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Hi!

I have my kernel loaded by GRUB. Its virtual address is 0xc0000000, and it gets loaded at 2MB. I've written my own linker script to achieve this (see below), and it seemed to work quite well.

However, after I introduced a new section (.init, intended to be discarded after kernel initialisation), I noticed that the physical addresses (LMA) of the sections behind the .bss differ from their virtual address (VMA), which of course causes severe problems when the kernel is booted.

Has anybody any idea about this?

Here is my linker script:

OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
OUTPUT_ARCH("i386")

ENTRY(_start)

MEMORY
{
physical : ORIGIN = 0x00200000, LENGTH = 4M
virtual  : ORIGIN = 0xc0000000, LENGTH = 4M
}

PHDRS
{
text PT_LOAD ;
init PT_LOAD ;
}

SECTIONS
{
. = 0xc0000000;

PROVIDE(stext = .);
PROVIDE(_stext = .);

.text :
{ *(.text)
  *(.rel.text) }
>virtual AT>physical : text

PROVIDE(etext = .);
PROVIDE(_etext = .);

PROVIDE(sdata = .);
PROVIDE(_sdata = .);

.data :
{ *(.data)
  *(.sdata)
  *(.rodata) }
>virtual AT>physical : text

PROVIDE(edata = .);
PROVIDE(_edata = .);

PROVIDE(sbss = .);
PROVIDE(_sbss = .);

.bss :
{ *(.bss)
  *(.sbss)
  *(COMMON) }
>virtual AT>physical : text

PROVIDE(ebss = .);
PROVIDE(_ebss = .);

PROVIDE(end = .);
PROVIDE(_end = .);

PROVIDE(sinit = .);
PROVIDE(_sinit = .);

.init :
{ *(.init.text)
  *(.init.data)
  *(.init.bss)
  *(.rel.init.text) }
>virtual AT>physical : init

PROVIDE(einit = .);
PROVIDE(_einit = .);

/DISCARD/ : { *(.note) *(.comment) }
}

Output of objdump -h kernel:
kernel:     file format elf32-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00001c50  c0000000  00200000  00001000  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .data         00000a40  c0001c60  00201c60  00002c60  2**5
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000008  c00026a0  002026a0  000036a0  2**2
                  ALLOC
  3 .init         000010e0  c00026c0  00202698  000036c0  2**5 // 26c0 != 2698
                  CONTENTS, ALLOC, LOAD, CODE

M. Schütz