Index: libgcc/config/i386/freebsd-unwind.h
===================================================================
--- libgcc/config/i386/freebsd-unwind.h	(revision 254205)
+++ libgcc/config/i386/freebsd-unwind.h	(working copy)
@@ -28,7 +28,10 @@
 
 #include <sys/types.h>
 #include <signal.h>
+#include <unistd.h>
+#include <sys/sysctl.h>
 #include <sys/ucontext.h>
+#include <sys/user.h>
 #include <machine/sigframe.h>
 
 #define REG_NAME(reg)	sf_uc.uc_mcontext.mc_## reg
@@ -36,38 +39,46 @@
 #ifdef __x86_64__
 #define MD_FALLBACK_FRAME_STATE_FOR x86_64_freebsd_fallback_frame_state
 
+static int
+x86_64_outside_sigtramp_range (unsigned char *pc)
+{
+  static int sigtramp_range_determined = 0;
+  static unsigned char *sigtramp_start, *sigtramp_end;
+
+  if (sigtramp_range_determined == 0)
+    {
+      struct kinfo_sigtramp kst = {0};
+      size_t len = sizeof (kst);
+      int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_SIGTRAMP, getpid() };
+
+      sigtramp_range_determined = 1;
+      if (sysctl (mib, 4, &kst, &len, NULL, 0) == 0)
+      {
+        sigtramp_range_determined = 2;
+        sigtramp_start = kst.ksigtramp_start;
+        sigtramp_end   = kst.ksigtramp_end;
+      }
+    }
+  if (sigtramp_range_determined < 2)  /* sysctl failed if < 2 */
+    return 1;
+
+  return (pc < sigtramp_start || pc >= sigtramp_end);
+}
+
 static _Unwind_Reason_Code
 x86_64_freebsd_fallback_frame_state
 (struct _Unwind_Context *context, _Unwind_FrameState *fs)
 {
   struct sigframe *sf;
-  long new_cfa;
+  _Unwind_Ptr new_cfa;
 
-  /* Prior to FreeBSD 9, the signal trampoline was located immediately
-     before the ps_strings.  To support non-executable stacks on AMD64,
-     the sigtramp was moved to a shared page for FreeBSD 9.  Unfortunately
-     this means looking frame patterns again (sys/amd64/amd64/sigtramp.S)
-     rather than using the robust and convenient KERN_PS_STRINGS trick.
-
-     <pc + 00>:  lea     0x10(%rsp),%rdi
-     <pc + 05>:  pushq   $0x0
-     <pc + 17>:  mov     $0x1a1,%rax
-     <pc + 14>:  syscall
-
-     If we can't find this pattern, we're at the end of the stack.
-  */
-
-  if (!(   *(unsigned int *)(context->ra)      == 0x247c8d48
-        && *(unsigned int *)(context->ra +  4) == 0x48006a10
-        && *(unsigned int *)(context->ra +  8) == 0x01a1c0c7
-        && *(unsigned int *)(context->ra + 12) == 0x050f0000 ))
+  if (x86_64_outside_sigtramp_range(context->ra))
     return _URC_END_OF_STACK;
 
   sf = (struct sigframe *) context->cfa;
   new_cfa = sf->REG_NAME(rsp);
   fs->regs.cfa_how = CFA_REG_OFFSET;
-  /* Register 7 is rsp  */
-  fs->regs.cfa_reg = 7;
+  fs->regs.cfa_reg =  __LIBGCC_STACK_POINTER_REGNUM__;
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */