1  /* DWARF2 EH unwinding support for Alpha Linux.
       2     Copyright (C) 2004-2023 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
       7  it under the terms of the GNU General Public License as published by
       8  the Free Software Foundation; either version 3, or (at your option)
       9  any later version.
      10  
      11  GCC is distributed in the hope that it will be useful,
      12  but WITHOUT ANY WARRANTY; without even the implied warranty of
      13  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14  GNU General Public 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  #ifndef inhibit_libc
      26  /* Do code reading to identify a signal frame, and set the frame
      27     state data appropriately.  See unwind-dw2.c for the structs.  */
      28  
      29  #include <signal.h>
      30  #include <sys/ucontext.h>
      31  
      32  #define MD_FALLBACK_FRAME_STATE_FOR alpha_fallback_frame_state
      33  
      34  static _Unwind_Reason_Code
      35  alpha_fallback_frame_state (struct _Unwind_Context *context,
      36  			    _Unwind_FrameState *fs)
      37  {
      38    unsigned int *pc = context->ra;
      39    struct sigcontext *sc;
      40    long new_cfa;
      41    int i;
      42  
      43    if (pc[0] != 0x47fe0410		/* mov $30,$16 */
      44        || pc[2] != 0x00000083)		/* callsys */
      45      return _URC_END_OF_STACK;
      46    if (context->cfa == 0)
      47      return _URC_END_OF_STACK;
      48    if (pc[1] == 0x201f0067)		/* lda $0,NR_sigreturn */
      49      sc = context->cfa;
      50    else if (pc[1] == 0x201f015f)		/* lda $0,NR_rt_sigreturn */
      51      {
      52        struct rt_sigframe {
      53  	siginfo_t info;
      54  	ucontext_t uc;
      55        } *rt_ = context->cfa;
      56        /* The void * cast is necessary to avoid an aliasing warning.
      57           The aliasing warning is correct, but should not be a problem
      58           because it does not alias anything.  */
      59        sc = (struct sigcontext *) (void *) &rt_->uc.uc_mcontext;
      60      }
      61    else
      62      return _URC_END_OF_STACK;
      63  
      64    new_cfa = sc->sc_regs[30];
      65    fs->regs.cfa_how = CFA_REG_OFFSET;
      66    fs->regs.cfa_reg = 30;
      67    fs->regs.cfa_offset = new_cfa - (long) context->cfa;
      68    for (i = 0; i < 30; ++i)
      69      {
      70        fs->regs.how[i] = REG_SAVED_OFFSET;
      71        fs->regs.reg[i].loc.offset
      72  	= (long) &sc->sc_regs[i] - new_cfa;
      73      }
      74    for (i = 0; i < 31; ++i)
      75      {
      76        fs->regs.how[i+32] = REG_SAVED_OFFSET;
      77        fs->regs.reg[i+32].loc.offset
      78  	= (long) &sc->sc_fpregs[i] - new_cfa;
      79      }
      80    fs->regs.how[64] = REG_SAVED_OFFSET;
      81    fs->regs.reg[64].loc.offset = (long)&sc->sc_pc - new_cfa;
      82    fs->retaddr_column = 64;
      83    fs->signal_frame = 1;
      84  
      85    return _URC_NO_REASON;
      86  }
      87  
      88  #define MD_FROB_UPDATE_CONTEXT alpha_frob_update_context
      89  
      90  /* Fix up for signal handlers that don't have S flag set.  */
      91  
      92  static void
      93  alpha_frob_update_context (struct _Unwind_Context *context,
      94  			   _Unwind_FrameState *fs ATTRIBUTE_UNUSED)
      95  {
      96    unsigned int *pc = context->ra;
      97  
      98    if (pc[0] == 0x47fe0410		/* mov $30,$16 */
      99        && pc[2] == 0x00000083		/* callsys */
     100        && (pc[1] == 0x201f0067		/* lda $0,NR_sigreturn */
     101  	  || pc[1] == 0x201f015f))	/* lda $0,NR_rt_sigreturn */
     102      _Unwind_SetSignalFrame (context, 1);
     103  }
     104  #endif