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Move Boot Sector/BPB related code to boot_sector.rs

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Rafał Harabień 2018-12-08 17:17:08 +01:00
parent 15b45f2457
commit 1768b0fe7e
3 changed files with 648 additions and 635 deletions
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src/boot_sector.rs Normal file
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use core::cmp;
use io;
use io::prelude::*;
use io::{Error, ErrorKind};
use byteorder::LittleEndian;
use byteorder_ext::{ReadBytesExt, WriteBytesExt};
use dir_entry::DIR_ENTRY_SIZE;
use fs::{FatType, FsStatusFlags, FormatVolumeOptions};
use table::RESERVED_FAT_ENTRIES;
#[allow(dead_code)]
#[derive(Default, Debug, Clone)]
pub(crate) struct BiosParameterBlock {
pub(crate) bytes_per_sector: u16,
pub(crate) sectors_per_cluster: u8,
pub(crate) reserved_sectors: u16,
pub(crate) fats: u8,
pub(crate) root_entries: u16,
pub(crate) total_sectors_16: u16,
pub(crate) media: u8,
pub(crate) sectors_per_fat_16: u16,
pub(crate) sectors_per_track: u16,
pub(crate) heads: u16,
pub(crate) hidden_sectors: u32,
pub(crate) total_sectors_32: u32,
// Extended BIOS Parameter Block
pub(crate) sectors_per_fat_32: u32,
pub(crate) extended_flags: u16,
pub(crate) fs_version: u16,
pub(crate) root_dir_first_cluster: u32,
pub(crate) fs_info_sector: u16,
pub(crate) backup_boot_sector: u16,
pub(crate) reserved_0: [u8; 12],
pub(crate) drive_num: u8,
pub(crate) reserved_1: u8,
pub(crate) ext_sig: u8,
pub(crate) volume_id: u32,
pub(crate) volume_label: [u8; 11],
pub(crate) fs_type_label: [u8; 8],
}
impl BiosParameterBlock {
fn deserialize<T: Read>(rdr: &mut T) -> io::Result<BiosParameterBlock> {
let mut bpb: BiosParameterBlock = Default::default();
bpb.bytes_per_sector = rdr.read_u16::<LittleEndian>()?;
bpb.sectors_per_cluster = rdr.read_u8()?;
bpb.reserved_sectors = rdr.read_u16::<LittleEndian>()?;
bpb.fats = rdr.read_u8()?;
bpb.root_entries = rdr.read_u16::<LittleEndian>()?;
bpb.total_sectors_16 = rdr.read_u16::<LittleEndian>()?;
bpb.media = rdr.read_u8()?;
bpb.sectors_per_fat_16 = rdr.read_u16::<LittleEndian>()?;
bpb.sectors_per_track = rdr.read_u16::<LittleEndian>()?;
bpb.heads = rdr.read_u16::<LittleEndian>()?;
bpb.hidden_sectors = rdr.read_u32::<LittleEndian>()?;
bpb.total_sectors_32 = rdr.read_u32::<LittleEndian>()?;
if bpb.is_fat32() {
bpb.sectors_per_fat_32 = rdr.read_u32::<LittleEndian>()?;
bpb.extended_flags = rdr.read_u16::<LittleEndian>()?;
bpb.fs_version = rdr.read_u16::<LittleEndian>()?;
bpb.root_dir_first_cluster = rdr.read_u32::<LittleEndian>()?;
bpb.fs_info_sector = rdr.read_u16::<LittleEndian>()?;
bpb.backup_boot_sector = rdr.read_u16::<LittleEndian>()?;
rdr.read_exact(&mut bpb.reserved_0)?;
bpb.drive_num = rdr.read_u8()?;
bpb.reserved_1 = rdr.read_u8()?;
bpb.ext_sig = rdr.read_u8()?; // 0x29
bpb.volume_id = rdr.read_u32::<LittleEndian>()?;
rdr.read_exact(&mut bpb.volume_label)?;
rdr.read_exact(&mut bpb.fs_type_label)?;
} else {
bpb.drive_num = rdr.read_u8()?;
bpb.reserved_1 = rdr.read_u8()?;
bpb.ext_sig = rdr.read_u8()?; // 0x29
bpb.volume_id = rdr.read_u32::<LittleEndian>()?;
rdr.read_exact(&mut bpb.volume_label)?;
rdr.read_exact(&mut bpb.fs_type_label)?;
}
// when the extended boot signature is anything other than 0x29, the fields are invalid
if bpb.ext_sig != 0x29 {
// fields after ext_sig are not used - clean them
bpb.volume_id = 0;
bpb.volume_label = [0; 11];
bpb.fs_type_label = [0; 8];
}
Ok(bpb)
}
fn serialize<T: Write>(&self, mut wrt: T) -> io::Result<()> {
wrt.write_u16::<LittleEndian>(self.bytes_per_sector)?;
wrt.write_u8(self.sectors_per_cluster)?;
wrt.write_u16::<LittleEndian>(self.reserved_sectors)?;
wrt.write_u8(self.fats)?;
wrt.write_u16::<LittleEndian>(self.root_entries)?;
wrt.write_u16::<LittleEndian>(self.total_sectors_16)?;
wrt.write_u8(self.media)?;
wrt.write_u16::<LittleEndian>(self.sectors_per_fat_16)?;
wrt.write_u16::<LittleEndian>(self.sectors_per_track)?;
wrt.write_u16::<LittleEndian>(self.heads)?;
wrt.write_u32::<LittleEndian>(self.hidden_sectors)?;
wrt.write_u32::<LittleEndian>(self.total_sectors_32)?;
if self.is_fat32() {
wrt.write_u32::<LittleEndian>(self.sectors_per_fat_32)?;
wrt.write_u16::<LittleEndian>(self.extended_flags)?;
wrt.write_u16::<LittleEndian>(self.fs_version)?;
wrt.write_u32::<LittleEndian>(self.root_dir_first_cluster)?;
wrt.write_u16::<LittleEndian>(self.fs_info_sector)?;
wrt.write_u16::<LittleEndian>(self.backup_boot_sector)?;
wrt.write_all(&self.reserved_0)?;
wrt.write_u8(self.drive_num)?;
wrt.write_u8(self.reserved_1)?;
wrt.write_u8(self.ext_sig)?; // 0x29
wrt.write_u32::<LittleEndian>(self.volume_id)?;
wrt.write_all(&self.volume_label)?;
wrt.write_all(&self.fs_type_label)?;
} else {
wrt.write_u8(self.drive_num)?;
wrt.write_u8(self.reserved_1)?;
wrt.write_u8(self.ext_sig)?; // 0x29
wrt.write_u32::<LittleEndian>(self.volume_id)?;
wrt.write_all(&self.volume_label)?;
wrt.write_all(&self.fs_type_label)?;
}
Ok(())
}
fn validate(&self) -> io::Result<()> {
// sanity checks
if self.bytes_per_sector.count_ones() != 1 {
return Err(Error::new(
ErrorKind::Other,
"invalid bytes_per_sector value in BPB (not power of two)",
));
} else if self.bytes_per_sector < 512 {
return Err(Error::new(ErrorKind::Other, "invalid bytes_per_sector value in BPB (value < 512)"));
} else if self.bytes_per_sector > 4096 {
return Err(Error::new(ErrorKind::Other, "invalid bytes_per_sector value in BPB (value > 4096)"));
}
if self.sectors_per_cluster.count_ones() != 1 {
return Err(Error::new(
ErrorKind::Other,
"invalid sectors_per_cluster value in BPB (not power of two)",
));
} else if self.sectors_per_cluster < 1 {
return Err(Error::new(ErrorKind::Other, "invalid sectors_per_cluster value in BPB (value < 1)"));
} else if self.sectors_per_cluster > 128 {
return Err(Error::new(
ErrorKind::Other,
"invalid sectors_per_cluster value in BPB (value > 128)",
));
}
// bytes per sector is u16, sectors per cluster is u8, so guaranteed no overflow in multiplication
let bytes_per_cluster = self.bytes_per_sector as u32 * self.sectors_per_cluster as u32;
let maximum_compatibility_bytes_per_cluster: u32 = 32 * 1024;
if bytes_per_cluster > maximum_compatibility_bytes_per_cluster {
// 32k is the largest value to maintain greatest compatibility
// Many implementations appear to support 64k per cluster, and some may support 128k or larger
// However, >32k is not as thoroughly tested...
warn!("fs compatibility: bytes_per_cluster value '{}' in BPB exceeds '{}', and thus may be incompatible with some implementations",
bytes_per_cluster, maximum_compatibility_bytes_per_cluster);
}
let is_fat32 = self.is_fat32();
if self.reserved_sectors < 1 {
return Err(Error::new(ErrorKind::Other, "invalid reserved_sectors value in BPB"));
} else if !is_fat32 && self.reserved_sectors != 1 {
// Microsoft document indicates fat12 and fat16 code exists that presume this value is 1
warn!(
"fs compatibility: reserved_sectors value '{}' in BPB is not '1', and thus is incompatible with some implementations",
self.reserved_sectors
);
}
if self.fats == 0 {
return Err(Error::new(ErrorKind::Other, "invalid fats value in BPB"));
} else if self.fats > 2 {
// Microsoft document indicates that few implementations support any values other than 1 or 2
warn!(
"fs compatibility: numbers of FATs '{}' in BPB is greater than '2', and thus is incompatible with some implementations",
self.fats
);
}
if is_fat32 && self.root_entries != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid root_entries value in BPB (should be zero for FAT32)",
));
}
if is_fat32 && self.total_sectors_16 != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid total_sectors_16 value in BPB (should be zero for FAT32)",
));
}
if (self.total_sectors_16 == 0) == (self.total_sectors_32 == 0) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors_16 or total_sectors_32 should be non-zero)",
));
}
if is_fat32 && self.sectors_per_fat_32 == 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid sectors_per_fat_32 value in BPB (should be non-zero for FAT32)",
));
}
if self.fs_version != 0 {
return Err(Error::new(ErrorKind::Other, "Unknown FS version"));
}
if self.total_sectors() <= self.first_data_sector() {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors field value is too small)",
));
}
let total_clusters = self.total_clusters();
let fat_type = FatType::from_clusters(total_clusters);
if is_fat32 != (fat_type == FatType::Fat32) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (result of FAT32 determination from total number of clusters and sectors_per_fat_16 field differs)",
));
}
let bits_per_fat_entry = fat_type.bits_per_fat_entry();
let total_fat_entries = self.sectors_per_fat() * self.bytes_per_sector as u32 * 8 / bits_per_fat_entry as u32;
if total_fat_entries - RESERVED_FAT_ENTRIES < total_clusters {
warn!("FAT is too small to compared to total number of clusters");
}
Ok(())
}
pub(crate) fn mirroring_enabled(&self) -> bool {
self.extended_flags & 0x80 == 0
}
pub(crate) fn active_fat(&self) -> u16 {
// The zero-based number of the active FAT is only valid if mirroring is disabled.
if self.mirroring_enabled() {
0
} else {
self.extended_flags & 0x0F
}
}
pub(crate) fn status_flags(&self) -> FsStatusFlags {
FsStatusFlags::decode(self.reserved_1)
}
pub(crate) fn is_fat32(&self) -> bool {
// because this field must be zero on FAT32, and
// because it must be non-zero on FAT12/FAT16,
// this provides a simple way to detect FAT32
self.sectors_per_fat_16 == 0
}
pub(crate) fn sectors_per_fat(&self) -> u32 {
if self.is_fat32() {
self.sectors_per_fat_32
} else {
self.sectors_per_fat_16 as u32
}
}
pub(crate) fn total_sectors(&self) -> u32 {
if self.total_sectors_16 == 0 {
self.total_sectors_32
} else {
self.total_sectors_16 as u32
}
}
pub(crate) fn root_dir_sectors(&self) -> u32 {
let root_dir_bytes = self.root_entries as u32 * DIR_ENTRY_SIZE as u32;
(root_dir_bytes + self.bytes_per_sector as u32 - 1) / self.bytes_per_sector as u32
}
pub(crate) fn sectors_per_all_fats(&self) -> u32 {
self.fats as u32 * self.sectors_per_fat()
}
pub(crate) fn first_data_sector(&self) -> u32 {
let root_dir_sectors = self.root_dir_sectors();
let fat_sectors = self.sectors_per_all_fats();
self.reserved_sectors as u32 + fat_sectors + root_dir_sectors
}
pub(crate) fn total_clusters(&self) -> u32 {
let total_sectors = self.total_sectors();
let first_data_sector = self.first_data_sector();
let data_sectors = total_sectors - first_data_sector;
data_sectors / self.sectors_per_cluster as u32
}
}
#[allow(dead_code)]
pub(crate) struct BootRecord {
bootjmp: [u8; 3],
oem_name: [u8; 8],
pub(crate) bpb: BiosParameterBlock,
boot_code: [u8; 448],
boot_sig: [u8; 2],
}
impl BootRecord {
pub(crate) fn deserialize<T: Read>(rdr: &mut T) -> io::Result<BootRecord> {
let mut boot: BootRecord = Default::default();
rdr.read_exact(&mut boot.bootjmp)?;
rdr.read_exact(&mut boot.oem_name)?;
boot.bpb = BiosParameterBlock::deserialize(rdr)?;
if boot.bpb.is_fat32() {
rdr.read_exact(&mut boot.boot_code[0..420])?;
} else {
rdr.read_exact(&mut boot.boot_code[0..448])?;
}
rdr.read_exact(&mut boot.boot_sig)?;
Ok(boot)
}
pub(crate) fn serialize<T: Write>(&self, mut wrt: T) -> io::Result<()> {
wrt.write_all(&self.bootjmp)?;
wrt.write_all(&self.oem_name)?;
self.bpb.serialize(&mut wrt)?;
if self.bpb.is_fat32() {
wrt.write_all(&self.boot_code[0..420])?;
} else {
wrt.write_all(&self.boot_code[0..448])?;
}
wrt.write_all(&self.boot_sig)?;
Ok(())
}
pub(crate) fn validate(&self) -> io::Result<()> {
if self.boot_sig != [0x55, 0xAA] {
return Err(Error::new(ErrorKind::Other, "Invalid boot sector signature"));
}
if self.bootjmp[0] != 0xEB && self.bootjmp[0] != 0xE9 {
warn!("Unknown opcode {:x} in bootjmp boot sector field", self.bootjmp[0]);
}
self.bpb.validate()?;
Ok(())
}
}
impl Default for BootRecord {
fn default() -> BootRecord {
BootRecord {
bootjmp: Default::default(),
oem_name: Default::default(),
bpb: Default::default(),
boot_code: [0; 448],
boot_sig: Default::default(),
}
}
}
const KB: u64 = 1024;
const MB: u64 = KB * 1024;
const GB: u64 = MB * 1024;
pub(crate) fn determine_fat_type(total_bytes: u64) -> FatType {
if total_bytes < 4 * MB {
FatType::Fat12
} else if total_bytes < 512 * MB {
FatType::Fat16
} else {
FatType::Fat32
}
}
fn determine_bytes_per_cluster(total_bytes: u64, fat_type: FatType, bytes_per_sector: u16) -> u32 {
let bytes_per_cluster = match fat_type {
FatType::Fat12 => (total_bytes.next_power_of_two() / MB * 512) as u32,
FatType::Fat16 => {
if total_bytes <= 16 * MB {
1 * KB as u32
} else if total_bytes <= 128 * MB {
2 * KB as u32
} else {
(total_bytes.next_power_of_two() / (64 * MB) * KB) as u32
}
},
FatType::Fat32 => {
if total_bytes <= 260 * MB {
512
} else if total_bytes <= 8 * GB {
4 * KB as u32
} else {
(total_bytes.next_power_of_two() / (2 * GB) * KB) as u32
}
},
};
const MAX_CLUSTER_SIZE: u32 = 32 * KB as u32;
debug_assert!(bytes_per_cluster.is_power_of_two());
cmp::min(cmp::max(bytes_per_cluster, bytes_per_sector as u32), MAX_CLUSTER_SIZE)
}
fn determine_sectors_per_fat(total_sectors: u32, reserved_sectors: u16, fats: u8, root_dir_sectors: u32,
sectors_per_cluster: u8, fat_type: FatType) -> u32 {
// TODO: check if this calculation is always correct (especially for FAT12)
let tmp_val1 = total_sectors - (reserved_sectors as u32 + root_dir_sectors as u32);
let mut tmp_val2 = (256 * sectors_per_cluster as u32) + fats as u32;
if fat_type == FatType::Fat32 {
tmp_val2 = tmp_val2 / 2;
} else if fat_type == FatType::Fat12 {
tmp_val2 = tmp_val2 / 3 * 4
}
(tmp_val1 + (tmp_val2 - 1)) / tmp_val2
}
fn format_bpb(options: &FormatVolumeOptions) -> io::Result<(BiosParameterBlock, FatType)> {
// TODO: maybe total_sectors could be optional?
let bytes_per_sector = options.bytes_per_sector;
let total_sectors = options.total_sectors;
let total_bytes = total_sectors as u64 * bytes_per_sector as u64;
let fat_type = options.fat_type.unwrap_or_else(|| determine_fat_type(total_bytes));
let bytes_per_cluster = options.bytes_per_cluster
.unwrap_or_else(|| determine_bytes_per_cluster(total_bytes, fat_type, bytes_per_sector));
let sectors_per_cluster = (bytes_per_cluster / bytes_per_sector as u32) as u8;
// Note: most of implementations use 32 reserved sectors for FAT32 but it's wasting of space
// We use 4 because there are two boot sectors and one FS Info sector (1 sector remains unused)
let reserved_sectors: u16 = if fat_type == FatType::Fat32 { 4 } else { 1 };
let fats = 2u8;
let is_fat32 = fat_type == FatType::Fat32;
let root_entries = if is_fat32 { 0 } else { options.root_entries.unwrap_or(512) };
let root_dir_bytes = root_entries as u32 * DIR_ENTRY_SIZE as u32;
let root_dir_sectors = (root_dir_bytes + bytes_per_sector as u32 - 1) / bytes_per_sector as u32;
// Check if volume has enough space to accomodate reserved sectors, FAT, root directory and some data space
// Having less than 8 sectors for FAT and data would make a little sense
if total_sectors <= reserved_sectors as u32 + root_dir_sectors as u32 + 8 {
return Err(Error::new(ErrorKind::Other, "Volume is too small",));
}
// calculate File Allocation Table size
let sectors_per_fat = determine_sectors_per_fat(total_sectors, reserved_sectors, fats, root_dir_sectors,
sectors_per_cluster, fat_type);
// drive_num should be 0 for floppy disks and 0x80 for hard disks - determine it using FAT type
let drive_num = options.drive_num.unwrap_or_else(|| if fat_type == FatType::Fat12 { 0 } else { 0x80 });
// reserved_0 is always zero
let reserved_0 = [0u8; 12];
// setup volume label
let mut volume_label = [0u8; 11];
if let Some(volume_label_from_opts) = options.volume_label {
volume_label.copy_from_slice(&volume_label_from_opts);
} else {
volume_label.copy_from_slice("NO NAME ".as_bytes());
}
// setup fs_type_label field
let mut fs_type_label = [0u8; 8];
let fs_type_label_str = match fat_type {
FatType::Fat12 => "FAT12 ",
FatType::Fat16 => "FAT16 ",
FatType::Fat32 => "FAT32 ",
};
fs_type_label.copy_from_slice(fs_type_label_str.as_bytes());
// create Bios Parameter Block struct
let bpb = BiosParameterBlock {
bytes_per_sector,
sectors_per_cluster,
reserved_sectors,
fats,
root_entries,
total_sectors_16: if total_sectors < 0x10000 { total_sectors as u16 } else { 0 },
media: options.media.unwrap_or(0xF8),
sectors_per_fat_16: if is_fat32 { 0 } else { sectors_per_fat as u16 },
sectors_per_track: options.sectors_per_track.unwrap_or(0x20),
heads: options.heads.unwrap_or(0x40),
hidden_sectors: 0,
total_sectors_32: if total_sectors >= 0x10000 { total_sectors } else { 0 },
// FAT32 fields start
sectors_per_fat_32: if is_fat32 { sectors_per_fat } else { 0 },
extended_flags: 0, // mirroring enabled
fs_version: 0,
root_dir_first_cluster: if is_fat32 { 2 } else { 0 },
fs_info_sector: if is_fat32 { 1 } else { 0 },
backup_boot_sector: if is_fat32 { 6 } else { 0 },
reserved_0,
// FAT32 fields end
drive_num,
reserved_1: 0,
ext_sig: 0x29,
volume_id: options.volume_id.unwrap_or(0x12345678),
volume_label,
fs_type_label,
};
// Check if number of clusters is proper for used FAT type
if FatType::from_clusters(bpb.total_clusters()) != fat_type {
return Err(Error::new(ErrorKind::Other, "Total number of clusters and FAT type does not match. Try other volume size"));
}
Ok((bpb, fat_type))
}
pub(crate) fn format_boot_sector(options: &FormatVolumeOptions) -> io::Result<(BootRecord, FatType)> {
let mut boot: BootRecord = Default::default();
let (bpb, fat_type) = format_bpb(options)?;
boot.bpb = bpb;
boot.oem_name.copy_from_slice("MSWIN4.1".as_bytes());
// Boot code copied from FAT32 boot sector initialized by mkfs.fat
boot.bootjmp = [0xEB, 0x58, 0x90];
let boot_code: [u8; 129] = [
0x0E, 0x1F, 0xBE, 0x77, 0x7C, 0xAC, 0x22, 0xC0, 0x74, 0x0B, 0x56, 0xB4, 0x0E, 0xBB, 0x07, 0x00,
0xCD, 0x10, 0x5E, 0xEB, 0xF0, 0x32, 0xE4, 0xCD, 0x16, 0xCD, 0x19, 0xEB, 0xFE, 0x54, 0x68, 0x69,
0x73, 0x20, 0x69, 0x73, 0x20, 0x6E, 0x6F, 0x74, 0x20, 0x61, 0x20, 0x62, 0x6F, 0x6F, 0x74, 0x61,
0x62, 0x6C, 0x65, 0x20, 0x64, 0x69, 0x73, 0x6B, 0x2E, 0x20, 0x20, 0x50, 0x6C, 0x65, 0x61, 0x73,
0x65, 0x20, 0x69, 0x6E, 0x73, 0x65, 0x72, 0x74, 0x20, 0x61, 0x20, 0x62, 0x6F, 0x6F, 0x74, 0x61,
0x62, 0x6C, 0x65, 0x20, 0x66, 0x6C, 0x6F, 0x70, 0x70, 0x79, 0x20, 0x61, 0x6E, 0x64, 0x0D, 0x0A,
0x70, 0x72, 0x65, 0x73, 0x73, 0x20, 0x61, 0x6E, 0x79, 0x20, 0x6B, 0x65, 0x79, 0x20, 0x74, 0x6F,
0x20, 0x74, 0x72, 0x79, 0x20, 0x61, 0x67, 0x61, 0x69, 0x6E, 0x20, 0x2E, 0x2E, 0x2E, 0x20, 0x0D,
0x0A];
boot.boot_code[..boot_code.len()].copy_from_slice(&boot_code);
boot.boot_sig = [0x55, 0xAA];
// fix offsets in bootjmp and boot code for non-FAT32 filesystems (bootcode is on a different offset)
if fat_type != FatType::Fat32 {
// offset of boot code
let boot_code_offset = 0x36 + 8;
boot.bootjmp[1] = (boot_code_offset - 2) as u8;
// offset of message
const MESSAGE_OFFSET: u32 = 29;
let message_offset_in_sector = boot_code_offset + MESSAGE_OFFSET + 0x7c00;
boot.boot_code[3] = (message_offset_in_sector & 0xff) as u8;
boot.boot_code[4] = (message_offset_in_sector >> 8) as u8;
}
Ok((boot, fat_type))
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_determine_fat_type() {
assert_eq!(determine_fat_type(3 * MB), FatType::Fat12);
assert_eq!(determine_fat_type(4 * MB), FatType::Fat16);
assert_eq!(determine_fat_type(511 * MB), FatType::Fat16);
assert_eq!(determine_fat_type(512 * MB), FatType::Fat32);
}
#[test]
fn test_determine_bytes_per_cluster_fat12() {
assert_eq!(determine_bytes_per_cluster(1 * MB + 0, FatType::Fat12, 512), 512);
assert_eq!(determine_bytes_per_cluster(1 * MB + 1, FatType::Fat12, 512), 1024);
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat12, 4096), 4096);
}
#[test]
fn test_determine_bytes_per_cluster_fat16() {
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat16, 512), 1 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat16, 4 * KB as u16), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * MB + 0, FatType::Fat16, 512), 1 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * MB + 1, FatType::Fat16, 512), 2 * KB as u32);
assert_eq!(determine_bytes_per_cluster(128 * MB + 0, FatType::Fat16, 512), 2 * KB as u32);
assert_eq!(determine_bytes_per_cluster(128 * MB + 1, FatType::Fat16, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(256 * MB + 0, FatType::Fat16, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(256 * MB + 1, FatType::Fat16, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(512 * MB + 0, FatType::Fat16, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(512 * MB + 1, FatType::Fat16, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1024 * MB + 0, FatType::Fat16, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1024 * MB + 1, FatType::Fat16, 512), 32 * KB as u32);
assert_eq!(determine_bytes_per_cluster(99999 * MB, FatType::Fat16, 512), 32 * KB as u32);
}
#[test]
fn test_determine_bytes_per_cluster_fat32() {
assert_eq!(determine_bytes_per_cluster(260 * MB as u64, FatType::Fat32, 512), 512);
assert_eq!(determine_bytes_per_cluster(260 * MB as u64, FatType::Fat32, 4 * KB as u16), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(260 * MB as u64 + 1, FatType::Fat32, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(8 * GB as u64, FatType::Fat32, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(8 * GB as u64 + 1, FatType::Fat32, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * GB as u64 + 0, FatType::Fat32, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * GB as u64 + 1, FatType::Fat32, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(32 * GB as u64, FatType::Fat32, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(32 * GB as u64 + 1, FatType::Fat32, 512), 32 * KB as u32);
assert_eq!(determine_bytes_per_cluster(999 * GB as u64, FatType::Fat32, 512), 32 * KB as u32);
}
#[test]
fn test_determine_sectors_per_fat() {
assert_eq!(determine_sectors_per_fat(1 * MB as u32 / 512, 1, 2, 32, 1, FatType::Fat12), 6);
}
}

668
src/fs.rs
View File

@ -12,8 +12,8 @@ use io::{Error, ErrorKind, SeekFrom};
use byteorder::LittleEndian;
use byteorder_ext::{ReadBytesExt, WriteBytesExt};
use boot_sector::{BootRecord, BiosParameterBlock, format_boot_sector};
use dir::{Dir, DirRawStream};
use dir_entry::DIR_ENTRY_SIZE;
use file::File;
use table::{alloc_cluster, count_free_clusters, read_fat_flags, format_fat, ClusterIterator, RESERVED_FAT_ENTRIES};
use time::{TimeProvider, DEFAULT_TIME_PROVIDER};
@ -36,7 +36,7 @@ pub enum FatType {
}
impl FatType {
fn from_clusters(total_clusters: u32) -> FatType {
pub(crate) fn from_clusters(total_clusters: u32) -> FatType {
if total_clusters < 4085 {
FatType::Fat12
} else if total_clusters < 65525 {
@ -86,7 +86,7 @@ impl FsStatusFlags {
res
}
fn decode(flags: u8) -> Self {
pub(crate) fn decode(flags: u8) -> Self {
FsStatusFlags {
dirty: flags & 1 != 0,
io_error: flags & 2 != 0,
@ -102,370 +102,6 @@ impl<T: Read + Seek> ReadSeek for T {}
pub trait ReadWriteSeek: Read + Write + Seek {}
impl<T: Read + Write + Seek> ReadWriteSeek for T {}
#[allow(dead_code)]
#[derive(Default, Debug, Clone)]
pub(crate) struct BiosParameterBlock {
bytes_per_sector: u16,
sectors_per_cluster: u8,
reserved_sectors: u16,
fats: u8,
root_entries: u16,
total_sectors_16: u16,
media: u8,
sectors_per_fat_16: u16,
sectors_per_track: u16,
heads: u16,
hidden_sectors: u32,
total_sectors_32: u32,
// Extended BIOS Parameter Block
sectors_per_fat_32: u32,
extended_flags: u16,
fs_version: u16,
root_dir_first_cluster: u32,
fs_info_sector: u16,
backup_boot_sector: u16,
reserved_0: [u8; 12],
drive_num: u8,
reserved_1: u8,
ext_sig: u8,
volume_id: u32,
volume_label: [u8; 11],
fs_type_label: [u8; 8],
}
impl BiosParameterBlock {
fn deserialize<T: Read>(rdr: &mut T) -> io::Result<BiosParameterBlock> {
let mut bpb: BiosParameterBlock = Default::default();
bpb.bytes_per_sector = rdr.read_u16::<LittleEndian>()?;
bpb.sectors_per_cluster = rdr.read_u8()?;
bpb.reserved_sectors = rdr.read_u16::<LittleEndian>()?;
bpb.fats = rdr.read_u8()?;
bpb.root_entries = rdr.read_u16::<LittleEndian>()?;
bpb.total_sectors_16 = rdr.read_u16::<LittleEndian>()?;
bpb.media = rdr.read_u8()?;
bpb.sectors_per_fat_16 = rdr.read_u16::<LittleEndian>()?;
bpb.sectors_per_track = rdr.read_u16::<LittleEndian>()?;
bpb.heads = rdr.read_u16::<LittleEndian>()?;
bpb.hidden_sectors = rdr.read_u32::<LittleEndian>()?;
bpb.total_sectors_32 = rdr.read_u32::<LittleEndian>()?;
if bpb.is_fat32() {
bpb.sectors_per_fat_32 = rdr.read_u32::<LittleEndian>()?;
bpb.extended_flags = rdr.read_u16::<LittleEndian>()?;
bpb.fs_version = rdr.read_u16::<LittleEndian>()?;
bpb.root_dir_first_cluster = rdr.read_u32::<LittleEndian>()?;
bpb.fs_info_sector = rdr.read_u16::<LittleEndian>()?;
bpb.backup_boot_sector = rdr.read_u16::<LittleEndian>()?;
rdr.read_exact(&mut bpb.reserved_0)?;
bpb.drive_num = rdr.read_u8()?;
bpb.reserved_1 = rdr.read_u8()?;
bpb.ext_sig = rdr.read_u8()?; // 0x29
bpb.volume_id = rdr.read_u32::<LittleEndian>()?;
rdr.read_exact(&mut bpb.volume_label)?;
rdr.read_exact(&mut bpb.fs_type_label)?;
} else {
bpb.drive_num = rdr.read_u8()?;
bpb.reserved_1 = rdr.read_u8()?;
bpb.ext_sig = rdr.read_u8()?; // 0x29
bpb.volume_id = rdr.read_u32::<LittleEndian>()?;
rdr.read_exact(&mut bpb.volume_label)?;
rdr.read_exact(&mut bpb.fs_type_label)?;
}
// when the extended boot signature is anything other than 0x29, the fields are invalid
if bpb.ext_sig != 0x29 {
// fields after ext_sig are not used - clean them
bpb.volume_id = 0;
bpb.volume_label = [0; 11];
bpb.fs_type_label = [0; 8];
}
Ok(bpb)
}
fn serialize<T: Write>(&self, mut wrt: T) -> io::Result<()> {
wrt.write_u16::<LittleEndian>(self.bytes_per_sector)?;
wrt.write_u8(self.sectors_per_cluster)?;
wrt.write_u16::<LittleEndian>(self.reserved_sectors)?;
wrt.write_u8(self.fats)?;
wrt.write_u16::<LittleEndian>(self.root_entries)?;
wrt.write_u16::<LittleEndian>(self.total_sectors_16)?;
wrt.write_u8(self.media)?;
wrt.write_u16::<LittleEndian>(self.sectors_per_fat_16)?;
wrt.write_u16::<LittleEndian>(self.sectors_per_track)?;
wrt.write_u16::<LittleEndian>(self.heads)?;
wrt.write_u32::<LittleEndian>(self.hidden_sectors)?;
wrt.write_u32::<LittleEndian>(self.total_sectors_32)?;
if self.is_fat32() {
wrt.write_u32::<LittleEndian>(self.sectors_per_fat_32)?;
wrt.write_u16::<LittleEndian>(self.extended_flags)?;
wrt.write_u16::<LittleEndian>(self.fs_version)?;
wrt.write_u32::<LittleEndian>(self.root_dir_first_cluster)?;
wrt.write_u16::<LittleEndian>(self.fs_info_sector)?;
wrt.write_u16::<LittleEndian>(self.backup_boot_sector)?;
wrt.write_all(&self.reserved_0)?;
wrt.write_u8(self.drive_num)?;
wrt.write_u8(self.reserved_1)?;
wrt.write_u8(self.ext_sig)?; // 0x29
wrt.write_u32::<LittleEndian>(self.volume_id)?;
wrt.write_all(&self.volume_label)?;
wrt.write_all(&self.fs_type_label)?;
} else {
wrt.write_u8(self.drive_num)?;
wrt.write_u8(self.reserved_1)?;
wrt.write_u8(self.ext_sig)?; // 0x29
wrt.write_u32::<LittleEndian>(self.volume_id)?;
wrt.write_all(&self.volume_label)?;
wrt.write_all(&self.fs_type_label)?;
}
Ok(())
}
fn validate(&self) -> io::Result<()> {
// sanity checks
if self.bytes_per_sector.count_ones() != 1 {
return Err(Error::new(
ErrorKind::Other,
"invalid bytes_per_sector value in BPB (not power of two)",
));
} else if self.bytes_per_sector < 512 {
return Err(Error::new(ErrorKind::Other, "invalid bytes_per_sector value in BPB (value < 512)"));
} else if self.bytes_per_sector > 4096 {
return Err(Error::new(ErrorKind::Other, "invalid bytes_per_sector value in BPB (value > 4096)"));
}
if self.sectors_per_cluster.count_ones() != 1 {
return Err(Error::new(
ErrorKind::Other,
"invalid sectors_per_cluster value in BPB (not power of two)",
));
} else if self.sectors_per_cluster < 1 {
return Err(Error::new(ErrorKind::Other, "invalid sectors_per_cluster value in BPB (value < 1)"));
} else if self.sectors_per_cluster > 128 {
return Err(Error::new(
ErrorKind::Other,
"invalid sectors_per_cluster value in BPB (value > 128)",
));
}
// bytes per sector is u16, sectors per cluster is u8, so guaranteed no overflow in multiplication
let bytes_per_cluster = self.bytes_per_sector as u32 * self.sectors_per_cluster as u32;
let maximum_compatibility_bytes_per_cluster: u32 = 32 * 1024;
if bytes_per_cluster > maximum_compatibility_bytes_per_cluster {
// 32k is the largest value to maintain greatest compatibility
// Many implementations appear to support 64k per cluster, and some may support 128k or larger
// However, >32k is not as thoroughly tested...
warn!("fs compatibility: bytes_per_cluster value '{}' in BPB exceeds '{}', and thus may be incompatible with some implementations",
bytes_per_cluster, maximum_compatibility_bytes_per_cluster);
}
let is_fat32 = self.is_fat32();
if self.reserved_sectors < 1 {
return Err(Error::new(ErrorKind::Other, "invalid reserved_sectors value in BPB"));
} else if !is_fat32 && self.reserved_sectors != 1 {
// Microsoft document indicates fat12 and fat16 code exists that presume this value is 1
warn!(
"fs compatibility: reserved_sectors value '{}' in BPB is not '1', and thus is incompatible with some implementations",
self.reserved_sectors
);
}
if self.fats == 0 {
return Err(Error::new(ErrorKind::Other, "invalid fats value in BPB"));
} else if self.fats > 2 {
// Microsoft document indicates that few implementations support any values other than 1 or 2
warn!(
"fs compatibility: numbers of FATs '{}' in BPB is greater than '2', and thus is incompatible with some implementations",
self.fats
);
}
if is_fat32 && self.root_entries != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid root_entries value in BPB (should be zero for FAT32)",
));
}
if is_fat32 && self.total_sectors_16 != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid total_sectors_16 value in BPB (should be zero for FAT32)",
));
}
if (self.total_sectors_16 == 0) == (self.total_sectors_32 == 0) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors_16 or total_sectors_32 should be non-zero)",
));
}
if is_fat32 && self.sectors_per_fat_32 == 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid sectors_per_fat_32 value in BPB (should be non-zero for FAT32)",
));
}
if self.fs_version != 0 {
return Err(Error::new(ErrorKind::Other, "Unknown FS version"));
}
if self.total_sectors() <= self.first_data_sector() {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors field value is too small)",
));
}
let total_clusters = self.total_clusters();
let fat_type = FatType::from_clusters(total_clusters);
if is_fat32 != (fat_type == FatType::Fat32) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (result of FAT32 determination from total number of clusters and sectors_per_fat_16 field differs)",
));
}
let bits_per_fat_entry = fat_type.bits_per_fat_entry();
let total_fat_entries = self.sectors_per_fat() * self.bytes_per_sector as u32 * 8 / bits_per_fat_entry as u32;
if total_fat_entries - RESERVED_FAT_ENTRIES < total_clusters {
warn!("FAT is too small to compared to total number of clusters");
}
Ok(())
}
fn mirroring_enabled(&self) -> bool {
self.extended_flags & 0x80 == 0
}
fn active_fat(&self) -> u16 {
// The zero-based number of the active FAT is only valid if mirroring is disabled.
if self.mirroring_enabled() {
0
} else {
self.extended_flags & 0x0F
}
}
fn status_flags(&self) -> FsStatusFlags {
FsStatusFlags::decode(self.reserved_1)
}
fn is_fat32(&self) -> bool {
// because this field must be zero on FAT32, and
// because it must be non-zero on FAT12/FAT16,
// this provides a simple way to detect FAT32
self.sectors_per_fat_16 == 0
}
fn sectors_per_fat(&self) -> u32 {
if self.is_fat32() {
self.sectors_per_fat_32
} else {
self.sectors_per_fat_16 as u32
}
}
fn total_sectors(&self) -> u32 {
if self.total_sectors_16 == 0 {
self.total_sectors_32
} else {
self.total_sectors_16 as u32
}
}
fn root_dir_sectors(&self) -> u32 {
let root_dir_bytes = self.root_entries as u32 * DIR_ENTRY_SIZE as u32;
(root_dir_bytes + self.bytes_per_sector as u32 - 1) / self.bytes_per_sector as u32
}
fn sectors_per_all_fats(&self) -> u32 {
self.fats as u32 * self.sectors_per_fat()
}
fn first_data_sector(&self) -> u32 {
let root_dir_sectors = self.root_dir_sectors();
let fat_sectors = self.sectors_per_all_fats();
self.reserved_sectors as u32 + fat_sectors + root_dir_sectors
}
fn total_clusters(&self) -> u32 {
let total_sectors = self.total_sectors();
let first_data_sector = self.first_data_sector();
let data_sectors = total_sectors - first_data_sector;
data_sectors / self.sectors_per_cluster as u32
}
}
#[allow(dead_code)]
struct BootRecord {
bootjmp: [u8; 3],
oem_name: [u8; 8],
bpb: BiosParameterBlock,
boot_code: [u8; 448],
boot_sig: [u8; 2],
}
impl BootRecord {
fn deserialize<T: Read>(rdr: &mut T) -> io::Result<BootRecord> {
let mut boot: BootRecord = Default::default();
rdr.read_exact(&mut boot.bootjmp)?;
rdr.read_exact(&mut boot.oem_name)?;
boot.bpb = BiosParameterBlock::deserialize(rdr)?;
if boot.bpb.is_fat32() {
rdr.read_exact(&mut boot.boot_code[0..420])?;
} else {
rdr.read_exact(&mut boot.boot_code[0..448])?;
}
rdr.read_exact(&mut boot.boot_sig)?;
Ok(boot)
}
fn serialize<T: Write>(&self, mut wrt: T) -> io::Result<()> {
wrt.write_all(&self.bootjmp)?;
wrt.write_all(&self.oem_name)?;
self.bpb.serialize(&mut wrt)?;
if self.bpb.is_fat32() {
wrt.write_all(&self.boot_code[0..420])?;
} else {
wrt.write_all(&self.boot_code[0..448])?;
}
wrt.write_all(&self.boot_sig)?;
Ok(())
}
fn validate(&self) -> io::Result<()> {
if self.boot_sig != [0x55, 0xAA] {
return Err(Error::new(ErrorKind::Other, "Invalid boot sector signature"));
}
if self.bootjmp[0] != 0xEB && self.bootjmp[0] != 0xE9 {
warn!("Unknown opcode {:x} in bootjmp boot sector field", self.bootjmp[0]);
}
self.bpb.validate()?;
Ok(())
}
}
impl Default for BootRecord {
fn default() -> BootRecord {
BootRecord {
bootjmp: Default::default(),
oem_name: Default::default(),
bpb: Default::default(),
boot_code: [0; 448],
boot_sig: Default::default(),
}
}
}
#[derive(Clone, Default, Debug)]
struct FsInfoSector {
free_cluster_count: Option<u32>,
@ -1114,23 +750,42 @@ impl OemCpConverter for LossyOemCpConverter {
pub(crate) static LOSSY_OEM_CP_CONVERTER: LossyOemCpConverter = LossyOemCpConverter { _dummy: () };
fn write_zeros<T: ReadWriteSeek>(mut disk: T, mut len: usize) -> io::Result<()> {
const ZEROS: [u8; 512] = [0u8; 512];
while len > 0 {
let write_size = cmp::min(len, ZEROS.len());
disk.write_all(&ZEROS[..write_size])?;
len -= write_size;
}
Ok(())
}
fn write_zeros_until_end_of_sector<T: ReadWriteSeek>(mut disk: T, bytes_per_sector: u16) -> io::Result<()> {
let pos = disk.seek(SeekFrom::Current(0))?;
let total_bytes_to_write = bytes_per_sector as usize - (pos % bytes_per_sector as u64) as usize;
if total_bytes_to_write != bytes_per_sector as usize {
write_zeros(disk, total_bytes_to_write)?;
}
Ok(())
}
/// A FAT filesystem formatting options
///
/// This struct implements a builder pattern.
/// Options are specified as an argument for `format_volume` function.
#[derive(Default, Debug, Clone)]
pub struct FormatVolumeOptions {
bytes_per_sector: u16,
total_sectors: u32,
bytes_per_cluster: Option<u32>,
fat_type: Option<FatType>,
root_entries: Option<u16>,
media: Option<u8>,
sectors_per_track: Option<u16>,
heads: Option<u16>,
drive_num: Option<u8>,
volume_id: Option<u32>,
volume_label: Option<[u8; 11]>,
pub(crate) bytes_per_sector: u16,
pub(crate) total_sectors: u32,
pub(crate) bytes_per_cluster: Option<u32>,
pub(crate) fat_type: Option<FatType>,
pub(crate) root_entries: Option<u16>,
pub(crate) media: Option<u8>,
pub(crate) sectors_per_track: Option<u16>,
pub(crate) heads: Option<u16>,
pub(crate) drive_num: Option<u8>,
pub(crate) volume_id: Option<u32>,
pub(crate) volume_label: Option<[u8; 11]>,
}
impl FormatVolumeOptions {
@ -1216,207 +871,6 @@ impl FormatVolumeOptions {
}
}
const KB: u64 = 1024;
const MB: u64 = KB * 1024;
const GB: u64 = MB * 1024;
fn determine_fat_type(total_bytes: u64) -> FatType {
if total_bytes < 4 * MB {
FatType::Fat12
} else if total_bytes < 512 * MB {
FatType::Fat16
} else {
FatType::Fat32
}
}
fn determine_bytes_per_cluster(total_bytes: u64, fat_type: FatType, bytes_per_sector: u16) -> u32 {
let bytes_per_cluster = match fat_type {
FatType::Fat12 => (total_bytes.next_power_of_two() / MB * 512) as u32,
FatType::Fat16 => {
if total_bytes <= 16 * MB {
1 * KB as u32
} else if total_bytes <= 128 * MB {
2 * KB as u32
} else {
(total_bytes.next_power_of_two() / (64 * MB) * KB) as u32
}
},
FatType::Fat32 => {
if total_bytes <= 260 * MB {
512
} else if total_bytes <= 8 * GB {
4 * KB as u32
} else {
(total_bytes.next_power_of_two() / (2 * GB) * KB) as u32
}
},
};
const MAX_CLUSTER_SIZE: u32 = 32 * KB as u32;
debug_assert!(bytes_per_cluster.is_power_of_two());
cmp::min(cmp::max(bytes_per_cluster, bytes_per_sector as u32), MAX_CLUSTER_SIZE)
}
fn determine_sectors_per_fat(total_sectors: u32, reserved_sectors: u16, fats: u8, root_dir_sectors: u32,
sectors_per_cluster: u8, fat_type: FatType) -> u32 {
// TODO: check if this calculation is always correct (especially for FAT12)
let tmp_val1 = total_sectors - (reserved_sectors as u32 + root_dir_sectors as u32);
let mut tmp_val2 = (256 * sectors_per_cluster as u32) + fats as u32;
if fat_type == FatType::Fat32 {
tmp_val2 = tmp_val2 / 2;
} else if fat_type == FatType::Fat12 {
tmp_val2 = tmp_val2 / 3 * 4
}
(tmp_val1 + (tmp_val2 - 1)) / tmp_val2
}
fn format_bpb(options: &FormatVolumeOptions) -> io::Result<(BiosParameterBlock, FatType)> {
// TODO: maybe total_sectors could be optional?
let bytes_per_sector = options.bytes_per_sector;
let total_sectors = options.total_sectors;
let total_bytes = total_sectors as u64 * bytes_per_sector as u64;
let fat_type = options.fat_type.unwrap_or_else(|| determine_fat_type(total_bytes));
let bytes_per_cluster = options.bytes_per_cluster
.unwrap_or_else(|| determine_bytes_per_cluster(total_bytes, fat_type, bytes_per_sector));
let sectors_per_cluster = (bytes_per_cluster / bytes_per_sector as u32) as u8;
// Note: most of implementations use 32 reserved sectors for FAT32 but it's wasting of space
// We use 4 because there are two boot sectors and one FS Info sector (1 sector remains unused)
let reserved_sectors: u16 = if fat_type == FatType::Fat32 { 4 } else { 1 };
let fats = 2u8;
let is_fat32 = fat_type == FatType::Fat32;
let root_entries = if is_fat32 { 0 } else { options.root_entries.unwrap_or(512) };
let root_dir_bytes = root_entries as u32 * DIR_ENTRY_SIZE as u32;
let root_dir_sectors = (root_dir_bytes + bytes_per_sector as u32 - 1) / bytes_per_sector as u32;
// Check if volume has enough space to accomodate reserved sectors, FAT, root directory and some data space
// Having less than 8 sectors for FAT and data would make a little sense
if total_sectors <= reserved_sectors as u32 + root_dir_sectors as u32 + 8 {
return Err(Error::new(ErrorKind::Other, "Volume is too small",));
}
// calculate File Allocation Table size
let sectors_per_fat = determine_sectors_per_fat(total_sectors, reserved_sectors, fats, root_dir_sectors,
sectors_per_cluster, fat_type);
// drive_num should be 0 for floppy disks and 0x80 for hard disks - determine it using FAT type
let drive_num = options.drive_num.unwrap_or_else(|| if fat_type == FatType::Fat12 { 0 } else { 0x80 });
// reserved_0 is always zero
let reserved_0 = [0u8; 12];
// setup volume label
let mut volume_label = [0u8; 11];
if let Some(volume_label_from_opts) = options.volume_label {
volume_label.copy_from_slice(&volume_label_from_opts);
} else {
volume_label.copy_from_slice("NO NAME ".as_bytes());
}
// setup fs_type_label field
let mut fs_type_label = [0u8; 8];
let fs_type_label_str = match fat_type {
FatType::Fat12 => "FAT12 ",
FatType::Fat16 => "FAT16 ",
FatType::Fat32 => "FAT32 ",
};
fs_type_label.copy_from_slice(fs_type_label_str.as_bytes());
// create Bios Parameter Block struct
let bpb = BiosParameterBlock {
bytes_per_sector,
sectors_per_cluster,
reserved_sectors,
fats,
root_entries,
total_sectors_16: if total_sectors < 0x10000 { total_sectors as u16 } else { 0 },
media: options.media.unwrap_or(0xF8),
sectors_per_fat_16: if is_fat32 { 0 } else { sectors_per_fat as u16 },
sectors_per_track: options.sectors_per_track.unwrap_or(0x20),
heads: options.heads.unwrap_or(0x40),
hidden_sectors: 0,
total_sectors_32: if total_sectors >= 0x10000 { total_sectors } else { 0 },
// FAT32 fields start
sectors_per_fat_32: if is_fat32 { sectors_per_fat } else { 0 },
extended_flags: 0, // mirroring enabled
fs_version: 0,
root_dir_first_cluster: if is_fat32 { 2 } else { 0 },
fs_info_sector: if is_fat32 { 1 } else { 0 },
backup_boot_sector: if is_fat32 { 6 } else { 0 },
reserved_0,
// FAT32 fields end
drive_num,
reserved_1: 0,
ext_sig: 0x29,
volume_id: options.volume_id.unwrap_or(0x12345678),
volume_label,
fs_type_label,
};
// Check if number of clusters is proper for used FAT type
if FatType::from_clusters(bpb.total_clusters()) != fat_type {
return Err(Error::new(ErrorKind::Other, "Total number of clusters and FAT type does not match. Try other volume size"));
}
Ok((bpb, fat_type))
}
fn write_zeros<T: ReadWriteSeek>(mut disk: T, mut len: usize) -> io::Result<()> {
const ZEROS: [u8; 512] = [0u8; 512];
while len > 0 {
let write_size = cmp::min(len, ZEROS.len());
disk.write_all(&ZEROS[..write_size])?;
len -= write_size;
}
Ok(())
}
fn write_zeros_until_end_of_sector<T: ReadWriteSeek>(mut disk: T, bytes_per_sector: u16) -> io::Result<()> {
let pos = disk.seek(SeekFrom::Current(0))?;
let total_bytes_to_write = bytes_per_sector as usize - (pos % bytes_per_sector as u64) as usize;
if total_bytes_to_write != bytes_per_sector as usize {
write_zeros(disk, total_bytes_to_write)?;
}
Ok(())
}
fn format_boot_sector(options: &FormatVolumeOptions) -> io::Result<(BootRecord, FatType)> {
let mut boot: BootRecord = Default::default();
let (bpb, fat_type) = format_bpb(options)?;
boot.bpb = bpb;
boot.oem_name.copy_from_slice("MSWIN4.1".as_bytes());
// Boot code copied from FAT32 boot sector initialized by mkfs.fat
boot.bootjmp = [0xEB, 0x58, 0x90];
let boot_code: [u8; 129] = [
0x0E, 0x1F, 0xBE, 0x77, 0x7C, 0xAC, 0x22, 0xC0, 0x74, 0x0B, 0x56, 0xB4, 0x0E, 0xBB, 0x07, 0x00,
0xCD, 0x10, 0x5E, 0xEB, 0xF0, 0x32, 0xE4, 0xCD, 0x16, 0xCD, 0x19, 0xEB, 0xFE, 0x54, 0x68, 0x69,
0x73, 0x20, 0x69, 0x73, 0x20, 0x6E, 0x6F, 0x74, 0x20, 0x61, 0x20, 0x62, 0x6F, 0x6F, 0x74, 0x61,
0x62, 0x6C, 0x65, 0x20, 0x64, 0x69, 0x73, 0x6B, 0x2E, 0x20, 0x20, 0x50, 0x6C, 0x65, 0x61, 0x73,
0x65, 0x20, 0x69, 0x6E, 0x73, 0x65, 0x72, 0x74, 0x20, 0x61, 0x20, 0x62, 0x6F, 0x6F, 0x74, 0x61,
0x62, 0x6C, 0x65, 0x20, 0x66, 0x6C, 0x6F, 0x70, 0x70, 0x79, 0x20, 0x61, 0x6E, 0x64, 0x0D, 0x0A,
0x70, 0x72, 0x65, 0x73, 0x73, 0x20, 0x61, 0x6E, 0x79, 0x20, 0x6B, 0x65, 0x79, 0x20, 0x74, 0x6F,
0x20, 0x74, 0x72, 0x79, 0x20, 0x61, 0x67, 0x61, 0x69, 0x6E, 0x20, 0x2E, 0x2E, 0x2E, 0x20, 0x0D,
0x0A];
boot.boot_code[..boot_code.len()].copy_from_slice(&boot_code);
boot.boot_sig = [0x55, 0xAA];
// fix offsets in bootjmp and boot code for non-FAT32 filesystems (bootcode is on a different offset)
if fat_type != FatType::Fat32 {
// offset of boot code
let boot_code_offset = 0x36 + 8;
boot.bootjmp[1] = (boot_code_offset - 2) as u8;
// offset of message
const MESSAGE_OFFSET: u32 = 29;
let message_offset_in_sector = boot_code_offset + MESSAGE_OFFSET + 0x7c00;
boot.boot_code[3] = (message_offset_in_sector & 0xff) as u8;
boot.boot_code[4] = (message_offset_in_sector >> 8) as u8;
}
Ok((boot, fat_type))
}
/// Create FAT filesystem on a disk or partition (format a volume)
///
/// Supplied `disk` parameter cannot be seeked. If there is a need to format a fragment of a disk
@ -1486,59 +940,3 @@ pub fn format_volume<T: ReadWriteSeek>(mut disk: T, options: FormatVolumeOptions
disk.seek(SeekFrom::Start(0))?;
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_determine_fat_type() {
assert_eq!(determine_fat_type(3 * MB), FatType::Fat12);
assert_eq!(determine_fat_type(4 * MB), FatType::Fat16);
assert_eq!(determine_fat_type(511 * MB), FatType::Fat16);
assert_eq!(determine_fat_type(512 * MB), FatType::Fat32);
}
#[test]
fn test_determine_bytes_per_cluster_fat12() {
assert_eq!(determine_bytes_per_cluster(1 * MB + 0, FatType::Fat12, 512), 512);
assert_eq!(determine_bytes_per_cluster(1 * MB + 1, FatType::Fat12, 512), 1024);
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat12, 4096), 4096);
}
#[test]
fn test_determine_bytes_per_cluster_fat16() {
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat16, 512), 1 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat16, 4 * KB as u16), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * MB + 0, FatType::Fat16, 512), 1 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * MB + 1, FatType::Fat16, 512), 2 * KB as u32);
assert_eq!(determine_bytes_per_cluster(128 * MB + 0, FatType::Fat16, 512), 2 * KB as u32);
assert_eq!(determine_bytes_per_cluster(128 * MB + 1, FatType::Fat16, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(256 * MB + 0, FatType::Fat16, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(256 * MB + 1, FatType::Fat16, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(512 * MB + 0, FatType::Fat16, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(512 * MB + 1, FatType::Fat16, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1024 * MB + 0, FatType::Fat16, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1024 * MB + 1, FatType::Fat16, 512), 32 * KB as u32);
assert_eq!(determine_bytes_per_cluster(99999 * MB, FatType::Fat16, 512), 32 * KB as u32);
}
#[test]
fn test_determine_bytes_per_cluster_fat32() {
assert_eq!(determine_bytes_per_cluster(260 * MB as u64, FatType::Fat32, 512), 512);
assert_eq!(determine_bytes_per_cluster(260 * MB as u64, FatType::Fat32, 4 * KB as u16), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(260 * MB as u64 + 1, FatType::Fat32, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(8 * GB as u64, FatType::Fat32, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(8 * GB as u64 + 1, FatType::Fat32, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * GB as u64 + 0, FatType::Fat32, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * GB as u64 + 1, FatType::Fat32, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(32 * GB as u64, FatType::Fat32, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(32 * GB as u64 + 1, FatType::Fat32, 512), 32 * KB as u32);
assert_eq!(determine_bytes_per_cluster(999 * GB as u64, FatType::Fat32, 512), 32 * KB as u32);
}
#[test]
fn test_determine_sectors_per_fat() {
assert_eq!(determine_sectors_per_fat(1 * MB as u32 / 512, 1, 2, 32, 1, FatType::Fat12), 6);
}
}

1
src/lib.rs
View File

@ -76,6 +76,7 @@ extern crate core_io;
#[cfg(all(not(feature = "std"), feature = "alloc"))]
extern crate alloc;
mod boot_sector;
mod dir;
mod dir_entry;
mod file;