[8u] RFR: 8149548: slowdebug build crashes if -XX:+TraceBytecodes flag is used

[Sergey Nazarkin]

Thank you, Ed. This fix was about SIGILL but you are right the line need to be swapped. I don’t know why we never get exception on JDK8


Sergey Nazarkin




> On 18 Feb 2016, at 20:12, Edward Nevill <edward.nevill at gmail.com> wrote:
> 
> Hi Sergey,
> 
> I was trying to forward port this patch to the jdk9 tree, but I get SEGVs on the slowdebug build even when just running 'java' on its own.
> 
> The problem seems to be the following part of the patch
> 
>     // Load *adr into c_rarg1, may fault.
>     *fault_pc = __ pc();
> +    __ mov(c_rarg2, c_rarg0);
>     switch (size) {
>       case 4:
> 
> The resultant code after patching looks like
> 
>    // Load *adr into c_rarg1, may fault.
>    *fault_pc = __ pc();
>    __ mov(c_rarg2, c_rarg0);
>    switch (size) {
>      case 4:
>        // int32_t
>        __ ldr(c_rarg0, Address(c_rarg2, 0));
>        break;
> 
> The problem seems to be that fault_pc is pointing to the mov c_rarg2, c_rarg0 rather than the actual instruction causing the fault.
> 
> What I don't quite understand is why we don't see the fault on the jdk8u tree, only the jdk9 tree. Maybe jdk8u isn't calling safefetch?
> 
> Anyway, if you agree that the correct fix is just to swap the lines I will push a patch.
> 
>    *fault_pc = __ pc();
>    __ mov(c_rarg2, c_rarg0);
> 
> to
> 
>    __ mov(c_rarg2, c_rarg0);
>    *fault_pc = __ pc();
> 
> Regards,
> Ed.
> 
> On Wed, 2016-02-10 at 15:59 +0000, Sergey Nazarkin wrote:
>> Hi!
>> 
>> Please review fix for JDK8 interpreter.  The changeset covers several SIGILL and NPE generated by signal handler
>> 
>> To reproduce call “java -XX:+TraceBytecodes -version”
>> 
>> http://cr.openjdk.java.net/~snazarki/8149548/
>> 
>> Sergey Nazarkin
>> 
>> 
>> 
>> 
> 
>