Re: [PATCH v15 00/10] arm64: Add kernel probes (kprobes) support

[David Long]

On 07/19/2016 09:57 AM, Catalin Marinas wrote:
> On Thu, Jul 14, 2016 at 05:22:08PM +0100, Catalin Marinas wrote:
> > On Fri, Jul 08, 2016 at 12:35:44PM -0400, David Long wrote:
> > > David A. Long (3):
> > >    arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature
> > >    arm64: Add more test functions to insn.c
> > >    arm64: add conditional instruction simulation support
> > >
> > > Pratyush Anand (2):
> > >    arm64: Blacklist non-kprobe-able symbol
> > >    arm64: Treat all entry code as non-kprobe-able
> > >
> > > Sandeepa Prabhu (4):
> > >    arm64: Kprobes with single stepping support
> > >    arm64: kprobes instruction simulation support
> > >    arm64: Add kernel return probes support (kretprobes)
> > >    kprobes: Add arm64 case in kprobe example module
> > >
> > > William Cohen (1):
> > >    arm64: Add trampoline code for kretprobes
> >
> > I applied these patches on top of the arm64 for-next/core branch an
> > tried to run the resulting kernel in a guest (on a Juno platform using
> > both kvmtool and qemu) with KPROBES_SANITY_TEST enabled. Unfortunately,
> > the kernel fails to boot with lots of "Unexpected kernel single-step
> > exception at EL1".
>
> FYI, we managed to track down the issue to two bugs in the arm64 kernel
> boot part, occasionally leaving the PSTATE.D bit set for kernel threads.
> While not KVM specific, the pre-conditions were more likely when running
> as a guest (receiving interrupts early on during boot, possibly because
> of a slow-down in the booting process due to stage 2 page faulting
> mechanism).
>
> Will is going to post the fixes soon.

Excellent news.

Thanks,
-dl