user-mode stack size & location

[Clemens Kolbitsch <clemens.kol@gmx.at>]

hi!
i'm working on a new concept of i386 memory management and have to change 
quite a bit of the linux mm. could someone please point out, where the 
location & size of the USER-MODE stack is set for a new program (i.e. after 
calling sys_execve...) exactly?

I know that all settings are simply copied from the parent-process when 
invoking fork and how the stack grows (through page-faults).

However,

1.) is

  mm->start_stack

set inside the

  search_binary_handler / the individual fs-handlers?

i see that the aout-, elf-, etc. handlers all set this variable --> is this 
the only location where it can be set?

2.) when looking at /proc/PID/maps, i see that the stack always ends at 
different locations (obviously close to TASK_SIZE). thus the sizes seem to 
vary. where are they set / where are the infos written to the vma's / the 
PGD?

any help would be greatly appreciated!!
greets,
  clemens