ELF binaries, a.out -- LONG

Ian Molton spyro at f2s.com
Tue Jul 6 01:03:03 PDT 2004


On Mon, 05 Jul 2004 22:51:38 -0700
Patrick Head <patrick at phead.net> wrote:

> 
> But multitasking OSes such as Unix have a problem.  All the directly
> set addresses and locations of variables, tables, and code jump
> points are fixed into the compiled binary file.  OK if we can always
> predict where the program will load in memory, but on a multitasking
> system we can't.

Not strictly true. OSes like linux use the MMU available in typical
modern system (yes I know about uClinux). This allows them to actuially
give every application an identical memory space. the applications
usually are linked to run at the lowest usable address in this range
(0x8000 for ARM I think) and the stack starts at the other end.

What *isnt* predictable, is where the shared libraries appear in the
memory map, and this is where the dynamic  linker and ELF come in...



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