1/* Code dealing with dummy stack frames, for GDB, the GNU debugger.
2
3   Copyright 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
4   1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free
5   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 2 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, write to the Free Software
21   Foundation, Inc., 59 Temple Place - Suite 330,
22   Boston, MA 02111-1307, USA.  */
23
24
25#include "defs.h"
26#include "dummy-frame.h"
27#include "regcache.h"
28#include "frame.h"
29#include "inferior.h"
30#include "gdb_assert.h"
31#include "frame-unwind.h"
32#include "command.h"
33#include "gdbcmd.h"
34#include "gdb_string.h"
35
36/* Dummy frame.  This saves the processor state just prior to setting
37   up the inferior function call.  Older targets save the registers
38   on the target stack (but that really slows down function calls).  */
39
40struct dummy_frame
41{
42  struct dummy_frame *next;
43  /* This frame's ID.  Must match the value returned by
44     gdbarch_unwind_dummy_id.  */
45  struct frame_id id;
46  /* The caller's regcache.  */
47  struct regcache *regcache;
48};
49
50static struct dummy_frame *dummy_frame_stack = NULL;
51
52/* Function: deprecated_pc_in_call_dummy (pc)
53
54   Return non-zero if the PC falls in a dummy frame created by gdb for
55   an inferior call.  The code below which allows DECR_PC_AFTER_BREAK
56   is for infrun.c, which may give the function a PC without that
57   subtracted out.
58
59   FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
60   figure out what the real PC (as in the resume address) is BEFORE
61   calling this function.
62
63   NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of
64   infrun.c:adjust_pc_after_break (thanks), this function is now
65   always called with a correctly adjusted PC!
66
67   NOTE: cagney/2004-08-02: Code should not need to call this.  */
68
69int
70deprecated_pc_in_call_dummy (CORE_ADDR pc)
71{
72  struct dummy_frame *dummyframe;
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 + DECR_PC_AFTER_BREAK))
79	return 1;
80    }
81  return 0;
82}
83
84/* Push the caller's state, along with the dummy frame info, onto a
85   dummy-frame stack.  */
86
87void
88dummy_frame_push (struct regcache *caller_regcache,
89		  const struct frame_id *dummy_id)
90{
91  struct dummy_frame *dummy_frame;
92
93  /* Check to see if there are stale dummy frames, perhaps left over
94     from when a longjump took us out of a function that was called by
95     the debugger.  */
96  dummy_frame = dummy_frame_stack;
97  while (dummy_frame)
98    /* FIXME: cagney/2004-08-02: Should just test IDs.  */
99    if (frame_id_inner (dummy_frame->id, (*dummy_id)))
100      /* Stale -- destroy!  */
101      {
102	dummy_frame_stack = dummy_frame->next;
103	regcache_xfree (dummy_frame->regcache);
104	xfree (dummy_frame);
105	dummy_frame = dummy_frame_stack;
106      }
107    else
108      dummy_frame = dummy_frame->next;
109
110  dummy_frame = XZALLOC (struct dummy_frame);
111  dummy_frame->regcache = caller_regcache;
112  dummy_frame->id = (*dummy_id);
113  dummy_frame->next = dummy_frame_stack;
114  dummy_frame_stack = dummy_frame;
115}
116
117/* Return the dummy frame cache, it contains both the ID, and a
118   pointer to the regcache.  */
119struct dummy_frame_cache
120{
121  struct frame_id this_id;
122  struct regcache *prev_regcache;
123};
124
125int
126dummy_frame_sniffer (const struct frame_unwind *self,
127		     struct frame_info *next_frame,
128		     void **this_prologue_cache)
129{
130  struct dummy_frame *dummyframe;
131  struct frame_id this_id;
132
133  /* When unwinding a normal frame, the stack structure is determined
134     by analyzing the frame's function's code (be it using brute force
135     prologue analysis, or the dwarf2 CFI).  In the case of a dummy
136     frame, that simply isn't possible.  The PC is either the program
137     entry point, or some random address on the stack.  Trying to use
138     that PC to apply standard frame ID unwind techniques is just
139     asking for trouble.  */
140  /* Use an architecture specific method to extract the prev's dummy
141     ID from the next frame.  Note that this method uses
142     frame_register_unwind to obtain the register values needed to
143     determine the dummy frame's ID.  */
144  this_id = gdbarch_unwind_dummy_id (get_frame_arch (next_frame), next_frame);
145
146  /* Use that ID to find the corresponding cache entry.  */
147  for (dummyframe = dummy_frame_stack;
148       dummyframe != NULL;
149       dummyframe = dummyframe->next)
150    {
151      if (frame_id_eq (dummyframe->id, this_id))
152	{
153	  struct dummy_frame_cache *cache;
154	  cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
155	  cache->prev_regcache = dummyframe->regcache;
156	  cache->this_id = this_id;
157	  (*this_prologue_cache) = cache;
158	  return 1;
159	}
160    }
161  return 0;
162}
163
164/* Given a call-dummy dummy-frame, return the registers.  Here the
165   register value is taken from the local copy of the register buffer.  */
166
167static void
168dummy_frame_prev_register (struct frame_info *next_frame,
169			   void **this_prologue_cache,
170			   int regnum, int *optimized,
171			   enum lval_type *lvalp, CORE_ADDR *addrp,
172			   int *realnum, void *bufferp)
173{
174  /* The dummy-frame sniffer always fills in the cache.  */
175  struct dummy_frame_cache *cache = (*this_prologue_cache);
176  gdb_assert (cache != NULL);
177
178  /* Describe the register's location.  Generic dummy frames always
179     have the register value in an ``expression''.  */
180  *optimized = 0;
181  *lvalp = not_lval;
182  *addrp = 0;
183  *realnum = -1;
184
185  /* If needed, find and return the value of the register.  */
186  if (bufferp != NULL)
187    {
188      /* Return the actual value.  */
189      /* Use the regcache_cooked_read() method so that it, on the fly,
190         constructs either a raw or pseudo register from the raw
191         register cache.  */
192      regcache_cooked_read (cache->prev_regcache, regnum, bufferp);
193    }
194}
195
196/* Assuming that THIS frame is a dummy (remember, the NEXT and not
197   THIS frame is passed in), return the ID of THIS frame.  That ID is
198   determined by examining the NEXT frame's unwound registers using
199   the method unwind_dummy_id().  As a side effect, THIS dummy frame's
200   dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
201
202static void
203dummy_frame_this_id (struct frame_info *next_frame,
204		     void **this_prologue_cache,
205		     struct frame_id *this_id)
206{
207  /* The dummy-frame sniffer always fills in the cache.  */
208  struct dummy_frame_cache *cache = (*this_prologue_cache);
209  gdb_assert (cache != NULL);
210  (*this_id) = cache->this_id;
211}
212
213static const struct frame_unwind dummy_frame_unwinder =
214{
215  DUMMY_FRAME,
216  dummy_frame_this_id,
217  dummy_frame_prev_register,
218  NULL,
219  dummy_frame_sniffer,
220};
221
222const struct frame_unwind *const dummy_frame_unwind = {
223  &dummy_frame_unwinder
224};
225
226static void
227fprint_dummy_frames (struct ui_file *file)
228{
229  struct dummy_frame *s;
230  for (s = dummy_frame_stack; s != NULL; s = s->next)
231    {
232      gdb_print_host_address (s, file);
233      fprintf_unfiltered (file, ":");
234      fprintf_unfiltered (file, " id=");
235      fprint_frame_id (file, s->id);
236      fprintf_unfiltered (file, "\n");
237    }
238}
239
240static void
241maintenance_print_dummy_frames (char *args, int from_tty)
242{
243  if (args == NULL)
244    fprint_dummy_frames (gdb_stdout);
245  else
246    {
247      struct ui_file *file = gdb_fopen (args, "w");
248      if (file == NULL)
249	perror_with_name ("maintenance print dummy-frames");
250      fprint_dummy_frames (file);
251      ui_file_delete (file);
252    }
253}
254
255extern void _initialize_dummy_frame (void);
256
257void
258_initialize_dummy_frame (void)
259{
260  add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
261	   "Print the contents of the internal dummy-frame stack.",
262	   &maintenanceprintlist);
263
264}
265