2011-03-21 Daniel Jacobowitz <dan@codesourcery.com>

[official-gcc.git] / gcc / config / arm / unwind-arm.c

/* ARM EABI compliant unwinding routines.
   Copyright (C) 2004, 2005, 2009 Free Software Foundation, Inc.
   Contributed by Paul Brook

   This file 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.

   This file 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/>.  */

#include "unwind.h"

/* We add a prototype for abort here to avoid creating a dependency on
   target headers.  */
extern void abort (void);

/* Definitions for C++ runtime support routines.  We make these weak
   declarations to avoid pulling in libsupc++ unnecessarily.  */
typedef unsigned char bool;

typedef struct _ZSt9type_info type_info; /* This names C++ type_info type */

void __attribute__((weak)) __cxa_call_unexpected(_Unwind_Control_Block *ucbp);
bool __attribute__((weak)) __cxa_begin_cleanup(_Unwind_Control_Block *ucbp);
bool __attribute__((weak)) __cxa_type_match(_Unwind_Control_Block *ucbp,
                                            const type_info *rttip,
                                            bool is_reference,
                                            void **matched_object);

_Unwind_Ptr __attribute__((weak))
__gnu_Unwind_Find_exidx (_Unwind_Ptr, int *);

/* Misc constants.  */
#define R_IP    12
#define R_SP    13
#define R_LR    14
#define R_PC    15

#define EXIDX_CANTUNWIND 1
#define uint32_highbit (((_uw) 1) << 31)

#define UCB_FORCED_STOP_FN(ucbp) ((ucbp)->unwinder_cache.reserved1)
#define UCB_PR_ADDR(ucbp) ((ucbp)->unwinder_cache.reserved2)
#define UCB_SAVED_CALLSITE_ADDR(ucbp) ((ucbp)->unwinder_cache.reserved3)
#define UCB_FORCED_STOP_ARG(ucbp) ((ucbp)->unwinder_cache.reserved4)

struct core_regs
{
  _uw r[16];
};

/* We use normal integer types here to avoid the compiler generating
   coprocessor instructions.  */
struct vfp_regs
{
  _uw64 d[16];
  _uw pad;
};

struct vfpv3_regs
{
  /* Always populated via VSTM, so no need for the "pad" field from
     vfp_regs (which is used to store the format word for FSTMX).  */
  _uw64 d[16];
};

struct fpa_reg
{
  _uw w[3];
};

struct fpa_regs
{
  struct fpa_reg f[8];
};

struct wmmxd_regs
{
  _uw64 wd[16];
};

struct wmmxc_regs
{
  _uw wc[4];
};

/* Unwind descriptors.  */

typedef struct
{
  _uw16 length;
  _uw16 offset;
} EHT16;

typedef struct
{
  _uw length;
  _uw offset;
} EHT32;

/* The ABI specifies that the unwind routines may only use core registers,
   except when actually manipulating coprocessor state.  This allows
   us to write one implementation that works on all platforms by
   demand-saving coprocessor registers.

   During unwinding we hold the coprocessor state in the actual hardware
   registers and allocate demand-save areas for use during phase1
   unwinding.  */

typedef struct
{
  /* The first fields must be the same as a phase2_vrs.  */
  _uw demand_save_flags;
  struct core_regs core;
  _uw prev_sp; /* Only valid during forced unwinding.  */
  struct vfp_regs vfp;
  struct vfpv3_regs vfp_regs_16_to_31;
  struct fpa_regs fpa;
  struct wmmxd_regs wmmxd;
  struct wmmxc_regs wmmxc;
} phase1_vrs;

#define DEMAND_SAVE_VFP 1       /* VFP state has been saved if not set */
#define DEMAND_SAVE_VFP_D 2     /* VFP state is for FLDMD/FSTMD if set */
#define DEMAND_SAVE_VFP_V3 4    /* VFPv3 state for regs 16 .. 31 has
                                   been saved if not set */
#define DEMAND_SAVE_WMMXD 8     /* iWMMXt data registers have been
                                   saved if not set.  */
#define DEMAND_SAVE_WMMXC 16    /* iWMMXt control registers have been
                                   saved if not set.  */

/* This must match the structure created by the assembly wrappers.  */
typedef struct
{
  _uw demand_save_flags;
  struct core_regs core;
} phase2_vrs;


/* An exception index table entry.  */

typedef struct __EIT_entry
{
  _uw fnoffset;
  _uw content;
} __EIT_entry;

/* Assembly helper functions.  */

/* Restore core register state.  Never returns.  */
void __attribute__((noreturn)) restore_core_regs (struct core_regs *);


/* Coprocessor register state manipulation functions.  */

/* Routines for FLDMX/FSTMX format...  */
void __gnu_Unwind_Save_VFP (struct vfp_regs * p);
void __gnu_Unwind_Restore_VFP (struct vfp_regs * p);
void __gnu_Unwind_Save_WMMXD (struct wmmxd_regs * p);
void __gnu_Unwind_Restore_WMMXD (struct wmmxd_regs * p);
void __gnu_Unwind_Save_WMMXC (struct wmmxc_regs * p);
void __gnu_Unwind_Restore_WMMXC (struct wmmxc_regs * p);

/* ...and those for FLDMD/FSTMD format...  */
void __gnu_Unwind_Save_VFP_D (struct vfp_regs * p);
void __gnu_Unwind_Restore_VFP_D (struct vfp_regs * p);

/* ...and those for VLDM/VSTM format, saving/restoring only registers
   16 through 31.  */
void __gnu_Unwind_Save_VFP_D_16_to_31 (struct vfpv3_regs * p);
void __gnu_Unwind_Restore_VFP_D_16_to_31 (struct vfpv3_regs * p);

/* Restore coprocessor state after phase1 unwinding.  */
static void
restore_non_core_regs (phase1_vrs * vrs)
{
  if ((vrs->demand_save_flags & DEMAND_SAVE_VFP) == 0)
    {
      if (vrs->demand_save_flags & DEMAND_SAVE_VFP_D)
        __gnu_Unwind_Restore_VFP_D (&vrs->vfp);
      else
        __gnu_Unwind_Restore_VFP (&vrs->vfp);
    }

  if ((vrs->demand_save_flags & DEMAND_SAVE_VFP_V3) == 0)
    __gnu_Unwind_Restore_VFP_D_16_to_31 (&vrs->vfp_regs_16_to_31);

  if ((vrs->demand_save_flags & DEMAND_SAVE_WMMXD) == 0)
    __gnu_Unwind_Restore_WMMXD (&vrs->wmmxd);
  if ((vrs->demand_save_flags & DEMAND_SAVE_WMMXC) == 0)
    __gnu_Unwind_Restore_WMMXC (&vrs->wmmxc);
}

/* A better way to do this would probably be to compare the absolute address
   with a segment relative relocation of the same symbol.  */

extern int __text_start;
extern int __data_start;

/* The exception index table location.  */
extern __EIT_entry __exidx_start;
extern __EIT_entry __exidx_end;

/* ABI defined personality routines.  */
extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr0 (_Unwind_State,
    _Unwind_Control_Block *, _Unwind_Context *);// __attribute__((weak));
extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr1 (_Unwind_State,
    _Unwind_Control_Block *, _Unwind_Context *) __attribute__((weak));
extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr2 (_Unwind_State,
    _Unwind_Control_Block *, _Unwind_Context *) __attribute__((weak));

/* ABI defined routine to store a virtual register to memory.  */

_Unwind_VRS_Result _Unwind_VRS_Get (_Unwind_Context *context,
                                    _Unwind_VRS_RegClass regclass,
                                    _uw regno,
                                    _Unwind_VRS_DataRepresentation representation,
                                    void *valuep)
{
  phase1_vrs *vrs = (phase1_vrs *) context;

  switch (regclass)
    {
    case _UVRSC_CORE:
      if (representation != _UVRSD_UINT32
          || regno > 15)
        return _UVRSR_FAILED;
      *(_uw *) valuep = vrs->core.r[regno];
      return _UVRSR_OK;

    case _UVRSC_VFP:
    case _UVRSC_FPA:
    case _UVRSC_WMMXD:
    case _UVRSC_WMMXC:
      return _UVRSR_NOT_IMPLEMENTED;

    default:
      return _UVRSR_FAILED;
    }
}


/* ABI defined function to load a virtual register from memory.  */

_Unwind_VRS_Result _Unwind_VRS_Set (_Unwind_Context *context,
                                    _Unwind_VRS_RegClass regclass,
                                    _uw regno,
                                    _Unwind_VRS_DataRepresentation representation,
                                    void *valuep)
{
  phase1_vrs *vrs = (phase1_vrs *) context;

  switch (regclass)
    {
    case _UVRSC_CORE:
      if (representation != _UVRSD_UINT32
          || regno > 15)
        return _UVRSR_FAILED;

      vrs->core.r[regno] = *(_uw *) valuep;
      return _UVRSR_OK;

    case _UVRSC_VFP:
    case _UVRSC_FPA:
    case _UVRSC_WMMXD:
    case _UVRSC_WMMXC:
      return _UVRSR_NOT_IMPLEMENTED;

    default:
      return _UVRSR_FAILED;
    }
}


/* ABI defined function to pop registers off the stack.  */

_Unwind_VRS_Result _Unwind_VRS_Pop (_Unwind_Context *context,
                                    _Unwind_VRS_RegClass regclass,
                                    _uw discriminator,
                                    _Unwind_VRS_DataRepresentation representation)
{
  phase1_vrs *vrs = (phase1_vrs *) context;

  switch (regclass)
    {
    case _UVRSC_CORE:
      {
        _uw *ptr;
        _uw mask;
        int i;

        if (representation != _UVRSD_UINT32)
          return _UVRSR_FAILED;

        mask = discriminator & 0xffff;
        ptr = (_uw *) vrs->core.r[R_SP];
        /* Pop the requested registers.  */
        for (i = 0; i < 16; i++)
          {
            if (mask & (1 << i))
              vrs->core.r[i] = *(ptr++);
          }
        /* Writeback the stack pointer value if it wasn't restored.  */
        if ((mask & (1 << R_SP)) == 0)
          vrs->core.r[R_SP] = (_uw) ptr;
      }
      return _UVRSR_OK;

    case _UVRSC_VFP:
      {
        _uw start = discriminator >> 16;
        _uw count = discriminator & 0xffff;
        struct vfp_regs tmp;
        struct vfpv3_regs tmp_16_to_31;
        int tmp_count;
        _uw *sp;
        _uw *dest;
        int num_vfpv3_regs = 0;

        /* We use an approximation here by bounding _UVRSD_DOUBLE
           register numbers at 32 always, since we can't detect if
           VFPv3 isn't present (in such a case the upper limit is 16).  */
        if ((representation != _UVRSD_VFPX && representation != _UVRSD_DOUBLE)
            || start + count > (representation == _UVRSD_VFPX ? 16 : 32)
            || (representation == _UVRSD_VFPX && start >= 16))
          return _UVRSR_FAILED;

        /* Check if we're being asked to pop VFPv3-only registers
           (numbers 16 through 31).  */
        if (start >= 16)
          num_vfpv3_regs = count;
        else if (start + count > 16)
          num_vfpv3_regs = start + count - 16;

        if (num_vfpv3_regs && representation != _UVRSD_DOUBLE)
          return _UVRSR_FAILED;

        /* Demand-save coprocessor registers for stage1.  */
        if (start < 16 && (vrs->demand_save_flags & DEMAND_SAVE_VFP))
          {
            vrs->demand_save_flags &= ~DEMAND_SAVE_VFP;

            if (representation == _UVRSD_DOUBLE)
              {
                /* Save in FLDMD/FSTMD format.  */
                vrs->demand_save_flags |= DEMAND_SAVE_VFP_D;
                __gnu_Unwind_Save_VFP_D (&vrs->vfp);
              }
            else
              {
                /* Save in FLDMX/FSTMX format.  */
                vrs->demand_save_flags &= ~DEMAND_SAVE_VFP_D;
                __gnu_Unwind_Save_VFP (&vrs->vfp);
              }
          }

        if (num_vfpv3_regs > 0
            && (vrs->demand_save_flags & DEMAND_SAVE_VFP_V3))
          {
            vrs->demand_save_flags &= ~DEMAND_SAVE_VFP_V3;
            __gnu_Unwind_Save_VFP_D_16_to_31 (&vrs->vfp_regs_16_to_31);
          }

        /* Restore the registers from the stack.  Do this by saving the
           current VFP registers to a memory area, moving the in-memory
           values into that area, and restoring from the whole area.
           For _UVRSD_VFPX we assume FSTMX standard format 1.  */
        if (representation == _UVRSD_VFPX)
          __gnu_Unwind_Save_VFP (&tmp);
        else
          {
            /* Save registers 0 .. 15 if required.  */
            if (start < 16)
              __gnu_Unwind_Save_VFP_D (&tmp);

            /* Save VFPv3 registers 16 .. 31 if required.  */
            if (num_vfpv3_regs)
              __gnu_Unwind_Save_VFP_D_16_to_31 (&tmp_16_to_31);
          }

        /* Work out how many registers below register 16 need popping.  */
        tmp_count = num_vfpv3_regs > 0 ? 16 - start : count;

        /* Copy registers below 16, if needed.
           The stack address is only guaranteed to be word aligned, so
           we can't use doubleword copies.  */
        sp = (_uw *) vrs->core.r[R_SP];
        if (tmp_count > 0)
          {
            tmp_count *= 2;
            dest = (_uw *) &tmp.d[start];
            while (tmp_count--)
              *(dest++) = *(sp++);
          }

        /* Copy VFPv3 registers numbered >= 16, if needed.  */
        if (num_vfpv3_regs > 0)
          {
            /* num_vfpv3_regs is needed below, so copy it.  */
            int tmp_count_2 = num_vfpv3_regs * 2;
            int vfpv3_start = start < 16 ? 16 : start;

            dest = (_uw *) &tmp_16_to_31.d[vfpv3_start - 16];
            while (tmp_count_2--)
              *(dest++) = *(sp++);
          }

        /* Skip the format word space if using FLDMX/FSTMX format.  */
        if (representation == _UVRSD_VFPX)
          sp++;

        /* Set the new stack pointer.  */
        vrs->core.r[R_SP] = (_uw) sp;

        /* Reload the registers.  */
        if (representation == _UVRSD_VFPX)
          __gnu_Unwind_Restore_VFP (&tmp);
        else
          {
            /* Restore registers 0 .. 15 if required.  */
            if (start < 16)
              __gnu_Unwind_Restore_VFP_D (&tmp);

            /* Restore VFPv3 registers 16 .. 31 if required.  */
            if (num_vfpv3_regs > 0)
              __gnu_Unwind_Restore_VFP_D_16_to_31 (&tmp_16_to_31);
          }
      }
      return _UVRSR_OK;

    case _UVRSC_FPA:
      return _UVRSR_NOT_IMPLEMENTED;

    case _UVRSC_WMMXD:
      {
        _uw start = discriminator >> 16;
        _uw count = discriminator & 0xffff;
        struct wmmxd_regs tmp;
        _uw *sp;
        _uw *dest;

        if ((representation != _UVRSD_UINT64) || start + count > 16)
          return _UVRSR_FAILED;

        if (vrs->demand_save_flags & DEMAND_SAVE_WMMXD)
          {
            /* Demand-save resisters for stage1.  */
            vrs->demand_save_flags &= ~DEMAND_SAVE_WMMXD;
            __gnu_Unwind_Save_WMMXD (&vrs->wmmxd);
          }

        /* Restore the registers from the stack.  Do this by saving the
           current WMMXD registers to a memory area, moving the in-memory
           values into that area, and restoring from the whole area.  */
        __gnu_Unwind_Save_WMMXD (&tmp);

        /* The stack address is only guaranteed to be word aligned, so
           we can't use doubleword copies.  */
        sp = (_uw *) vrs->core.r[R_SP];
        dest = (_uw *) &tmp.wd[start];
        count *= 2;
        while (count--)
          *(dest++) = *(sp++);

        /* Set the new stack pointer.  */
        vrs->core.r[R_SP] = (_uw) sp;

        /* Reload the registers.  */
        __gnu_Unwind_Restore_WMMXD (&tmp);
      }
      return _UVRSR_OK;

    case _UVRSC_WMMXC:
      {
        int i;
        struct wmmxc_regs tmp;
        _uw *sp;

        if ((representation != _UVRSD_UINT32) || discriminator > 16)
          return _UVRSR_FAILED;

        if (vrs->demand_save_flags & DEMAND_SAVE_WMMXC)
          {
            /* Demand-save resisters for stage1.  */
            vrs->demand_save_flags &= ~DEMAND_SAVE_WMMXC;
            __gnu_Unwind_Save_WMMXC (&vrs->wmmxc);
          }

        /* Restore the registers from the stack.  Do this by saving the
           current WMMXC registers to a memory area, moving the in-memory
           values into that area, and restoring from the whole area.  */
        __gnu_Unwind_Save_WMMXC (&tmp);

        sp = (_uw *) vrs->core.r[R_SP];
        for (i = 0; i < 4; i++)
          if (discriminator & (1 << i))
            tmp.wc[i] = *(sp++);

        /* Set the new stack pointer.  */
        vrs->core.r[R_SP] = (_uw) sp;

        /* Reload the registers.  */
        __gnu_Unwind_Restore_WMMXC (&tmp);
      }
      return _UVRSR_OK;

    default:
      return _UVRSR_FAILED;
    }
}


/* Core unwinding functions.  */

/* Calculate the address encoded by a 31-bit self-relative offset at address
   P.  */
static inline _uw
selfrel_offset31 (const _uw *p)
{
  _uw offset;

  offset = *p;
  /* Sign extend to 32 bits.  */
  if (offset & (1 << 30))
    offset |= 1u << 31;
  else
    offset &= ~(1u << 31);

  return offset + (_uw) p;
}


/* Perform a binary search for RETURN_ADDRESS in TABLE.  The table contains
   NREC entries.  */

static const __EIT_entry *
search_EIT_table (const __EIT_entry * table, int nrec, _uw return_address)
{
  _uw next_fn;
  _uw this_fn;
  int n, left, right;

  if (nrec == 0)
    return (__EIT_entry *) 0;

  left = 0;
  right = nrec - 1;

  while (1)
    {
      n = (left + right) / 2;
      this_fn = selfrel_offset31 (&table[n].fnoffset);
      if (n != nrec - 1)
        next_fn = selfrel_offset31 (&table[n + 1].fnoffset) - 1;
      else
        next_fn = (_uw)0 - 1;

      if (return_address < this_fn)
        {
          if (n == left)
            return (__EIT_entry *) 0;
          right = n - 1;
        }
      else if (return_address <= next_fn)
        return &table[n];
      else
        left = n + 1;
    }
}

/* Find the exception index table eintry for the given address.
   Fill in the relevant fields of the UCB.
   Returns _URC_FAILURE if an error occurred, _URC_OK on success.  */

static _Unwind_Reason_Code
get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
{
  const __EIT_entry * eitp;
  int nrec;
  
  /* The return address is the address of the instruction following the
     call instruction (plus one in thumb mode).  If this was the last
     instruction in the function the address will lie in the following
     function.  Subtract 2 from the address so that it points within the call
     instruction itself.  */
  return_address -= 2;

  if (__gnu_Unwind_Find_exidx)
    {
      eitp = (const __EIT_entry *) __gnu_Unwind_Find_exidx (return_address,
                                                            &nrec);
      if (!eitp)
        {
          UCB_PR_ADDR (ucbp) = 0;
          return _URC_FAILURE;
        }
    }
  else
    {
      eitp = &__exidx_start;
      nrec = &__exidx_end - &__exidx_start;
    }

  eitp = search_EIT_table (eitp, nrec, return_address);

  if (!eitp)
    {
      UCB_PR_ADDR (ucbp) = 0;
      return _URC_FAILURE;
    }
  ucbp->pr_cache.fnstart = selfrel_offset31 (&eitp->fnoffset);

  /* Can this frame be unwound at all?  */
  if (eitp->content == EXIDX_CANTUNWIND)
    {
      UCB_PR_ADDR (ucbp) = 0;
      return _URC_END_OF_STACK;
    }

  /* Obtain the address of the "real" __EHT_Header word.  */

  if (eitp->content & uint32_highbit)
    {
      /* It is immediate data.  */
      ucbp->pr_cache.ehtp = (_Unwind_EHT_Header *)&eitp->content;
      ucbp->pr_cache.additional = 1;
    }
  else
    {
      /* The low 31 bits of the content field are a self-relative
         offset to an _Unwind_EHT_Entry structure.  */
      ucbp->pr_cache.ehtp =
        (_Unwind_EHT_Header *) selfrel_offset31 (&eitp->content);
      ucbp->pr_cache.additional = 0;
    }

  /* Discover the personality routine address.  */
  if (*ucbp->pr_cache.ehtp & (1u << 31))
    {
      /* One of the predefined standard routines.  */
      _uw idx = (*(_uw *) ucbp->pr_cache.ehtp >> 24) & 0xf;
      if (idx == 0)
        UCB_PR_ADDR (ucbp) = (_uw) &__aeabi_unwind_cpp_pr0;
      else if (idx == 1)
        UCB_PR_ADDR (ucbp) = (_uw) &__aeabi_unwind_cpp_pr1;
      else if (idx == 2)
        UCB_PR_ADDR (ucbp) = (_uw) &__aeabi_unwind_cpp_pr2;
      else
        { /* Failed */
          UCB_PR_ADDR (ucbp) = 0;
          return _URC_FAILURE;
        }
    } 
  else
    {
      /* Execute region offset to PR */
      UCB_PR_ADDR (ucbp) = selfrel_offset31 (ucbp->pr_cache.ehtp);
    }
  return _URC_OK;
}


/* Perform phase2 unwinding.  VRS is the initial virtual register state.  */

static void __attribute__((noreturn))
unwind_phase2 (_Unwind_Control_Block * ucbp, phase2_vrs * vrs)
{
  _Unwind_Reason_Code pr_result;

  do
    {
      /* Find the entry for this routine.  */
      if (get_eit_entry (ucbp, vrs->core.r[R_PC]) != _URC_OK)
        abort ();

      UCB_SAVED_CALLSITE_ADDR (ucbp) = vrs->core.r[R_PC];

      /* Call the pr to decide what to do.  */
      pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
        (_US_UNWIND_FRAME_STARTING, ucbp, (_Unwind_Context *) vrs);
    }
  while (pr_result == _URC_CONTINUE_UNWIND);
  
  if (pr_result != _URC_INSTALL_CONTEXT)
    abort();
  
  restore_core_regs (&vrs->core);
}

/* Perform phase2 forced unwinding.  */

static _Unwind_Reason_Code
unwind_phase2_forced (_Unwind_Control_Block *ucbp, phase2_vrs *entry_vrs,
                      int resuming)
{
  _Unwind_Stop_Fn stop_fn = (_Unwind_Stop_Fn) UCB_FORCED_STOP_FN (ucbp);
  void *stop_arg = (void *)UCB_FORCED_STOP_ARG (ucbp);
  _Unwind_Reason_Code pr_result = 0;
  /* We use phase1_vrs here even though we do not demand save, for the
     prev_sp field.  */
  phase1_vrs saved_vrs, next_vrs;

  /* Save the core registers.  */
  saved_vrs.core = entry_vrs->core;
  /* We don't need to demand-save the non-core registers, because we
     unwind in a single pass.  */
  saved_vrs.demand_save_flags = 0;

  /* Unwind until we reach a propagation barrier.  */
  do
    {
      _Unwind_State action;
      _Unwind_Reason_Code entry_code;
      _Unwind_Reason_Code stop_code;

      /* Find the entry for this routine.  */
      entry_code = get_eit_entry (ucbp, saved_vrs.core.r[R_PC]);

      if (resuming)
        {
          action = _US_UNWIND_FRAME_RESUME | _US_FORCE_UNWIND;
          resuming = 0;
        }
      else
        action = _US_UNWIND_FRAME_STARTING | _US_FORCE_UNWIND;

      if (entry_code == _URC_OK)
        {
          UCB_SAVED_CALLSITE_ADDR (ucbp) = saved_vrs.core.r[R_PC];

          next_vrs = saved_vrs;

          /* Call the pr to decide what to do.  */
          pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
            (action, ucbp, (void *) &next_vrs);

          saved_vrs.prev_sp = next_vrs.core.r[R_SP];
        }
      else
        {
          /* Treat any failure as the end of unwinding, to cope more
             gracefully with missing EH information.  Mixed EH and
             non-EH within one object will usually result in failure,
             because the .ARM.exidx tables do not indicate the end
             of the code to which they apply; but mixed EH and non-EH
             shared objects should return an unwind failure at the
             entry of a non-EH shared object.  */
          action |= _US_END_OF_STACK;

          saved_vrs.prev_sp = saved_vrs.core.r[R_SP];
        }

      stop_code = stop_fn (1, action, ucbp->exception_class, ucbp,
                           (void *)&saved_vrs, stop_arg);
      if (stop_code != _URC_NO_REASON)
        return _URC_FAILURE;

      if (entry_code != _URC_OK)
        return entry_code;

      saved_vrs = next_vrs;
    }
  while (pr_result == _URC_CONTINUE_UNWIND);

  if (pr_result != _URC_INSTALL_CONTEXT)
    {
      /* Some sort of failure has occurred in the pr and probably the
         pr returned _URC_FAILURE.  */
      return _URC_FAILURE;
    }

  restore_core_regs (&saved_vrs.core);
}

/* This is a very limited implementation of _Unwind_GetCFA.  It returns
   the stack pointer as it is about to be unwound, and is only valid
   while calling the stop function during forced unwinding.  If the
   current personality routine result is going to run a cleanup, this
   will not be the CFA; but when the frame is really unwound, it will
   be.  */

_Unwind_Word
_Unwind_GetCFA (_Unwind_Context *context)
{
  return ((phase1_vrs *) context)->prev_sp;
}

/* Perform phase1 unwinding.  UCBP is the exception being thrown, and
   entry_VRS is the register state on entry to _Unwind_RaiseException.  */

_Unwind_Reason_Code
__gnu_Unwind_RaiseException (_Unwind_Control_Block *, phase2_vrs *);

_Unwind_Reason_Code
__gnu_Unwind_RaiseException (_Unwind_Control_Block * ucbp,
                             phase2_vrs * entry_vrs)
{
  phase1_vrs saved_vrs;
  _Unwind_Reason_Code pr_result;

  /* Set the pc to the call site.  */
  entry_vrs->core.r[R_PC] = entry_vrs->core.r[R_LR];

  /* Save the core registers.  */
  saved_vrs.core = entry_vrs->core;
  /* Set demand-save flags.  */
  saved_vrs.demand_save_flags = ~(_uw) 0;
  
  /* Unwind until we reach a propagation barrier.  */
  do
    {
      /* Find the entry for this routine.  */
      if (get_eit_entry (ucbp, saved_vrs.core.r[R_PC]) != _URC_OK)
        return _URC_FAILURE;

      /* Call the pr to decide what to do.  */
      pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
        (_US_VIRTUAL_UNWIND_FRAME, ucbp, (void *) &saved_vrs);
    }
  while (pr_result == _URC_CONTINUE_UNWIND);

  /* We've unwound as far as we want to go, so restore the original
     register state.  */
  restore_non_core_regs (&saved_vrs);
  if (pr_result != _URC_HANDLER_FOUND)
    {
      /* Some sort of failure has occurred in the pr and probably the
         pr returned _URC_FAILURE.  */
      return _URC_FAILURE;
    }
  
  unwind_phase2 (ucbp, entry_vrs);
}

/* Resume unwinding after a cleanup has been run.  UCBP is the exception
   being thrown and ENTRY_VRS is the register state on entry to
   _Unwind_Resume.  */
_Unwind_Reason_Code
__gnu_Unwind_ForcedUnwind (_Unwind_Control_Block *,
                           _Unwind_Stop_Fn, void *, phase2_vrs *);

_Unwind_Reason_Code
__gnu_Unwind_ForcedUnwind (_Unwind_Control_Block *ucbp,
                           _Unwind_Stop_Fn stop_fn, void *stop_arg,
                           phase2_vrs *entry_vrs)
{
  UCB_FORCED_STOP_FN (ucbp) = (_uw) stop_fn;
  UCB_FORCED_STOP_ARG (ucbp) = (_uw) stop_arg;

  /* Set the pc to the call site.  */
  entry_vrs->core.r[R_PC] = entry_vrs->core.r[R_LR];

  return unwind_phase2_forced (ucbp, entry_vrs, 0);
}

_Unwind_Reason_Code
__gnu_Unwind_Resume (_Unwind_Control_Block *, phase2_vrs *);

_Unwind_Reason_Code
__gnu_Unwind_Resume (_Unwind_Control_Block * ucbp, phase2_vrs * entry_vrs)
{
  _Unwind_Reason_Code pr_result;

  /* Recover the saved address.  */
  entry_vrs->core.r[R_PC] = UCB_SAVED_CALLSITE_ADDR (ucbp);

  if (UCB_FORCED_STOP_FN (ucbp))
    {
      unwind_phase2_forced (ucbp, entry_vrs, 1);

      /* We can't return failure at this point.  */
      abort ();
    }

  /* Call the cached PR.  */
  pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
        (_US_UNWIND_FRAME_RESUME, ucbp, (_Unwind_Context *) entry_vrs);

  switch (pr_result)
    {
    case _URC_INSTALL_CONTEXT:
      /* Upload the registers to enter the landing pad.  */
      restore_core_regs (&entry_vrs->core);

    case _URC_CONTINUE_UNWIND:
      /* Continue unwinding the next frame.  */
      unwind_phase2 (ucbp, entry_vrs);

    default:
      abort ();
    }
}

_Unwind_Reason_Code
__gnu_Unwind_Resume_or_Rethrow (_Unwind_Control_Block *, phase2_vrs *);

_Unwind_Reason_Code
__gnu_Unwind_Resume_or_Rethrow (_Unwind_Control_Block * ucbp,
                                phase2_vrs * entry_vrs)
{
  if (!UCB_FORCED_STOP_FN (ucbp))
    return __gnu_Unwind_RaiseException (ucbp, entry_vrs);

  /* Set the pc to the call site.  */
  entry_vrs->core.r[R_PC] = entry_vrs->core.r[R_LR];
  /* Continue unwinding the next frame.  */
  return unwind_phase2_forced (ucbp, entry_vrs, 0);
}

/* Clean up an exception object when unwinding is complete.  */
void
_Unwind_Complete (_Unwind_Control_Block * ucbp __attribute__((unused)))
{
}


/* Get the _Unwind_Control_Block from an _Unwind_Context.  */

static inline _Unwind_Control_Block *
unwind_UCB_from_context (_Unwind_Context * context)
{
  return (_Unwind_Control_Block *) _Unwind_GetGR (context, R_IP);
}


/* Free an exception.  */

void
_Unwind_DeleteException (_Unwind_Exception * exc)
{
  if (exc->exception_cleanup)
    (*exc->exception_cleanup) (_URC_FOREIGN_EXCEPTION_CAUGHT, exc);
}


/* Perform stack backtrace through unwind data.  */
_Unwind_Reason_Code
__gnu_Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument,
                       phase2_vrs * entry_vrs);
_Unwind_Reason_Code
__gnu_Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument,
                       phase2_vrs * entry_vrs)
{
  phase1_vrs saved_vrs;
  _Unwind_Reason_Code code;

  _Unwind_Control_Block ucb;
  _Unwind_Control_Block *ucbp = &ucb;

  /* Set the pc to the call site.  */
  entry_vrs->core.r[R_PC] = entry_vrs->core.r[R_LR];

  /* Save the core registers.  */
  saved_vrs.core = entry_vrs->core;
  /* Set demand-save flags.  */
  saved_vrs.demand_save_flags = ~(_uw) 0;
  
  do
    {
      /* Find the entry for this routine.  */
      if (get_eit_entry (ucbp, saved_vrs.core.r[R_PC]) != _URC_OK)
        {
          code = _URC_FAILURE;
          break;
        }

      /* The dwarf unwinder assumes the context structure holds things
         like the function and LSDA pointers.  The ARM implementation
         caches these in the exception header (UCB).  To avoid
         rewriting everything we make the virtual IP register point at
         the UCB.  */
      _Unwind_SetGR((_Unwind_Context *)&saved_vrs, 12, (_Unwind_Ptr) ucbp);

      /* Call trace function.  */
      if ((*trace) ((_Unwind_Context *) &saved_vrs, trace_argument) 
          != _URC_NO_REASON)
        {
          code = _URC_FAILURE;
          break;
        }

      /* Call the pr to decide what to do.  */
      code = ((personality_routine) UCB_PR_ADDR (ucbp))
        (_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND, 
         ucbp, (void *) &saved_vrs);
    }
  while (code != _URC_END_OF_STACK
         && code != _URC_FAILURE);

  restore_non_core_regs (&saved_vrs);
  return code;
}


/* Common implementation for ARM ABI defined personality routines.
   ID is the index of the personality routine, other arguments are as defined
   by __aeabi_unwind_cpp_pr{0,1,2}.  */

static _Unwind_Reason_Code
__gnu_unwind_pr_common (_Unwind_State state,
                        _Unwind_Control_Block *ucbp,
                        _Unwind_Context *context,
                        int id)
{
  __gnu_unwind_state uws;
  _uw *data;
  _uw offset;
  _uw len;
  _uw rtti_count;
  int phase2_call_unexpected_after_unwind = 0;
  int in_range = 0;
  int forced_unwind = state & _US_FORCE_UNWIND;

  state &= _US_ACTION_MASK;

  data = (_uw *) ucbp->pr_cache.ehtp;
  uws.data = *(data++);
  uws.next = data;
  if (id == 0)
    {
      uws.data <<= 8;
      uws.words_left = 0;
      uws.bytes_left = 3;
    }
  else
    {
      uws.words_left = (uws.data >> 16) & 0xff;
      uws.data <<= 16;
      uws.bytes_left = 2;
      data += uws.words_left;
    }

  /* Restore the saved pointer.  */
  if (state == _US_UNWIND_FRAME_RESUME)
    data = (_uw *) ucbp->cleanup_cache.bitpattern[0];

  if ((ucbp->pr_cache.additional & 1) == 0)
    {
      /* Process descriptors.  */
      while (*data)
        {
          _uw addr;
          _uw fnstart;

          if (id == 2)
            {
              len = ((EHT32 *) data)->length;
              offset = ((EHT32 *) data)->offset;
              data += 2;
            }
          else
            {
              len = ((EHT16 *) data)->length;
              offset = ((EHT16 *) data)->offset;
              data++;
            }

          fnstart = ucbp->pr_cache.fnstart + (offset & ~1);
          addr = _Unwind_GetGR (context, R_PC);
          in_range = (fnstart <= addr && addr < fnstart + (len & ~1));

          switch (((offset & 1) << 1) | (len & 1))
            {
            case 0:
              /* Cleanup.  */
              if (state != _US_VIRTUAL_UNWIND_FRAME
                  && in_range)
                {
                  /* Cleanup in range, and we are running cleanups.  */
                  _uw lp;

                  /* Landing pad address is 31-bit pc-relative offset.  */
                  lp = selfrel_offset31 (data);
                  data++;
                  /* Save the exception data pointer.  */
                  ucbp->cleanup_cache.bitpattern[0] = (_uw) data;
                  if (!__cxa_begin_cleanup (ucbp))
                    return _URC_FAILURE;
                  /* Setup the VRS to enter the landing pad.  */
                  _Unwind_SetGR (context, R_PC, lp);
                  return _URC_INSTALL_CONTEXT;
                }
              /* Cleanup not in range, or we are in stage 1.  */
              data++;
              break;

            case 1:
              /* Catch handler.  */
              if (state == _US_VIRTUAL_UNWIND_FRAME)
                {
                  if (in_range)
                    {
                      /* Check for a barrier.  */
                      _uw rtti;
                      bool is_reference = (data[0] & uint32_highbit) != 0;
                      void *matched;

                      /* Check for no-throw areas.  */
                      if (data[1] == (_uw) -2)
                        return _URC_FAILURE;

                      /* The thrown object immediately follows the ECB.  */
                      matched = (void *)(ucbp + 1);
                      if (data[1] != (_uw) -1)
                        {
                          /* Match a catch specification.  */
                          rtti = _Unwind_decode_target2 ((_uw) &data[1]);
                          if (!__cxa_type_match (ucbp, (type_info *) rtti,
                                                 is_reference,
                                                 &matched))
                            matched = (void *)0;
                        }

                      if (matched)
                        {
                          ucbp->barrier_cache.sp =
                            _Unwind_GetGR (context, R_SP);
                          ucbp->barrier_cache.bitpattern[0] = (_uw) matched;
                          ucbp->barrier_cache.bitpattern[1] = (_uw) data;
                          return _URC_HANDLER_FOUND;
                        }
                    }
                  /* Handler out of range, or not matched.  */
                }
              else if (ucbp->barrier_cache.sp == _Unwind_GetGR (context, R_SP)
                       && ucbp->barrier_cache.bitpattern[1] == (_uw) data)
                {
                  /* Matched a previous propagation barrier.  */
                  _uw lp;

                  /* Setup for entry to the handler.  */
                  lp = selfrel_offset31 (data);
                  _Unwind_SetGR (context, R_PC, lp);
                  _Unwind_SetGR (context, 0, (_uw) ucbp);
                  return _URC_INSTALL_CONTEXT;
                }
              /* Catch handler not matched.  Advance to the next descriptor.  */
              data += 2;
              break;

            case 2:
              rtti_count = data[0] & 0x7fffffff;
              /* Exception specification.  */
              if (state == _US_VIRTUAL_UNWIND_FRAME)
                {
                  if (in_range && (!forced_unwind || !rtti_count))
                    {
                      /* Match against the exception specification.  */
                      _uw i;
                      _uw rtti;
                      void *matched;

                      for (i = 0; i < rtti_count; i++)
                        {
                          matched = (void *)(ucbp + 1);
                          rtti = _Unwind_decode_target2 ((_uw) &data[i + 1]);
                          if (__cxa_type_match (ucbp, (type_info *) rtti, 0,
                                                &matched))
                            break;
                        }

                      if (i == rtti_count)
                        {
                          /* Exception does not match the spec.  */
                          ucbp->barrier_cache.sp =
                            _Unwind_GetGR (context, R_SP);
                          ucbp->barrier_cache.bitpattern[0] = (_uw) matched;
                          ucbp->barrier_cache.bitpattern[1] = (_uw) data;
                          return _URC_HANDLER_FOUND;
                        }
                    }
                  /* Handler out of range, or exception is permitted.  */
                }
              else if (ucbp->barrier_cache.sp == _Unwind_GetGR (context, R_SP)
                       && ucbp->barrier_cache.bitpattern[1] == (_uw) data)
                {
                  /* Matched a previous propagation barrier.  */
                  _uw lp;
                  /* Record the RTTI list for __cxa_call_unexpected.  */
                  ucbp->barrier_cache.bitpattern[1] = rtti_count;
                  ucbp->barrier_cache.bitpattern[2] = 0;
                  ucbp->barrier_cache.bitpattern[3] = 4;
                  ucbp->barrier_cache.bitpattern[4] = (_uw) &data[1];

                  if (data[0] & uint32_highbit)
                    {
                      data += rtti_count + 1;
                      /* Setup for entry to the handler.  */
                      lp = selfrel_offset31 (data);
                      data++;
                      _Unwind_SetGR (context, R_PC, lp);
                      _Unwind_SetGR (context, 0, (_uw) ucbp);
                      return _URC_INSTALL_CONTEXT;
                    }
                  else
                    phase2_call_unexpected_after_unwind = 1;
                }
              if (data[0] & uint32_highbit)
                data++;
              data += rtti_count + 1;
              break;

            default:
              /* Should never happen.  */
              return _URC_FAILURE;
            }
          /* Finished processing this descriptor.  */
        }
    }

  if (__gnu_unwind_execute (context, &uws) != _URC_OK)
    return _URC_FAILURE;

  if (phase2_call_unexpected_after_unwind)
    {
      /* Enter __cxa_unexpected as if called from the call site.  */
      _Unwind_SetGR (context, R_LR, _Unwind_GetGR (context, R_PC));
      _Unwind_SetGR (context, R_PC, (_uw) &__cxa_call_unexpected);
      return _URC_INSTALL_CONTEXT;
    }

  return _URC_CONTINUE_UNWIND;
}


/* ABI defined personality routine entry points.  */

_Unwind_Reason_Code
__aeabi_unwind_cpp_pr0 (_Unwind_State state,
                        _Unwind_Control_Block *ucbp,
                        _Unwind_Context *context)
{
  return __gnu_unwind_pr_common (state, ucbp, context, 0);
}

_Unwind_Reason_Code
__aeabi_unwind_cpp_pr1 (_Unwind_State state,
                        _Unwind_Control_Block *ucbp,
                        _Unwind_Context *context)
{
  return __gnu_unwind_pr_common (state, ucbp, context, 1);
}

_Unwind_Reason_Code
__aeabi_unwind_cpp_pr2 (_Unwind_State state,
                        _Unwind_Control_Block *ucbp,
                        _Unwind_Context *context)
{
  return __gnu_unwind_pr_common (state, ucbp, context, 2);
}