--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/config/xtensa/linux-unwind.h	Fri Jul 17 14:47:48 2009 +0900
@@ -0,0 +1,97 @@
+/* DWARF2 EH unwinding support for Xtensa.
+   Copyright (C) 2008, 2009 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+/* Do code reading to identify a signal frame, and set the frame
+   state data appropriately.  See unwind-dw2-xtensa.c for the structs.
+   Don't use this at all if inhibit_libc is used.  */
+
+#ifndef inhibit_libc
+
+#include <signal.h>
+#include <sys/ucontext.h>
+
+/* Encoded bytes for Xtensa instructions:
+	movi a2, __NR_rt_sigreturn
+	syscall
+	entry (first byte only)
+   Some of the bytes are endian-dependent.  */
+
+#define MOVI_BYTE0 0x22
+#define MOVI_BYTE2 225 /* __NR_rt_sigreturn */
+#define SYSC_BYTE0 0
+#define SYSC_BYTE2 0
+
+#ifdef __XTENSA_EB__
+#define MOVI_BYTE1 0x0a
+#define SYSC_BYTE1 0x05
+#define ENTRY_BYTE 0x6c
+#else
+#define MOVI_BYTE1 0xa0
+#define SYSC_BYTE1 0x50
+#define ENTRY_BYTE 0x36
+#endif
+
+#define MD_FALLBACK_FRAME_STATE_FOR xtensa_fallback_frame_state
+
+static _Unwind_Reason_Code
+xtensa_fallback_frame_state (struct _Unwind_Context *context,
+			     _Unwind_FrameState *fs)
+{
+  unsigned char *pc = context->ra;
+  struct sigcontext *sc;
+
+  struct rt_sigframe {
+    struct siginfo info;
+    struct ucontext uc;
+  } *rt_;
+
+  /* movi a2, __NR_rt_sigreturn; syscall */
+  if (pc[0] != MOVI_BYTE0
+      || pc[1] != MOVI_BYTE1
+      || pc[2] != MOVI_BYTE2
+      || pc[3] != SYSC_BYTE0
+      || pc[4] != SYSC_BYTE1
+      || pc[5] != SYSC_BYTE2)
+    return _URC_END_OF_STACK;
+
+  rt_ = context->sp;
+  sc = &rt_->uc.uc_mcontext;
+  fs->signal_regs = (_Unwind_Word *) sc->sc_a;
+
+  /* If the signal arrived just before an ENTRY instruction, find the return
+     address and pretend the signal arrived before executing the CALL.  */
+  if (*(unsigned char *) sc->sc_pc == ENTRY_BYTE)
+   {
+     unsigned callinc = (sc->sc_ps >> 16) & 3;
+     fs->signal_ra = ((sc->sc_a[callinc << 2] & XTENSA_RA_FIELD_MASK)
+		      | context->ra_high_bits) - 3;
+   }
+  else
+    fs->signal_ra = sc->sc_pc;
+
+  fs->signal_frame = 1;
+  return _URC_NO_REASON;
+}
+
+#endif /* ifdef inhibit_libc  */