diff --git a/node.gyp b/node.gyp
index bbded80895..64a4ab62ff 100644
--- a/node.gyp
+++ b/node.gyp
@@ -169,13 +169,9 @@
           #
           'sources': [
             'src/node_dtrace.cc',
-            'src/node_dtrace_provider.cc'
+            'src/node_dtrace_provider.cc',
+            'src/node_dtrace_ustack.cc',
           ],
-          'conditions': [ [
-            'target_arch=="ia32"', {
-              'sources': [ 'src/node_dtrace_ustack.cc' ]
-            }
-          ] ],
         } ],
         [ 'node_use_systemtap=="true"', {
           'defines': [ 'HAVE_SYSTEMTAP=1', 'STAP_SDT_V1=1' ],
@@ -424,7 +420,7 @@
       'target_name': 'node_dtrace_ustack',
       'type': 'none',
       'conditions': [
-        [ 'node_use_dtrace=="true" and target_arch=="ia32"', {
+        [ 'node_use_dtrace=="true"', {
           'actions': [
             {
               'action_name': 'node_dtrace_ustack_constants',
@@ -449,9 +445,19 @@
               'outputs': [
                 '<(PRODUCT_DIR)/obj.target/node/src/node_dtrace_ustack.o'
               ],
-              'action': [
-                'dtrace', '-32', '-I<(SHARED_INTERMEDIATE_DIR)', '-Isrc',
-                '-C', '-G', '-s', 'src/v8ustack.d', '-o', '<@(_outputs)',
+              'conditions': [
+                [ 'target_arch=="ia32"', {
+                  'action': [
+                    'dtrace', '-32', '-I<(SHARED_INTERMEDIATE_DIR)', '-Isrc',
+                    '-C', '-G', '-s', 'src/v8ustack.d', '-o', '<@(_outputs)',
+                  ]
+                } ],
+                [ 'target_arch=="x64"', {
+                  'action': [
+                    'dtrace', '-64', '-I<(SHARED_INTERMEDIATE_DIR)', '-Isrc',
+                    '-C', '-G', '-s', 'src/v8ustack.d', '-o', '<@(_outputs)',
+                  ]
+                } ],
               ]
             }
           ]
diff --git a/src/v8abbr.h b/src/v8abbr.h
index 9bc425eb84..95ddb6a661 100644
--- a/src/v8abbr.h
+++ b/src/v8abbr.h
@@ -7,9 +7,9 @@
 #define V8_ABBR_H
 
 /* Frame pointer offsets */
-#define V8_OFF_FP_FUNC              ((uint32_t)V8DBG_OFF_FP_FUNCTION)
-#define V8_OFF_FP_CONTEXT           ((uint32_t)V8DBG_OFF_FP_CONTEXT)
-#define V8_OFF_FP_MARKER            ((uint32_t)V8DBG_OFF_FP_MARKER)
+#define V8_OFF_FP_FUNC              V8DBG_OFF_FP_FUNCTION
+#define V8_OFF_FP_CONTEXT           V8DBG_OFF_FP_CONTEXT
+#define V8_OFF_FP_MARKER            V8DBG_OFF_FP_MARKER
 
 /* Stack frame types */
 #define V8_FT_ENTRY                 V8DBG_FRAMETYPE_ENTRYFRAME
@@ -22,9 +22,9 @@
 #define V8_FT_ADAPTOR               V8DBG_FRAMETYPE_ARGUMENTSADAPTORFRAME
 
 /* Identification masks and tags */
-#define V8_SmiTagMask               V8DBG_SMITAGMASK
-#define V8_SmiTag                   V8DBG_SMITAG
-#define V8_SmiValueShift            V8_SmiTagMask
+#define V8_SmiTagMask               (V8DBG_SMITAGMASK)
+#define V8_SmiTag                   (V8DBG_SMITAG)
+#define V8_SmiValueShift            (V8DBG_SMISHIFTSIZE + V8DBG_SMITAGMASK)
 
 #define V8_HeapObjectTagMask        V8DBG_HEAPOBJECTTAGMASK
 #define V8_HeapObjectTag            V8DBG_HEAPOBJECTTAG
@@ -45,7 +45,7 @@
 #define V8_IT_CODE                  V8DBG_TYPE_CODE__CODE_TYPE
 
 /* Node-specific offsets */
-#define NODE_OFF_EXTSTR_DATA        0x4
+#define NODE_OFF_EXTSTR_DATA        sizeof(void*)
 
 /* Heap class->field offsets */
 #define V8_OFF_HEAP(off)            ((off) - 1)
diff --git a/src/v8ustack.d b/src/v8ustack.d
index 8a25ee01f3..f55148cfda 100644
--- a/src/v8ustack.d
+++ b/src/v8ustack.d
@@ -14,13 +14,13 @@
 #include <v8abbr.h>
 
 /*
- * V8 represents small integers (SMI) using the upper 31 bits of a 32-bit
+ * V8 represents small integers (SMI) using the upper 31 bits of a 32/64-bit
  * value.  To extract the actual integer value, we must shift it over.
  */
 #define IS_SMI(value) \
     ((value & V8_SmiTagMask) == V8_SmiTag)
 #define SMI_VALUE(value) \
-    ((uint32_t)(value) >> V8_SmiValueShift)
+    ((uint32_t) ((value) >> V8_SmiValueShift))
 
 /*
  * Heap objects usually start off with a Map pointer, itself another heap
@@ -34,7 +34,8 @@
 /*
  * Determine the encoding and representation of a V8 string.
  */
-#define V8_TYPE_STRING(type) (((type) & V8_IsNotStringMask) == V8_StringTag)
+#define V8_TYPE_STRING(type) \
+    (((type) & V8_IsNotStringMask) == V8_StringTag)
 
 #define V8_STRENC_ASCII(type) \
     (((type) & V8_StringEncodingMask) == V8_AsciiStringTag)
@@ -63,19 +64,56 @@
  */
 #define COPYIN_UINT8(addr) (*(uint8_t*) copyin((addr), sizeof(uint8_t)))
 #define COPYIN_UINT32(addr) (*(uint32_t*) copyin((addr), sizeof(uint32_t)))
+#define COPYIN_UINT64(addr) (*(uint64_t*) copyin((addr), sizeof(uint64_t)))
+
+#if defined(__i386)
+# define COPYIN_PTR(addr) COPYIN_UINT32(addr)
+# define off_t uint32_t
+# define APPEND_PTR(p) APPEND_PTR_32(p)
+#else
+# define COPYIN_PTR(addr) COPYIN_UINT64(addr)
+# define off_t uint64_t
+# define APPEND_PTR(p) APPEND_PTR_64(p)
+#endif
 
 #define APPEND_CHR(c) (this->buf[this->off++] = (c))
+#define APPEND_CHR4(s0, s1, s2, s3) \
+    APPEND_CHR(s0); \
+    APPEND_CHR(s1); \
+    APPEND_CHR(s2); \
+    APPEND_CHR(s3);
+#define APPEND_CHR8(s0, s1, s2, s3, s4, s5, s6, s7) \
+    APPEND_CHR4(s0, s1, s2, s3) \
+    APPEND_CHR4(s4, s5, s6, s7)
 
 #define APPEND_DGT(i, d) \
     (((i) / (d)) ? APPEND_CHR('0' + ((i)/(d) % 10)) : 0)
 
 #define APPEND_NUM(i) \
+    APPEND_DGT((i), 100000); \
     APPEND_DGT((i), 10000); \
     APPEND_DGT((i), 1000); \
     APPEND_DGT((i), 100); \
     APPEND_DGT((i), 10); \
     APPEND_DGT((i), 1);
 
+#define APPEND_HEX(d) \
+    APPEND_CHR((d) < 10 ? '0' + (d) : 'a' - 10 + (d))
+
+#define APPEND_PTR_32(p) \
+    APPEND_HEX((p >> 28) & 0xf); \
+    APPEND_HEX((p >> 24) & 0xf); \
+    APPEND_HEX((p >> 20) & 0xf); \
+    APPEND_HEX((p >> 16) & 0xf); \
+    APPEND_HEX((p >> 12) & 0xf); \
+    APPEND_HEX((p >> 8) & 0xf); \
+    APPEND_HEX((p >> 4) & 0xf); \
+    APPEND_HEX((p) & 0xf);
+
+#define APPEND_PTR_64(p) \
+    APPEND_PTR_32(p >> 32) \
+    APPEND_PTR_32(p)
+
 /*
  * The following macros are used to output ASCII SeqStrings, ConsStrings, and
  * Node.js ExternalStrings.  To represent each string, we use three fields:
@@ -99,8 +137,8 @@
  * Load "len" and "attrs" for the given "str".
  */
 #define LOAD_STRFIELDS(str, len, attrs) \
-    len = SMI_VALUE(COPYIN_UINT32(str + V8_OFF_STR_LENGTH)); \
-    this->map = V8_MAP_PTR(COPYIN_UINT32(str + V8_OFF_HEAPOBJ_MAP)); \
+    len = SMI_VALUE(COPYIN_PTR(str + V8_OFF_STR_LENGTH)); \
+    this->map = V8_MAP_PTR(COPYIN_PTR(str + V8_OFF_HEAPOBJ_MAP)); \
     attrs = COPYIN_UINT8(this->map + V8_OFF_MAP_ATTRS);
 
 /*
@@ -123,8 +161,8 @@
     dtrace:helper:ustack: \
     /!this->done && len > 0 && ASCII_EXTSTR(attrs)/ \
     { \
-      this->resource = COPYIN_UINT32(str + V8_OFF_EXTSTR_RSRC); \
-      this->dataptr = COPYIN_UINT32(this->resource + NODE_OFF_EXTSTR_DATA); \
+      this->resource = COPYIN_PTR(str + V8_OFF_EXTSTR_RSRC); \
+      this->dataptr = COPYIN_PTR(this->resource + NODE_OFF_EXTSTR_DATA); \
       copyinto(this->dataptr, len, this->buf + this->off); \
       this->off += len; \
     }
@@ -146,7 +184,7 @@
  *              s0                       s7
  *            /    \                  / \
  *           /      \                /       \           <--  2nd expansion
- *          /        \              / \
+ *          /        \              /         \
  *        s1          s4          s8           s11
  *       /  \        /  \        /  \          /  \      <--  3rd expansion
  *     s2    s3    s5    s6    s9    s10    s12    s13
@@ -162,17 +200,17 @@
     dtrace:helper:ustack: \
     /!this->done/ \
     { \
-      this->s0str = this->s1str = this->s2str = 0; \
-      this->s3str = this->s4str = this->s5str = 0; \
-      this->s6str = this->s7str = this->s8str = 0; \
-      this->s9str = this->s10str = this->s11str = 0; \
-      this->s12str = this->s13str = 0; \
+      this->s0str = this->s1str = this->s2str = (off_t) 0; \
+      this->s3str = this->s4str = this->s5str = (off_t) 0; \
+      this->s6str = this->s7str = this->s8str = (off_t) 0; \
+      this->s9str = this->s10str = this->s11str = (off_t) 0; \
+      this->s12str = this->s13str = (off_t) 0; \
       \
-      this->s0len = this->s1len = this->s2len = 0; \
-      this->s3len = this->s4len = this->s5len = 0; \
-      this->s6len = this->s7len = this->s8len = 0; \
-      this->s9len = this->s10len = this->s11len = 0; \
-      this->s12len = this->s13len = 0; \
+      this->s0len = this->s1len = this->s2len = (off_t) 0; \
+      this->s3len = this->s4len = this->s5len = (off_t) 0; \
+      this->s6len = this->s7len = this->s8len = (off_t) 0; \
+      this->s9len = this->s10len = this->s11len = (off_t) 0; \
+      this->s12len = this->s13len = (off_t) 0; \
       \
       this->s0attrs = this->s1attrs = this->s2attrs = 0; \
       this->s3attrs = this->s4attrs = this->s5attrs = 0; \
@@ -192,10 +230,10 @@
     { \
       len = 0; \
       \
-      s1s = COPYIN_UINT32(str + V8_OFF_CONSSTR_CAR); \
+      s1s = COPYIN_PTR(str + V8_OFF_CONSSTR_CAR); \
       LOAD_STRFIELDS(s1s, s1l, s1a) \
       \
-      s2s = COPYIN_UINT32(str + V8_OFF_CONSSTR_CDR); \
+      s2s = COPYIN_PTR(str + V8_OFF_CONSSTR_CDR); \
       LOAD_STRFIELDS(s2s, s2l, s2a) \
     }
 
@@ -268,21 +306,21 @@ dtrace:helper:ustack:
   this->done = 0;
 
   /* program state */
-  this->ctx = 0;
-  this->marker = 0;
-  this->func = 0;
-  this->shared = 0;
-  this->map = 0;
+  this->ctx = (off_t) 0;
+  this->marker = (off_t) 0;
+  this->func = (off_t) 0;
+  this->shared = (off_t) 0;
+  this->map = (off_t) 0;
   this->attrs = 0;
-  this->funcnamestr = 0;
+  this->funcnamestr = (off_t) 0;
   this->funcnamelen = 0;
   this->funcnameattrs = 0;
-  this->script = 0;
-  this->scriptnamestr = 0;
+  this->script = (off_t) 0;
+  this->scriptnamestr = (off_t) 0;
   this->scriptnamelen = 0;
   this->scriptnameattrs = 0;
   this->position = 0;
-  this->line_ends = 0;
+  this->line_ends = (off_t) 0;
   this->le_attrs = 0;
 
   /* binary search fields */
@@ -297,27 +335,15 @@ dtrace:helper:ustack:
  */
 dtrace:helper:ustack:
 {
-  this->ctx = COPYIN_UINT32(this->fp + V8_OFF_FP_CONTEXT);
+  this->ctx = COPYIN_PTR(this->fp + V8_OFF_FP_CONTEXT);
 }
 
 dtrace:helper:ustack:
 /IS_SMI(this->ctx) && SMI_VALUE(this->ctx) == V8_FT_ADAPTOR/
 {
   this->done = 1;
-  APPEND_CHR('<');
-  APPEND_CHR('<');
-  APPEND_CHR(' ');
-  APPEND_CHR('a');
-  APPEND_CHR('d');
-  APPEND_CHR('a');
-  APPEND_CHR('p');
-  APPEND_CHR('t');
-  APPEND_CHR('o');
-  APPEND_CHR('r');
-  APPEND_CHR(' ');
-  APPEND_CHR('>');
-  APPEND_CHR('>');
-  APPEND_CHR('\0');
+  APPEND_CHR8('<','<',' ','a','d','a','p','t');
+  APPEND_CHR8('o','r',' ','>','>','\0','\0','\0');
   stringof(this->buf);
 }
 
@@ -327,7 +353,7 @@ dtrace:helper:ustack:
 dtrace:helper:ustack:
 /!this->done/
 {
-  this->marker = COPYIN_UINT32(this->fp + V8_OFF_FP_MARKER);
+  this->marker = COPYIN_PTR(this->fp + V8_OFF_FP_MARKER);
 }
 
 dtrace:helper:ustack:
@@ -335,18 +361,8 @@ dtrace:helper:ustack:
  SMI_VALUE(this->marker) == V8_FT_ENTRY/
 {
   this->done = 1;
-  APPEND_CHR('<');
-  APPEND_CHR('<');
-  APPEND_CHR(' ');
-  APPEND_CHR('e');
-  APPEND_CHR('n');
-  APPEND_CHR('t');
-  APPEND_CHR('r');
-  APPEND_CHR('y');
-  APPEND_CHR(' ');
-  APPEND_CHR('>');
-  APPEND_CHR('>');
-  APPEND_CHR('\0');
+  APPEND_CHR8('<','<',' ','e','n','t','r','y');
+  APPEND_CHR4(' ','>','>','\0');
   stringof(this->buf);
 }
 
@@ -355,27 +371,9 @@ dtrace:helper:ustack:
  SMI_VALUE(this->marker) == V8_FT_ENTRYCONSTRUCT/
 {
   this->done = 1;
-  APPEND_CHR('<');
-  APPEND_CHR('<');
-  APPEND_CHR(' ');
-  APPEND_CHR('e');
-  APPEND_CHR('n');
-  APPEND_CHR('t');
-  APPEND_CHR('r');
-  APPEND_CHR('y');
-  APPEND_CHR('_');
-  APPEND_CHR('c');
-  APPEND_CHR('o');
-  APPEND_CHR('n');
-  APPEND_CHR('s');
-  APPEND_CHR('t');
-  APPEND_CHR('r');
-  APPEND_CHR('u');
-  APPEND_CHR('c');
-  APPEND_CHR('t');
-  APPEND_CHR(' ');
-  APPEND_CHR('>');
-  APPEND_CHR('>');
+  APPEND_CHR8('<','<',' ','e','n','t','r','y');
+  APPEND_CHR8('_','c','o','n','s','t','r','u');
+  APPEND_CHR4('t',' ','>','>');
   APPEND_CHR('\0');
   stringof(this->buf);
 }
@@ -385,17 +383,8 @@ dtrace:helper:ustack:
  SMI_VALUE(this->marker) == V8_FT_EXIT/
 {
   this->done = 1;
-  APPEND_CHR('<');
-  APPEND_CHR('<');
-  APPEND_CHR(' ');
-  APPEND_CHR('e');
-  APPEND_CHR('x');
-  APPEND_CHR('i');
-  APPEND_CHR('t');
-  APPEND_CHR(' ');
-  APPEND_CHR('>');
-  APPEND_CHR('>');
-  APPEND_CHR('\0');
+  APPEND_CHR8('<','<',' ','e','x','i','t',' ');
+  APPEND_CHR4('>','>','\0','\0');
   stringof(this->buf);
 }
 
@@ -404,21 +393,8 @@ dtrace:helper:ustack:
  SMI_VALUE(this->marker) == V8_FT_INTERNAL/
 {
   this->done = 1;
-  APPEND_CHR('<');
-  APPEND_CHR('<');
-  APPEND_CHR(' ');
-  APPEND_CHR('i');
-  APPEND_CHR('n');
-  APPEND_CHR('t');
-  APPEND_CHR('e');
-  APPEND_CHR('r');
-  APPEND_CHR('n');
-  APPEND_CHR('a');
-  APPEND_CHR('l');
-  APPEND_CHR(' ');
-  APPEND_CHR('>');
-  APPEND_CHR('>');
-  APPEND_CHR('\0');
+  APPEND_CHR8('<','<',' ','i','n','t','e','r');
+  APPEND_CHR8('n','a','l',' ','>','>','\0','\0');
   stringof(this->buf);
 }
 
@@ -427,24 +403,9 @@ dtrace:helper:ustack:
  SMI_VALUE(this->marker) == V8_FT_CONSTRUCT/
 {
   this->done = 1;
-  APPEND_CHR('<');
-  APPEND_CHR('<');
-  APPEND_CHR(' ');
-  APPEND_CHR('c');
-  APPEND_CHR('o');
-  APPEND_CHR('n');
-  APPEND_CHR('s');
-  APPEND_CHR('t');
-  APPEND_CHR('r');
-  APPEND_CHR('u');
-  APPEND_CHR('c');
-  APPEND_CHR('t');
-  APPEND_CHR('o');
-  APPEND_CHR('r');
-  APPEND_CHR(' ');
-  APPEND_CHR('>');
-  APPEND_CHR('>');
-  APPEND_CHR('\0');
+  APPEND_CHR8('<','<',' ','c','o','n','s','t');
+  APPEND_CHR8('r','u','c','t','o','r',' ','>');
+  APPEND_CHR4('>','\0','\0','\0');
   stringof(this->buf);
 }
 
@@ -456,8 +417,8 @@ dtrace:helper:ustack:
 dtrace:helper:ustack:
 /!this->done/
 {
-  this->func = COPYIN_UINT32(this->fp + V8_OFF_FP_FUNC);
-  this->map = V8_MAP_PTR(COPYIN_UINT32(this->func + V8_OFF_HEAPOBJ_MAP));
+  this->func = COPYIN_PTR(this->fp + V8_OFF_FP_FUNC);
+  this->map = V8_MAP_PTR(COPYIN_PTR(this->func + V8_OFF_HEAPOBJ_MAP));
   this->attrs = COPYIN_UINT8(this->map + V8_OFF_MAP_ATTRS);
 }
 
@@ -465,26 +426,9 @@ dtrace:helper:ustack:
 /!this->done && this->attrs == V8_IT_CODE/
 {
   this->done = 1;
-  APPEND_CHR('<');
-  APPEND_CHR('<');
-  APPEND_CHR(' ');
-  APPEND_CHR('i');
-  APPEND_CHR('n');
-  APPEND_CHR('t');
-  APPEND_CHR('e');
-  APPEND_CHR('r');
-  APPEND_CHR('n');
-  APPEND_CHR('a');
-  APPEND_CHR('l');
-  APPEND_CHR(' ');
-  APPEND_CHR('c');
-  APPEND_CHR('o');
-  APPEND_CHR('d');
-  APPEND_CHR('e');
-  APPEND_CHR(' ');
-  APPEND_CHR('>');
-  APPEND_CHR('>');
-  APPEND_CHR('\0');
+  APPEND_CHR8('<','<',' ','i','n','t','e','r');
+  APPEND_CHR8('n','a','l',' ','c','o','d','e');
+  APPEND_CHR4(' ','>','>','\0');
   stringof(this->buf);
 }
 
@@ -499,8 +443,8 @@ dtrace:helper:ustack:
   this->map = 0;
   this->attrs = 0;
 
-  this->shared = COPYIN_UINT32(this->func + V8_OFF_FUNC_SHARED);
-  this->funcnamestr = COPYIN_UINT32(this->shared + V8_OFF_SHARED_NAME);
+  this->shared = COPYIN_PTR(this->func + V8_OFF_FUNC_SHARED);
+  this->funcnamestr = COPYIN_PTR(this->shared + V8_OFF_SHARED_NAME);
   LOAD_STRFIELDS(this->funcnamestr, this->funcnamelen,
                  this->funcnameattrs);
 }
@@ -513,18 +457,11 @@ dtrace:helper:ustack:
    * some object then V8 will have computed an inferred name that we can
    * include in the stack trace.
    */
-  APPEND_CHR('(');
-  APPEND_CHR('a');
-  APPEND_CHR('n');
-  APPEND_CHR('o');
-  APPEND_CHR('n');
-  APPEND_CHR(')');
-  APPEND_CHR(' ');
-  APPEND_CHR('a');
+  APPEND_CHR8('(','a','n','o','n',')',' ','a');
   APPEND_CHR('s');
   APPEND_CHR(' ');
 
-  this->funcnamestr = COPYIN_UINT32(this->shared + V8_OFF_SHARED_INFERRED);
+  this->funcnamestr = COPYIN_PTR(this->shared + V8_OFF_SHARED_INFERRED);
   LOAD_STRFIELDS(this->funcnamestr, this->funcnamelen,
                  this->funcnameattrs);
 }
@@ -533,10 +470,7 @@ dtrace:helper:ustack:
 /!this->done && this->funcnamelen == 0/
 {
   APPEND_CHR('(');
-  APPEND_CHR('a');
-  APPEND_CHR('n');
-  APPEND_CHR('o');
-  APPEND_CHR('n');
+  APPEND_CHR4('a','n','o','n');
   APPEND_CHR(')');
 }
 
@@ -548,15 +482,19 @@ APPEND_V8STR(this->funcnamestr, this->funcnamelen, this->funcnameattrs)
 dtrace:helper:ustack:
 /!this->done/
 {
-  this->script = COPYIN_UINT32(this->shared + V8_OFF_SHARED_SCRIPT);
-  this->scriptnamestr = COPYIN_UINT32(this->script + V8_OFF_SCRIPT_NAME);
+  this->script = COPYIN_PTR(this->shared + V8_OFF_SHARED_SCRIPT);
+  this->scriptnamestr = COPYIN_PTR(this->script + V8_OFF_SCRIPT_NAME);
   LOAD_STRFIELDS(this->scriptnamestr, this->scriptnamelen,
                  this->scriptnameattrs);
 
-  APPEND_CHR(' ');
-  APPEND_CHR('a');
-  APPEND_CHR('t');
-  APPEND_CHR(' ');
+  APPEND_CHR4(' ','a','t',' ');
+}
+
+dtrace:helper:ustack:
+/!this->done && this->scriptnamelen == 0/
+{
+  APPEND_CHR8('<','u','n','k','n','o','w','n');
+  APPEND_CHR('>');
 }
 
 APPEND_V8STR(this->scriptnamestr, this->scriptnamelen, this->scriptnameattrs)
@@ -568,8 +506,8 @@ dtrace:helper:ustack:
 /!this->done/
 {
   this->position = COPYIN_UINT32(this->shared + V8_OFF_SHARED_FUNTOK);
-  this->line_ends = COPYIN_UINT32(this->script + V8_OFF_SCRIPT_LENDS);
-  this->map = V8_MAP_PTR(COPYIN_UINT32(this->line_ends + V8_OFF_HEAPOBJ_MAP));
+  this->line_ends = COPYIN_PTR(this->script + V8_OFF_SCRIPT_LENDS);
+  this->map = V8_MAP_PTR(COPYIN_PTR(this->line_ends + V8_OFF_HEAPOBJ_MAP));
   this->le_attrs = COPYIN_UINT8(this->map + V8_OFF_MAP_ATTRS);
 }
 
@@ -581,14 +519,7 @@ dtrace:helper:ustack:
    * undefined because V8 has not had to compute it yet.  In this case we
    * just show the raw position and call it a day.
    */
-  APPEND_CHR(' ');
-  APPEND_CHR('p');
-  APPEND_CHR('o');
-  APPEND_CHR('s');
-  APPEND_CHR('i');
-  APPEND_CHR('t');
-  APPEND_CHR('i');
-  APPEND_CHR('o');
+  APPEND_CHR8(' ','p','o','s','i','t','i','o');
   APPEND_CHR('n');
   APPEND_CHR(' ');
   APPEND_NUM(this->position);
@@ -608,10 +539,10 @@ dtrace:helper:ustack:
 {
   /* initialize binary search */
   this->bsearch_line = this->position <
-      COPYIN_UINT32(this->line_ends + V8_OFF_FA_DATA) ? 1 : 0;
+      SMI_VALUE(COPYIN_PTR(this->line_ends + V8_OFF_FA_DATA)) ? 1 : 0;
   this->bsearch_min = 0;
   this->bsearch_max = this->bsearch_line != 0 ? 0 :
-      SMI_VALUE(COPYIN_UINT32(this->line_ends + V8_OFF_FA_SIZE)) - 1;
+      SMI_VALUE(COPYIN_PTR(this->line_ends + V8_OFF_FA_SIZE)) - 1;
 }
 
 /*
@@ -628,16 +559,18 @@ dtrace:helper:ustack:
     \
     dtrace:helper:ustack: \
     /!this->done && this->bsearch_max >= 1 && \
-     this->position > COPYIN_UINT32(this->line_ends + V8_OFF_FA_DATA + \
-                                    this->ii * sizeof (uint32_t))/ \
+     this->position > SMI_VALUE( \
+         COPYIN_PTR(this->line_ends + V8_OFF_FA_DATA + \
+                    this->ii * sizeof (uint32_t)))/ \
     { \
       this->bsearch_min = this->ii + 1; \
     } \
     \
     dtrace:helper:ustack: \
     /!this->done && this->bsearch_max >= 1 && \
-     this->position <= COPYIN_UINT32(this->line_ends + V8_OFF_FA_DATA + \
-                                     (this->ii - 1) * sizeof (uint32_t))/ \
+     this->position <= SMI_VALUE( \
+         COPYIN_PTR(this->line_ends + V8_OFF_FA_DATA + \
+                    (this->ii - 1) * sizeof (uint32_t)))/ \
     { \
       this->bsearch_max = this->ii - 1; \
     }
@@ -668,10 +601,7 @@ dtrace:helper:ustack:
 /!this->done/
 {
   APPEND_CHR(' ');
-  APPEND_CHR('l');
-  APPEND_CHR('i');
-  APPEND_CHR('n');
-  APPEND_CHR('e');
+  APPEND_CHR4('l','i','n','e');
   APPEND_CHR(' ');
   APPEND_NUM(this->bsearch_line);
   APPEND_CHR('\0');
diff --git a/tools/genv8constants.py b/tools/genv8constants.py
index efc644152d..fb8b5ffa8c 100755
--- a/tools/genv8constants.py
+++ b/tools/genv8constants.py
@@ -18,8 +18,10 @@ if len(sys.argv) != 3:
 outfile = file(sys.argv[1], 'w');
 pipe = subprocess.Popen([ 'objdump', '-z', '-D', sys.argv[2] ],
     bufsize=-1, stdout=subprocess.PIPE).stdout;
-pattern = re.compile('00000000 <(v8dbg_.*)>:');
-numpattern = re.compile('[0-9a-fA-F]{2}');
+pattern = re.compile('(00000000|0000000000000000) <(.*)>:');
+v8dbg = re.compile('^v8dbg.*$')
+numpattern = re.compile('^[0-9a-fA-F]{2} $');
+octets = 4
 
 outfile.write("""
 /*
@@ -32,13 +34,27 @@ outfile.write("""
 #ifndef V8_CONSTANTS_H
 #define V8_CONSTANTS_H
 
-#if defined(__i386)
 """);
 
 curr_sym = None;
 curr_val = 0;
 curr_octet = 0;
 
+def out_reset():
+  global curr_sym, curr_val, curr_octet
+  curr_sym = None;
+  curr_val = 0;
+  curr_octet = 0;
+
+def out_define():
+  global curr_sym, curr_val, curr_octet, outfile, octets
+  if curr_sym != None:
+    if curr_val & 0x80000000 != 0:
+      outfile.write("#define %s -0x%x\n" % (curr_sym.upper(), 0x100000000 - curr_val));
+    else:
+      outfile.write("#define %s 0x%x\n" % (curr_sym.upper(), curr_val));
+  out_reset();
+
 for line in pipe:
   if curr_sym != None:
     #
@@ -51,32 +67,34 @@ for line in pipe:
     for i in range (0, 3):
       # 6-character margin, 2-characters + 1 space for each field
       idx = 6 + i * 3;
-      octetstr = line[idx:idx+2]
+      octetstr = line[idx:idx+3]
       if not numpattern.match(octetstr):
         break;
 
+      if curr_octet > octets:
+        break;
+
       curr_val += int('0x%s' % octetstr, 16) << (curr_octet * 8);
       curr_octet += 1;
 
-    if curr_octet < 4:
-      continue;
-
-    outfile.write("#define %s 0x%x\n" % (curr_sym.upper(), curr_val));
-    curr_sym = None;
-    curr_val = 0;
-    curr_octet = 0;
-    continue;
-
   match = pattern.match(line)
   if match == None:
     continue;
 
-  curr_sym = match.group(1);
+  octets = len(match.group(1)) / 2;
+
+  # Print previous symbol
+  out_define();
+
+  v8match = v8dbg.match(match.group(2));
+  if v8match != None:
+    out_reset();
+    curr_sym = match.group(2);
+
+# Print last symbol
+out_define();
 
 outfile.write("""
-#else
-#error "only i386 is supported for DTrace ustack helper"
-#endif
 
 #endif /* V8_CONSTANTS_H */
 """);