gdb/vaxobsd-tdep.c

   1 /* Target-dependent code for OpenBSD/vax.
   2
   3    Copyright (C) 2005, 2007, 2008 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.  */
  46 static const int vaxobsd_page_size = 4096;
  47
  48 /* Offset for sigreturn(2).  */
  49 static 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.  */
  54 static const gdb_byte vaxobsd_sigreturn[] = {
  55   0xbc, 0x8f, 0x67, 0x00,       /* chmk $SYS_sigreturn */
  56   0xbc, 0x01                    /* chmk $SYS_exit */
  57 };
  58
  59 static int
  60 vaxobsd_sigtramp_sniffer (const struct frame_unwind *self,
  61                           struct frame_info *this_frame,
  62                           void **this_cache)
  63 {
  64   CORE_ADDR pc = get_frame_pc (this_frame);
  65   CORE_ADDR start_pc = (pc & ~(vaxobsd_page_size - 1));
  66   CORE_ADDR sigreturn_addr = start_pc + vaxobsd_sigreturn_offset;
  67   gdb_byte *buf;
  68   char *name;
  69
  70   find_pc_partial_function (pc, &name, NULL, NULL);
  71   if (name)
  72     return 0;
  73
  74   buf = alloca(sizeof vaxobsd_sigreturn);
  75   if (!safe_frame_unwind_memory (this_frame, sigreturn_addr,
  76                                  buf, sizeof vaxobsd_sigreturn))
  77     return 0;
  78
  79   if (memcmp(buf, vaxobsd_sigreturn, sizeof vaxobsd_sigreturn) == 0)
  80     return 1;
  81
  82   return 0;
  83 }
  84
  85 static struct trad_frame_cache *
  86 vaxobsd_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
  87 {
  88   struct trad_frame_cache *cache;
  89   CORE_ADDR addr, base, func;
  90
  91   if (*this_cache)
  92     return *this_cache;
  93
  94   cache = trad_frame_cache_zalloc (this_frame);
  95   *this_cache = cache;
  96
  97   func = get_frame_pc (this_frame);
  98   func &= ~(vaxobsd_page_size - 1);
  99
 100   base = get_frame_register_unsigned (this_frame, VAX_SP_REGNUM);
 101   addr = get_frame_memory_unsigned (this_frame, base - 4, 4);
 102
 103   trad_frame_set_reg_addr (cache, VAX_SP_REGNUM, addr + 8);
 104   trad_frame_set_reg_addr (cache, VAX_FP_REGNUM, addr + 12);
 105   trad_frame_set_reg_addr (cache, VAX_AP_REGNUM, addr + 16);
 106   trad_frame_set_reg_addr (cache, VAX_PC_REGNUM, addr + 20);
 107   trad_frame_set_reg_addr (cache, VAX_PS_REGNUM, addr + 24);
 108
 109   /* Construct the frame ID using the function start.  */
 110   trad_frame_set_id (cache, frame_id_build (base, func));
 111
 112   return cache;
 113 }
 114
 115 static void
 116 vaxobsd_sigtramp_frame_this_id (struct frame_info *this_frame,
 117                                 void **this_cache, struct frame_id *this_id)
 118 {
 119   struct trad_frame_cache *cache =
 120     vaxobsd_sigtramp_frame_cache (this_frame, this_cache);
 121
 122   trad_frame_get_id (cache, this_id);
 123 }
 124
 125 static struct value *
 126 vaxobsd_sigtramp_frame_prev_register (struct frame_info *this_frame,
 127                                       void **this_cache, int regnum)
 128 {
 129   struct trad_frame_cache *cache =
 130     vaxobsd_sigtramp_frame_cache (this_frame, this_cache);
 131
 132   return trad_frame_get_register (cache, this_frame, regnum);
 133 }
 134
 135 static const struct frame_unwind vaxobsd_sigtramp_frame_unwind = {
 136   SIGTRAMP_FRAME,
 137   vaxobsd_sigtramp_frame_this_id,
 138   vaxobsd_sigtramp_frame_prev_register,
 139   NULL,
 140   vaxobsd_sigtramp_sniffer
 141 };
 142 \f
 143
 144 /* OpenBSD a.out.  */
 145
 146 static void
 147 vaxobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 148 {
 149   frame_unwind_append_unwinder (gdbarch, &vaxobsd_sigtramp_frame_unwind);
 150 }
 151
 152 /* FIXME: kettenis/20050821: Since OpenBSD/vax binaries are
 153    indistingushable from NetBSD/vax a.out binaries, building a GDB
 154    that should support both these targets will probably not work as
 155    expected.  */
 156 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 157
 158 static enum gdb_osabi
 159 vaxobsd_aout_osabi_sniffer (bfd *abfd)
 160 {
 161   if (strcmp (bfd_get_target (abfd), "a.out-vax-netbsd") == 0)
 162     return GDB_OSABI_OPENBSD_AOUT;
 163
 164   return GDB_OSABI_UNKNOWN;
 165 }
 166 \f
 167
 168 /* Provide a prototype to silence -Wmissing-prototypes.  */
 169 void _initialize_vaxobsd_tdep (void);
 170
 171 void
 172 _initialize_vaxobsd_tdep (void)
 173 {
 174   gdbarch_register_osabi_sniffer (bfd_arch_vax, bfd_target_aout_flavour,
 175                                   vaxobsd_aout_osabi_sniffer);
 176
 177   gdbarch_register_osabi (bfd_arch_vax, 0, GDB_OSABI_OPENBSD_AOUT,
 178                           vaxobsd_init_abi);
 179 }