Question

Im having problems when I define global variables in a basic C program for an ARM9 processor. I’m using EABI GNU compiler and the binary generated from a 12KB elf is 4GB! I assume the issue is with my scatter file but Im having trouble getting my head around it.

I have 256KB of ROM (base address 0xFFFF0000) and 32KBs of RAM (base 0x01000000)

SECTIONS {
  . = 0xFFFF0000;
  .text : {
    * (vectors);
    * (.text);
  }
  .rodata : { *(.rodata) }
  . = 0x01000000;
  sbss = .;
  .data : { *(.data) }
  .bss  : { *(.bss) }
  ebss = .;
  bssSize = ebss - sbss;
}

And my program is as follows:

int a=10;
int main() {
  int b=5;
  b = (a>b)? a : b;  
  return b;
};

If I declare a as a local variable, i.e. there is no .data section then everything works.
fine. Any help greatly appreciated.

–16th March 2011–
Can anyone help with this, Im getting nowhere and have read the manuals, forums etc…
My boot, compile command and objcopy commands are pasted below

     .section "vectors"
reset:  b   start
undef:  b   undef
swi:    b   swi
pabt:   b   pabt
dabt:   b   dabt
    nop
irq:    b   irq
fiq:    b   fiq

  .text
start:
        ldr   sp, =0x01006000
        bl    main

stop:   b     stop

arm-none-eabi-gcc -mcpu=arm926ej-s -Wall -nostartfiles -Wall main.c boot.s -o main.elf -T \ scatter_file
arm-none-eabi-objcopy ./main.elf –output-target=binary ./main.bin
arm-none-eabi-objdump ./main.elf –disassemble-all > ./main.dis

Answer 1

I found the problem. The objcopy command will try to create the entire address space described in the linker script, from the lowest address to the highest including everything in between. You can tell it to just generate the ROM code as follows:

objcopy ./main.elf -j ROM –output-target=binary ./main.bin

I also changed the linker script slightly

MEMORY {
  ram(WXAIL) : ORIGIN = 0x01000000, LENGTH = 32K    
  rom(RX)    : ORIGIN = 0xFFFF0000, LENGTH = 32K                    
}

SECTIONS {
  ROM : { 
    *(vectors);
    *(.text);
    *(.rodata);
  } > rom 

  RAM : {
    *(.data); 
    *(.bss);
  } > ram 
}