Bug ID: JDK-8214226 SA: Incorrect BCI and Line Number with jstack if the top frame is in the interpreter

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JDK 12	JDK 13
12 b24Fixed	13Fixed

mail snippet from David Griffiths below
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I have observed that if the top frame is in the interpreter it reports the BCI and line number incorrectly. This is because X86Frame.getInterpreterFrameBCI uses the value stored on the stack rather than the actual live value stored in R13.

I have a patch for this which lets LinuxAMD64JavaThreadPDAccess.getCurrentFrameGuess pass the R13 value to X86Frame so that the latter can then do:

  public int getInterpreterFrameBCI() {
    Address bcp = addressOfInterpreterFrameBCX().getAddressAt(0);
    // If we are in the top level frame then R13 may have been set for us which contains
    // the BCP. If so then let it take priority. If we are in a top level interpreter frame,
    // the BCP is live in R13 (on x86) and not saved in the BCX stack slot.
    if (r13 != null) {
        bcp = r13;
    }
    Address methodHandle = addressOfInterpreterFrameMethod().getAddressAt(0);

and this fixes the problem.

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This bug fix introduced the "illegal bci" failures we've been seeing on linux: JDK-8231634 and JDK-8222499.

23-04-2020

This fix was never applied to bsd-amd64, windows-amd64, and linux-x86. That means sometimes these platforms will see the same issue of a stale BCI and line number. I think we can ignore linux-x86. For the other two platforms we just need to apply the LinuxAMD64JavaThreadPDAccess changes to both WindowsAMD64JavaThreadPDAccess and BSDAMD64JavaThreadPDAccess: if (guesser.getPC() == null) { return new X86Frame(guesser.getSP(), guesser.getFP()); + } else if (VM.getVM().getInterpreter().contains(guesser.getPC())) { + // pass the value of R13 which contains the bcp for the top level frame + Address bcp = context.getRegisterAsAddress(AMD64ThreadContext.R13); + return new X86Frame(guesser.getSP(), guesser.getFP(), guesser.getPC(), null, bcp); } else { return new X86Frame(guesser.getSP(), guesser.getFP(), guesser.getPC()); } I've created JDK-8243500 to address this.

23-04-2020

Relates :	JDK-8231634 - SA stack walking fails with "illegal bci"
Relates :	JDK-8222499 - serviceability/sa/JhsdbThreadInfoTest.java fails with "AssertionFailure: illegal bci"
Relates :	JDK-8243500 - SA: Incorrect BCI and Line Number with jstack if the top frame is in the interpreter (BSD and Windows)