gdb/vaxobsd-tdep.c

   1 /* Target-dependent code for OpenBSD/vax.
   2
   3    Copyright (C) 2005-2016 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 /* Signal trampolines.  */
  31
  32 /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
  33    in virtual memory.  The randomness makes it somewhat tricky to
  34    detect it, but fortunately we can rely on the fact that the start
  35    of the sigtramp routine is page-aligned.  We recognize the
  36    trampoline by looking for the code that invokes the sigreturn
  37    system call.  The offset where we can find that code varies from
  38    release to release.
  39
  40    By the way, the mapping mentioned above is read-only, so you cannot
  41    place a breakpoint in the signal trampoline.  */
  42
  43 /* Default page size.  */
  44 static const int vaxobsd_page_size = 4096;
  45
  46 /* Offset for sigreturn(2).  */
  47 static const int vaxobsd_sigreturn_offset = 0x11;
  48
  49 /* Instruction sequence for sigreturn(2).  VAX doesn't have
  50    fixed-length instructions so we include the ensuing exit(2) to
  51    reduce the chance of spurious matches.  */
  52 static const gdb_byte vaxobsd_sigreturn[] = {
  53   0xbc, 0x8f, 0x67, 0x00,       /* chmk $SYS_sigreturn */
  54   0xbc, 0x01                    /* chmk $SYS_exit */
  55 };
  56
  57 static int
  58 vaxobsd_sigtramp_sniffer (const struct frame_unwind *self,
  59                           struct frame_info *this_frame,
  60                           void **this_cache)
  61 {
  62   CORE_ADDR pc = get_frame_pc (this_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   const char *name;
  67
  68   find_pc_partial_function (pc, &name, NULL, NULL);
  69   if (name)
  70     return 0;
  71
  72   buf = (gdb_byte *) alloca (sizeof vaxobsd_sigreturn);
  73   if (!safe_frame_unwind_memory (this_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
  83 static struct trad_frame_cache *
  84 vaxobsd_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
  85 {
  86   struct trad_frame_cache *cache;
  87   CORE_ADDR addr, base, func;
  88
  89   if (*this_cache)
  90     return (struct trad_frame_cache *) *this_cache;
  91
  92   cache = trad_frame_cache_zalloc (this_frame);
  93   *this_cache = cache;
  94
  95   func = get_frame_pc (this_frame);
  96   func &= ~(vaxobsd_page_size - 1);
  97
  98   base = get_frame_register_unsigned (this_frame, VAX_SP_REGNUM);
  99   addr = get_frame_memory_unsigned (this_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
 113 static void
 114 vaxobsd_sigtramp_frame_this_id (struct frame_info *this_frame,
 115                                 void **this_cache, struct frame_id *this_id)
 116 {
 117   struct trad_frame_cache *cache =
 118     vaxobsd_sigtramp_frame_cache (this_frame, this_cache);
 119
 120   trad_frame_get_id (cache, this_id);
 121 }
 122
 123 static struct value *
 124 vaxobsd_sigtramp_frame_prev_register (struct frame_info *this_frame,
 125                                       void **this_cache, int regnum)
 126 {
 127   struct trad_frame_cache *cache =
 128     vaxobsd_sigtramp_frame_cache (this_frame, this_cache);
 129
 130   return trad_frame_get_register (cache, this_frame, regnum);
 131 }
 132
 133 static const struct frame_unwind vaxobsd_sigtramp_frame_unwind = {
 134   SIGTRAMP_FRAME,
 135   default_frame_unwind_stop_reason,
 136   vaxobsd_sigtramp_frame_this_id,
 137   vaxobsd_sigtramp_frame_prev_register,
 138   NULL,
 139   vaxobsd_sigtramp_sniffer
 140 };
 141 \f
 142
 143 /* OpenBSD a.out.  */
 144
 145 static void
 146 vaxobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 147 {
 148   frame_unwind_append_unwinder (gdbarch, &vaxobsd_sigtramp_frame_unwind);
 149 }
 150
 151 /* FIXME: kettenis/20050821: Since OpenBSD/vax binaries are
 152    indistingushable from NetBSD/vax a.out binaries, building a GDB
 153    that should support both these targets will probably not work as
 154    expected.  */
 155 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 156
 157 static enum gdb_osabi
 158 vaxobsd_aout_osabi_sniffer (bfd *abfd)
 159 {
 160   if (strcmp (bfd_get_target (abfd), "a.out-vax-netbsd") == 0)
 161     return GDB_OSABI_OPENBSD_AOUT;
 162
 163   return GDB_OSABI_UNKNOWN;
 164 }
 165 \f
 166
 167 /* Provide a prototype to silence -Wmissing-prototypes.  */
 168 void _initialize_vaxobsd_tdep (void);
 169
 170 void
 171 _initialize_vaxobsd_tdep (void)
 172 {
 173   gdbarch_register_osabi_sniffer (bfd_arch_vax, bfd_target_aout_flavour,
 174                                   vaxobsd_aout_osabi_sniffer);
 175
 176   gdbarch_register_osabi (bfd_arch_vax, 0, GDB_OSABI_OPENBSD_AOUT,
 177                           vaxobsd_init_abi);
 178 }