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/* 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  */