_bytes(data[24:26], "little") + low_cluster = int.from_bytes(data[26:28], "little") + self.cluster = (high_cluster << 16) | low_cluster + self.size_bytes = int.from_bytes(data[28:32], "little") + + # extra (to help write back to disk) + self.sector = sector + self.offset = offset + + def as_bytes(self) -> bytes: + return ( + self.name.ljust(8, " ").encode("ascii") + + self.ext.ljust(3, " ").encode("ascii") + + self.attributes.to_bytes(1, "little") + + self.reserved.to_bytes(1, "little") + + self.create_time_tenth.to_bytes(1, "little") + + self.create_time.to_bytes(2, "little") + + self.create_date.to_bytes(2, "little") + + self.last_access_date.to_bytes(2, "little") + + (self.cluster >> 16).to_bytes(2, "little") + + self.last_mod_time.to_bytes(2, "little") + + self.last_mod_date.to_bytes(2, "little") + + (self.cluster & 0xFFFF).to_bytes(2, "little") + + self.size_bytes.to_bytes(4, "little") + ) + + def whole_name(self): + if self.ext: + return f"{self.name}.{self.ext}" + else: + return self.name + + def __str__(self): + return ( + f"Name: {self.name}\n" + f"Ext: {self.ext}\n" + f"Attributes: {self.attributes}\n" + f"Reserved: {self.reserved}\n" + f"Create time tenth: {self.create_time_tenth}\n" + f"Create time: {self.create_time}\n" + f"Create date: {self.create_date}\n" + f"Last access date: {self.last_access_date}\n" + f"Last mod time: {self.last_mod_time}\n" + f"Last mod date: {self.last_mod_date}\n" + f"Cluster: {self.cluster}\n" + f"Size: {self.size_bytes}\n" + ) + + def __repr__(self): + # convert to dict + return str(vars(self)) + + +class SectorReader(Protocol): + def __call__(self, start_sector: int, num_sectors: int = 1) -> bytes: ... + +# pylint: disable=broad-exception-raised +class Fat16: + def __init__( + self, + start_sector: int, + size: int, + sector_reader: SectorReader, + sector_writer: Callable[[int, bytes], None] + ): + self.start_sector = start_sector + self.size_in_sectors = size + self.sector_reader = sector_reader + self.sector_writer = sector_writer + + self.boot_sector = FatBootSector(self.sector_reader(start_sector, 1)) + + fat_size_in_sectors = ( + self.boot_sector.sectors_per_fat * self.boot_sector.fat_count + ) + self.fats = self.read_sectors( + self.boot_sector.reserved_sectors, fat_size_in_sectors + ) + self.fats_dirty_sectors: Set[int] = set() + + def read_sectors(self, start_sector: int, num_sectors: int) -> bytes: + return self.sector_reader(start_sector + self.start_sector, + num_sectors) + + def write_sectors(self, start_sector: int, data: bytes) -> None: + return self.sector_writer(start_sector + self.start_sector, data) + + def directory_from_bytes( + self, data: bytes, start_sector: int + ) -> List[FatDirectoryEntry]: + """ + Convert `bytes` into a list of `FatDirectoryEntry` objects. + Will ignore long file names. + Will stop when it encounters a 0x00 byte. + """ + + entries = [] + for i in range(0, len(data), DIRENTRY_SIZE): + entry = data[i : i + DIRENTRY_SIZE] + + current_sector = start_sector + (i // SECTOR_SIZE) + current_offset = i % SECTOR_SIZE + + if entry[0] == 0: + break + + if entry[0] == 0xE5: + # Deleted file + continue + + if entry[11] & 0xF == 0xF: + # Long file name + continue + + entries.append( + FatDirectoryEntry(entry, current_sector, current_offset) + ) + return entries + + def read_root_directory(self) -> List[FatDirectoryEntry]: + root_dir = self.read_sectors( + self.boot_sector.root_dir_start(), self.boot_sector.root_dir_size() + ) + return self.directory_from_bytes( + root_dir, self.boot_sector.root_dir_start() + ) + + def read_fat_entry(self, cluster: int) -> int: + """ + Read the FAT entry for the given cluster. + """ + fat_offset = cluster * 2 # FAT16 + return int.from_bytes(self.fats[fat_offset : fat_offset + 2], "little") + + def write_fat_entry(self, cluster: int, value: int) -> None: + """ + Write the FAT entry for the given cluster. + """ + fat_offset = cluster * 2 + self.fats = ( + self.fats[:fat_offset] + + value.to_bytes(2, "little") + + self.fats[fat_offset + 2 :] + ) + self.fats_dirty_sectors.add(fat_offset // SECTOR_SIZE) + + def flush_fats(self) -> None: + """ + Write the FATs back to the disk. + """ + for sector in self.fats_dirty_sectors: + data = self.fats[sector * SECTOR_SIZE : (sector + 1) * SECTOR_SIZE] + sector = self.boot_sector.reserved_sectors + sector + self.write_sectors(sector, data) + self.fats_dirty_sectors = set() + + def next_cluster(self, cluster: int) -> Optional[int]: + """ + Get the next cluster in the chain. + If its `None`, then its the last cluster. + The function will crash if the next cluster + is `FREE` (unexpected) or invalid entry. + """ + fat_entry = self.read_fat_entry(cluster) + if fat_entry == 0: + raise Exception("Unexpected: FREE cluster") + if fat_entry == 1: + raise Exception("Unexpected: RESERVED cluster") + if fat_entry >= 0xFFF8: + return None + if fat_entry >= 0xFFF7: + raise Exception("Invalid FAT entry") + + return fat_entry + + def next_free_cluster(self) -> int: + """ + Find the next free cluster. + """ + # simple linear search + for i in range(2, 0xFFFF): + if self.read_fat_entry(i) == 0: + return i + raise Exception("No free clusters") + + def next_free_cluster_non_continuous(self) -> int: + """ + Find the next free cluster, but makes sure + that the cluster before and after it are not allocated. + """ + # simple linear search + before = False + for i in range(2, 0xFFFF): + if self.read_fat_entry(i) == 0: + if before and self.read_fat_entry(i + 1) == 0: + return i + else: + before = True + else: + before = False + + raise Exception("No free clusters") + + def read_cluster(self, cluster: int) -> bytes: + """ + Read the cluster at the given cluster. + """ + return self.read_sectors( + self.boot_sector.first_sector_of_cluster(cluster), + self.boot_sector.sectors_per_cluster, + ) + + def write_cluster(self, cluster: int, data: bytes) -> None: + """ + Write the cluster at the given cluster. + """ + assert len(data) == self.boot_sector.cluster_bytes() + self.write_sectors( + self.boot_sector.first_sector_of_cluster(cluster), + data, + ) + + def read_directory( + self, cluster: Optional[int] + ) -> List[FatDirectoryEntry]: + """ + Read the directory at the given cluster. + """ + entries = [] + while cluster is not None: + data = self.read_cluster(cluster) + entries.extend( + self.directory_from_bytes( + data, self.boot_sector.first_sector_of_cluster(cluster) + ) + ) + cluster = self.next_cluster(cluster) + return entries + + def add_direntry( + self, cluster: Optional[int], name: str, ext: str, attributes: int + ) -> FatDirectoryEntry: + """ + Add a new directory entry to the given cluster. + If the cluster is `None`, then it will be added to the root directory. + """ + + def find_free_entry(data: bytes) -> Optional[int]: + for i in range(0, len(data), DIRENTRY_SIZE): + entry = data[i : i + DIRENTRY_SIZE] + if entry[0] == 0 or entry[0] == 0xE5: + return i + return None + + assert len(name) <= 8, "Name must be 8 characters or less" + assert len(ext) <= 3, "Ext must be 3 characters or less" + assert attributes % 0x15 != 0x15, "Invalid attributes" + + # initial dummy data + new_entry = FatDirectoryEntry(b"\0" * 32, 0, 0) + new_entry.name = name.ljust(8, " ") + new_entry.ext = ext.ljust(3, " ") + new_entry.attributes = attributes + new_entry.reserved = 0 + new_entry.create_time_tenth = 0 + new_entry.create_time = 0 + new_entry.create_date = 0 + new_entry.last_access_date = 0 + new_entry.last_mod_time = 0 + new_entry.last_mod_date = 0 + new_entry.cluster = self.next_free_cluster() + new_entry.size_bytes = 0 + + # mark as EOF + self.write_fat_entry(new_entry.cluster, 0xFFFF) + + if cluster is None: + for i in range(self.boot_sector.root_dir_size()): + sector_data = self.read_sectors( + self.boot_sector.root_dir_start() + i, 1 + ) + offset = find_free_entry(sector_data) + if offset is not None: + new_entry.sector = self.boot_sector.root_dir_start() + i + new_entry.offset = offset + self.update_direntry(new_entry) + return new_entry + else: + while cluster is not None: + data = self.read_cluster(cluster) + offset = find_free_entry(data) + if offset is not None: + new_entry.sector = ( + self.boot_sector.first_sector_of_cluster(cluster) + + (offset // SECTOR_SIZE)) + new_entry.offset = offset % SECTOR_SIZE + self.update_direntry(new_entry) + return new_entry + cluster = self.next_cluster(cluster) + + raise Exception("No free directory entries") + + def update_direntry(self, entry: FatDirectoryEntry) -> None: + """ + Write the directory entry back to the disk. + """ + sector = self.read_sectors(entry.sector, 1) + sector = ( + sector[: entry.offset] + + entry.as_bytes() + + sector[entry.offset + DIRENTRY_SIZE :] + ) + self.write_sectors(entry.sector, sector) + + def find_direntry(self, path: str) -> Optional[FatDirectoryEntry]: + """ + Find the directory entry for the given path. + """ + assert path[0] == "/", "Path must start with /" + + path = path[1:] # remove the leading / + parts = path.split("/") + directory = self.read_root_directory() + + current_entry = None + + for i, part in enumerate(parts): + is_last = i == len(parts) - 1 + + for entry in directory: + if entry.whole_name() == part: + current_entry = entry + break + if current_entry is None: + return None + + if is_last: + return current_entry + + if current_entry.attributes & 0x10 == 0: + raise Exception( + f"{current_entry.whole_name()} is not a directory" + ) + + directory = self.read_directory(current_entry.cluster) + + assert False, "Exited loop with is_last == False" + + def read_file(self, entry: Optional[FatDirectoryEntry]) -> Optional[bytes]: + """ + Read the content of the file at the given path. + """ + if entry is None: + return None + if entry.attributes & 0x10 != 0: + raise Exception(f"{entry.whole_name()} is a directory") + + data = b"" + cluster: Optional[int] = entry.cluster + while cluster is not None and len(data) <= entry.size_bytes: + data += self.read_cluster(cluster) + cluster = self.next_cluster(cluster) + return data[: entry.size_bytes] + + def truncate_file( + self, + entry: FatDirectoryEntry, + new_size: int, + allocate_non_continuous: bool = False, + ) -> None: + """ + Truncate the file at the given path to the new size. + """ + if entry is None: + raise Exception("entry is None") + if entry.attributes & 0x10 != 0: + raise Exception(f"{entry.whole_name()} is a directory") + + def clusters_from_size(size: int) -> int: + return ( + size + self.boot_sector.cluster_bytes() - 1 + ) // self.boot_sector.cluster_bytes() + + # First, allocate new FATs if we need to + required_clusters = clusters_from_size(new_size) + current_clusters = clusters_from_size(entry.size_bytes) + + affected_clusters = set() + + # Keep at least one cluster, easier to manage this way + if required_clusters == 0: + required_clusters = 1 + if current_clusters == 0: + current_clusters = 1 + + cluster: Optional[int] + + if required_clusters > current_clusters: + # Allocate new clusters + cluster = entry.cluster + to_add = required_clusters + for _ in range(current_clusters - 1): + to_add -= 1 + assert cluster is not None, "Cluster is None" + affected_clusters.add(cluster) + cluster = self.next_cluster(cluster) + assert required_clusters > 0, "No new clusters to allocate" + assert cluster is not None, "Cluster is None" + assert ( + self.next_cluster(cluster) is None + ), "Cluster is not the last cluster" + + # Allocate new clusters + for _ in range(to_add - 1): + if allocate_non_continuous: + new_cluster = self.next_free_cluster_non_continuous() + else: + new_cluster = self.next_free_cluster() + self.write_fat_entry(cluster, new_cluster) + self.write_fat_entry(new_cluster, 0xFFFF) + cluster = new_cluster + + elif required_clusters < current_clusters: + # Truncate the file + cluster = entry.cluster + for _ in range(required_clusters - 1): + assert cluster is not None, "Cluster is None" + cluster = self.next_cluster(cluster) + assert cluster is not None, "Cluster is None" + + next_cluster = self.next_cluster(cluster) + # mark last as EOF + self.write_fat_entry(cluster, 0xFFFF) + # free the rest + while next_cluster is not None: + cluster = next_cluster + next_cluster = self.next_cluster(next_cluster) + self.write_fat_entry(cluster, 0) + + self.flush_fats() + + # verify number of clusters + cluster = entry.cluster + count = 0 + while cluster is not None: + count += 1 + affected_clusters.add(cluster) + cluster = self.next_cluster(cluster) + assert ( + count == required_clusters + ), f"Expected {required_clusters} clusters, got {count}" + + # update the size + entry.size_bytes = new_size + self.update_direntry(entry) + + # trigger every affected cluster + for cluster in affected_clusters: + first_sector = self.boot_sector.first_sector_of_cluster(cluster) + first_sector_data = self.read_sectors(first_sector, 1) + self.write_sectors(first_sector, first_sector_data) + + def write_file(self, entry: FatDirectoryEntry, data: bytes) -> None: + """ + Write the content of the file at the given path. + """ + if entry is None: + raise Exception("entry is None") + if entry.attributes & 0x10 != 0: + raise Exception(f"{entry.whole_name()} is a directory") + + data_len = len(data) + + self.truncate_file(entry, data_len) + + cluster: Optional[int] = entry.cluster + while cluster is not None: + data_to_write = data[: self.boot_sector.cluster_bytes()] + if len(data_to_write) < self.boot_sector.cluster_bytes(): + old_data = self.read_cluster(cluster) + data_to_write += old_data[len(data_to_write) :] + + self.write_cluster(cluster, data_to_write) + data = data[self.boot_sector.cluster_bytes() :] + if len(data) == 0: + break + cluster = self.next_cluster(cluster) + + assert ( + len(data) == 0 + ), "Data was not written completely, clusters missing" + + def create_file(self, path: str) -> Optional[FatDirectoryEntry]: + """ + Create a new file at the given path. + """ + assert path[0] == "/", "Path must start with /" + + path = path[1:] # remove the leading / + + parts = path.split("/") + + directory_cluster = None + directory = self.read_root_directory() + + parts, filename = parts[:-1], parts[-1] + + for _, part in enumerate(parts): + current_entry = None + for entry in directory: + if entry.whole_name() == part: + current_entry = entry + break + if current_entry is None: + return None + + if current_entry.attributes & 0x10 == 0: + raise Exception( + f"{current_entry.whole_name()} is not a directory" + ) + + directory = self.read_directory(current_entry.cluster) + directory_cluster = current_entry.cluster + + # add new entry to the directory + + filename, ext = filename.split(".") + + if len(ext) > 3: + raise Exception("Ext must be 3 characters or less") + if len(filename) > 8: + raise Exception("Name must be 8 characters or less") + + for c in filename + ext: + + if c not in ALLOWED_FILE_CHARS: + raise Exception("Invalid character in filename") + + return self.add_direntry(directory_cluster, filename, ext, 0) |