RFR(m): 8074552: SafeFetch32 and SafeFetchN do not work in error handling

[Thomas Stüfe]

Hi David,

I see now that only Windows 32bit is broken. I will investigate this.

Thomas

On Mon, Mar 9, 2015 at 4:12 PM, Thomas Stüfe <thomas.stuefe at gmail.com>
wrote:

> Hi David,
>
> I am sorry, but I am unable to reproduce the error. Both slowdebug and
> fastdebug builds on Windows come up and SafeFetch works (also in error
> handling). Are you sure the crash is caused by my change? If yes, could you
> send me an hs-err file or at least the configure line you used for building?
>
> Kind Regards, Thomas
>
> On Mon, Mar 9, 2015 at 7:51 AM, David Holmes <david.holmes at oracle.com>
> wrote:
>
>> On 9/03/2015 4:21 PM, Thomas Stüfe wrote:
>>
>>> Hi David,
>>>
>>> Ouch. The only thing I can think about are the added initialization
>>> tests in stubRoutines.cpp. I will check this.
>>>
>>
>> Ah! It hadn't registered with me that this test code was going to be
>> executed. Seems the likely cause as a clean repo has no problems.
>>
>> David
>>
>>  Kind Regards, Thomas
>>>
>>>
>>>
>>> On Mon, Mar 9, 2015 at 6:56 AM, David Holmes <david.holmes at oracle.com
>>> <mailto:david.holmes at oracle.com>> wrote:
>>>
>>>     Hi Thomas,
>>>
>>>     FYI When I applied this to latest hs-rt forest and ran through JPRT
>>>     the Windows fastdebug builds were DOA (instant segfault just running
>>>     "java -version"). Can't see how your changes could do this so
>>>     running a test on unmodified forest.
>>>
>>>     David
>>>
>>>
>>>     On 9/03/2015 9:40 AM, David Holmes wrote:
>>>
>>>         Hi Thomas,
>>>
>>>         Minor nit: in
>>>         src/share/vm/runtime/__stubRoutines.cpp::test___safefetchN can
>>>         you use UCONST64 macro instead of explicit ULL - thanks.
>>>
>>>         Otherwise this seems okay, but we will also need the aarch64
>>>         component
>>>         (and I'll look into our internal needs).
>>>
>>>         Thanks,
>>>         David
>>>
>>>         On 7/03/2015 2:10 AM, Thomas Stüfe wrote:
>>>
>>>             Hi all,
>>>
>>>             could someone please review the following fix (I also will
>>>             need a
>>>             sponsor):
>>>
>>>             http://cr.openjdk.java.net/~__stuefe/webrevs/8074552/webrev.
>>> __01/
>>>             <http://cr.openjdk.java.net/~stuefe/webrevs/8074552/webrev.
>>> 01/>
>>>
>>>             https://bugs.openjdk.java.net/__browse/JDK-8074552
>>>
>>>             <https://bugs.openjdk.java.net/browse/JDK-8074552>
>>>
>>>             The fix will make SafeFetch[32,N] work in error reporting.
>>>
>>>             At SAP, we use SafeFetch a lot in error reporting to poke
>>>             around in
>>>             potentially invalid memory (e.g. writing hex dumps over
>>>             areas which
>>>             may be
>>>             partly unmapped), and we feel that this could be useful for
>>> the
>>>             OpenJDK too.
>>>
>>>             Without this fix, SafeFetch will cause a crash, the current
>>>             error
>>>             reporting
>>>             step will be interrupted and error reporting will continue
>>>             with the next
>>>             step; that is not optimal because the interrupted step may
>>>             have shown
>>>             valuable information.
>>>
>>>             This fix handles SafeFetch faults during error reporting the
>>>             same way as
>>>             they are handled normally. The changes are:
>>>
>>>             - handle safe fetch fault in the various (os_cpu dependend)
>>>             secondary
>>>             signal handlers
>>>
>>>             - provide a function to check if it is safe to use SafeFetch:
>>>             CanUseSafeFetch32(). SafeFetch needs stub routines and will
>>>             crash when
>>>             used
>>>             before stub generation.
>>>
>>>             - set_context_pc() is added which complements the existing
>>>             get_context_pc()
>>>             and all instances where the pc in ucontext_t was modified
>>>             directly are
>>>             changed to use set_context_pc()
>>>
>>>             - in stubRoutines.cpp, a small test was added to the already
>>>             existing
>>>             stub
>>>             routines tests which run at VM init
>>>
>>>             - in vmError.cpp, a test was added to test SafeFetch during
>>>             error
>>>             reporting, similar to the tests introduced for 8065895
>>>
>>>             - A JTreg test was added
>>>
>>>             Thanks and Kind Regards,
>>>
>>>             Thomas Stuefe
>>>
>>>
>>>
>