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From "Pavel Rebriy" <pavel.reb...@gmail.com>
Subject Re: [jira] Updated: (HARMONY-788) [drlvm] Verifier: parameters and dimensions limit checks fix
Date Thu, 06 Jul 2006 12:47:40 GMT
During the first pass through bytecode verifier builds an instruction array
of the method. While building the instruction array verifier checks
constraints for each processed instruction. For instance, for instruction
working with local variables verifier checks a range of local variable
index, for constant pool index – range of constant pool index and type of
constant pool entry, and so on.

Java VM Specification has a limitation for arrays dimensions (it's limited
to 255). There are 2 instructions which create multi-dimensional arrays –
anewarray and multianewarray. The limitation should be checked for these
instructions. Checking it verifier constructs a type of created array and
counts a number of dimensions and check the limit.

Besides array dimensions Java VM Specification has a limit for number of a
method arguments (the limitation is 255 arguments). Parsing a descriptor of
an invoked method verifier counts the number of arguments and checks if it
exceeds the limit.

The test which checks the limitations seems to be quite synthetic but
verifier should be able to correctly process all classes loaded by VM.

On 06/07/06, Pavel Rebriy (JIRA) <jira@apache.org> wrote:
>
>      [ http://issues.apache.org/jira/browse/HARMONY-788?page=all ]
>
> Pavel Rebriy updated HARMONY-788:
> ---------------------------------
>
>     Attachment:
> 0001-Verifier-parameters-and-dimensions-limit-checks-fix.patch
>
> Patch to fix the problem.
>
> > [drlvm] Verifier: parameters and dimensions limit checks fix
> > ------------------------------------------------------------
> >
> >          Key: HARMONY-788
> >          URL: http://issues.apache.org/jira/browse/HARMONY-788
> >      Project: Harmony
> >         Type: Bug
>
> >   Components: VM
> >     Reporter: Pavel Rebriy
> >  Attachments: 0001-Test.zip,
> 0001-Verifier-parameters-and-dimensions-limit-checks-fix.patch
> >
> > I've found a bug that DRLVM verifier doesn't check array dimensions and
> method parameters limits as requested in Java VM Specification.
> > Test checks multianewarray instruction array dimensions and number of
> arguments for invokevirtual, invokespecial, invokeinterface and invokestatic
> instructions.
> > To run test use the following command:
> > <path to drl vm>/bin/ij Test
>
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>


-- 
Best regards,
Pavel Rebriy

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