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 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 for (dummyframe = dummy_frame_stack; 73 dummyframe != NULL; 74 dummyframe = dummyframe->next) 75 { 76 if ((pc >= dummyframe->id.code_addr) 77 && (pc <= dummyframe->id.code_addr 78 + gdbarch_decr_pc_after_break (gdbarch))) 79 return 1; 80 } 81 return 0; 82 } 83 84 /* Push the caller's state, along with the dummy frame info, onto the 85 dummy-frame stack. */ 86 87 void 88 dummy_frame_push (struct inferior_thread_state *caller_state, 89 const struct frame_id *dummy_id) 90 { 91 struct dummy_frame *dummy_frame; 92 93 dummy_frame = XZALLOC (struct dummy_frame); 94 dummy_frame->caller_state = caller_state; 95 dummy_frame->id = (*dummy_id); 96 dummy_frame->next = dummy_frame_stack; 97 dummy_frame_stack = dummy_frame; 98 } 99 100 /* Remove *DUMMY_PTR from the dummy frame stack. */ 101 102 static void 103 remove_dummy_frame (struct dummy_frame **dummy_ptr) 104 { 105 struct dummy_frame *dummy = *dummy_ptr; 106 107 *dummy_ptr = dummy->next; 108 discard_inferior_thread_state (dummy->caller_state); 109 xfree (dummy); 110 } 111 112 /* Pop *DUMMY_PTR, restoring program state to that before the 113 frame was created. */ 114 115 static void 116 pop_dummy_frame (struct dummy_frame **dummy_ptr) 117 { 118 struct dummy_frame *dummy; 119 120 restore_inferior_thread_state ((*dummy_ptr)->caller_state); 121 122 /* restore_inferior_status frees inf_state, 123 all that remains is to pop *dummy_ptr */ 124 dummy = *dummy_ptr; 125 *dummy_ptr = dummy->next; 126 xfree (dummy); 127 128 /* We've made right mess of GDB's local state, just discard 129 everything. */ 130 reinit_frame_cache (); 131 } 132 133 /* Look up DUMMY_ID. 134 Return NULL if not found. */ 135 136 static struct dummy_frame ** 137 lookup_dummy_frame (struct frame_id dummy_id) 138 { 139 struct dummy_frame **dp; 140 141 for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next) 142 { 143 if (frame_id_eq ((*dp)->id, dummy_id)) 144 return dp; 145 } 146 147 return NULL; 148 } 149 150 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the 151 frame was created. 152 On return reinit_frame_cache has been called. 153 If the frame isn't found, flag an internal error. 154 155 NOTE: This can only pop the one frame, even if it is in the middle of the 156 stack, because the other frames may be for different threads, and there's 157 currently no way to tell which stack frame is for which thread. */ 158 159 void 160 dummy_frame_pop (struct frame_id dummy_id) 161 { 162 struct dummy_frame **dp; 163 164 dp = lookup_dummy_frame (dummy_id); 165 gdb_assert (dp != NULL); 166 167 pop_dummy_frame (dp); 168 } 169 170 /* There may be stale dummy frames, perhaps left over from when a longjump took 171 us out of a function that was called by the debugger. Clean them up at 172 least once whenever we start a new inferior. */ 173 174 static void 175 cleanup_dummy_frames (struct target_ops *target, int from_tty) 176 { 177 while (dummy_frame_stack != NULL) 178 remove_dummy_frame (&dummy_frame_stack); 179 } 180 181 /* Return the dummy frame cache, it contains both the ID, and a 182 pointer to the regcache. */ 183 struct dummy_frame_cache 184 { 185 struct frame_id this_id; 186 struct regcache *prev_regcache; 187 }; 188 189 static int 190 dummy_frame_sniffer (const struct frame_unwind *self, 191 struct frame_info *this_frame, 192 void **this_prologue_cache) 193 { 194 struct dummy_frame *dummyframe; 195 struct frame_id this_id; 196 197 /* When unwinding a normal frame, the stack structure is determined 198 by analyzing the frame's function's code (be it using brute force 199 prologue analysis, or the dwarf2 CFI). In the case of a dummy 200 frame, that simply isn't possible. The PC is either the program 201 entry point, or some random address on the stack. Trying to use 202 that PC to apply standard frame ID unwind techniques is just 203 asking for trouble. */ 204 205 /* Don't bother unless there is at least one dummy frame. */ 206 if (dummy_frame_stack != NULL) 207 { 208 /* Use an architecture specific method to extract this frame's 209 dummy ID, assuming it is a dummy frame. */ 210 this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame); 211 212 /* Use that ID to find the corresponding cache entry. */ 213 for (dummyframe = dummy_frame_stack; 214 dummyframe != NULL; 215 dummyframe = dummyframe->next) 216 { 217 if (frame_id_eq (dummyframe->id, this_id)) 218 { 219 struct dummy_frame_cache *cache; 220 cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache); 221 cache->prev_regcache = get_inferior_thread_state_regcache (dummyframe->caller_state); 222 cache->this_id = this_id; 223 (*this_prologue_cache) = cache; 224 return 1; 225 } 226 } 227 } 228 return 0; 229 } 230 231 /* Given a call-dummy dummy-frame, return the registers. Here the 232 register value is taken from the local copy of the register buffer. */ 233 234 static struct value * 235 dummy_frame_prev_register (struct frame_info *this_frame, 236 void **this_prologue_cache, 237 int regnum) 238 { 239 struct dummy_frame_cache *cache = (*this_prologue_cache); 240 struct gdbarch *gdbarch = get_frame_arch (this_frame); 241 struct value *reg_val; 242 243 /* The dummy-frame sniffer always fills in the cache. */ 244 gdb_assert (cache != NULL); 245 246 /* Describe the register's location. Generic dummy frames always 247 have the register value in an ``expression''. */ 248 reg_val = value_zero (register_type (gdbarch, regnum), not_lval); 249 250 /* Use the regcache_cooked_read() method so that it, on the fly, 251 constructs either a raw or pseudo register from the raw 252 register cache. */ 253 regcache_cooked_read (cache->prev_regcache, regnum, 254 value_contents_writeable (reg_val)); 255 return reg_val; 256 } 257 258 /* Assuming that THIS_FRAME is a dummy, return its ID. That ID is 259 determined by examining the NEXT frame's unwound registers using 260 the method dummy_id(). As a side effect, THIS dummy frame's 261 dummy cache is located and and saved in THIS_PROLOGUE_CACHE. */ 262 263 static void 264 dummy_frame_this_id (struct frame_info *this_frame, 265 void **this_prologue_cache, 266 struct frame_id *this_id) 267 { 268 /* The dummy-frame sniffer always fills in the cache. */ 269 struct dummy_frame_cache *cache = (*this_prologue_cache); 270 gdb_assert (cache != NULL); 271 (*this_id) = cache->this_id; 272 } 273 274 static const struct frame_unwind dummy_frame_unwinder = 275 { 276 DUMMY_FRAME, 277 dummy_frame_this_id, 278 dummy_frame_prev_register, 279 NULL, 280 dummy_frame_sniffer, 281 }; 282 283 const struct frame_unwind *const dummy_frame_unwind = { 284 &dummy_frame_unwinder 285 }; 286 287 static void 288 fprint_dummy_frames (struct ui_file *file) 289 { 290 struct dummy_frame *s; 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 if (file == NULL) 311 perror_with_name (_("maintenance print dummy-frames")); 312 cleanups = make_cleanup_ui_file_delete (file); 313 fprint_dummy_frames (file); 314 do_cleanups (cleanups); 315 } 316 } 317 318 extern void _initialize_dummy_frame (void); 319 320 void 321 _initialize_dummy_frame (void) 322 { 323 add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames, 324 _("Print the contents of the internal dummy-frame stack."), 325 &maintenanceprintlist); 326 327 observer_attach_inferior_created (cleanup_dummy_frames); 328 } 329