gdb/vaxobsd-tdep.c

   1 /* Target-dependent code for OpenBSD/vax.
   2
   3    Copyright (C) 2005 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 2 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, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20    Boston, MA 02110-1301, USA.  */
  21
  22 #include "defs.h"
  23 #include "arch-utils.h"
  24 #include "frame.h"
  25 #include "frame-unwind.h"
  26 #include "osabi.h"
  27 #include "symtab.h"
  28 #include "trad-frame.h"
  29
  30 #include "vax-tdep.h"
  31
  32 #include "gdb_string.h"
  33
  34 /* Signal trampolines.  */
  35
  36 /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
  37    in virtual memory.  The randomness makes it somewhat tricky to
  38    detect it, but fortunately we can rely on the fact that the start
  39    of the sigtramp routine is page-aligned.  We recognize the
  40    trampoline by looking for the code that invokes the sigreturn
  41    system call.  The offset where we can find that code varies from
  42    release to release.
  43
  44    By the way, the mapping mentioned above is read-only, so you cannot
  45    place a breakpoint in the signal trampoline.  */
  46
  47 /* Default page size.  */
  48 static const int vaxobsd_page_size = 4096;
  49
  50 /* Offset for sigreturn(2).  */
  51 static const int vaxobsd_sigreturn_offset = 0x11;
  52
  53 /* Instruction sequence for sigreturn(2).  VAX doesn't have
  54    fixed-length instructions so we include the ensuing exit(2) to
  55    reduce the chance of spurious matches.  */
  56 static const gdb_byte vaxobsd_sigreturn[] = {
  57   0xbc, 0x8f, 0x67, 0x00,       /* chmk $SYS_sigreturn */
  58   0xbc, 0x01                    /* chmk $SYS_exit */
  59 };
  60
  61 static int
  62 vaxobsd_sigtramp_p (struct frame_info *next_frame)
  63 {
  64   CORE_ADDR pc = frame_pc_unwind (next_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 (next_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 *next_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 (next_frame);
  95   *this_cache = cache;
  96
  97   func = frame_pc_unwind (next_frame);
  98   func &= ~(vaxobsd_page_size - 1);
  99
 100   base = frame_unwind_register_unsigned (next_frame, VAX_SP_REGNUM);
 101   addr = get_frame_memory_unsigned (next_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 *next_frame,
 117                                 void **this_cache, struct frame_id *this_id)
 118 {
 119   struct trad_frame_cache *cache =
 120     vaxobsd_sigtramp_frame_cache (next_frame, this_cache);
 121
 122   trad_frame_get_id (cache, this_id);
 123 }
 124
 125 static void
 126 vaxobsd_sigtramp_frame_prev_register (struct frame_info *next_frame,
 127                                       void **this_cache, int regnum,
 128                                       int *optimizedp, enum lval_type *lvalp,
 129                                       CORE_ADDR *addrp, int *realnump,
 130                                       gdb_byte *valuep)
 131 {
 132   struct trad_frame_cache *cache =
 133     vaxobsd_sigtramp_frame_cache (next_frame, this_cache);
 134
 135   trad_frame_get_register (cache, next_frame, regnum,
 136                            optimizedp, lvalp, addrp, realnump, valuep);
 137 }
 138
 139 static const struct frame_unwind vaxobsd_sigtramp_frame_unwind = {
 140   SIGTRAMP_FRAME,
 141   vaxobsd_sigtramp_frame_this_id,
 142   vaxobsd_sigtramp_frame_prev_register
 143 };
 144
 145 static const struct frame_unwind *
 146 vaxobsd_sigtramp_frame_sniffer (struct frame_info *next_frame)
 147 {
 148   if (vaxobsd_sigtramp_p (next_frame))
 149     return &vaxobsd_sigtramp_frame_unwind;
 150
 151   return NULL;
 152 }
 153 \f
 154
 155 /* OpenBSD a.out.  */
 156
 157 static void
 158 vaxobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 159 {
 160   frame_unwind_append_sniffer (gdbarch, vaxobsd_sigtramp_frame_sniffer);
 161 }
 162
 163 /* FIXME: kettenis/20050821: Since OpenBSD/vax binaries are
 164    indistingushable from NetBSD/vax a.out binaries, building a GDB
 165    that should support both these targets will probably not work as
 166    expected.  */
 167 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 168
 169 static enum gdb_osabi
 170 vaxobsd_aout_osabi_sniffer (bfd *abfd)
 171 {
 172   if (strcmp (bfd_get_target (abfd), "a.out-vax-netbsd") == 0)
 173     return GDB_OSABI_OPENBSD_AOUT;
 174
 175   return GDB_OSABI_UNKNOWN;
 176 }
 177 \f
 178
 179 /* Provide a prototype to silence -Wmissing-prototypes.  */
 180 void _initialize_vaxobsd_tdep (void);
 181
 182 void
 183 _initialize_vaxobsd_tdep (void)
 184 {
 185   gdbarch_register_osabi_sniffer (bfd_arch_vax, bfd_target_aout_flavour,
 186                                   vaxobsd_aout_osabi_sniffer);
 187
 188   gdbarch_register_osabi (bfd_arch_vax, 0, GDB_OSABI_OPENBSD_AOUT,
 189                           vaxobsd_init_abi);
 190 }