1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger. 2 3 Copyright (C) 1986-2023 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 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 bool 130 pop_dummy_frame_bpt (struct breakpoint *b, struct dummy_frame *dummy) 131 { 132 if (b->thread == dummy->id.thread->global_num 133 && b->disposition == disp_del && b->frame_id == dummy->id.id) 134 { 135 while (b->related_breakpoint != b) 136 delete_breakpoint (b->related_breakpoint); 137 138 delete_breakpoint (b); 139 140 /* Stop the traversal. */ 141 return true; 142 } 143 144 /* Continue the traversal. */ 145 return false; 146 } 147 148 /* Pop *DUMMY_PTR, restoring program state to that before the 149 frame was created. */ 150 151 static void 152 pop_dummy_frame (struct dummy_frame **dummy_ptr) 153 { 154 struct dummy_frame *dummy = *dummy_ptr; 155 156 gdb_assert (dummy->id.thread == inferior_thread ()); 157 158 while (dummy->dtor_list != NULL) 159 { 160 struct dummy_frame_dtor_list *list = dummy->dtor_list; 161 162 dummy->dtor_list = list->next; 163 list->dtor (list->dtor_data, 1); 164 xfree (list); 165 } 166 167 restore_infcall_suspend_state (dummy->caller_state); 168 169 for (breakpoint *bp : all_breakpoints_safe ()) 170 if (pop_dummy_frame_bpt (bp, dummy)) 171 break; 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 (inferior *inf) 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 frame_info_ptr 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 (frame_info_ptr 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 357 (regnum, value_contents_writeable (reg_val).data ()); 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 (frame_info_ptr 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", 382 DUMMY_FRAME, 383 default_frame_unwind_stop_reason, 384 dummy_frame_this_id, 385 dummy_frame_prev_register, 386 NULL, 387 dummy_frame_sniffer, 388 }; 389 390 /* See dummy-frame.h. */ 391 392 struct frame_id 393 default_dummy_id (struct gdbarch *gdbarch, frame_info_ptr this_frame) 394 { 395 CORE_ADDR sp, pc; 396 397 sp = get_frame_sp (this_frame); 398 pc = get_frame_pc (this_frame); 399 return frame_id_build (sp, pc); 400 } 401 402 static void 403 fprint_dummy_frames (struct ui_file *file) 404 { 405 struct dummy_frame *s; 406 407 for (s = dummy_frame_stack; s != NULL; s = s->next) 408 gdb_printf (file, "%s: id=%s, ptid=%s\n", 409 host_address_to_string (s), 410 s->id.id.to_string ().c_str (), 411 s->id.thread->ptid.to_string ().c_str ()); 412 } 413 414 static void 415 maintenance_print_dummy_frames (const char *args, int from_tty) 416 { 417 if (args == NULL) 418 fprint_dummy_frames (gdb_stdout); 419 else 420 { 421 stdio_file file; 422 423 if (!file.open (args, "w")) 424 perror_with_name (_("maintenance print dummy-frames")); 425 fprint_dummy_frames (&file); 426 } 427 } 428 429 void _initialize_dummy_frame (); 430 void 431 _initialize_dummy_frame () 432 { 433 add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames, 434 _("Print the contents of the internal dummy-frame stack."), 435 &maintenanceprintlist); 436 437 gdb::observers::inferior_created.attach (cleanup_dummy_frames, "dummy-frame"); 438 } 439