diff --git a/Boot486/boot0.S b/Boot486/boot0.S
index 21608cbc66d797064902c57826ca8fb215702b46..9ff81fabebf11bf2e9238c4cedc89178d7359357 100644 (file)
--- a/Boot486/boot0.S
+++ b/Boot486/boot0.S
# Stage 1
# =========================================================================== #
-.code16
_start:
+
+.code16
stage1:
# 1. Setup canonical %cs:%eip, segment registers %ds, %es, %fs, %gs, %ss and stack %sp
cli
mov %dx, BootDiskAdr
call mapmem
+ sti
# 2. Enable A20 gate
- call enable_A20
- sti
+ call enableA20
# 3. Reset disk controller (%dl and %dh initialized by bios) and read Kernel into buffer
movl $(kernel_code_end - kernel_code_start), KernelSizeAdr
ret
# =========================================================================== #
-# Check that A20 Gate is enabled
-# output: set zero flag if disabled
-# restore: %ds %es
+# Enable A20 Line
# =========================================================================== #
.code16
-check_A20:
- push %ds
- push %es
-# push %ax
-# push %di
-# push %si
-
- xor %ax, %ax
- mov %ax, %es
-
- not %ax
- mov %ax, %ds
-
- mov $0x0500, %di
- mov $0x0510, %si
-
- mov %es:0(%di), %al
- push %ax
-
- mov %ds:0(%si), %al
- push %ax
-
- movb $0x00, %es:0(%di)
- movb $0xff, %ds:0(%si)
-
- cmpb $0xff, %es:0(%di)
-
- pop %ax
- mov %es:0(%di), %al
-
- pop %ax
- mov %es:0(%di), %al
-
- mov $0, %ax
-
- je check_A20__exit
-
- mov $1, %ax
-
-check_A20__exit:
-# pop %si
-# pop %di
-# pop %ax
- pop %es
- pop %ds
- or %al, %al
- ret
-
-# =========================================================================== #
-# Enable A20 Gate
-# =========================================================================== #
-
-enable_A20:
- /* First check */
- call check_A20
- jnz enable_A20__success
- /* BIOS method */
- mov $0x2401, %ax
- int $0x15
-
- call check_A20
- jnz enable_A20__success
-
- /* Keyboard method 1 */
- mov $0xd0, %al
- out %al, $0x64
-
- call check_A20
- jnz enable_A20__success
-
- /* Keyboard method 2 */
-/*
-# cli
-
- call enable_A20__wait1
- mov $0xad, %al
- out %al, $0x64
-
- call enable_A20__wait1
- mov $0xd0, %al
- out %al, $0x64
-
- enable_A20__wait2:
+enableA20:
+ cli
+ xor %cx, %cx
+enableA20_1:
+ inc %cx
+ jz enableA20_3
in $0x64, %al
- test $1, %al
- jz enable_A20__wait2
-
- in $0x60, %al
- push %eax
-
- call enable_A20__wait1
+ test $0x2, %al
+ jnz enableA20_1
mov $0xd1, %al
out %al, $0x64
-
- call enable_A20__wait1
- pop %eax
- or $2, %al
- out %al, $0x64
-
- call enable_A20__wait1
- mov $0xae, %al
- out %al, $0x64
-
- call enable_A20__wait1
-# sti
-
-# call check_A20
-# jnz enable_A20__success
-*/
-
- /* Control port A method */
- mov $1, %al
- out %al, $0x92
-
- call check_A20
- jnz enable_A20__success
-
- /* Fast method */
- in $0xee, %al
-
- call check_A20
- jnz enable_A20__success
-
- mov $msg_a20_failed, %si
- call print
-# cli
-# hlt
-
-enable_A20__success:
- ret
-
-/*
-enable_A20__wait1:
+enableA20_2:
in $0x64, %al
- test $2, %al
- jnz enable_A20__wait1
+ test $0x2, %al
+ jnz enableA20_2
+ mov $0xdf, %al
+ out %al, $0x60
+enableA20_3:
+ sti
ret
-*/
# =========================================================================== #
# =========================================================================== #
# =========================================================================== #
msg_mapmem_failed: .asciz "1"
-msg_a20_failed: .asciz "2"
msg_chs_error: .asciz "3"
msg_kernel_read_failed: .asciz "4"
-
msg_protected_mode: .asciz ">5"
current_sector: