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/* DWARF2 EH unwinding support for TPF OS.

   Copyright (C) 2004, 2005 Free Software Foundation, Inc.

   Contributed by P.J. Darcy (darcypj@us.ibm.com).

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 into combinations with other programs,

and to distribute those combinations 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 a combined

executable.)

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.  */

#include <dlfcn.h>

/* Function Name: __isPATrange

   Parameters passed into it:  address to check

   Return Value: A 1 if address is in pat code "range", 0 if not

   Description: This function simply checks to see if the address

   passed to it is in the CP pat code range.  */

#define MIN_PATRANGE 0x10000

#define MAX_PATRANGE 0x800000

static inline unsigned int

__isPATrange (void *addr)

{

  if (addr > (void *)MIN_PATRANGE && addr < (void *)MAX_PATRANGE)

    return 1;

  else

    return 0;

}

/* TPF return address offset from start of stack frame.  */

#define TPFRA_OFFSET 168

/* Exceptions macro defined for TPF so that functions without

   dwarf frame information can be used with exceptions.  */

#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 long int regs;

  unsigned long int new_cfa;

  int i;

  regs = *((unsigned long int *)

        (((unsigned long int) context->cfa) - STACK_POINTER_OFFSET));

  /* Are we going through special linkage code?  */

  if (__isPATrange (context->ra))

    {

      /* Our return register isn't zero for end of stack, so

         check backward stackpointer to see if it is zero.  */

      if (regs == NULL)

         return _URC_END_OF_STACK;

      /* No stack frame.  */

      fs->cfa_how = CFA_REG_OFFSET;

      fs->cfa_reg = 15;

      fs->cfa_offset = STACK_POINTER_OFFSET;

      /* All registers remain unchanged ...  */

      for (i = 0; i < 32; i++)

        {

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

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

        }

      /* ... except for %r14, which is stored at CFA-112

         and used as return address.  */

      fs->regs.reg[14].how = REG_SAVED_OFFSET;

      fs->regs.reg[14].loc.offset = TPFRA_OFFSET - STACK_POINTER_OFFSET;

      fs->retaddr_column = 14;

      return _URC_NO_REASON;

    }

  regs = *((unsigned long int *)

        (((unsigned long int) context->cfa) - STACK_POINTER_OFFSET));

  new_cfa = regs + STACK_POINTER_OFFSET;

  fs->cfa_how = CFA_REG_OFFSET;

  fs->cfa_reg = 15;

  fs->cfa_offset = new_cfa -

        (unsigned long int) context->cfa + STACK_POINTER_OFFSET;

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

    {

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

      fs->regs.reg[i].loc.offset = regs + i*8 - new_cfa;

    }

  for (i = 0; i < 4; i++)

    {

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

      fs->regs.reg[16 + i].loc.offset = regs + 16*8 + i*8 - new_cfa;

    }

  fs->retaddr_column = 14;

  return _URC_NO_REASON;

}

/* Function Name: __tpf_eh_return

   Parameters passed into it: Destination address to jump to.

   Return Value: Converted Destination address if a Pat Stub exists.

   Description: This function swaps the unwinding return address

      with the cp stub code.  The original target return address is

      then stored into the tpf return address field.  The cp stub

      code is searched for by climbing back up the stack and

      comparing the tpf stored return address object address to

      that of the targets object address.  */

#define CURRENT_STACK_PTR() \

  ({ register unsigned long int *stack_ptr asm ("%r15"); stack_ptr; })

#define PREVIOUS_STACK_PTR() \

  ((unsigned long int *)(*(CURRENT_STACK_PTR())))

#define RA_OFFSET 112

#define R15_OFFSET 120

#define TPFAREA_OFFSET 160

#define TPFAREA_SIZE STACK_POINTER_OFFSET-TPFAREA_OFFSET

#define INVALID_RETURN 0

void * __tpf_eh_return (void *target);

void *

__tpf_eh_return (void *target)

{

  Dl_info targetcodeInfo, currentcodeInfo;

  int retval;

  void *current, *stackptr, *destination_frame;

  unsigned long int shifter, is_a_stub;

  is_a_stub = 0;

  /* Get code info for target return's address.  */

  retval = dladdr (target, &targetcodeInfo);

  /* Ensure the code info is valid (for target).  */

  if (retval != INVALID_RETURN)

    {

      /* Get the stack pointer of the stack frame to be modified by

         the exception unwinder.  So that we can begin our climb

         there.  */

      stackptr = (void *) *((unsigned long int *) (*(PREVIOUS_STACK_PTR())));

      /* Begin looping through stack frames.  Stop if invalid

         code information is retrieved or if a match between the

         current stack frame iteration shared object's address

         matches that of the target, calculated above.  */

      do

        {

          /* Get return address based on our stackptr iterator.  */

          current = (void *) *((unsigned long int *)

                      (stackptr+RA_OFFSET));

          /* Is it a Pat Stub?  */

          if (__isPATrange (current))

            {

              /* Yes it was, get real return address

                 in TPF stack area.  */

              current = (void *) *((unsigned long int *)

                          (stackptr+TPFRA_OFFSET));

              is_a_stub = 1;

            }

          /* Get codeinfo on RA so that we can figure out

             the module address.  */

          retval = dladdr (current, &currentcodeInfo);

          /* Check that codeinfo for current stack frame is valid.

             Then compare the module address of current stack frame

             to target stack frame to determine if we have the pat

             stub address we want.  Also ensure we are dealing

             with a module crossing, stub return address. */

          if (is_a_stub && retval != INVALID_RETURN

             && targetcodeInfo.dli_fbase == currentcodeInfo.dli_fbase)

             {

               /* Yes! They are in the same module.

                  Force copy of TPF private stack area to

                  destination stack frame TPF private area. */

               destination_frame = (void *) *((unsigned long int *)

                   (*PREVIOUS_STACK_PTR() + R15_OFFSET));

               /* Copy TPF linkage area from current frame to

                  destination frame.  */

               memcpy((void *) (destination_frame + TPFAREA_OFFSET),

                 (void *) (stackptr + TPFAREA_OFFSET), TPFAREA_SIZE);

               /* Now overlay the

                  real target address into the TPF stack area of

                  the target frame we are jumping to.  */

               *((unsigned long int *) (destination_frame +

                   TPFRA_OFFSET)) = (unsigned long int) target;

               /* Before returning the desired pat stub address to

                  the exception handling unwinder so that it can

                  actually do the "leap" shift out the low order

                  bit designated to determine if we are in 64BIT mode.

                  This is necessary for CTOA stubs.

                  Otherwise we leap one byte past where we want to

                  go to in the TPF pat stub linkage code.  */

               shifter = *((unsigned long int *)

                     (stackptr + RA_OFFSET));

               shifter &= ~1ul;

               /* Store Pat Stub Address in destination Stack Frame.  */

               *((unsigned long int *) (destination_frame +

                   RA_OFFSET)) = shifter;

               /* Re-adjust pat stub address to go to correct place

                  in linkage.  */

               shifter = shifter - 4;

               return (void *) shifter;

             }

          /* Desired module pat stub not found ...

             Bump stack frame iterator.  */

          stackptr = (void *) *(unsigned long int *) stackptr;

          is_a_stub = 0;

        }  while (stackptr && retval != INVALID_RETURN

                && targetcodeInfo.dli_fbase != currentcodeInfo.dli_fbase);

    }

  /* No pat stub found, could be a problem?  Simply return unmodified

     target address.  */

  return target;

}