RFR: JDK-8230413: Support Pre JDK 6 class with CDS

[David Holmes]

Hi Jiangli,

On 12/11/2019 8:12 am, Jiangli Zhou wrote:
> Please review the following change that allows archiving
> pre-JAVA_6_VERSION classes with -Xverify:none.
> 
> webrev: http://cr.openjdk.java.net/~jiangli/8230413/webrev.00/
> RFE: https://bugs.openjdk.java.net/browse/JDK-8230413
> 
> Currently there are still large number of existing classes (pre-built)
> with older class versions (< 50) in real world applications. Those
> classes are missing the benefit of archiving. Particularly, in some
> use cases, class verification can be safely disabled. For those use
> cases, supporting archiving pre JDK 6 classes shows good performance
> benefit. We can re-evaluate this support when -Xverify:none is removed
> in the future, hopefully the needs for supporting class version < 50
> is no longer significant at that time.
> 
> This change brings back the pre-JDK-8198849 behavior. Runtime makes
> sure the dump-time verification mode must be the same or stronger than
> the current mode.
> 
> A CSR may be needed for the change. Any thoughts on that?

A CSR request is definitely required given that you are proposing to 
undo a change that was itself put in place via a CSR request! And given 
this is relaxing a "defense-in-depth" check which will result in 
increasing exploitability, I think you will need a very strong argument 
to justify this.

Further this not only undoes JDK-8197972 but it also invalidates 
JDK-8155671 being closed as a duplicate of JDK-8197972. JDK-8155671 
requested a way to know if verification had been disabled, to help with 
analyzing crash reports, but instead we decided to not allow 
verification to be disabled.

David
-----



> Tested with jtreg appcds tests.
> 
> Best,
> Jiangli
>