libgcc/config/s390/linux-unwind.h

   1 /* DWARF2 EH unwinding support for S/390 Linux.
   2    Copyright (C) 2004-2020 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 it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 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.c for the structs.  */
  27
  28 #define MD_FALLBACK_FRAME_STATE_FOR s390_fallback_frame_state
  29
  30 static _Unwind_Reason_Code
  31 s390_fallback_frame_state (struct _Unwind_Context *context,
  32                            _Unwind_FrameState *fs)
  33 {
  34   static const unsigned char dwarf_to_fpr_map[16] =
  35     { 0, 2, 4, 6, 1, 3, 5, 7, 8, 10, 12, 14, 9, 11, 13, 15 };
  36   unsigned char *pc = context->ra;
  37   long new_cfa;
  38   int i;
  39
  40   typedef struct
  41   {
  42     unsigned long psw_mask;
  43     unsigned long psw_addr;
  44     unsigned long gprs[16];
  45     unsigned int  acrs[16];
  46     unsigned int  fpc;
  47     unsigned int  __pad;
  48     double        fprs[16];
  49   } __attribute__ ((__aligned__ (8))) sigregs_;
  50
  51   sigregs_ *regs;
  52   int *signo;
  53
  54   /* svc $__NR_sigreturn or svc $__NR_rt_sigreturn  */
  55   if (pc[0] != 0x0a || (pc[1] != 119 && pc[1] != 173))
  56     return _URC_END_OF_STACK;
  57
  58   /* Legacy frames:
  59        old signal mask (8 bytes)
  60        pointer to sigregs (8 bytes) - points always to next location
  61        sigregs
  62        retcode
  63      This frame layout was used on kernels < 2.6.9 for non-RT frames,
  64      and on kernels < 2.4.13 for RT frames as well.  Note that we need
  65      to look at RA to detect this layout -- this means that if you use
  66      sa_restorer to install a different signal restorer on a legacy
  67      kernel, unwinding from signal frames will not work.  */
  68   if (context->ra == context->cfa + 16 + sizeof (sigregs_))
  69     {
  70       regs = (sigregs_ *)(context->cfa + 16);
  71       signo = NULL;
  72     }
  73
  74   /* New-style RT frame:
  75      retcode + alignment (8 bytes)
  76      siginfo (128 bytes)
  77      ucontext (contains sigregs)  */
  78   else if (pc[1] == 173 /* __NR_rt_sigreturn */)
  79     {
  80       struct ucontext_
  81       {
  82         unsigned long     uc_flags;
  83         struct ucontext_ *uc_link;
  84         unsigned long     uc_stack[3];
  85         sigregs_          uc_mcontext;
  86       } *uc = context->cfa + 8 + 128;
  87
  88       regs = &uc->uc_mcontext;
  89       signo = context->cfa + sizeof(long);
  90     }
  91
  92   /* New-style non-RT frame:
  93      old signal mask (8 bytes)
  94      pointer to sigregs (followed by signal number)  */
  95   else
  96     {
  97       regs = *(sigregs_ **)(context->cfa + 8);
  98       signo = (int *)(regs + 1);
  99     }
 100
 101   new_cfa = regs->gprs[15] + 16*sizeof(long) + 32;
 102   fs->regs.cfa_how = CFA_REG_OFFSET;
 103   fs->regs.cfa_reg = 15;
 104   fs->regs.cfa_offset =
 105     new_cfa - (long) context->cfa + 16*sizeof(long) + 32;
 106
 107   for (i = 0; i < 16; i++)
 108     {
 109       fs->regs.reg[i].how = REG_SAVED_OFFSET;
 110       fs->regs.reg[i].loc.offset =
 111         (long)&regs->gprs[i] - new_cfa;
 112     }
 113   for (i = 0; i < 16; i++)
 114     {
 115       fs->regs.reg[16+i].how = REG_SAVED_OFFSET;
 116       fs->regs.reg[16+i].loc.offset =
 117         (long)&regs->fprs[dwarf_to_fpr_map[i]] - new_cfa;
 118     }
 119
 120   /* Load return addr from PSW into dummy register 32.  */
 121
 122   fs->regs.reg[32].how = REG_SAVED_OFFSET;
 123   fs->regs.reg[32].loc.offset = (long)&regs->psw_addr - new_cfa;
 124   fs->retaddr_column = 32;
 125   /* SIGILL, SIGFPE and SIGTRAP are delivered with psw_addr
 126      after the faulting instruction rather than before it.
 127      Don't set FS->signal_frame in that case.  */
 128   if (!signo || (*signo != 4 && *signo != 5 && *signo != 8))
 129     fs->signal_frame = 1;
 130
 131   return _URC_NO_REASON;
 132 }