gdb/i386obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/i386.
   2
   3    Copyright 1988, 1989, 1991, 1992, 1994, 1996, 2000, 2001, 2002,
   4    2003, 2004
   5    Free Software Foundation, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 59 Temple Place - Suite 330,
  22    Boston, MA 02111-1307, USA.  */
  23
  24 #include "defs.h"
  25 #include "arch-utils.h"
  26 #include "frame.h"
  27 #include "gdbcore.h"
  28 #include "regcache.h"
  29 #include "regset.h"
  30 #include "symtab.h"
  31 #include "objfiles.h"
  32 #include "osabi.h"
  33 #include "target.h"
  34
  35 #include "gdb_assert.h"
  36 #include "gdb_string.h"
  37
  38 #include "i386-tdep.h"
  39 #include "i387-tdep.h"
  40 #include "solib-svr4.h"
  41
  42 /* Support for signal handlers.  */
  43
  44 /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
  45    in virtual memory.  The randomness makes it somewhat tricky to
  46    detect it, but fortunately we can rely on the fact that the start
  47    of the sigtramp routine is page-aligned.  By the way, the mapping
  48    is read-only, so you cannot place a breakpoint in the signal
  49    trampoline.  */
  50
  51 /* Default page size.  */
  52 static const int i386obsd_page_size = 4096;
  53
  54 /* Return whether the frame preciding NEXT_FRAME corresponds to an
  55    OpenBSD sigtramp routine.  */
  56
  57 static int
  58 i386obsd_sigtramp_p (struct frame_info *next_frame)
  59 {
  60   CORE_ADDR pc = frame_pc_unwind (next_frame);
  61   CORE_ADDR start_pc = (pc & ~(i386obsd_page_size - 1));
  62   const char sigreturn[] =
  63   {
  64     0xb8,
  65     0x67, 0x00, 0x00, 0x00,     /* movl $SYS_sigreturn, %eax */
  66     0xcd, 0x80                  /* int $0x80 */
  67   };
  68   char *name, *buf;
  69
  70   /* If the function has a valid symbol name, it isn't a
  71      trampoline.  */
  72   find_pc_partial_function (pc, &name, NULL, NULL);
  73   if (name != NULL)
  74     return 0;
  75
  76   /* If the function lives in a valid section (even without a starting
  77      point) it isn't a trampoline.  */
  78   if (find_pc_section (pc) != NULL)
  79     return 0;
  80
  81   /* If we can't read the instructions at START_PC, return zero.  */
  82   buf = alloca (sizeof sigreturn);
  83   if (target_read_memory (start_pc + 0x14, buf, sizeof sigreturn))
  84     return 0;
  85
  86   /* Check for sigreturn(2).  */
  87   if (memcmp (buf, sigreturn, sizeof sigreturn) == 0)
  88     return 1;
  89
  90   return 0;
  91 }
  92 \f
  93 /* Mapping between the general-purpose registers in `struct reg'
  94    format and GDB's register cache layout.  */
  95
  96 /* From <machine/reg.h>.  */
  97 static int i386obsd_r_reg_offset[] =
  98 {
  99   0 * 4,                        /* %eax */
 100   1 * 4,                        /* %ecx */
 101   2 * 4,                        /* %edx */
 102   3 * 4,                        /* %ebx */
 103   4 * 4,                        /* %esp */
 104   5 * 4,                        /* %ebp */
 105   6 * 4,                        /* %esi */
 106   7 * 4,                        /* %edi */
 107   8 * 4,                        /* %eip */
 108   9 * 4,                        /* %eflags */
 109   10 * 4,                       /* %cs */
 110   11 * 4,                       /* %ss */
 111   12 * 4,                       /* %ds */
 112   13 * 4,                       /* %es */
 113   14 * 4,                       /* %fs */
 114   15 * 4                        /* %gs */
 115 };
 116
 117 static void
 118 i386obsd_aout_supply_regset (const struct regset *regset,
 119                              struct regcache *regcache, int regnum,
 120                              const void *regs, size_t len)
 121 {
 122   const struct gdbarch_tdep *tdep = regset->descr;
 123
 124   gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE);
 125
 126   i386_supply_gregset (regset, regcache, regnum, regs, tdep->sizeof_gregset);
 127   i387_supply_fsave (regcache, regnum, (char *) regs + tdep->sizeof_gregset);
 128 }
 129
 130 static const struct regset *
 131 i386obsd_aout_regset_from_core_section (struct gdbarch *gdbarch,
 132                                         const char *sect_name,
 133                                         size_t sect_size)
 134 {
 135   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 136
 137   /* OpenBSD a.out core dumps don't use seperate register sets for the
 138      general-purpose and floating-point registers.  */
 139
 140   if (strcmp (sect_name, ".reg") == 0
 141       && sect_size >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE)
 142     {
 143       if (tdep->gregset == NULL)
 144         {
 145           tdep->gregset = XMALLOC (struct regset);
 146           tdep->gregset->descr = tdep;
 147           tdep->gregset->supply_regset = i386obsd_aout_supply_regset;
 148         }
 149       return tdep->gregset;
 150     }
 151
 152   return NULL;
 153 }
 154 \f
 155
 156 /* Sigtramp routine location for OpenBSD 3.1 and earlier releases.  */
 157 CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20;
 158 CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0;
 159
 160 /* From <machine/signal.h>.  */
 161 int i386obsd_sc_reg_offset[I386_NUM_GREGS] =
 162 {
 163   10 * 4,                       /* %eax */
 164   9 * 4,                        /* %ecx */
 165   8 * 4,                        /* %edx */
 166   7 * 4,                        /* %ebx */
 167   14 * 4,                       /* %esp */
 168   6 * 4,                        /* %ebp */
 169   5 * 4,                        /* %esi */
 170   4 * 4,                        /* %edi */
 171   11 * 4,                       /* %eip */
 172   13 * 4,                       /* %eflags */
 173   12 * 4,                       /* %cs */
 174   15 * 4,                       /* %ss */
 175   3 * 4,                        /* %ds */
 176   2 * 4,                        /* %es */
 177   1 * 4,                        /* %fs */
 178   0 * 4                         /* %gs */
 179 };
 180
 181 static void
 182 i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 183 {
 184   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 185
 186   /* Obviously OpenBSD is BSD-based.  */
 187   i386bsd_init_abi (info, gdbarch);
 188
 189   /* OpenBSD has a different `struct reg'.  */
 190   tdep->gregset_reg_offset = i386obsd_r_reg_offset;
 191   tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset);
 192   tdep->sizeof_gregset = 16 * 4;
 193
 194   /* OpenBSD uses -freg-struct-return by default.  */
 195   tdep->struct_return = reg_struct_return;
 196
 197   /* OpenBSD uses a different memory layout.  */
 198   tdep->sigtramp_start = i386obsd_sigtramp_start_addr;
 199   tdep->sigtramp_end = i386obsd_sigtramp_end_addr;
 200   tdep->sigtramp_p = i386obsd_sigtramp_p;
 201
 202   /* OpenBSD has a `struct sigcontext' that's different from the
 203      original 4.3 BSD.  */
 204   tdep->sc_reg_offset = i386obsd_sc_reg_offset;
 205   tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
 206 }
 207
 208 /* OpenBSD a.out.  */
 209
 210 static void
 211 i386obsd_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 212 {
 213   i386obsd_init_abi (info, gdbarch);
 214
 215   /* OpenBSD a.out has a single register set.  */
 216   set_gdbarch_regset_from_core_section
 217     (gdbarch, i386obsd_aout_regset_from_core_section);
 218 }
 219
 220 /* OpenBSD ELF.  */
 221
 222 static void
 223 i386obsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 224 {
 225   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 226
 227   /* It's still OpenBSD.  */
 228   i386obsd_init_abi (info, gdbarch);
 229
 230   /* But ELF-based.  */
 231   i386_elf_init_abi (info, gdbarch);
 232
 233   /* OpenBSD ELF uses SVR4-style shared libraries.  */
 234   set_gdbarch_in_solib_call_trampoline
 235     (gdbarch, generic_in_solib_call_trampoline);
 236   set_solib_svr4_fetch_link_map_offsets
 237     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 238 }
 239 \f
 240
 241 /* Provide a prototype to silence -Wmissing-prototypes.  */
 242 void _initialize_i386obsd_tdep (void);
 243
 244 void
 245 _initialize_i386obsd_tdep (void)
 246 {
 247   /* FIXME: kettenis/20021020: Since OpenBSD/i386 binaries are
 248      indistingushable from NetBSD/i386 a.out binaries, building a GDB
 249      that should support both these targets will probably not work as
 250      expected.  */
 251 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 252
 253   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_AOUT,
 254                           i386obsd_aout_init_abi);
 255   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_ELF,
 256                           i386obsd_elf_init_abi);
 257 }