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Problems with tutorial. http://forums.osdever.net/viewtopic.php?f=5&t=965 |
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Author: | Dr.Mallard [ Fri Mar 18, 2011 4:17 pm ] |
Post subject: | Problems with tutorial. |
Hi everybody. I have some questions about tutorials. More precisely those which are on bootloader running kernel written in c. I followed step by step it but i don't have the same result : i boot but the c kernel doesn't seem to be read... My computer runs with WinXP SP3. I use Notepad++ as text editor. I compile with the last version of nasm and DJGPP/GCC. I make my floppy images with makeboot and I run them with bochs. I tried with the partcopy, dd and vfd combo but without any success. I tried with Mingw/GCC... no more success. There is something i didn't see ? I write below the code i used (which can be found on this website): main.c Code: const char *tutorial3; void main() { clrscr(); print(tutorial3); for(;;); } const char *tutorial3 = "MuOS Tutorial 3"; video.c Code: void clrscr() { unsigned char *vidmem = (unsigned char *)0xB8000; const long size = 80*25; long loop; // Clear visible video memory for (loop=0; loop<size; loop++) { *vidmem++ = 0; *vidmem++ = 0xF; } // Set cursor position to 0,0 out(0x3D4, 14); out(0x3D5, 0); out(0x3D4, 15); out(0x3D5, 0); } void print(const char *_message) { unsigned short offset; unsigned long i; unsigned char *vidmem = (unsigned char *)0xB8000; // Read cursor position out(0x3D4, 14); offset = in(0x3D5) << 8; out(0x3D4, 15); offset |= in(0x3D5); // Start at writing at cursor position vidmem += offset*2; // Continue until we reach null character i = 0; while (_message[i] != 0) { *vidmem = _message[i++]; vidmem += 2; } // Set new cursor position offset += i; out(0x3D5, (unsigned char)(offset)); out(0x3D4, 14); out(0x3D5, (unsigned char)(offset >> 8)); } ports.c Code: unsigned char in(unsigned short _port) { // "=a" (result) means: put AL register in variable result when finished // "d" (_port) means: load EDX with _port unsigned char result; __asm__ ("in %%dx, %%al" : "=a" (result) : "d" (_port)); return result; } void out(unsigned short _port, unsigned char _data) { // "a" (_data) means: load EAX with _data // "d" (_port) means: load EDX with _port __asm__ ("out %%al, %%dx" : :"a" (_data), "d" (_port)); } loader.asm Code: [BITS 16] ; We need 16-bit intructions for Real mode [ORG 0x7C00] ; The BIOS loads the boot sector into memory location 0x7C00 mov ah, 0Eh ; Display 'A' mov al, 'A' mov bh, 0Fh mov bl, 0 int 10h reset_drive: mov ah, 0 ; RESET-command int 13h ; Call interrupt 13h or ah, ah ; Check for error code jnz reset_drive ; Try again if ah != 0 mov ax, 0 mov es, ax mov bx, 0x1000 ; Destination address = 0000:1000 mov ah, 02h ; READ SECTOR-command mov al, 02h ; Number of sectors to read = 1 mov ch, 0 ; Cylinder = 0 mov cl, 02h ; Sector = 2 mov dh, 0 ; Head = 0 int 13h ; Call interrupt 13h or ah, ah ; Check for error code jnz reset_drive ; Try again if ah != 0 cli ; Disable interrupts, we want to be alone xor ax, ax mov ds, ax ; Set DS-register to 0 - used by lgdt lgdt [gdt_desc] ; Load the GDT descriptor mov eax, cr0 ; Copy the contents of CR0 into EAX or eax, 1 ; Set bit 0 mov cr0, eax ; Copy the contents of EAX into CR0 jmp 08h:clear_pipe ; Jump to code segment, offset clear_pipe [BITS 32] ; We now need 32-bit instructions clear_pipe: mov ax, 10h ; Save data segment identifyer mov ds, ax ; Move a valid data segment into the data segment register mov ss, ax ; Move a valid data segment into the stack segment register mov esp, 090000h ; Move the stack pointer to 090000h jmp 08h:01000h ; Jump to section 08h (code), offset 01000h gdt: ; Address for the GDT gdt_null: ; Null Segment dd 0 dd 0 gdt_code: ; Code segment, read/execute, nonconforming dw 0FFFFh dw 0 db 0 db 10011010b db 11001111b db 0 gdt_data: ; Data segment, read/write, expand down dw 0FFFFh dw 0 db 0 db 10010010b db 11001111b db 0 gdt_end: ; Used to calculate the size of the GDT gdt_desc: ; The GDT descriptor dw gdt_end - gdt - 1 ; Limit (size) dd gdt ; Address of the GDT times 510-($-$$) db 0 ; Fill up the file with zeros dw 0AA55h ; Boot sector identifyer compile.bat Code: @echo on nasm -f bin loader.asm -o loader.bin gcc -ffreestanding -c main.c -o main.o gcc -c video.c -o video.o gcc -c ports.c -o ports.o ld -e _main -Ttext 0x1000 -o kernel.o main.o video.o ports.o ld -i -e _main -Ttext 0x1000 -o kernel.o main.o video.o ports.o objcopy -R .note -R .comment -S -O binary kernel.o kernel.bin makeboot floppy.img loader.bin kernel.bin pause bochs -f bochsrc.txt So, does this code run for you? Could you display code dump for kernel.bin, loader.bin and floppy.img, and their size in bytes? Or tell me what software do you use and with which parameters? Thanks you. |
Author: | Dr.Mallard [ Sun Mar 20, 2011 10:13 am ] |
Post subject: | Re: Problems with tutorial. |
That's ok. I solved my problem by using boil plate and linker script. |
Author: | brenden [ Tue Aug 23, 2011 1:15 am ] |
Post subject: | Re: Problems with tutorial. |
So what exactly was the issue and how did you fix it? It may be the compiler tools you are using. Some react differently than others. |
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