gdb/trad-frame.c

   1 /* Traditional frame unwind support, for GDB the GNU Debugger.
   2
   3    Copyright (C) 2003-2021 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 3 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, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "frame.h"
  22 #include "trad-frame.h"
  23 #include "regcache.h"
  24 #include "frame-unwind.h"
  25 #include "target.h"
  26 #include "value.h"
  27 #include "gdbarch.h"
  28 #include "gdbsupport/traits.h"
  29
  30 struct trad_frame_cache
  31 {
  32   struct frame_info *this_frame;
  33   CORE_ADDR this_base;
  34   trad_frame_saved_reg *prev_regs;
  35   struct frame_id this_id;
  36 };
  37
  38 struct trad_frame_cache *
  39 trad_frame_cache_zalloc (struct frame_info *this_frame)
  40 {
  41   struct trad_frame_cache *this_trad_cache;
  42
  43   this_trad_cache = FRAME_OBSTACK_ZALLOC (struct trad_frame_cache);
  44   this_trad_cache->prev_regs = trad_frame_alloc_saved_regs (this_frame);
  45   this_trad_cache->this_frame = this_frame;
  46   return this_trad_cache;
  47 }
  48
  49 /* See trad-frame.h.  */
  50
  51 void
  52 trad_frame_reset_saved_regs (struct gdbarch *gdbarch,
  53                              trad_frame_saved_reg *regs)
  54 {
  55   int numregs = gdbarch_num_cooked_regs (gdbarch);
  56
  57   for (int regnum = 0; regnum < numregs; regnum++)
  58     regs[regnum].set_realreg (regnum);
  59 }
  60
  61 trad_frame_saved_reg *
  62 trad_frame_alloc_saved_regs (struct gdbarch *gdbarch)
  63 {
  64 #ifdef HAVE_IS_TRIVIALLY_CONSTRUCTIBLE
  65   gdb_static_assert (std::is_trivially_constructible<trad_frame_saved_reg>::value);
  66 #endif
  67
  68   int numregs = gdbarch_num_cooked_regs (gdbarch);
  69   trad_frame_saved_reg *this_saved_regs
  70     = FRAME_OBSTACK_CALLOC (numregs, trad_frame_saved_reg);
  71
  72   /* For backwards compatibility, initialize all the register values to
  73      REALREG, with register 0 stored in 0, register 1 stored in 1 and so
  74      on.  */
  75   trad_frame_reset_saved_regs (gdbarch, this_saved_regs);
  76
  77   return this_saved_regs;
  78 }
  79
  80 /* A traditional frame is unwound by analysing the function prologue
  81    and using the information gathered to track registers.  For
  82    non-optimized frames, the technique is reliable (just need to check
  83    for all potential instruction sequences).  */
  84
  85 trad_frame_saved_reg *
  86 trad_frame_alloc_saved_regs (struct frame_info *this_frame)
  87 {
  88   struct gdbarch *gdbarch = get_frame_arch (this_frame);
  89
  90   return trad_frame_alloc_saved_regs (gdbarch);
  91 }
  92
  93 void
  94 trad_frame_set_reg_value (struct trad_frame_cache *this_trad_cache,
  95                           int regnum, LONGEST val)
  96 {
  97   /* External interface for users of trad_frame_cache
  98      (who cannot access the prev_regs object directly).  */
  99   this_trad_cache->prev_regs[regnum].set_value (val);
 100 }
 101
 102 void
 103 trad_frame_set_reg_realreg (struct trad_frame_cache *this_trad_cache,
 104                             int regnum, int realreg)
 105 {
 106   this_trad_cache->prev_regs[regnum].set_realreg (realreg);
 107 }
 108
 109 void
 110 trad_frame_set_reg_addr (struct trad_frame_cache *this_trad_cache,
 111                          int regnum, CORE_ADDR addr)
 112 {
 113   this_trad_cache->prev_regs[regnum].set_addr (addr);
 114 }
 115
 116 void
 117 trad_frame_set_reg_regmap (struct trad_frame_cache *this_trad_cache,
 118                            const struct regcache_map_entry *regmap,
 119                            CORE_ADDR addr, size_t size)
 120 {
 121   struct gdbarch *gdbarch = get_frame_arch (this_trad_cache->this_frame);
 122   int offs = 0, count;
 123
 124   for (; (count = regmap->count) != 0; regmap++)
 125     {
 126       int regno = regmap->regno;
 127       int slot_size = regmap->size;
 128
 129       if (slot_size == 0 && regno != REGCACHE_MAP_SKIP)
 130         slot_size = register_size (gdbarch, regno);
 131
 132       if (offs + slot_size > size)
 133         break;
 134
 135       if (regno == REGCACHE_MAP_SKIP)
 136         offs += count * slot_size;
 137       else
 138         for (; count--; regno++, offs += slot_size)
 139           {
 140             /* Mimic the semantics of regcache::transfer_regset if a
 141                register slot's size does not match the size of a
 142                register.
 143
 144                If a register slot is larger than a register, assume
 145                the register's value is stored in the first N bytes of
 146                the slot and ignore the remaining bytes.
 147
 148                If the register slot is smaller than the register,
 149                assume that the slot contains the low N bytes of the
 150                register's value.  Since trad_frame assumes that
 151                registers stored by address are sized according to the
 152                register, read the low N bytes and zero-extend them to
 153                generate a register value.  */
 154             if (slot_size >= register_size (gdbarch, regno))
 155               trad_frame_set_reg_addr (this_trad_cache, regno, addr + offs);
 156             else
 157               {
 158                 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 159                 gdb_byte buf[slot_size];
 160
 161                 if (target_read_memory (addr + offs, buf, sizeof buf) == 0)
 162                   {
 163                     LONGEST val
 164                       = extract_unsigned_integer (buf, sizeof buf, byte_order);
 165                     trad_frame_set_reg_value (this_trad_cache, regno, val);
 166                   }
 167               }
 168           }
 169     }
 170 }
 171
 172 /* See trad-frame.h.  */
 173
 174 void
 175 trad_frame_set_reg_value_bytes (struct trad_frame_cache *this_trad_cache,
 176                                 int regnum,
 177                                 gdb::array_view<const gdb_byte> bytes)
 178 {
 179   /* External interface for users of trad_frame_cache
 180      (who cannot access the prev_regs object directly).  */
 181   this_trad_cache->prev_regs[regnum].set_value_bytes (bytes);
 182 }
 183
 184
 185
 186 struct value *
 187 trad_frame_get_prev_register (struct frame_info *this_frame,
 188                               trad_frame_saved_reg this_saved_regs[],
 189                               int regnum)
 190 {
 191   if (this_saved_regs[regnum].is_addr ())
 192     /* The register was saved in memory.  */
 193     return frame_unwind_got_memory (this_frame, regnum,
 194                                     this_saved_regs[regnum].addr ());
 195   else if (this_saved_regs[regnum].is_realreg ())
 196     return frame_unwind_got_register (this_frame, regnum,
 197                                       this_saved_regs[regnum].realreg ());
 198   else if (this_saved_regs[regnum].is_value ())
 199     /* The register's value is available.  */
 200     return frame_unwind_got_constant (this_frame, regnum,
 201                                       this_saved_regs[regnum].value ());
 202   else if (this_saved_regs[regnum].is_value_bytes ())
 203     /* The register's value is available as a sequence of bytes.  */
 204     return frame_unwind_got_bytes (this_frame, regnum,
 205                                    this_saved_regs[regnum].value_bytes ());
 206   else
 207     return frame_unwind_got_optimized (this_frame, regnum);
 208 }
 209
 210 struct value *
 211 trad_frame_get_register (struct trad_frame_cache *this_trad_cache,
 212                          struct frame_info *this_frame,
 213                          int regnum)
 214 {
 215   return trad_frame_get_prev_register (this_frame, this_trad_cache->prev_regs,
 216                                        regnum);
 217 }
 218
 219 void
 220 trad_frame_set_id (struct trad_frame_cache *this_trad_cache,
 221                    struct frame_id this_id)
 222 {
 223   this_trad_cache->this_id = this_id;
 224 }
 225
 226 void
 227 trad_frame_get_id (struct trad_frame_cache *this_trad_cache,
 228                    struct frame_id *this_id)
 229 {
 230   (*this_id) = this_trad_cache->this_id;
 231 }
 232
 233 void
 234 trad_frame_set_this_base (struct trad_frame_cache *this_trad_cache,
 235                           CORE_ADDR this_base)
 236 {
 237   this_trad_cache->this_base = this_base;
 238 }
 239
 240 CORE_ADDR
 241 trad_frame_get_this_base (struct trad_frame_cache *this_trad_cache)
 242 {
 243   return this_trad_cache->this_base;
 244 }