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/* DWARF2 EH unwinding support for S/390 Linux.

   Copyright (C) 2004, 2005, 2006, 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.c for the structs.  */

#define MD_FALLBACK_FRAME_STATE_FOR s390_fallback_frame_state

static _Unwind_Reason_Code

s390_fallback_frame_state (struct _Unwind_Context *context,

                           _Unwind_FrameState *fs)

{

  unsigned char *pc = context->ra;

  long new_cfa;

  int i;

  typedef struct

  {

    unsigned long psw_mask;

    unsigned long psw_addr;

    unsigned long gprs[16];

    unsigned int  acrs[16];

    unsigned int  fpc;

    unsigned int  __pad;

    double        fprs[16];

  } __attribute__ ((__aligned__ (8))) sigregs_;

  sigregs_ *regs;

  int *signo;

  /* svc $__NR_sigreturn or svc $__NR_rt_sigreturn  */

  if (pc[0] != 0x0a || (pc[1] != 119 && pc[1] != 173))

    return _URC_END_OF_STACK;

  /* Legacy frames:

       old signal mask (8 bytes)

       pointer to sigregs (8 bytes) - points always to next location

       sigregs

       retcode

     This frame layout was used on kernels < 2.6.9 for non-RT frames,

     and on kernels < 2.4.13 for RT frames as well.  Note that we need

     to look at RA to detect this layout -- this means that if you use

     sa_restorer to install a different signal restorer on a legacy

     kernel, unwinding from signal frames will not work.  */

  if (context->ra == context->cfa + 16 + sizeof (sigregs_))

    {

      regs = (sigregs_ *)(context->cfa + 16);

      signo = NULL;

    }

  /* New-style RT frame:

     retcode + alignment (8 bytes)

     siginfo (128 bytes)

     ucontext (contains sigregs)  */

  else if (pc[1] == 173 /* __NR_rt_sigreturn */)

    {

      struct ucontext_

      {

        unsigned long     uc_flags;

        struct ucontext_ *uc_link;

        unsigned long     uc_stack[3];

        sigregs_          uc_mcontext;

      } *uc = context->cfa + 8 + 128;

      regs = &uc->uc_mcontext;

      signo = context->cfa + sizeof(long);

    }

  /* New-style non-RT frame:

     old signal mask (8 bytes)

     pointer to sigregs (followed by signal number)  */

  else

    {

      regs = *(sigregs_ **)(context->cfa + 8);

      signo = (int *)(regs + 1);

    }

  new_cfa = regs->gprs[15] + 16*sizeof(long) + 32;

  fs->regs.cfa_how = CFA_REG_OFFSET;

  fs->regs.cfa_reg = 15;

  fs->regs.cfa_offset =

    new_cfa - (long) context->cfa + 16*sizeof(long) + 32;

  for (i = 0; i < 16; i++)

    {

      fs->regs.reg[i].how = REG_SAVED_OFFSET;

      fs->regs.reg[i].loc.offset =

        (long)&regs->gprs[i] - new_cfa;

    }

  for (i = 0; i < 16; i++)

    {

      fs->regs.reg[16+i].how = REG_SAVED_OFFSET;

      fs->regs.reg[16+i].loc.offset =

        (long)&regs->fprs[i] - new_cfa;

    }

  /* Load return addr from PSW into dummy register 32.  */

  fs->regs.reg[32].how = REG_SAVED_OFFSET;

  fs->regs.reg[32].loc.offset = (long)&regs->psw_addr - new_cfa;

  fs->retaddr_column = 32;

  /* SIGILL, SIGFPE and SIGTRAP are delivered with psw_addr

     after the faulting instruction rather than before it.

     Don't set FS->signal_frame in that case.  */

  if (!signo || (*signo != 4 && *signo != 5 && *signo != 8))

    fs->signal_frame = 1;

  return _URC_NO_REASON;

}