read.me

John Fine的OS模型// 源代码// C & ASM// 英文

read.me for bootf02.zip
Version 2.0, May 1, 1999
Sample code
by John S. Fine  [e-mail]
I do not place any restrictions on your use of this source code
I do not provide any warranty of the correctness of this source code
_____________________________________________________________________________

  BOOTF.ASM is a coding sample for a bootstrap for a pmode operating system.
It is also a coding sample for cramming lots of operations into very little
code.   The boot code on a FAT diskette or FAT partition is limited to 0x1C0
bytes (0x3E bytes are reserved at the beginning and 0x2 at the end of a 0x200
byte sector).  BOOTF.ASM fits with 0x1A bytes to spare.  In just 0x1A6 bytes of
code and data it:

1)  Enables the A20 gate.
2)  Switches to big real mode
3)  Computes the locations of the FAT, the root directory and the first cluster.
4)  Reads in the root directory
5)  Scans the root directory for a specific file (KERNEL.BIN in the example)
6)  Reads in the FAT
7)  Reads the file (KERNEL.BIN) to RAM starting at physical 1Mb.
8)  Builds two page tables and one page directory mapping:
    a)  The first 4Mb linear to the first 4Mb physical
    b)  Linear FF800000 (where all my protected mode images start) to physical
        RAM starting at 1Mb
    c)  Self map the page directory to the end of linear memory
9)  Switch to protected mode with paging turned on
10) JMP to KERNEL.BIN at linear FF800000
_____________________________________________________________________________

   Included in BOOTF02.ZIP:

   READ.ME      This file.
   BOOTF.ASM    Source code.
   BOOTF.LNK    JLOC control file for linking BOOTF.
   BOOTF.BIN    Prebuilt
   BOOTF.BAT    Commands to make BOOTF.BIN and install it on A:
   GDT.INC      Definitions for GDT (included by BOOTF.ASM).
   GDT_OLD.INC  Part of GDT.INC
   GDT_NEW.INC  Part of GDT.INC
   KERNEL_C.C   Source code for trivial C example of KERNEL.BIN
   KERNEL_C.LNK JLOC control file for linking KERNEL_C
   KERNEL_C.BAT Commands to make KERNEL_C.BIN and copy it to A:KERNEL.BIN
   KERNEL_C.BIN Prebuilt
   KERNEL_A.ASM Source code for trivial ASM example of KERNEL.BIN
   KERNEL_A.BAT Commands to make KERNEL_A.BIN and copy it to A:KERNEL.BIN
   KERNEL_C.BIN Prebuilt

   Also required to rebuild and install:

   NASM (I think version 0.95 or higher will work)
       http://www.cryogen.com/Nasm/
        (but I only tested with version 0.98)
       http://www.erols.com/johnfine/#nasmj
   JLOC
       http://www.erols.com/johnfine/#jloc
   PARTCOPY  (pcopy02.zip contains partcopy.exe)
       http://www.erols.com/johnfine/#partcopy
   DJGPP (if you want to rebuild kernel_c)
       http://www.delorie.com/djgpp