Ghidra emulator stops working when stumbled upon LOCK instruction

[nogitsune-youkai]

Describe the bug When emulating software which runs in VM, ghidra apparently can't emulate properly LOCK instruction. Is it a bug or i'm doing something wrong?

To Reproduce Steps to reproduce the behavior:

1. Simply launch emulator and emulate program

Expected behavior LOCK instruction should be emulated without issues.

Environment (please complete the following information):

• OS: [Win 11]
• Java Version: [21]
• Ghidra Version: [11.1]
• Ghidra Origin: [Github]

Additional context Full error log:

Sleigh userop 'LOCK' is not in the library ghidra.pcode.exec.ComposedPcodeUseropLibrary@21f3ab2b
ghidra.pcode.exec.PcodeExecutionException: Sleigh userop 'LOCK' is not in the library ghidra.pcode.exec.ComposedPcodeUseropLibrary@21f3ab2b
    at ghidra.pcode.exec.PcodeExecutor.step(PcodeExecutor.java:275)
    at ghidra.pcode.exec.PcodeExecutor.finish(PcodeExecutor.java:178)
    at ghidra.pcode.exec.PcodeExecutor.execute(PcodeExecutor.java:160)
    at ghidra.pcode.exec.PcodeExecutor.execute(PcodeExecutor.java:135)
    at ghidra.pcode.emu.DefaultPcodeThread.executeInstruction(DefaultPcodeThread.java:584)
    at ghidra.pcode.emu.DefaultPcodeThread.stepInstruction(DefaultPcodeThread.java:415)
    at ghidra.trace.model.time.schedule.Stepper$Enum$1.tick(Stepper.java:25)
    at ghidra.trace.model.time.schedule.TickStep.execute(TickStep.java:74)
    at ghidra.trace.model.time.schedule.Step.execute(Step.java:182)
    at ghidra.trace.model.time.schedule.Sequence.execute(Sequence.java:392)
    at ghidra.trace.model.time.schedule.TraceSchedule.finish(TraceSchedule.java:400)
    at ghidra.app.plugin.core.debug.service.emulation.DebuggerEmulationServicePlugin.doEmulateFromCached(DebuggerEmulationServicePlugin.java:723)
    at ghidra.app.plugin.core.debug.service.emulation.DebuggerEmulationServicePlugin.doEmulate(DebuggerEmulationServicePlugin.java:771)
    at ghidra.app.plugin.core.debug.service.emulation.DebuggerEmulationServicePlugin$EmulateTask.compute(DebuggerEmulationServicePlugin.java:262)
    at ghidra.app.plugin.core.debug.service.emulation.DebuggerEmulationServicePlugin$EmulateTask.compute(DebuggerEmulationServicePlugin.java:252)
    at ghidra.app.plugin.core.debug.service.emulation.DebuggerEmulationServicePlugin$AbstractEmulateTask.run(DebuggerEmulationServicePlugin.java:239)
    at ghidra.util.task.Task.monitoredRun(Task.java:134)
    at ghidra.util.task.TaskRunner.lambda$startTaskThread$0(TaskRunner.java:106)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
    at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: ghidra.pcode.exec.SleighLinkException: Sleigh userop 'LOCK' is not in the library ghidra.pcode.exec.ComposedPcodeUseropLibrary@21f3ab2b
    at ghidra.pcode.exec.PcodeExecutor.onMissingUseropDef(PcodeExecutor.java:578)
    at ghidra.pcode.emu.DefaultPcodeThread$PcodeThreadExecutor.onMissingUseropDef(DefaultPcodeThread.java:203)
    at ghidra.pcode.exec.PcodeExecutor.executeCallother(PcodeExecutor.java:562)
    at ghidra.pcode.exec.PcodeExecutor.stepOp(PcodeExecutor.java:249)
    at ghidra.pcode.emu.DefaultPcodeThread$PcodeThreadExecutor.stepOp(DefaultPcodeThread.java:180)
    at ghidra.pcode.exec.PcodeExecutor.step(PcodeExecutor.java:268)
    ... 20 more

[nsadeveloper789]

You'll need to define for the emulator what the LOCK pcode userop means. See https://github.com/NationalSecurityAgency/ghidra/blob/master/GhidraDocs/GhidraClass/Debugger/B4-Modeling.md. That tutorial goes into quite a bit more than you need, but essentialy, create a custom userop library that defines LOCK, then use a script to install an emulator with that library into the UI.

[nsadeveloper789]

Essentially, the same solution as found here, but for a different processor: https://github.com/NationalSecurityAgency/ghidra/issues/6089. It's very possible your definition is effectively a NOP.

[nogitsune-youkai]

Ok. Thank you, i'll look into it