linking files ?

[Sam111]

Ok , I have been at this for hours.

I am trying to run this code.

load2.asm

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global main
[BITS 32]

jmp main
hello	db	'This is sector 2!',13d,10d,'$' ;Put any data here!


main:
mov ax , 0
mov ds , ax 
mov es , ax

mov ax , 0x1110
mov ss , ax
mov sp , ax


mov ax , 600h       ; clear screen scroll up function
mov bh , 7h         ; white on black background
mov ch , 0h         ;upper line (top)
mov cl , 0h         ;left col (far left)
mov dh , 18h        ;bottom 
mov dl , 4Fh        ;far right
int 10h             ;do the clearing 

; display the string This is sector 2 on the screen
;mov ax , 0
;mov es , ax

mov ah , 13h
mov al , 01h 
mov bh , 0h
mov bl , 0Fh
mov dh , 5h
mov dl , 3h
mov cx , hello
mov bp , cx
mov cx , 16d
int 10h
; loop forever
extern _sound
call _sound

endsss:
jmp endsss

sound.c

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void sound();
static void play_sound(long int) ;
static void nosound();
void beep() ;
unsigned char inb (unsigned short ) ;
void outb (unsigned short , unsigned char ) ;


void sound()
{
int i = 1 ;
while( i == 1 )
{
beep() ;
}

}


 //Play sound using built in speaker
 static void play_sound(long int nFrequence) {
 	long int Div;
 	unsigned char tmp;
 
        //Set the PIT to the desired frequency
 	Div = 1193180 / nFrequence;
 	outb(0x43, 0xb6);
 	outb(0x42, (unsigned char) (Div) );
 	outb(0x42, (unsigned char) (Div >> 8));
 
        //And play the sound using the PC speaker
 	tmp = inb(0x61);
  	if (tmp != (tmp | 3)) {
 		outb(0x61, tmp | 3);
 	}
 }
 
 //make it shutup
 static void nosound() {
 	unsigned char tmp = (inb(0x61) & 0xFC);
 
 	outb(0x61, tmp);
 }
 
 //Make a beep
 void beep() {
 	 play_sound(1000);
 	 //timer_wait(10);
 	 nosound();
          //set_PIT_2(old_frequency);
 }
 
 
unsigned char inb (unsigned short _port)
{
    unsigned char rv;
    __asm__ __volatile__ ("inb %1, %0" : "=a" (rv) : "dN" (_port));
    return rv;
}

void outb (unsigned short _port, unsigned char _data)
{
    __asm__ __volatile__ ("outb %1, %0" : : "dN" (_port), "a" (_data));
}

everything compiles perfect
and I can link it perfectly to
ld -T link.ld load2.o sound.o -o kernel.bin

but the problem is it is not running correctly.

in my link.ld script

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OUTPUT_FORMAT("binary")
ENTRY(main)
phys = 0x00008000;
SECTIONS
{
  .text phys : AT(phys) {
    code = .;
    load2.o (.text);
    sound.o (.text);
    . = ALIGN(4096);
  }
  .data : AT(phys + (data - code))
  {
    data = .;
    *(.data)
    . = ALIGN(4096);
  }
  .bss : AT(phys + (bss - code))
  {
    bss = .;
    *(.bss)
    . = ALIGN(4096);
  }
  end = .;
}

I have used this load2 to boot before and I physically copied the kernel.bin to the second sector of my floppy as well as having my load2 copied to the first sector with the AA55 at the end.

objdump gives

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load2.o:     file format a.out-i386

Contents of section .text:
 0000 e9140000 00546869 73206973 20736563  .....This is sec
 0010 746f7220 32210d0a 2466b800 008ed88e  tor 2!..$f......
 0020 c066b810 118ed066 89c466b8 0006b707  .f.....f..f.....
 0030 b500b100 b618b24f cd10b413 b001b700  .......O........
 0040 b30fb605 b20366b9 05006689 cd66b910  ......f...f..f..
 0050 00cd10e8 a8ffffff ebfe9090           ............
Contents of section .data:

Contents of section .text:
 0000 55575653 bdb6ffff ffbf4200 0000be42  UWVS......B....B
 0010 000000bb 61000000 b9610000 0089e8e6  ....a....a......
 0020 43b0a989 faeeb004 89f2ee89 daec88c2  C...............
 0030 83ca0338 d0740488 d0e66189 caec83e0  ...8.t....a.....
 0040 fce661b8 01000000 83f80174 d05b5e5f  ..a........t.[^_
 0050 5dc383ec 1868e803 0000e821 000000e4  ]....h.....!....
 0060 6183e0fc e66183c4 1cc38b54 2404ec25  a....a.....T$..%
 0070 ff000000 c3908b54 24048a44 2408eec3  .......T$..D$...
 0080 83ec04b9 dc341200 89ca89c8 c1fa1ff7  .....4..........
 0090 7c240889 c1b0b6e6 4388c8e6 4289c8c1  |$......C...B...
 00a0 e808e642 e46188c2 83ca0338 d0740488  ...B.a.....8.t..
 00b0 d0e66183 c404c390 90909090 90909090  ..a.............
Contents of section .comment:
 00c0 4743433a 2028474e 55292033 2e310000  GCC: (GNU) 3.1..

as well as -h option

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sound.o:     file format coff-go32

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         000000c0  00000000  00000000  000000b4  2**4
                  CONTENTS, ALLOC, LOAD, CODE
  1 .data         00000000  000000c0  000000c0  00000000  2**4
                  ALLOC, LOAD, DATA
  2 .bss          00000000  000000c0  000000c0  00000000  2**2
                  ALLOC
  3 .comment      00000010  000000c0  000000c0  00000174  2**2
                  CONTENTS, DEBUGGING



load2.o:     file format a.out-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         0000005c  00000000  00000000  00000020  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, CODE
  1 .data         00000000  0000005c  0000005c  0000007c  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000000  0000005c  0000005c  00000000  2**2
                  ALLOC

I just have no clue on why the jmp main is not at address 0000:8000h because if it is then the program that I use on the MBR should boot and jmp to the main.

Basically this is the MBR code

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org 0x7C00
BITS 16
jmp start
greetings	    db	'Greetings and welcome ',13d,10d,'$' 
BOOTLOADER_NAME db 'Nates BootLoader Stage 1' ,13d,10d,'$'
STARTSECTOR     db  2            ;start sector to load
LOADADDRESS     dw  8000h       ; where to load the sectors into memory
NUMBEROFSECTORS db  1           ; number of bytes to load begining at STARTSECTOR

clear_screen:
mov ax , 600h      ; clear screen scroll up function
mov bh , 7h        ; white on black background
mov ch , 0h        ;upper line (top)
mov cl , 0h        ;left col (far left)
mov dh , 18h       ;bottom 
mov dl , 4Fh       ;far right
int 10h  ;                          do the clearing 
ret


readsectors_into_memory:
mov ah , 02h                    ; read function
mov al , 01h ;NUMBEROFSECTORS        ; number  of sectors to read
mov ch , 0h                     ; cylinder number
mov cl , 02h;STARTSECTOR            ; starting sector to begin reading from
mov dh , 0h                     ; head number
mov dl , 00h                    ;drive for floppy
mov bx , 8000h ; LOADADDRESS            ; es:bx-> buffer for where the sectors will be loaded in this case 0000:8000h

int 13h                          ; execute the interrupt for reading into memory
ret


start:
mov ax , 0x9100 ;set the stack to some random address
mov ss , ax
mov sp , 0x9000 ; set the stack pointer to some random address
xor ax , ax
mov ds , ax     ;data segment is at segment zero 
mov es , ax     ; exta segment is at segment zero now.

call clear_screen

mov ah , 13h
mov al , 01h 
mov bh , 0h
mov bl , 0Fh
mov dh , 5h
mov dl , 3h
mov cx , greetings
mov bp , cx
mov cx , 22d
int 10h


mov cx , BOOTLOADER_NAME
mov bp , cx
mov cx , 24d
mov dh , 10h
mov dl , 0h
int 10h

readData:
call readsectors_into_memory
jc readData


;so whatever is on the second sector of the floppy gets put in memory 0000:8000h
;then we jump to it. But when I jump to the kernel.bin  it doesn't work ... however it works with mostly all other programs so their must be something in the kernel.bin that is causeing this
jmp 0000:8000h

Also I am not sure about the algn = 2**4 or 2**2 and what it should be?
I can probably change this with my linker script but I don't know what I should have it at.

[Sam111]

I fix it by changing bits 32 to 16 in load2 that is how I originally had it.
But what I would like to know is what this alignment stuff is when I did an
objdump -h on the load2.o file I got that it changed from 2**2 to 2**3 ?

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C:\KERNEL~1>objdump -h load2.o

load2.o:     file format a.out-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00000050  00000000  00000000  00000020  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, CODE
  1 .data         00000000  00000050  00000050  00000070  2**3
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000000  00000050  00000050  00000000  2**3
                  ALLOC




sound.o:     file format coff-go32

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         000000c0  00000000  00000000  000000b4  2**4
                  CONTENTS, ALLOC, LOAD, CODE
  1 .data         00000000  000000c0  000000c0  00000000  2**4
                  ALLOC, LOAD, DATA
  2 .bss          00000000  000000c0  000000c0  00000000  2**2
                  ALLOC
  3 .comment      00000010  000000c0  000000c0  00000174  2**2
                  CONTENTS, DEBUGGING

I am assuming 2**2 means 4bytes and 2**3 means 8bytes alignment.
What exactly is this for and when would you need to use it.
In my link.ld the only line I don't understand is ALIGN(4096) what is this 4096 and why is it so important???

Thanks.

[KotuxGuy]

First off, bootloaders always start in real mode(16-bit), as that is how the processor starts up, and is why your bootloader wouldn't work as 32-bit(protected mode) code.
As for the ALIGN(4096)..

With the Intel x86 32-bit processors, a pages size is fixed at 4KB. 4096 bytes = 4KB. That way, when you enable paging, your code and variables aren't mangled.

But honestly, RTFM!!