| 1 | /* Code dealing with dummy stack frames, for GDB, the GNU debugger. |
| 2 | |
| 3 | Copyright (C) 1986-2014 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 <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 = XCNEW (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 | } |