diff --git a/include/tdep-x86_64/libunwind_i.h b/include/tdep-x86_64/libunwind_i.h
index 974d610e..f6a02897 100644
--- a/include/tdep-x86_64/libunwind_i.h
+++ b/include/tdep-x86_64/libunwind_i.h
@@ -63,7 +63,8 @@ struct cursor
       {
 	X86_64_SCF_NONE,		/* no signal frame encountered */
 	X86_64_SCF_LINUX_RT_SIGFRAME,	/* Linux ucontext_t */
-	X86_64_SCF_FREEBSD_SIGFRAME,	/* FreeBSD ucontext_t */
+	X86_64_SCF_FREEBSD_SIGFRAME,	/* FreeBSD signal frame */
+	X86_64_SCF_FREEBSD_SYSCALL,	/* FreeBSD syscall */
       }
     sigcontext_format;
     unw_word_t sigcontext_addr;
diff --git a/src/ptrace/_UPT_find_proc_info.c b/src/ptrace/_UPT_find_proc_info.c
index 2b81e59a..d06c84ca 100644
--- a/src/ptrace/_UPT_find_proc_info.c
+++ b/src/ptrace/_UPT_find_proc_info.c
@@ -262,8 +262,9 @@ _UPTi_find_unwind_table (struct UPT_info *ui, unw_addr_space_t as,
 
   if (hdr->table_enc != (DW_EH_PE_datarel | DW_EH_PE_sdata4))
     {
+#if 1
       abort ();
-#if 0
+#else
       /* If there is no search table or it has an unsupported
 	 encoding, fall back on linear search.  */
       if (hdr->table_enc == DW_EH_PE_omit)
diff --git a/src/x86_64/Gis_signal_frame.c b/src/x86_64/Gis_signal_frame.c
index fd6599c1..4e516663 100644
--- a/src/x86_64/Gis_signal_frame.c
+++ b/src/x86_64/Gis_signal_frame.c
@@ -54,7 +54,8 @@ unw_is_signal_frame (unw_cursor_t *cursor)
       || (ret = (*a->access_mem) (as, ip + 8, &w1, 0, arg)) < 0)
     return 0;
   w1 &= 0xff;
-  return (w0 == 0x0f0000000fc0c748 && w1 == 0x05);
+  return (w0 == 0x0f0000000fc0c748 && w1 == 0x05) ?
+	  X86_64_SCF_LINUX_RT_SIGFRAME : X86_64_SCF_NONE;
 }
 
 #elif defined(__FreeBSD__)
@@ -63,7 +64,7 @@ unw_is_signal_frame (unw_cursor_t *cursor)
 {
   /* XXXKIB */
   struct cursor *c = (struct cursor *) cursor;
-  unw_word_t w0, w1, w2, w3, w4, ip;
+  unw_word_t w0, w1, w2, b0, ip;
   unw_addr_space_t as;
   unw_accessors_t *a;
   void *arg;
@@ -88,10 +89,20 @@ eb fd			jmp	0b
       || (ret = (*a->access_mem) (as, ip + 16, &w2, 0, arg)) < 0)
     return 0;
   w2 &= 0xffffff;
-  ret = w0 == 0x48006a10247c8d48 &&
-	  w1 == 0x050f000001a1c0c7 &&
-	  w2 == 0x0000000000fdebf4;
-  return ret;
+  if (w0 == 0x48006a10247c8d48 &&
+      w1 == 0x050f000001a1c0c7 &&
+      w2 == 0x0000000000fdebf4)
+	  return X86_64_SCF_FREEBSD_SIGFRAME;
+  /* Check if RIP points at standard syscall sequence.
+49 89 ca	mov    %rcx,%r10
+0f 05		syscall
+  */
+  if ((ret = (*a->access_mem) (as, ip - 5, &b0, 0, arg)) < 0)
+    return (0);
+  b0 &= 0xffffffffff;
+  if (b0 == 0x000000050fca8949)
+    return X86_64_SCF_FREEBSD_SYSCALL;
+  return X86_64_SCF_NONE;
 }
 
 #else /* !__linux__ && !__FreeBSD__ */
diff --git a/src/x86_64/Gstep.c b/src/x86_64/Gstep.c
index 5a1654e1..96f1c902 100644
--- a/src/x86_64/Gstep.c
+++ b/src/x86_64/Gstep.c
@@ -83,7 +83,24 @@ unw_step (unw_cursor_t *cursor)
 
       Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
 
-      if (unw_is_signal_frame (cursor))
+      c->sigcontext_format = unw_is_signal_frame (cursor);
+      if (c->sigcontext_format == X86_64_SCF_FREEBSD_SYSCALL) {
+	  c->dwarf.loc[RCX] = c->dwarf.loc[R10];
+//	  rsp_loc = DWARF_LOC(c->dwarf.cfa - 8, 0);
+//	  rbp_loc = c->dwarf.loc[RBP];
+	  c->dwarf.loc[RIP] = DWARF_LOC (c->dwarf.cfa, 0);
+	  ret = dwarf_get (&c->dwarf, c->dwarf.loc[RIP], &c->dwarf.ip);
+	  Debug (1, "Frame Chain [RIP=0x%Lx] = 0x%Lx\n",
+		     (unsigned long long) DWARF_GET_LOC (c->dwarf.loc[RIP]),
+		     (unsigned long long) c->dwarf.ip);
+	  if (ret < 0)
+	    {
+	      Debug (2, "returning %d\n", ret);
+	      return ret;
+	    }
+	  c->dwarf.cfa += 8;
+	  return 1;
+      } else if (c->sigcontext_format != X86_64_SCF_NONE)
 	{
 	  unw_word_t ucontext;
 
@@ -91,10 +108,13 @@ unw_step (unw_cursor_t *cursor)
 
 #if defined __linux__
 	  ucontext = c->dwarf.cfa;
-	  c->sigcontext_format = X86_64_SCF_LINUX_RT_SIGFRAME;
+	  if (c->sigcontext_format != X86_64_SCF_LINUX_RT_SIGFRAME)
+	    return -UNW_EBADFRAME;
 #elif defined __FreeBSD__
-	  ucontext = c->dwarf.cfa + offsetof(struct sigframe, sf_uc);
-	  c->sigcontext_format = X86_64_SCF_FREEBSD_SIGFRAME;
+	  if (c->sigcontext_format == X86_64_SCF_FREEBSD_SIGFRAME)
+	    ucontext = c->dwarf.cfa + offsetof(struct sigframe, sf_uc);
+	  else
+	    return -UNW_EBADFRAME;
 #endif
 	  c->sigcontext_addr = c->dwarf.cfa;