1/* Definitions for a frame unwinder, for GDB, the GNU debugger.
2
3   Copyright (C) 2003, 2004, 2007 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#if !defined (FRAME_UNWIND_H)
21#define FRAME_UNWIND_H 1
22
23struct frame_data;
24struct frame_info;
25struct frame_id;
26struct frame_unwind;
27struct gdbarch;
28struct regcache;
29
30#include "frame.h"		/* For enum frame_type.  */
31
32/* The following unwind functions assume a chain of frames forming the
33   sequence: (outer) prev <-> this <-> next (inner).  All the
34   functions are called with called with the next frame's `struct
35   frame_info' and and this frame's prologue cache.
36
37   THIS frame's register values can be obtained by unwinding NEXT
38   frame's registers (a recursive operation).
39
40   THIS frame's prologue cache can be used to cache information such
41   as where this frame's prologue stores the previous frame's
42   registers.  */
43
44/* Given the NEXT frame, take a wiff of THIS frame's registers (namely
45   the PC and attributes) and if SELF is the applicable unwinder,
46   return non-zero.  Possibly also initialize THIS_PROLOGUE_CACHE.  */
47
48typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
49				   struct frame_info *next_frame,
50				   void **this_prologue_cache);
51
52/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
53   use the NEXT frame, and its register unwind method, to determine
54   the frame ID of THIS frame.
55
56   A frame ID provides an invariant that can be used to re-identify an
57   instance of a frame.  It is a combination of the frame's `base' and
58   the frame's function's code address.
59
60   Traditionally, THIS frame's ID was determined by examining THIS
61   frame's function's prologue, and identifying the register/offset
62   used as THIS frame's base.
63
64   Example: An examination of THIS frame's prologue reveals that, on
65   entry, it saves the PC(+12), SP(+8), and R1(+4) registers
66   (decrementing the SP by 12).  Consequently, the frame ID's base can
67   be determined by adding 12 to the THIS frame's stack-pointer, and
68   the value of THIS frame's SP can be obtained by unwinding the NEXT
69   frame's SP.
70
71   THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
72   with the other unwind methods.  Memory for that cache should be
73   allocated using FRAME_OBSTACK_ZALLOC().  */
74
75typedef void (frame_this_id_ftype) (struct frame_info *next_frame,
76				    void **this_prologue_cache,
77				    struct frame_id *this_id);
78
79/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
80   use the NEXT frame, and its register unwind method, to unwind THIS
81   frame's registers (returning the value of the specified register
82   REGNUM in the previous frame).
83
84   Traditionally, THIS frame's registers were unwound by examining
85   THIS frame's function's prologue and identifying which registers
86   that prolog code saved on the stack.
87
88   Example: An examination of THIS frame's prologue reveals that, on
89   entry, it saves the PC(+12), SP(+8), and R1(+4) registers
90   (decrementing the SP by 12).  Consequently, the value of the PC
91   register in the previous frame is found in memory at SP+12, and
92   THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
93
94   Why not pass in THIS_FRAME?  By passing in NEXT frame and THIS
95   cache, the supplied parameters are consistent with the sibling
96   function THIS_ID.
97
98   Can the code call ``frame_register (get_prev_frame (NEXT_FRAME))''?
99   Won't the call frame_register (THIS_FRAME) be faster?  Well,
100   ignoring the possability that the previous frame does not yet
101   exist, the ``frame_register (FRAME)'' function is expanded to
102   ``frame_register_unwind (get_next_frame (FRAME)'' and hence that
103   call will expand to ``frame_register_unwind (get_next_frame
104   (get_prev_frame (NEXT_FRAME)))''.  Might as well call
105   ``frame_register_unwind (NEXT_FRAME)'' directly.
106
107   THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
108   with the other unwind methods.  Memory for that cache should be
109   allocated using FRAME_OBSTACK_ZALLOC().  */
110
111typedef void (frame_prev_register_ftype) (struct frame_info *next_frame,
112					  void **this_prologue_cache,
113					  int prev_regnum,
114					  int *optimized,
115					  enum lval_type * lvalp,
116					  CORE_ADDR *addrp,
117					  int *realnump, gdb_byte *valuep);
118
119/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
120   use the NEXT frame, and its register unwind method, to return the PREV
121   frame's program-counter.  */
122
123typedef CORE_ADDR (frame_prev_pc_ftype) (struct frame_info *next_frame,
124					 void **this_prologue_cache);
125
126/* Deallocate extra memory associated with the frame cache if any.  */
127
128typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
129					  void *this_cache);
130
131struct frame_unwind
132{
133  /* The frame's type.  Should this instead be a collection of
134     predicates that test the frame for various attributes?  */
135  enum frame_type type;
136  /* Should an attribute indicating the frame's address-in-block go
137     here?  */
138  frame_this_id_ftype *this_id;
139  frame_prev_register_ftype *prev_register;
140  const struct frame_data *unwind_data;
141  frame_sniffer_ftype *sniffer;
142  frame_prev_pc_ftype *prev_pc;
143  frame_dealloc_cache_ftype *dealloc_cache;
144};
145
146/* Register a frame unwinder, _prepending_ it to the front of the
147   search list (so it is sniffed before previously registered
148   unwinders).  By using a prepend, later calls can install unwinders
149   that override earlier calls.  This allows, for instance, an OSABI
150   to install a a more specific sigtramp unwinder that overrides the
151   traditional brute-force unwinder.  */
152extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
153					   const struct frame_unwind *unwinder);
154
155/* Given the NEXT frame, take a wiff of THIS frame's registers (namely
156   the PC and attributes) and if it is the applicable unwinder return
157   the unwind methods, or NULL if it is not.  */
158
159typedef const struct frame_unwind *(frame_unwind_sniffer_ftype) (struct frame_info *next_frame);
160
161/* Add a frame sniffer to the list.  The predicates are polled in the
162   order that they are appended.  The initial list contains the dummy
163   frame sniffer.  */
164
165extern void frame_unwind_append_sniffer (struct gdbarch *gdbarch,
166					 frame_unwind_sniffer_ftype *sniffer);
167
168/* Iterate through the next frame's sniffers until one returns with an
169   unwinder implementation.  Possibly initialize THIS_CACHE.  */
170
171extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *next_frame,
172							      void **this_cache);
173
174#endif
175