[PATCH] arm: Add unwinding annotations for 64bit division functions

On Thu, 2011-09-22 at 12:57 +0100, Catalin Marinas wrote:

On Thu, Sep 22, 2011 at 12:06:46PM +0100, Jon Medhurst (Tixy) wrote:

quoted

On Thu, 2011-09-22 at 10:48 +0100, Catalin Marinas wrote:

quoted

We could improve things a bit in the unwinder and assume
that if the fault address is the same as the .fnstart address, the
return value is always in LR and the SP not affected (that's unwinding
bytecode 0xb0). For a few instructions into the function prologue we
can't reliably get the unwinding information.

That would help make it possible to unwind out of kprobes handlers to
the probed function. The kprobes code itself would need work as well,
and possibly the undef handler. Do we think it is worthwhile to do
this? 

Does kprobes need to trace beyond the probed function? If not, you get
the address of the probed function via pt_regs anyway, so no need for
unwinding beyond that.

To be honest, I'm not very sure how kprobes get used in the real world.
Though, if stack unwinding from their handlers currently doesn't work
and people had a usecase for it, we would expect them to complain.

-- 
Tixy