(jdk10) RFR(xxs): 8176872: [s390] wrong pc shown in error logs

[Thomas Stüfe]

Hi David, thanks for the review! Let's keep the s390-only solution for now.
Cleanup can be done in a separate fix.

Kind Regards, Thomas

On Wed, Mar 22, 2017 at 12:47 AM, David Holmes <david.holmes at oracle.com>
wrote:

> Hi Thomas,
>
> On 21/03/2017 11:40 PM, Thomas Stüfe wrote:
>
>> Hi all,
>>
>> please take a look at this tiny fix. It fixes the pc shown as faulting
>> address for SIGILL and SIGFPE in hs_err files.
>>
>> https://bugs.openjdk.java.net/browse/JDK-8176872
>> http://cr.openjdk.java.net/~stuefe/webrevs/8176872-s390-wron
>> g-pc-in-errorlogs/jdk10-webrev.00/webrev/
>>
>> When determining the crash pc, in all posix platform signal handlers pc is
>> taken from the context. However, context.pc on zlinux points to the
>> instruction *after* the faulting op. The correct way, according to POSIX,
>> would be to take the address from siginfo_t->si_addr for signals SIGILL,
>> SIGFPE.
>>
>
> Well si_addr is the platform independent POSIX way of getting the address.
> Getting it from the uc_mcontext is architecture specific and seemingly not
> specified as to what the "pc" actually contains - the faulting instruction
> or the next instruction. If it were specified then the bug might be in
> zlinux :)
>
> (actually, this patch would make sense for all POSIX platforms, but only
>> s390 seems to show this error, so I leave the patch local to s390.)
>>
>
> I think it is historical that we get the PC from the uc_mcontext because
> originally we did not have SA_SIGINFO available. So a broader cleanup of
> this code is certainly possible. But for now this S390 fix seems fine.
>
> Thanks,
> David
> -----
>
> Kind Regards, Thomas
>>
>>