StubRoutines::load_long_atomic causes SIGBUS on aarch32

[Sergei Ustimenko]

Hi again,

I had to mention that I've checked the reference manual on armv7-a
and it says that address in the base register have to be doubleword
aligned. Most likely that causes SIGBUS. Though I just wanted to know
if anyone faced that before and may provide some quick tips.

Thanks,
Sergei

On Sat, 29 Dec 2018 at 17:01, Sergei Ustimenko <merkel05 at gmail.com> wrote:

> Hi,
>
> Recently I've stumbled upon quite curious situation in the aarch32 port.
> I have latest raspberry pi 3b+ which has an armv8-a CPU, that works
> in the compatibility mode. Raspbian in that case shows me that CPU
> is in the 32 bits mode and uses armv7-a instructions set.
>
> When I was building and testing the sandbox flavor of openjdk, amongst
> some tests that failed I've noticed an unusual one:
>
> TestAnonymousClassUnloading.java fails with:
>
> #  SIGBUS (0x7) at pc=0x73db4884, pid=5430, tid=5435
> #
> # JRE version: OpenJDK Runtime Environment (13.0) (build
> 13-internal+0-adhoc.pi.sandbox)
> # Java VM: OpenJDK Server VM (13-internal+0-adhoc.pi.sandbox, mixed mode,
> sharing, serial gc, linux-arm)
> # Problematic frame:
> # v  ~StubRoutines::atomic_load_long
>
> r0  = 0x5bde8e94
> 0x5bde8e94 is pointing into metadata
>
> pc  = 0x73db4884
> 0x73db4884 is at begin+4 in a stub
> StubRoutines::atomic_load_long [0x73db4880, 0x73db488c[ (12 bytes)
>
> StubRoutines::atomic_load_long [0x73db4880, 0x73db488c[ (12
> bytes)[Disassembling for mach='arm']
>   0x73db4880: ldrexd    r0, [r0]
>   0x73db4884: clrex
>   0x73db4888: bx        lr
> VM_Operation (0x643fe5f8): GenCollectFull, mode: safepoint, requested by
> thread 0x7609fc00
>
> Does anybody have any suggestion where I could read on why the `clrex`
> caused SIGBUS?
>
> Regards,
> Sergei
>