[U-Boot-Users] regarding exception frame

[Dileep Kumar]

Hi,
In the uboot1.1.6 code , there are some constants like
STACK_FRAME_OVERHEAD and STACK_UNDERHEAD in
the file  "\include\ppc_asm.tmpl " . Could you please tell me what are
the use of those constants ?

Here is one statement in the macro CRITICAL_EXCEPTION_PROLOG  in the
file "ppc_asm.tmpl"

subi    r21,r1,INT_FRAME_SIZE+STACK_UNDERHEAD;  /* alloc exc. frame */\

what is the need of STACK_UNDERHEAD here ?



In the macro STD_EXCEPTION there is a statement in the same file
    addi	r3,r1,STACK_FRAME_OVERHEAD

What is the need of STACK_FRAME_OVERHEAD here ?

Please clarify my doubts ....

Thanks
Dileep Kumar