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1 /* DWARF2 EH unwinding support for Xtensa.
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2 Copyright (C) 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 /* Do code reading to identify a signal frame, and set the frame
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26 state data appropriately. See unwind-dw2-xtensa.c for the structs.
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27 Don't use this at all if inhibit_libc is used. */
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28
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29 #ifndef inhibit_libc
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30
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31 #include <signal.h>
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32 #include <sys/ucontext.h>
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33
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34 /* Encoded bytes for Xtensa instructions:
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35 movi a2, __NR_rt_sigreturn
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36 syscall
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37 entry (first byte only)
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38 Some of the bytes are endian-dependent. */
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39
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40 #define MOVI_BYTE0 0x22
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41 #define MOVI_BYTE2 225 /* __NR_rt_sigreturn */
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42 #define SYSC_BYTE0 0
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43 #define SYSC_BYTE2 0
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44
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45 #ifdef __XTENSA_EB__
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46 #define MOVI_BYTE1 0x0a
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47 #define SYSC_BYTE1 0x05
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48 #define ENTRY_BYTE 0x6c
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49 #else
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50 #define MOVI_BYTE1 0xa0
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51 #define SYSC_BYTE1 0x50
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52 #define ENTRY_BYTE 0x36
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53 #endif
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54
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55 #define MD_FALLBACK_FRAME_STATE_FOR xtensa_fallback_frame_state
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56
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57 static _Unwind_Reason_Code
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58 xtensa_fallback_frame_state (struct _Unwind_Context *context,
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59 _Unwind_FrameState *fs)
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60 {
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61 unsigned char *pc = context->ra;
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62 struct sigcontext *sc;
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63
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64 struct rt_sigframe {
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65 struct siginfo info;
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66 struct ucontext uc;
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67 } *rt_;
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68
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69 /* movi a2, __NR_rt_sigreturn; syscall */
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70 if (pc[0] != MOVI_BYTE0
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71 || pc[1] != MOVI_BYTE1
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72 || pc[2] != MOVI_BYTE2
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73 || pc[3] != SYSC_BYTE0
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74 || pc[4] != SYSC_BYTE1
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75 || pc[5] != SYSC_BYTE2)
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76 return _URC_END_OF_STACK;
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77
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78 rt_ = context->sp;
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79 sc = &rt_->uc.uc_mcontext;
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80 fs->signal_regs = (_Unwind_Word *) sc->sc_a;
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81
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82 /* If the signal arrived just before an ENTRY instruction, find the return
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83 address and pretend the signal arrived before executing the CALL. */
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84 if (*(unsigned char *) sc->sc_pc == ENTRY_BYTE)
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85 {
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86 unsigned callinc = (sc->sc_ps >> 16) & 3;
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87 fs->signal_ra = ((sc->sc_a[callinc << 2] & XTENSA_RA_FIELD_MASK)
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88 | context->ra_high_bits) - 3;
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89 }
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90 else
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91 fs->signal_ra = sc->sc_pc;
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92
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93 fs->signal_frame = 1;
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94 return _URC_NO_REASON;
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95 }
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96
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97 #endif /* ifdef inhibit_libc */
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