libgcc/config/mips/linux-unwind.h

   1 /* DWARF2 EH unwinding support for MIPS Linux.
   2    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 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 <asm/unistd.h>
  31
  32 /* The third parameter to the signal handler points to something with
  33  * this structure defined in asm/ucontext.h, but the name clashes with
  34  * struct ucontext from sys/ucontext.h so this private copy is used.  */
  35 typedef struct _sig_ucontext {
  36     unsigned long         uc_flags;
  37     struct _sig_ucontext  *uc_link;
  38     stack_t               uc_stack;
  39     struct sigcontext uc_mcontext;
  40     sigset_t      uc_sigmask;
  41 } _sig_ucontext_t;
  42
  43 #define MD_FALLBACK_FRAME_STATE_FOR mips_fallback_frame_state
  44
  45 static _Unwind_Reason_Code
  46 mips_fallback_frame_state (struct _Unwind_Context *context,
  47                            _Unwind_FrameState *fs)
  48 {
  49   u_int32_t *pc = (u_int32_t *) context->ra;
  50   struct sigcontext *sc;
  51   _Unwind_Ptr new_cfa, reg_offset;
  52   int i;
  53
  54   /* 24021061 li v0, 0x1061 (rt_sigreturn)*/
  55   /* 0000000c syscall    */
  56   /*    or */
  57   /* 24021017 li v0, 0x1017 (sigreturn) */
  58   /* 0000000c syscall  */
  59   if (pc[1] != 0x0000000c)
  60     return _URC_END_OF_STACK;
  61 #if _MIPS_SIM == _ABIO32
  62   if (pc[0] == (0x24020000 | __NR_sigreturn))
  63     {
  64       struct sigframe {
  65         u_int32_t ass[4];  /* Argument save space for o32.  */
  66         u_int32_t trampoline[2];
  67         struct sigcontext sigctx;
  68       } *rt_ = context->cfa;
  69       sc = &rt_->sigctx;
  70     }
  71   else
  72 #endif
  73   if (pc[0] == (0x24020000 | __NR_rt_sigreturn))
  74     {
  75       struct rt_sigframe {
  76         u_int32_t ass[4];  /* Argument save space for o32.  */
  77         u_int32_t trampoline[2];
  78         struct siginfo info;
  79         _sig_ucontext_t uc;
  80       } *rt_ = context->cfa;
  81       sc = &rt_->uc.uc_mcontext;
  82     }
  83   else
  84     return _URC_END_OF_STACK;
  85
  86   new_cfa = (_Unwind_Ptr) sc;
  87   fs->regs.cfa_how = CFA_REG_OFFSET;
  88   fs->regs.cfa_reg = STACK_POINTER_REGNUM;
  89   fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
  90
  91   /* On o32 Linux, the register save slots in the sigcontext are
  92      eight bytes.  We need the lower half of each register slot,
  93      so slide our view of the structure back four bytes.  */
  94 #if _MIPS_SIM == _ABIO32 && defined __MIPSEB__
  95   reg_offset = 4;
  96 #else
  97   reg_offset = 0;
  98 #endif
  99
 100   for (i = 0; i < 32; i++) {
 101     fs->regs.reg[i].how = REG_SAVED_OFFSET;
 102     fs->regs.reg[i].loc.offset
 103       = (_Unwind_Ptr)&(sc->sc_regs[i]) + reg_offset - new_cfa;
 104   }
 105   /* "PC & -2" points to the faulting instruction, but the unwind code
 106      searches for "(ADDR & -2) - 1".  (See MASK_RETURN_ADDR for the source
 107      of the -2 mask.)  Adding 2 here ensures that "(ADDR & -2) - 1" is the
 108      address of the second byte of the faulting instruction.
 109
 110      Note that setting fs->signal_frame would not work.  As the comment
 111      above MASK_RETURN_ADDR explains, MIPS unwinders must earch for an
 112      odd-valued address.  */
 113   fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].how = REG_SAVED_VAL_OFFSET;
 114   fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].loc.offset
 115     = (_Unwind_Ptr)(sc->sc_pc) + 2 - new_cfa;
 116   fs->retaddr_column = DWARF_ALT_FRAME_RETURN_COLUMN;
 117
 118   return _URC_NO_REASON;
 119 }
 120 #endif