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Fixed some Task stuff, added DOSFS filesystem

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This commit is contained in:
Lucia Ceionia 2022-09-21 17:14:11 -05:00
parent 6ebee28032
commit 9216b3359a
15 changed files with 2280 additions and 56 deletions
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6
Makefile
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@ -1,11 +1,11 @@
objects = entry.o kernel.o task.o handler.o interrupt.o v86.o print.o tss.o
objects = entry.o kernel.o task.o handler.o interrupt.o v86.o print.o tss.o dosfs/dosfs.o
CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=pentium-m -fno-stack-protector -nostdlib -c
%.o: %.nasm
nasm -f elf32 -o $@ $<
%.o: %.c
clang $(CFLAGS) -O2 $<
clang $(CFLAGS) -O2 -o $@ $<
all: $(objects)
nasm boot.nasm -o boot.bin
@ -17,3 +17,5 @@ virtdisk:
dd bs=1M count=32 if=/dev/zero of=virtdisk.bin
echo -n -e '\x55\xaa' | dd bs=1 seek=510 conv=notrunc of=virtdisk.bin
clean:
rm $(objects)

2
boot.nasm
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@ -26,6 +26,6 @@ string: db 'DISK ERROR'
addr_packet:
db 0x10, 0x00 ; size, reserved
dw 0x20 ; blocks
dw 0x39 ; blocks
dd 0x8000 ; transfer buffer
dq 1 ; start block

1273
dosfs/dosfs.c Executable file
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File diff suppressed because it is too large Load Diff

374
dosfs/dosfs.h Executable file
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/*
DOSFS Embedded FAT-Compatible Filesystem
(C) 2005 Lewin A.R.W. Edwards (sysadm@zws.com)
*/
#ifndef _DOSFS_H
#define _DOSFS_H
#include <stdint.h>
//===================================================================
// User-supplied functions
uint32_t DFS_ReadSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t count);
uint32_t DFS_WriteSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t count);
//===================================================================
// Configurable items
#define MAX_PATH 64 // Maximum path length (increasing this will
// GREATLY increase stack requirements!)
#define DIR_SEPARATOR '/' // character separating directory components
// End of configurable items
//===================================================================
//===================================================================
// 32-bit error codes
#define DFS_OK 0 // no error
#define DFS_EOF 1 // end of file (not an error)
#define DFS_WRITEPROT 2 // volume is write protected
#define DFS_NOTFOUND 3 // path or file not found
#define DFS_PATHLEN 4 // path too long
#define DFS_ALLOCNEW 5 // must allocate new directory cluster
#define DFS_ERRMISC 0xffffffff // generic error
//===================================================================
// File access modes
#define DFS_READ 1 // read-only
#define DFS_WRITE 2 // write-only
//===================================================================
// Miscellaneous constants
#define SECTOR_SIZE 512 // sector size in bytes
//===================================================================
// Internal subformat identifiers
#define FAT12 0
#define FAT16 1
#define FAT32 2
//===================================================================
// DOS attribute bits
#define ATTR_READ_ONLY 0x01
#define ATTR_HIDDEN 0x02
#define ATTR_SYSTEM 0x04
#define ATTR_VOLUME_ID 0x08
#define ATTR_DIRECTORY 0x10
#define ATTR_ARCHIVE 0x20
#define ATTR_LONG_NAME (ATTR_READ_ONLY | ATTR_HIDDEN | ATTR_SYSTEM | ATTR_VOLUME_ID)
/*
Directory entry structure
note: if name[0] == 0xe5, this is a free dir entry
if name[0] == 0x00, this is a free entry and all subsequent entries are free
if name[0] == 0x05, the first character of the name is 0xe5 [a kanji nicety]
Date format: bit 0-4 = day of month (1-31)
bit 5-8 = month, 1=Jan..12=Dec
bit 9-15 = count of years since 1980 (0-127)
Time format: bit 0-4 = 2-second count, (0-29)
bit 5-10 = minutes (0-59)
bit 11-15= hours (0-23)
*/
typedef struct _tagDIRENT {
uint8_t name[11]; // filename
uint8_t attr; // attributes (see ATTR_* constant definitions)
uint8_t reserved; // reserved, must be 0
uint8_t crttimetenth; // create time, 10ths of a second (0-199 are valid)
uint8_t crttime_l; // creation time low byte
uint8_t crttime_h; // creation time high byte
uint8_t crtdate_l; // creation date low byte
uint8_t crtdate_h; // creation date high byte
uint8_t lstaccdate_l; // last access date low byte
uint8_t lstaccdate_h; // last access date high byte
uint8_t startclus_h_l; // high word of first cluster, low byte (FAT32)
uint8_t startclus_h_h; // high word of first cluster, high byte (FAT32)
uint8_t wrttime_l; // last write time low byte
uint8_t wrttime_h; // last write time high byte
uint8_t wrtdate_l; // last write date low byte
uint8_t wrtdate_h; // last write date high byte
uint8_t startclus_l_l; // low word of first cluster, low byte
uint8_t startclus_l_h; // low word of first cluster, high byte
uint8_t filesize_0; // file size, low byte
uint8_t filesize_1; //
uint8_t filesize_2; //
uint8_t filesize_3; // file size, high byte
} DIRENT, *PDIRENT;
/*
Partition table entry structure
*/
typedef struct _tagPTINFO {
uint8_t active; // 0x80 if partition active
uint8_t start_h; // starting head
uint8_t start_cs_l; // starting cylinder and sector (low byte)
uint8_t start_cs_h; // starting cylinder and sector (high byte)
uint8_t type; // type ID byte
uint8_t end_h; // ending head
uint8_t end_cs_l; // ending cylinder and sector (low byte)
uint8_t end_cs_h; // ending cylinder and sector (high byte)
uint8_t start_0; // starting sector# (low byte)
uint8_t start_1; //
uint8_t start_2; //
uint8_t start_3; // starting sector# (high byte)
uint8_t size_0; // size of partition (low byte)
uint8_t size_1; //
uint8_t size_2; //
uint8_t size_3; // size of partition (high byte)
} PTINFO, *PPTINFO;
/*
Master Boot Record structure
*/
typedef struct _tagMBR {
uint8_t bootcode[0x1be]; // boot sector
PTINFO ptable[4]; // four partition table structures
uint8_t sig_55; // 0x55 signature byte
uint8_t sig_aa; // 0xaa signature byte
} MBR, *PMBR;
/*
BIOS Parameter Block structure (FAT12/16)
*/
typedef struct _tagBPB {
uint8_t bytepersec_l; // bytes per sector low byte (0x00)
uint8_t bytepersec_h; // bytes per sector high byte (0x02)
uint8_t secperclus; // sectors per cluster (1,2,4,8,16,32,64,128 are valid)
uint8_t reserved_l; // reserved sectors low byte
uint8_t reserved_h; // reserved sectors high byte
uint8_t numfats; // number of FAT copies (2)
uint8_t rootentries_l; // number of root dir entries low byte (0x00 normally)
uint8_t rootentries_h; // number of root dir entries high byte (0x02 normally)
uint8_t sectors_s_l; // small num sectors low byte
uint8_t sectors_s_h; // small num sectors high byte
uint8_t mediatype; // media descriptor byte
uint8_t secperfat_l; // sectors per FAT low byte
uint8_t secperfat_h; // sectors per FAT high byte
uint8_t secpertrk_l; // sectors per track low byte
uint8_t secpertrk_h; // sectors per track high byte
uint8_t heads_l; // heads low byte
uint8_t heads_h; // heads high byte
uint8_t hidden_0; // hidden sectors low byte
uint8_t hidden_1; // (note - this is the number of MEDIA sectors before
uint8_t hidden_2; // first sector of VOLUME - we rely on the MBR instead)
uint8_t hidden_3; // hidden sectors high byte
uint8_t sectors_l_0; // large num sectors low byte
uint8_t sectors_l_1; //
uint8_t sectors_l_2; //
uint8_t sectors_l_3; // large num sectors high byte
} BPB, *PBPB;
/*
Extended BIOS Parameter Block structure (FAT12/16)
*/
typedef struct _tagEBPB {
uint8_t unit; // int 13h drive#
uint8_t head; // archaic, used by Windows NT-class OSes for flags
uint8_t signature; // 0x28 or 0x29
uint8_t serial_0; // serial#
uint8_t serial_1; // serial#
uint8_t serial_2; // serial#
uint8_t serial_3; // serial#
uint8_t label[11]; // volume label
uint8_t system[8]; // filesystem ID
} EBPB, *PEBPB;
/*
Extended BIOS Parameter Block structure (FAT32)
*/
typedef struct _tagEBPB32 {
uint8_t fatsize_0; // big FAT size in sectors low byte
uint8_t fatsize_1; //
uint8_t fatsize_2; //
uint8_t fatsize_3; // big FAT size in sectors high byte
uint8_t extflags_l; // extended flags low byte
uint8_t extflags_h; // extended flags high byte
uint8_t fsver_l; // filesystem version (0x00) low byte
uint8_t fsver_h; // filesystem version (0x00) high byte
uint8_t root_0; // cluster of root dir, low byte
uint8_t root_1; //
uint8_t root_2; //
uint8_t root_3; // cluster of root dir, high byte
uint8_t fsinfo_l; // sector pointer to FSINFO within reserved area, low byte (2)
uint8_t fsinfo_h; // sector pointer to FSINFO within reserved area, high byte (0)
uint8_t bkboot_l; // sector pointer to backup boot sector within reserved area, low byte (6)
uint8_t bkboot_h; // sector pointer to backup boot sector within reserved area, high byte (0)
uint8_t reserved[12]; // reserved, should be 0
uint8_t unit; // int 13h drive#
uint8_t head; // archaic, used by Windows NT-class OSes for flags
uint8_t signature; // 0x28 or 0x29
uint8_t serial_0; // serial#
uint8_t serial_1; // serial#
uint8_t serial_2; // serial#
uint8_t serial_3; // serial#
uint8_t label[11]; // volume label
uint8_t system[8]; // filesystem ID
} EBPB32, *PEBPB32;
/*
Logical Boot Record structure (volume boot sector)
*/
typedef struct _tagLBR {
uint8_t jump[3]; // JMP instruction
uint8_t oemid[8]; // OEM ID, space-padded
BPB bpb; // BIOS Parameter Block
union {
EBPB ebpb; // FAT12/16 Extended BIOS Parameter Block
EBPB32 ebpb32; // FAT32 Extended BIOS Parameter Block
} ebpb;
uint8_t code[420]; // boot sector code
uint8_t sig_55; // 0x55 signature byte
uint8_t sig_aa; // 0xaa signature byte
} LBR, *PLBR;
/*
Volume information structure (Internal to DOSFS)
*/
typedef struct _tagVOLINFO {
uint8_t unit; // unit on which this volume resides
uint8_t filesystem; // formatted filesystem
// These two fields aren't very useful, so support for them has been commented out to
// save memory. (Note that the "system" tag is not actually used by DOS to determine
// filesystem type - that decision is made entirely on the basis of how many clusters
// the drive contains. DOSFS works the same way).
// See tag: OEMID in dosfs.c
// uint8_t oemid[9]; // OEM ID ASCIIZ
// uint8_t system[9]; // system ID ASCIIZ
uint8_t label[12]; // volume label ASCIIZ
uint32_t startsector; // starting sector of filesystem
uint8_t secperclus; // sectors per cluster
uint16_t reservedsecs; // reserved sectors
uint32_t numsecs; // number of sectors in volume
uint32_t secperfat; // sectors per FAT
uint16_t rootentries; // number of root dir entries
uint32_t numclusters; // number of clusters on drive
// The fields below are PHYSICAL SECTOR NUMBERS.
uint32_t fat1; // starting sector# of FAT copy 1
uint32_t rootdir; // starting sector# of root directory (FAT12/FAT16) or cluster (FAT32)
uint32_t dataarea; // starting sector# of data area (cluster #2)
} VOLINFO, *PVOLINFO;
/*
Flags in DIRINFO.flags
*/
#define DFS_DI_BLANKENT 0x01 // Searching for blank entry
/*
Directory search structure (Internal to DOSFS)
*/
typedef struct _tagDIRINFO {
uint32_t currentcluster; // current cluster in dir
uint8_t currentsector; // current sector in cluster
uint8_t currententry; // current dir entry in sector
uint8_t *scratch; // ptr to user-supplied scratch buffer (one sector)
uint8_t flags; // internal DOSFS flags
} DIRINFO, *PDIRINFO;
/*
File handle structure (Internal to DOSFS)
*/
typedef struct _tagFILEINFO {
PVOLINFO volinfo; // VOLINFO used to open this file
uint32_t dirsector; // physical sector containing dir entry of this file
uint8_t diroffset; // # of this entry within the dir sector
uint8_t mode; // mode in which this file was opened
uint32_t firstcluster; // first cluster of file
uint32_t filelen; // byte length of file
uint32_t cluster; // current cluster
uint32_t pointer; // current (BYTE) pointer
} FILEINFO, *PFILEINFO;
/*
Get starting sector# of specified partition on drive #unit
NOTE: This code ASSUMES an MBR on the disk.
scratchsector should point to a SECTOR_SIZE scratch area
Returns 0xffffffff for any error.
If pactive is non-NULL, this function also returns the partition active flag.
If pptype is non-NULL, this function also returns the partition type.
If psize is non-NULL, this function also returns the partition size.
*/
uint32_t DFS_GetPtnStart(uint8_t unit, uint8_t *scratchsector, uint8_t pnum, uint8_t *pactive, uint8_t *pptype, uint32_t *psize);
/*
Retrieve volume info from BPB and store it in a VOLINFO structure
You must provide the unit and starting sector of the filesystem, and
a pointer to a sector buffer for scratch
Attempts to read BPB and glean information about the FS from that.
Returns 0 OK, nonzero for any error.
*/
uint32_t DFS_GetVolInfo(uint8_t unit, uint8_t *scratchsector, uint32_t startsector, PVOLINFO volinfo);
/*
Open a directory for enumeration by DFS_GetNextDirEnt
You must supply a populated VOLINFO (see DFS_GetVolInfo)
The empty string or a string containing only the directory separator are
considered to be the root directory.
Returns 0 OK, nonzero for any error.
*/
uint32_t DFS_OpenDir(PVOLINFO volinfo, uint8_t *dirname, PDIRINFO dirinfo);
/*
Get next entry in opened directory structure. Copies fields into the dirent
structure, updates dirinfo. Note that it is the _caller's_ responsibility to
handle the '.' and '..' entries.
A deleted file will be returned as a NULL entry (first char of filename=0)
by this code. Filenames beginning with 0x05 will be translated to 0xE5
automatically. Long file name entries will be returned as NULL.
returns DFS_EOF if there are no more entries, DFS_OK if this entry is valid,
or DFS_ERRMISC for a media error
*/
uint32_t DFS_GetNext(PVOLINFO volinfo, PDIRINFO dirinfo, PDIRENT dirent);
/*
Open a file for reading or writing. You supply populated VOLINFO, a path to the file,
mode (DFS_READ or DFS_WRITE) and an empty fileinfo structure. You also need to
provide a pointer to a sector-sized scratch buffer.
Returns various DFS_* error states. If the result is DFS_OK, fileinfo can be used
to access the file from this point on.
*/
uint32_t DFS_OpenFile(PVOLINFO volinfo, uint8_t *path, uint8_t mode, uint8_t *scratch, PFILEINFO fileinfo);
/*
Read an open file
You must supply a prepopulated FILEINFO as provided by DFS_OpenFile, and a
pointer to a SECTOR_SIZE scratch buffer.
Note that returning DFS_EOF is not an error condition. This function updates the
successcount field with the number of bytes actually read.
*/
uint32_t DFS_ReadFile(PFILEINFO fileinfo, uint8_t *scratch, uint8_t *buffer, uint32_t *successcount, uint32_t len);
/*
Write an open file
You must supply a prepopulated FILEINFO as provided by DFS_OpenFile, and a
pointer to a SECTOR_SIZE scratch buffer.
This function updates the successcount field with the number of bytes actually written.
*/
uint32_t DFS_WriteFile(PFILEINFO fileinfo, uint8_t *scratch, uint8_t *buffer, uint32_t *successcount, uint32_t len);
/*
Seek file pointer to a given position
This function does not return status - refer to the fileinfo->pointer value
to see where the pointer wound up.
Requires a SECTOR_SIZE scratch buffer
*/
void DFS_Seek(PFILEINFO fileinfo, uint32_t offset, uint8_t *scratch);
/*
Delete a file
scratch must point to a sector-sized buffer
*/
uint32_t DFS_UnlinkFile(PVOLINFO volinfo, uint8_t *path, uint8_t *scratch);
// If we are building a host-emulation version, include host support
#ifdef HOSTVER
#include "hostemu.h"
#endif
#endif // _DOSFS_H

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README.TXT (C) Copyright 2006
DOSFS Level 1 Version 1.02 Lewin A.R.W. Edwards (sysadm@zws.com)
=====================================================================
Abstract
========
DOSFS is a FAT-compatible filesystem intended for fairly low-end
embedded applications. It is not the leanest possible implementation
(the leanest FAT implementations operate in << 512 bytes of RAM, with
heavy restrictions). This code strikes a good balance between size
and functionality, with an emphasis on RAM footprint.
Intended target systems would be in the ballpark of 1K RAM, 4K ROM
or more.
Features:
* Supports FAT12, FAT16 and FAT32 volumes
* Supports storage devices up to 2048Gbytes in size (LBA32)
* Supports devices with or without MBRs (hard disks vs. floppy disks
or ZIP drives formatted as "big floppies")
* Supports multiple partitions on disks with MBRs
* Supports subdirectories
* Can be operated with a single global 512-byte sector buffer
* Fully reentrant code (assuming the underlying physical device driver
is reentrant and global sector buffers are not used). There are no
global variables in the filesystem
* Does not perform any memory allocation
* Partial support for random-access files
Applications:
* Firmware upgrades
* Failsafe IPL
* Media playback
* Data logging
* Configuration storage
There is no technical support for this free product; however, if you
have questions or suggestions, you are encouraged to email Lewin
Edwards at sysadm@zws.com. If you need custom additions to the code,
or if you have other projects for which you need engineering
assistance, please feel free to email or call (646) 549-3715.
License
=======
The license for DOSFS is very simple but verbose to state.
1. DOSFS is (C) Copyright 2006 by Lewin A.R.W. Edwards ("Author").
All rights not explicitly granted herein are reserved. The DOSFS
code is the permanent property of the Author and no transfer of
ownership is implied by this license.
2. DOSFS is an educational project, provided as-is. No guarantee of
performance or suitability for any application is stated or
implied. You use this product entirely at your own risk. Use of
this product in any manner automatically waives any right to seek
compensation or damages of any sort from the Author. Since the
products you might make are entirely out of the Author's control,
use of this product also constitutes an agreement by you to take
full responsibility for and indemnify the Author against any
action for any loss or damage (including economic loss of any
type, and specifically including patent litigation) that arises
from a product made by you that incorporates any portion of
the DOSFS code.
3. If you live under the jurisdiction of any legislation that would
prohibit or limit any condition in this license, you cannot be
licensed to use this product.
4. If you do not fall into the excluded category in point 3, you are
hereby licensed to use the DOSFS code in any application that you
see fit. You are not required to pay any fee or notify the Author
that you are using DOSFS. Any modifications made by you to the
DOSFS code are your property and you may distribute the modified
version in any manner that you wish. You are not required to
disclose sourcecode to such modifications, either to the Author or
to any third party. Any such disclosure made to the Author will
irrevocably become the property of the Author in the absence of a
formal agreement to the contrary, established prior to such
disclosure being made.
To summarize the intent of the above: DOSFS is free. You can do what
you want with it. Anything that happens as a result is entirely your
responsibility. You can't take ownership of my code and stop me from
doing whatever I want with it. If you do something nifty with DOSFS
and send me the sourcecode, I may include your changes in the next
distribution and it will be released to the world as free software.
If someone sues you because your DOSFS-containing product causes
any sort of legal, financial or other problem, it's your lawsuit,
not mine, and you'll exclude me from the proceedings.
User-Supplied Functions
=======================
You must provide functions to read sectors into memory and write
them back to the target media. The demo suite includes an emulation
module that reads/writes a disk image file (#define HOSTVER pulls
in hostemu.h which wraps the prototypes for these functions).
There are various tools for UNIX, DOS, Windows et al, to create
images from storage media; my preferred utility is dd.
The functions you must supply in your embedded app are:
DFS_ReadSector(unit,buffer,sector,count)
DFS_WriteSector(unit,buffer,sector,count)
These two functions read and write, respectively, "count" sectors of
size SECTOR_SIZE (512 bytes; see below) from/to physical sector
#"sector" of device "unit", to/from the scratch buffer "buffer". They
should return 0 for success or nonzero for failure. In the current
implementation of DOSFS, count will always be 1.
The "unit" argument is designed to permit implementation of multiple
storage devices, for example multiple media slots on a single device,
or to differentiate between master and slave devices on an ATAPI bus.
This code is designed for 512-byte sectors. Although the sector size
is a #define, you should not tinker with it because the vast majority
of FAT filesystems use 512-byte sectors, and the DOSFS code doesn't
support runtime determination of sector size. This will not affect the
vast majority of users.
Example Code
============
Refer to the tests in main.c to see how to call DOSFS functions.
(These tests are all commented out). Note that the only two files
you need to add to your project are dosfs.c and dosfs.h.
Mounting Volumes
================
--If the device has a partition table (practically all removable flash
media are formatted this way), call DFS_GetPtnStart to get the
starting sector# of the desired partition. You can optionally also
retrieve the active state, partition type byte and partition size
in this step. The reason this step is broken out separately is so
you can support devices that are formatted like a floppy disk, i.e.
the volume starts directly at physical sector 0 of the media.
--Call DFS_GetVolInfo to read filesystem info into a VOLINFO structure.
DFS_GetVolInfo needs to know the unit number and partition starting
sector (as returned by DFS_GetPtnStart, or 0 if this is a "floppy-
format" volume without an MBR).
From this point on, the VOLINFO structure is all you'll need - you can
forget the unit and partition start sector numbers.
Enumerating Directory Contents
==============================
--Call DFS_Opendir and supply a path, populated VOLINFO and a
DIRINFO structure to receive the results. Note - you must PREPOPULATE
the DIRINFO.scratch field with a pointer to a sector scratch buffer.
This buffer must remain unmolested while you have the directory open
for searching.
--Call DFS_GetNext to receive the DIRENT contents for the next directory
item. This function returns DFS_OK for no error, and DFS_EOF if there
are no more entries in the directory being searched.
Before using the DIRENT, check the first character of the name. If it
is NULL, then this is an unusable entry - call DFS_GetNext again to
keep searching. LFN directory entries are automatically tagged this way
so your application will not be pestered by them.
Note: A designed side-effect of this code is that when you locate the
file of interest, the DIRINFO.currentcluster, DIRINFO.currentsector
and DIRINFO.currententry-1 fields will identify the directory entry of
interest.
Reading a File
==============
--Call DFS_OpenFile with mode = DFS_READ and supply a path and the relevant
VOLINFO structure. DFS_OpenFile will populate a FILEINFO that can be used
to refer to the file.
--Optionally call DFS_Seek to set the file pointer. If you attempt to set
the file pointer past the end of file, the file will NOT be extended. Check
the FILEINFO.pointer value after DFS_Seek to verify that the pointer is
where you expect it to be.
--Observe that functionality similar to the "whence" parameter of fseek() can
be obtained by using simple arithmetic on the FILEINFO.pointer and
FILEINFO.filelen members.
--Call DFS_ReadFile with the FILEINFO you obtained from OpenFile, and a
pointer to a buffer plus the desired number of bytes to read, and a
pointer to a sector-sized scratch buffer. The reason a scratch sector is
required is because the underlying sector read function doesn't know
about partial reads.
--Note that a file opened for reading cannot be written. If you need r/w
access, open with mode = DFS_WRITE (see below).
Writing a file
==============
--Call DFS_OpenFile with mode = DFS_WRITE and supply a path and the relevant
VOLINFO structure. DFS_OpenFile will populate a FILEINFO that can be used to
refer to the file.
--Optionally call DFS_Seek to set the file pointer. Refer to the notes on
this topic in the section on reading files, above.
--Call DFS_WriteFile with the FILEINFO you obtained from OpenFile, and a
pointer to the source buffer, and a pointer to a sector-sized scratch
buffer.
--Note that a file open for writing can also be read.
--Files are created automatically if they do not exist. Subdirectories are
NOT automatically created.
--If you open an existing file for writing, the file pointer will start at
the beginning of the data; if you want to append, seek to the end before
writing new data.
--If you perform random-access writes to a file, the length will NOT change
unless you exceed the file's original length. There is currently no
function to truncate a file at the current pointer position.
--On-disk consistency is guaranteed when DFS_WriteFile exits, unless your
physical layer has a writeback cache in it.
Deleting a file
===============
--Call DFS_UnlinkFile
--WARNING: This call will delete a subdirectory (correctly) but will NOT
first recurse the directory to delete the contents - so you will end up
with lost clusters.
Notes
=====
Some platforms may require explicit pragmas or attributes to the structures
and unions. For example, arm-gcc will require __attribute__ ((__packed__))
otherwise it will try to be "smart" and place the uint8_t members on 4-byte
boundaries. There is no truly elegant compiler-independent method to get
around this sort of problem.
The code assumes either a von Neumann architecture, or a compiler that
is smart enough to understand where your pointers are aimed and emit
the right kind of memory read and write instructions. The implications
of this statement depend on your target processor and the compiler you
are using. Be very careful not to straddle bank boundaries on bank-
switched memory systems.
Physical 32-bit sector numbers are used throughout. Therefore, the
CHS geometry (if any) of the storage media is not known to DOSFS. Your
sector r/w functions may need to query the CHS geometry and perform
mapping.
File timestamps set by DOSFS are always 1:01:00am on Jan 1, 2006. If
your system has a concept of real time, you can enhance this.
FILEINFO structures contain a pointer to the corresponding VOLINFO
used to open the file, mainly in order to avoid mixups but also to
obviate the need for an extra parameter to every file read/write. DOSFS
assumes that the VOLINFO won't move around. If you need to move or
destroy VOLINFOs pertaining to open files, you'll have to fix up the
pointer in the FILEINFO structure yourself.
The subdirectory delimiter is a forward slash ( '/' ) by default. The
reason for this is to avoid the common programming error of forgetting
that backslash is an escape character in C strings; i.e. "\MYDIR\FILE"
is NOT what you want; "\\MYDIR\\FILE" is what you wanted to type. If you
are porting DOS code into an embedded environment, feel free to change
this #define.
DOSFS does not have a concept of "current directory". A current directory
is owned by a process, and a process is an operating system concept.
DOSFS is a filesystem library, not an operating system. Therefore, any
path you provide to a DOSFS call is assumed to be relative to the root of
the volume.
There is no call to close a file or directory that is open for reading or
writing. You can simply destroy or reuse the data structures allocated for
that operation; there is no internal state in DOSFS so no cleanup is
necessary. Similarly, there is no call to close a file that is open for
writing. (Observe that dosfs.c has no global variables. All state information
is stored in data structures provided by the caller).
MAX_PATH is defined as 64. MS-type DOS filesystems support 128 characters
or more in paths. You can increase this define, but it may GREATLY
increase memory requirements.
VFAT long filenames are not supported. There is a certain amount of
patent controversy about them, but more importantly they don't really
belong in the scope of a "minimalist embedded filesystem".
Improving Performance
=====================
Read performance is fairly good, but can be improved by implementing read
caching on the FAT (see below) and, depending on your hardware platform,
possibly by implementing multi-sector reads.
Write performance may benefit ENORMOUSLY from platform-specific
optimization, especially if you are working with a flash media type that
has a large erase block size. While it is not possible to offer detailed
platform-independent advice, my general advice is to implement writeback
caching on the FAT area. One method for doing this would be to have a
cache system that lives in the DFS_ReadSector/WriteSector functions (on
top of the physical sector r/w functions) and is initially switched off.
Once you have called DFS_GetVolInfo, you then extract the VOLINFO.fat1
and VOLINFO.rootdir parameters and pass them to your caching layer.
Sectors >= fat1 and < rootdir should be cached. The cache strategy is
determined by the physical storage medium underlying the filesystem.
CACHING HINT:
Observe that there will be numerous read-modify-write operations in the
region from VOLINFO.fat1 through VOLINFO.fat1+VOLINFO.secperfat-1, but
in the region from VOLINFO.fat1+VOLINFO.secperfat through VOLINFO.rootdir
there will ONLY be write operations.
Platform Compatibility
======================
DOSFS was derived from code originally written for ARM7TDMI but
designed to be portable. It has been tested on AVR (using avrgcc),
MSP430 (using Rowley's CrossWorks) and PPC603e (using gcc); the host
test suite has also been validated on x86 using gcc under both Cygwin
and 32-bit Fedora Core 4 Linux.
TODO list
=========
* Add function to create subdirectory
* Make DFS_UnlinkFile recognize non-empty subdirectories
* Support "fast write" files where the FAT is not updated, for
logging applications where latency is important.
Test cases for V1.02
====================
Version 1.02 has NOT been through full regression testing. However the
bugs fixed in this version are important, and people have been asking
about them.
Test cases for V1.01
====================
See below.
Test cases for V1.00
====================
These are the test cases that were used to validate the correct
functionality of the DOSFS suite. Each test was performed on FAT12,
FAT16 and FAT32 volumes. P=Pass, F=Fail.
Case F12 F16 F32
---------------------------------------------------------------------
Get volume information P P P
Open root directory P P P
List contents of root directory (fully populated) P P P
Open subdirectory P P P
List contents of subdirectory (<= 1 cluster) P P P
List contents of large subdirectory (> 1 cluster) P P P
Open 5-level nested subdirectory P P P
Open existing file for reading P P P
Open nonexistent file for reading P P P
Seek past EOF, file open for reading P P P
Seek to cluster boundary P P P
Seek past cluster boundary P P P
Seek backwards to nonzero offset, pointer > cluster size P P P
Block-read entire file >1 cluster in size, odd size P P P
Seek to odd location in file P P P
Perform <1 sector reads from random file locations P P P
Open nonexistent file for writing in root dir P P P
Open nonexistent file for writing in subdir P P P
Repeat prev. 2 tests on volume with 0 free clusters P P P
Seek past EOF, file open for writing P P P
Open existing file for writing in root dir P P P
Write random-length records to file, 20 clusters total P P P
MS-DOS 6.0 SCANDISK cross-check P P P
Revision History
================
Jan-06-2005 larwe Initial release (1.0)
Jan-29-2006 larwe Bugfix release (1.01)
- Fixed error in FAT12 FAT read on boundary of sector
- Improved compilability under avrgcc
Sep-16-2006 larwe Bugfix release (1.02)
- DFS_Seek would not correctly rewind to start of file
- DFS_Seek would not correctly seek to a position not on a cluster
boundary
- DFS_OpenFile fencepost error caused memory access at [start of
string-1] with a local variable
- DFS_OpenFile could not open a file in the root directory

99
dosfs/tmpstring.c Normal file
View File

@ -0,0 +1,99 @@
#pragma once
#include <stdint.h>
#include <stddef.h>
void *memcpy(void *restrict dest, const void *restrict src, size_t n)
{
unsigned char *d = dest;
const unsigned char *s = src;
for (; n; n--) *d++ = *s++;
return dest;
}
void *memset(void *dest, int c, size_t n)
{
unsigned char *s = dest;
size_t k;
/* Fill head and tail with minimal branching. Each
* conditional ensures that all the subsequently used
* offsets are well-defined and in the dest region. */
if (!n) return dest;
s[0] = c;
s[n-1] = c;
if (n <= 2) return dest;
s[1] = c;
s[2] = c;
s[n-2] = c;
s[n-3] = c;
if (n <= 6) return dest;
s[3] = c;
s[n-4] = c;
if (n <= 8) return dest;
/* Advance pointer to align it at a 4-byte boundary,
* and truncate n to a multiple of 4. The previous code
* already took care of any head/tail that get cut off
* by the alignment. */
k = -(uintptr_t)s & 3;
s += k;
n -= k;
n &= -4;
/* Pure C fallback with no aliasing violations. */
for (; n; n--, s++) *s = c;
return dest;
}
size_t strlen(const char *s)
{
const char *a = s;
for (; *s; s++);
return s-a;
}
int memcmp(const void *vl, const void *vr, size_t n)
{
const unsigned char *l=vl, *r=vr;
for (; n && *l == *r; n--, l++, r++);
return n ? *l-*r : 0;
}
char *strncpy(char *restrict d, const char *restrict s, size_t n)
{
for (; n && (*d=*s); n--, s++, d++);
memset(d, 0, n);
return d;
}
char *strcpy(char *restrict dest, const char *restrict src)
{
char *restrict d = dest;
const char *restrict s = src;
for (; (*d=*s); s++, d++);
return d;
}
int strcmp(const char *l, const char *r)
{
for (; *l==*r && *l; l++, r++);
return *(unsigned char *)l - *(unsigned char *)r;
}
/* STDLIB DIV FUNCTIONS */
typedef struct { int quot, rem; } div_t;
typedef struct { long quot, rem; } ldiv_t;
div_t div(int num, int den)
{
return (div_t){ num/den, num%den };
}
ldiv_t ldiv(long num, long den)
{
return (ldiv_t){ num/den, num%den };
}

2
entry.nasm
View File

@ -77,7 +77,7 @@ div bl ; Unhandled DIV0 exception
global jmp_usermode_test
jmp_usermode_test:
pop eax ; return address
mov ebp, esp ; return stack
mov ecx, esp ; return stack
call save_current_task
mov esp, 0x500000 ; usermode stack
mov eax, 0x20 | 3

2
interrupt.c
View File

@ -175,7 +175,7 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
frame->eip = (uint16_t)(frame->eip + 1);
goto done;
case 0xCD: // INT n
vga[0] = 'I'; vga[2]++; if (vga[2] < '0') vga[2] = '0';
//vga[0] = 'I'; vga[2]++; if (vga[2] < '0') vga[2] = '0';
switch (ip[1]) {
case 0x30:
return_prev_task();

1
interrupt.h
View File

@ -27,6 +27,7 @@ typedef uint32_t FARPTR;
#define EFLAG_IF ((uint32_t)1 << 9)
#define EFLAG_VM ((uint32_t)1 << 17)
FARPTR i386LinearToFp(void *ptr);
__attribute__ ((interrupt))

122
kernel.c
View File

@ -1,5 +1,6 @@
#include <stdint.h>
#include "dosfs/dosfs.h"
#include "print.h"
#include "interrupt.h"
@ -52,13 +53,21 @@ void print_cr4() {
printDword(reg, 0xB8000 + (160*5) + 50 + 8*4 + 4);
}
__attribute((__no_caller_saved_registers__))
struct __attribute((__packed__)) Int13DiskPacket_t {
uint8_t size; // 0x10
uint8_t reserved; // 0x00
uint16_t blocks;
uint32_t transfer_buffer; // 0x2300:0000
uint64_t start_block;
};
extern struct Int13DiskPacket_t v86disk_addr_packet;
extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
extern void v86Test();
extern void v86GfxMode();
extern void v86TextMode();
extern void v86DiskRead();
__attribute((__no_caller_saved_registers__))
extern char *jmp_usermode_test();
__attribute((__no_caller_saved_registers__))
extern void kbd_wait();
@ -88,6 +97,92 @@ Protected Only (1MB+)
400000 - 500000 Usermode Stack (1mB)
*/
void TestV86() {
FARPTR v86_entry = i386LinearToFp(v86Test);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
}
void TestGfx() {
FARPTR v86_entry = i386LinearToFp(v86GfxMode);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
char *vga = jmp_usermode_test();
for (int i = 0; i < 320; i++) {
vga[i] = i;
}
}
void TestDiskRead() {
FARPTR v86_entry = i386LinearToFp(v86TextMode);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
v86_entry = i386LinearToFp(v86DiskRead);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
word *vga_text = (word *)0xb8000;
char *diskReadBuf = (char *)0x23000;
for (int i = 0; i < (80*25)/2; i++) {
printByte(diskReadBuf[i], &vga_text[i*2]);
}
}
void TestFAT() {
word *vga_text = (word *)0xb8000;
uint8_t *diskReadBuf = (uint8_t *)0x23000;
for (int i = 0; i < 80*25; i++)
vga_text[i] = 0x0f00;
VOLINFO vi;
uint8_t pactive, ptype;
uint32_t pstart, psize;
pstart = DFS_GetPtnStart(0, diskReadBuf, 0, &pactive, &ptype, &psize);
vga_text = (word *)0xb8000;
vga_text += printStr("PartStart: ", vga_text);
vga_text += printDword(pstart, vga_text);
vga_text += 2;
vga_text += printStr("PartSize: ", vga_text);
vga_text += printDword(psize, vga_text);
vga_text += 2;
vga_text += printStr("PartActive: ", vga_text);
vga_text += printByte(pactive, vga_text);
vga_text += 2;
vga_text += printStr("PartType: ", vga_text);
vga_text += printByte(ptype, vga_text);
vga_text = (word *)((((((uintptr_t)vga_text)-0xb8000) - ((((uintptr_t)vga_text)-0xb8000) % 160)) + 160)+0xb8000);
DFS_GetVolInfo(0, diskReadBuf, pstart, &vi);
vga_text += printStr("Label: ", vga_text);
vga_text += printStr((char*)vi.label, vga_text);
vga_text += 2;
vga_text += printStr("Sec/Clus: ", vga_text);
vga_text += printByte(vi.secperclus, vga_text);
vga_text += 2;
vga_text += printStr("ResrvSec: ", vga_text);
vga_text += printWord(vi.reservedsecs, vga_text);
vga_text += 2;
vga_text += printStr("NumSec: ", vga_text);
vga_text += printDword(vi.numsecs, vga_text);
vga_text += 2;
vga_text += printStr("Sec/FAT: ", vga_text);
vga_text += printDword(vi.secperfat, vga_text);
vga_text += 2;
vga_text += printStr("FAT1@: ", vga_text);
vga_text += printDword(vi.fat1, vga_text);
vga_text += 2;
vga_text += printStr("ROOT@: ", vga_text);
vga_text += printDword(vi.rootdir, vga_text);
vga_text = (word *)((((((uintptr_t)vga_text)-0xb8000) - ((((uintptr_t)vga_text)-0xb8000) % 160)) + 160)+0xb8000);
vga_text += printStr("Files in root:", vga_text);
vga_text = (word *)((((((uintptr_t)vga_text)-0xb8000) - ((((uintptr_t)vga_text)-0xb8000) % 160)) + 160)+0xb8000);
DIRINFO di;
DIRENT de;
di.scratch = 0x23000;
while (!DFS_GetNext(&vi, &di, &de)) {
if (de.name[0]) {
for (int i = 0; i < 11 && de.name[i]; i++) {
*(uint8_t *)vga_text = de.name[i];
vga_text++;
}
vga_text = (word *)((((((uintptr_t)vga_text)-0xb8000) - ((((uintptr_t)vga_text)-0xb8000) % 160)) + 160)+0xb8000);
}
}
}
void start() {
word *vga_text = (word *)0xb8000;
char h[] = "LuciaOS";
@ -122,25 +217,14 @@ void start() {
print_cr0();
print_cr3();
print_cr4();
FARPTR v86_entry = i386LinearToFp(v86Test);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
v86_entry = i386LinearToFp(v86GfxMode);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
char *vga = jmp_usermode_test();
//asm ("xchgw %bx, %bx");
for (int i = 0; i < 320; i++) {
vga[i] = i;
}
TestV86(); // has int 3 wait in v86
TestGfx();
kbd_wait();
TestDiskRead();
kbd_wait();
TestFAT();
kbd_wait();
v86_entry = i386LinearToFp(v86TextMode);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
v86_entry = i386LinearToFp(v86DiskRead);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
vga_text = (word *)0xb8000;
char *bootloader = (char *)0x23000;
for (int i = 0; i < (80*25)/2; i++) {
printByte(bootloader[i], &vga_text[i*2]);
}
}

16
print.c
View File

@ -3,15 +3,25 @@
char nibbleToHex(uint8_t n) {
return n > 9 ? (n - 10) + 'A' : n + '0';
}
void printByte(uint8_t v, uint16_t *buff) {
uintptr_t printByte(uint8_t v, uint16_t *buff) {
*(char *)&buff[0] = nibbleToHex((v >> 4) & 0xF);
*(char *)&buff[1] = nibbleToHex(v & 0xF);
return 2;
}
void printWord(uint16_t v, uint16_t *buff) {
uintptr_t printWord(uint16_t v, uint16_t *buff) {
printByte(v >> 8, buff);
printByte(v, &buff[2]);
return 4;
}
void printDword(uint32_t v, uint16_t *buff) {
uintptr_t printDword(uint32_t v, uint16_t *buff) {
printWord(v >> 16, buff);
printWord(v, &buff[4]);
return 8;
}
uintptr_t printStr(char *v, uint16_t *buff) {
char *s;
for (s = v;*s;s++,buff++)
*(char*)buff = *s;
return s - v;
}

7
print.h
View File

@ -1,6 +1,7 @@
#pragma once
#include <stdint.h>
void printByte(uint8_t v, uint16_t *buff);
void printWord(uint16_t v, uint16_t *buff);
void printDword(uint32_t v, uint16_t *buff);
uintptr_t printByte(uint8_t v, uint16_t *buff);
uintptr_t printWord(uint16_t v, uint16_t *buff);
uintptr_t printDword(uint32_t v, uint16_t *buff);
uintptr_t printStr(char *v, uint16_t *buff);

54
task.nasm
View File

@ -1,12 +1,16 @@
task_ptr: equ (0x310000-4)
; return address in EAX
; return stack in ECX
; we can modify EAX, ECX, EDX
; i.e. save all others in task
global save_current_task
save_current_task:
push ebx
mov ebx, esp
push edx
mov edx, esp ; EDX holds our tmp stack, unsaved
mov esp, dword [task_ptr] ; load current task pointer
push ss
push ebp ; return stack
push ecx ; return stack
pushfd
push cs
push eax ; return address
@ -14,33 +18,41 @@ push ds ; other segs, pop
push es ; before iret
push fs ; in exit handler
push gs
push ebp ; saved
push ebx ; saved
push esi ; saved
push edi ; saved
mov dword [task_ptr], esp ; save new task pointer
mov esp, ebx
pop ebx
mov esp, edx
pop edx
ret
global return_prev_task
return_prev_task:
mov edi, eax ; save for later
mov esi, dword [task_ptr] ; load current task pointer
add dword [task_ptr], 36 ; adjust to last task pointer
mov eax, [esi+0] ; gs
mov ecx, eax ; save return value for later
mov edx, dword [task_ptr] ; load current task pointer
add dword [task_ptr], 52 ; adjust to last task pointer
mov edi, [edx+0]
mov esi, [edx+4]
mov ebx, [edx+8]
mov ebp, [edx+12]
mov eax, [edx+0+16] ; gs
mov gs, ax
mov eax, [esi+4] ; fs
mov eax, [edx+4+16] ; fs
mov fs, ax
mov eax, [esi+8] ; es
mov eax, [edx+8+16] ; es
mov es, ax
mov ebx, [esi+16] ; eip
mov ecx, [esi+20] ; cs
mov edx, [esi+24] ; eflags
; SS:ESP <- return stack
mov esp, [esi+28] ; esp
mov eax, [esi+32] ; ss
mov esp, [edx+28+16] ; esp
mov eax, [edx+32+16] ; ss
mov ss, ax
mov eax, [esi+12] ; ds
mov eax, [edx+24+16] ; eflags
push eax
mov eax, [edx+20+16] ; cs
push eax
mov eax, [edx+16+16] ; eip
push eax
mov eax, [edx+12+16] ; ds
mov ds, ax
push edx ; eflags
push ecx ; cs
push ebx ; eip
mov eax, edi ; restore return value
mov eax, ecx ; restore return value
iret

2
tss.c
View File

@ -42,7 +42,7 @@ void write_tss() {
// not technically TSS but set up task pointer
uint32_t *current_task_ptr = (uint32_t*)(0x310000-4);
*current_task_ptr = 0x310000-40; // each task is 9 dwords, plus 1 for pointer
*current_task_ptr = 0x310000-(20*4); // each task is 12 dwords, plus 1 for pointer
/* TODO setup null recovery task at start */
}
extern void flushTSS();

10
v86.nasm
View File

@ -67,18 +67,20 @@ mov si, v86disk_addr_packet ; ds:si
int 0x13
int 0x30
jmp $
global v86disk_addr_packet
v86disk_addr_packet:
db 0x10, 0x00 ; size, reserved
dw 0x20 ; blocks
dw 0x1 ; blocks
dd 0x23000000 ; transfer buffer 0x23000
dq 0 ; start block
dq 0x1 ; start block
[BITS 32]
; extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
global enter_v86
enter_v86:
pop eax
mov ebp, esp ; save stack pointer
pop eax ; return address
mov ecx, esp ; return stack
call save_current_task
mov ebp, esp ; save stack pointer
push dword [ebp+0] ; ss
push dword [ebp+4] ; esp
pushfd ; eflags