1  /* DWARF2 EH unwinding support for ARC Linux.
       2     Copyright (C) 2017-2023 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 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, 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
      21     and a copy of the GCC Runtime Library Exception along with this
      22     program; see the files COPYING3 and COPYING.RUNTIME respectively.
      23     If not, see <http://www.gnu.org/licenses/>.  */
      24  
      25  /* This order is defined by a structure in the kernel, in file
      26     arch/arc/kernel/signal.c.  */
      27  
      28  #define REGISTER_IN_STACK(REG_NAME, ID) \
      29    REG_NAME,
      30  enum registers_stack_order {
      31    REGISTER_STACK_ORDER_START = -1,
      32    #include "config/arc/linux-unwind-reg.def"
      33    REGISTER_STACK_ORDER_SIZE,
      34  };
      35  
      36  struct register_position {
      37    int reg_id;
      38    int offset_in_stack;
      39  };
      40  #undef REGISTER_IN_STACK
      41  
      42  #define REGISTER_SIZE_IN_WORDS 4
      43  #define REGISTER_IN_STACK(REG_NAME, ID) (int) ID,
      44  int
      45  register_id_for_index[REGISTER_STACK_ORDER_SIZE] = {
      46    #include "config/arc/linux-unwind-reg.def"
      47  };
      48  #undef REGISTER_IN_STACK
      49  
      50  #ifndef inhibit_libc
      51  /* Do code reading to identify a signal frame, and set the frame
      52     state data appropriately.  See unwind-dw2.c for the structs.  */
      53  
      54  #include <signal.h>
      55  #include <asm/unistd.h>
      56  
      57  /*
      58  00010edc <__default_rt_sa_restorer>:
      59     10edc:	208a 12c2		mov     r8,139
      60     10ee0:	781e			trap_s  0
      61     10ee2:	7ee0			j_s     [blink]
      62  */
      63  
      64  #if __BIG_ENDIAN__
      65  #define MOV_R8_139	  0x8a20c212
      66  #define TRAP_S_J_S_BLINK  0x1e78e07e
      67  #define SWI		  0x6f223f00
      68  #elif __LITTLE_ENDIAN__
      69  #define MOV_R8_139	  0x12c2208a
      70  #define TRAP_S_J_S_BLINK  0x7ee0781e
      71  #define SWI		  0x003f226f
      72  #endif
      73  
      74  #define MD_FALLBACK_FRAME_STATE_FOR arc_fallback_frame_state
      75  
      76  static __attribute__((noinline)) _Unwind_Reason_Code
      77  arc_fallback_frame_state (struct _Unwind_Context *context,
      78  			   _Unwind_FrameState *fs)
      79  {
      80    struct rt_sigframe {
      81      siginfo_t info;
      82      ucontext_t uc;
      83      unsigned int sigret_magic;
      84    };
      85  
      86    struct rt_sigframe *rt_;
      87    u_int32_t *pc = (u_int32_t *) context->ra;
      88    struct sigcontext *sc;
      89    _Unwind_Ptr new_cfa;
      90    int i;
      91  
      92  #ifdef __ARC700__
      93    if (pc[1] != SWI)
      94      return _URC_END_OF_STACK;
      95  #else
      96    if (pc[1] != TRAP_S_J_S_BLINK)
      97      return _URC_END_OF_STACK;
      98  #endif
      99  
     100    if (pc[0] == MOV_R8_139)
     101      {
     102        rt_ = context->cfa;
     103        sc = &rt_->uc.uc_mcontext;
     104      }
     105    else
     106      return _URC_END_OF_STACK;
     107  
     108    new_cfa = (_Unwind_Ptr) sc;
     109    fs->regs.cfa_how = CFA_REG_OFFSET;
     110    fs->regs.cfa_reg = __LIBGCC_STACK_POINTER_REGNUM__;
     111    fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
     112  
     113    unsigned long *regs = &sc->regs.scratch.bta;
     114    for (i = 0; i < REGISTER_STACK_ORDER_SIZE; i++)
     115      {
     116        if (register_id_for_index[i] == -1)
     117  	continue;
     118        fs->regs.how[register_id_for_index[i]] = REG_SAVED_OFFSET;
     119        fs->regs.reg[register_id_for_index[i]].loc.offset
     120  	= ((_Unwind_Ptr) &(regs[i])) - new_cfa;
     121      }
     122  
     123    fs->signal_frame = 1;
     124    fs->retaddr_column = __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__;
     125    fs->regs.how[fs->retaddr_column] = REG_SAVED_VAL_OFFSET;
     126    fs->regs.reg[fs->retaddr_column].loc.offset =
     127      ((_Unwind_Ptr) (regs[ret])) - new_cfa;
     128  
     129    return _URC_NO_REASON;
     130  }
     131  #endif
     132  
     133  #define MD_FROB_UPDATE_CONTEXT arc_frob_update_context
     134  /* Save fp register for unwinding to work.  */
     135  
     136  static void
     137  arc_frob_update_context (struct _Unwind_Context *context,
     138  			 _Unwind_FrameState *fs)
     139  {
     140    _Unwind_Word fp_val;
     141    asm ("mov %0,fp" : "=r" (fp_val));
     142  
     143    switch (fs->regs.how[27])
     144      {
     145      case REG_UNSAVED:
     146      case REG_UNDEFINED:
     147        if (context->reg[27] == NULL)
     148  	_Unwind_SetGRValue (context, 27, fp_val);
     149        break;
     150  
     151      default:
     152        break;
     153      }
     154  }