3 To build FreeLoader you will need DJGPP because Mingw32 doesn't support 16-bit code
4 ext2 filesystem support needs to be added.
5 The MessageBox() function needs to not allocate memory. Because it gets called when memory allocation fails.
9 0000:0000 - 0000:0FFF: Interrupt vector table & BIOS data
10 0000:1000 - 0000:6FFF: Real mode stack area
11 0000:7000 - 0000:7FFF: Unused
12 0000:8000 - xxxx:xxxx: FreeLoader program & data area
13 xxxx:xxxx - 7000:7FFF: Random memory allocation heap
14 7000:8000 - 7000:FFFF: Protected mode stack area
15 8000:0000 - 8000:FFFF: File system read buffer
16 9000:0000 - 9000:FFFF: Disk read buffer for BIOS Int 13h
17 A000:0000 - FFFF:FFFF: reserved
20 FreeLoader Boot Process
22 FAT 12/16/32 Boot Sector
24 The BIOS loads the boot sector at 0000:7C00. The FAT32 boot sector
25 relocates itself higher in memory at 9000:0000 and loads it's extra sector
26 at 9000:0200 and then looks for freeldr.sys on the file system. Once found
27 it loads freeldr.sys to 0000:7E00 and then jumps to it's entry point at
28 0000:8000. The FAT12/16 boot sector does no relocation, it just searches for
29 the freeldr.sys and loads the first 512 bytes to 0000:7E00. This extra code
30 enables it to fully navigate the file allocation table. Then it loads
31 freeldr.sys to 0000:7E00 and jumps to it's entry point at 0000:8000. Before
32 FreeLoader gets control the boot sector saves the screen contents to a buffer
33 at 9000:8000 and the cursor x & y position to bytes at 9000:8FA0 & 9000:8FA1
37 ISO-9660 (CD-ROM) Boot Sector
39 The BIOS loads the boot sector (2048 bytes) at 0000:7C00. First, the
40 boot sector relocates itself to 0000:7000 (up to 0000:7800). Then it looks
41 for the I386 directory and makes it the current directory. Next it looks for
42 FREELDR.SYS and loads it at 0000:8000. Finally it restores the boot drive
43 number in the DL register and jumps to FreeLoader's entry point at 0000:8000.
46 FreeLoader Initialization
48 When FreeLoader gets control it saves the boot drive, passed to it in
49 the DL register, and sets up the stack, enables protected mode, and calls