gdb/i386nbsd-tdep.c

   1 /* Target-dependent code for NetBSD/i386.
   2
   3    Copyright (C) 1988, 1989, 1991, 1992, 1994, 1996, 2000, 2001, 2002, 2003,
   4    2004, 2007 Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "arch-utils.h"
  23 #include "frame.h"
  24 #include "gdbcore.h"
  25 #include "regcache.h"
  26 #include "regset.h"
  27 #include "osabi.h"
  28 #include "symtab.h"
  29
  30 #include "gdb_assert.h"
  31 #include "gdb_string.h"
  32
  33 #include "i386-tdep.h"
  34 #include "i387-tdep.h"
  35 #include "nbsd-tdep.h"
  36 #include "solib-svr4.h"
  37
  38 /* From <machine/reg.h>.  */
  39 static int i386nbsd_r_reg_offset[] =
  40 {
  41   0 * 4,                        /* %eax */
  42   1 * 4,                        /* %ecx */
  43   2 * 4,                        /* %edx */
  44   3 * 4,                        /* %ebx */
  45   4 * 4,                        /* %esp */
  46   5 * 4,                        /* %ebp */
  47   6 * 4,                        /* %esi */
  48   7 * 4,                        /* %edi */
  49   8 * 4,                        /* %eip */
  50   9 * 4,                        /* %eflags */
  51   10 * 4,                       /* %cs */
  52   11 * 4,                       /* %ss */
  53   12 * 4,                       /* %ds */
  54   13 * 4,                       /* %es */
  55   14 * 4,                       /* %fs */
  56   15 * 4                        /* %gs */
  57 };
  58
  59 /* Under NetBSD/i386, signal handler invocations can be identified by the
  60    designated code sequence that is used to return from a signal handler.
  61    In particular, the return address of a signal handler points to the
  62    following code sequence:
  63
  64         leal    0x10(%esp), %eax
  65         pushl   %eax
  66         pushl   %eax
  67         movl    $0x127, %eax            # __sigreturn14
  68         int     $0x80
  69
  70    Each instruction has a unique encoding, so we simply attempt to match
  71    the instruction the PC is pointing to with any of the above instructions.
  72    If there is a hit, we know the offset to the start of the designated
  73    sequence and can then check whether we really are executing in the
  74    signal trampoline.  If not, -1 is returned, otherwise the offset from the
  75    start of the return sequence is returned.  */
  76 #define RETCODE_INSN1           0x8d
  77 #define RETCODE_INSN2           0x50
  78 #define RETCODE_INSN3           0x50
  79 #define RETCODE_INSN4           0xb8
  80 #define RETCODE_INSN5           0xcd
  81
  82 #define RETCODE_INSN2_OFF       4
  83 #define RETCODE_INSN3_OFF       5
  84 #define RETCODE_INSN4_OFF       6
  85 #define RETCODE_INSN5_OFF       11
  86
  87 static const unsigned char sigtramp_retcode[] =
  88 {
  89   RETCODE_INSN1, 0x44, 0x24, 0x10,
  90   RETCODE_INSN2,
  91   RETCODE_INSN3,
  92   RETCODE_INSN4, 0x27, 0x01, 0x00, 0x00,
  93   RETCODE_INSN5, 0x80,
  94 };
  95
  96 static LONGEST
  97 i386nbsd_sigtramp_offset (struct frame_info *next_frame)
  98 {
  99   CORE_ADDR pc = frame_pc_unwind (next_frame);
 100   unsigned char ret[sizeof(sigtramp_retcode)], insn;
 101   LONGEST off;
 102   int i;
 103
 104   if (!safe_frame_unwind_memory (next_frame, pc, &insn, 1))
 105     return -1;
 106
 107   switch (insn)
 108     {
 109     case RETCODE_INSN1:
 110       off = 0;
 111       break;
 112
 113     case RETCODE_INSN2:
 114       /* INSN2 and INSN3 are the same.  Read at the location of PC+1
 115          to determine if we're actually looking at INSN2 or INSN3.  */
 116       if (!safe_frame_unwind_memory (next_frame, pc + 1, &insn, 1))
 117         return -1;
 118
 119       if (insn == RETCODE_INSN3)
 120         off = RETCODE_INSN2_OFF;
 121       else
 122         off = RETCODE_INSN3_OFF;
 123       break;
 124
 125     case RETCODE_INSN4:
 126       off = RETCODE_INSN4_OFF;
 127       break;
 128
 129     case RETCODE_INSN5:
 130       off = RETCODE_INSN5_OFF;
 131       break;
 132
 133     default:
 134       return -1;
 135     }
 136
 137   pc -= off;
 138
 139   if (!safe_frame_unwind_memory (next_frame, pc, ret, sizeof (ret)))
 140     return -1;
 141
 142   if (memcmp (ret, sigtramp_retcode, sizeof (ret)) == 0)
 143     return off;
 144
 145   return -1;
 146 }
 147
 148 /* Return whether the frame preceding NEXT_FRAME corresponds to a
 149    NetBSD sigtramp routine.  */
 150
 151 static int
 152 i386nbsd_sigtramp_p (struct frame_info *next_frame)
 153 {
 154   CORE_ADDR pc = frame_pc_unwind (next_frame);
 155   char *name;
 156
 157   find_pc_partial_function (pc, &name, NULL, NULL);
 158   return (nbsd_pc_in_sigtramp (pc, name)
 159           || i386nbsd_sigtramp_offset (next_frame) >= 0);
 160 }
 161
 162 /* From <machine/signal.h>.  */
 163 int i386nbsd_sc_reg_offset[] =
 164 {
 165   10 * 4,                       /* %eax */
 166   9 * 4,                        /* %ecx */
 167   8 * 4,                        /* %edx */
 168   7 * 4,                        /* %ebx */
 169   14 * 4,                       /* %esp */
 170   6 * 4,                        /* %ebp */
 171   5 * 4,                        /* %esi */
 172   4 * 4,                        /* %edi */
 173   11 * 4,                       /* %eip */
 174   13 * 4,                       /* %eflags */
 175   12 * 4,                       /* %cs */
 176   15 * 4,                       /* %ss */
 177   3 * 4,                        /* %ds */
 178   2 * 4,                        /* %es */
 179   1 * 4,                        /* %fs */
 180   0 * 4                         /* %gs */
 181 };
 182
 183 static void
 184 i386nbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 185 {
 186   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 187
 188   /* Obviously NetBSD is BSD-based.  */
 189   i386bsd_init_abi (info, gdbarch);
 190
 191   /* NetBSD has a different `struct reg'.  */
 192   tdep->gregset_reg_offset = i386nbsd_r_reg_offset;
 193   tdep->gregset_num_regs = ARRAY_SIZE (i386nbsd_r_reg_offset);
 194   tdep->sizeof_gregset = 16 * 4;
 195
 196   /* NetBSD has different signal trampoline conventions.  */
 197   tdep->sigtramp_start = 0;
 198   tdep->sigtramp_end = 0;
 199   tdep->sigtramp_p = i386nbsd_sigtramp_p;
 200
 201   /* NetBSD uses -freg-struct-return by default.  */
 202   tdep->struct_return = reg_struct_return;
 203
 204   /* NetBSD has a `struct sigcontext' that's different from the
 205      original 4.3 BSD.  */
 206   tdep->sc_reg_offset = i386nbsd_sc_reg_offset;
 207   tdep->sc_num_regs = ARRAY_SIZE (i386nbsd_sc_reg_offset);
 208 }
 209
 210 /* NetBSD ELF.  */
 211
 212 static void
 213 i386nbsdelf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 214 {
 215   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 216
 217   /* It's still NetBSD.  */
 218   i386nbsd_init_abi (info, gdbarch);
 219
 220   /* But ELF-based.  */
 221   i386_elf_init_abi (info, gdbarch);
 222
 223   /* NetBSD ELF uses SVR4-style shared libraries.  */
 224   set_solib_svr4_fetch_link_map_offsets
 225     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 226
 227   /* NetBSD ELF uses -fpcc-struct-return by default.  */
 228   tdep->struct_return = pcc_struct_return;
 229 }
 230
 231 void
 232 _initialize_i386nbsd_tdep (void)
 233 {
 234   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_NETBSD_ELF,
 235                           i386nbsdelf_init_abi);
 236 }