libgcc/config/xtensa/linux-unwind.h

   1 /* DWARF2 EH unwinding support for Xtensa.
   2    Copyright (C) 2008-2020 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 /* Do code reading to identify a signal frame, and set the frame
  26    state data appropriately.  See unwind-dw2-xtensa.c for the structs.
  27    Don't use this at all if inhibit_libc is used.  */
  28
  29 #ifndef inhibit_libc
  30
  31 #include <signal.h>
  32 #include <sys/ucontext.h>
  33
  34 /* Encoded bytes for Xtensa instructions:
  35         movi a2, __NR_rt_sigreturn
  36         syscall
  37         entry (first byte only)
  38    Some of the bytes are endian-dependent.  */
  39
  40 #define MOVI_BYTE0 0x22
  41 #define MOVI_BYTE2 225 /* __NR_rt_sigreturn */
  42 #define SYSC_BYTE0 0
  43 #define SYSC_BYTE2 0
  44
  45 #ifdef __XTENSA_EB__
  46 #define MOVI_BYTE1 0x0a
  47 #define SYSC_BYTE1 0x05
  48 #define ENTRY_BYTE 0x6c
  49 #else
  50 #define MOVI_BYTE1 0xa0
  51 #define SYSC_BYTE1 0x50
  52 #define ENTRY_BYTE 0x36
  53 #endif
  54
  55 #define MD_FALLBACK_FRAME_STATE_FOR xtensa_fallback_frame_state
  56
  57 static _Unwind_Reason_Code
  58 xtensa_fallback_frame_state (struct _Unwind_Context *context,
  59                              _Unwind_FrameState *fs)
  60 {
  61   unsigned char *pc = context->ra;
  62   struct sigcontext *sc;
  63 #if defined(__XTENSA_CALL0_ABI__)
  64   _Unwind_Ptr new_cfa;
  65   int i;
  66 #endif
  67
  68   struct rt_sigframe {
  69     siginfo_t info;
  70     ucontext_t uc;
  71   } *rt_;
  72
  73   /* movi a2, __NR_rt_sigreturn; syscall */
  74   if (pc[0] != MOVI_BYTE0
  75       || pc[1] != MOVI_BYTE1
  76       || pc[2] != MOVI_BYTE2
  77       || pc[3] != SYSC_BYTE0
  78       || pc[4] != SYSC_BYTE1
  79       || pc[5] != SYSC_BYTE2)
  80     return _URC_END_OF_STACK;
  81
  82 #if defined(__XTENSA_WINDOWED_ABI__)
  83   rt_ = context->sp;
  84   sc = &rt_->uc.uc_mcontext;
  85   fs->signal_regs = (_Unwind_Word *) sc->sc_a;
  86
  87   /* If the signal arrived just before an ENTRY instruction, find the return
  88      address and pretend the signal arrived before executing the CALL.  */
  89   if (*(unsigned char *) sc->sc_pc == ENTRY_BYTE)
  90    {
  91      unsigned callinc = (sc->sc_ps >> 16) & 3;
  92      fs->signal_ra = ((sc->sc_a[callinc << 2] & XTENSA_RA_FIELD_MASK)
  93                       | context->ra_high_bits) - 3;
  94    }
  95   else
  96     fs->signal_ra = sc->sc_pc;
  97 #elif defined(__XTENSA_CALL0_ABI__)
  98   rt_ = context->cfa;
  99   sc = &rt_->uc.uc_mcontext;
 100
 101   new_cfa = (_Unwind_Ptr) sc;
 102   fs->regs.cfa_how = CFA_REG_OFFSET;
 103   fs->regs.cfa_reg = __LIBGCC_STACK_POINTER_REGNUM__;
 104   fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
 105
 106   for (i = 0; i < 16; i++)
 107     {
 108       fs->regs.reg[i].how = REG_SAVED_OFFSET;
 109       fs->regs.reg[i].loc.offset = (_Unwind_Ptr) &(sc->sc_a[i]) - new_cfa;
 110     }
 111
 112   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how =
 113     REG_SAVED_VAL_OFFSET;
 114   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset =
 115     (_Unwind_Ptr) (sc->sc_pc) - new_cfa;
 116   fs->retaddr_column = __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__;
 117 #else
 118 #error Unsupported Xtensa ABI
 119 #endif
 120
 121   fs->signal_frame = 1;
 122   return _URC_NO_REASON;
 123 }
 124
 125
 126 #endif /* ifdef inhibit_libc  */