| 1 | /* Code dealing with dummy stack frames, for GDB, the GNU debugger. |
| 2 | |
| 3 | Copyright (C) 1986-2019 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 | |
| 21 | #include "defs.h" |
| 22 | #include "dummy-frame.h" |
| 23 | #include "regcache.h" |
| 24 | #include "frame.h" |
| 25 | #include "inferior.h" |
| 26 | #include "frame-unwind.h" |
| 27 | #include "command.h" |
| 28 | #include "gdbcmd.h" |
| 29 | #include "observable.h" |
| 30 | #include "gdbthread.h" |
| 31 | #include "infcall.h" |
| 32 | #include "gdbarch.h" |
| 33 | |
| 34 | struct dummy_frame_id |
| 35 | { |
| 36 | /* This frame's ID. Must match the value returned by |
| 37 | gdbarch_dummy_id. */ |
| 38 | struct frame_id id; |
| 39 | |
| 40 | /* The thread this dummy_frame relates to. */ |
| 41 | thread_info *thread; |
| 42 | }; |
| 43 | |
| 44 | /* Return whether dummy_frame_id *ID1 and *ID2 are equal. */ |
| 45 | |
| 46 | static int |
| 47 | dummy_frame_id_eq (struct dummy_frame_id *id1, |
| 48 | struct dummy_frame_id *id2) |
| 49 | { |
| 50 | return frame_id_eq (id1->id, id2->id) && id1->thread == id2->thread; |
| 51 | } |
| 52 | |
| 53 | /* List of dummy_frame destructors. */ |
| 54 | |
| 55 | struct dummy_frame_dtor_list |
| 56 | { |
| 57 | /* Next element in the list or NULL if this is the last element. */ |
| 58 | struct dummy_frame_dtor_list *next; |
| 59 | |
| 60 | /* If non-NULL, a destructor that is run when this dummy frame is freed. */ |
| 61 | dummy_frame_dtor_ftype *dtor; |
| 62 | |
| 63 | /* Arbitrary data that is passed to DTOR. */ |
| 64 | void *dtor_data; |
| 65 | }; |
| 66 | |
| 67 | /* Dummy frame. This saves the processor state just prior to setting |
| 68 | up the inferior function call. Older targets save the registers |
| 69 | on the target stack (but that really slows down function calls). */ |
| 70 | |
| 71 | struct dummy_frame |
| 72 | { |
| 73 | struct dummy_frame *next; |
| 74 | |
| 75 | /* An id represents a dummy frame. */ |
| 76 | struct dummy_frame_id id; |
| 77 | |
| 78 | /* The caller's state prior to the call. */ |
| 79 | struct infcall_suspend_state *caller_state; |
| 80 | |
| 81 | /* First element of destructors list or NULL if there are no |
| 82 | destructors registered for this dummy_frame. */ |
| 83 | struct dummy_frame_dtor_list *dtor_list; |
| 84 | }; |
| 85 | |
| 86 | static struct dummy_frame *dummy_frame_stack = NULL; |
| 87 | |
| 88 | /* Push the caller's state, along with the dummy frame info, onto the |
| 89 | dummy-frame stack. */ |
| 90 | |
| 91 | void |
| 92 | dummy_frame_push (struct infcall_suspend_state *caller_state, |
| 93 | const frame_id *dummy_id, thread_info *thread) |
| 94 | { |
| 95 | struct dummy_frame *dummy_frame; |
| 96 | |
| 97 | dummy_frame = XCNEW (struct dummy_frame); |
| 98 | dummy_frame->caller_state = caller_state; |
| 99 | dummy_frame->id.id = (*dummy_id); |
| 100 | dummy_frame->id.thread = thread; |
| 101 | dummy_frame->next = dummy_frame_stack; |
| 102 | dummy_frame_stack = dummy_frame; |
| 103 | } |
| 104 | |
| 105 | /* Remove *DUMMY_PTR from the dummy frame stack. */ |
| 106 | |
| 107 | static void |
| 108 | remove_dummy_frame (struct dummy_frame **dummy_ptr) |
| 109 | { |
| 110 | struct dummy_frame *dummy = *dummy_ptr; |
| 111 | |
| 112 | while (dummy->dtor_list != NULL) |
| 113 | { |
| 114 | struct dummy_frame_dtor_list *list = dummy->dtor_list; |
| 115 | |
| 116 | dummy->dtor_list = list->next; |
| 117 | list->dtor (list->dtor_data, 0); |
| 118 | xfree (list); |
| 119 | } |
| 120 | |
| 121 | *dummy_ptr = dummy->next; |
| 122 | discard_infcall_suspend_state (dummy->caller_state); |
| 123 | xfree (dummy); |
| 124 | } |
| 125 | |
| 126 | /* Delete any breakpoint B which is a momentary breakpoint for return from |
| 127 | inferior call matching DUMMY_VOIDP. */ |
| 128 | |
| 129 | static int |
| 130 | pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp) |
| 131 | { |
| 132 | struct dummy_frame *dummy = (struct dummy_frame *) dummy_voidp; |
| 133 | |
| 134 | if (b->thread == dummy->id.thread->global_num |
| 135 | && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id.id)) |
| 136 | { |
| 137 | while (b->related_breakpoint != b) |
| 138 | delete_breakpoint (b->related_breakpoint); |
| 139 | |
| 140 | delete_breakpoint (b); |
| 141 | |
| 142 | /* Stop the traversal. */ |
| 143 | return 1; |
| 144 | } |
| 145 | |
| 146 | /* Continue the traversal. */ |
| 147 | return 0; |
| 148 | } |
| 149 | |
| 150 | /* Pop *DUMMY_PTR, restoring program state to that before the |
| 151 | frame was created. */ |
| 152 | |
| 153 | static void |
| 154 | pop_dummy_frame (struct dummy_frame **dummy_ptr) |
| 155 | { |
| 156 | struct dummy_frame *dummy = *dummy_ptr; |
| 157 | |
| 158 | gdb_assert (dummy->id.thread == inferior_thread ()); |
| 159 | |
| 160 | while (dummy->dtor_list != NULL) |
| 161 | { |
| 162 | struct dummy_frame_dtor_list *list = dummy->dtor_list; |
| 163 | |
| 164 | dummy->dtor_list = list->next; |
| 165 | list->dtor (list->dtor_data, 1); |
| 166 | xfree (list); |
| 167 | } |
| 168 | |
| 169 | restore_infcall_suspend_state (dummy->caller_state); |
| 170 | |
| 171 | iterate_over_breakpoints (pop_dummy_frame_bpt, dummy); |
| 172 | |
| 173 | /* restore_infcall_control_state frees inf_state, |
| 174 | all that remains is to pop *dummy_ptr. */ |
| 175 | *dummy_ptr = dummy->next; |
| 176 | xfree (dummy); |
| 177 | |
| 178 | /* We've made right mess of GDB's local state, just discard |
| 179 | everything. */ |
| 180 | reinit_frame_cache (); |
| 181 | } |
| 182 | |
| 183 | /* Look up DUMMY_ID. |
| 184 | Return NULL if not found. */ |
| 185 | |
| 186 | static struct dummy_frame ** |
| 187 | lookup_dummy_frame (struct dummy_frame_id *dummy_id) |
| 188 | { |
| 189 | struct dummy_frame **dp; |
| 190 | |
| 191 | for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next) |
| 192 | { |
| 193 | if (dummy_frame_id_eq (&(*dp)->id, dummy_id)) |
| 194 | return dp; |
| 195 | } |
| 196 | |
| 197 | return NULL; |
| 198 | } |
| 199 | |
| 200 | /* Find the dummy frame by DUMMY_ID and THREAD, and pop it, restoring |
| 201 | program state to that before the frame was created. |
| 202 | On return reinit_frame_cache has been called. |
| 203 | If the frame isn't found, flag an internal error. */ |
| 204 | |
| 205 | void |
| 206 | dummy_frame_pop (frame_id dummy_id, thread_info *thread) |
| 207 | { |
| 208 | struct dummy_frame **dp; |
| 209 | struct dummy_frame_id id = { dummy_id, thread }; |
| 210 | |
| 211 | dp = lookup_dummy_frame (&id); |
| 212 | gdb_assert (dp != NULL); |
| 213 | |
| 214 | pop_dummy_frame (dp); |
| 215 | } |
| 216 | |
| 217 | /* Find the dummy frame by DUMMY_ID and PTID and drop it. Do nothing |
| 218 | if it is not found. Do not restore its state into inferior, just |
| 219 | free its memory. */ |
| 220 | |
| 221 | void |
| 222 | dummy_frame_discard (struct frame_id dummy_id, thread_info *thread) |
| 223 | { |
| 224 | struct dummy_frame **dp; |
| 225 | struct dummy_frame_id id = { dummy_id, thread }; |
| 226 | |
| 227 | dp = lookup_dummy_frame (&id); |
| 228 | if (dp) |
| 229 | remove_dummy_frame (dp); |
| 230 | } |
| 231 | |
| 232 | /* See dummy-frame.h. */ |
| 233 | |
| 234 | void |
| 235 | register_dummy_frame_dtor (frame_id dummy_id, thread_info *thread, |
| 236 | dummy_frame_dtor_ftype *dtor, void *dtor_data) |
| 237 | { |
| 238 | struct dummy_frame_id id = { dummy_id, thread }; |
| 239 | struct dummy_frame **dp, *d; |
| 240 | struct dummy_frame_dtor_list *list; |
| 241 | |
| 242 | dp = lookup_dummy_frame (&id); |
| 243 | gdb_assert (dp != NULL); |
| 244 | d = *dp; |
| 245 | list = XNEW (struct dummy_frame_dtor_list); |
| 246 | list->next = d->dtor_list; |
| 247 | d->dtor_list = list; |
| 248 | list->dtor = dtor; |
| 249 | list->dtor_data = dtor_data; |
| 250 | } |
| 251 | |
| 252 | /* See dummy-frame.h. */ |
| 253 | |
| 254 | int |
| 255 | find_dummy_frame_dtor (dummy_frame_dtor_ftype *dtor, void *dtor_data) |
| 256 | { |
| 257 | struct dummy_frame *d; |
| 258 | |
| 259 | for (d = dummy_frame_stack; d != NULL; d = d->next) |
| 260 | { |
| 261 | struct dummy_frame_dtor_list *list; |
| 262 | |
| 263 | for (list = d->dtor_list; list != NULL; list = list->next) |
| 264 | if (list->dtor == dtor && list->dtor_data == dtor_data) |
| 265 | return 1; |
| 266 | } |
| 267 | return 0; |
| 268 | } |
| 269 | |
| 270 | /* There may be stale dummy frames, perhaps left over from when an uncaught |
| 271 | longjmp took us out of a function that was called by the debugger. Clean |
| 272 | them up at least once whenever we start a new inferior. */ |
| 273 | |
| 274 | static void |
| 275 | cleanup_dummy_frames (struct target_ops *target, int from_tty) |
| 276 | { |
| 277 | while (dummy_frame_stack != NULL) |
| 278 | remove_dummy_frame (&dummy_frame_stack); |
| 279 | } |
| 280 | |
| 281 | /* Return the dummy frame cache, it contains both the ID, and a |
| 282 | pointer to the regcache. */ |
| 283 | struct dummy_frame_cache |
| 284 | { |
| 285 | struct frame_id this_id; |
| 286 | readonly_detached_regcache *prev_regcache; |
| 287 | }; |
| 288 | |
| 289 | static int |
| 290 | dummy_frame_sniffer (const struct frame_unwind *self, |
| 291 | struct frame_info *this_frame, |
| 292 | void **this_prologue_cache) |
| 293 | { |
| 294 | /* When unwinding a normal frame, the stack structure is determined |
| 295 | by analyzing the frame's function's code (be it using brute force |
| 296 | prologue analysis, or the dwarf2 CFI). In the case of a dummy |
| 297 | frame, that simply isn't possible. The PC is either the program |
| 298 | entry point, or some random address on the stack. Trying to use |
| 299 | that PC to apply standard frame ID unwind techniques is just |
| 300 | asking for trouble. */ |
| 301 | |
| 302 | /* Don't bother unless there is at least one dummy frame. */ |
| 303 | if (dummy_frame_stack != NULL) |
| 304 | { |
| 305 | struct dummy_frame *dummyframe; |
| 306 | /* Use an architecture specific method to extract this frame's |
| 307 | dummy ID, assuming it is a dummy frame. */ |
| 308 | struct frame_id this_id |
| 309 | = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame); |
| 310 | struct dummy_frame_id dummy_id = { this_id, inferior_thread () }; |
| 311 | |
| 312 | /* Use that ID to find the corresponding cache entry. */ |
| 313 | for (dummyframe = dummy_frame_stack; |
| 314 | dummyframe != NULL; |
| 315 | dummyframe = dummyframe->next) |
| 316 | { |
| 317 | if (dummy_frame_id_eq (&dummyframe->id, &dummy_id)) |
| 318 | { |
| 319 | struct dummy_frame_cache *cache; |
| 320 | |
| 321 | cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache); |
| 322 | cache->prev_regcache = get_infcall_suspend_state_regcache |
| 323 | (dummyframe->caller_state); |
| 324 | cache->this_id = this_id; |
| 325 | (*this_prologue_cache) = cache; |
| 326 | return 1; |
| 327 | } |
| 328 | } |
| 329 | } |
| 330 | return 0; |
| 331 | } |
| 332 | |
| 333 | /* Given a call-dummy dummy-frame, return the registers. Here the |
| 334 | register value is taken from the local copy of the register buffer. */ |
| 335 | |
| 336 | static struct value * |
| 337 | dummy_frame_prev_register (struct frame_info *this_frame, |
| 338 | void **this_prologue_cache, |
| 339 | int regnum) |
| 340 | { |
| 341 | struct dummy_frame_cache *cache |
| 342 | = (struct dummy_frame_cache *) *this_prologue_cache; |
| 343 | struct gdbarch *gdbarch = get_frame_arch (this_frame); |
| 344 | struct value *reg_val; |
| 345 | |
| 346 | /* The dummy-frame sniffer always fills in the cache. */ |
| 347 | gdb_assert (cache != NULL); |
| 348 | |
| 349 | /* Describe the register's location. Generic dummy frames always |
| 350 | have the register value in an ``expression''. */ |
| 351 | reg_val = value_zero (register_type (gdbarch, regnum), not_lval); |
| 352 | |
| 353 | /* Use the regcache_cooked_read() method so that it, on the fly, |
| 354 | constructs either a raw or pseudo register from the raw |
| 355 | register cache. */ |
| 356 | cache->prev_regcache->cooked_read (regnum, |
| 357 | value_contents_writeable (reg_val)); |
| 358 | return reg_val; |
| 359 | } |
| 360 | |
| 361 | /* Assuming that THIS_FRAME is a dummy, return its ID. That ID is |
| 362 | determined by examining the NEXT frame's unwound registers using |
| 363 | the method dummy_id(). As a side effect, THIS dummy frame's |
| 364 | dummy cache is located and saved in THIS_PROLOGUE_CACHE. */ |
| 365 | |
| 366 | static void |
| 367 | dummy_frame_this_id (struct frame_info *this_frame, |
| 368 | void **this_prologue_cache, |
| 369 | struct frame_id *this_id) |
| 370 | { |
| 371 | /* The dummy-frame sniffer always fills in the cache. */ |
| 372 | struct dummy_frame_cache *cache |
| 373 | = (struct dummy_frame_cache *) *this_prologue_cache; |
| 374 | |
| 375 | gdb_assert (cache != NULL); |
| 376 | (*this_id) = cache->this_id; |
| 377 | } |
| 378 | |
| 379 | const struct frame_unwind dummy_frame_unwind = |
| 380 | { |
| 381 | DUMMY_FRAME, |
| 382 | default_frame_unwind_stop_reason, |
| 383 | dummy_frame_this_id, |
| 384 | dummy_frame_prev_register, |
| 385 | NULL, |
| 386 | dummy_frame_sniffer, |
| 387 | }; |
| 388 | |
| 389 | /* See dummy-frame.h. */ |
| 390 | |
| 391 | struct frame_id |
| 392 | default_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame) |
| 393 | { |
| 394 | CORE_ADDR sp, pc; |
| 395 | |
| 396 | sp = get_frame_sp (this_frame); |
| 397 | pc = get_frame_pc (this_frame); |
| 398 | return frame_id_build (sp, pc); |
| 399 | } |
| 400 | |
| 401 | static void |
| 402 | fprint_dummy_frames (struct ui_file *file) |
| 403 | { |
| 404 | struct dummy_frame *s; |
| 405 | |
| 406 | for (s = dummy_frame_stack; s != NULL; s = s->next) |
| 407 | { |
| 408 | gdb_print_host_address (s, file); |
| 409 | fprintf_unfiltered (file, ":"); |
| 410 | fprintf_unfiltered (file, " id="); |
| 411 | fprint_frame_id (file, s->id.id); |
| 412 | fprintf_unfiltered (file, ", ptid=%s", |
| 413 | target_pid_to_str (s->id.thread->ptid).c_str ()); |
| 414 | fprintf_unfiltered (file, "\n"); |
| 415 | } |
| 416 | } |
| 417 | |
| 418 | static void |
| 419 | maintenance_print_dummy_frames (const char *args, int from_tty) |
| 420 | { |
| 421 | if (args == NULL) |
| 422 | fprint_dummy_frames (gdb_stdout); |
| 423 | else |
| 424 | { |
| 425 | stdio_file file; |
| 426 | |
| 427 | if (!file.open (args, "w")) |
| 428 | perror_with_name (_("maintenance print dummy-frames")); |
| 429 | fprint_dummy_frames (&file); |
| 430 | } |
| 431 | } |
| 432 | |
| 433 | void |
| 434 | _initialize_dummy_frame (void) |
| 435 | { |
| 436 | add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames, |
| 437 | _("Print the contents of the internal dummy-frame stack."), |
| 438 | &maintenanceprintlist); |
| 439 | |
| 440 | gdb::observers::inferior_created.attach (cleanup_dummy_frames); |
| 441 | } |