Re: [RFC 2/2] dyn ftrace porting of IA64

[Ingo Molnar <mingo@elte.hu>]

* Steven Rostedt <srostedt@redhat.com> wrote:

> On Thu, 2008-12-18 at 11:17 +0800, Shaohua Li wrote:
> > This is the IA64 port of dyn ftrace. In IA64, there are some issues we
> > must solve.
> > 1. kernel compile has different option against module compile, so I
> > extend the Makefile.build/recordmcount.pl script to distinct the two
> > cases.
> > 2. in a module, each routine's mcount call will call a PLT stub, which
> > will call kernel mcount. We can't simply make the mcount call call into
> > kernel mcount, as kernel and mocule have different gp and the
> > instruction just supports 25bit offset. So I introduced a new PLT stub,
> > which will call into kernel ftrace_caller. When module loading, all
> > mcount call will be converted to nop. When the nop is converted to call,
> > we make the call to the new PLT stub instead of old mcount PLT stub.
> 
> Have you taken a look at how powerpc64 does it?
> 
> You can look at Ingo's tip tree under the branch tip/tracing/powerpc, or 
> my own tree under tip/ftrace/ppc.

it's at:

  http://people.redhat.com/mingo/tip.git/README

> My tree is at:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git

	Ingo