1/* Target-dependent code for OpenBSD/alpha.
2
3   Copyright (C) 2006, 2007 Free Software Foundation, Inc.
4
5   This file is part of GDB.
6
7   This program is free software; you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 3 of the License, or
10   (at your option) any later version.
11
12   This program is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   GNU General Public License for more details.
16
17   You should have received a copy of the GNU General Public License
18   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
19
20#include "defs.h"
21#include "frame.h"
22#include "gdbcore.h"
23#include "osabi.h"
24
25#include "obsd-tdep.h"
26#include "alpha-tdep.h"
27#include "alphabsd-tdep.h"
28#include "solib-svr4.h"
29
30/* Signal trampolines.  */
31
32/* The OpenBSD kernel maps the signal trampoline at some random
33   location in user space, which means that the traditional BSD way of
34   detecting it won't work.
35
36   The signal trampoline will be mapped at an address that is page
37   aligned.  We recognize the signal trampoline by looking for the
38   sigreturn system call.  */
39
40static const int alphaobsd_page_size = 8192;
41
42static LONGEST
43alphaobsd_sigtramp_offset (CORE_ADDR pc)
44{
45  return (pc & (alphaobsd_page_size - 1));
46}
47
48static int
49alphaobsd_pc_in_sigtramp (CORE_ADDR pc, char *name)
50{
51  CORE_ADDR start_pc = (pc & ~(alphaobsd_page_size - 1));
52  unsigned insn;
53
54  if (name)
55    return 0;
56
57  /* Check for "".  */
58  insn = alpha_read_insn (start_pc + 5 * ALPHA_INSN_SIZE);
59  if (insn != 0x201f0067)
60    return 0;
61
62  /* Check for "".  */
63  insn = alpha_read_insn (start_pc + 6 * ALPHA_INSN_SIZE);
64  if (insn != 0x00000083)
65    return 0;
66
67  return 1;
68}
69
70static CORE_ADDR
71alphaobsd_sigcontext_addr (struct frame_info *next_frame)
72{
73  CORE_ADDR pc = frame_pc_unwind (next_frame);
74
75  if (alphaobsd_sigtramp_offset (pc) < 3 * ALPHA_INSN_SIZE)
76    {
77      /* On entry, a pointer the `struct sigcontext' is passed in %a2.  */
78      return frame_unwind_register_unsigned (next_frame, ALPHA_A0_REGNUM + 2);
79    }
80  else if (alphaobsd_sigtramp_offset (pc) < 4 * ALPHA_INSN_SIZE)
81    {
82      /* It is stored on the stack Before calling the signal handler.  */
83      CORE_ADDR sp;
84      sp = frame_unwind_register_unsigned (next_frame, ALPHA_SP_REGNUM);
85      return get_frame_memory_unsigned (next_frame, sp, 8);
86    }
87  else
88    {
89      /* It is reloaded into %a0 for the sigreturn(2) call.  */
90      return frame_unwind_register_unsigned (next_frame, ALPHA_A0_REGNUM);
91    }
92}
93
94
95static void
96alphaobsd_init_abi(struct gdbarch_info info, struct gdbarch *gdbarch)
97{
98  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
99
100  /* Hook into the DWARF CFI frame unwinder.  */
101  alpha_dwarf2_init_abi (info, gdbarch);
102
103  /* Hook into the MDEBUG frame unwinder.  */
104  alpha_mdebug_init_abi (info, gdbarch);
105
106  /* OpenBSD/alpha 3.0 and earlier does not provide single step
107     support via ptrace(2); use software single-stepping for now.  */
108  set_gdbarch_software_single_step (gdbarch, alpha_software_single_step);
109
110  /* OpenBSD/alpha has SVR4-style shared libraries.  */
111  set_solib_svr4_fetch_link_map_offsets
112    (gdbarch, svr4_lp64_fetch_link_map_offsets);
113  set_gdbarch_skip_solib_resolver (gdbarch, obsd_skip_solib_resolver);
114
115  tdep->dynamic_sigtramp_offset = alphaobsd_sigtramp_offset;
116  tdep->pc_in_sigtramp = alphaobsd_pc_in_sigtramp;
117  tdep->sigcontext_addr = alphaobsd_sigcontext_addr;
118
119  tdep->jb_pc = 2;
120  tdep->jb_elt_size = 8;
121
122  set_gdbarch_regset_from_core_section
123    (gdbarch, alphanbsd_regset_from_core_section);
124}
125
126
127/* Provide a prototype to silence -Wmissing-prototypes.  */
128void _initialize_alphaobsd_tdep (void);
129
130void
131_initialize_alphaobsd_tdep (void)
132{
133  gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_OPENBSD_ELF,
134                          alphaobsd_init_abi);
135}
136