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 preceding 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   size_t buflen = sizeof sigreturn;
  69   char *name, *buf;
  70
  71   /* If the function has a valid symbol name, it isn't a
  72      trampoline.  */
  73   find_pc_partial_function (pc, &name, NULL, NULL);
  74   if (name != NULL)
  75     return 0;
  76
  77   /* If the function lives in a valid section (even without a starting
  78      point) it isn't a trampoline.  */
  79   if (find_pc_section (pc) != NULL)
  80     return 0;
  81
  82   /* Allocate buffer.  */
  83   buf = alloca (buflen);
  84
  85   /* If we can't read the instructions at START_PC, return zero.  */
  86   if (!safe_frame_unwind_memory (next_frame, start_pc + 0x0a, buf, buflen))
  87     return 0;
  88
  89   /* Check for sigreturn(2).  */
  90   if (memcmp (buf, sigreturn, buflen) == 0)
  91     return 1;
  92
  93   /* If we can't read the instructions at START_PC, return zero.  */
  94   if (!safe_frame_unwind_memory (next_frame, start_pc + 0x14, buf, buflen))
  95     return 0;
  96
  97   /* Check for sigreturn(2) (again).  */
  98   if (memcmp (buf, sigreturn, buflen) == 0)
  99     return 1;
 100
 101   return 0;
 102 }
 103 \f
 104 /* Mapping between the general-purpose registers in `struct reg'
 105    format and GDB's register cache layout.  */
 106
 107 /* From <machine/reg.h>.  */
 108 static int i386obsd_r_reg_offset[] =
 109 {
 110   0 * 4,                        /* %eax */
 111   1 * 4,                        /* %ecx */
 112   2 * 4,                        /* %edx */
 113   3 * 4,                        /* %ebx */
 114   4 * 4,                        /* %esp */
 115   5 * 4,                        /* %ebp */
 116   6 * 4,                        /* %esi */
 117   7 * 4,                        /* %edi */
 118   8 * 4,                        /* %eip */
 119   9 * 4,                        /* %eflags */
 120   10 * 4,                       /* %cs */
 121   11 * 4,                       /* %ss */
 122   12 * 4,                       /* %ds */
 123   13 * 4,                       /* %es */
 124   14 * 4,                       /* %fs */
 125   15 * 4                        /* %gs */
 126 };
 127
 128 static void
 129 i386obsd_aout_supply_regset (const struct regset *regset,
 130                              struct regcache *regcache, int regnum,
 131                              const void *regs, size_t len)
 132 {
 133   const struct gdbarch_tdep *tdep = gdbarch_tdep (regset->arch);
 134
 135   gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE);
 136
 137   i386_supply_gregset (regset, regcache, regnum, regs, tdep->sizeof_gregset);
 138   i387_supply_fsave (regcache, regnum, (char *) regs + tdep->sizeof_gregset);
 139 }
 140
 141 static const struct regset *
 142 i386obsd_aout_regset_from_core_section (struct gdbarch *gdbarch,
 143                                         const char *sect_name,
 144                                         size_t sect_size)
 145 {
 146   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 147
 148   /* OpenBSD a.out core dumps don't use seperate register sets for the
 149      general-purpose and floating-point registers.  */
 150
 151   if (strcmp (sect_name, ".reg") == 0
 152       && sect_size >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE)
 153     {
 154       if (tdep->gregset == NULL)
 155         tdep->gregset =
 156           regset_alloc (gdbarch, i386obsd_aout_supply_regset, NULL);
 157       return tdep->gregset;
 158     }
 159
 160   return NULL;
 161 }
 162 \f
 163
 164 /* Sigtramp routine location for OpenBSD 3.1 and earlier releases.  */
 165 CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20;
 166 CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0;
 167
 168 /* From <machine/signal.h>.  */
 169 int i386obsd_sc_reg_offset[I386_NUM_GREGS] =
 170 {
 171   10 * 4,                       /* %eax */
 172   9 * 4,                        /* %ecx */
 173   8 * 4,                        /* %edx */
 174   7 * 4,                        /* %ebx */
 175   14 * 4,                       /* %esp */
 176   6 * 4,                        /* %ebp */
 177   5 * 4,                        /* %esi */
 178   4 * 4,                        /* %edi */
 179   11 * 4,                       /* %eip */
 180   13 * 4,                       /* %eflags */
 181   12 * 4,                       /* %cs */
 182   15 * 4,                       /* %ss */
 183   3 * 4,                        /* %ds */
 184   2 * 4,                        /* %es */
 185   1 * 4,                        /* %fs */
 186   0 * 4                         /* %gs */
 187 };
 188
 189 static void
 190 i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 191 {
 192   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 193
 194   /* Obviously OpenBSD is BSD-based.  */
 195   i386bsd_init_abi (info, gdbarch);
 196
 197   /* OpenBSD has a different `struct reg'.  */
 198   tdep->gregset_reg_offset = i386obsd_r_reg_offset;
 199   tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset);
 200   tdep->sizeof_gregset = 16 * 4;
 201
 202   /* OpenBSD uses -freg-struct-return by default.  */
 203   tdep->struct_return = reg_struct_return;
 204
 205   /* OpenBSD uses a different memory layout.  */
 206   tdep->sigtramp_start = i386obsd_sigtramp_start_addr;
 207   tdep->sigtramp_end = i386obsd_sigtramp_end_addr;
 208   tdep->sigtramp_p = i386obsd_sigtramp_p;
 209
 210   /* OpenBSD has a `struct sigcontext' that's different from the
 211      original 4.3 BSD.  */
 212   tdep->sc_reg_offset = i386obsd_sc_reg_offset;
 213   tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
 214 }
 215
 216 /* OpenBSD a.out.  */
 217
 218 static void
 219 i386obsd_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 220 {
 221   i386obsd_init_abi (info, gdbarch);
 222
 223   /* OpenBSD a.out has a single register set.  */
 224   set_gdbarch_regset_from_core_section
 225     (gdbarch, i386obsd_aout_regset_from_core_section);
 226 }
 227
 228 /* OpenBSD ELF.  */
 229
 230 static void
 231 i386obsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 232 {
 233   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 234
 235   /* It's still OpenBSD.  */
 236   i386obsd_init_abi (info, gdbarch);
 237
 238   /* But ELF-based.  */
 239   i386_elf_init_abi (info, gdbarch);
 240
 241   /* OpenBSD ELF uses SVR4-style shared libraries.  */
 242   set_solib_svr4_fetch_link_map_offsets
 243     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 244 }
 245 \f
 246
 247 /* Provide a prototype to silence -Wmissing-prototypes.  */
 248 void _initialize_i386obsd_tdep (void);
 249
 250 void
 251 _initialize_i386obsd_tdep (void)
 252 {
 253   /* FIXME: kettenis/20021020: Since OpenBSD/i386 binaries are
 254      indistingushable from NetBSD/i386 a.out binaries, building a GDB
 255      that should support both these targets will probably not work as
 256      expected.  */
 257 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 258
 259   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_AOUT,
 260                           i386obsd_aout_init_abi);
 261   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_ELF,
 262                           i386obsd_elf_init_abi);
 263 }