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   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   /* Allocate buffer.  */
  82   buf = alloca (sizeof sigreturn);
  83
  84   /* If we can't read the instructions at START_PC, return zero.  */
  85   if (target_read_memory (start_pc + 0x0a, buf, sizeof sigreturn))
  86     return 0;
  87
  88   /* Check for sigreturn(2).  */
  89   if (memcmp (buf, sigreturn, sizeof sigreturn) == 0)
  90     return 1;
  91
  92   /* If we can't read the instructions at START_PC, return zero.  */
  93   if (target_read_memory (start_pc + 0x14, buf, sizeof sigreturn))
  94     return 0;
  95
  96   /* Check for sigreturn(2) (again).  */
  97   if (memcmp (buf, sigreturn, sizeof sigreturn) == 0)
  98     return 1;
  99
 100   return 0;
 101 }
 102 \f
 103 /* Mapping between the general-purpose registers in `struct reg'
 104    format and GDB's register cache layout.  */
 105
 106 /* From <machine/reg.h>.  */
 107 static int i386obsd_r_reg_offset[] =
 108 {
 109   0 * 4,                        /* %eax */
 110   1 * 4,                        /* %ecx */
 111   2 * 4,                        /* %edx */
 112   3 * 4,                        /* %ebx */
 113   4 * 4,                        /* %esp */
 114   5 * 4,                        /* %ebp */
 115   6 * 4,                        /* %esi */
 116   7 * 4,                        /* %edi */
 117   8 * 4,                        /* %eip */
 118   9 * 4,                        /* %eflags */
 119   10 * 4,                       /* %cs */
 120   11 * 4,                       /* %ss */
 121   12 * 4,                       /* %ds */
 122   13 * 4,                       /* %es */
 123   14 * 4,                       /* %fs */
 124   15 * 4                        /* %gs */
 125 };
 126
 127 static void
 128 i386obsd_aout_supply_regset (const struct regset *regset,
 129                              struct regcache *regcache, int regnum,
 130                              const void *regs, size_t len)
 131 {
 132   const struct gdbarch_tdep *tdep = gdbarch_tdep (regset->arch);
 133
 134   gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE);
 135
 136   i386_supply_gregset (regset, regcache, regnum, regs, tdep->sizeof_gregset);
 137   i387_supply_fsave (regcache, regnum, (char *) regs + tdep->sizeof_gregset);
 138 }
 139
 140 static const struct regset *
 141 i386obsd_aout_regset_from_core_section (struct gdbarch *gdbarch,
 142                                         const char *sect_name,
 143                                         size_t sect_size)
 144 {
 145   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 146
 147   /* OpenBSD a.out core dumps don't use seperate register sets for the
 148      general-purpose and floating-point registers.  */
 149
 150   if (strcmp (sect_name, ".reg") == 0
 151       && sect_size >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE)
 152     {
 153       if (tdep->gregset == NULL)
 154         tdep->gregset =
 155           regset_alloc (gdbarch, i386obsd_aout_supply_regset, NULL);
 156       return tdep->gregset;
 157     }
 158
 159   return NULL;
 160 }
 161 \f
 162
 163 /* Sigtramp routine location for OpenBSD 3.1 and earlier releases.  */
 164 CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20;
 165 CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0;
 166
 167 /* From <machine/signal.h>.  */
 168 int i386obsd_sc_reg_offset[I386_NUM_GREGS] =
 169 {
 170   10 * 4,                       /* %eax */
 171   9 * 4,                        /* %ecx */
 172   8 * 4,                        /* %edx */
 173   7 * 4,                        /* %ebx */
 174   14 * 4,                       /* %esp */
 175   6 * 4,                        /* %ebp */
 176   5 * 4,                        /* %esi */
 177   4 * 4,                        /* %edi */
 178   11 * 4,                       /* %eip */
 179   13 * 4,                       /* %eflags */
 180   12 * 4,                       /* %cs */
 181   15 * 4,                       /* %ss */
 182   3 * 4,                        /* %ds */
 183   2 * 4,                        /* %es */
 184   1 * 4,                        /* %fs */
 185   0 * 4                         /* %gs */
 186 };
 187
 188 static void
 189 i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 190 {
 191   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 192
 193   /* Obviously OpenBSD is BSD-based.  */
 194   i386bsd_init_abi (info, gdbarch);
 195
 196   /* OpenBSD has a different `struct reg'.  */
 197   tdep->gregset_reg_offset = i386obsd_r_reg_offset;
 198   tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset);
 199   tdep->sizeof_gregset = 16 * 4;
 200
 201   /* OpenBSD uses -freg-struct-return by default.  */
 202   tdep->struct_return = reg_struct_return;
 203
 204   /* OpenBSD uses a different memory layout.  */
 205   tdep->sigtramp_start = i386obsd_sigtramp_start_addr;
 206   tdep->sigtramp_end = i386obsd_sigtramp_end_addr;
 207   tdep->sigtramp_p = i386obsd_sigtramp_p;
 208
 209   /* OpenBSD has a `struct sigcontext' that's different from the
 210      original 4.3 BSD.  */
 211   tdep->sc_reg_offset = i386obsd_sc_reg_offset;
 212   tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
 213 }
 214
 215 /* OpenBSD a.out.  */
 216
 217 static void
 218 i386obsd_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 219 {
 220   i386obsd_init_abi (info, gdbarch);
 221
 222   /* OpenBSD a.out has a single register set.  */
 223   set_gdbarch_regset_from_core_section
 224     (gdbarch, i386obsd_aout_regset_from_core_section);
 225 }
 226
 227 /* OpenBSD ELF.  */
 228
 229 static void
 230 i386obsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 231 {
 232   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 233
 234   /* It's still OpenBSD.  */
 235   i386obsd_init_abi (info, gdbarch);
 236
 237   /* But ELF-based.  */
 238   i386_elf_init_abi (info, gdbarch);
 239
 240   /* OpenBSD ELF uses SVR4-style shared libraries.  */
 241   set_gdbarch_in_solib_call_trampoline
 242     (gdbarch, generic_in_solib_call_trampoline);
 243   set_solib_svr4_fetch_link_map_offsets
 244     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 245 }
 246 \f
 247
 248 /* Provide a prototype to silence -Wmissing-prototypes.  */
 249 void _initialize_i386obsd_tdep (void);
 250
 251 void
 252 _initialize_i386obsd_tdep (void)
 253 {
 254   /* FIXME: kettenis/20021020: Since OpenBSD/i386 binaries are
 255      indistingushable from NetBSD/i386 a.out binaries, building a GDB
 256      that should support both these targets will probably not work as
 257      expected.  */
 258 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 259
 260   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_AOUT,
 261                           i386obsd_aout_init_abi);
 262   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_ELF,
 263                           i386obsd_elf_init_abi);
 264 }