1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger. 2 3 Copyright (C) 1986-2013 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 "gdb_assert.h" 27 #include "frame-unwind.h" 28 #include "command.h" 29 #include "gdbcmd.h" 30 #include "gdb_string.h" 31 #include "observer.h" 32 #include "gdbthread.h" 33 34 /* Dummy frame. This saves the processor state just prior to setting 35 up the inferior function call. Older targets save the registers 36 on the target stack (but that really slows down function calls). */ 37 38 struct dummy_frame 39 { 40 struct dummy_frame *next; 41 /* This frame's ID. Must match the value returned by 42 gdbarch_dummy_id. */ 43 struct frame_id id; 44 /* The caller's state prior to the call. */ 45 struct infcall_suspend_state *caller_state; 46 }; 47 48 static struct dummy_frame *dummy_frame_stack = NULL; 49 50 /* Push the caller's state, along with the dummy frame info, onto the 51 dummy-frame stack. */ 52 53 void 54 dummy_frame_push (struct infcall_suspend_state *caller_state, 55 const struct frame_id *dummy_id) 56 { 57 struct dummy_frame *dummy_frame; 58 59 dummy_frame = XZALLOC (struct dummy_frame); 60 dummy_frame->caller_state = caller_state; 61 dummy_frame->id = (*dummy_id); 62 dummy_frame->next = dummy_frame_stack; 63 dummy_frame_stack = dummy_frame; 64 } 65 66 /* Remove *DUMMY_PTR from the dummy frame stack. */ 67 68 static void 69 remove_dummy_frame (struct dummy_frame **dummy_ptr) 70 { 71 struct dummy_frame *dummy = *dummy_ptr; 72 73 *dummy_ptr = dummy->next; 74 discard_infcall_suspend_state (dummy->caller_state); 75 xfree (dummy); 76 } 77 78 /* Delete any breakpoint B which is a momentary breakpoint for return from 79 inferior call matching DUMMY_VOIDP. */ 80 81 static int 82 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp) 83 { 84 struct dummy_frame *dummy = dummy_voidp; 85 86 if (b->thread == pid_to_thread_id (inferior_ptid) 87 && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id)) 88 { 89 while (b->related_breakpoint != b) 90 delete_breakpoint (b->related_breakpoint); 91 92 delete_breakpoint (b); 93 94 /* Stop the traversal. */ 95 return 1; 96 } 97 98 /* Continue the traversal. */ 99 return 0; 100 } 101 102 /* Pop *DUMMY_PTR, restoring program state to that before the 103 frame was created. */ 104 105 static void 106 pop_dummy_frame (struct dummy_frame **dummy_ptr) 107 { 108 struct dummy_frame *dummy = *dummy_ptr; 109 110 restore_infcall_suspend_state (dummy->caller_state); 111 112 iterate_over_breakpoints (pop_dummy_frame_bpt, dummy); 113 114 /* restore_infcall_control_state frees inf_state, 115 all that remains is to pop *dummy_ptr. */ 116 *dummy_ptr = dummy->next; 117 xfree (dummy); 118 119 /* We've made right mess of GDB's local state, just discard 120 everything. */ 121 reinit_frame_cache (); 122 } 123 124 /* Look up DUMMY_ID. 125 Return NULL if not found. */ 126 127 static struct dummy_frame ** 128 lookup_dummy_frame (struct frame_id dummy_id) 129 { 130 struct dummy_frame **dp; 131 132 for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next) 133 { 134 if (frame_id_eq ((*dp)->id, dummy_id)) 135 return dp; 136 } 137 138 return NULL; 139 } 140 141 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the 142 frame was created. 143 On return reinit_frame_cache has been called. 144 If the frame isn't found, flag an internal error. 145 146 NOTE: This can only pop the one frame, even if it is in the middle of the 147 stack, because the other frames may be for different threads, and there's 148 currently no way to tell which stack frame is for which thread. */ 149 150 void 151 dummy_frame_pop (struct frame_id dummy_id) 152 { 153 struct dummy_frame **dp; 154 155 dp = lookup_dummy_frame (dummy_id); 156 gdb_assert (dp != NULL); 157 158 pop_dummy_frame (dp); 159 } 160 161 /* Drop dummy frame DUMMY_ID. Do nothing if it is not found. Do not restore 162 its state into inferior, just free its memory. */ 163 164 void 165 dummy_frame_discard (struct frame_id dummy_id) 166 { 167 struct dummy_frame **dp; 168 169 dp = lookup_dummy_frame (dummy_id); 170 if (dp) 171 remove_dummy_frame (dp); 172 } 173 174 /* There may be stale dummy frames, perhaps left over from when an uncaught 175 longjmp took us out of a function that was called by the debugger. Clean 176 them up at least once whenever we start a new inferior. */ 177 178 static void 179 cleanup_dummy_frames (struct target_ops *target, int from_tty) 180 { 181 while (dummy_frame_stack != NULL) 182 remove_dummy_frame (&dummy_frame_stack); 183 } 184 185 /* Return the dummy frame cache, it contains both the ID, and a 186 pointer to the regcache. */ 187 struct dummy_frame_cache 188 { 189 struct frame_id this_id; 190 struct regcache *prev_regcache; 191 }; 192 193 static int 194 dummy_frame_sniffer (const struct frame_unwind *self, 195 struct frame_info *this_frame, 196 void **this_prologue_cache) 197 { 198 struct dummy_frame *dummyframe; 199 struct frame_id this_id; 200 201 /* When unwinding a normal frame, the stack structure is determined 202 by analyzing the frame's function's code (be it using brute force 203 prologue analysis, or the dwarf2 CFI). In the case of a dummy 204 frame, that simply isn't possible. The PC is either the program 205 entry point, or some random address on the stack. Trying to use 206 that PC to apply standard frame ID unwind techniques is just 207 asking for trouble. */ 208 209 /* Don't bother unless there is at least one dummy frame. */ 210 if (dummy_frame_stack != NULL) 211 { 212 /* Use an architecture specific method to extract this frame's 213 dummy ID, assuming it is a dummy frame. */ 214 this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame); 215 216 /* Use that ID to find the corresponding cache entry. */ 217 for (dummyframe = dummy_frame_stack; 218 dummyframe != NULL; 219 dummyframe = dummyframe->next) 220 { 221 if (frame_id_eq (dummyframe->id, this_id)) 222 { 223 struct dummy_frame_cache *cache; 224 225 cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache); 226 cache->prev_regcache = get_infcall_suspend_state_regcache 227 (dummyframe->caller_state); 228 cache->this_id = this_id; 229 (*this_prologue_cache) = cache; 230 return 1; 231 } 232 } 233 } 234 return 0; 235 } 236 237 /* Given a call-dummy dummy-frame, return the registers. Here the 238 register value is taken from the local copy of the register buffer. */ 239 240 static struct value * 241 dummy_frame_prev_register (struct frame_info *this_frame, 242 void **this_prologue_cache, 243 int regnum) 244 { 245 struct dummy_frame_cache *cache = (*this_prologue_cache); 246 struct gdbarch *gdbarch = get_frame_arch (this_frame); 247 struct value *reg_val; 248 249 /* The dummy-frame sniffer always fills in the cache. */ 250 gdb_assert (cache != NULL); 251 252 /* Describe the register's location. Generic dummy frames always 253 have the register value in an ``expression''. */ 254 reg_val = value_zero (register_type (gdbarch, regnum), not_lval); 255 256 /* Use the regcache_cooked_read() method so that it, on the fly, 257 constructs either a raw or pseudo register from the raw 258 register cache. */ 259 regcache_cooked_read (cache->prev_regcache, regnum, 260 value_contents_writeable (reg_val)); 261 return reg_val; 262 } 263 264 /* Assuming that THIS_FRAME is a dummy, return its ID. That ID is 265 determined by examining the NEXT frame's unwound registers using 266 the method dummy_id(). As a side effect, THIS dummy frame's 267 dummy cache is located and saved in THIS_PROLOGUE_CACHE. */ 268 269 static void 270 dummy_frame_this_id (struct frame_info *this_frame, 271 void **this_prologue_cache, 272 struct frame_id *this_id) 273 { 274 /* The dummy-frame sniffer always fills in the cache. */ 275 struct dummy_frame_cache *cache = (*this_prologue_cache); 276 277 gdb_assert (cache != NULL); 278 (*this_id) = cache->this_id; 279 } 280 281 const struct frame_unwind dummy_frame_unwind = 282 { 283 DUMMY_FRAME, 284 default_frame_unwind_stop_reason, 285 dummy_frame_this_id, 286 dummy_frame_prev_register, 287 NULL, 288 dummy_frame_sniffer, 289 }; 290 291 static void 292 fprint_dummy_frames (struct ui_file *file) 293 { 294 struct dummy_frame *s; 295 296 for (s = dummy_frame_stack; s != NULL; s = s->next) 297 { 298 gdb_print_host_address (s, file); 299 fprintf_unfiltered (file, ":"); 300 fprintf_unfiltered (file, " id="); 301 fprint_frame_id (file, s->id); 302 fprintf_unfiltered (file, "\n"); 303 } 304 } 305 306 static void 307 maintenance_print_dummy_frames (char *args, int from_tty) 308 { 309 if (args == NULL) 310 fprint_dummy_frames (gdb_stdout); 311 else 312 { 313 struct cleanup *cleanups; 314 struct ui_file *file = gdb_fopen (args, "w"); 315 316 if (file == NULL) 317 perror_with_name (_("maintenance print dummy-frames")); 318 cleanups = make_cleanup_ui_file_delete (file); 319 fprint_dummy_frames (file); 320 do_cleanups (cleanups); 321 } 322 } 323 324 extern void _initialize_dummy_frame (void); 325 326 void 327 _initialize_dummy_frame (void) 328 { 329 add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames, 330 _("Print the contents of the internal dummy-frame stack."), 331 &maintenanceprintlist); 332 333 observer_attach_inferior_created (cleanup_dummy_frames); 334 } 335