On Thu, 2009-11-19 at 15:05 -0500, Steven Rostedt wrote:
> Well, other archs use a register to store the return address. But it
> would also be easy to do (pseudo arch assembly):
>
> <function>:
> mov lr, (%sp)
> add 8, %sp
> blr __fentry__
Should be bl __fentry__ for "branch and link".
> sub 8, %sp
> mov (%sp), lr
>
>
> That way the lr would have the current function, and the parent would
> still be at 8(%sp)
Actually, if we add a new profiler and can make our own specification, I
would say that the add and sub lines be the responsibility of
__fentry__. Then we would have:
<function>:
mov lr, (%sp)
bl __fentry__
mov (%sp), lr
If sp points to the current content, then replace (%sp) above with
-8(%sp). Then the implementation of a nop __fentry__ would simply be:
__fentry__:
blr
For anything more elaborate, __fentry__ would be responsible for all
adjustments.
-- Steve
