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I'm looking at arch/arm/boot/compressed/head.S in linux kerenl.

My board is odroid-S and when I see my symbol table which I got from readelf -S arch/arm/boot/compressed/vmlinux and I see these codes.

    LC0:  .word LC0         @ r1 
    .word   __bss_start     @ r2 
    .word   _end            @ r3 
    .word   zreladdr        @ r4 
    .word   _start          @ r5 
    .word   _got_start      @ r6 
    .word   _got_end        @ ip 
    .word   user_stack+4096     @ sp `

But the address each they have is not sequenced. As an example, LC0 value is 0000013c but __bss_start is 0031a734.

Can anybody tell me what confirms the values of these symbols???

g3rv4
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Young Hyun Yoo
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1 Answers1

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When compiling a baremetal implementation of software like an OS or bootloader, one will have a platform specific linker script will specify what addresses each section will go into. The linker script will be written according to the platform's memory map.

When the operating system loads an executable, the operating system loaded will read the various sections in your elf file and ensure that each gets placed into the correct section of the process's memory map. The OS loader will then fix any unlinked addresses as required.

doron
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    Yes, on a gross scale. But the addresses of the detailed entries mentioned in the question are as much a result of fitting the smaller pieces one after another into the specified sections. The more significant part of the addresses come from the section assignments, while the less significant parts come from the length of whatever preceded within that section. – Chris Stratton Nov 30 '12 at 17:46