stack pointer usage

[Ahmet Akkas]

Hi everybody,

In RTEMS, each task has its own stack. And I am just wondering
how stack pointer in the target architecture is set by task's
stack. For example, in m68k architecture a7 is the user stack
pointer. In the _CPU_Context_switch and _ISR_Handler assembly
routines, a7 user stack pointer is used and I did not see any
place where a7 gets the task's stack address. I am not OS person,
so I may have wrong interpretation of the RTEMS. But if somebody 
gives me how RTEMS deals with stack pointer (interaction between
the stack pointer used in the architecture and task's stack), 
I really appreciate it.

Thanks a lot.

Ahmet Akkas