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[MBR] Successfully jump to protected mode

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[MBR} Successfully set VGA video mode 3
[Host/KernelCopy] Fix MBR_PACKET definition and buffer address
[RawIMG] Fix linux iamge generation script
[Host/GDTCreator] Fix low limit values
This commit is contained in:
John 2023-01-14 02:15:53 +01:00
parent d57078cc2d
commit 3f7e02533f
Signed by: jstefanelli
GPG key ID: 60EDE2437640D2AA
6 changed files with 65 additions and 84 deletions
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10
host/gdtCreator/gdtCreator.cpp
View file

@ -4,7 +4,7 @@
#include <iostream>
uint64_t makeEntry(uint32_t base, uint16_t limit, bool present, unsigned char dpl, bool executable, bool exec_write) {
uint64_t makeEntry(uint32_t base, uint32_t limit, bool present, unsigned char dpl, bool executable, bool exec_write) {
uint64_t value = 0x0;
//auto* target = (uint8_t*) &value;
@ -43,9 +43,9 @@ uint64_t makeEntry(uint32_t base, uint16_t limit, bool present, unsigned char dp
}
int main(int argc, char** argv) {
std::cout << std::hex << "Code: " << makeEntry(0, 0xFFFF, true, 0x0, true, true) << std::endl;
std::cout << std::hex << "Data: " << makeEntry(0, 0xFFFF, true, 0x0, false, true) << std::endl;
std::cout << std::hex << "User Code: " << makeEntry(0, 0xFFFF, true, 0x3, true, true) << std::endl;
std::cout << std::hex << "User Data: " << makeEntry(0, 0xFFFF, true, 0x3, false, true) << std::endl;
std::cout << std::hex << "Code: " << makeEntry(0, 0xFFFFF, true, 0x0, true, true) << std::endl;
std::cout << std::hex << "Data: " << makeEntry(0, 0xFFFFF, true, 0x0, false, true) << std::endl;
std::cout << std::hex << "User Code: " << makeEntry(0, 0xFFFFF, true, 0x3, true, true) << std::endl;
std::cout << std::hex << "User Data: " << makeEntry(0, 0xFFFFF, true, 0x3, false, true) << std::endl;
return 0;
}

28
host/kernelcopy/kernelcopy.c
View file

@ -27,6 +27,7 @@ typedef struct _MBR_ReadPacket {
os_u16 blocks;
os_u16 buffer_offset;
os_u16 buffer_segment;
//os_u32 buffer;
os_u64 lba;
os_u16 sig_1;
} OS_PACK_MID MBR_ReadPacket;
@ -136,35 +137,18 @@ int main(int argc, char** argv) {
char mbr[512];
fread(mbr, 1, 512, image);
os_bool found = OS_FALSE;
os_s8* ptr = mbr;
for(int i = 0; i < 512 - sizeof(MBR_BuildSettings); i++) {
MBR_BuildSettings* settings = (MBR_BuildSettings*)ptr;
if (settings->sig_0 == MBR_SETTINGS_SIG_0 && settings->sig_1 == MBR_SETTINGS_SIG_1) {
settings->sector = kernel_offset / fat.header.base.bytes_per_sector;
settings->size = kernel_size;
found = OS_TRUE;
break;
}
ptr++;
}
printf("Kernel size: %d", kernel_size);
if (found == OS_FALSE) {
fprintf(stderr, "Error: could not find BUILD_SETTINGS markers\n");
return 1;
}
found = OS_FALSE;
ptr = mbr;
os_bool found = OS_FALSE;
os_u8* ptr = mbr;
for (int i = 0; i < 512 - sizeof(MBR_ReadPacket); i++) {
MBR_ReadPacket * packet = (MBR_ReadPacket*)ptr;
if(packet->sig_0 == MBR_PACKET_SIG_0 && packet->sig_1 == MBR_PACKET_SIG_1) {
packet->lba = kernel_offset / fat.header.base.bytes_per_sector;
packet->blocks = (kernel_size / fat.header.base.bytes_per_sector) + ((kernel_size % fat.header.base.bytes_per_sector) == 0 ? 0 : 1);
packet->buffer_offset = 0x0000;
packet->buffer_segment = 0x0100;
packet->buffer_segment = 0x1000;
//packet->buffer = 0x10000;
found = OS_TRUE;
break;
}

4
mbr/linker.ld
View file

@ -11,8 +11,8 @@ SECTIONS
.sig : AT(0x7DFE){
SHORT(0xaa55);
}
. = 0x7E00;
.eh_frame : AT(0x7E00){
. = 0x9C00;
.eh_frame : AT(0x9C00){
*.o(.eh_frame);
}
}

95
mbr/mbr.asm
View file

@ -15,7 +15,7 @@ fat_header:
; function READ_SECTORS_EXTENDED: Read sectors from disk
; Uses INT 13h AH=42h from: http://www.ctyme.com/intr/rb-0708.htm
; Stack Parameters (in order of PUSH):
; - BYTE: Drive number
; - WORD: Drive number (interpret as BYTE)
; - WORD: Address of packet
; - WORD: RETURN ADDRESS
; Returns:
@ -34,7 +34,8 @@ read_sectors_extended:
PUSH BP ; save BP
MOV BP, SP ; estabilish stack frame
MOV DX, 0 ; zero-out DX
MOV DL, [BP + 10] ; load drive number
MOV DX, [BP + 10] ; load drive number
MOV DH, 0 ; Zero-out high byte of drive number
MOV SI, [BP + 8] ; load address of packet
MOV AH, 42h ; set AH to 42h
MOV AL, 0h ; set AL to 0h
@ -186,35 +187,23 @@ entry:
; Not doing this may cause an interrupt to use an old SP and new SS
MOV DS, AX ; set up segment registers
MOV ES, AX ; ^^^
MOV FS, AX ; ^^^
MOV GS, AX ; ^^^
PUSH DX ; save drive number (DL)
; Load kernel image
MOV BX, packet_blocks ; Load address of packet_blocks
MOV AX, [BX] ; Load value of packet_blocks
CMP AX, 0 ; See if amount of packets to read is 0
JE endless_loop ; if no packets are to be loaded, the kernel is not present. Loop endlessly
POP AX ; load 'drive number'
PUSH AX ; pushing it twice to keep it saved, CBA to mess with SP, BP and stuff right now
PUSH AX ; push parameter 'drive number'
; Comment out check, presume that the packet info is populated
;MOV BX, packet_blocks ; Load address of packet_blocks
;MOV AX, [BX] ; Load value of packet_blocks
;CMP AX, 0 ; See if amount of packets to read is 0
;JE endless_loop ; if no packets are to be loaded, the kernel is not present. Loop endlessly
; Parameter drive number is already in the stack
MOV AX, read_sectors_packet ; load 'packet address'
PUSH AX ; push parameter 'packet address'
CALL read_sectors_extended ; try to read these damned sectors
ADD SP, 4 ; clear previous call parameters
; Print message
MOV AX, msg ; load address of msg
PUSH AX ; push parameter 'address of string'
MOV AX, 14 ; load size of msg
PUSH AX ; push parameter 'size of string'
CALL print ; call function 'print'
ADD SP, 4 ; clear previous call parameters
; Enable A20
CALL check_a20 ; call check_a20. Result in Ax
CMP AX, 0 ; compare AX to 0 (0 = A20 disabled)
@ -231,28 +220,44 @@ entry:
MOV AX, 8 ; load size of 'a20_msg'
PUSH AX ; push parameter 'size of string'
CALL print ; print 'a20_msg'
JMP endless_loop ; loop endlessly
after_a20:
; set video mode
STI ; re-enable interrupts
MOV AH, 00h ; int 10h AH=00h = set video mode command
MOV AL, 03h ; desired video mode (80x25 characters, 8 colors)
INT 10h ; call interrupt
after_video:
; load GDT
CLI ; disable interrupts
MOV AX, gdt ; load address of GDT
MOV [gdt_ptr_base], AX ; save address of GDT to gdt_ptr_base
LGDT [gdt_ptr_base] ; load GDT
; print message
MOV AX, gdt_msg ; load address of 'gdt_ms'
PUSH AX ; push parameter 'address of string'
MOV AX, 8 ; load size of 'gdt_msg'
PUSH AX ; push parameter 'size of string'
CALL print ; print 'gdt_msg'
JMP endless_loop ; loop endlessly
LGDT [gdt_ptr] ; load GDT
; Enable protected mode
MOV EAX, CR0 ; load Control Register 0
OR AL, 1 ; set Protection Enable bit
MOV CR0, EAX ; save Control Register 0
JMP 08h:init_32 ; long jump to 32 bit mode
init_32:
USE32
MOV AX, 10h ; load 32 bit segment registers
MOV AX, 10h
MOV DS, AX ; ^^^^
MOV SS, AX ; ^^^^
MOV FS, AX ; ^^^^
MOV GS, AX ; ^^^^
MOV SS, AX ; ^^^^
MOV EAX, 0x7CFE ; reset stack
MOV ESP, EAX ; ^^^^
JMP 0x10000 ; jump to stage1 bootloader
USE16
endless_loop:
JMP endless_loop ; loop endlessly
@ -268,23 +273,15 @@ packet_buffer_seg dw 0h
packet_lba dq 0h
packet_sig_1 dw 0x4955
build_settings:
build_settings_magic_0 dw 0x4952
build_settings_offset dw 0x0
build_settings_size dw 0x0
build_settings_magic_1 dw 0x4953
msg db "OS3_KRNL_OK!", 10, 13
a20_msg db "NO_A20", 10, 13
gdt_msg db "GDT_OK", 10, 13
gdt:
null_sec dq 0x0
kernel_code dq 0xc09a000000ffff
kernel_data dq 0xc092000000ffff
user_code dq 0xc0fa000000ffff
user_data dq 0xc0f2000000ffff
kernel_code dq 0xcf9a000000ffff
kernel_data dq 0xcf92000000ffff
user_code dq 0xcffa000000ffff
user_data dq 0xcff2000000ffff
gdt_ptr:
gdt_ptr_limit dw 40
gdt_ptr_base dd 0
gdt_ptr_base dd gdt

4
rawimg/mkimg_linux.sh
View file

@ -1,4 +1,4 @@
#!/bin/bash
echo "Generating image $1..."
qemu-img create $1 512M
mkfs.vfat $1 -n OS3_BOOT
qemu-img create "$1" "512M"
mkfs.vfat "$1" -n OS3_BOOT

8
stage1/linker.ld
View file

@ -3,15 +3,15 @@ SECTIONS
{
. = 0x10000;
.text : AT(0x10000){
*.o(.text);
*(.text);
}
.data : {
*.o(.data);
*(.data);
}
.rodata : {
*.o(.rodata);
*(.rodata);
}
.bss : {
*.o(.bss);
*(.bss);
}
}