{"record":{"id":"166c197e3350f552","repo":"NationalSecurityAgency/ghidra","slug":"could-not-find-a-register-for","errorCode":null,"errorMessage":"Could not find a register for ","messagePattern":"Could not find a register for ","errorType":"validation","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/model/time/schedule/PatchStep.java","lineNumber":175,"sourceCode":"\t}\n\n\tprotected static void generateRegisterSleigh(List<String> result, Language language,\n\t\t\tAddressSpace space, SemisparseByteArray array) {\n\t\tbyte[] data = new byte[8];\n\t\tMutableULongSpanSet remains = new DefaultULongSpanSet();\n\t\tremains.addAll(array.getInitialized(0, -1));\n\t\twhile (!remains.isEmpty()) {\n\t\t\tULongSpan bound = remains.bound();\n\t\t\tAddress min = space.getAddress(bound.min());\n\t\t\tRegister register = Stream.of(language.getRegisters(min))\n\t\t\t\t\t.filter(r -> r.getAddress().equals(min))\n\t\t\t\t\t.filter(r -> r.getNumBytes() <= data.length)\n\t\t\t\t\t.filter(r -> isContained(r, remains))\n\t\t\t\t\t.sorted(Comparator.comparing(r -> -r.getNumBytes()))\n\t\t\t\t\t.findFirst()\n\t\t\t\t\t.orElse(null);\n\t\t\tif (register == null) {\n\t\t\t\tthrow new IllegalArgumentException(\"Could not find a register for \" + min);\n\t\t\t}\n\t\t\tif (register.getBaseRegister().isProgramCounter()) {\n\t\t\t\tregister = register.getBaseRegister();\n\t\t\t}\n\t\t\tint length = register.getNumBytes();\n\t\t\tarray.getData(register.getOffset(), data, 0, length);\n\t\t\tBigInteger value = Utils.bytesToBigInteger(data, length, language.isBigEndian(), false);\n\t\t\tif (register.isProgramCounter()) {\n\t\t\t\tresult.add(String.format(\"goto 0x%s\", value.toString(16)));\n\t\t\t}\n\t\t\telse {\n\t\t\t\tresult.add(String.format(\"%s=0x%s\", register, value.toString(16)));\n\t\t\t}\n\t\t\tremains.remove(spanOfRegister(register));\n\t\t}\n\t}\n\n\tpublic static PatchStep parse(long threadKey, String stepSpec) {","sourceCodeStart":157,"sourceCodeEnd":193,"githubUrl":"https://github.com/NationalSecurityAgency/ghidra/blob/d5f144c24d6bc53c9cbf4448c6d11143e7696206/Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/model/time/schedule/PatchStep.java#L157-L193","documentation":"Thrown by PatchStep while serializing a byte-patch into register assignments: for the next patched address 'min' in the register address space, no register was found that starts exactly at 'min', fits within the data length, and is contained in the remaining patched span (the stream over language.getRegisters(min) returned empty after the filters). The patch bytes therefore do not align to any register boundary defined by the language.","triggerScenarios":"Serializing a PatchStep whose patched byte range (in the register address space) does not begin on a register start offset, or covers bytes no single register (within the available length) can represent, e.g. a sub-register slice with no enclosing register, or a patch that straddles register boundaries without covering a whole register.","commonSituations":"Emulator/tracer writing partial-register bytes that don't align to any defined register; custom languages where the register set doesn't cover the patched offset; patches produced by p-code ops touching unmapped register offsets.","solutions":["Align the patched range to whole registers (start at a register boundary and span whole register widths).","Verify the language defines a register at that offset; if not, patch the underlying memory/register space differently.","When building the PatchStep, decompose arbitrary byte ranges into per-register patches before serialization.","Catch IllegalArgumentException and report the offending offset 'min' to locate the misaligned patch."],"exampleFix":"// before\n// patch starts at a sub-offset no register begins at -> 'Could not find a register for 0x..'\n\n// after\n// snap the patch start to the nearest enclosing register's offset\nRegister enc = language.getRegister(new AddressRangeImpl(min, min));\nlong regOff = enc != null ? enc.getOffset() : min;\n// build the patch from regOff covering enc.getNumBytes()","handlingStrategy":"try-catch","validationCode":"// Before building/serializing a PatchStep, verify each patched span starts on a register:\nRegister reg = Stream.of(language.getRegisters(addr))\n    .filter(r -> r.getAddress().equals(addr))\n    .findFirst().orElse(null);\nif (reg == null) { /* re-align the patch to a register boundary */ }","typeGuard":"static boolean alignedToRegister(Language lang, Address addr, int maxBytes) {\n    return Stream.of(lang.getRegisters(addr))\n        .anyMatch(r -> r.getAddress().equals(addr) && r.getNumBytes() <= maxBytes);\n}","tryCatchPattern":"try {\n    patchStep.serialize(language);\n} catch (IllegalArgumentException e) {\n    // e.getMessage() names the misaligned address 'min'; decompose the patch into per-register writes\n}","preventionTips":["Align patched byte ranges to whole registers (register start offset + full width).","Decompose arbitrary byte patches into per-register patches before serializing.","Confirm the language defines a register at the patched offset for custom languages."],"tags":["ghidra","trace-modeling","schedule","patch-step","register","alignment"],"backgroundTag":null,"analyzedSha":"d5f144c24d6bc53c9cbf4448c6d11143e7696206","analyzedAt":"2026-08-14T01:00:57.564Z","schemaVersion":2},"datasetVersion":"2026-08-14T05:17:29.042Z"}