I'm done making my bootloader and kernel that switches from real-mode to protected-mode and Displays the character; 'S'. But when I boot it from Bochs, the last line of the my log is just: "Booting from 0000:7c00" and doesn't get past there. I edited and rewrote my code but still. I tried using QEmu to emulate but says: "boot device not found". I read through this Stack Overflow Question: "https://stackoverflow.com/questions/3285721/oss-boot-loader-doesnt-work" but that question has no answer and tried to read a couple OSDev Questions and Answers, but it didn't solve my problem here's the link: "https://forum.osdev.org/viewtopic.php?t=7877&p=46293", and some other links that I forgot. I tried other compilation options on gcc (about compiling down below.) and still doesn't work. I provided an disassembly for further analysis. and Thank you for taking a look at this Question!
Here's my code: (Filename "start_boot.asm")
[org 7c000h]
DRIVE_ID db 0
KERNEL_HEX equ 0x1000
mov bp, 9000h
mov sp, bp
mov bh, [_realmode]
call _print
call prep_kernel
call init_gdt
jmp $
%include "get_sector.asm"
%include "print_str.asm"
%include "print_str_pm.asm"
%include "gdt_conf.asm"
%include "init_protm.asm"
_realmode db "Bit mode: 16-bit", 0
_pmmode db "Bit mode: 32-bit", 0
_kernel_lod db "Kernel is loading... Please wait....", 0
[bits 16]
prep_kernel:
mov bh, _kernel_lod
call _print
mov ah, 02h
mov al, 15
mov ch, 0
mov cl, 1
mov dh, 0
mov dl, [DRIVE_ID]
mov bx, KERNEL_HEX
mov es, bx
call _read
ret
[bits 32]
launch_kernel:
mov ebx, _kernel_lod
call _print_pm
call KERNEL_HEX
jmp $
times 510 - ($ - $$) db 0
dw 0xAA55
Headers of "start_boot.asm": ("get_sector.asm")
_disk_err db "Media error occured! we'll restart.", 0
_read:
push dx
xor ah, ah
mov ah, 02h
mov dl, DRIVE_ID
mov ch, 00h
mov dh, 00h
mov al, dh
mov cl, 02h
int 13h
jc err
pop dx
cmp dh, al
jne err
ret
err:
mov bh, [_disk_err]
call _print
hlt
("print_str.asm")
[bits 16]
_print:
mov ah, 0Eh
mov al, bh
int 10h
("print_str_pm.asm")
[bits 32]
VIDEO_HEX equ 0xb8000
WHITE_BLACK equ 0Fh
_print_pm:
pusha
mov edx, VIDEO_HEX
print_pm_loop:
mov al, [ebx]
mov ah, WHITE_BLACK
cmp al, 0
je print_done
mov [edx], ax
add ebx, 1
add edx, 2
jmp print_pm_loop
print_done:
popa
ret
("gdt_conf.asm")
desc_start:
null_desc:
dd 0x0
dd 0x0
code_desc:
dw 0xFFFF
dw 0x0
db 0x0
db 10011010b
db 11001111b
db 0x0
data_desc:
dw 0xFFFF
dw 0x0
db 0x0
db 10010010b
db 11001111b
db 0x0
desc_end:
gdt_config_desc:
dw desc_end - desc_start - 1
dd desc_start
CODE_SEGM equ code_desc - desc_start
DATA_SEGM equ data_desc - desc_start
("init_protm.asm")
init_gdt:
cli
lgdt [gdt_config_desc]
mov eax, cr0
or eax, 0x1
mov cr0, eax
jmp CODE_SEGM:init_pm
[bits 32]
init_pm:
mov ax, DATA_SEGM
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000
mov esp, ebp
call launch_kernel
(and that's all)
I link this file to the kernel so that I can prevent the kernel from going back the boot sector if it encounters a ret instruction
("link.asm")
[bits 32]
[extern main]
call main
jmp $
("kernel.c")
void main(void)
{
char* VID_MEM = (char *) 0xB8000;
*VID_MEM = 'S';
}
And here's the Disassembly file of the compiled OS:
(it's long)
00000000 00BD009089EC add [ebp-0x13767000],bh
00000006 8A3E mov bh,[esi]
00000008 CB retf
00000009 C0E84D shr al,byte 0x4d
0000000C 00E8 add al,ch
0000000E 0201 add al,[ecx]
00000010 E88600EBFE call 0xfeeb009b
00000015 4D dec ebp
00000016 6564696120657272 imul esp,[fs:ecx+0x20],dword 0x6f727265
-6F
0000001F 7220 jc 0x41
00000021 6F outsd
00000022 636375 arpl [ebx+0x75],sp
00000025 7265 jc 0x8c
00000027 642120 and [fs:eax],esp
0000002A 7765 ja 0x91
0000002C 27 daa
0000002D 6C insb
0000002E 6C insb
0000002F 207265 and [edx+0x65],dh
00000032 7374 jnc 0xa8
00000034 61 popa
00000035 7274 jc 0xab
00000037 2E005230 add [cs:edx+0x30],dl
0000003B E4B4 in al,0xb4
0000003D 02B200B500B6 add dh,[edx-0x49ff4b00]
00000043 0088F0B102CD add [eax-0x32fd4e10],cl
00000049 137206 adc esi,[edx+0x6]
0000004C 5A pop edx
0000004D 38C6 cmp dh,al
0000004F 7501 jnz 0x52
00000051 C3 ret
00000052 8A3E mov bh,[esi]
00000054 15C0E80100 adc eax,0x1e8c0
00000059 F4 hlt
0000005A B40E mov ah,0xe
0000005C 88F8 mov al,bh
0000005E CD10 int 0x10
00000060 60 pusha
00000061 BA00800B00 mov edx,0xb8000
00000066 8A03 mov al,[ebx]
00000068 B40F mov ah,0xf
0000006A 3C00 cmp al,0x0
0000006C 740B jz 0x79
0000006E 668902 mov [edx],ax
00000071 83C301 add ebx,byte +0x1
00000074 83C202 add edx,byte +0x2
00000077 EBED jmp short 0x66
00000079 61 popa
0000007A C3 ret
0000007B 0000 add [eax],al
0000007D 0000 add [eax],al
0000007F 0000 add [eax],al
00000081 0000 add [eax],al
00000083 FF db 0xff
00000084 FF00 inc dword [eax]
00000086 0000 add [eax],al
00000088 9ACF00FFFF0000 call 0x0:0xffff00cf
0000008F 0092CF001700 add [edx+0x1700cf],dl
00000095 7BC0 jpo 0x57
00000097 07 pop es
00000098 00FA add dl,bh
0000009A 0F011593C00700 lgdt [dword 0x7c093]
000000A1 0F20C0 mov eax,cr0
000000A4 83C801 or eax,byte +0x1
000000A7 0F22C0 mov cr0,eax
000000AA EAB1C007000800 jmp 0x8:0x7c0b1
000000B1 66B81000 mov ax,0x10
000000B5 8ED8 mov ds,eax
000000B7 8ED0 mov ss,eax
000000B9 8EC0 mov es,eax
000000BB 8EE0 mov fs,eax
000000BD 8EE8 mov gs,eax
000000BF BD00000900 mov ebp,0x90000
000000C4 89EC mov esp,ebp
000000C6 E863000000 call 0x12e
000000CB 42 inc edx
000000CC 6974206D6F64653A imul esi,[eax+0x6d],dword 0x3a65646f
000000D4 2031 and [ecx],dh
000000D6 362D62697400 ss sub eax,0x746962
000000DC 42 inc edx
000000DD 6974206D6F64653A imul esi,[eax+0x6d],dword 0x3a65646f
000000E5 2033 and [ebx],dh
000000E7 322D62697400 xor ch,[dword 0x746962]
000000ED 4B dec ebx
000000EE 65726E gs jc 0x15f
000000F1 656C gs insb
000000F3 206973 and [ecx+0x73],ch
000000F6 206C6F61 and [edi+ebp*2+0x61],ch
000000FA 64696E672E2E2E20 imul ebp,[fs:esi+0x67],dword 0x202e2e2e
00000102 50 push eax
00000103 6C insb
00000104 6561 gs popa
00000106 7365 jnc 0x16d
00000108 207761 and [edi+0x61],dh
0000010B 69742E2E2E2E00B7 imul esi,[esi+ebp+0x2e],dword 0xb7002e2e
00000113 ED in eax,dx
00000114 E843FFB402 call 0x2b5005c
00000119 B00F mov al,0xf
0000011B B500 mov ch,0x0
0000011D B101 mov cl,0x1
0000011F B600 mov dh,0x0
00000121 8A16 mov dl,[esi]
00000123 00C0 add al,al
00000125 BB00108EC3 mov ebx,0xc38e1000
0000012A E80CFFC3BB call 0xbbc4003b
0000012F ED in eax,dx
00000130 C00700 rol byte [edi],byte 0x0
00000133 E828FFFFFF call 0x60
00000138 E8C34EF8FF call 0xfff85000
0000013D EBFE jmp short 0x13d
0000013F 0000 add [eax],al
00000141 0000 add [eax],al
00000143 0000 add [eax],al
00000145 0000 add [eax],al
00000147 0000 add [eax],al
00000149 0000 add [eax],al
0000014B 0000 add [eax],al
0000014D 0000 add [eax],al
0000014F 0000 add [eax],al
00000151 0000 add [eax],al
00000153 0000 add [eax],al
00000155 0000 add [eax],al
00000157 0000 add [eax],al
00000159 0000 add [eax],al
0000015B 0000 add [eax],al
0000015D 0000 add [eax],al
0000015F 0000 add [eax],al
00000161 0000 add [eax],al
00000163 0000 add [eax],al
00000165 0000 add [eax],al
00000167 0000 add [eax],al
00000169 0000 add [eax],al
0000016B 0000 add [eax],al
0000016D 0000 add [eax],al
0000016F 0000 add [eax],al
00000171 0000 add [eax],al
00000173 0000 add [eax],al
00000175 0000 add [eax],al
00000177 0000 add [eax],al
00000179 0000 add [eax],al
0000017B 0000 add [eax],al
0000017D 0000 add [eax],al
0000017F 0000 add [eax],al
00000181 0000 add [eax],al
00000183 0000 add [eax],al
00000185 0000 add [eax],al
00000187 0000 add [eax],al
00000189 0000 add [eax],al
0000018B 0000 add [eax],al
0000018D 0000 add [eax],al
0000018F 0000 add [eax],al
00000191 0000 add [eax],al
00000193 0000 add [eax],al
00000195 0000 add [eax],al
00000197 0000 add [eax],al
00000199 0000 add [eax],al
0000019B 0000 add [eax],al
0000019D 0000 add [eax],al
0000019F 0000 add [eax],al
000001A1 0000 add [eax],al
000001A3 0000 add [eax],al
000001A5 0000 add [eax],al
000001A7 0000 add [eax],al
000001A9 0000 add [eax],al
000001AB 0000 add [eax],al
000001AD 0000 add [eax],al
000001AF 0000 add [eax],al
000001B1 0000 add [eax],al
000001B3 0000 add [eax],al
000001B5 0000 add [eax],al
000001B7 0000 add [eax],al
000001B9 0000 add [eax],al
000001BB 0000 add [eax],al
000001BD 0000 add [eax],al
000001BF 0000 add [eax],al
000001C1 0000 add [eax],al
000001C3 0000 add [eax],al
000001C5 0000 add [eax],al
000001C7 0000 add [eax],al
000001C9 0000 add [eax],al
000001CB 0000 add [eax],al
000001CD 0000 add [eax],al
000001CF 0000 add [eax],al
000001D1 0000 add [eax],al
000001D3 0000 add [eax],al
000001D5 0000 add [eax],al
000001D7 0000 add [eax],al
000001D9 0000 add [eax],al
000001DB 0000 add [eax],al
000001DD 0000 add [eax],al
000001DF 0000 add [eax],al
000001E1 0000 add [eax],al
000001E3 0000 add [eax],al
000001E5 0000 add [eax],al
000001E7 0000 add [eax],al
000001E9 0000 add [eax],al
000001EB 0000 add [eax],al
000001ED 0000 add [eax],al
000001EF 0000 add [eax],al
000001F1 0000 add [eax],al
000001F3 0000 add [eax],al
000001F5 0000 add [eax],al
000001F7 0000 add [eax],al
000001F9 0000 add [eax],al
000001FB 0000 add [eax],al
000001FD 0055AA add [ebp-0x56],dl
00000200 E802000000 call 0x207
00000205 EBFE jmp short 0x205
00000207 55 push ebp
00000208 48 dec eax
00000209 89E5 mov ebp,esp
0000020B 48 dec eax
0000020C C745F800800B00 mov dword [ebp-0x8],0xb8000
00000213 48 dec eax
00000214 8B45F8 mov eax,[ebp-0x8]
00000217 C60053 mov byte [eax],0x53
0000021A 90 nop
0000021B 5D pop ebp
0000021C C3 ret
0000021D 0000 add [eax],al
0000021F 001400 add [eax+eax],dl
00000222 0000 add [eax],al
00000224 0000 add [eax],al
00000226 0000 add [eax],al
00000228 017A52 add [edx+0x52],edi
0000022B 0001 add [ecx],al
0000022D 7810 js 0x23f
0000022F 011B add [ebx],ebx
00000231 0C07 or al,0x7
00000233 08900100001C or [eax+0x1c000001],dl
00000239 0000 add [eax],al
0000023B 001C00 add [eax+eax],bl
0000023E 0000 add [eax],al
00000240 C7 db 0xc7
00000241 FF db 0xff
00000242 FF db 0xff
00000243 FF16 call [esi]
00000245 0000 add [eax],al
00000247 0000 add [eax],al
00000249 41 inc ecx
0000024A 0E push cs
0000024B 108602430D06 adc [esi+0x60d4302],al
00000251 51 push ecx
00000252 0C07 or al,0x7
00000254 0800 or [eax],al
00000256 0000 add [eax],al
How I compile:
1. nasm link.asm -f elf64 -o llink.o
2. nasm start_boot.asm -f bin -o boot.bin
3. gcc -ffreestanding -c kernel.c -o krnl.o
4. ld -o krnlf.bin -Ttext 0x1000 link.o krnl.o -oformat binary
5. cat link.o krnl.o > osimg
Notes:
- I'll be compiling the "link.asm" as
elf64otherwise, GCC Linker will tell you that: "Link.asm is not compatible with 'i386:x86_64' output" - sure, should be binary.
- I tried -fno-pie, -no-stdlib, -fno-builtin and combined them but still.
- This where I link "link.o" and "krnl.o".
- to combine/stitch them together?
UPDATE: Now I removed the header file; "get_sector.asm"
and edited my bootsector, compiled it. here's the code of my latest bootsector:
[org 7c000h]
DRIVE_ID db 0
KERNEL_HEX equ 0x1000
mov bp, 9000h
mov sp, bp
mov bh, [_realmode]
call _print
call prep_kernel
call init_gdt
jmp $
%include "print_str.asm"
%include "print_str_pm.asm"
%include "gdt_conf.asm"
%include "init_protm.asm"
_realmode db "Bit mode: 16-bit", 0
_pmmode db "Bit mode: 32-bit", 0
_kernel_lod db "Kernel is loading... Please wait....", 0
[bits 16]
prep_kernel:
mov bh, _kernel_lod
call _print
mov ah, 02h
mov al, 15
mov ch, 0
mov cl, 1
mov dh, 0
mov dl, [DRIVE_ID]
mov bx, KERNEL_HEX
mov es, bx
int 13h
ret
[bits 32]
launch_kernel:
mov ebx, _kernel_lod
call _print_pm
call KERNEL_HEX
jmp $
times 510 - ($ - $$) db 0
dw 0xAA55
now QEmu produces the following output:
SeaBIOS bla bla...
iPXE bla bla...
Booting from Hard Disk...
_
it made a space before the cursor... maybe it booted successfully? or what?
Sorry for the long Question... -_-
