IV68296: MISSING RELOCATION IN AOT-COMPILED METHOD CAUSES JVM TO CRASH

APAR status

• Closed as program error.

Error description

• Error Message: A SIGSEGV or S0C4 ABEND is raised when an
  ahead-of-time (AOT) compiled Java method attempts to cast an
  object to a different type. The problem is most frequently
  observed in the AxesWalker.cloneDeep() method, with the
  following call stack for example, but the problem can
  potentially affect other code that calls the overridden clone()
  method recursively.
  .
  Stack Trace:
  org/apache/xpath/axes/AxesWalker.cloneDeep()org/apache/xpath/axe
  s/WalkingIterator.clone()org/apache/xpath/axes/IteratorPool.getI
  nstance()org/apache/xpath/axes/LocPathIterator.asIterator()org/a
  pache/xalan/templates/ElemForEach.transformSelectedNodes()
  .
  This problem is only triggered on System z (both z/OS and Linux)
  if the shared class cache is enabled.
  

Local fix

• This issue can be avoided by first clearing the shared class
  cache (with the -Xshareclasses:destroy option), and then
  disabling several optimizations in the AOT compiler with this
  option:-Xaot:disableAOTCheckCastInlining,disableAOTInstanceOfInl
  ining,disableAOTMethodEnterExitNote, however, that the
  "disableAOTMethodEnterExit" option will prevent
  methodenter/methodexit tracing (e.g. in a debugger).
  

Problem summary

• The problem is caused when the AOT compiler incorrectly merges
  two class pointer constants that both need to be relocated at
  run time, but belong to different inlined method calls. As a
  result, in the rare case that the inlining is invalidated at run
  time, the relocation could be skipped, leading to a crash when
  the constant is used on the other, valid code path.
  

Problem conclusion

• The AOT compiler has been fixed to generate relocatable class
  pointer constants in such situations.
  .
  This APAR will be fixed in the following Java Releases:
     7    SR9       (7.0.9.0)
     6 R1 SR8 FP4   (6.1.8.4)
     7 R1 SR3       (7.1.3.0)
     8    SR1       (8.0.1.0)
     6    SR16 FP4  (6.0.16.4)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the Service
  Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

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:

  PI32463

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R260 PSY

     UP

• R130 PSY

     UP