RFR(M) 8212605: Pure-Java implementation of AccessController.doPrivileged

[Sean Mullan]

Some of the copyrights need to be updated to 2018.

All else looks good to me as I had reviewed an earlier version of this 
before. We have talked about doing this for a while now, so I am finally 
glad we and are able to pretty much eliminate one of the more common 
SecurityManager related hot-spots and give a performance boost to 
applications that don't use the SM as well.

--Sean

On 10/31/18 6:23 PM, dean.long at oracle.com wrote:
> https://bugs.openjdk.java.net/browse/JDK-8212605
> http://cr.openjdk.java.net/~dlong/8212605/webrev.1
> 
> This change implements AccessController.doPrivileged in Java.  This 
> gives a performance improvement while also being useful to Project Loom 
> by removing the Java --> native --> Java transition.  One reason 
> doPrivileged has historically been in native is because of the need to 
> guarantee the cleanup of the privileged context when doPrivileged 
> returns.  To do that in Java, the information that 
> AccessController.getContext needs is pushed onto the Java stack as 
> arguments to a method that getContext will recognize during its stack 
> walk.  This allows us to remove the native privileged stack while 
> guaranteeing that the privileged context goes away when the method returns.
> 
> Tested with tier1-tier3 hotspot and jdk tests and JCK api/java_security 
> tests.  For the first few rounds of testing, I kept the old native 
> privileged stack and compared the results of the old and new 
> implementations for each getContext call, which did catch some early 
> bugs.  The changes were also examined by internal security experts and 
> run through additional internal security tests.
> 
> The improvement on this [1] doPrivileged microbenchmark is approximate 50x.
> 
> There is no attempt to optimize getContext() or security permission 
> checks in this change, however, this is intended to be a first step 
> towards other possible improvements, for example those proposed here [2].
> 
> dl
> 
> [1] 
> http://hg.openjdk.java.net/code-tools/jmh-jdk-microbenchmarks/file/fc4783360f58/src/main/java/org/openjdk/bench/java/security/DoPrivileged.java 
> 
> [2] 
> http://mail.openjdk.java.net/pipermail/security-dev/2017-December/016627.html 
> 
>