| 1 | /* Definitions for frame unwinder, for GDB, the GNU debugger. |
| 2 | |
| 3 | Copyright (C) 2003-2020 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 "frame-unwind.h" |
| 23 | #include "dummy-frame.h" |
| 24 | #include "inline-frame.h" |
| 25 | #include "value.h" |
| 26 | #include "regcache.h" |
| 27 | #include "gdb_obstack.h" |
| 28 | #include "target.h" |
| 29 | #include "gdbarch.h" |
| 30 | #include "dwarf2/frame-tailcall.h" |
| 31 | |
| 32 | static struct gdbarch_data *frame_unwind_data; |
| 33 | |
| 34 | struct frame_unwind_table_entry |
| 35 | { |
| 36 | const struct frame_unwind *unwinder; |
| 37 | struct frame_unwind_table_entry *next; |
| 38 | }; |
| 39 | |
| 40 | struct frame_unwind_table |
| 41 | { |
| 42 | struct frame_unwind_table_entry *list; |
| 43 | /* The head of the OSABI part of the search list. */ |
| 44 | struct frame_unwind_table_entry **osabi_head; |
| 45 | }; |
| 46 | |
| 47 | /* A helper function to add an unwinder to a list. LINK says where to |
| 48 | install the new unwinder. The new link is returned. */ |
| 49 | |
| 50 | static struct frame_unwind_table_entry ** |
| 51 | add_unwinder (struct obstack *obstack, const struct frame_unwind *unwinder, |
| 52 | struct frame_unwind_table_entry **link) |
| 53 | { |
| 54 | *link = OBSTACK_ZALLOC (obstack, struct frame_unwind_table_entry); |
| 55 | (*link)->unwinder = unwinder; |
| 56 | return &(*link)->next; |
| 57 | } |
| 58 | |
| 59 | static void * |
| 60 | frame_unwind_init (struct obstack *obstack) |
| 61 | { |
| 62 | struct frame_unwind_table *table |
| 63 | = OBSTACK_ZALLOC (obstack, struct frame_unwind_table); |
| 64 | |
| 65 | /* Start the table out with a few default sniffers. OSABI code |
| 66 | can't override this. */ |
| 67 | struct frame_unwind_table_entry **link = &table->list; |
| 68 | |
| 69 | link = add_unwinder (obstack, &dummy_frame_unwind, link); |
| 70 | /* The DWARF tailcall sniffer must come before the inline sniffer. |
| 71 | Otherwise, we can end up in a situation where a DWARF frame finds |
| 72 | tailcall information, but then the inline sniffer claims a frame |
| 73 | before the tailcall sniffer, resulting in confusion. This is |
| 74 | safe to do always because the tailcall sniffer can only ever be |
| 75 | activated if the newer frame was created using the DWARF |
| 76 | unwinder, and it also found tailcall information. */ |
| 77 | link = add_unwinder (obstack, &dwarf2_tailcall_frame_unwind, link); |
| 78 | link = add_unwinder (obstack, &inline_frame_unwind, link); |
| 79 | |
| 80 | /* The insertion point for OSABI sniffers. */ |
| 81 | table->osabi_head = link; |
| 82 | return table; |
| 83 | } |
| 84 | |
| 85 | void |
| 86 | frame_unwind_prepend_unwinder (struct gdbarch *gdbarch, |
| 87 | const struct frame_unwind *unwinder) |
| 88 | { |
| 89 | struct frame_unwind_table *table |
| 90 | = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data); |
| 91 | struct frame_unwind_table_entry *entry; |
| 92 | |
| 93 | /* Insert the new entry at the start of the list. */ |
| 94 | entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry); |
| 95 | entry->unwinder = unwinder; |
| 96 | entry->next = (*table->osabi_head); |
| 97 | (*table->osabi_head) = entry; |
| 98 | } |
| 99 | |
| 100 | void |
| 101 | frame_unwind_append_unwinder (struct gdbarch *gdbarch, |
| 102 | const struct frame_unwind *unwinder) |
| 103 | { |
| 104 | struct frame_unwind_table *table |
| 105 | = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data); |
| 106 | struct frame_unwind_table_entry **ip; |
| 107 | |
| 108 | /* Find the end of the list and insert the new entry there. */ |
| 109 | for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next); |
| 110 | (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry); |
| 111 | (*ip)->unwinder = unwinder; |
| 112 | } |
| 113 | |
| 114 | /* Call SNIFFER from UNWINDER. If it succeeded set UNWINDER for |
| 115 | THIS_FRAME and return 1. Otherwise the function keeps THIS_FRAME |
| 116 | unchanged and returns 0. */ |
| 117 | |
| 118 | static int |
| 119 | frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache, |
| 120 | const struct frame_unwind *unwinder) |
| 121 | { |
| 122 | int res = 0; |
| 123 | |
| 124 | unsigned int entry_generation = get_frame_cache_generation (); |
| 125 | |
| 126 | frame_prepare_for_sniffer (this_frame, unwinder); |
| 127 | |
| 128 | try |
| 129 | { |
| 130 | res = unwinder->sniffer (unwinder, this_frame, this_cache); |
| 131 | } |
| 132 | catch (const gdb_exception &ex) |
| 133 | { |
| 134 | /* Catch all exceptions, caused by either interrupt or error. |
| 135 | Reset *THIS_CACHE, unless something reinitialized the frame |
| 136 | cache meanwhile, in which case THIS_FRAME/THIS_CACHE are now |
| 137 | dangling. */ |
| 138 | if (get_frame_cache_generation () == entry_generation) |
| 139 | { |
| 140 | *this_cache = NULL; |
| 141 | frame_cleanup_after_sniffer (this_frame); |
| 142 | } |
| 143 | |
| 144 | if (ex.error == NOT_AVAILABLE_ERROR) |
| 145 | { |
| 146 | /* This usually means that not even the PC is available, |
| 147 | thus most unwinders aren't able to determine if they're |
| 148 | the best fit. Keep trying. Fallback prologue unwinders |
| 149 | should always accept the frame. */ |
| 150 | return 0; |
| 151 | } |
| 152 | throw; |
| 153 | } |
| 154 | |
| 155 | if (res) |
| 156 | return 1; |
| 157 | else |
| 158 | { |
| 159 | /* Don't set *THIS_CACHE to NULL here, because sniffer has to do |
| 160 | so. */ |
| 161 | frame_cleanup_after_sniffer (this_frame); |
| 162 | return 0; |
| 163 | } |
| 164 | gdb_assert_not_reached ("frame_unwind_try_unwinder"); |
| 165 | } |
| 166 | |
| 167 | /* Iterate through sniffers for THIS_FRAME frame until one returns with an |
| 168 | unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set |
| 169 | by this function. Possibly initialize THIS_CACHE. */ |
| 170 | |
| 171 | void |
| 172 | frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache) |
| 173 | { |
| 174 | struct gdbarch *gdbarch = get_frame_arch (this_frame); |
| 175 | struct frame_unwind_table *table |
| 176 | = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data); |
| 177 | struct frame_unwind_table_entry *entry; |
| 178 | const struct frame_unwind *unwinder_from_target; |
| 179 | |
| 180 | unwinder_from_target = target_get_unwinder (); |
| 181 | if (unwinder_from_target != NULL |
| 182 | && frame_unwind_try_unwinder (this_frame, this_cache, |
| 183 | unwinder_from_target)) |
| 184 | return; |
| 185 | |
| 186 | unwinder_from_target = target_get_tailcall_unwinder (); |
| 187 | if (unwinder_from_target != NULL |
| 188 | && frame_unwind_try_unwinder (this_frame, this_cache, |
| 189 | unwinder_from_target)) |
| 190 | return; |
| 191 | |
| 192 | for (entry = table->list; entry != NULL; entry = entry->next) |
| 193 | if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder)) |
| 194 | return; |
| 195 | |
| 196 | internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed")); |
| 197 | } |
| 198 | |
| 199 | /* A default frame sniffer which always accepts the frame. Used by |
| 200 | fallback prologue unwinders. */ |
| 201 | |
| 202 | int |
| 203 | default_frame_sniffer (const struct frame_unwind *self, |
| 204 | struct frame_info *this_frame, |
| 205 | void **this_prologue_cache) |
| 206 | { |
| 207 | return 1; |
| 208 | } |
| 209 | |
| 210 | /* The default frame unwinder stop_reason callback. */ |
| 211 | |
| 212 | enum unwind_stop_reason |
| 213 | default_frame_unwind_stop_reason (struct frame_info *this_frame, |
| 214 | void **this_cache) |
| 215 | { |
| 216 | struct frame_id this_id = get_frame_id (this_frame); |
| 217 | |
| 218 | if (frame_id_eq (this_id, outer_frame_id)) |
| 219 | return UNWIND_OUTERMOST; |
| 220 | else |
| 221 | return UNWIND_NO_REASON; |
| 222 | } |
| 223 | |
| 224 | /* See frame-unwind.h. */ |
| 225 | |
| 226 | CORE_ADDR |
| 227 | default_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame) |
| 228 | { |
| 229 | int pc_regnum = gdbarch_pc_regnum (gdbarch); |
| 230 | CORE_ADDR pc = frame_unwind_register_unsigned (next_frame, pc_regnum); |
| 231 | pc = gdbarch_addr_bits_remove (gdbarch, pc); |
| 232 | return pc; |
| 233 | } |
| 234 | |
| 235 | /* See frame-unwind.h. */ |
| 236 | |
| 237 | CORE_ADDR |
| 238 | default_unwind_sp (struct gdbarch *gdbarch, struct frame_info *next_frame) |
| 239 | { |
| 240 | int sp_regnum = gdbarch_sp_regnum (gdbarch); |
| 241 | return frame_unwind_register_unsigned (next_frame, sp_regnum); |
| 242 | } |
| 243 | |
| 244 | /* Helper functions for value-based register unwinding. These return |
| 245 | a (possibly lazy) value of the appropriate type. */ |
| 246 | |
| 247 | /* Return a value which indicates that FRAME did not save REGNUM. */ |
| 248 | |
| 249 | struct value * |
| 250 | frame_unwind_got_optimized (struct frame_info *frame, int regnum) |
| 251 | { |
| 252 | struct gdbarch *gdbarch = frame_unwind_arch (frame); |
| 253 | struct type *type = register_type (gdbarch, regnum); |
| 254 | |
| 255 | return allocate_optimized_out_value (type); |
| 256 | } |
| 257 | |
| 258 | /* Return a value which indicates that FRAME copied REGNUM into |
| 259 | register NEW_REGNUM. */ |
| 260 | |
| 261 | struct value * |
| 262 | frame_unwind_got_register (struct frame_info *frame, |
| 263 | int regnum, int new_regnum) |
| 264 | { |
| 265 | return value_of_register_lazy (frame, new_regnum); |
| 266 | } |
| 267 | |
| 268 | /* Return a value which indicates that FRAME saved REGNUM in memory at |
| 269 | ADDR. */ |
| 270 | |
| 271 | struct value * |
| 272 | frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr) |
| 273 | { |
| 274 | struct gdbarch *gdbarch = frame_unwind_arch (frame); |
| 275 | struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr); |
| 276 | |
| 277 | set_value_stack (v, 1); |
| 278 | return v; |
| 279 | } |
| 280 | |
| 281 | /* Return a value which indicates that FRAME's saved version of |
| 282 | REGNUM has a known constant (computed) value of VAL. */ |
| 283 | |
| 284 | struct value * |
| 285 | frame_unwind_got_constant (struct frame_info *frame, int regnum, |
| 286 | ULONGEST val) |
| 287 | { |
| 288 | struct gdbarch *gdbarch = frame_unwind_arch (frame); |
| 289 | enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); |
| 290 | struct value *reg_val; |
| 291 | |
| 292 | reg_val = value_zero (register_type (gdbarch, regnum), not_lval); |
| 293 | store_unsigned_integer (value_contents_writeable (reg_val), |
| 294 | register_size (gdbarch, regnum), byte_order, val); |
| 295 | return reg_val; |
| 296 | } |
| 297 | |
| 298 | struct value * |
| 299 | frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf) |
| 300 | { |
| 301 | struct gdbarch *gdbarch = frame_unwind_arch (frame); |
| 302 | struct value *reg_val; |
| 303 | |
| 304 | reg_val = value_zero (register_type (gdbarch, regnum), not_lval); |
| 305 | memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum)); |
| 306 | return reg_val; |
| 307 | } |
| 308 | |
| 309 | /* Return a value which indicates that FRAME's saved version of REGNUM |
| 310 | has a known constant (computed) value of ADDR. Convert the |
| 311 | CORE_ADDR to a target address if necessary. */ |
| 312 | |
| 313 | struct value * |
| 314 | frame_unwind_got_address (struct frame_info *frame, int regnum, |
| 315 | CORE_ADDR addr) |
| 316 | { |
| 317 | struct gdbarch *gdbarch = frame_unwind_arch (frame); |
| 318 | struct value *reg_val; |
| 319 | |
| 320 | reg_val = value_zero (register_type (gdbarch, regnum), not_lval); |
| 321 | pack_long (value_contents_writeable (reg_val), |
| 322 | register_type (gdbarch, regnum), addr); |
| 323 | return reg_val; |
| 324 | } |
| 325 | |
| 326 | void _initialize_frame_unwind (); |
| 327 | void |
| 328 | _initialize_frame_unwind () |
| 329 | { |
| 330 | frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init); |
| 331 | } |