1  /* DWARF2 EH unwinding support for PowerPC64 FreeBSD.
       2     Copyright (C) 2012-2023 Free Software Foundation, Inc.
       3  
       4     This file is part of GCC.
       5  
       6     GCC is free software; you can redistribute it and/or modify it
       7     under the terms of the GNU General Public License as published
       8     by the Free Software Foundation; either version 3, or (at your
       9     option) any later version.
      10  
      11     GCC is distributed in the hope that it will be useful, but WITHOUT
      12     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      13     or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
      14     License for more details.
      15  
      16     Under Section 7 of GPL version 3, you are granted additional
      17     permissions described in the GCC Runtime Library Exception, version
      18     3.1, as published by the Free Software Foundation.
      19  
      20     You should have received a copy of the GNU General Public License and
      21     a copy of the GCC Runtime Library Exception along with this program;
      22     see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23     <http://www.gnu.org/licenses/>.  */
      24  
      25  #define R_LR		65
      26  
      27  #define MD_FROB_UPDATE_CONTEXT frob_update_context
      28  
      29  static void
      30  frob_update_context (struct _Unwind_Context *context,
      31  		     _Unwind_FrameState *fs ATTRIBUTE_UNUSED)
      32  {
      33    const unsigned int *pc = (const unsigned int *) context->ra;
      34  
      35  #ifdef __powerpc64__
      36    if (fs->regs.how[2] == REG_UNSAVED)
      37      {
      38        /* If the current unwind info (FS) does not contain explicit info
      39  	 saving R2, then we have to do a minor amount of code reading to
      40  	 figure out if it was saved.  The big problem here is that the
      41  	 code that does the save/restore is generated by the linker, so
      42  	 we have no good way to determine at compile time what to do.  */
      43        if (pc[0] == 0xF8410028
      44  	  || ((pc[0] & 0xFFFF0000) == 0x3D820000
      45  	      && pc[1] == 0xF8410028))
      46  	{
      47  	  /* We are in a plt call stub or r2 adjusting long branch stub,
      48  	     before r2 has been saved.  Keep REG_UNSAVED.  */
      49  	}
      50        else
      51  	{
      52  	  unsigned int *insn
      53  	    = (unsigned int *) _Unwind_GetGR (context, R_LR);
      54  	  if (insn && *insn == 0xE8410028)
      55  	    _Unwind_SetGRPtr (context, 2, context->cfa + 40);
      56  	  else if (pc[0] == 0x4E800421
      57  		   && pc[1] == 0xE8410028)
      58  	    {
      59  	      /* We are at the bctrl instruction in a call via function
      60  		 pointer.  gcc always emits the load of the new R2 just
      61  		 before the bctrl so this is the first and only place
      62  		 we need to use the stored R2.  */
      63  	      _Unwind_Word sp = _Unwind_GetGR (context, 1);
      64  	      _Unwind_SetGRPtr (context, 2, (void *)(sp + 40));
      65  	    }
      66  	}
      67      }
      68  #endif
      69  }