OSDev.org

Posted: **Mon Mar 30, 2009 4:03 pm**

my kernel compiled is 12kb and i define a stack of 8 kb. so the kernel should be about 20kb.. but if i try to calculate it with the end of the kernel (i use a symbol at the end of the linker) and the kernel start, i can see that is 104kb! there's something wrong on my operations or it is possible that the kernel is so big??

sorry for my bad english...

Posted: **Mon Mar 30, 2009 5:22 pm**

It might have to do with padding and/or alignment of the sections in your kernel binary. Hard to tell without looking at a linker map.

Posted: **Tue Mar 31, 2009 1:16 am**

here is the linker:

Code: Select all

OUTPUT_FORMAT("binary")
ENTRY(start)
phys = 0x00100000;
SECTIONS
{
  .text phys : AT(phys) {
    code = .;
    *(.text)
    *(.rodata)
    . = ALIGN(4096);
  }
  .data : AT(phys + (data - code))
  {
    data = .;
    *(.data)
    . = ALIGN(4096);
  }
  .bss : AT(phys + (bss - code))
  {
    bss = .;
    *(.bss)
    . = ALIGN(4096);
  }
  end = .;
}

that is nothing more then the Bran's tutorial..

Posted: **Tue Mar 31, 2009 1:28 am**

What you need to do is to run objdump and then you see what's in your kernel. What section is occupying too much space. And when you've seen this you can use objdump to see what symbols are present in that section.

Posted: **Tue Mar 31, 2009 4:51 am**

Srowen wrote:i can see that is 104kb! there's something wrong on my operations or it is possible that the kernel is so big??

Have you stripped the kenel? If not, all symbols may be present making it big. If it's an ELF file, using elfdump or the like to check.

JAL

Posted: **Tue Mar 31, 2009 8:31 am**

jal wrote:
Srowen wrote:i can see that is 104kb! there's something wrong on my operations or it is possible that the kernel is so big??
Have you stripped the kenel? If not, all symbols may be present making it big. If it's an ELF file, using elfdump or the like to check.

JAL

What does the first line of his linker script say?

Posted: **Tue Mar 31, 2009 1:11 pm**

Craze Frog wrote:What does the first line of his linker script say?

Sorry, hit that reply button too fast. Won't do again, promise.

JAL

Posted: **Wed Apr 01, 2009 10:41 am**

Craze Frog wrote:
jal wrote:
Srowen wrote:i can see that is 104kb! there's something wrong on my operations or it is possible that the kernel is so big??
Have you stripped the kenel? If not, all symbols may be present making it big. If it's an ELF file, using elfdump or the like to check.

JAL
What does the first line of his linker script say?

Well it wouldn't hurt to output an ELF variant of the kernel as well (or a mapfile). It's not fun to read through a 104kb binary file to see what's occupying all space.

Posted: **Wed Apr 01, 2009 1:05 pm**

Is the file really 104kb? Or is it just your calculations?

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