1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
3 Copyright (C) 1986-2014 Free Software Foundation, Inc.
5 This file is part of GDB.
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.
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.
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/>. */
22 #include "dummy-frame.h"
26 #include "gdb_assert.h"
27 #include "frame-unwind.h"
32 #include "gdbthread.h"
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). */
40 struct dummy_frame *next;
41 /* This frame's ID. Must match the value returned by
44 /* The caller's state prior to the call. */
45 struct infcall_suspend_state *caller_state;
48 static struct dummy_frame *dummy_frame_stack = NULL;
50 /* Push the caller's state, along with the dummy frame info, onto the
54 dummy_frame_push (struct infcall_suspend_state *caller_state,
55 const struct frame_id *dummy_id)
57 struct dummy_frame *dummy_frame;
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;
66 /* Remove *DUMMY_PTR from the dummy frame stack. */
69 remove_dummy_frame (struct dummy_frame **dummy_ptr)
71 struct dummy_frame *dummy = *dummy_ptr;
73 *dummy_ptr = dummy->next;
74 discard_infcall_suspend_state (dummy->caller_state);
78 /* Delete any breakpoint B which is a momentary breakpoint for return from
79 inferior call matching DUMMY_VOIDP. */
82 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp)
84 struct dummy_frame *dummy = dummy_voidp;
86 if (b->thread == pid_to_thread_id (inferior_ptid)
87 && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id))
89 while (b->related_breakpoint != b)
90 delete_breakpoint (b->related_breakpoint);
92 delete_breakpoint (b);
94 /* Stop the traversal. */
98 /* Continue the traversal. */
102 /* Pop *DUMMY_PTR, restoring program state to that before the
103 frame was created. */
106 pop_dummy_frame (struct dummy_frame **dummy_ptr)
108 struct dummy_frame *dummy = *dummy_ptr;
110 restore_infcall_suspend_state (dummy->caller_state);
112 iterate_over_breakpoints (pop_dummy_frame_bpt, dummy);
114 /* restore_infcall_control_state frees inf_state,
115 all that remains is to pop *dummy_ptr. */
116 *dummy_ptr = dummy->next;
119 /* We've made right mess of GDB's local state, just discard
121 reinit_frame_cache ();
125 Return NULL if not found. */
127 static struct dummy_frame **
128 lookup_dummy_frame (struct frame_id dummy_id)
130 struct dummy_frame **dp;
132 for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
134 if (frame_id_eq ((*dp)->id, dummy_id))
141 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the
143 On return reinit_frame_cache has been called.
144 If the frame isn't found, flag an internal error.
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. */
151 dummy_frame_pop (struct frame_id dummy_id)
153 struct dummy_frame **dp;
155 dp = lookup_dummy_frame (dummy_id);
156 gdb_assert (dp != NULL);
158 pop_dummy_frame (dp);
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. */
165 dummy_frame_discard (struct frame_id dummy_id)
167 struct dummy_frame **dp;
169 dp = lookup_dummy_frame (dummy_id);
171 remove_dummy_frame (dp);
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. */
179 cleanup_dummy_frames (struct target_ops *target, int from_tty)
181 while (dummy_frame_stack != NULL)
182 remove_dummy_frame (&dummy_frame_stack);
185 /* Return the dummy frame cache, it contains both the ID, and a
186 pointer to the regcache. */
187 struct dummy_frame_cache
189 struct frame_id this_id;
190 struct regcache *prev_regcache;
194 dummy_frame_sniffer (const struct frame_unwind *self,
195 struct frame_info *this_frame,
196 void **this_prologue_cache)
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. */
206 /* Don't bother unless there is at least one dummy frame. */
207 if (dummy_frame_stack != NULL)
209 struct dummy_frame *dummyframe;
210 /* Use an architecture specific method to extract this frame's
211 dummy ID, assuming it is a dummy frame. */
212 struct frame_id this_id
213 = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
215 /* Use that ID to find the corresponding cache entry. */
216 for (dummyframe = dummy_frame_stack;
218 dummyframe = dummyframe->next)
220 if (frame_id_eq (dummyframe->id, this_id))
222 struct dummy_frame_cache *cache;
224 cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
225 cache->prev_regcache = get_infcall_suspend_state_regcache
226 (dummyframe->caller_state);
227 cache->this_id = this_id;
228 (*this_prologue_cache) = cache;
236 /* Given a call-dummy dummy-frame, return the registers. Here the
237 register value is taken from the local copy of the register buffer. */
239 static struct value *
240 dummy_frame_prev_register (struct frame_info *this_frame,
241 void **this_prologue_cache,
244 struct dummy_frame_cache *cache = (*this_prologue_cache);
245 struct gdbarch *gdbarch = get_frame_arch (this_frame);
246 struct value *reg_val;
248 /* The dummy-frame sniffer always fills in the cache. */
249 gdb_assert (cache != NULL);
251 /* Describe the register's location. Generic dummy frames always
252 have the register value in an ``expression''. */
253 reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
255 /* Use the regcache_cooked_read() method so that it, on the fly,
256 constructs either a raw or pseudo register from the raw
258 regcache_cooked_read (cache->prev_regcache, regnum,
259 value_contents_writeable (reg_val));
263 /* Assuming that THIS_FRAME is a dummy, return its ID. That ID is
264 determined by examining the NEXT frame's unwound registers using
265 the method dummy_id(). As a side effect, THIS dummy frame's
266 dummy cache is located and saved in THIS_PROLOGUE_CACHE. */
269 dummy_frame_this_id (struct frame_info *this_frame,
270 void **this_prologue_cache,
271 struct frame_id *this_id)
273 /* The dummy-frame sniffer always fills in the cache. */
274 struct dummy_frame_cache *cache = (*this_prologue_cache);
276 gdb_assert (cache != NULL);
277 (*this_id) = cache->this_id;
280 const struct frame_unwind dummy_frame_unwind =
283 default_frame_unwind_stop_reason,
285 dummy_frame_prev_register,
291 fprint_dummy_frames (struct ui_file *file)
293 struct dummy_frame *s;
295 for (s = dummy_frame_stack; s != NULL; s = s->next)
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");
306 maintenance_print_dummy_frames (char *args, int from_tty)
309 fprint_dummy_frames (gdb_stdout);
312 struct cleanup *cleanups;
313 struct ui_file *file = gdb_fopen (args, "w");
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);
323 extern void _initialize_dummy_frame (void);
326 _initialize_dummy_frame (void)
328 add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
329 _("Print the contents of the internal dummy-frame stack."),
330 &maintenanceprintlist);
332 observer_attach_inferior_created (cleanup_dummy_frames);