[PATCH 2/2] ftrace - add ftrace function_graph support on ARM

[rabin@rab.in (Rabin Vincent)]

On Sat, Oct 09, 2010 at 08:37:57PM +0100, Russell King - ARM Linux wrote:
> On Sat, Oct 09, 2010 at 11:20:50PM +0530, Rabin Vincent wrote:
> > It's used just for the C entry functions for interrupts: asm_do_IRQ()
> > and the IPI and local timer functions.
> > 
> > AFAICS __exception seems to be used only for is_exception_text().  If
> > that's the case, would it be OK to just place those functions in
> > __irq_entry if ftrace is built and have is_exception_text() check that
> > section too?
> 
> No.  is_exception_text() is used to detect those functions which have
> a specific stack layout - which is that there's a pt_regs struct on the
> stack.  Grouping other functions into that violates the expectation.

I'm not sure I follow.  These functions (asm_do_IRQ(), do_IPI(), and
do_local_timer()) will be the only ones in __irq_entry. iow, __irq_entry
will contain nothing else except these functions.  So we woudn't be
grouping other functions; it's just that some of the __exception
functions would be moved to the new section so that __exception and
__irq_entry combined will contain the functions with the specific stack
layout (and only those functions).