Re: [for-next][PATCH 12/16] kprobes: Initialize kprobes at postcore_initcall

[Catalin Marinas]

On Tue, Jul 02, 2019 at 05:50:09PM +0100, Mark Rutland wrote:
> On Sun, May 26, 2019 at 03:18:40PM -0400, Steven Rostedt wrote:
> > From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > 
> > Initialize kprobes at postcore_initcall level instead of module_init
> > since kprobes is not a module, and it depends on only subsystems
> > initialized in core_initcall.
> > This will allow ftrace kprobe event to add new events when it is
> > initializing because ftrace kprobe event is initialized at
> > later initcall level.
> > 
> > Link: http://lkml.kernel.org/r/155851394736.15728.13626739508905120098.stgit@devnote2
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
> > ---
> >  kernel/kprobes.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index b1ea30a5540e..54aaaad00a47 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -2289,6 +2289,7 @@ static int __init init_kprobes(void)
> >  		init_test_probes();
> >  	return err;
> >  }
> > +postcore_initcall(init_kprobes);
> 
> As a heads-up, this is causing boot-time failures on arm64.
> 
> On arm64 kprobes depends on the BRK handler we register in
> debug_traps_init(), which is an arch_initcall.
> 
> As of this change, init_krprobes() calls init_test_probes() before
> that's registered, so we end up hitting a BRK before we can handle it.

Thanks Mark for identifying this.

So we either revert the above commit in -next or queue the one below
together with the rest of the kprobes changes (I can queue it via the
arm64 for-next/core assuming that the above commit id remains stable):

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