pull/6/head
Carlos Fenollosa 9 years ago
parent 418bb11305
commit c8db77fea9

BIN
.DS_Store vendored

Binary file not shown.

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[bits 32] ; using 32-bit protected mode
; this is how constants are defined
VIDEO_MEMORY equ 0xb8000
WHITE_OB_BLACK equ 0x0f ; the color byte for each character
print_string_pm:
pusha
mov edx, VIDEO_MEMORY
print_string_pm_loop:
mov al, [ebx] ; [ebx] is the address of our character
mov ah, WHITE_OB_BLACK
cmp al, 0 ; check if end of string
je print_string_pm_done
mov [edx], ax ; store character + attribute in video memory
add ebx, 1 ; next char
add edx, 2 ; next video memory position
jmp print_string_pm_loop
print_string_pm_done:
popa
ret

@ -0,0 +1,51 @@
; Identical to lesson 13's boot sector, but the %included files have new paths
[org 0x7c00]
KERNEL_OFFSET equ 0x1000 ; The same one we used when linking the kernel
mov [BOOT_DRIVE], dl ; Remember that the BIOS sets us the boot drive in 'dl' on boot
mov bp, 0x9000
mov sp, bp
mov bx, MSG_REAL_MODE
call print
call print_nl
call load_kernel ; read the kernel from disk
call switch_to_pm ; disable interrupts, load GDT, etc. Finally jumps to 'BEGIN_PM'
jmp $ ; Never executed
%include "boot/print.asm"
%include "boot/print_hex.asm"
%include "boot/disk.asm"
%include "boot/gdt.asm"
%include "boot/32bit_print.asm"
%include "boot/switch_pm.asm"
[bits 16]
load_kernel:
mov bx, MSG_LOAD_KERNEL
call print
call print_nl
mov bx, KERNEL_OFFSET ; Read from disk and store in 0x1000
mov dh, 16 ; Our future kernel will be larger, make this big
mov dl, [BOOT_DRIVE]
call disk_load
ret
[bits 32]
BEGIN_PM:
mov ebx, MSG_PROT_MODE
call print_string_pm
call KERNEL_OFFSET ; Give control to the kernel
jmp $ ; Stay here when the kernel returns control to us (if ever)
BOOT_DRIVE db 0 ; It is a good idea to store it in memory because 'dl' may get overwritten
MSG_REAL_MODE db "Started in 16-bit Real Mode", 0
MSG_PROT_MODE db "Landed in 32-bit Protected Mode", 0
MSG_LOAD_KERNEL db "Loading kernel into memory", 0
; padding
times 510 - ($-$$) db 0
dw 0xaa55

@ -0,0 +1,46 @@
; load 'dh' sectors from drive 'dl' into ES:BX
disk_load:
pusha
; reading from disk requires setting specific values in all registers
; so we will overwrite our input parameters from 'dx'. Let's save it
; to the stack for later use.
push dx
mov ah, 0x02 ; ah <- int 0x13 function. 0x02 = 'read'
mov al, dh ; al <- number of sectors to read (0x01 .. 0x80)
mov cl, 0x02 ; cl <- sector (0x01 .. 0x11)
; 0x01 is our boot sector, 0x02 is the first 'available' sector
mov ch, 0x00 ; ch <- cylinder (0x0 .. 0x3FF, upper 2 bits in 'cl')
; dl <- drive number. Our caller sets it as a parameter and gets it from BIOS
; (0 = floppy, 1 = floppy2, 0x80 = hdd, 0x81 = hdd2)
mov dh, 0x00 ; dh <- head number (0x0 .. 0xF)
; [es:bx] <- pointer to buffer where the data will be stored
; caller sets it up for us, and it is actually the standard location for int 13h
int 0x13 ; BIOS interrupt
jc disk_error ; if error (stored in the carry bit)
pop dx
cmp al, dh ; BIOS also sets 'al' to the # of sectors read. Compare it.
jne sectors_error
popa
ret
disk_error:
mov bx, DISK_ERROR
call print
call print_nl
mov dh, ah ; ah = error code, dl = disk drive that dropped the error
call print_hex ; check out the code at http://stanislavs.org/helppc/int_13-1.html
jmp disk_loop
sectors_error:
mov bx, SECTORS_ERROR
call print
disk_loop:
jmp $
DISK_ERROR: db "Disk read error", 0
SECTORS_ERROR: db "Incorrect number of sectors read", 0

@ -0,0 +1,35 @@
gdt_start: ; don't remove the labels, they're needed to compute sizes and jumps
; the GDT starts with a null 8-byte
dd 0x0 ; 4 byte
dd 0x0 ; 4 byte
; GDT for code segment. base = 0x00000000, length = 0xfffff
; for flags, refer to os-dev.pdf document, page 36
gdt_code:
dw 0xffff ; segment length, bits 0-15
dw 0x0 ; segment base, bits 0-15
db 0x0 ; segment base, bits 16-23
db 10011010b ; flags (8 bits)
db 11001111b ; flags (4 bits) + segment length, bits 16-19
db 0x0 ; segment base, bits 24-31
; GDT for data segment. base and length identical to code segment
; some flags changed, again, refer to os-dev.pdf
gdt_data:
dw 0xffff
dw 0x0
db 0x0
db 10010010b
db 11001111b
db 0x0
gdt_end:
; GDT descriptor
gdt_descriptor:
dw gdt_end - gdt_start - 1 ; size (16 bit), always one less of its true size
dd gdt_start ; address (32 bit)
; define some constants for later use
CODE_SEG equ gdt_code - gdt_start
DATA_SEG equ gdt_data - gdt_start

@ -0,0 +1,4 @@
[bits 32]
[extern main] ; Define calling point. Must have same name as kernel.c 'main' function
call main ; Calls the C function. The linker will know where it is placed in memory
jmp $

@ -0,0 +1,37 @@
print:
pusha
; keep this in mind:
; while (string[i] != 0) { print string[i]; i++ }
; the comparison for string end (null byte)
start:
mov al, [bx] ; 'bx' is the base address for the string
cmp al, 0
je done
; the part where we print with the BIOS help
mov ah, 0x0e
int 0x10 ; 'al' already contains the char
; increment pointer and do next loop
add bx, 1
jmp start
done:
popa
ret
print_nl:
pusha
mov ah, 0x0e
mov al, 0x0a ; newline char
int 0x10
mov al, 0x0d ; carriage return
int 0x10
popa
ret

@ -0,0 +1,46 @@
; receiving the data in 'dx'
; For the examples we'll assume that we're called with dx=0x1234
print_hex:
pusha
mov cx, 0 ; our index variable
; Strategy: get the last char of 'dx', then convert to ASCII
; Numeric ASCII values: '0' (ASCII 0x30) to '9' (0x39), so just add 0x30 to byte N.
; For alphabetic characters A-F: 'A' (ASCII 0x41) to 'F' (0x46) we'll add 0x40
; Then, move the ASCII byte to the correct position on the resulting string
hex_loop:
cmp cx, 4 ; loop 4 times
je end
; 1. convert last char of 'dx' to ascii
mov ax, dx ; we will use 'ax' as our working register
and ax, 0x000f ; 0x1234 -> 0x0004 by masking first three to zeros
add al, 0x30 ; add 0x30 to N to convert it to ASCII "N"
cmp al, 0x39 ; if > 9, add extra 8 to represent 'A' to 'F'
jle step2
add al, 7 ; 'A' is ASCII 65 instead of 58, so 65-58=7
step2:
; 2. get the correct position of the string to place our ASCII char
; bx <- base address + string length - index of char
mov bx, HEX_OUT + 5 ; base + length
sub bx, cx ; our index variable
mov [bx], al ; copy the ASCII char on 'al' to the position pointed by 'bx'
ror dx, 4 ; 0x1234 -> 0x4123 -> 0x3412 -> 0x2341 -> 0x1234
; increment index and loop
add cx, 1
jmp hex_loop
end:
; prepare the parameter and call the function
; remember that print receives parameters in 'bx'
mov bx, HEX_OUT
call print
popa
ret
HEX_OUT:
db '0x0000',0 ; reserve memory for our new string

@ -0,0 +1,22 @@
[bits 16]
switch_to_pm:
cli ; 1. disable interrupts
lgdt [gdt_descriptor] ; 2. load the GDT descriptor
mov eax, cr0
or eax, 0x1 ; 3. set 32-bit mode bit in cr0
mov cr0, eax
jmp CODE_SEG:init_pm ; 4. far jump by using a different segment
[bits 32]
init_pm: ; we are now using 32-bit instructions
mov ax, DATA_SEG ; 5. update the segment registers
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000 ; 6. update the stack right at the top of the free space
mov esp, ebp
call BEGIN_PM ; 7. Call a well-known label with useful code

@ -0,0 +1,26 @@
[bits 32] ; using 32-bit protected mode
; this is how constants are defined
VIDEO_MEMORY equ 0xb8000
WHITE_OB_BLACK equ 0x0f ; the color byte for each character
print_string_pm:
pusha
mov edx, VIDEO_MEMORY
print_string_pm_loop:
mov al, [ebx] ; [ebx] is the address of our character
mov ah, WHITE_OB_BLACK
cmp al, 0 ; check if end of string
je print_string_pm_done
mov [edx], ax ; store character + attribute in video memory
add ebx, 1 ; next char
add edx, 2 ; next video memory position
jmp print_string_pm_loop
print_string_pm_done:
popa
ret

@ -0,0 +1,51 @@
; Identical to lesson 13's boot sector, but the %included files have new paths
[org 0x7c00]
KERNEL_OFFSET equ 0x1000 ; The same one we used when linking the kernel
mov [BOOT_DRIVE], dl ; Remember that the BIOS sets us the boot drive in 'dl' on boot
mov bp, 0x9000
mov sp, bp
mov bx, MSG_REAL_MODE
call print
call print_nl
call load_kernel ; read the kernel from disk
call switch_to_pm ; disable interrupts, load GDT, etc. Finally jumps to 'BEGIN_PM'
jmp $ ; Never executed
%include "boot/print.asm"
%include "boot/print_hex.asm"
%include "boot/disk.asm"
%include "boot/gdt.asm"
%include "boot/32bit_print.asm"
%include "boot/switch_pm.asm"
[bits 16]
load_kernel:
mov bx, MSG_LOAD_KERNEL
call print
call print_nl
mov bx, KERNEL_OFFSET ; Read from disk and store in 0x1000
mov dh, 16 ; Our future kernel will be larger, make this big
mov dl, [BOOT_DRIVE]
call disk_load
ret
[bits 32]
BEGIN_PM:
mov ebx, MSG_PROT_MODE
call print_string_pm
call KERNEL_OFFSET ; Give control to the kernel
jmp $ ; Stay here when the kernel returns control to us (if ever)
BOOT_DRIVE db 0 ; It is a good idea to store it in memory because 'dl' may get overwritten
MSG_REAL_MODE db "Started in 16-bit Real Mode", 0
MSG_PROT_MODE db "Landed in 32-bit Protected Mode", 0
MSG_LOAD_KERNEL db "Loading kernel into memory", 0
; padding
times 510 - ($-$$) db 0
dw 0xaa55

@ -0,0 +1,46 @@
; load 'dh' sectors from drive 'dl' into ES:BX
disk_load:
pusha
; reading from disk requires setting specific values in all registers
; so we will overwrite our input parameters from 'dx'. Let's save it
; to the stack for later use.
push dx
mov ah, 0x02 ; ah <- int 0x13 function. 0x02 = 'read'
mov al, dh ; al <- number of sectors to read (0x01 .. 0x80)
mov cl, 0x02 ; cl <- sector (0x01 .. 0x11)
; 0x01 is our boot sector, 0x02 is the first 'available' sector
mov ch, 0x00 ; ch <- cylinder (0x0 .. 0x3FF, upper 2 bits in 'cl')
; dl <- drive number. Our caller sets it as a parameter and gets it from BIOS
; (0 = floppy, 1 = floppy2, 0x80 = hdd, 0x81 = hdd2)
mov dh, 0x00 ; dh <- head number (0x0 .. 0xF)
; [es:bx] <- pointer to buffer where the data will be stored
; caller sets it up for us, and it is actually the standard location for int 13h
int 0x13 ; BIOS interrupt
jc disk_error ; if error (stored in the carry bit)
pop dx
cmp al, dh ; BIOS also sets 'al' to the # of sectors read. Compare it.
jne sectors_error
popa
ret
disk_error:
mov bx, DISK_ERROR
call print
call print_nl
mov dh, ah ; ah = error code, dl = disk drive that dropped the error
call print_hex ; check out the code at http://stanislavs.org/helppc/int_13-1.html
jmp disk_loop
sectors_error:
mov bx, SECTORS_ERROR
call print
disk_loop:
jmp $
DISK_ERROR: db "Disk read error", 0
SECTORS_ERROR: db "Incorrect number of sectors read", 0

@ -0,0 +1,35 @@
gdt_start: ; don't remove the labels, they're needed to compute sizes and jumps
; the GDT starts with a null 8-byte
dd 0x0 ; 4 byte
dd 0x0 ; 4 byte
; GDT for code segment. base = 0x00000000, length = 0xfffff
; for flags, refer to os-dev.pdf document, page 36
gdt_code:
dw 0xffff ; segment length, bits 0-15
dw 0x0 ; segment base, bits 0-15
db 0x0 ; segment base, bits 16-23
db 10011010b ; flags (8 bits)
db 11001111b ; flags (4 bits) + segment length, bits 16-19
db 0x0 ; segment base, bits 24-31
; GDT for data segment. base and length identical to code segment
; some flags changed, again, refer to os-dev.pdf
gdt_data:
dw 0xffff
dw 0x0
db 0x0
db 10010010b
db 11001111b
db 0x0
gdt_end:
; GDT descriptor
gdt_descriptor:
dw gdt_end - gdt_start - 1 ; size (16 bit), always one less of its true size
dd gdt_start ; address (32 bit)
; define some constants for later use
CODE_SEG equ gdt_code - gdt_start
DATA_SEG equ gdt_data - gdt_start

@ -0,0 +1,4 @@
[bits 32]
[extern main] ; Define calling point. Must have same name as kernel.c 'main' function
call main ; Calls the C function. The linker will know where it is placed in memory
jmp $

@ -0,0 +1,37 @@
print:
pusha
; keep this in mind:
; while (string[i] != 0) { print string[i]; i++ }
; the comparison for string end (null byte)
start:
mov al, [bx] ; 'bx' is the base address for the string
cmp al, 0
je done
; the part where we print with the BIOS help
mov ah, 0x0e
int 0x10 ; 'al' already contains the char
; increment pointer and do next loop
add bx, 1
jmp start
done:
popa
ret
print_nl:
pusha
mov ah, 0x0e
mov al, 0x0a ; newline char
int 0x10
mov al, 0x0d ; carriage return
int 0x10
popa
ret

@ -0,0 +1,46 @@
; receiving the data in 'dx'
; For the examples we'll assume that we're called with dx=0x1234
print_hex:
pusha
mov cx, 0 ; our index variable
; Strategy: get the last char of 'dx', then convert to ASCII
; Numeric ASCII values: '0' (ASCII 0x30) to '9' (0x39), so just add 0x30 to byte N.
; For alphabetic characters A-F: 'A' (ASCII 0x41) to 'F' (0x46) we'll add 0x40
; Then, move the ASCII byte to the correct position on the resulting string
hex_loop:
cmp cx, 4 ; loop 4 times
je end
; 1. convert last char of 'dx' to ascii
mov ax, dx ; we will use 'ax' as our working register
and ax, 0x000f ; 0x1234 -> 0x0004 by masking first three to zeros
add al, 0x30 ; add 0x30 to N to convert it to ASCII "N"
cmp al, 0x39 ; if > 9, add extra 8 to represent 'A' to 'F'
jle step2
add al, 7 ; 'A' is ASCII 65 instead of 58, so 65-58=7
step2:
; 2. get the correct position of the string to place our ASCII char
; bx <- base address + string length - index of char
mov bx, HEX_OUT + 5 ; base + length
sub bx, cx ; our index variable
mov [bx], al ; copy the ASCII char on 'al' to the position pointed by 'bx'
ror dx, 4 ; 0x1234 -> 0x4123 -> 0x3412 -> 0x2341 -> 0x1234
; increment index and loop
add cx, 1
jmp hex_loop
end:
; prepare the parameter and call the function
; remember that print receives parameters in 'bx'
mov bx, HEX_OUT
call print
popa
ret
HEX_OUT:
db '0x0000',0 ; reserve memory for our new string

@ -0,0 +1,22 @@
[bits 16]
switch_to_pm:
cli ; 1. disable interrupts
lgdt [gdt_descriptor] ; 2. load the GDT descriptor
mov eax, cr0
or eax, 0x1 ; 3. set 32-bit mode bit in cr0
mov cr0, eax
jmp CODE_SEG:init_pm ; 4. far jump by using a different segment
[bits 32]
init_pm: ; we are now using 32-bit instructions
mov ax, DATA_SEG ; 5. update the segment registers
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000 ; 6. update the stack right at the top of the free space
mov esp, ebp
call BEGIN_PM ; 7. Call a well-known label with useful code

@ -0,0 +1,26 @@
[bits 32] ; using 32-bit protected mode
; this is how constants are defined
VIDEO_MEMORY equ 0xb8000
WHITE_OB_BLACK equ 0x0f ; the color byte for each character
print_string_pm:
pusha
mov edx, VIDEO_MEMORY
print_string_pm_loop:
mov al, [ebx] ; [ebx] is the address of our character
mov ah, WHITE_OB_BLACK
cmp al, 0 ; check if end of string
je print_string_pm_done
mov [edx], ax ; store character + attribute in video memory
add ebx, 1 ; next char
add edx, 2 ; next video memory position
jmp print_string_pm_loop
print_string_pm_done:
popa
ret

@ -0,0 +1,51 @@
; Identical to lesson 13's boot sector, but the %included files have new paths
[org 0x7c00]
KERNEL_OFFSET equ 0x1000 ; The same one we used when linking the kernel
mov [BOOT_DRIVE], dl ; Remember that the BIOS sets us the boot drive in 'dl' on boot
mov bp, 0x9000
mov sp, bp
mov bx, MSG_REAL_MODE
call print
call print_nl
call load_kernel ; read the kernel from disk
call switch_to_pm ; disable interrupts, load GDT, etc. Finally jumps to 'BEGIN_PM'
jmp $ ; Never executed
%include "boot/print.asm"
%include "boot/print_hex.asm"
%include "boot/disk.asm"
%include "boot/gdt.asm"
%include "boot/32bit_print.asm"
%include "boot/switch_pm.asm"
[bits 16]
load_kernel:
mov bx, MSG_LOAD_KERNEL
call print
call print_nl
mov bx, KERNEL_OFFSET ; Read from disk and store in 0x1000
mov dh, 16 ; Our future kernel will be larger, make this big
mov dl, [BOOT_DRIVE]
call disk_load
ret
[bits 32]
BEGIN_PM:
mov ebx, MSG_PROT_MODE
call print_string_pm
call KERNEL_OFFSET ; Give control to the kernel
jmp $ ; Stay here when the kernel returns control to us (if ever)
BOOT_DRIVE db 0 ; It is a good idea to store it in memory because 'dl' may get overwritten
MSG_REAL_MODE db "Started in 16-bit Real Mode", 0
MSG_PROT_MODE db "Landed in 32-bit Protected Mode", 0
MSG_LOAD_KERNEL db "Loading kernel into memory", 0
; padding
times 510 - ($-$$) db 0
dw 0xaa55

@ -0,0 +1,46 @@
; load 'dh' sectors from drive 'dl' into ES:BX
disk_load:
pusha
; reading from disk requires setting specific values in all registers
; so we will overwrite our input parameters from 'dx'. Let's save it
; to the stack for later use.
push dx
mov ah, 0x02 ; ah <- int 0x13 function. 0x02 = 'read'
mov al, dh ; al <- number of sectors to read (0x01 .. 0x80)
mov cl, 0x02 ; cl <- sector (0x01 .. 0x11)
; 0x01 is our boot sector, 0x02 is the first 'available' sector
mov ch, 0x00 ; ch <- cylinder (0x0 .. 0x3FF, upper 2 bits in 'cl')
; dl <- drive number. Our caller sets it as a parameter and gets it from BIOS
; (0 = floppy, 1 = floppy2, 0x80 = hdd, 0x81 = hdd2)
mov dh, 0x00 ; dh <- head number (0x0 .. 0xF)
; [es:bx] <- pointer to buffer where the data will be stored
; caller sets it up for us, and it is actually the standard location for int 13h
int 0x13 ; BIOS interrupt
jc disk_error ; if error (stored in the carry bit)
pop dx
cmp al, dh ; BIOS also sets 'al' to the # of sectors read. Compare it.
jne sectors_error
popa
ret
disk_error:
mov bx, DISK_ERROR
call print
call print_nl
mov dh, ah ; ah = error code, dl = disk drive that dropped the error
call print_hex ; check out the code at http://stanislavs.org/helppc/int_13-1.html
jmp disk_loop
sectors_error:
mov bx, SECTORS_ERROR
call print
disk_loop:
jmp $
DISK_ERROR: db "Disk read error", 0
SECTORS_ERROR: db "Incorrect number of sectors read", 0

@ -0,0 +1,35 @@
gdt_start: ; don't remove the labels, they're needed to compute sizes and jumps
; the GDT starts with a null 8-byte
dd 0x0 ; 4 byte
dd 0x0 ; 4 byte
; GDT for code segment. base = 0x00000000, length = 0xfffff
; for flags, refer to os-dev.pdf document, page 36
gdt_code:
dw 0xffff ; segment length, bits 0-15
dw 0x0 ; segment base, bits 0-15
db 0x0 ; segment base, bits 16-23
db 10011010b ; flags (8 bits)
db 11001111b ; flags (4 bits) + segment length, bits 16-19
db 0x0 ; segment base, bits 24-31
; GDT for data segment. base and length identical to code segment
; some flags changed, again, refer to os-dev.pdf
gdt_data:
dw 0xffff
dw 0x0
db 0x0
db 10010010b
db 11001111b
db 0x0
gdt_end:
; GDT descriptor
gdt_descriptor:
dw gdt_end - gdt_start - 1 ; size (16 bit), always one less of its true size
dd gdt_start ; address (32 bit)
; define some constants for later use
CODE_SEG equ gdt_code - gdt_start
DATA_SEG equ gdt_data - gdt_start

@ -0,0 +1,4 @@
[bits 32]
[extern main] ; Define calling point. Must have same name as kernel.c 'main' function
call main ; Calls the C function. The linker will know where it is placed in memory
jmp $

@ -0,0 +1,37 @@
print:
pusha
; keep this in mind:
; while (string[i] != 0) { print string[i]; i++ }
; the comparison for string end (null byte)
start:
mov al, [bx] ; 'bx' is the base address for the string
cmp al, 0
je done
; the part where we print with the BIOS help
mov ah, 0x0e
int 0x10 ; 'al' already contains the char
; increment pointer and do next loop
add bx, 1
jmp start
done:
popa
ret
print_nl:
pusha
mov ah, 0x0e
mov al, 0x0a ; newline char
int 0x10
mov al, 0x0d ; carriage return
int 0x10
popa
ret

@ -0,0 +1,46 @@
; receiving the data in 'dx'
; For the examples we'll assume that we're called with dx=0x1234
print_hex:
pusha
mov cx, 0 ; our index variable
; Strategy: get the last char of 'dx', then convert to ASCII
; Numeric ASCII values: '0' (ASCII 0x30) to '9' (0x39), so just add 0x30 to byte N.
; For alphabetic characters A-F: 'A' (ASCII 0x41) to 'F' (0x46) we'll add 0x40
; Then, move the ASCII byte to the correct position on the resulting string
hex_loop:
cmp cx, 4 ; loop 4 times
je end
; 1. convert last char of 'dx' to ascii
mov ax, dx ; we will use 'ax' as our working register
and ax, 0x000f ; 0x1234 -> 0x0004 by masking first three to zeros
add al, 0x30 ; add 0x30 to N to convert it to ASCII "N"
cmp al, 0x39 ; if > 9, add extra 8 to represent 'A' to 'F'
jle step2
add al, 7 ; 'A' is ASCII 65 instead of 58, so 65-58=7
step2:
; 2. get the correct position of the string to place our ASCII char
; bx <- base address + string length - index of char
mov bx, HEX_OUT + 5 ; base + length
sub bx, cx ; our index variable
mov [bx], al ; copy the ASCII char on 'al' to the position pointed by 'bx'
ror dx, 4 ; 0x1234 -> 0x4123 -> 0x3412 -> 0x2341 -> 0x1234
; increment index and loop
add cx, 1
jmp hex_loop
end:
; prepare the parameter and call the function
; remember that print receives parameters in 'bx'
mov bx, HEX_OUT
call print
popa
ret
HEX_OUT:
db '0x0000',0 ; reserve memory for our new string

@ -0,0 +1,22 @@
[bits 16]
switch_to_pm:
cli ; 1. disable interrupts
lgdt [gdt_descriptor] ; 2. load the GDT descriptor
mov eax, cr0
or eax, 0x1 ; 3. set 32-bit mode bit in cr0
mov cr0, eax
jmp CODE_SEG:init_pm ; 4. far jump by using a different segment
[bits 32]
init_pm: ; we are now using 32-bit instructions
mov ax, DATA_SEG ; 5. update the segment registers
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000 ; 6. update the stack right at the top of the free space
mov esp, ebp
call BEGIN_PM ; 7. Call a well-known label with useful code
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