libgcc/config/arm/pr-support.c

/* ARM EABI compliant unwinding routines
   Copyright (C) 2004-2023 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/>.  */

#pragma GCC target ("general-regs-only")
#include "unwind.h"

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

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

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

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

void __attribute__((weak)) __cxa_call_unexpected(_Unwind_Control_Block *ucbp);

/* Unwind descriptors.  */

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

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

/* Calculate the address encoded by a 31-bit self-relative offset at address
   P.  Copy of routine in unwind-arm.c.  */

static inline _uw
selfrel_offset31 (const _uw *p)
{
  _uw offset;

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

  return offset + (_uw) p;
}


/* Personality routine helper functions.  */

#define CODE_FINISH (0xb0)

/* Return the next byte of unwinding information, or CODE_FINISH if there is
   no data remaining.  */
static inline _uw8
next_unwind_byte (__gnu_unwind_state * uws)
{
  _uw8 b;

  if (uws->bytes_left == 0)
    {
      /* Load another word */
      if (uws->words_left == 0)
	return CODE_FINISH; /* Nothing left.  */
      uws->words_left--;
      uws->data = *(uws->next++);
      uws->bytes_left = 3;
    }
  else
    uws->bytes_left--;

  /* Extract the most significant byte.  */
  b = (uws->data >> 24) & 0xff;
  uws->data <<= 8;
  return b;
}

/* Execute the unwinding instructions described by UWS.  */
_Unwind_Reason_Code
__gnu_unwind_execute (_Unwind_Context * context, __gnu_unwind_state * uws)
{
  _uw op;
  int set_pc;
#if defined(TARGET_HAVE_PACBTI)
  int set_pac = 0;
  int set_pac_sp = 0;
#endif
  _uw reg;
  _uw sp;

  set_pc = 0;
  for (;;)
    {
      op = next_unwind_byte (uws);
      if (op == CODE_FINISH)
	{
	  /* When we reach end, we have to authenticate R12 we just popped
	     earlier.

	     Note: while the check provides additional security against a
	     corrupted unwind chain, it isn't essential for correct unwinding
	     of an uncorrupted chain.  */
#if defined(TARGET_HAVE_PACBTI)
	  if (set_pac)
	    {
	      _uw lr;
	      _uw pac;
	      if (!set_pac_sp)
		_Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32,
				 &sp);
	      _Unwind_VRS_Get (context, _UVRSC_CORE, R_LR, _UVRSD_UINT32, &lr);
	      _Unwind_VRS_Get (context, _UVRSC_PAC, R_IP,
			       _UVRSD_UINT32, &pac);
	      __asm__ __volatile__
		("autg %0, %1, %2" : : "r"(pac), "r"(lr), "r"(sp) :);
	    }
#endif

	  /* If we haven't already set pc then copy it from lr.  */
	  if (!set_pc)
	    {
	      _Unwind_VRS_Get (context, _UVRSC_CORE, R_LR, _UVRSD_UINT32,
			       &reg);
	      _Unwind_VRS_Set (context, _UVRSC_CORE, R_PC, _UVRSD_UINT32,
			       &reg);
	      set_pc = 1;
	    }
	  /* Drop out of the loop.  */
	  break;
	}
      if ((op & 0x80) == 0)
	{
	  /* vsp = vsp +- (imm6 << 2 + 4).  */
	  _uw offset;

	  offset = ((op & 0x3f) << 2) + 4;
	  _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32, &reg);
	  if (op & 0x40)
	    reg -= offset;
	  else
	    reg += offset;
	  _Unwind_VRS_Set (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32, &reg);
	  continue;
	}
      
      if ((op & 0xf0) == 0x80)
	{
	  op = (op << 8) | next_unwind_byte (uws);
	  if (op == 0x8000)
	    {
	      /* Refuse to unwind.  */
	      return _URC_FAILURE;
	    }
	  /* Pop r4-r15 under mask.  */
	  op = (op << 4) & 0xfff0;
	  if (_Unwind_VRS_Pop (context, _UVRSC_CORE, op, _UVRSD_UINT32)
	      != _UVRSR_OK)
	    return _URC_FAILURE;
	  if (op & (1 << R_PC))
	    set_pc = 1;
	  continue;
	}
      if ((op & 0xf0) == 0x90)
	{
	  op &= 0xf;
	  if (op == 13 || op == 15)
	    /* Reserved.  */
	    return _URC_FAILURE;
	  /* vsp = r[nnnn].  */
	  _Unwind_VRS_Get (context, _UVRSC_CORE, op, _UVRSD_UINT32, &reg);
	  _Unwind_VRS_Set (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32, &reg);
	  continue;
	}
      if ((op & 0xf0) == 0xa0)
	{
	  /* Pop r4-r[4+nnn], [lr].  */
	  _uw mask;
	  
	  mask = (0xff0 >> (7 - (op & 7))) & 0xff0;
	  if (op & 8)
	    mask |= (1 << R_LR);
	  if (_Unwind_VRS_Pop (context, _UVRSC_CORE, mask, _UVRSD_UINT32)
	      != _UVRSR_OK)
	    return _URC_FAILURE;
	  continue;
	}
      if ((op & 0xf0) == 0xb0)
	{
	  /* op == 0xb0 already handled.  */
	  if (op == 0xb1)
	    {
	      op = next_unwind_byte (uws);
	      if (op == 0 || ((op & 0xf0) != 0))
		/* Spare.  */
		return _URC_FAILURE;
	      /* Pop r0-r4 under mask.  */
	      if (_Unwind_VRS_Pop (context, _UVRSC_CORE, op, _UVRSD_UINT32)
		  != _UVRSR_OK)
		return _URC_FAILURE;
	      continue;
	    }
	  if (op == 0xb2)
	    {
	      /* vsp = vsp + 0x204 + (uleb128 << 2).  */
	      int shift;

	      _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32,
			       &reg);
	      op = next_unwind_byte (uws);
	      shift = 2;
	      while (op & 0x80)
		{
		  reg += ((op & 0x7f) << shift);
		  shift += 7;
		  op = next_unwind_byte (uws);
		}
	      reg += ((op & 0x7f) << shift) + 0x204;
	      _Unwind_VRS_Set (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32,
			       &reg);
	      continue;
	    }
	  if (op == 0xb3)
	    {
	      /* Pop VFP registers with fldmx.  */
	      op = next_unwind_byte (uws);
	      op = ((op & 0xf0) << 12) | ((op & 0xf) + 1);
	      if (_Unwind_VRS_Pop (context, _UVRSC_VFP, op, _UVRSD_VFPX)
		  != _UVRSR_OK)
		return _URC_FAILURE;
	      continue;
	    }
	  /* Pop PAC off the stack into VRS pseudo.pac.  */
	  if (op == 0xb4)
	    {
	      if (_Unwind_VRS_Pop (context, _UVRSC_PAC, 0, _UVRSD_UINT32)
		  != _UVRSR_OK)
		return _URC_FAILURE;
#if defined(TARGET_HAVE_PACBTI)
	      set_pac = 1;
#endif
	      continue;
	    }

	  /* Use current VSP as modifier in PAC validation.  */
	  if (op == 0xb5)
	    {
	      _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32, &sp);
#if defined(TARGET_HAVE_PACBTI)
	      set_pac_sp = 1;
#endif
	      continue;
	    }

	  if ((op & 0xfc) == 0xb4)  /* Obsolete FPA.  */
	    return _URC_FAILURE;

	  /* op & 0xf8 == 0xb8.  */
	  /* Pop VFP D[8]-D[8+nnn] with fldmx.  */
	  op = 0x80000 | ((op & 7) + 1);
	  if (_Unwind_VRS_Pop (context, _UVRSC_VFP, op, _UVRSD_VFPX)
	      != _UVRSR_OK)
	    return _URC_FAILURE;
	  continue;
	}
      if ((op & 0xf0) == 0xc0)
	{
	  if (op == 0xc6)
	    {
	      /* Pop iWMMXt D registers.  */
	      op = next_unwind_byte (uws);
	      op = ((op & 0xf0) << 12) | ((op & 0xf) + 1);
	      if (_Unwind_VRS_Pop (context, _UVRSC_WMMXD, op, _UVRSD_UINT64)
		  != _UVRSR_OK)
		return _URC_FAILURE;
	      continue;
	    }
	  if (op == 0xc7)
	    {
	      op = next_unwind_byte (uws);
	      if (op == 0 || (op & 0xf0) != 0)
		/* Spare.  */
		return _URC_FAILURE;
	      /* Pop iWMMXt wCGR{3,2,1,0} under mask.  */
	      if (_Unwind_VRS_Pop (context, _UVRSC_WMMXC, op, _UVRSD_UINT32)
		  != _UVRSR_OK)
		return _URC_FAILURE;
	      continue;
	    }
	  if ((op & 0xf8) == 0xc0)
	    {
	      /* Pop iWMMXt wR[10]-wR[10+nnn].  */
	      op = 0xa0000 | ((op & 0xf) + 1);
	      if (_Unwind_VRS_Pop (context, _UVRSC_WMMXD, op, _UVRSD_UINT64)
		  != _UVRSR_OK)
		return _URC_FAILURE;
	      continue;
	    }
	  if (op == 0xc8)
	    {
              /* Pop VFPv3 registers D[16+ssss]-D[16+ssss+cccc] with vldm.  */
              op = next_unwind_byte (uws);
              op = (((op & 0xf0) + 16) << 12) | ((op & 0xf) + 1);
              if (_Unwind_VRS_Pop (context, _UVRSC_VFP, op, _UVRSD_DOUBLE)
                  != _UVRSR_OK)
                return _URC_FAILURE;
              continue;
	    }
	  if (op == 0xc9)
	    {
	      /* Pop VFP registers with fldmd.  */
	      op = next_unwind_byte (uws);
	      op = ((op & 0xf0) << 12) | ((op & 0xf) + 1);
	      if (_Unwind_VRS_Pop (context, _UVRSC_VFP, op, _UVRSD_DOUBLE)
		  != _UVRSR_OK)
		return _URC_FAILURE;
	      continue;
	    }
	  /* Spare.  */
	  return _URC_FAILURE;
	}
      if ((op & 0xf8) == 0xd0)
	{
	  /* Pop VFP D[8]-D[8+nnn] with fldmd.  */
	  op = 0x80000 | ((op & 7) + 1);
	  if (_Unwind_VRS_Pop (context, _UVRSC_VFP, op, _UVRSD_DOUBLE)
	      != _UVRSR_OK)
	    return _URC_FAILURE;
	  continue;
	}
      /* Spare.  */
      return _URC_FAILURE;
    }
  return _URC_OK;
}


/* Execute the unwinding instructions associated with a frame.  UCBP and
   CONTEXT are the current exception object and virtual CPU state
   respectively.  */

_Unwind_Reason_Code
__gnu_unwind_frame (_Unwind_Control_Block * ucbp, _Unwind_Context * context)
{
  _uw *ptr;
  __gnu_unwind_state uws;

  ptr = (_uw *) ucbp->pr_cache.ehtp;
  /* Skip over the personality routine address.  */
  ptr++;
  /* Setup the unwinder state.  */
  uws.data = (*ptr) << 8;
  uws.next = ptr + 1;
  uws.bytes_left = 3;
  uws.words_left = ((*ptr) >> 24) & 0xff;

  return __gnu_unwind_execute (context, &uws);
}

/* 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);
}

/* Get the start address of the function being unwound.  */

_Unwind_Ptr
_Unwind_GetRegionStart (_Unwind_Context * context)
{
  _Unwind_Control_Block *ucbp;

  ucbp = unwind_UCB_from_context (context);
  return (_Unwind_Ptr) ucbp->pr_cache.fnstart;
}

/* Find the Language specific exception data.  */

void *
_Unwind_GetLanguageSpecificData (_Unwind_Context * context)
{
  _Unwind_Control_Block *ucbp;
  _uw *ptr;

  /* Get a pointer to the exception table entry.  */
  ucbp = unwind_UCB_from_context (context);
  ptr = (_uw *) ucbp->pr_cache.ehtp;
  /* Skip the personality routine address.  */
  ptr++;
  /* Skip the unwind opcodes.  */
  ptr += (((*ptr) >> 24) & 0xff) + 1;

  return ptr;
}


/* These two should never be used.  */

_Unwind_Ptr
_Unwind_GetDataRelBase (_Unwind_Context *context __attribute__ ((unused)))
{
  abort ();
}

_Unwind_Ptr
_Unwind_GetTextRelBase (_Unwind_Context *context __attribute__ ((unused)))
{
  abort ();
}