linux-unwind.h revision 1.1 
1/* DWARF2 EH unwinding support for MIPS Linux.
2   Copyright (C) 2004-2013 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#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.  */
35typedef 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
45static _Unwind_Reason_Code
46mips_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	siginfo_t 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
121