gcc/config/s390/linux-unwind.h

   1 /* DWARF2 EH unwinding support for S/390 Linux.
   2    Copyright (C) 2004, 2005 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 2, or (at your option) any later
   9 version.
  10
  11 In addition to the permissions in the GNU General Public License, the
  12 Free Software Foundation gives you unlimited permission to link the
  13 compiled version of this file with other programs, and to distribute
  14 those programs without any restriction coming from the use of this
  15 file.  (The General Public License restrictions do apply in other
  16 respects; for example, they cover modification of the file, and
  17 distribution when not linked into another program.)
  18
  19 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  20 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  21 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  22 for more details.
  23
  24 You should have received a copy of the GNU General Public License
  25 along with GCC; see the file COPYING.  If not, write to the Free
  26 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  27 02111-1307, USA.  */
  28
  29 /* Do code reading to identify a signal frame, and set the frame
  30    state data appropriately.  See unwind-dw2.c for the structs.  */
  31
  32 #define MD_FALLBACK_FRAME_STATE_FOR s390_fallback_frame_state
  33
  34 static _Unwind_Reason_Code
  35 s390_fallback_frame_state (struct _Unwind_Context *context,
  36                            _Unwind_FrameState *fs)
  37 {
  38   unsigned char *pc = context->ra;
  39   long new_cfa;
  40   int i;
  41
  42   typedef struct
  43   {
  44     unsigned long psw_mask;
  45     unsigned long psw_addr;
  46     unsigned long gprs[16];
  47     unsigned int  acrs[16];
  48     unsigned int  fpc;
  49     unsigned int  __pad;
  50     double        fprs[16];
  51   } __attribute__ ((__aligned__ (8))) sigregs_;
  52
  53   sigregs_ *regs;
  54   int *signo = NULL;
  55
  56   /* svc $__NR_sigreturn or svc $__NR_rt_sigreturn  */
  57   if (pc[0] != 0x0a || (pc[1] != 119 && pc[1] != 173))
  58     return _URC_END_OF_STACK;
  59
  60   /* New-style RT frame:
  61      retcode + alignment (8 bytes)
  62      siginfo (128 bytes)
  63      ucontext (contains sigregs)  */
  64   if (context->ra == context->cfa)
  65     {
  66       struct ucontext_
  67       {
  68         unsigned long     uc_flags;
  69         struct ucontext_ *uc_link;
  70         unsigned long     uc_stack[3];
  71         sigregs_          uc_mcontext;
  72       } *uc = context->cfa + 8 + 128;
  73
  74       regs = &uc->uc_mcontext;
  75       signo = context->cfa + sizeof(long);
  76     }
  77
  78   /* Old-style RT frame and all non-RT frames:
  79      old signal mask (8 bytes)
  80      pointer to sigregs  */
  81   else
  82     {
  83       regs = *(sigregs_ **)(context->cfa + 8);
  84
  85       /* Recent kernels store the signal number immediately after
  86          the sigregs; old kernels have the return trampoline at
  87          this location.  */
  88       if ((void *)(regs + 1) != context->ra)
  89         signo = (int *)(regs + 1);
  90     }
  91
  92   new_cfa = regs->gprs[15] + 16*sizeof(long) + 32;
  93   fs->cfa_how = CFA_REG_OFFSET;
  94   fs->cfa_reg = 15;
  95   fs->cfa_offset =
  96     new_cfa - (long) context->cfa + 16*sizeof(long) + 32;
  97
  98   for (i = 0; i < 16; i++)
  99     {
 100       fs->regs.reg[i].how = REG_SAVED_OFFSET;
 101       fs->regs.reg[i].loc.offset =
 102         (long)&regs->gprs[i] - new_cfa;
 103     }
 104   for (i = 0; i < 16; i++)
 105     {
 106       fs->regs.reg[16+i].how = REG_SAVED_OFFSET;
 107       fs->regs.reg[16+i].loc.offset =
 108         (long)&regs->fprs[i] - new_cfa;
 109     }
 110
 111   /* Load return addr from PSW into dummy register 32.  */
 112
 113   fs->regs.reg[32].how = REG_SAVED_OFFSET;
 114   fs->regs.reg[32].loc.offset = (long)&regs->psw_addr - new_cfa;
 115   fs->retaddr_column = 32;
 116
 117   /* If we got a SIGSEGV or a SIGBUS, the PSW address points *to*
 118      the faulting instruction, not after it.  This causes the logic
 119      in unwind-dw2.c that decrements the RA to determine the correct
 120      CFI region to get confused.  To fix that, we *increment* the RA
 121      here in that case.  Note that we cannot modify the RA in place,
 122      and the frame state wants a *pointer*, not a value; thus we put
 123      the modified RA value into the unused register 33 slot of FS and
 124      have the register 32 save address point to that slot.
 125
 126      Unfortunately, for regular signals on old kernels, we don't know
 127      the signal number.  We default to not fiddling with the RA;
 128      that can fail in rare cases.  Upgrade your kernel.  */
 129
 130   if (signo && (*signo == 11 || *signo == 7))
 131     {
 132       fs->regs.reg[33].loc.exp =
 133         (unsigned char *)regs->psw_addr + 1;
 134       fs->regs.reg[32].loc.offset =
 135         (long)&fs->regs.reg[33].loc.exp - new_cfa;
 136     }
 137
 138   return _URC_NO_REASON;
 139 }