1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger. 2 3 Copyright (C) 1986-2004, 2007-2012 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 33 /* Dummy frame. This saves the processor state just prior to setting 34 up the inferior function call. Older targets save the registers 35 on the target stack (but that really slows down function calls). */ 36 37 struct dummy_frame 38 { 39 struct dummy_frame *next; 40 /* This frame's ID. Must match the value returned by 41 gdbarch_dummy_id. */ 42 struct frame_id id; 43 /* The caller's state prior to the call. */ 44 struct infcall_suspend_state *caller_state; 45 }; 46 47 static struct dummy_frame *dummy_frame_stack = NULL; 48 49 /* Function: deprecated_pc_in_call_dummy (pc) 50 51 Return non-zero if the PC falls in a dummy frame created by gdb for 52 an inferior call. The code below which allows gdbarch_decr_pc_after_break 53 is for infrun.c, which may give the function a PC without that 54 subtracted out. 55 56 FIXME: cagney/2002-11-23: This is silly. Surely "infrun.c" can 57 figure out what the real PC (as in the resume address) is BEFORE 58 calling this function. 59 60 NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of 61 infrun.c:adjust_pc_after_break (thanks), this function is now 62 always called with a correctly adjusted PC! 63 64 NOTE: cagney/2004-08-02: Code should not need to call this. */ 65 66 int 67 deprecated_pc_in_call_dummy (struct gdbarch *gdbarch, CORE_ADDR pc) 68 { 69 struct dummy_frame *dummyframe; 70 71 for (dummyframe = dummy_frame_stack; 72 dummyframe != NULL; 73 dummyframe = dummyframe->next) 74 { 75 if ((pc >= dummyframe->id.code_addr) 76 && (pc <= dummyframe->id.code_addr 77 + gdbarch_decr_pc_after_break (gdbarch))) 78 return 1; 79 } 80 return 0; 81 } 82 83 /* Push the caller's state, along with the dummy frame info, onto the 84 dummy-frame stack. */ 85 86 void 87 dummy_frame_push (struct infcall_suspend_state *caller_state, 88 const struct frame_id *dummy_id) 89 { 90 struct dummy_frame *dummy_frame; 91 92 dummy_frame = XZALLOC (struct dummy_frame); 93 dummy_frame->caller_state = caller_state; 94 dummy_frame->id = (*dummy_id); 95 dummy_frame->next = dummy_frame_stack; 96 dummy_frame_stack = dummy_frame; 97 } 98 99 /* Remove *DUMMY_PTR from the dummy frame stack. */ 100 101 static void 102 remove_dummy_frame (struct dummy_frame **dummy_ptr) 103 { 104 struct dummy_frame *dummy = *dummy_ptr; 105 106 *dummy_ptr = dummy->next; 107 discard_infcall_suspend_state (dummy->caller_state); 108 xfree (dummy); 109 } 110 111 /* Pop *DUMMY_PTR, restoring program state to that before the 112 frame was created. */ 113 114 static void 115 pop_dummy_frame (struct dummy_frame **dummy_ptr) 116 { 117 struct dummy_frame *dummy; 118 119 restore_infcall_suspend_state ((*dummy_ptr)->caller_state); 120 121 /* restore_infcall_control_state frees inf_state, 122 all that remains is to pop *dummy_ptr. */ 123 dummy = *dummy_ptr; 124 *dummy_ptr = dummy->next; 125 xfree (dummy); 126 127 /* We've made right mess of GDB's local state, just discard 128 everything. */ 129 reinit_frame_cache (); 130 } 131 132 /* Look up DUMMY_ID. 133 Return NULL if not found. */ 134 135 static struct dummy_frame ** 136 lookup_dummy_frame (struct frame_id dummy_id) 137 { 138 struct dummy_frame **dp; 139 140 for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next) 141 { 142 if (frame_id_eq ((*dp)->id, dummy_id)) 143 return dp; 144 } 145 146 return NULL; 147 } 148 149 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the 150 frame was created. 151 On return reinit_frame_cache has been called. 152 If the frame isn't found, flag an internal error. 153 154 NOTE: This can only pop the one frame, even if it is in the middle of the 155 stack, because the other frames may be for different threads, and there's 156 currently no way to tell which stack frame is for which thread. */ 157 158 void 159 dummy_frame_pop (struct frame_id dummy_id) 160 { 161 struct dummy_frame **dp; 162 163 dp = lookup_dummy_frame (dummy_id); 164 gdb_assert (dp != NULL); 165 166 pop_dummy_frame (dp); 167 } 168 169 /* There may be stale dummy frames, perhaps left over from when a longjump took 170 us out of a function that was called by the debugger. Clean them up at 171 least once whenever we start a new inferior. */ 172 173 static void 174 cleanup_dummy_frames (struct target_ops *target, int from_tty) 175 { 176 while (dummy_frame_stack != NULL) 177 remove_dummy_frame (&dummy_frame_stack); 178 } 179 180 /* Return the dummy frame cache, it contains both the ID, and a 181 pointer to the regcache. */ 182 struct dummy_frame_cache 183 { 184 struct frame_id this_id; 185 struct regcache *prev_regcache; 186 }; 187 188 static int 189 dummy_frame_sniffer (const struct frame_unwind *self, 190 struct frame_info *this_frame, 191 void **this_prologue_cache) 192 { 193 struct dummy_frame *dummyframe; 194 struct frame_id this_id; 195 196 /* When unwinding a normal frame, the stack structure is determined 197 by analyzing the frame's function's code (be it using brute force 198 prologue analysis, or the dwarf2 CFI). In the case of a dummy 199 frame, that simply isn't possible. The PC is either the program 200 entry point, or some random address on the stack. Trying to use 201 that PC to apply standard frame ID unwind techniques is just 202 asking for trouble. */ 203 204 /* Don't bother unless there is at least one dummy frame. */ 205 if (dummy_frame_stack != NULL) 206 { 207 /* Use an architecture specific method to extract this frame's 208 dummy ID, assuming it is a dummy frame. */ 209 this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame); 210 211 /* Use that ID to find the corresponding cache entry. */ 212 for (dummyframe = dummy_frame_stack; 213 dummyframe != NULL; 214 dummyframe = dummyframe->next) 215 { 216 if (frame_id_eq (dummyframe->id, this_id)) 217 { 218 struct dummy_frame_cache *cache; 219 220 cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache); 221 cache->prev_regcache = get_infcall_suspend_state_regcache 222 (dummyframe->caller_state); 223 cache->this_id = this_id; 224 (*this_prologue_cache) = cache; 225 return 1; 226 } 227 } 228 } 229 return 0; 230 } 231 232 /* Given a call-dummy dummy-frame, return the registers. Here the 233 register value is taken from the local copy of the register buffer. */ 234 235 static struct value * 236 dummy_frame_prev_register (struct frame_info *this_frame, 237 void **this_prologue_cache, 238 int regnum) 239 { 240 struct dummy_frame_cache *cache = (*this_prologue_cache); 241 struct gdbarch *gdbarch = get_frame_arch (this_frame); 242 struct value *reg_val; 243 244 /* The dummy-frame sniffer always fills in the cache. */ 245 gdb_assert (cache != NULL); 246 247 /* Describe the register's location. Generic dummy frames always 248 have the register value in an ``expression''. */ 249 reg_val = value_zero (register_type (gdbarch, regnum), not_lval); 250 251 /* Use the regcache_cooked_read() method so that it, on the fly, 252 constructs either a raw or pseudo register from the raw 253 register cache. */ 254 regcache_cooked_read (cache->prev_regcache, regnum, 255 value_contents_writeable (reg_val)); 256 return reg_val; 257 } 258 259 /* Assuming that THIS_FRAME is a dummy, return its ID. That ID is 260 determined by examining the NEXT frame's unwound registers using 261 the method dummy_id(). As a side effect, THIS dummy frame's 262 dummy cache is located and saved in THIS_PROLOGUE_CACHE. */ 263 264 static void 265 dummy_frame_this_id (struct frame_info *this_frame, 266 void **this_prologue_cache, 267 struct frame_id *this_id) 268 { 269 /* The dummy-frame sniffer always fills in the cache. */ 270 struct dummy_frame_cache *cache = (*this_prologue_cache); 271 272 gdb_assert (cache != NULL); 273 (*this_id) = cache->this_id; 274 } 275 276 const struct frame_unwind dummy_frame_unwind = 277 { 278 DUMMY_FRAME, 279 default_frame_unwind_stop_reason, 280 dummy_frame_this_id, 281 dummy_frame_prev_register, 282 NULL, 283 dummy_frame_sniffer, 284 }; 285 286 static void 287 fprint_dummy_frames (struct ui_file *file) 288 { 289 struct dummy_frame *s; 290 291 for (s = dummy_frame_stack; s != NULL; s = s->next) 292 { 293 gdb_print_host_address (s, file); 294 fprintf_unfiltered (file, ":"); 295 fprintf_unfiltered (file, " id="); 296 fprint_frame_id (file, s->id); 297 fprintf_unfiltered (file, "\n"); 298 } 299 } 300 301 static void 302 maintenance_print_dummy_frames (char *args, int from_tty) 303 { 304 if (args == NULL) 305 fprint_dummy_frames (gdb_stdout); 306 else 307 { 308 struct cleanup *cleanups; 309 struct ui_file *file = gdb_fopen (args, "w"); 310 311 if (file == NULL) 312 perror_with_name (_("maintenance print dummy-frames")); 313 cleanups = make_cleanup_ui_file_delete (file); 314 fprint_dummy_frames (file); 315 do_cleanups (cleanups); 316 } 317 } 318 319 extern void _initialize_dummy_frame (void); 320 321 void 322 _initialize_dummy_frame (void) 323 { 324 add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames, 325 _("Print the contents of the internal dummy-frame stack."), 326 &maintenanceprintlist); 327 328 observer_attach_inferior_created (cleanup_dummy_frames); 329 } 330