gdb/vaxobsd-tdep.c

   1 /* Target-dependent code for OpenBSD/vax.
   2
   3    Copyright (C) 2005, 2007, 2008, 2009, 2010, 2011
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "arch-utils.h"
  23 #include "frame.h"
  24 #include "frame-unwind.h"
  25 #include "osabi.h"
  26 #include "symtab.h"
  27 #include "trad-frame.h"
  28
  29 #include "vax-tdep.h"
  30
  31 #include "gdb_string.h"
  32
  33 /* Signal trampolines.  */
  34
  35 /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
  36    in virtual memory.  The randomness makes it somewhat tricky to
  37    detect it, but fortunately we can rely on the fact that the start
  38    of the sigtramp routine is page-aligned.  We recognize the
  39    trampoline by looking for the code that invokes the sigreturn
  40    system call.  The offset where we can find that code varies from
  41    release to release.
  42
  43    By the way, the mapping mentioned above is read-only, so you cannot
  44    place a breakpoint in the signal trampoline.  */
  45
  46 /* Default page size.  */
  47 static const int vaxobsd_page_size = 4096;
  48
  49 /* Offset for sigreturn(2).  */
  50 static const int vaxobsd_sigreturn_offset = 0x11;
  51
  52 /* Instruction sequence for sigreturn(2).  VAX doesn't have
  53    fixed-length instructions so we include the ensuing exit(2) to
  54    reduce the chance of spurious matches.  */
  55 static const gdb_byte vaxobsd_sigreturn[] = {
  56   0xbc, 0x8f, 0x67, 0x00,       /* chmk $SYS_sigreturn */
  57   0xbc, 0x01                    /* chmk $SYS_exit */
  58 };
  59
  60 static int
  61 vaxobsd_sigtramp_sniffer (const struct frame_unwind *self,
  62                           struct frame_info *this_frame,
  63                           void **this_cache)
  64 {
  65   CORE_ADDR pc = get_frame_pc (this_frame);
  66   CORE_ADDR start_pc = (pc & ~(vaxobsd_page_size - 1));
  67   CORE_ADDR sigreturn_addr = start_pc + vaxobsd_sigreturn_offset;
  68   gdb_byte *buf;
  69   char *name;
  70
  71   find_pc_partial_function (pc, &name, NULL, NULL);
  72   if (name)
  73     return 0;
  74
  75   buf = alloca(sizeof vaxobsd_sigreturn);
  76   if (!safe_frame_unwind_memory (this_frame, sigreturn_addr,
  77                                  buf, sizeof vaxobsd_sigreturn))
  78     return 0;
  79
  80   if (memcmp(buf, vaxobsd_sigreturn, sizeof vaxobsd_sigreturn) == 0)
  81     return 1;
  82
  83   return 0;
  84 }
  85
  86 static struct trad_frame_cache *
  87 vaxobsd_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
  88 {
  89   struct trad_frame_cache *cache;
  90   CORE_ADDR addr, base, func;
  91
  92   if (*this_cache)
  93     return *this_cache;
  94
  95   cache = trad_frame_cache_zalloc (this_frame);
  96   *this_cache = cache;
  97
  98   func = get_frame_pc (this_frame);
  99   func &= ~(vaxobsd_page_size - 1);
 100
 101   base = get_frame_register_unsigned (this_frame, VAX_SP_REGNUM);
 102   addr = get_frame_memory_unsigned (this_frame, base - 4, 4);
 103
 104   trad_frame_set_reg_addr (cache, VAX_SP_REGNUM, addr + 8);
 105   trad_frame_set_reg_addr (cache, VAX_FP_REGNUM, addr + 12);
 106   trad_frame_set_reg_addr (cache, VAX_AP_REGNUM, addr + 16);
 107   trad_frame_set_reg_addr (cache, VAX_PC_REGNUM, addr + 20);
 108   trad_frame_set_reg_addr (cache, VAX_PS_REGNUM, addr + 24);
 109
 110   /* Construct the frame ID using the function start.  */
 111   trad_frame_set_id (cache, frame_id_build (base, func));
 112
 113   return cache;
 114 }
 115
 116 static void
 117 vaxobsd_sigtramp_frame_this_id (struct frame_info *this_frame,
 118                                 void **this_cache, struct frame_id *this_id)
 119 {
 120   struct trad_frame_cache *cache =
 121     vaxobsd_sigtramp_frame_cache (this_frame, this_cache);
 122
 123   trad_frame_get_id (cache, this_id);
 124 }
 125
 126 static struct value *
 127 vaxobsd_sigtramp_frame_prev_register (struct frame_info *this_frame,
 128                                       void **this_cache, int regnum)
 129 {
 130   struct trad_frame_cache *cache =
 131     vaxobsd_sigtramp_frame_cache (this_frame, this_cache);
 132
 133   return trad_frame_get_register (cache, this_frame, regnum);
 134 }
 135
 136 static const struct frame_unwind vaxobsd_sigtramp_frame_unwind = {
 137   SIGTRAMP_FRAME,
 138   default_frame_unwind_stop_reason,
 139   vaxobsd_sigtramp_frame_this_id,
 140   vaxobsd_sigtramp_frame_prev_register,
 141   NULL,
 142   vaxobsd_sigtramp_sniffer
 143 };
 144 \f
 145
 146 /* OpenBSD a.out.  */
 147
 148 static void
 149 vaxobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 150 {
 151   frame_unwind_append_unwinder (gdbarch, &vaxobsd_sigtramp_frame_unwind);
 152 }
 153
 154 /* FIXME: kettenis/20050821: Since OpenBSD/vax binaries are
 155    indistingushable from NetBSD/vax a.out binaries, building a GDB
 156    that should support both these targets will probably not work as
 157    expected.  */
 158 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 159
 160 static enum gdb_osabi
 161 vaxobsd_aout_osabi_sniffer (bfd *abfd)
 162 {
 163   if (strcmp (bfd_get_target (abfd), "a.out-vax-netbsd") == 0)
 164     return GDB_OSABI_OPENBSD_AOUT;
 165
 166   return GDB_OSABI_UNKNOWN;
 167 }
 168 \f
 169
 170 /* Provide a prototype to silence -Wmissing-prototypes.  */
 171 void _initialize_vaxobsd_tdep (void);
 172
 173 void
 174 _initialize_vaxobsd_tdep (void)
 175 {
 176   gdbarch_register_osabi_sniffer (bfd_arch_vax, bfd_target_aout_flavour,
 177                                   vaxobsd_aout_osabi_sniffer);
 178
 179   gdbarch_register_osabi (bfd_arch_vax, 0, GDB_OSABI_OPENBSD_AOUT,
 180                           vaxobsd_init_abi);
 181 }