Experimental bootloader update
This commit is contained in:
Adrien Bourmault
parent
960a949d9c
commit
21c3dd64e0
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@ -14,4 +14,6 @@
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2018/12/06 - Actually started project, began MBR, decided directories organization, created this file and others
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2018/12/06 - Actually started project, began MBR, decided directories organization, created this file and others
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2018/12/08 - MBR actually supports Long Mode Compatibility Verification
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2018/12/08 - MBR actually supports Long Mode Compatibility Verification
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- Added A20 line Enabling to MBR
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- Added A20 line Enabling to MBR
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2018/12/21 - Boot is now in two stages. First stage is 512 MBR code that loads second stage loader from FAT16.
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That second stage loader enables A20, switches into long mode and write colored text =D
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@ -29,7 +29,7 @@ SYSTDIR=kaleid/system
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all: bootloader
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all: bootloader
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boot.mbr.s: $(BOOTDIR)/mbr.s $(BOOTDIR)/mbr.inc
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boot.mbr.s: $(BOOTDIR)/mbr.s
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$(ASM) $(BOOTFLAGS) $(BOOTDIR)/mbr.s -o $(OBJDIR)/boot/mbr.bin
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$(ASM) $(BOOTFLAGS) $(BOOTDIR)/mbr.s -o $(OBJDIR)/boot/mbr.bin
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boot.loader.s: $(BOOTDIR)/loader.s
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boot.loader.s: $(BOOTDIR)/loader.s
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@ -1,27 +0,0 @@
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;=----------------------------------------------------------------------------=;
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; GNU GPL OS/K ;
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; ;
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; Authors: spectral` ;
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; NeoX ;
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; ;
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; Desc: Functions for the OS/K loaders ;
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; (x86_64 architecture only) ;
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;=----------------------------------------------------------------------------=;
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;-------------------------------------------------------------------;
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; Prints the (null-terminated) string at address @es:@si ;
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;-------------------------------------------------------------------;
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PrintB:
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pushad ; saving context
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.pLoop:
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lodsb ; loads the character at @es:@si in @al
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mov bh, 0x00
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mov bl, 0x07
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cmp al,0
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je .pEnd ; while @al, i.e. while we're not hitting '\0'
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mov ah, 0x0E
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int 0x10 ; print character @al in color @bl (BIOS interrupt)
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jmp .pLoop
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.pEnd:
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popad ; restores context
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ret
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@ -7,16 +7,22 @@
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; Desc: Kernel (second stage) Loader for OS/K ;
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; Desc: Kernel (second stage) Loader for OS/K ;
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; (x86_64 architecture only) ;
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; (x86_64 architecture only) ;
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;=----------------------------------------------------------------------------=;
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;=----------------------------------------------------------------------------=;
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[ORG 0x1000]
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pop word [Bootdrv]
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jmp main
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;; DATA
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%define TRAM 0x0B8000 ; [T]ext[RAM]
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%define TRAM 0x0B8000 ; [T]ext[RAM]
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%define VRAM 0x0A0000 ; [V]ideo[RAM]
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%define VRAM 0x0A0000 ; [V]ideo[RAM]
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Bootdrv db 0x00
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[BITS 16]
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[ORG 0x1000]
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mov ax, cs
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mov ds, ax
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mov es, ax
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mov [Bootdrv], dl
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jmp 0x0000:main
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;; DATA
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Bootdrv db 0
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VGA_HEIGHT dq 0
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VGA_HEIGHT dq 0
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VIDEO_MODE dw 0
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VIDEO_MODE dw 0
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@ -96,7 +102,6 @@ GDT64:
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db 0x0 ; Base Address 31:24
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db 0x0 ; Base Address 31:24
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GDT_LENGTH:
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GDT_LENGTH:
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[BITS 16]
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disable_cursor:
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disable_cursor:
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pushf
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pushf
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push eax
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push eax
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@ -160,8 +165,23 @@ Is64bits:
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stc
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stc
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ret
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ret
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;; INCLUDES
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PrintB:
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%include "boot/common.inc" ; for PrintB
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;---------------------------------------------------;
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; Print out a simple string. ;
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; ;
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; Expects: DS:SI = String to print ;
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; ;
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; Returns: None ;
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; ;
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;---------------------------------------------------;
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lodsb ; Load byte from ds:si to al
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or al, al ; If al is empty stop looping
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jz .done ; Done looping and return
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mov ah, 0x0e ; Teletype output
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int 0x10 ; Video interupt
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jmp PrintB ; Loop untill string is null
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.done:
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ret
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main:
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main:
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;; compatibility check
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;; compatibility check
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@ -174,7 +194,7 @@ main:
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mov si, Pass
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mov si, Pass
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call PrintB
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call PrintB
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;; enabling A20
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;; Enabling A20
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mov si, EnA20
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mov si, EnA20
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call PrintB
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call PrintB
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pop si
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pop si
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@ -271,6 +291,23 @@ main32:
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[BITS 64]
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[BITS 64]
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;; FUNCTIONS
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;; FUNCTIONS
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clear:
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;-----------------------------------------------------------------------;
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; x64/LM Clear Text Screen Function ;
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;-----------------------------------------------------------------------;
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mov qword [NextTRAM], TRAM
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mov edi, TRAM
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push rsi
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push rdi
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push rcx
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mov ah, 0
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mov al, 0
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mov rcx, 0x4000 ; traditionnal value
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rep stosw ; fill screen with al while cx > 0
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pop rcx
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pop rsi
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pop rdi
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ret
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write:
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write:
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;-----------------------------------------------------------------------;
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;-----------------------------------------------------------------------;
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@ -320,11 +357,13 @@ write:
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;; DATA
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;; DATA
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txt db 0x09, " Switching to Long Mode... OK", 0x0A, 0x0D, 0
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txt db 0x09, " Switching to Long Mode... OK", 0x0A, 0x0D, 0
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Init db 0x09, " Checking CPUID", 0
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Init db "Booting OS/K !", 0x0D, 0x0A, 0x0D, 0x0A, 0x09, " Checking CPUID...",0
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EnA20 db 0x09, " Enabling A20 line", 0
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Reinit db "Booting OS/K !", 0x0D, 0x0A, 0x0D, 0x0A, 0
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CPUIDD db 0x09, " Checking CPUID...", 0
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EnA20 db 0x09, " Enabling A20 line...", 0
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NoLongMode db 0x0A, 0x0D, "ERROR : Your computer is not designed for x64 OS", 0
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NoLongMode db 0x0A, 0x0D, "ERROR : Your computer is not designed for x64 OS", 0
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Pass db " OK", 0x0A, 0x0D, 0
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Pass db " OK", 0x0A, 0x0D, 0
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NextTRAM dq 0x0B8AA0 ; Last position of cursor
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NextTRAM dq 0x0B8000 ; Last position of cursor
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VIDEO_MODE64 dq 0
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VIDEO_MODE64 dq 0
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VGA_HEIGHT64 dq 0
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VGA_HEIGHT64 dq 0
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VGA_X dq 0x0
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VGA_X dq 0x0
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@ -336,29 +375,38 @@ main64:
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;; INITIALIZE STACK
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;; INITIALIZE STACK
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mov rsp, 0x9F000
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mov rsp, 0x9F000
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;; NOTIFYING
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call clear
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;; Printing
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mov bl, 0x0B
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mov esi, Reinit
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call write
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mov bl, 0x0F
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mov esi, CPUIDD
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call write
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mov bl, 0x0A
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mov esi, Pass
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call write
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mov bl, 0x0F
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mov esi, EnA20
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call write
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mov bl, 0x0A
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mov esi, Pass
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call write
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mov bl, 0x0A
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mov bl, 0x0A
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mov esi, txt
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mov esi, txt
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call write
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call write
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mov bl, 0x0B
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mov esi, msg
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call write
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mov bl, 0x0C
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mov esi, msg
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call write
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mov bl, 0x0D
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mov bl, 0x0D
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mov esi, msg
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mov esi, msg
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call write
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call write
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mov bl, 0x0E
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jmp Die
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mov esi, msg
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call write
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;call KERNEL
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jmp $
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[BITS 16]
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[BITS 16]
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ErrorNo64:
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ErrorNo64:
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@ -368,6 +416,4 @@ Die:
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cli
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cli
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hlt ; die nooooow
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hlt ; die nooooow
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retf
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retf
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times 1024-($-$$) db 144
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KERNEL:
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KERNEL:
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;=----------------------------------------------------------------------------=;
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; GNU GPL OS/K ;
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; ;
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; Authors: spectral` ;
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; NeoX ;
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; ;
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; Desc: Functions for the OS/K mbr ;
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; (x86_64 architecture only) ;
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;=----------------------------------------------------------------------------=;
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451
src/boot/mbr.s
451
src/boot/mbr.s
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@ -4,185 +4,338 @@
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; Authors: spectral` ;
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; Authors: spectral` ;
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; NeoX ;
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; NeoX ;
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; ;
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; ;
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; Desc: Master Boot Record for OS/K ;
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; Desc: Bootsector for OS/K ;
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; (x86_64 architecture only) ;
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; (x86_64 architecture only) ;
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;=----------------------------------------------------------------------------=;
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;=----------------------------------------------------------------------------=;
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%define SECOND_STAGE 0x100 ;about to change
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;; BOOT "SEGMENT"
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%define BOOT_SEG 0x07c0 ; (BOOT_SEG << 4) + BOOT_OFF = 0x007c00
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%define BOOT_OFF 0x0000
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;; STACK "SEGMENT"
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%define STACK_SEG 0x0600 ; (STACK_SEG << 4) + STACK_OFF = 0x007000
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%define STACK_OFF 0x1000
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[BITS 16] ; real mode
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;; DISK BUFFER "SEGMENT"
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[ORG 0x7C00] ; address where the BIOS/UEFI CSM is loading us
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%define BUFFER_SEG 0x2000 ; (BUFFER_SEG << 4) + BUFFER_OFF = 0x020000
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%define BUFFER_OFF 0x0000
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jmp short Start
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;; SECOND STAGE LOADER "SEGMENT"
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%define LOAD_SEG 0x0000 ; (LOAD_SEG << 4) + LOAD_OFF = 0x030000
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%define LOAD_OFF 0x1000
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;; File Allocation Table Disk Identifiers
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[BITS 16] ; Ensure 16-bit code (because fuck UEFI)
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nop
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OEM_ID db "GPL OS/K"
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BytesPerSector dw 0x0200
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SectorsPerCluster db 0x08
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ReservedSectors dw 0x0020
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TotalFATs db 0x02
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MaxRootEntries dw 0x0000
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NumberOfSectors dw 0x0000
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MediaDescriptor db 0xF8
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SectorsPerFAT dw 0x0000
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SectorsPerTrack dw 0x003D
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SectorsPerHead dw 0x0002
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HiddenSectors dd 0x00000000
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TotalSectors dd 0x00FE3B1F
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BigSectorsPerFAT dd 0x00000778
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Flags dw 0x0000
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FSVersion dw 0x0000
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RootDirectoryStart dd 0x00000002
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FSInfoSector dw 0x0001
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BackupBootSector dw 0x0006
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TIMES 12 DB 0 ; going to the next offset
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;---------------------------------------------------
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; Disk description table
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;---------------------------------------------------
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Intro:
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DriveNumber db 0x00
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jmp short _start ; Jump over the BIOS PARAMETER BLOCK
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ReservedByte db 0x00
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nop ; Required by BIOS to recognize the Disk
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Signature db 0x29
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BPB:
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VolumeID dd 0xFFFFFFFF
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%define OEMName bp+0x03 ; Disk label
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VolumeLabel db "OS/K BDISK "
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%define bytesPerSector bp+0x0b ; Bytes per sector
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SystemID db "FAT32 "
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%define sectorsPerCluster bp+0x0d ; Sectors per cluster
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%define reservedSectors bp+0x0e ; Reserved sectors
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%define fats bp+0x10 ; Number of fats
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%define rootDirEntries bp+0x11 ; Number of entries in root dir
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%define sectors bp+0x13 ; Logical sectors
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%define mediaType bp+0x15 ; Media descriptor byte
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%define fatSectors bp+0x16 ; Sectors per FAT
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%define sectorsPerTrack bp+0x18 ; Sectors per track
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%define heads bp+0x1a ; Number of sides/heads
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%define hiddenSectors bp+0x1c ; Hidden sectors
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%define hugeSectors bp+0x20 ; LBA sectors
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%define biosBootdrvNum bp+0x24 ; Bootdrv number
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%define reserved bp+0x25 ; This is not used
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%define bootSignature bp+0x26 ; Bootdrv signature
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%define volumeId bp+0x27 ; Volume ID
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%define volumeLabel bp+0x2b ; Volume Label
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%define fatTypeLabel bp+0x36 ; File system type
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times 0x3b db 0x00
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Start:
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;; ENTRY POINT
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;; saving registers for future
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_start:
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pushad
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jmp BOOT_SEG:$+5 ; Fix the cs:ip registers with a vaudou magical trip
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pushfd
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pushf
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;; dl contains the boot drive. Saving it.
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bootstrap:
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mov [Bootdrv], dl
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mov ax, BOOT_SEG ; Set segments to the location of the bootloader
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mov ds, ax
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;; hello world
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push si
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mov si, Starting
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call PrintB
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;; SWITCHING TO LOADER
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mov si, Switch
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call PrintB
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pop si
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mov cx, word [SectorsPerCluster] ; size of a cluster in sectors is stored in cx
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; computing location of the begining of the Data area and store in ax
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mov al, byte [TotalFATs] ; Total number of FATs
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mul word [BigSectorsPerFAT] ; Number of sectors for a FAT
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add ax, word [ReservedSectors] ; Find the start of the Data area
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mov word [Datasector], ax ; Store the begining of the Data area
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; reading 1st data cluster into memory (7C00:0200)
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mov ax, word [RootDirectoryStart]
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call ClusterLBA
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mov bx, 0x0200 ; copy 1st data cluter above bootcode
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call ReadSectors
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; Point Index register to 1st File Entry
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mov di, 0x0200 + 0x20
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;Point to the offset where the file location information contains
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mov dx, word [di + 0x001A]
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mov word [Cluster], dx
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;Set up the segments where the loader needs to be loaded ;)
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mov ax, 0100h ; set ES:BX = 0100:0000
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mov es, ax
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mov es, ax
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xor bx, bx
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;Read the cluster which contains the loader
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;; INIT STACK
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mov cx, 0x0008
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cli
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mov ax, word [Cluster]
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mov ax, STACK_SEG ; Init the staaaaaack
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call ClusterLBA
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mov ss, ax ; Continue init the staaaaaaaack
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call ReadSectors
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mov sp, STACK_OFF ; Ok man, the stack is in 4K :O
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sti
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mov bp, (0x7c0-STACK_SEG) << 4 ; Correct bp for the disk description table !
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;Jump to the location where the loader was loded
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;; INITIALIZE BOOT DISK
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popf
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or dl, dl ; Verifying dl points actually to the boot drive
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popfd
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jz loadRoot
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popad
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mov byte [Bootdrv], dl ; Another soul (the disk) saved !
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push word [Bootdrv]
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mov ah, 0x08
|
||||||
call dword SECOND_STAGE:0000
|
int 0x13 ; int 0x13 : read drive parameters/geom
|
||||||
|
jc loadRoot
|
||||||
|
and cx, 0x003f ; Maximum sector number is the high bits 6-7 of cl
|
||||||
|
mov word [sectorsPerTrack], cx ; And whose low 8 bits are in ch
|
||||||
|
mov dl, dh ; Convert the maximum head number to a word with another vaudou magical trip
|
||||||
|
xor dh, dh
|
||||||
|
inc dx ; because head numbers start at zero
|
||||||
|
mov word [heads], dx ; Another soul (the heads number) saved !
|
||||||
|
|
||||||
; Exiting
|
|
||||||
mov ah, 0x00
|
|
||||||
int 0x19 ; warm boot computer
|
|
||||||
|
|
||||||
;;END OF MBR
|
;; LOAD THE ROOT DIRECTORY FROM DISK
|
||||||
|
loadRoot:
|
||||||
|
xor cx, cx
|
||||||
|
mov ax, 32 ; Size of root dir = (rootDirEntries * 32) / bytesPerSector
|
||||||
|
mul word [rootDirEntries] ; multiply by the total size of the root directory
|
||||||
|
div word [bytesPerSector] ; divide by the number of bytes used per sector
|
||||||
|
xchg cx, ax
|
||||||
|
|
||||||
;;----------------------------------------------------------------------------;;
|
mov al, byte [fats] ; Location of root dir = (fats * fatSectors) + reservedSectors
|
||||||
;; DATA
|
mul word [fatSectors] ; multiply by the sectors used
|
||||||
Starting db 0x0A, 0x0D, 0x07, "GNU GPL OS/K", 0x0A, 0x0D, 0x0A, 0x0D, 0
|
add ax, word [reservedSectors] ; increase ax by the reserved sectors
|
||||||
Switch db 0x09, " Loading Second Stage", 0
|
mov word [userData], ax ; Start of user data = startOfRoot + numberOfRoot
|
||||||
AbsoluteSector db 0x00
|
add word [userData], cx ; Add the size and location of the root directory
|
||||||
AbsoluteHead db 0x00
|
|
||||||
AbsoluteTrack db 0x00
|
|
||||||
Cluster dw 0x0000
|
|
||||||
Datasector dw 0x0000
|
|
||||||
|
|
||||||
Bootdrv db 0x00
|
mov di, BUFFER_SEG ; Set the extra segment to the disk buffer
|
||||||
|
mov es, di
|
||||||
|
mov di, BUFFER_OFF ; Set es:di and load the root directory into the disk buffer
|
||||||
|
call readSectors ; Read the sectoooooooors !
|
||||||
|
|
||||||
;; INCLUDES
|
;; FIND THE SECOND STAGE LOADER
|
||||||
%include "boot/common.inc" ; for PrintB
|
mov di, BUFFER_OFF ; Set es:di to the disk buffer
|
||||||
|
mov cx, word [rootDirEntries] ; Search through all of the root dir entries
|
||||||
|
xor ax, ax ; Clear ax for the file entry offset
|
||||||
|
searchRoot:
|
||||||
|
xchg cx, dx ; Save cx because it's a loop counter
|
||||||
|
mov si, filename ; Load the filename
|
||||||
|
mov cx, 11 ; Compare first 11 bytes
|
||||||
|
rep cmpsb ; Compare si and di cx times
|
||||||
|
je loadFat ; We found the LOADEEEEEEEER!!!
|
||||||
|
add ax, 32 ; File entry offset
|
||||||
|
mov di, BUFFER_OFF ; Point back to the start of the entry
|
||||||
|
add di, ax ; Add the offset to point to the next entry
|
||||||
|
xchg dx, cx
|
||||||
|
loop searchRoot ; Continue to search for the file
|
||||||
|
|
||||||
;; INTERNAL FUNCTIONS
|
;; ERROR...
|
||||||
;-------------------------------------------------------------------;
|
mov si, fileNotFound ; Could not find the file
|
||||||
; loading second stage loader (loader.s) ;
|
call print
|
||||||
;-------------------------------------------------------------------;
|
|
||||||
ReadSectors:
|
;; REBOOT
|
||||||
.main:
|
reboot:
|
||||||
mov di, 0x0005 ; five retries for error
|
xor ax, ax
|
||||||
.sectorloop:
|
int 0x16 ; Get a single keypress
|
||||||
|
mov ah, 0x0e ; Teletype output
|
||||||
|
mov al, 0x0d ; Carriage return
|
||||||
|
int 0x10 ; Video interupt
|
||||||
|
mov al, 0x0a ; Line feed
|
||||||
|
int 0x10 ; Video interupt
|
||||||
|
mov al, 0x0a ; Line feed
|
||||||
|
int 0x10 ; Video interupt
|
||||||
|
xor ax, ax
|
||||||
|
int 0x19 ; Reboot the system
|
||||||
|
|
||||||
|
;; LOAD THE FAT FROM THE FILE
|
||||||
|
loadFat:
|
||||||
|
mov ax, word [es:di + 15] ; Get the file cluster at offset 26
|
||||||
|
push ax ; Store the FAT cluster
|
||||||
|
xor ax, ax ; Size of fat = (fats * fatSectors)
|
||||||
|
mov al, byte [fats] ; Move number of fats into al
|
||||||
|
mul word [fatSectors] ; Move fat sectors into bx
|
||||||
|
mov cx, ax ; Store in cx
|
||||||
|
mov ax, word [reservedSectors] ; Convert the first fat on the disk
|
||||||
|
mov di, BUFFER_OFF ; Set es:di and load the fat sectors into the disk buffer
|
||||||
|
call readSectors ; Read the sectooooooooooors !!!
|
||||||
|
|
||||||
|
;; LOAD THE CLUSTERS OF THE LOADER AND JUMP
|
||||||
|
loadFile:
|
||||||
|
mov di, LOAD_SEG
|
||||||
|
mov es, di ; Set es:bx to where the file will load
|
||||||
|
mov di, LOAD_OFF
|
||||||
|
pop ax ; File cluster restored
|
||||||
|
call readClusters ; Read clusters from the file
|
||||||
|
mov dl, byte [Bootdrv] ; Pass the boot Bootdrv into dl
|
||||||
|
jmp LOAD_SEG:LOAD_OFF ; Jump to the file loaded!
|
||||||
|
|
||||||
|
hlt ; This should never be hit...
|
||||||
|
; ...
|
||||||
|
; ...
|
||||||
|
; I hope....
|
||||||
|
; ...
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
;---------------------------------------------------;
|
||||||
|
; FUNCTIONS ;
|
||||||
|
;---------------------------------------------------;
|
||||||
|
|
||||||
|
readClusters:
|
||||||
|
;---------------------------------------------------;
|
||||||
|
; Read file clusters, starting at the given cluster,;
|
||||||
|
; expects FAT to be loaded into the disk buffer. ;
|
||||||
|
; Please note that this may allocate up to 128KB ;
|
||||||
|
; of ram. ;
|
||||||
|
; ;
|
||||||
|
; Expects: AX = Starting cluster ;
|
||||||
|
; ES:DI = Location to load clusters ;
|
||||||
|
; ;
|
||||||
|
; Returns: None ;
|
||||||
|
; ;
|
||||||
|
;---------------------------------------------------;
|
||||||
push ax
|
push ax
|
||||||
push bx
|
push bx
|
||||||
push cx
|
push cx
|
||||||
call LbaToChs
|
push dx
|
||||||
mov ah, 0x02 ; BIOS read sector
|
push di
|
||||||
mov al, 0x01 ; read one sector
|
push es
|
||||||
mov ch, BYTE [AbsoluteTrack] ; track
|
.clusterLoop:
|
||||||
mov cl, BYTE [AbsoluteSector] ; sector
|
xor bh, bh
|
||||||
mov dh, BYTE [AbsoluteHead] ; head
|
xor dx, dx
|
||||||
int 0x13 ; invoke BIOS
|
push ax ; Get the cluster start = (cluster - 2) * sectorsPerCluster + userData
|
||||||
jnc .success ; test for read error
|
sub ax, 2 ; Subtract 2
|
||||||
xor ax, ax ; BIOS reset disk
|
mov bl, byte [sectorsPerCluster] ; Sectors per cluster is a byte value
|
||||||
int 0x13 ; invoke BIOS
|
mul bx ; multiply (cluster - 2) * sectorsPerCluster
|
||||||
dec di ; decrement error counter
|
add ax, word [userData] ; add the userData
|
||||||
|
xor ch, ch
|
||||||
|
mov cl, byte [sectorsPerCluster] ; Sectors to read
|
||||||
|
call readSectors ; Read the sectors
|
||||||
|
pop ax ; Current cluster number
|
||||||
|
xor dx, dx
|
||||||
|
.calculateNextSector16: ; Get the next sector for FAT16 (cluster * 2)
|
||||||
|
mov bx, 2 ; Multiply the cluster by two (cluster is in ax)
|
||||||
|
mul bx
|
||||||
|
.loadNextSector:
|
||||||
|
push ds
|
||||||
|
push si
|
||||||
|
mov si, BUFFER_SEG
|
||||||
|
mov ds, si ; Temporarly set ds:si to the FAT buffer
|
||||||
|
mov si, BUFFER_OFF
|
||||||
|
add si, ax ; Point to the next cluster in the FAT entry
|
||||||
|
mov ax, word [ds:si] ; Load ax to the next cluster in FAT
|
||||||
|
pop si
|
||||||
|
pop ds
|
||||||
|
.nextSectorCalculated:
|
||||||
|
cmp ax, 0xfff8 ; Check if we are at the end of the file?
|
||||||
|
jae .done
|
||||||
|
add di, 512 ; Add to the pointer offset
|
||||||
|
jnc .clusterLoop
|
||||||
|
.fixBuffer: ; An error will occur if the buffer in memory
|
||||||
|
mov dx, es ; overlaps a 64k page boundry, when di overflows
|
||||||
|
add dh, 0x10 ; it will trigger the carry flag, so correct
|
||||||
|
mov es, dx ; extra segment by 0x1000
|
||||||
|
jmp .clusterLoop ; Load the next file cluster
|
||||||
|
.done:
|
||||||
|
pop es
|
||||||
|
pop di
|
||||||
|
pop dx
|
||||||
pop cx
|
pop cx
|
||||||
pop bx
|
pop bx
|
||||||
pop ax
|
pop ax
|
||||||
jnz .sectorloop ; attempt to read again
|
ret
|
||||||
int 0x18
|
|
||||||
.success:
|
|
||||||
|
readSectors:
|
||||||
|
;---------------------------------------------------;
|
||||||
|
; Read sectors starting at a given sector by ;
|
||||||
|
; the given times and load into a buffer. Please ;
|
||||||
|
; note that this may allocate up to 128KB of ram. ;
|
||||||
|
; ;
|
||||||
|
; Expects: AX = Starting sector ;
|
||||||
|
; CX = Number of sectors to read ;
|
||||||
|
; ES:DI = Location to load sectors ;
|
||||||
|
; ;
|
||||||
|
; Returns: None ;
|
||||||
|
; ;
|
||||||
|
;---------------------------------------------------;
|
||||||
|
push ax
|
||||||
|
push bx
|
||||||
|
push cx
|
||||||
|
push dx
|
||||||
|
push di
|
||||||
|
push es
|
||||||
|
mov bx, di ; Convert es:di to es:bx for int 13h
|
||||||
|
.sectorLoop:
|
||||||
|
push ax
|
||||||
|
push cx
|
||||||
|
xor dx, dx
|
||||||
|
div word [sectorsPerTrack] ; Divide the lba (value in ax) by sectorsPerTrack
|
||||||
|
mov cx, dx ; Save the absolute sector value
|
||||||
|
inc cx
|
||||||
|
xor dx, dx ; Divide by the number of heads
|
||||||
|
div word [heads] ; to get absolute head and track values
|
||||||
|
mov dh, dl ; Move the absolute head into dh
|
||||||
|
mov ch, al ; Low 8 bits of absolute track
|
||||||
|
shl ah, 1 ; High 2 bits of absolute track
|
||||||
|
shl ah, 1
|
||||||
|
shl ah, 1
|
||||||
|
shl ah, 1
|
||||||
|
shl ah, 1
|
||||||
|
shl ah, 1
|
||||||
|
or cl, ah ; Now cx is set with respective track and sector numbers
|
||||||
|
mov dl, byte [Bootdrv] ; Set correct Bootdrv for int 13h
|
||||||
|
mov di, 5 ; Try five times to read the sector because i love 5
|
||||||
|
.attemptRead:
|
||||||
|
mov ax, 0x0201 ; Read Sectors func of int 13h, read one sector
|
||||||
|
int 0x13 ; Call int 13h (BIOS disk I/O)
|
||||||
|
jnc .readOk ; If no carry set, the sector has been read
|
||||||
|
xor ah, ah ; Reset Bootdrv func of int 13h
|
||||||
|
int 0x13 ; Call int 13h (BIOS disk I/O)
|
||||||
|
dec di ; Decrease read attempt counter
|
||||||
|
jnz .attemptRead ; Try to read the sector again
|
||||||
|
mov si, diskError ; Error reading the disk :/
|
||||||
|
call print
|
||||||
|
jmp reboot
|
||||||
|
.readOk:
|
||||||
|
pop cx
|
||||||
|
pop ax
|
||||||
|
inc ax ; Increase the next sector to read
|
||||||
|
add bx, word [bytesPerSector] ; Add to the buffer address for the next sector
|
||||||
|
jnc .nextSector
|
||||||
|
.fixBuffer: ; An error will occur if the buffer in memory
|
||||||
|
mov dx, es ; overlaps a 64k page boundry, when bx overflows
|
||||||
|
add dh, 0x10 ; it will trigger the carry flag, so correct
|
||||||
|
mov es, dx ; es segment by 0x1000
|
||||||
|
.nextSector:
|
||||||
|
loop .sectorLoop
|
||||||
|
pop es
|
||||||
|
pop di
|
||||||
|
pop dx
|
||||||
pop cx
|
pop cx
|
||||||
pop bx
|
pop bx
|
||||||
pop ax
|
pop ax
|
||||||
add bx, WORD [BytesPerSector] ; queue next buffer
|
|
||||||
inc ax ; queue next sector
|
|
||||||
loop .main ; read next sector
|
|
||||||
ret
|
ret
|
||||||
|
|
||||||
;-------------------------------------------------------------------;
|
print:
|
||||||
; Converts LBA Adresses to CHS ;
|
;---------------------------------------------------;
|
||||||
;-------------------------------------------------------------------;
|
; Print out a simple string. ;
|
||||||
LbaToChs:
|
; ;
|
||||||
xor dx, dx ; prepare dx:ax for operation
|
; Expects: DS:SI = String to print ;
|
||||||
div WORD [SectorsPerTrack] ; calculate
|
; ;
|
||||||
inc dl ; adjust for sector 0
|
; Returns: None ;
|
||||||
mov BYTE [AbsoluteSector], dl
|
; ;
|
||||||
xor dx, dx ; prepare dx:ax for operation
|
;---------------------------------------------------;
|
||||||
div WORD [SectorsPerHead] ; calculate
|
lodsb ; Load byte from ds:si to al
|
||||||
mov BYTE [AbsoluteHead], dl
|
or al, al ; If al is empty stop looping
|
||||||
mov BYTE [AbsoluteTrack], al
|
jz .done ; Done looping and return
|
||||||
ret
|
mov ah, 0x0e ; Teletype output
|
||||||
;-------------------------------------------------------------------;
|
int 0x10 ; Video interupt
|
||||||
; Converts FAT Adresses to LBA ;
|
jmp print ; Loop untill string is null
|
||||||
;-------------------------------------------------------------------;
|
.done:
|
||||||
ClusterLBA:
|
|
||||||
sub ax, 0x0002 ; zero base cluster number
|
|
||||||
xor cx, cx
|
|
||||||
mov cl, BYTE [SectorsPerCluster] ; convert byte to word
|
|
||||||
mul cx
|
|
||||||
add ax, WORD [Datasector] ; base data sector
|
|
||||||
ret
|
ret
|
||||||
|
|
||||||
End:
|
;; LOVELY DATA
|
||||||
times 510-($-$$) db 144 ; NOP until 510
|
fileNotFound db "FStage ERR : NO LOADER", 0 ; File was not found
|
||||||
dw 0xAA55 ; magic word
|
diskError db "FStage ERR : DISK", 0 ; Error while reading from the disk
|
||||||
|
userData dw 0 ; Start of the data sectors
|
||||||
|
Bootdrv db 0 ; Boot Bootdrv number
|
||||||
|
filename db "LOADER BIN" ; Filename
|
||||||
|
|
||||||
|
;; END
|
||||||
|
times 510 - ($ - $$) db 0 ; Pad remainder of boot sector with zeros
|
||||||
|
dw 0xaa55 ; Boot signature
|
||||||
|
|
||||||
|
|
|
||||||
Loading…
Reference in New Issue