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/* DWARF2 EH unwinding support for PA Linux.

   Copyright (C) 2004, 2005 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 2, or (at your option)

any later version.

In addition to the permissions in the GNU General Public License, the

Free Software Foundation gives you unlimited permission to link the

compiled version of this file with other programs, and to distribute

those programs without any restriction coming from the use of this

file.  (The General Public License restrictions do apply in other

respects; for example, they cover modification of the file, and

distribution when not linked into another program.)

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.

You should have received a copy of the GNU General Public License

along with GCC; see the file COPYING.  If not, write to

the Free Software Foundation, 51 Franklin Street, Fifth Floor,

Boston, MA 02110-1301, USA.  */

/* Do code reading to identify a signal frame, and set the frame

   state data appropriately.  See unwind-dw2.c for the structs.  */

#include <signal.h>

#include <sys/ucontext.h>

/* Unfortunately, because of various bugs and changes to the kernel,

   we have several cases to deal with.

   In 2.4, the signal trampoline is 4 words, and (CONTEXT)->ra should

   point directly at the beginning of the trampoline and struct rt_sigframe.

   In <= 2.6.5-rc2-pa3, the signal trampoline is 9 words, and

   (CONTEXT)->ra points at the 4th word in the trampoline structure.  This

   is wrong, it should point at the 5th word.  This is fixed in 2.6.5-rc2-pa4.

   To detect these cases, we first take (CONTEXT)->ra, align it to 64-bytes

   to get the beginning of the signal frame, and then check offsets 0, 4

   and 5 to see if we found the beginning of the trampoline.  This will

   tell us how to locate the sigcontext structure.

   Note that with a 2.4 64-bit kernel, the signal context is not properly

   passed back to userspace so the unwind will not work correctly.  */

#define MD_FALLBACK_FRAME_STATE_FOR pa32_fallback_frame_state

static _Unwind_Reason_Code

pa32_fallback_frame_state (struct _Unwind_Context *context,

                           _Unwind_FrameState *fs)

{

  unsigned long sp = (unsigned long)context->ra & ~63;

  unsigned int *pc = (unsigned int *)sp;

  unsigned long off;

  _Unwind_Ptr new_cfa;

  int i;

  struct sigcontext *sc;

  struct rt_sigframe {

    struct siginfo info;

    struct ucontext uc;

  } *frame;

  /* rt_sigreturn trampoline:

     3419000x ldi 0, %r25 or ldi 1, %r25   (x = 0 or 2)

     3414015a ldi __NR_rt_sigreturn, %r20

     e4008200 be,l 0x100(%sr2, %r0), %sr0, %r31

     08000240 nop  */

  if (pc[0] == 0x34190000 || pc[0] == 0x34190002)

    off = 4*4;

  else if (pc[4] == 0x34190000 || pc[4] == 0x34190002)

    {

      pc += 4;

      off = 10 * 4;

    }

  else if (pc[5] == 0x34190000 || pc[5] == 0x34190002)

    {

      pc += 5;

      off = 10 * 4;

    }

  else

    {

      /* We may have to unwind through an alternate signal stack.

         We assume that the alignment of the alternate signal stack

         is BIGGEST_ALIGNMENT (i.e., that it has been allocated using

         malloc).  As a result, we can't distinguish trampolines

         used prior to 2.6.5-rc2-pa4.  However after 2.6.5-rc2-pa4,

         the return address of a signal trampoline will be on an odd

         word boundary and we can then determine the frame offset.  */

      sp = (unsigned long)context->ra;

      pc = (unsigned int *)sp;

      if ((pc[0] == 0x34190000 || pc[0] == 0x34190002) && (sp & 4))

        off = 5 * 4;

      else

        return _URC_END_OF_STACK;

    }

  if (pc[1] != 0x3414015a

      || pc[2] != 0xe4008200

      || pc[3] != 0x08000240)

    return _URC_END_OF_STACK;

  frame = (struct rt_sigframe *)(sp + off);

  sc = &frame->uc.uc_mcontext;

  new_cfa = sc->sc_gr[30];

  fs->cfa_how = CFA_REG_OFFSET;

  fs->cfa_reg = 30;

  fs->cfa_offset = new_cfa - (long) context->cfa;

  for (i = 1; i <= 31; i++)

    {

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

      fs->regs.reg[i].loc.offset = (long)&sc->sc_gr[i] - new_cfa;

    }

  for (i = 4; i <= 31; i++)

    {

      /* FP regs have left and right halves */

      fs->regs.reg[2*i+24].how = REG_SAVED_OFFSET;

      fs->regs.reg[2*i+24].loc.offset

        = (long)&sc->sc_fr[i] - new_cfa;

      fs->regs.reg[2*i+24+1].how = REG_SAVED_OFFSET;

      fs->regs.reg[2*i+24+1].loc.offset

        = (long)&sc->sc_fr[i] + 4 - new_cfa;

    }

  fs->regs.reg[88].how = REG_SAVED_OFFSET;

  fs->regs.reg[88].loc.offset = (long) &sc->sc_sar - new_cfa;

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

  fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].loc.offset

    = (long) &sc->sc_iaoq[0] - new_cfa;

  fs->retaddr_column = DWARF_ALT_FRAME_RETURN_COLUMN;

  return _URC_NO_REASON;

}