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Load the kernel

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This commit is contained in:
Baptiste Wicht 2014-01-01 20:52:23 +01:00
parent 60d159af6f
commit 2892baa993
3 changed files with 106 additions and 7 deletions
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1
Makefile
View File

@ -15,6 +15,7 @@ thor.flp: bootloader/stage1.bin bootloader/stage2.bin kernel/kernel.bin
dd if=bootloader/stage1.bin of=hdd.img conv=notrunc
dd if=bootloader/stage2.bin of=hdd.img seek=1 conv=notrunc
sudo /sbin/losetup -o1048576 /dev/loop0 hdd.img
sudo mkdosfs -F32 /dev/loop0
sudo /bin/mount -t vfat /dev/loop0 /mnt/fake_cdrom/
sudo /bin/cp kernel/kernel.bin /mnt/fake_cdrom/
sleep 0.1

104
bootloader/stage2.asm
View File

@ -12,7 +12,7 @@ jmp second_step
%include "intel_16.asm"
%include "sectors.asm"
KERNEL_BASE equ 0x100 ; 0x100:0x0 = 0x1000
KERNEL_BASE equ 0x200 ; 0x200:0x0 = 0x2000
DAP:
.size db 0x10
@ -215,15 +215,109 @@ second_step:
jmp error_end
; TODO Find kernel.bin in the directory
.found:
mov si, kernel_found
call print_line_16
; 4. Load the kernel into memory
mov ax, [cluster_low]
mov [current_cluster], ax
mov word [current_segment], KERNEL_BASE
.next_cluster:
mov si, star
call print_16
mov ah, [sectors_per_cluster]
mov byte [DAP.count], ah
mov word [DAP.offset], 0x0
mov ax, [current_segment]
mov word [DAP.segment], ax
; Compute LBA from current_cluster
mov ax, [current_cluster]
sub ax, 2
movzx bx, byte [sectors_per_cluster]
mul bx
mov bx, [cluster_begin]
add ax, bx
mov word [DAP.lba], ax
mov ah, 0x42
mov si, DAP
mov dl, 0x80
int 0x13
jc read_failed
; Compute next cluster
; Compute the sector of the FAT to read
mov ax, [current_cluster]
shl ax, 2 ; current_cluster * 4
shr ax, 9 ; (current_cluster * 4) / 512
mov bx, [fat_begin]
add ax, bx ; fat_sector
; Read the FAT sector
mov byte [DAP.count], 1
mov word [DAP.offset], 0x100
mov word [DAP.segment], 0x0
mov word [DAP.lba], ax
mov ah, 0x42
mov si, DAP
mov dl, 0x80
int 0x13
jc read_failed
mov si, [current_cluster]
and si, 512 - 1 ; current_cluster % 512
shl si, 2
; cluster low
mov ax, [gs:(0x100 + si)]
; cluster high
mov bx, [gs:(0x100 + si + 2)]
cmp bx, 0x0FFF
jl .ok
cmp ax, 0xFFF7
je corrupted
cmp ax, 0xFFF8
jge .fully_loaded
.ok:
mov [current_cluster], ax
mov ax, sectors_per_cluster
mov bx, 0x20
mul bx
mov bx, [current_segment]
add ax, bx
mov [current_segment], ax
jmp .next_cluster
.fully_loaded:
mov si, kernel_loaded
call print_line_16
jmp $
corrupted:
mov si, corrupted_disk
call print_line_16
jmp error_end
read_failed:
mov si, read_failed_msg
call print_line_16
@ -251,12 +345,16 @@ error_end:
size_high dw 0
size_low dw 0
current_cluster dw 0
current_segment dw 0
; Constant Datas
load_kernel db 'Attempt to load the kernel...', 0
kernel_found db 'Kernel found. Starting kernel loading...', 0
kernel_not_found db 'Kernel not found...', 0
kernel_loaded db 'Kernel fully loaded', 0
corrupted_disk db 'The disk seeems to be corrupted', 0
star db '*', 0
read_failed_msg db 'Read disk failed', 0

8
kernel/src/fat32.cpp
View File

@ -93,10 +93,10 @@ struct long_entry {
static_assert(sizeof(cluster_entry) == 32, "A cluster entry is 32 bytes");
static_assert(sizeof(long_entry) == 32, "A cluster entry is 32 bytes");
constexpr const bool CLUSTER_FREE = 0x0;
constexpr const bool CLUSTER_RESERVED= 0x1;
constexpr const bool CLUSTER_CORRUPTED = 0x0FFFFFF7;
constexpr const bool CLUSTER_END = 0x0FFFFFF8;
constexpr const uint32_t CLUSTER_FREE = 0x0;
constexpr const uint32_t CLUSTER_RESERVED= 0x1;
constexpr const uint32_t CLUSTER_CORRUPTED = 0x0FFFFFF7;
constexpr const uint32_t CLUSTER_END = 0x0FFFFFF8;
uint64_t cached_disk = -1;
uint64_t cached_partition = -1;