Re: next: Rpi4: Unexpected kernel BRK exception at EL1

[Naresh Kamboju]

Hi Mark,

On Thu, 22 Jun 2023 at 15:12, Mark Rutland <mark.rutland@xxxxxxx> wrote:
>
> On Wed, Jun 21, 2023 at 01:57:21PM +0100, Mark Rutland wrote:
> > On Wed, Jun 21, 2023 at 06:06:51PM +0530, Naresh Kamboju wrote:
> > > Following boot warnings and crashes noticed on arm64 Rpi4 device running
> > > Linux next-20230621 kernel.
> > >
> > > Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> > >
> > > boot log:
> > >
> > > [   22.331748] Kernel text patching generated an invalid instruction
> > > at 0xffff8000835d6580!
> > > [   22.340579] Unexpected kernel BRK exception at EL1
> > > [   22.346141] Internal error: BRK handler: 00000000f2000100 [#1] PREEMPT SMP
> >
> > This indicates execution of AARCH64_BREAK_FAULT.
> >
> > That could be from dodgy arguments to aarch64_insn_gen_*(), or elsewhere, and
> > given this is in the networking code I suspect this'll be related to BPF.
> >
> > Looking at next-20230621 I see commit:
> >
> >   49703aa2adfaff28 ("bpf, arm64: use bpf_jit_binary_pack_alloc")
> >
> > ... which changed the way BPF allocates memory, and has code that pads memory
> > with a bunch of AARCH64_BREAK_FAULT, so it looks like that *might* be related.
>
> For the benefit of those just looknig at this thread, there has been some
> discussion in the original thread for this commit. Summary and links below.
>
> We identified a potential issue with missing cache maintenance:
>
>   https://lore.kernel.org/linux-arm-kernel/ZJMXqTffB22LSOkd@FVFF77S0Q05N/
>
> Puranjay verified that was causing the problem seen here:
>
>   https://lore.kernel.org/linux-arm-kernel/CANk7y0h5ucxmMz4K8sGx7qogFyx6PRxYxmFtwTRO7=0Y=B4ugw@xxxxxxxxxxxxxx/
>
> Alexei has dropped this commit for now:
>
>   https://lore.kernel.org/linux-arm-kernel/CAADnVQJqDOMABEx8JuU6r_Dehyf=SkDfRNChx1oNfqPoo7pSrw@xxxxxxxxxxxxxx/

Thanks for the detailed information.
I am happy to test any proposed fix patches.


>
> Thanks,
> Mark.

- Naresh