gdb/trad-frame.c

   1 /* Traditional frame unwind support, for GDB the GNU Debugger.
   2
   3    Copyright (C) 2003-2025 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 "extract-store-integer.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   frame_info_ptr 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 (const frame_info_ptr &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   static_assert (std::is_trivially_constructible<trad_frame_saved_reg>::value);
  65
  66   int numregs = gdbarch_num_cooked_regs (gdbarch);
  67   trad_frame_saved_reg *this_saved_regs
  68     = FRAME_OBSTACK_CALLOC (numregs, trad_frame_saved_reg);
  69
  70   /* For backwards compatibility, initialize all the register values to
  71      REALREG, with register 0 stored in 0, register 1 stored in 1 and so
  72      on.  */
  73   trad_frame_reset_saved_regs (gdbarch, this_saved_regs);
  74
  75   return this_saved_regs;
  76 }
  77
  78 /* A traditional frame is unwound by analysing the function prologue
  79    and using the information gathered to track registers.  For
  80    non-optimized frames, the technique is reliable (just need to check
  81    for all potential instruction sequences).  */
  82
  83 trad_frame_saved_reg *
  84 trad_frame_alloc_saved_regs (const frame_info_ptr &this_frame)
  85 {
  86   struct gdbarch *gdbarch = get_frame_arch (this_frame);
  87
  88   return trad_frame_alloc_saved_regs (gdbarch);
  89 }
  90
  91 void
  92 trad_frame_set_reg_value (struct trad_frame_cache *this_trad_cache,
  93                           int regnum, LONGEST val)
  94 {
  95   /* External interface for users of trad_frame_cache
  96      (who cannot access the prev_regs object directly).  */
  97   this_trad_cache->prev_regs[regnum].set_value (val);
  98 }
  99
 100 void
 101 trad_frame_set_reg_realreg (struct trad_frame_cache *this_trad_cache,
 102                             int regnum, int realreg)
 103 {
 104   this_trad_cache->prev_regs[regnum].set_realreg (realreg);
 105 }
 106
 107 void
 108 trad_frame_set_reg_addr (struct trad_frame_cache *this_trad_cache,
 109                          int regnum, CORE_ADDR addr)
 110 {
 111   this_trad_cache->prev_regs[regnum].set_addr (addr);
 112 }
 113
 114 void
 115 trad_frame_set_reg_regmap (struct trad_frame_cache *this_trad_cache,
 116                            const struct regcache_map_entry *regmap,
 117                            CORE_ADDR addr, size_t size)
 118 {
 119   struct gdbarch *gdbarch = get_frame_arch (this_trad_cache->this_frame);
 120   int offs = 0, count;
 121
 122   for (; (count = regmap->count) != 0; regmap++)
 123     {
 124       int regno = regmap->regno;
 125       int slot_size = regmap->size;
 126
 127       if (slot_size == 0 && regno != REGCACHE_MAP_SKIP)
 128         slot_size = register_size (gdbarch, regno);
 129
 130       if (offs + slot_size > size)
 131         break;
 132
 133       if (regno == REGCACHE_MAP_SKIP)
 134         offs += count * slot_size;
 135       else
 136         for (; count--; regno++, offs += slot_size)
 137           {
 138             /* Mimic the semantics of regcache::transfer_regset if a
 139                register slot's size does not match the size of a
 140                register.
 141
 142                If a register slot is larger than a register, assume
 143                the register's value is stored in the first N bytes of
 144                the slot and ignore the remaining bytes.
 145
 146                If the register slot is smaller than the register,
 147                assume that the slot contains the low N bytes of the
 148                register's value.  Since trad_frame assumes that
 149                registers stored by address are sized according to the
 150                register, read the low N bytes and zero-extend them to
 151                generate a register value.  */
 152             if (slot_size >= register_size (gdbarch, regno))
 153               trad_frame_set_reg_addr (this_trad_cache, regno, addr + offs);
 154             else
 155               {
 156                 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 157                 gdb::byte_vector buf (slot_size);
 158
 159                 if (target_read_memory (addr + offs, buf.data (), buf.size ())
 160                     == 0)
 161                   {
 162                     LONGEST val
 163                       = extract_unsigned_integer (buf.data (), buf.size (),
 164                                                   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 (const frame_info_ptr &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                          const frame_info_ptr &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 }