linux-unwind.h revision 1.1.1.1 
1/* DWARF2 EH unwinding support for Xtensa.
2   Copyright (C) 2008-2013 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify
7it under the terms of the GNU General Public License as published by
8the Free Software Foundation; either version 3, or (at your option)
9any later version.
10
11GCC is distributed in the hope that it will be useful,
12but WITHOUT ANY WARRANTY; without even the implied warranty of
13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14GNU General Public License for more details.
15
16Under Section 7 of GPL version 3, you are granted additional
17permissions described in the GCC Runtime Library Exception, version
183.1, as published by the Free Software Foundation.
19
20You should have received a copy of the GNU General Public License and
21a copy of the GCC Runtime Library Exception along with this program;
22see 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-xtensa.c for the structs.
27   Don't use this at all if inhibit_libc is used.  */
28
29#ifndef inhibit_libc
30
31#include <signal.h>
32#include <sys/ucontext.h>
33
34/* Encoded bytes for Xtensa instructions:
35	movi a2, __NR_rt_sigreturn
36	syscall
37	entry (first byte only)
38   Some of the bytes are endian-dependent.  */
39
40#define MOVI_BYTE0 0x22
41#define MOVI_BYTE2 225 /* __NR_rt_sigreturn */
42#define SYSC_BYTE0 0
43#define SYSC_BYTE2 0
44
45#ifdef __XTENSA_EB__
46#define MOVI_BYTE1 0x0a
47#define SYSC_BYTE1 0x05
48#define ENTRY_BYTE 0x6c
49#else
50#define MOVI_BYTE1 0xa0
51#define SYSC_BYTE1 0x50
52#define ENTRY_BYTE 0x36
53#endif
54
55#define MD_FALLBACK_FRAME_STATE_FOR xtensa_fallback_frame_state
56
57static _Unwind_Reason_Code
58xtensa_fallback_frame_state (struct _Unwind_Context *context,
59			     _Unwind_FrameState *fs)
60{
61  unsigned char *pc = context->ra;
62  struct sigcontext *sc;
63
64  struct rt_sigframe {
65    siginfo_t info;
66    struct ucontext uc;
67  } *rt_;
68
69  /* movi a2, __NR_rt_sigreturn; syscall */
70  if (pc[0] != MOVI_BYTE0
71      || pc[1] != MOVI_BYTE1
72      || pc[2] != MOVI_BYTE2
73      || pc[3] != SYSC_BYTE0
74      || pc[4] != SYSC_BYTE1
75      || pc[5] != SYSC_BYTE2)
76    return _URC_END_OF_STACK;
77
78  rt_ = context->sp;
79  sc = &rt_->uc.uc_mcontext;
80  fs->signal_regs = (_Unwind_Word *) sc->sc_a;
81
82  /* If the signal arrived just before an ENTRY instruction, find the return
83     address and pretend the signal arrived before executing the CALL.  */
84  if (*(unsigned char *) sc->sc_pc == ENTRY_BYTE)
85   {
86     unsigned callinc = (sc->sc_ps >> 16) & 3;
87     fs->signal_ra = ((sc->sc_a[callinc << 2] & XTENSA_RA_FIELD_MASK)
88		      | context->ra_high_bits) - 3;
89   }
90  else
91    fs->signal_ra = sc->sc_pc;
92
93  fs->signal_frame = 1;
94  return _URC_NO_REASON;
95}
96
97#endif /* ifdef inhibit_libc  */
98