| 34,6 → 34,15 |
|---|
| # |
| |
| |
| # KERNEL_SIZE is passed from the outside to the preprocessor |
| #if (KERNEL_SIZE%512>0) |
| #define TAIL 1 |
| #else |
| #define TAIL 0 |
| #endif |
| |
| #define SECTORS (KERNEL_SIZE/512+TAIL) |
| |
| .text |
| .global _start_0x7c00 |
| |
| 41,28 → 50,23 |
|---|
| _start_0x7c00: |
| xorw %ax,%ax # reset, %al will be used below |
| movw %ax,%dx # fd0, %dh and %dl will be used below |
| int $0x13 |
| jc stop_trying |
| movw %dx,%ds |
| |
| movb $2,%ah # read |
| incb %al # one sector |
| movb %ah,%cl # from disk sector 2 |
| movw %dx,%es |
| movw $0x8000,%bx # at %es:%bx |
| int $0x13 |
| movw %dx,%ss # initialize stack |
| movw $stack,%sp |
| |
| int $0x13 # reset floppy |
| jc stop_trying |
| |
| pushw $('.') |
| call echo_mark |
| add $2,%sp |
| |
| movw %dx,%ds |
| movw %dx,%ss |
| movw $0x7c00,%sp |
| movw $0xffe0,%si # after next increment, %si will become 0x0000 |
| movw %si,%es |
| movw $0x8000,%bx # at %es:%bx |
| |
| # KERNEL_SIZE is passed from the outside to the preprocessor |
| movl $(KERNEL_SIZE),%edi |
| movl $(SECTORS),%edi |
| |
| shrl $9,%edi # number of sectors that kernel occupies (%edi div 512) |
| |
| read_next: |
| test %edi,%edi |
| jnz read_sectors |
| 71,16 → 75,14 |
|---|
| movw $0x3f2,%dx |
| outb %al,%dx |
| |
| pushw $('$') |
| movb $('$'),%al |
| call echo_mark |
| add $2,%sp |
| |
| jmpl $0,$0x8000 |
| |
| read_sectors: |
| pushw $('.') |
| movb $('.'),%al |
| call echo_mark |
| add $2,%sp |
| |
| decl %edi |
| incw logical_sector |
| 104,9 → 106,8 |
|---|
| int $0x13 |
| jnc read_next |
| |
| pushw $('R') |
| movb $('R'),%al |
| call echo_mark |
| add $2,%sp |
| |
| xorw %ax,%ax # try to reset |
| movw %ax,%dx # fd0 |
| 114,9 → 115,8 |
|---|
| jnc read_next |
| |
| stop_trying: |
| pushw $('F') |
| movb $('F'),%al |
| call echo_mark |
| add $2,%sp |
| |
| cli |
| hlt |
| 127,7 → 127,6 |
|---|
| movw %sp,%bp |
| pusha |
| |
| movw CH(%bp),%ax |
| movb $0xe,%ah |
| movb $7,%bl |
| int $0x10 |
| 138,15 → 137,15 |
|---|
| |
| # current logical sector from the beginning of the disk |
| logical_sector: |
| .word 1 |
| .word 0 |
| |
| # number of sectors per track on 1440 floppy |
| sectors: |
| .byte 18 |
| |
| |
| # boot floppy signature |
| .org 0x1fe |
| boot_floppy_signature: |
| .byte 0x55 |
| .byte 0xaa |
| stack: |