Controlling File Offset in linking - gcc

Question

I have some assembler for the Microblaze that I want to load at address 0x00000000 (ie to ensure it is executed on a reset).
I have a linker script that should do this (I think):
SECTIONS
{
ENTRY(_start)
. = 0x0000;
.vectors.reset : { *(.vectors.reset) }
. = 0x0008;
.vectors.sw_exception : { *(.vectors.sw_exception) }
. = 0x0010;
.vectors.interrupt : { *(.vectors.interrupt) }
. = 0x0018;
.vectors.hw_exception : { *(.vectors.hw_exception) }
. = 0x100;
.text : { *(.text) }
.data : { *(.data) }
.bss : { *(.bss) }
}
But when the code is compiled it seems to be offset by 0x1000:
objdump -h startup.MICROBLAZE.elf
startup.MICROBLAZE.elf: file format elf32-big
Sections:
Idx Name Size VMA LMA File off Algn
0 .vectors.reset 00000008 00000000 00000000 00001000 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .vectors.sw_exception 00000008 00000008 00000008 00001008 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
2 .vectors.interrupt 00000008 00000010 00000010 00001010 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
3 .vectors.hw_exception 00000008 00000018 00000018 00001018 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
4 .text 00000020 00000100 00000100 00001100 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE
Where does that offset come from and how can I supress/control it?
Edit: It seems the 0x1000 offset is the physical offset of the code section in the compiled file/object - is that correct?

Answer 1

According to your objdump listing everything is suppose to be laid out as you expect. I.e. VMA and LMA of your .text section are pointing to address 0x100.
The offset 0x1000 as you correctly guessed is offset of the .text section inside ELF file. But this section will be loaded to address 0x100.
If you try to disassemble your ELF with
$ objdump -S startup.MICROBLAZE.elf
you will see the proper instructions layout. It is also helpful to produce MAP file on a linkage stage with -Wl,-Map,output.map gcc flags.