1/* DWARF2 EH unwinding support for MIPS Linux.
2   Copyright (C) 2004, 2005 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 2, or (at your option)
9any later version.
10
11In addition to the permissions in the GNU General Public License, the
12Free Software Foundation gives you unlimited permission to link the
13compiled version of this file with other programs, and to distribute
14those programs without any restriction coming from the use of this
15file.  (The General Public License restrictions do apply in other
16respects; for example, they cover modification of the file, and
17distribution when not linked into another program.)
18
19GCC is distributed in the hope that it will be useful,
20but WITHOUT ANY WARRANTY; without even the implied warranty of
21MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
22GNU General Public License for more details.
23
24You should have received a copy of the GNU General Public License
25along with GCC; see the file COPYING.  If not, write to
26the Free Software Foundation, 51 Franklin Street, Fifth Floor,
27Boston, MA 02110-1301, USA.  */
28
29#ifndef inhibit_libc
30/* Do code reading to identify a signal frame, and set the frame
31   state data appropriately.  See unwind-dw2.c for the structs.  */
32
33#include <signal.h>
34#include <asm/unistd.h>
35
36/* The third parameter to the signal handler points to something with
37 * this structure defined in asm/ucontext.h, but the name clashes with
38 * struct ucontext from sys/ucontext.h so this private copy is used.  */
39typedef struct _sig_ucontext {
40    unsigned long         uc_flags;
41    struct _sig_ucontext  *uc_link;
42    stack_t               uc_stack;
43    struct sigcontext uc_mcontext;
44    sigset_t      uc_sigmask;
45} _sig_ucontext_t;
46
47#define MD_FALLBACK_FRAME_STATE_FOR mips_fallback_frame_state
48
49static _Unwind_Reason_Code
50mips_fallback_frame_state (struct _Unwind_Context *context,
51			   _Unwind_FrameState *fs)
52{
53  u_int32_t *pc = (u_int32_t *) context->ra;
54  struct sigcontext *sc;
55  _Unwind_Ptr new_cfa;
56  int i;
57
58  /* 24021061 li v0, 0x1061 (rt_sigreturn)*/
59  /* 0000000c syscall    */
60  /*    or */
61  /* 24021017 li v0, 0x1017 (sigreturn) */
62  /* 0000000c syscall  */
63  if (pc[1] != 0x0000000c)
64    return _URC_END_OF_STACK;
65#if _MIPS_SIM == _ABIO32
66  if (pc[0] == (0x24020000 | __NR_sigreturn))
67    {
68      struct sigframe {
69	u_int32_t trampoline[2];
70	struct sigcontext sigctx;
71      } *rt_ = context->ra;
72      sc = &rt_->sigctx;
73    }
74  else
75#endif
76  if (pc[0] == (0x24020000 | __NR_rt_sigreturn))
77    {
78      struct rt_sigframe {
79	u_int32_t trampoline[2];
80	struct siginfo info;
81	_sig_ucontext_t uc;
82      } *rt_ = context->ra;
83      sc = &rt_->uc.uc_mcontext;
84    }
85  else
86    return _URC_END_OF_STACK;
87
88  new_cfa = (_Unwind_Ptr)sc;
89  fs->cfa_how = CFA_REG_OFFSET;
90  fs->cfa_reg = STACK_POINTER_REGNUM;
91  fs->cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
92
93#if _MIPS_SIM == _ABIO32 && defined __MIPSEB__
94  /* On o32 Linux, the register save slots in the sigcontext are
95     eight bytes.  We need the lower half of each register slot,
96     so slide our view of the structure back four bytes.  */
97  new_cfa -= 4;
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]) - new_cfa;
104  }
105  fs->regs.reg[SIGNAL_UNWIND_RETURN_COLUMN].how = REG_SAVED_OFFSET;
106  fs->regs.reg[SIGNAL_UNWIND_RETURN_COLUMN].loc.offset
107    = (_Unwind_Ptr)&(sc->sc_pc) - new_cfa;
108  fs->retaddr_column = SIGNAL_UNWIND_RETURN_COLUMN;
109
110  return _URC_NO_REASON;
111}
112#endif
113