1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger. 2 3 Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 4 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2007, 2008, 2009, 5 2010 Free Software Foundation, Inc. 6 7 This file is part of GDB. 8 9 This program is free software; you can redistribute it and/or modify 10 it under the terms of the GNU General Public License as published by 11 the Free Software Foundation; either version 3 of the License, or 12 (at your option) any later version. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 21 22 23 #include "defs.h" 24 #include "dummy-frame.h" 25 #include "regcache.h" 26 #include "frame.h" 27 #include "inferior.h" 28 #include "gdb_assert.h" 29 #include "frame-unwind.h" 30 #include "command.h" 31 #include "gdbcmd.h" 32 #include "gdb_string.h" 33 #include "observer.h" 34 35 /* Dummy frame. This saves the processor state just prior to setting 36 up the inferior function call. Older targets save the registers 37 on the target stack (but that really slows down function calls). */ 38 39 struct dummy_frame 40 { 41 struct dummy_frame *next; 42 /* This frame's ID. Must match the value returned by 43 gdbarch_dummy_id. */ 44 struct frame_id id; 45 /* The caller's state prior to the call. */ 46 struct inferior_thread_state *caller_state; 47 }; 48 49 static struct dummy_frame *dummy_frame_stack = NULL; 50 51 /* Function: deprecated_pc_in_call_dummy (pc) 52 53 Return non-zero if the PC falls in a dummy frame created by gdb for 54 an inferior call. The code below which allows gdbarch_decr_pc_after_break 55 is for infrun.c, which may give the function a PC without that 56 subtracted out. 57 58 FIXME: cagney/2002-11-23: This is silly. Surely "infrun.c" can 59 figure out what the real PC (as in the resume address) is BEFORE 60 calling this function. 61 62 NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of 63 infrun.c:adjust_pc_after_break (thanks), this function is now 64 always called with a correctly adjusted PC! 65 66 NOTE: cagney/2004-08-02: Code should not need to call this. */ 67 68 int 69 deprecated_pc_in_call_dummy (struct gdbarch *gdbarch, CORE_ADDR pc) 70 { 71 struct dummy_frame *dummyframe; 72 73 for (dummyframe = dummy_frame_stack; 74 dummyframe != NULL; 75 dummyframe = dummyframe->next) 76 { 77 if ((pc >= dummyframe->id.code_addr) 78 && (pc <= dummyframe->id.code_addr 79 + gdbarch_decr_pc_after_break (gdbarch))) 80 return 1; 81 } 82 return 0; 83 } 84 85 /* Push the caller's state, along with the dummy frame info, onto the 86 dummy-frame stack. */ 87 88 void 89 dummy_frame_push (struct inferior_thread_state *caller_state, 90 const struct frame_id *dummy_id) 91 { 92 struct dummy_frame *dummy_frame; 93 94 dummy_frame = XZALLOC (struct dummy_frame); 95 dummy_frame->caller_state = caller_state; 96 dummy_frame->id = (*dummy_id); 97 dummy_frame->next = dummy_frame_stack; 98 dummy_frame_stack = dummy_frame; 99 } 100 101 /* Remove *DUMMY_PTR from the dummy frame stack. */ 102 103 static void 104 remove_dummy_frame (struct dummy_frame **dummy_ptr) 105 { 106 struct dummy_frame *dummy = *dummy_ptr; 107 108 *dummy_ptr = dummy->next; 109 discard_inferior_thread_state (dummy->caller_state); 110 xfree (dummy); 111 } 112 113 /* Pop *DUMMY_PTR, restoring program state to that before the 114 frame was created. */ 115 116 static void 117 pop_dummy_frame (struct dummy_frame **dummy_ptr) 118 { 119 struct dummy_frame *dummy; 120 121 restore_inferior_thread_state ((*dummy_ptr)->caller_state); 122 123 /* restore_inferior_status frees inf_state, 124 all that remains is to pop *dummy_ptr */ 125 dummy = *dummy_ptr; 126 *dummy_ptr = dummy->next; 127 xfree (dummy); 128 129 /* We've made right mess of GDB's local state, just discard 130 everything. */ 131 reinit_frame_cache (); 132 } 133 134 /* Look up DUMMY_ID. 135 Return NULL if not found. */ 136 137 static struct dummy_frame ** 138 lookup_dummy_frame (struct frame_id dummy_id) 139 { 140 struct dummy_frame **dp; 141 142 for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next) 143 { 144 if (frame_id_eq ((*dp)->id, dummy_id)) 145 return dp; 146 } 147 148 return NULL; 149 } 150 151 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the 152 frame was created. 153 On return reinit_frame_cache has been called. 154 If the frame isn't found, flag an internal error. 155 156 NOTE: This can only pop the one frame, even if it is in the middle of the 157 stack, because the other frames may be for different threads, and there's 158 currently no way to tell which stack frame is for which thread. */ 159 160 void 161 dummy_frame_pop (struct frame_id dummy_id) 162 { 163 struct dummy_frame **dp; 164 165 dp = lookup_dummy_frame (dummy_id); 166 gdb_assert (dp != NULL); 167 168 pop_dummy_frame (dp); 169 } 170 171 /* There may be stale dummy frames, perhaps left over from when a longjump took 172 us out of a function that was called by the debugger. Clean them up at 173 least once whenever we start a new inferior. */ 174 175 static void 176 cleanup_dummy_frames (struct target_ops *target, int from_tty) 177 { 178 while (dummy_frame_stack != NULL) 179 remove_dummy_frame (&dummy_frame_stack); 180 } 181 182 /* Return the dummy frame cache, it contains both the ID, and a 183 pointer to the regcache. */ 184 struct dummy_frame_cache 185 { 186 struct frame_id this_id; 187 struct regcache *prev_regcache; 188 }; 189 190 static int 191 dummy_frame_sniffer (const struct frame_unwind *self, 192 struct frame_info *this_frame, 193 void **this_prologue_cache) 194 { 195 struct dummy_frame *dummyframe; 196 struct frame_id this_id; 197 198 /* When unwinding a normal frame, the stack structure is determined 199 by analyzing the frame's function's code (be it using brute force 200 prologue analysis, or the dwarf2 CFI). In the case of a dummy 201 frame, that simply isn't possible. The PC is either the program 202 entry point, or some random address on the stack. Trying to use 203 that PC to apply standard frame ID unwind techniques is just 204 asking for trouble. */ 205 206 /* Don't bother unless there is at least one dummy frame. */ 207 if (dummy_frame_stack != NULL) 208 { 209 /* Use an architecture specific method to extract this frame's 210 dummy ID, assuming it is a dummy frame. */ 211 this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame); 212 213 /* Use that ID to find the corresponding cache entry. */ 214 for (dummyframe = dummy_frame_stack; 215 dummyframe != NULL; 216 dummyframe = dummyframe->next) 217 { 218 if (frame_id_eq (dummyframe->id, this_id)) 219 { 220 struct dummy_frame_cache *cache; 221 222 cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache); 223 cache->prev_regcache = get_inferior_thread_state_regcache (dummyframe->caller_state); 224 cache->this_id = this_id; 225 (*this_prologue_cache) = cache; 226 return 1; 227 } 228 } 229 } 230 return 0; 231 } 232 233 /* Given a call-dummy dummy-frame, return the registers. Here the 234 register value is taken from the local copy of the register buffer. */ 235 236 static struct value * 237 dummy_frame_prev_register (struct frame_info *this_frame, 238 void **this_prologue_cache, 239 int regnum) 240 { 241 struct dummy_frame_cache *cache = (*this_prologue_cache); 242 struct gdbarch *gdbarch = get_frame_arch (this_frame); 243 struct value *reg_val; 244 245 /* The dummy-frame sniffer always fills in the cache. */ 246 gdb_assert (cache != NULL); 247 248 /* Describe the register's location. Generic dummy frames always 249 have the register value in an ``expression''. */ 250 reg_val = value_zero (register_type (gdbarch, regnum), not_lval); 251 252 /* Use the regcache_cooked_read() method so that it, on the fly, 253 constructs either a raw or pseudo register from the raw 254 register cache. */ 255 regcache_cooked_read (cache->prev_regcache, regnum, 256 value_contents_writeable (reg_val)); 257 return reg_val; 258 } 259 260 /* Assuming that THIS_FRAME is a dummy, return its ID. That ID is 261 determined by examining the NEXT frame's unwound registers using 262 the method dummy_id(). As a side effect, THIS dummy frame's 263 dummy cache is located and and saved in THIS_PROLOGUE_CACHE. */ 264 265 static void 266 dummy_frame_this_id (struct frame_info *this_frame, 267 void **this_prologue_cache, 268 struct frame_id *this_id) 269 { 270 /* The dummy-frame sniffer always fills in the cache. */ 271 struct dummy_frame_cache *cache = (*this_prologue_cache); 272 273 gdb_assert (cache != NULL); 274 (*this_id) = cache->this_id; 275 } 276 277 static const struct frame_unwind dummy_frame_unwinder = 278 { 279 DUMMY_FRAME, 280 dummy_frame_this_id, 281 dummy_frame_prev_register, 282 NULL, 283 dummy_frame_sniffer, 284 }; 285 286 const struct frame_unwind *const dummy_frame_unwind = { 287 &dummy_frame_unwinder 288 }; 289 290 static void 291 fprint_dummy_frames (struct ui_file *file) 292 { 293 struct dummy_frame *s; 294 295 for (s = dummy_frame_stack; s != NULL; s = s->next) 296 { 297 gdb_print_host_address (s, file); 298 fprintf_unfiltered (file, ":"); 299 fprintf_unfiltered (file, " id="); 300 fprint_frame_id (file, s->id); 301 fprintf_unfiltered (file, "\n"); 302 } 303 } 304 305 static void 306 maintenance_print_dummy_frames (char *args, int from_tty) 307 { 308 if (args == NULL) 309 fprint_dummy_frames (gdb_stdout); 310 else 311 { 312 struct cleanup *cleanups; 313 struct ui_file *file = gdb_fopen (args, "w"); 314 315 if (file == NULL) 316 perror_with_name (_("maintenance print dummy-frames")); 317 cleanups = make_cleanup_ui_file_delete (file); 318 fprint_dummy_frames (file); 319 do_cleanups (cleanups); 320 } 321 } 322 323 extern void _initialize_dummy_frame (void); 324 325 void 326 _initialize_dummy_frame (void) 327 { 328 add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames, 329 _("Print the contents of the internal dummy-frame stack."), 330 &maintenanceprintlist); 331 332 observer_attach_inferior_created (cleanup_dummy_frames); 333 } 334