better formatting
e17fee10df1ce706f5a6fe8cdd1e115d44ace038
1 files changed
bsect.asm
diff --git a/bsect.asm b/bsect.asm
index a4b9aac..87b478e 100644
--- a/bsect.asm
+++ b/bsect.asm
@@ -20,56 +20,53 @@
org 0x7c00
cli
- xor ax, ax
- mov ds, ax
- mov ss, ax
- mov sp, 0x7c00 ; setup stack
-
-; now get into protected move (32bit) as kernel is large and has to be loaded high
- mov ax, 0x2401 ; A20 line enable via BIOS
- int 0x15
- jc err
+ xor ax, ax
+ mov ds, ax
+ mov ss, ax
+ mov sp, 0x7c00 ; setup stack
+ mov ax, 0x2401 ; now get into protected move (32bit) as kernel is large and has to be loaded high
+ int 0x15 ; A20 line enable via BIOS
+ jc err
lgdt [gdt_desc]
mov eax, cr0
or eax, 1
mov cr0, eax
- jmp $+2
+ jmp $+2 ; nop
- mov bx, 0x8 ; first descriptor in GDT
+ mov bx, 0x8 ; first descriptor in GDT
mov ds, bx
mov es, bx
mov gs, bx
- and al, 0xFE ; back to real mode
+ and al, 0xFE ; back to real mode
mov cr0, eax
- xor ax,ax ; restore segment values - now limits are removed but seg regs still work as normal
- mov ds, ax
- mov gs, ax
- mov ax, 0x1000 ; segment for kernel load (mem off 0x10000)
- mov es, ax
+ xor ax,ax ; restore segment values - now limits are removed but seg regs still work as normal
+ mov ds, ax
+ mov gs, ax
+ mov ax, 0x1000 ; segment for kernel load (mem off 0x10000)
+ mov es, ax
sti
- ; now in UNREAL mode
-
- mov ax, 1 ; one sector
- xor bx,bx ; offset
- mov cx, 0x1000 ; seg
+ ; now in UNREAL mode
+ mov ax, 1 ; one sector
+ xor bx,bx ; offset
+ mov cx, 0x1000 ; seg
call hddread
read_kernel_setup:
- mov al, [es:0x1f1] ; no of sectors
+ mov al, [es:0x1f1] ; no of sectors
cmp ax, 0
jne read_kernel_setup.next
- mov ax, 4 ; default is 4
+ mov ax, 4 ; default is 4
.next:
- ; ax = count
- mov bx, 512 ; next offset
- mov cx, 0x1000 ; segment
+ ; ax = count
+ mov bx, 512 ; next offset
+ mov cx, 0x1000 ; segment
call hddread
cmp word [es:0x206], 0x204
@@ -77,34 +74,33 @@ read_kernel_setup:
test byte [es:0x211], 1
jz err
- mov byte [es:0x210], 0xe1 ;loader type
- mov byte [es:0x211], 0x81 ;heap use? !! SET Bit5 to Make Kern Quiet
- mov word [es:0x224], 0xde00 ;head_end_ptr
- mov byte [es:0x227], 0x01 ;ext_loader_type / bootloader id
- mov dword [es:0x228], 0x1e000 ;cmd line ptr
+ mov byte [es:0x210], 0xe1 ; loader type
+ mov byte [es:0x211], 0x81 ; heap use? !! SET Bit5 to Make Kern Quiet
+ mov word [es:0x224], 0xde00 ; head_end_ptr
+ mov byte [es:0x227], 0x01 ; ext_loader_type / bootloader id
+ mov dword [es:0x228], 0x1e000 ; cmd line ptr
- ; copy cmd line
- mov si, cmdLine
+ mov si, cmdLine ; copy cmd line
mov di, 0xe000
mov cx, cmdLineLen
- rep movsb ; copies from DS:si to ES:di (0x1e000)
+ rep movsb ; copies from DS:si to ES:di (0x1e000)
- ; modern kernels are bzImage ones (despite name on disk and so
- ; the protected mode part must be loaded at 0x100000
- ; load 127 sectors at a time to 0x2000, then copy to 0x100000
+ ; modern kernels are bzImage ones (despite name on disk and so
+ ; the protected mode part must be loaded at 0x100000
+ ; load 127 sectors at a time to 0x2000, then copy to 0x100000
-;load_kernel
- mov edx, [es:0x1f4] ; bytes to load
+ ; load_kernel
+ mov edx, [es:0x1f4] ; bytes to load
shl edx, 4
call loader
-;load initrd
- mov eax, 0x7fab000; this is the address qemu loads it at
+ ; load initrd
+ mov eax, 0x7fab000 ; this is the address qemu loads it at
mov [highmove_addr],eax ; end of kernel and initrd load address
mov [es:0x218], eax
- mov edx, [initRdSize] ; ramdisk size in bytes
- mov [es:0x21c], edx ; ramdisk size into kernel header
+ mov edx, [initRdSize] ; ramdisk size in bytes
+ mov [es:0x21c], edx ; ramdisk size into kernel header
call loader
kernel_start:
@@ -117,7 +113,7 @@ kernel_start:
mov ss, ax
mov sp, 0xe000
jmp 0x1020:0
- jmp $
+ jmp $ ; infinity
; ================= functions ====================
; length in bytes into edx
@@ -129,9 +125,9 @@ loader:
jl loader.part_2
jz loader.finish
- mov ax, 127 ;count
- xor bx, bx ; offset
- mov cx, 0x2000 ; seg
+ mov ax, 127 ; count
+ xor bx, bx ; offset
+ mov cx, 0x2000 ; seg
push edx
call hddread
call highmove
@@ -140,9 +136,9 @@ loader:
jmp loader.loop
-.part_2: ; load less than 127*512 sectors
- shr edx, 9 ; divide by 512
- inc edx ; increase by one to get final sector if not multiple - otherwise just load junk - doesn't matter
+.part_2: ; load less than 127*512 sectors
+ shr edx, 9 ; divide by 512
+ inc edx ; increase by one to get final sector if not multiple - otherwise just load junk - doesn't matter
mov ax, dx
xor bx,bx
mov cx, 0x2000
@@ -160,7 +156,7 @@ highmove:
mov esi, 0x20000
mov edi, [highmove_addr]
mov edx, 512*127
- mov ecx, 0 ; pointer
+ mov ecx, 0 ; pointer
.loop:
mov eax, [ds:esi]
mov [ds:edi], eax
@@ -172,7 +168,10 @@ highmove:
ret
err:
- jmp $
+ jmp $ ; infinity calls
+; cli
+; hlt
+; jmp err
hddread:
push eax
@@ -182,28 +181,28 @@ hddread:
mov edx, dword [hddLBA]
mov dword [dap.lba], edx
and eax, 0xffff
- add edx, eax ; advance lba pointer
+ add edx, eax ; advance lba pointer
mov [hddLBA], edx
mov ah, 0x42
mov si, dap
- mov dl, 0x80 ; first hdd
+ mov dl, 0x80 ; first hdd
int 0x13
jc err
pop eax
ret
dap:
- db 0x10 ; size
- db 0 ; unused
+ db 0x10 ; size
+ db 0 ; unused
.count:
- dw 0 ; num sectors
+ dw 0 ; num sectors
.offset:
- dw 0 ;dest offset
+ dw 0 ; dest offset
.segment:
- dw 0 ;dest segment
+ dw 0 ; dest segment
.lba:
- dd 0 ; lba low bits
- dd 0 ; lba high bits
+ dd 0 ; lba low bits
+ dd 0 ; lba high bits
;descriptor
gdt_desc:
@@ -214,26 +213,27 @@ gdt_desc:
; flags: Granuality (0=limitinbytes, 1=limitin4kbs), Sz= [0=16bit, 1=32bit], 0, 0
gdt:
- dq 0 ; first entry 0
-;flat data segment
- dw 0FFFFh ; limit[0:15] (aka 4gb)
- dw 0 ; base[0:15]
- db 0 ; base[16:23]
- db 10010010b ; access byte
- db 11001111b ; [7..4]= flags [3..0] = limit[16:19]
- db 0 ; base[24:31]
+ dq 0 ; first entry 0
+ ; flat data segment
+ dw 0FFFFh ; limit[0:15] (aka 4gb)
+ dw 0 ; base[0:15]
+ db 0 ; base[16:23]
+ db 10010010b ; access byte
+ db 11001111b ; [7..4]= flags [3..0] = limit[16:19]
+ db 0 ; base[24:31]
gdt_end:
-; config options
- hddLBA dd 1 ; start address for kernel - subsequent calls are sequential
+ ; config options
+ hddLBA dd 1 ; start address for kernel - subsequent calls are sequential
initRdSize dd initRdSizeDef
-; kernel command line fills up the space, can not exceed address 510
+
+ ; kernel command line fills up the space, can not exceed address 510
cmdLine db cmdLineDef,0
cmdLineLen equ $-cmdLine
-;boot sector magic
- times 510-($-$$) db 0
+ ;boot sector magic
+ times 510-($-$$) db 0
dw 0xaa55
-; this is the end
+ ; this is the end