IJ44596: JAVA JIT: INVALID HARD-CODING OF STATIC FINAL FIELD OBJECT PROPERTIES

APAR status

• Closed as program error.

Error description

• Error Message: SIGSEGV inside JIT compiled code
  .
  Stack Trace: N/A
  .
  The issue effect all IBM JVM (OpenJ9) supported platforms. It is
  mostly likely to cause a problem in AOT compiled bodies that are
  then loaded in to a different JVM instance, but can also cause
  problems in cases where the reflection API is used to modify the
  contents of static final fields.
  

Local fix

• The problem can be avoided using the following java command line
  options:
  -Xjit:disableLookahead,disableGlobalVP
  -Xaot:disableLookahead,disableGlobalVPeGlobalVP
  The -Xjit options above are for normal non-AOT (non-cached)
  compiles and are unlikely to be required since the issue is far
  more likely with AOT (cached) compiles which is addressed by
  the "-Xaot" option above.
  These options (particularly the disableGlobalVP option) will
  have a measurable effect on performance of around 10% in most
  cases. The disableLookahead option will likely have no effect in
  most cases since the optimization is very rarely used already.
  The performance effect will be felt more for normal (-Xjit) opti
  then when using just the AOT (-Xaot) options.
  

Problem summary

• The JIT was inspecting heap objects pointed to by static final
  fields and using that information to hard code some values that
  would otherwise have been runtime queries against the object
  (i.e. array length checks). This would happen in some rare cases
  when compiling for AOT, which could cause issues if static final
  fields are initialized differently depending on JVM launch
  conditions. For non-AOT compiles this could still be a problem
  if the fields value is modified using the reflection API after
  compiling the method.
  

Problem conclusion

• The JIT was modified to remove cases where static final field
  inspection is used for AOT compiles and limit its use in non-AOT
  compiles to cases where we have in place mitigation techniques
  for when the contents of a static final field is modified
  through means like the reflection API.
  .
  This APAR will be fixed in the following Releases:
  .
  IBM SDK, Java Technology Edition
     8    SR8 FP5   (8.0.8.5)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  maintenance can be found at:
             https://www.ibm.com/support/pages/java-sdk
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels