Re: [PATCH 05/22 -v7] add notrace annotations to vsyscall.

Steven Rostedt
2008-01-30T13:15:36Z

On Wed, 30 Jan 2008, Peter Zijlstra wrote:

>
> On Tue, 2008-01-29 at 22:15 -0500, Steven Rostedt wrote:
> > plain text document attachment
> > (mcount-add-x86-vdso-notrace-annotations.patch)
> > Add the notrace annotations to some of the vsyscall functions.
>
> Would the VDSO stuff crash a kernel without these annotations and
> CONFIG_MCOUNT=y ?
>
> If so, I think it would be best of you placed these annotations before
> adding the core code, this would improve bisectability.

The thing is that MCOUNT needs something to select it, it's not a visible
option:

config MCOUNT
bool
select FRAME_POINTER

Nothing selects MCOUNT before the annotations are in, which really makes
the mcount code a nop until the tracer code comes in. A bisect (as long as
make oldconfig is done) should not be harmed by this patch ordering.
Note: the mcount patch introduces the annotation of notrace, which means
switching the order as it is will break it.

-- Steve