1/* Target-dependent code for OpenBSD/vax.
2
3   Copyright (C) 2005, 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 "arch-utils.h"
22#include "frame.h"
23#include "frame-unwind.h"
24#include "osabi.h"
25#include "symtab.h"
26#include "trad-frame.h"
27
28#include "vax-tdep.h"
29
30#include "gdb_string.h"
31
32/* Signal trampolines.  */
33
34/* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
35   in virtual memory.  The randomness makes it somewhat tricky to
36   detect it, but fortunately we can rely on the fact that the start
37   of the sigtramp routine is page-aligned.  We recognize the
38   trampoline by looking for the code that invokes the sigreturn
39   system call.  The offset where we can find that code varies from
40   release to release.
41
42   By the way, the mapping mentioned above is read-only, so you cannot
43   place a breakpoint in the signal trampoline.  */
44
45/* Default page size.  */
46static const int vaxobsd_page_size = 4096;
47
48/* Offset for sigreturn(2).  */
49static const int vaxobsd_sigreturn_offset = 0x11;
50
51/* Instruction sequence for sigreturn(2).  VAX doesn't have
52   fixed-length instructions so we include the ensuing exit(2) to
53   reduce the chance of spurious matches.  */
54static const gdb_byte vaxobsd_sigreturn[] = {
55  0xbc, 0x8f, 0x67, 0x00,	/* chmk $SYS_sigreturn */
56  0xbc, 0x01			/* chmk $SYS_exit */
57};
58
59static int
60vaxobsd_sigtramp_p (struct frame_info *next_frame)
61{
62  CORE_ADDR pc = frame_pc_unwind (next_frame);
63  CORE_ADDR start_pc = (pc & ~(vaxobsd_page_size - 1));
64  CORE_ADDR sigreturn_addr = start_pc + vaxobsd_sigreturn_offset;
65  gdb_byte *buf;
66  char *name;
67
68  find_pc_partial_function (pc, &name, NULL, NULL);
69  if (name)
70    return 0;
71
72  buf = alloca(sizeof vaxobsd_sigreturn);
73  if (!safe_frame_unwind_memory (next_frame, sigreturn_addr,
74				 buf, sizeof vaxobsd_sigreturn))
75    return 0;
76
77  if (memcmp(buf, vaxobsd_sigreturn, sizeof vaxobsd_sigreturn) == 0)
78    return 1;
79
80  return 0;
81}
82
83static struct trad_frame_cache *
84vaxobsd_sigtramp_frame_cache (struct frame_info *next_frame, void **this_cache)
85{
86  struct trad_frame_cache *cache;
87  CORE_ADDR addr, base, func;
88
89  if (*this_cache)
90    return *this_cache;
91
92  cache = trad_frame_cache_zalloc (next_frame);
93  *this_cache = cache;
94
95  func = frame_pc_unwind (next_frame);
96  func &= ~(vaxobsd_page_size - 1);
97
98  base = frame_unwind_register_unsigned (next_frame, VAX_SP_REGNUM);
99  addr = get_frame_memory_unsigned (next_frame, base - 4, 4);
100
101  trad_frame_set_reg_addr (cache, VAX_SP_REGNUM, addr + 8);
102  trad_frame_set_reg_addr (cache, VAX_FP_REGNUM, addr + 12);
103  trad_frame_set_reg_addr (cache, VAX_AP_REGNUM, addr + 16);
104  trad_frame_set_reg_addr (cache, VAX_PC_REGNUM, addr + 20);
105  trad_frame_set_reg_addr (cache, VAX_PS_REGNUM, addr + 24);
106
107  /* Construct the frame ID using the function start.  */
108  trad_frame_set_id (cache, frame_id_build (base, func));
109
110  return cache;
111}
112
113static void
114vaxobsd_sigtramp_frame_this_id (struct frame_info *next_frame,
115				void **this_cache, struct frame_id *this_id)
116{
117  struct trad_frame_cache *cache =
118    vaxobsd_sigtramp_frame_cache (next_frame, this_cache);
119
120  trad_frame_get_id (cache, this_id);
121}
122
123static void
124vaxobsd_sigtramp_frame_prev_register (struct frame_info *next_frame,
125				      void **this_cache, int regnum,
126				      int *optimizedp, enum lval_type *lvalp,
127				      CORE_ADDR *addrp, int *realnump,
128				      gdb_byte *valuep)
129{
130  struct trad_frame_cache *cache =
131    vaxobsd_sigtramp_frame_cache (next_frame, this_cache);
132
133  trad_frame_get_register (cache, next_frame, regnum,
134			   optimizedp, lvalp, addrp, realnump, valuep);
135}
136
137static const struct frame_unwind vaxobsd_sigtramp_frame_unwind = {
138  SIGTRAMP_FRAME,
139  vaxobsd_sigtramp_frame_this_id,
140  vaxobsd_sigtramp_frame_prev_register
141};
142
143static const struct frame_unwind *
144vaxobsd_sigtramp_frame_sniffer (struct frame_info *next_frame)
145{
146  if (vaxobsd_sigtramp_p (next_frame))
147    return &vaxobsd_sigtramp_frame_unwind;
148
149  return NULL;
150}
151
152
153/* OpenBSD a.out.  */
154
155static void
156vaxobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
157{
158  frame_unwind_append_sniffer (gdbarch, vaxobsd_sigtramp_frame_sniffer);
159}
160
161/* FIXME: kettenis/20050821: Since OpenBSD/vax binaries are
162   indistingushable from NetBSD/vax a.out binaries, building a GDB
163   that should support both these targets will probably not work as
164   expected.  */
165#define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
166
167static enum gdb_osabi
168vaxobsd_aout_osabi_sniffer (bfd *abfd)
169{
170  if (strcmp (bfd_get_target (abfd), "a.out-vax-netbsd") == 0)
171    return GDB_OSABI_OPENBSD_AOUT;
172
173  return GDB_OSABI_UNKNOWN;
174}
175
176
177/* Provide a prototype to silence -Wmissing-prototypes.  */
178void _initialize_vaxobsd_tdep (void);
179
180void
181_initialize_vaxobsd_tdep (void)
182{
183  gdbarch_register_osabi_sniffer (bfd_arch_vax, bfd_target_aout_flavour,
184				  vaxobsd_aout_osabi_sniffer);
185
186  gdbarch_register_osabi (bfd_arch_vax, 0, GDB_OSABI_OPENBSD_AOUT,
187			  vaxobsd_init_abi);
188}
189