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1 /* DWARF2 EH unwinding support for MIPS Linux.
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2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
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3
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4 This file is part of GCC.
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5
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6 GCC is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3, or (at your option)
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9 any later version.
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10
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11 GCC is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 #ifndef inhibit_libc
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26 /* Do code reading to identify a signal frame, and set the frame
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27 state data appropriately. See unwind-dw2.c for the structs. */
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28
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29 #include <signal.h>
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30 #include <asm/unistd.h>
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31
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32 /* The third parameter to the signal handler points to something with
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33 * this structure defined in asm/ucontext.h, but the name clashes with
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34 * struct ucontext from sys/ucontext.h so this private copy is used. */
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35 typedef struct _sig_ucontext {
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36 unsigned long uc_flags;
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37 struct _sig_ucontext *uc_link;
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38 stack_t uc_stack;
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39 struct sigcontext uc_mcontext;
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40 sigset_t uc_sigmask;
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41 } _sig_ucontext_t;
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42
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43 #define MD_FALLBACK_FRAME_STATE_FOR mips_fallback_frame_state
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44
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45 static _Unwind_Reason_Code
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46 mips_fallback_frame_state (struct _Unwind_Context *context,
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47 _Unwind_FrameState *fs)
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48 {
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49 u_int32_t *pc = (u_int32_t *) context->ra;
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50 struct sigcontext *sc;
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51 _Unwind_Ptr new_cfa, reg_offset;
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52 int i;
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53
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54 /* 24021061 li v0, 0x1061 (rt_sigreturn)*/
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55 /* 0000000c syscall */
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56 /* or */
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57 /* 24021017 li v0, 0x1017 (sigreturn) */
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58 /* 0000000c syscall */
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59 if (pc[1] != 0x0000000c)
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60 return _URC_END_OF_STACK;
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61 #if _MIPS_SIM == _ABIO32
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62 if (pc[0] == (0x24020000 | __NR_sigreturn))
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63 {
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64 struct sigframe {
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65 u_int32_t ass[4]; /* Argument save space for o32. */
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66 u_int32_t trampoline[2];
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67 struct sigcontext sigctx;
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68 } *rt_ = context->cfa;
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69 sc = &rt_->sigctx;
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70 }
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71 else
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72 #endif
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73 if (pc[0] == (0x24020000 | __NR_rt_sigreturn))
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74 {
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75 struct rt_sigframe {
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76 u_int32_t ass[4]; /* Argument save space for o32. */
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77 u_int32_t trampoline[2];
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78 struct siginfo info;
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79 _sig_ucontext_t uc;
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80 } *rt_ = context->cfa;
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81 sc = &rt_->uc.uc_mcontext;
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82 }
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83 else
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84 return _URC_END_OF_STACK;
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85
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86 new_cfa = (_Unwind_Ptr) sc;
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87 fs->regs.cfa_how = CFA_REG_OFFSET;
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88 fs->regs.cfa_reg = STACK_POINTER_REGNUM;
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89 fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
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90
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91 /* On o32 Linux, the register save slots in the sigcontext are
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92 eight bytes. We need the lower half of each register slot,
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93 so slide our view of the structure back four bytes. */
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94 #if _MIPS_SIM == _ABIO32 && defined __MIPSEB__
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95 reg_offset = 4;
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96 #else
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97 reg_offset = 0;
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98 #endif
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99
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100 for (i = 0; i < 32; i++) {
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101 fs->regs.reg[i].how = REG_SAVED_OFFSET;
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102 fs->regs.reg[i].loc.offset
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103 = (_Unwind_Ptr)&(sc->sc_regs[i]) + reg_offset - new_cfa;
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104 }
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105 /* "PC & -2" points to the faulting instruction, but the unwind code
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106 searches for "(ADDR & -2) - 1". (See MASK_RETURN_ADDR for the source
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107 of the -2 mask.) Adding 2 here ensures that "(ADDR & -2) - 1" is the
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108 address of the second byte of the faulting instruction.
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109
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110 Note that setting fs->signal_frame would not work. As the comment
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111 above MASK_RETURN_ADDR explains, MIPS unwinders must earch for an
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112 odd-valued address. */
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113 fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].how = REG_SAVED_VAL_OFFSET;
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114 fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].loc.offset
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115 = (_Unwind_Ptr)(sc->sc_pc) + 2 - new_cfa;
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116 fs->retaddr_column = DWARF_ALT_FRAME_RETURN_COLUMN;
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117
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118 return _URC_NO_REASON;
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119 }
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120 #endif
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