On 9/13/18 7:19 PM, Bernd Eckenfels wrote:
Hallo Sean,
The change looks fine to me, but if you have to roll another version
maybe you could add a comment on this line to explain its purpose. Since
this line is changed in the patch it would be a good time:
System.java:350
sm.checkPackageAccess("java.lang");
Is that some kind of warm-up? (It cant be a sanity or security check as
its result is ignored.
Yes. If I recall, that forces the Policy implementation to be loaded
early and avoids potential class loading and/or stack recursion issues
if done later on. I played around with removing this a while back and
all sorts of things broke, so I'll do that again but this time add some
meaningful comments as to why it is needed.
I am curious, did you verify that the compiler will actually optimize
the getSecurityManager null check in case allow=never? Is that happening
in C1?
Yes, Claes did some initial testing and confirmed that the
constant-folded is occurring. See the comment in JDK-8191053 for more
info and some results:
https://bugs.openjdk.java.net/browse/JDK-8191053?focusedCommentId=14186619&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14186619
--Sean
Gruss
Bernd
Gruss
Bernd
--
http://bernd.eckenfels.net
------------------------------------------------------------------------
*Von:* -995614032m Auftrag von
*Gesendet:* Donnerstag, September 13, 2018 10:14 PM
*An:* security Dev OpenJDK
*Betreff:* RFR (12): 8191053: Provide a mechanism to make system's
security manager immutable
This is a SecurityManager related change which warrants some additional
details for its motivation.
The current System.setSecurityManager() API allows a SecurityManager to
be set at run-time. However, because of this mutability, it incurs a
performance overhead even for applications that never call it and do not
enable a SecurityManager dynamically, which is probably the majority of
applications.
For example, there are lots of "SecurityManager sm =
System.getSecurityManager(); if (sm != null) ..." checks in the JDK. If
it was known that a SecurityManager could never be set at run-time,
these checks could be optimized using constant-folding.
There are essentially two main parts to this change:
1. Deprecation of System.securityManager()
Going forward, we want to discourage applications from calling
System.setSecurityManager(). Instead they should enable a
SecurityManager using the java.security.manager system property on the
command-line.
2. A new JDK-specific system property to disallow the setting of the
security manager at run-time: jdk.allowSecurityManager
If set to false, it allows the run-time to optimize the code and improve
performance when it is known that an application will never run with a
SecurityManager. To support this behavior, the
System.setSecurityManager() API has been updated such that it can throw
an UnsupportedOperationException if it does not allow a security manager
to be set dynamically.
webrev: http://cr.openjdk.java.net/~mullan/webrevs/8191053/webrev.00/
CSR: https://bugs.openjdk.java.net/browse/JDK-8203316
JBS: https://bugs.openjdk.java.net/browse/JDK-8191053
(I will likely also send this to core-libs for additional review later)
--Sean
