GP-3771: Add mask to the unwind analyzer (Fixes unwind with ARM/THUMB)

Ghidra/Debug/Debugger/ghidra_scripts/ComputeUnwindInfoScript.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -52,6 +52,7 @@ public class ComputeUnwindInfoScript extends GhidraScript {
 		}
 		println("Stack depth at " + currentAddress + ": " + info.depth());
 		println("Return address address: " + addressToString(info.ofReturn()));
+		println("Return address mask: 0x" + Long.toHexString(info.maskOfReturn()));
 		println("Saved registers:");
 		for (Entry<Register, Address> entry : info.saved().entrySet()) {
 			println("  " + entry);

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/gui/stack/vars/VariableValueHoverService.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -261,8 +261,7 @@ public class VariableValueHoverService extends AbstractConfigurableHover
 			}
 		}
 
-		record MappedLocation(Program stProg, Address stAddr, Address dynAddr) {
+		record MappedLocation(Program stProg, Address stAddr, Address dynAddr) {}
-		}
 
 		protected MappedLocation mapLocation(Program programOrView, Address address) {
 			if (programOrView instanceof TraceProgramView view) {
@@ -400,7 +399,7 @@ public class VariableValueHoverService extends AbstractConfigurableHover
 		public CompletableFuture<VariableValueTable> fillOperand(OperandFieldLocation opLoc,
 				Instruction ins) {
 			RefType refType = ins.getOperandRefType(opLoc.getOperandIndex());
-			if (refType.isFlow()) {
+			if (refType != null && refType.isFlow()) {
 				return null;
 			}
 			Object operand = ins.getDefaultOperandRepresentationList(opLoc.getOperandIndex())

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/stack/StackUnwindWarningSet.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -71,6 +71,11 @@ public class StackUnwindWarningSet implements Collection<StackUnwindWarning> {
 		return this.warnings.equals(that.warnings);
 	}
 
+	@Override
+	public String toString() {
+		return this.warnings.toString();
+	}
+
 	@Override
 	public int size() {
 		return warnings.size();

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/stack/Sym.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -96,6 +96,15 @@ sealed interface Sym {
 	 */
 	Sym twosComp();
 
+	/**
+	 * Logical bitwise and this and another symbol with the given compiler context
+	 * 
+	 * @param cSpec the compiler specification
+	 * @param in2 the second symbol
+	 * @return the resulting symbol
+	 */
+	Sym and(CompilerSpec cSpec, Sym in2);
+
 	/**
 	 * Get the size of this symbol with the given compiler for context
 	 * 
@@ -144,6 +153,11 @@ sealed interface Sym {
 			return this;
 		}
 
+		@Override
+		public Sym and(CompilerSpec cSpec, Sym in2) {
+			return this;
+		}
+
 		@Override
 		public Sym twosComp() {
 			return this;
@@ -166,19 +180,23 @@ sealed interface Sym {
 	public record ConstSym(long value, int size) implements Sym {
 		@Override
 		public Sym add(CompilerSpec cSpec, Sym in2) {
-			if (in2 instanceof ConstSym const2) {
+			return switch (in2) {
-				return new ConstSym(value + const2.value, size);
+				case ConstSym const2 -> new ConstSym(value + const2.value, size);
-			}
+				case RegisterSym reg2 when reg2.register() == cSpec
-			if (in2 instanceof RegisterSym reg2) {
+						.getStackPointer() -> new StackOffsetSym(value);
-				if (reg2.register() == cSpec.getStackPointer()) {
+				case StackOffsetSym off2 -> new StackOffsetSym(value + off2.offset);
-					return new StackOffsetSym(value);
+				default -> Sym.opaque();
-				}
+			};
-				return Sym.opaque();
+		}
-			}
+
-			if (in2 instanceof StackOffsetSym off2) {
+		@Override
-				return new StackOffsetSym(value + off2.offset);
+		public Sym and(CompilerSpec cSpec, Sym in2) {
-			}
+			return switch (in2) {
-			return Sym.opaque();
+				case ConstSym const2 -> new ConstSym(value & const2.value, size);
+				case RegisterSym reg2 -> reg2.withAppliedMask(value);
+				case StackDerefSym deref2 -> deref2.withAppliedMask(value);
+				default -> Sym.opaque();
+			};
 		}
 
 		@Override
@@ -203,13 +221,25 @@ sealed interface Sym {
 	/**
 	 * A register symbol
 	 */
-	public record RegisterSym(Register register) implements Sym {
+	public record RegisterSym(Register register, long mask) implements Sym {
 		@Override
 		public Sym add(CompilerSpec cSpec, Sym in2) {
-			if (in2 instanceof ConstSym const2) {
+			return switch (in2) {
-				return const2.add(cSpec, this);
+				case ConstSym const2 -> const2.add(cSpec, this);
-			}
+				default -> Sym.opaque();
-			return Sym.opaque();
+			};
+		}
+
+		@Override
+		public Sym and(CompilerSpec cSpec, Sym in2) {
+			return switch (in2) {
+				case ConstSym const2 -> const2.and(cSpec, this);
+				default -> Sym.opaque();
+			};
+		}
+
+		public RegisterSym withAppliedMask(long mask) {
+			return new RegisterSym(register, this.mask & mask);
 		}
 
 		@Override
@@ -244,10 +274,18 @@ sealed interface Sym {
 	public record StackOffsetSym(long offset) implements Sym {
 		@Override
 		public Sym add(CompilerSpec cSpec, Sym in2) {
-			if (in2 instanceof ConstSym const2) {
+			return switch (in2) {
-				return new StackOffsetSym(offset + const2.value());
+				case ConstSym const2 -> const2.add(cSpec, this);
-			}
+				default -> Sym.opaque();
-			return Sym.opaque();
+			};
+		}
+
+		@Override
+		public Sym and(CompilerSpec cSpec, Sym in2) {
+			return switch (in2) {
+				case ConstSym const2 -> const2.and(cSpec, this);
+				default -> Sym.opaque();
+			};
 		}
 
 		@Override
@@ -276,10 +314,25 @@ sealed interface Sym {
 	 * This represents a dereferenced {@link StackOffsetSym} (or the dereferenced stack pointer
 	 * register, in which is treated as a stack offset of 0).
 	 */
-	public record StackDerefSym(long offset, int size) implements Sym {
+	public record StackDerefSym(long offset, long mask, int size) implements Sym {
 		@Override
 		public Sym add(CompilerSpec cSpec, Sym in2) {
-			return Sym.opaque();
+			return switch (in2) {
+				case ConstSym const2 -> const2.add(cSpec, this);
+				default -> Sym.opaque();
+			};
+		}
+
+		@Override
+		public Sym and(CompilerSpec cSpec, Sym in2) {
+			return switch (in2) {
+				case ConstSym const2 -> const2.and(cSpec, this);
+				default -> Sym.opaque();
+			};
+		}
+
+		public StackDerefSym withAppliedMask(long mask) {
+			return new StackDerefSym(offset, this.mask & mask, size);
 		}
 
 		@Override

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/stack/SymPcodeArithmetic.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -65,6 +65,8 @@ class SymPcodeArithmetic implements PcodeArithmetic<Sym> {
 				return in1.add(cSpec, in2);
 			case PcodeOp.INT_SUB:
 				return in1.sub(cSpec, in2);
+			case PcodeOp.INT_AND:
+				return in1.and(cSpec, in2);
 			default:
 				return Sym.opaque();
 		}

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/stack/SymPcodeExecutorState.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -79,16 +79,16 @@ public class SymPcodeExecutorState implements PcodeExecutorState<Sym> {
 	public String toString() {
 		return String.format("""
 				%s[
-				    cSpec=%s
+				  cSpec=%s
-				    stack=%s
+				  stack=%s
-				    registers=%s
+				  registers=%s
-				    unique=%s
+				  unique=%s
 				]
 				""", getClass().getSimpleName(),
 			cSpec.toString(),
-			stackSpace.toString("    ", language),
+			stackSpace.toString("  ", language),
-			registerSpace.toString("    ", language),
+			registerSpace.toString("  ", language),
-			uniqueSpace.toString("    ", language));
+			uniqueSpace.toString("  ", language));
 	}
 
 	@Override
@@ -218,17 +218,37 @@ public class SymPcodeExecutorState implements PcodeExecutorState<Sym> {
 	 * <li>PC:Deref => location is [Stack]:PC.offset
 	 * </ul>
 	 * 
-	 * @return
+	 * @return the address (stack offset or register) of the return address
 	 */
 	public Address computeAddressOfReturn() {
-		Sym expr = getVar(language.getProgramCounter(), Reason.INSPECT);
+		return switch (getVar(language.getProgramCounter(), Reason.INSPECT)) {
-		if (expr instanceof StackDerefSym stackVar) {
+			case StackDerefSym stackVar -> cSpec.getStackSpace().getAddress(stackVar.offset());
-			return cSpec.getStackSpace().getAddress(stackVar.offset());
+			case RegisterSym regVar -> regVar.register().getAddress();
-		}
+			default -> null;
-		if (expr instanceof RegisterSym regVar) {
+		};
-			return regVar.register().getAddress();
+	}
-		}
+
-		return null;
+	/**
+	 * Examine this state's PC to determine how the return address is masked
+	 * 
+	 * <p>
+	 * This is only applicable in cases where {@link #computeAddressOfReturn()} returns a non-null
+	 * address. This is to handle architectures where the low bits indicate an ISA mode, and the
+	 * higher bits form the actual address. Often, the sleigh specifications for these processors
+	 * will mask off those low bits when setting the PC. If that has happened, and the symbolic
+	 * expression stored in the PC is otherwise understood to come from the stack or a register,
+	 * this will return that mask. Most often, this will return -1, indicating that all bits are
+	 * relevant to the actual address. If the symbolic expression does not indicate the stack or a
+	 * register, this still returns -1.
+	 * 
+	 * @return the mask, often -1
+	 */
+	public long computeMaskOfReturn() {
+		return switch (getVar(language.getProgramCounter(), Reason.INSPECT)) {
+			case StackDerefSym stackVar -> stackVar.mask();
+			case RegisterSym regVar -> regVar.mask();
+			default -> -1;
+		};
 	}
 
 	/**

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/stack/SymStateSpace.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -211,7 +211,10 @@ public class SymStateSpace {
 		return map.values()
 				.stream()
 				.map(se -> se.toString(language))
-				.collect(Collectors.joining("\n" + indent, indent + "{", "\n" + indent + "}"));
+				.collect(Collectors.joining(
+					"\n" + indent + indent,
+					"{\n" + indent + indent,
+					"\n" + indent + "}"));
 	}
 
 	private NavigableMap<Address, SymEntry> subMap(Address lower, Address upper) {
@@ -281,10 +284,10 @@ public class SymStateSpace {
 				Msg.warn(this, "Could not figure register: address=" + address + ",size=" + size);
 				return Sym.opaque();
 			}
-			return new RegisterSym(register);
+			return new RegisterSym(register, -1);
 		}
 		if (address.isStackAddress()) {
-			return new StackDerefSym(address.getOffset(), size);
+			return new StackDerefSym(address.getOffset(), -1, size);
 		}
 		return Sym.opaque();
 	}

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/stack/UnwindAnalysis.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -98,8 +98,7 @@ public class UnwindAnalysis {
 	/**
 	 * Wrap a {@link CodeBlock}
 	 */
-	record BlockVertex(CodeBlock block) {
+	record BlockVertex(CodeBlock block) {}
-	}
 
 	/**
 	 * Wrap a {@link CodeBlockReference}
@@ -492,6 +491,7 @@ public class UnwindAnalysis {
 							new UnwindException("Cannot determine address of return pointer");
 						continue;
 					}
+					long maskOfReturn = exitState.computeMaskOfReturn();
 					Long adjust = exitState.computeStackDepth();
 					if (adjust == null) {
 						lastError = new UnwindException("Cannot determine stack adjustment");
@@ -501,8 +501,8 @@ public class UnwindAnalysis {
 					warnings.addAll(exitState.warnings);
 					Map<Register, Address> mapByExit = exitState.computeMapUsingRegisters();
 					mapByExit.entrySet().retainAll(mapByEntry.entrySet());
-					return new UnwindInfo(function, depth, adjust, addressOfReturn, mapByExit,
+					return new UnwindInfo(function, depth, adjust, addressOfReturn, maskOfReturn,
-						new StackUnwindWarningSet(warnings), null);
+						mapByExit, new StackUnwindWarningSet(warnings), null);
 				}
 			}
 			if (lastSuccessfulEntryState != null) {
@@ -510,16 +510,16 @@ public class UnwindAnalysis {
 				try {
 					long adjust = SymPcodeExecutor.computeStackChange(function, warnings);
 					return new UnwindInfo(function, lastSuccessfulEntryState.computeStackDepth(),
-						adjust, null, lastSuccessfulEntryState.computeMapUsingStack(),
+						adjust, null, -1, lastSuccessfulEntryState.computeMapUsingStack(),
 						new StackUnwindWarningSet(warnings), lastError);
 				}
 				catch (Exception e) {
 					return new UnwindInfo(function, lastSuccessfulEntryState.computeStackDepth(),
-						null, null, lastSuccessfulEntryState.computeMapUsingStack(),
+						null, null, -1, lastSuccessfulEntryState.computeMapUsingStack(),
 						new StackUnwindWarningSet(warnings), e);
 				}
 			}
-			return new UnwindInfo(function, null, null, null, null,
+			return new UnwindInfo(function, null, null, null, -1, null,
 				new StackUnwindWarningSet(warnings), new UnwindException(
 					"Could not analyze any path from %s entry to %s.\n%s".formatted(function, pc,
 						lastError.getMessage()),

Ghidra/Debug/Debugger/src/main/java/ghidra/app/plugin/core/debug/stack/UnwindInfo.java

@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -31,12 +31,28 @@ import ghidra.util.task.TaskMonitor;
 
 /**
  * Information for interpreting the current stack frame and unwinding to the next
+ * 
+ * @param function see {@link #function()}
+ * @param depth see {@link #depth()}
+ * @param adjust see {@link #adjust()}
+ * @param ofReturn see {@link #ofReturn()}
+ * @param maskOfReturn see {@link #maskOfReturn()}
+ * @param saved see {@link #saved()}
+ * @param warnings see {@link #warnings()}
+ * @param error see {@link #error()}
  */
 public record UnwindInfo(Function function, Long depth, Long adjust, Address ofReturn,
-		Map<Register, Address> saved, StackUnwindWarningSet warnings, Exception error) {
+		long maskOfReturn, Map<Register, Address> saved, StackUnwindWarningSet warnings,
+		Exception error) {
 
+	/**
+	 * Construct an error-only info
+	 * 
+	 * @param error the error
+	 * @return the info containing only the error
+	 */
 	public static UnwindInfo errorOnly(Exception error) {
-		return new UnwindInfo(null, null, null, null, null, new StackUnwindWarningSet(), error);
+		return new UnwindInfo(null, null, null, null, -1, null, new StackUnwindWarningSet(), error);
 	}
 
 	/**
@@ -88,6 +104,29 @@ public record UnwindInfo(Function function, Long depth, Long adjust, Address ofR
 		return ofReturn;
 	}
 
+	/**
+	 * The mask applied to the return address
+	 * 
+	 * <p>
+	 * This is to handle ISAs that use the low bits of addresses in jumps to indicate an ISA switch.
+	 * Often, the code that returns from a function will apply a mask. If that is the case, this
+	 * returns that mask. In most cases, this returns -1, which when applied as a mask has no
+	 * effect.
+	 * 
+	 * <p>
+	 * <b>NOTE</b>: There is currently no tracking of the ISA mode by the stack unwinder. First, the
+	 * conventions for tracking that in the Sleigh specification varies from processor to processor.
+	 * There is often custom-made handling of that bit programmed in Java for the emulator, but it's
+	 * not generally accessible for static analysis. Second, for stack unwinding purposes, we use
+	 * the statically disassembled code at the return address, anyway. That should already be of the
+	 * correct ISA; if not, then we are already lost.
+	 * 
+	 * @return the mask, often -1
+	 */
+	public long maskOfReturn() {
+		return maskOfReturn;
+	}
+
 	/**
 	 * The <em>address of</em> the return address, given a stack base
 	 * 
@@ -172,7 +211,7 @@ public record UnwindInfo(Function function, Long depth, Long adjust, Address ofR
 	 * Add register map entries for the saved registers in this frame
 	 * 
 	 * @param base the current frame's base pointer, as in {@link #computeBase(Address)}
-	 * @param registerMap the register map of the stack to this point, to be modified
+	 * @param map the register map of the stack to this point, to be modified
 	 */
 	public void mapSavedRegisters(Address base, SavedRegisterMap map) {
 		for (Entry<Register, Address> ent : saved.entrySet()) {
@@ -221,7 +260,8 @@ public record UnwindInfo(Function function, Long depth, Long adjust, Address ofR
 			AddressSpace codeSpace, Register pc) {
 		T value = computeNextPc(base, state, pc);
 		long concrete = state.getArithmetic().toLong(value, Purpose.INSPECT);
-		return codeSpace.getAddress(concrete);
+		long masked = concrete & maskOfReturn;
+		return codeSpace.getAddress(masked);
 	}
 
 	/**

Ghidra/Debug/Debugger/src/test/java/ghidra/app/plugin/core/debug/stack/StackUnwinderTest.java

@@ -38,6 +38,7 @@ import ghidra.app.decompiler.*;
 import ghidra.app.decompiler.component.*;
 import ghidra.app.plugin.assembler.*;
 import ghidra.app.plugin.assembler.sleigh.sem.*;
+import ghidra.app.plugin.core.analysis.*;
 import ghidra.app.plugin.core.codebrowser.CodeBrowserPlugin;
 import ghidra.app.plugin.core.debug.disassemble.TraceDisassembleCommand;
 import ghidra.app.plugin.core.debug.gui.AbstractGhidraHeadedDebuggerTest;
@@ -81,6 +82,7 @@ import ghidra.trace.model.TraceLocation;
 import ghidra.trace.model.breakpoint.TraceBreakpoint;
 import ghidra.trace.model.breakpoint.TraceBreakpointKind;
 import ghidra.trace.model.listing.TraceData;
+import ghidra.trace.model.memory.TraceMemorySpace;
 import ghidra.trace.model.thread.TraceThread;
 import ghidra.trace.model.time.schedule.Scheduler;
 import ghidra.util.Msg;
@@ -587,6 +589,59 @@ public class StackUnwinderTest extends AbstractGhidraHeadedDebuggerTest {
 		}
 	}
 
+	protected Function createInfiniteRecursionProgramArm() throws Throwable {
+		createProgram("ARM:LE:32:v8", "default");
+		intoProject(program);
+		try (Transaction tx = program.openTransaction("Assemble")) {
+			Address entry = addr(program, 0x00400000);
+			program.getMemory()
+					.createInitializedBlock(".text", entry, 0x1000, (byte) 0, monitor, false);
+
+			Assembler asm = Assemblers.getAssembler(program.getLanguage());
+			AssemblyBuffer buf = new AssemblyBuffer(asm, entry);
+
+			Language language = asm.getLanguage();
+			Register regCtx = language.getContextBaseRegister();
+			Register regT = language.getRegister("T");
+			RegisterValue rvDefault = new RegisterValue(regCtx,
+				asm.getContextAt(entry).toBigInteger(regCtx.getNumBytes()));
+			RegisterValue rvThumb = rvDefault.assign(regT, BigInteger.ONE);
+			AssemblyPatternBlock ctxThumb = AssemblyPatternBlock.fromRegisterValue(rvThumb);
+
+			buf.emit(NumericUtilities.convertStringToBytes("00 b5")); // push {lr}
+			buf.emit(NumericUtilities.convertStringToBytes("00 04")); // lsl  r0,r0,#0x10
+			buf.emit(NumericUtilities.convertStringToBytes("00 0c")); // lsr  r0,r0,#0x10
+			buf.assemble("bl   0x%s".formatted(entry), ctxThumb);
+			bodyInstr = buf.getNext();
+			buf.assemble("pop  {r0}", ctxThumb);
+			buf.assemble("bx   r0", ctxThumb);
+
+			byte[] bytes = buf.getBytes();
+			program.getMemory().setBytes(entry, bytes);
+
+			Disassembler dis = Disassembler.getDisassembler(program, monitor, null);
+			dis.disassemble(entry, null, rvThumb, false);
+
+			Function func = program.getFunctionManager()
+					.createFunction("recurseInfinitely", entry,
+						new AddressSet(entry, entry.add(bytes.length - 1)),
+						SourceType.USER_DEFINED);
+			return func;
+		}
+	}
+
+	protected void openAndAnalyze(Function function) {
+		GhidraProgramUtilities.markProgramNotToAskToAnalyze(program);
+		programManager.openProgram(program);
+		waitForSwing();
+
+		AutoAnalysisManager analysisManager = AutoAnalysisManager.getAnalysisManager(program);
+		tool.executeBackgroundCommand(new AnalysisBackgroundCommand(analysisManager, true),
+			program);
+		analysisManager.reAnalyzeAll(function.getBody());
+		waitForTasks();
+	}
+
 	@Test
 	public void testComputeUnwindInfoX86_32() throws Throwable {
 		addPlugin(tool, CodeBrowserPlugin.class);
@@ -599,13 +654,14 @@ public class StackUnwinderTest extends AbstractGhidraHeadedDebuggerTest {
 		UnwindAnalysis ua = new UnwindAnalysis(program);
 
 		UnwindInfo infoAtEntry = ua.computeUnwindInfo(entry, monitor);
-		assertEquals(
+		assertEquals(new UnwindInfo(function, 0L, 4L, stack(0), -1,
-			new UnwindInfo(function, 0L, 4L, stack(0), Map.of(), new StackUnwindWarningSet(), null),
+			Map.of(), new StackUnwindWarningSet(), null),
 			infoAtEntry);
 
 		UnwindInfo infoAtBody = ua.computeUnwindInfo(bodyInstr, monitor);
-		assertEquals(new UnwindInfo(function, -20L, 4L, stack(0),
+		assertEquals(new UnwindInfo(function, -20L, 4L, stack(0), -1,
-			Map.of(register("EBP"), stack(-4)), new StackUnwindWarningSet(), null), infoAtBody);
+			Map.of(register("EBP"), stack(-4)), new StackUnwindWarningSet(), null),
+			infoAtBody);
 	}
 
 	@Test
@@ -623,16 +679,17 @@ public class StackUnwinderTest extends AbstractGhidraHeadedDebuggerTest {
 		UnwindAnalysis ua = new UnwindAnalysis(program);
 
 		UnwindInfo infoAtEntry = ua.computeUnwindInfo(entry, monitor);
-		assertEquals(
+		assertEquals(new UnwindInfo(function, 0L, 4L, stack(0), -1,
-			new UnwindInfo(function, 0L, 4L, stack(0), Map.of(), new StackUnwindWarningSet(), null),
+			Map.of(), new StackUnwindWarningSet(), null),
 			infoAtEntry);
 
 		UnwindInfo infoAtBody = ua.computeUnwindInfo(bodyInstr, monitor);
-		assertEquals(
+		assertEquals(new UnwindInfo(function, -20L, 4L, stack(0), -1,
-			new UnwindInfo(function, -20L, 4L, stack(0), Map.of(register("EBP"), stack(-4)),
+			Map.of(register("EBP"), stack(-4)),
-				new StackUnwindWarningSet(new UnspecifiedConventionStackUnwindWarning(myExtern),
+			new StackUnwindWarningSet(
-					new UnknownPurgeStackUnwindWarning(myExtern)),
+				new UnspecifiedConventionStackUnwindWarning(myExtern),
-				null),
+				new UnknownPurgeStackUnwindWarning(myExtern)),
+			null),
 			infoAtBody);
 	}
 
@@ -649,18 +706,47 @@ public class StackUnwinderTest extends AbstractGhidraHeadedDebuggerTest {
 		UnwindAnalysis ua = new UnwindAnalysis(program);
 
 		UnwindInfo infoAtEntry = ua.computeUnwindInfo(entry, monitor);
-		assertEquals(
+		assertEquals(new UnwindInfo(function, 0L, 4L, stack(0), -1,
-			new UnwindInfo(function, 0L, 4L, stack(0), Map.of(), new StackUnwindWarningSet(), null),
+			Map.of(), new StackUnwindWarningSet(), null),
 			infoAtEntry);
 
 		UnwindInfo infoAtBody = ua.computeUnwindInfo(bodyInstr, monitor);
 		DataType ptr2Undef = new PointerDataType(DataType.DEFAULT, program.getDataTypeManager());
-		assertEquals(new UnwindInfo(function, -20L, 4L, stack(0),
+		assertEquals(new UnwindInfo(function, -20L, 4L, stack(0), -1,
 			Map.of(register("EBP"), stack(-4)),
 			new StackUnwindWarningSet(new UnexpectedTargetTypeStackUnwindWarning(ptr2Undef)), null),
 			infoAtBody);
 	}
 
+	@Test
+	public void testComputeUnwindInfoWithArmBx() throws Throwable {
+		addPlugin(tool, CodeBrowserPlugin.class);
+		addPlugin(tool, AutoAnalysisPlugin.class);
+		addPlugin(tool, DecompilePlugin.class);
+
+		Function function = createInfiniteRecursionProgramArm();
+		openAndAnalyze(function);
+		Address entry = function.getEntryPoint();
+
+		UnwindAnalysis ua = new UnwindAnalysis(program);
+
+		UnwindInfo infoAtEntry = ua.computeUnwindInfo(entry, monitor);
+		assertEquals(new UnwindInfo(function, 0L, 0L, register("lr").getAddress(), 0xfffffffeL,
+			Map.of(), new StackUnwindWarningSet(
+				new UnspecifiedConventionStackUnwindWarning(function),
+				new UnknownPurgeStackUnwindWarning(function)),
+			null),
+			infoAtEntry);
+
+		UnwindInfo infoAtBody = ua.computeUnwindInfo(bodyInstr, monitor);
+		assertEquals(new UnwindInfo(function, -4L, 0L, stack(-4), 0xfffffffeL,
+			Map.of(), new StackUnwindWarningSet(
+				new UnspecifiedConventionStackUnwindWarning(function),
+				new UnknownPurgeStackUnwindWarning(function)),
+			null),
+			infoAtBody);
+	}
+
 	@Test
 	public void testUnwindTopFrameX86_32() throws Throwable {
 		addPlugin(tool, CodeBrowserPlugin.class);
@@ -814,6 +900,95 @@ public class StackUnwinderTest extends AbstractGhidraHeadedDebuggerTest {
 		assertEquals(BigInteger.valueOf(34), retVal.toBigInteger(false));
 	}
 
+	@Test
+	public void testUnwindRecursiveArmThumb() throws Throwable {
+		addPlugin(tool, CodeBrowserPlugin.class);
+		addPlugin(tool, DebuggerListingPlugin.class);
+		addPlugin(tool, DisassemblerPlugin.class);
+		addPlugin(tool, AutoAnalysisPlugin.class);
+		addPlugin(tool, DecompilePlugin.class);
+		DebuggerEmulationService emuService = addPlugin(tool, DebuggerEmulationServicePlugin.class);
+
+		Function function = createInfiniteRecursionProgramArm();
+		openAndAnalyze(function);
+		Address entry = function.getEntryPoint();
+
+		useTrace(ProgramEmulationUtils.launchEmulationTrace(program, entry, this));
+		tb.trace.release(this);
+		TraceThread thread = Unique.assertOne(tb.trace.getThreadManager().getAllThreads());
+		traceManager.openTrace(tb.trace);
+		traceManager.activateThread(thread);
+		waitForSwing();
+
+		DebuggerCoordinates atSetup = traceManager.getCurrent();
+		StackUnwinder unwinder = new StackUnwinder(tool, atSetup.getPlatform());
+
+		TraceMemorySpace regs = tb.trace.getMemoryManager().getMemoryRegisterSpace(thread, false);
+		Register sp = program.getCompilerSpec().getStackPointer();
+		long spAtSetup = regs.getValue(0, sp).getUnsignedValue().longValueExact();
+
+		TraceBreakpoint bptUnwind;
+		try (Transaction tx = tb.startTransaction()) {
+			bptUnwind = tb.trace.getBreakpointManager()
+					.addBreakpoint("Breakpoints[0]", Lifespan.nowOn(0), entry, Set.of(),
+						Set.of(TraceBreakpointKind.SW_EXECUTE), true, "unwind stack");
+			bptUnwind.setEmuSleigh("""
+					if (%s >= 0x%x) goto <skip>;
+					  emu_swi();
+					<skip>
+					emu_exec_decoded();
+					""".formatted(sp, spAtSetup - 0xc));
+		}
+
+		EmulationResult result = emuService.run(atSetup.getPlatform(), atSetup.getTime(), monitor,
+			Scheduler.oneThread(thread));
+		Msg.debug(this, "Broke after " + result.schedule());
+
+		traceManager.activateTime(result.schedule());
+		waitForTasks();
+		DebuggerCoordinates broke = traceManager.getCurrent();
+
+		AnalysisUnwoundFrame<WatchValue> frameBroke = unwinder.start(broke, monitor);
+		assertEquals(tb.addr(0x00004ff0), frameBroke.getStackPointer());
+		assertEquals(tb.addr(0x00004ff0), frameBroke.getBasePointer());
+		assertEquals(tb.addr(0x00400000), frameBroke.getProgramCounter());
+
+		frameBroke = frameBroke.unwindNext(monitor); // Innermost hadn't pushed anything, yet
+		assertEquals(tb.addr(0x00004ff0), frameBroke.getStackPointer());
+		assertEquals(tb.addr(0x00004ff4), frameBroke.getBasePointer());
+		assertEquals(tb.addr(0x0040000a), frameBroke.getProgramCounter());
+
+		frameBroke = frameBroke.unwindNext(monitor);
+		assertEquals(tb.addr(0x00004ff4), frameBroke.getStackPointer());
+		assertEquals(tb.addr(0x00004ff8), frameBroke.getBasePointer());
+		assertEquals(tb.addr(0x0040000a), frameBroke.getProgramCounter());
+
+		frameBroke = frameBroke.unwindNext(monitor);
+		assertEquals(tb.addr(0x00004ff8), frameBroke.getStackPointer());
+		assertEquals(tb.addr(0x00004ffc), frameBroke.getBasePointer());
+		assertEquals(tb.addr(0x0040000a), frameBroke.getProgramCounter());
+
+		frameBroke = frameBroke.unwindNext(monitor);
+		assertEquals(tb.addr(0x00004ffc), frameBroke.getStackPointer());
+		assertEquals(tb.addr(0x00005000), frameBroke.getBasePointer());
+		assertEquals(tb.addr(0x0040000a), frameBroke.getProgramCounter());
+
+		frameBroke = frameBroke.unwindNext(monitor);
+		assertEquals(tb.addr(0x00005000), frameBroke.getStackPointer());
+		assertNull(frameBroke.getBasePointer());
+		assertEquals(tb.addr(0x00000000), frameBroke.getProgramCounter());
+
+		assertEquals(5, frameBroke.getLevel());
+
+		try {
+			frameBroke.unwindNext(monitor);
+			fail();
+		}
+		catch (NoSuchElementException e) {
+			// pass
+		}
+	}
+
 	@Test
 	public void testCreateFramesAtEntryX86_32() throws Throwable {
 		addPlugin(tool, CodeBrowserPlugin.class);