commit 1b43afaf5f93e3fd2c7198054c038268bb671149
Author: Andrew Cagney <cagney@gnu.org>
Date:   Tue Apr 19 10:38:01 2016 -0400

    When cloning a unw_cursor_t also clone the jobject ref.

diff --git a/frysk-sys/lib/unwind/jni/UnwindH.hxx b/frysk-sys/lib/unwind/jni/UnwindH.hxx
index 4d72423..6c16f39 100644
--- a/frysk-sys/lib/unwind/jni/UnwindH.hxx
+++ b/frysk-sys/lib/unwind/jni/UnwindH.hxx
@@ -64,9 +64,12 @@
 using namespace java::lang;
 using namespace lib::unwind;
 
+#define CURSOR_MAGIC 0xfab
+
 struct jni_cursor {
   unw_cursor_t cursor;
   jobject addressSpace;
+  int magic;
 };
 
 #define UNW_PROC_INFO ((unw_proc_info_t*)unwProcInfo)
@@ -248,27 +251,56 @@ jlong
 TARGET::createCursor(jnixx::env env,
 		     AddressSpace addressSpace,
 		     jlong unwAddressSpace) {
-  logf(FINE, "createCursor from address-space %lx", (long) UNW_ADDRESS_SPACE);
   jni_cursor *cursor = new(jni_cursor);
+  logf(FINE, "createCursor %p using address-space %p arg %llx",
+       cursor, UNW_ADDRESS_SPACE, (long long) addressSpace._object);
   // XXX: Need to zero out the cursor, as unw_init_remote doesn't seem
   // to do it.
   memset(cursor, 0, sizeof(jni_cursor));
   // Make global as object is used across JNI calls
+  cursor->magic = CURSOR_MAGIC;
   cursor->addressSpace = env.NewGlobalRef(addressSpace._object);
   unw_init_remote(&cursor->cursor, UNW_ADDRESS_SPACE, cursor->addressSpace);
-  logf(FINE, "createCursor at %p", cursor);
+  logf(FINE, "createCursor %p global address-space ref %llx",
+       cursor, (long long) cursor->addressSpace);
   return (jlong)cursor;
 }
 
 void
 TARGET::destroyCursor(jnixx::env env, jlong unwCursor) {
   jni_cursor *cursor = (jni_cursor*)unwCursor;
-  logf(FINE, "destroyCursor at %p", cursor);
+  logf(FINE, "destroyCursor %p", cursor);
+  if (cursor->magic != CURSOR_MAGIC) {
+    fprintf(stderr, "\n%s: cursor %p has bad CURSOR_MAGIC number\n",
+	    __func__, cursor);
+    abort();
+  }
+  logf(FINE, "destroyCursor %p deleting global address-space ref %llx",
+       cursor, (long long) cursor->addressSpace);
   env.DeleteGlobalRef(cursor->addressSpace);
   ::free(cursor);
 }
 
 jlong
+TARGET::copyCursor(jnixx::env env, jlong unwCursor) {
+  jni_cursor *original = (jni_cursor*) unwCursor;
+  logf(FINE, "copyCursor %p", original);
+  if (original->magic != CURSOR_MAGIC) {
+    fprintf(stderr, "\n%s: cursor %p has bad CURSOR_MAGIC number\n",
+	    __func__, original);
+    abort();
+  }
+  jni_cursor *copy = new(jni_cursor);
+  // Create a local copy of the unwind cursor
+  ::memcpy(&copy->cursor, &original->cursor, sizeof(original->cursor));
+  copy->magic = CURSOR_MAGIC;
+  copy->addressSpace = env.NewGlobalRef(original->addressSpace);
+  logf(FINE, "copyCursor %p to %p global address-space ref %llx",
+       original, copy, (long long) copy->addressSpace);
+  return (jlong) copy;
+}
+
+jlong
 TARGET::createAddressSpace(jnixx::env env, ByteOrder byteOrder) {
   logf(FINE, "createAddressSpace, byteOrder %d",
        (int) byteOrder.hashCode(env));
@@ -304,13 +336,13 @@ TARGET::setCachingPolicy(jnixx::env env, jlong unwAddressSpace,
 
 jint
 TARGET::isSignalFrame(jnixx::env env, jlong unwCursor) {
-  logf(FINE, "isSignalFrame");
+  logf(FINE, "isSignalFrame: %p", UNW_CURSOR);
   return unw_is_signal_frame(UNW_CURSOR);
 }
 
 jint
 TARGET::step(jnixx::env env, jlong unwCursor) {
-  logf(FINE, "step cursor: %lx", (long) UNW_CURSOR);
+  logf(FINE, "step cursor: %p", UNW_CURSOR);
   return unw_step(UNW_CURSOR);
 }
 
@@ -329,8 +361,8 @@ TARGET::getRegister(jnixx::env env, jlong unwCursor,
 		    Number num, jlong offset, jint length,
 		    jnixx::jbyteArray jbytes, jint start) {
   int regNum = num.intValue(env);
-  logf(FINE, "getRegister %d from %lx, offset %ld length %d start %d",
-       regNum, (long)UNW_CURSOR, (long) offset, (int)length, (int)start);
+  logf(FINE, "getRegister: %d from cursor: %p offset: %ld length: %d start: %d",
+       regNum, UNW_CURSOR, (long) offset, (int)length, (int)start);
   int status;
   union {
     unw_word_t w;
@@ -423,9 +455,11 @@ TARGET::getCFA(jnixx::env env, jlong unwCursor) {
   // This is wasteful, but there is no generic UNW_REG_CFA.
   // So just unwind and return the stack pointer.
 #define FRYSK_UNW_REG_CFA UNW_REG_SP
-  unw_cursor_t copy;
+  // Need to copy everything including magic and the addressSpace
+  // handle.
+  jni_cursor copy;
   memcpy(&copy, UNW_CURSOR, sizeof (copy));
-  if (unw_step(&copy) < 0)
+  if (unw_step(&copy.cursor) < 0)
     return 0;
   unwCursor = (jlong) &copy;
 #endif
@@ -446,17 +480,6 @@ TARGET::getContext(jnixx::env env, jlong context) {
 }
 
 jlong
-TARGET::copyCursor(jnixx::env env, jlong unwCursor) {
-  ::unw_cursor_t *nativeCursor
-    = (::unw_cursor_t*) ::malloc(sizeof(::unw_cursor_t));
-  // Create a local copy of the unwind cursor
-  ::memcpy(nativeCursor, UNW_CURSOR, sizeof(*UNW_CURSOR));
-  logf(FINE, "copyCursor %lx to %lx", (long) UNW_CURSOR,
-       (long) nativeCursor);
-  return (jlong) nativeCursor;
-}
-
-jlong
 TARGET::getProcInfo(jnixx::env env, jlong unwCursor) {
   logf(FINE, "getProcInfo cursor: %lx", (long) UNW_CURSOR);
   unw_proc_info_t *procInfo
@@ -510,8 +533,9 @@ image_access_mem(unw_addr_space_t as, unw_word_t addr,
 		 unw_word_t *val, int write, void *arg) {
   struct image *image = (struct image*) arg;
   if (image->magic != IMAGE_MAGIC) {
-    fprintf(stderr, "%s: bad magic number\n", __func__);
-    return -UNW_EINVAL;
+    fprintf(stderr, "%s: image %p has bad IMAGE_MAGIC number\n",
+	    __func__, image);
+    abort();
   }
   // Writing is not supported
   if (write)