diff --git a/rt/gc/RiGc.v3 b/rt/gc/RiGc.v3
index 0d4f030a0..7bfa5a1d6 100644
--- a/rt/gc/RiGc.v3
+++ b/rt/gc/RiGc.v3
@@ -152,6 +152,27 @@ component RiGc {
 		System.error("GcError", "Invalid object header");
 		return 0;
 	}
+	// scan references in a frame and return the size in bytes
+	def scanStackFrame(sp: Pointer, stackMap: int) -> int {
+		if ((stackMap & 0x80000) != 0) {
+			// extended entry
+			var vmap_p = CiRuntime.GC_EXTMAPS + (RiGc.INT_SIZE * (stackMap & 0x7FFFF));
+			return scanExtMap(vmap_p, sp);
+		} else {
+			// normal entry
+			return scanRefMap(stackMap, sp);
+		}
+	}
+	def stackmapSize(stackMap: int) -> int {
+		if ((stackMap & 0x80000) != 0) {
+			// extended entry
+			var vmap_p = CiRuntime.GC_EXTMAPS + (RiGc.INT_SIZE * (stackMap & 0x7FFFF));
+			return extmapSize(vmap_p);
+		} else {
+			// normal entry
+			return refmapSize(stackMap);
+		}
+	}
 	// scan the references at the given start address, returning the size
 	def scanRefMap(v: int, start: Pointer) -> int {
 		var vmap = v;
diff --git a/rt/native/NativeStackScanner.v3 b/rt/native/NativeStackScanner.v3
index 56d644b8f..a585dda5f 100644
--- a/rt/native/NativeStackScanner.v3
+++ b/rt/native/NativeStackScanner.v3
@@ -43,7 +43,8 @@ component NativeStackScanner {
 				}
 				return;
 			}
-			var frameSize = scanStackFrame(sp, stackmapEntry);
+			var stackMap = stackmapEntry.load<int>() >>> RiTables.PAGE_SHIFT;
+			var frameSize = RiGc.scanStackFrame(sp, stackMap);
 			if (RiGc.debug && frameSize != frameWords * RiGc.REF_SIZE) {
 				D.puts("\n\n!GcError: mismatch between source frame size ")
 				 .puti(frameWords * RiGc.REF_SIZE)
@@ -56,16 +57,4 @@ component NativeStackScanner {
 			ip = t.0; sp = t.1;
 		}
 	}
-	// scan a single stack frame
-	def scanStackFrame(sp: Pointer, stackmapEntry: Pointer) -> int {
-		var stackMap = stackmapEntry.load<int>() >>> RiTables.PAGE_SHIFT;
-		if ((stackMap & 0x80000) != 0) {
-			// extended entry
-			var vmap_p = CiRuntime.GC_EXTMAPS + (RiGc.INT_SIZE * (stackMap & 0x7FFFF));
-			return RiGc.scanExtMap(vmap_p, sp);
-		} else {
-			// normal entry
-			return RiGc.scanRefMap(stackMap, sp);
-		}
-	}
 }
diff --git a/rt/native/NativeStackWalker.v3 b/rt/native/NativeStackWalker.v3
new file mode 100644
index 000000000..e9470e450
--- /dev/null
+++ b/rt/native/NativeStackWalker.v3
@@ -0,0 +1,44 @@
+// Copyright 2019 Google Inc. All rights reserved.
+// See LICENSE for details of Apache 2.0 license.
+
+// Encapsulates logic relating to walking the stack to be exposed to (power user) applications.
+component NativeStackWalker {
+	def iterateFrames(i: Pointer, s: Pointer, callback: (Pointer, Pointer, RiUserCode, int) -> bool) {
+		var ip = i, sp = s;
+		while (true) {
+			// Try looking up a GC stackmap entry first.
+			var stackmapEntry = RiTables.exactMatch(RiTables.searchTable(CiRuntime.GC_STACKMAP_PAGES,
+                        								CiRuntime.GC_STACKMAP_TABLE, ip));
+			if (stackmapEntry != Pointer.NULL) { // found a (GC) stackmap entry.
+				var stackMap = stackmapEntry.load<int>() >>> RiTables.PAGE_SHIFT;
+				var frameSize = RiGc.stackmapSize(stackMap);
+				callback(ip, sp, null, frameSize);
+				var t = RiOs.callerFrame(ip, sp, frameSize / RiGc.REF_SIZE);
+				ip = t.0; sp = t.1;
+				continue;
+			}
+
+			//  
+			/* TODO: try using a source entry if no GC entry.
+			var sourceEntry = RiTables.findSource(ip);
+			if (sourceEntry != Pointer.NULL) { // found a source entry.
+				var frameWords = printSourceEntry(ip, sourceEntry);
+				var t = RiOs.callerFrame(ip, sp, frameWords);
+				ip = t.0; sp = t.1;
+				continue;
+			}
+			*/
+
+			// Search for user code.
+			if (RiRuntime.userCodeList != null) {
+				var userCode = RiRuntime.findUserCode(ip);
+				if (userCode == null) return; // no user code found
+				callback(ip, sp, userCode, 0);
+				var t = userCode.nextFrame(ip, sp);
+				ip = t.0; sp = t.1;
+				continue;
+			}
+			return; // unknown frame; assume finished
+		}
+	}
+}
\ No newline at end of file
diff --git a/test/rt/x86-64-darwin/stackwalk0.v3 b/test/rt/x86-64-darwin/stackwalk0.v3
new file mode 100644
index 000000000..14d9813a4
--- /dev/null
+++ b/test/rt/x86-64-darwin/stackwalk0.v3
@@ -0,0 +1,14 @@
+def main() -> int {
+	foo(Array<byte>.new(4));
+	foo(Array<int>.new(8));
+	return 33;
+}
+def foo<T>(x: Array<T>) -> int {
+	NativeStackWalker.iterateFrames(CiRuntime.callerIp() + -1, CiRuntime.callerSp(), printFrame);
+	return x.length;
+}
+def printFrame(ip: Pointer, sp: Pointer, code: RiUserCode, size: int) -> bool {
+	if (code == null) System.puts("--{virgil frame}--\n");
+	else System.puts("--{user frame}--\n");
+	return true;
+}
diff --git a/test/rt/x86-64-darwin/stackwalk0.v3.out b/test/rt/x86-64-darwin/stackwalk0.v3.out
new file mode 100644
index 000000000..27b11dbac
--- /dev/null
+++ b/test/rt/x86-64-darwin/stackwalk0.v3.out
@@ -0,0 +1,2 @@
+--{virgil frame}--
+--{virgil frame}--
diff --git a/test/rt/x86-64-linux/stackwalk0.v3 b/test/rt/x86-64-linux/stackwalk0.v3
new file mode 100644
index 000000000..14d9813a4
--- /dev/null
+++ b/test/rt/x86-64-linux/stackwalk0.v3
@@ -0,0 +1,14 @@
+def main() -> int {
+	foo(Array<byte>.new(4));
+	foo(Array<int>.new(8));
+	return 33;
+}
+def foo<T>(x: Array<T>) -> int {
+	NativeStackWalker.iterateFrames(CiRuntime.callerIp() + -1, CiRuntime.callerSp(), printFrame);
+	return x.length;
+}
+def printFrame(ip: Pointer, sp: Pointer, code: RiUserCode, size: int) -> bool {
+	if (code == null) System.puts("--{virgil frame}--\n");
+	else System.puts("--{user frame}--\n");
+	return true;
+}
diff --git a/test/rt/x86-64-linux/stackwalk0.v3.out b/test/rt/x86-64-linux/stackwalk0.v3.out
new file mode 100644
index 000000000..27b11dbac
--- /dev/null
+++ b/test/rt/x86-64-linux/stackwalk0.v3.out
@@ -0,0 +1,2 @@
+--{virgil frame}--
+--{virgil frame}--
diff --git a/test/rt/x86-64-linux/stackwalk1.v3 b/test/rt/x86-64-linux/stackwalk1.v3
new file mode 100644
index 000000000..a8c73ce8d
--- /dev/null
+++ b/test/rt/x86-64-linux/stackwalk1.v3
@@ -0,0 +1,13 @@
+def main() -> int {
+	foo(Array<byte>.new(4));
+	foo(Array<int>.new(8));
+	return 33;
+}
+def foo<T>(x: Array<T>) -> int {
+	NativeStackWalker.iterateFrames(CiRuntime.callerIp() + -1, CiRuntime.callerSp(), printFrame);
+	return x.length;
+}
+def printFrame(ip: Pointer, sp: Pointer, code: RiUserCode, size: int) -> bool {
+	System.puts("--{user frame}--\n");
+	return true;
+}
diff --git a/test/rt/x86-darwin/stackwalk0.v3 b/test/rt/x86-darwin/stackwalk0.v3
new file mode 100644
index 000000000..14d9813a4
--- /dev/null
+++ b/test/rt/x86-darwin/stackwalk0.v3
@@ -0,0 +1,14 @@
+def main() -> int {
+	foo(Array<byte>.new(4));
+	foo(Array<int>.new(8));
+	return 33;
+}
+def foo<T>(x: Array<T>) -> int {
+	NativeStackWalker.iterateFrames(CiRuntime.callerIp() + -1, CiRuntime.callerSp(), printFrame);
+	return x.length;
+}
+def printFrame(ip: Pointer, sp: Pointer, code: RiUserCode, size: int) -> bool {
+	if (code == null) System.puts("--{virgil frame}--\n");
+	else System.puts("--{user frame}--\n");
+	return true;
+}
diff --git a/test/rt/x86-darwin/stackwalk0.v3.out b/test/rt/x86-darwin/stackwalk0.v3.out
new file mode 100644
index 000000000..27b11dbac
--- /dev/null
+++ b/test/rt/x86-darwin/stackwalk0.v3.out
@@ -0,0 +1,2 @@
+--{virgil frame}--
+--{virgil frame}--
diff --git a/test/rt/x86-linux/stackwalk0.v3 b/test/rt/x86-linux/stackwalk0.v3
new file mode 100644
index 000000000..14d9813a4
--- /dev/null
+++ b/test/rt/x86-linux/stackwalk0.v3
@@ -0,0 +1,14 @@
+def main() -> int {
+	foo(Array<byte>.new(4));
+	foo(Array<int>.new(8));
+	return 33;
+}
+def foo<T>(x: Array<T>) -> int {
+	NativeStackWalker.iterateFrames(CiRuntime.callerIp() + -1, CiRuntime.callerSp(), printFrame);
+	return x.length;
+}
+def printFrame(ip: Pointer, sp: Pointer, code: RiUserCode, size: int) -> bool {
+	if (code == null) System.puts("--{virgil frame}--\n");
+	else System.puts("--{user frame}--\n");
+	return true;
+}
diff --git a/test/rt/x86-linux/stackwalk0.v3.out b/test/rt/x86-linux/stackwalk0.v3.out
new file mode 100644
index 000000000..27b11dbac
--- /dev/null
+++ b/test/rt/x86-linux/stackwalk0.v3.out
@@ -0,0 +1,2 @@
+--{virgil frame}--
+--{virgil frame}--