1/* Definitions for a frame unwinder, for GDB, the GNU debugger.
2
3   Copyright 2003, 2004 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 2 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, write to the Free Software
19   Foundation, Inc., 59 Temple Place - Suite 330,
20   Boston, MA 02111-1307, USA.  */
21
22#if !defined (FRAME_UNWIND_H)
23#define FRAME_UNWIND_H 1
24
25struct frame_data;
26struct frame_info;
27struct frame_id;
28struct frame_unwind;
29struct gdbarch;
30struct regcache;
31
32#include "frame.h"		/* For enum frame_type.  */
33
34/* The following unwind functions assume a chain of frames forming the
35   sequence: (outer) prev <-> this <-> next (inner).  All the
36   functions are called with called with the next frame's `struct
37   frame_info' and and this frame's prologue cache.
38
39   THIS frame's register values can be obtained by unwinding NEXT
40   frame's registers (a recursive operation).
41
42   THIS frame's prologue cache can be used to cache information such
43   as where this frame's prologue stores the previous frame's
44   registers.  */
45
46/* Given the NEXT frame, take a wiff of THIS frame's registers (namely
47   the PC and attributes) and if SELF is the applicable unwinder,
48   return non-zero.  Possibly also initialize THIS_PROLOGUE_CACHE.  */
49
50typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
51				   struct frame_info *next_frame,
52				   void **this_prologue_cache);
53
54/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
55   use the NEXT frame, and its register unwind method, to determine
56   the frame ID of THIS frame.
57
58   A frame ID provides an invariant that can be used to re-identify an
59   instance of a frame.  It is a combination of the frame's `base' and
60   the frame's function's code address.
61
62   Traditionally, THIS frame's ID was determined by examining THIS
63   frame's function's prologue, and identifying the register/offset
64   used as THIS frame's base.
65
66   Example: An examination of THIS frame's prologue reveals that, on
67   entry, it saves the PC(+12), SP(+8), and R1(+4) registers
68   (decrementing the SP by 12).  Consequently, the frame ID's base can
69   be determined by adding 12 to the THIS frame's stack-pointer, and
70   the value of THIS frame's SP can be obtained by unwinding the NEXT
71   frame's SP.
72
73   THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
74   with the other unwind methods.  Memory for that cache should be
75   allocated using frame_obstack_zalloc().  */
76
77typedef void (frame_this_id_ftype) (struct frame_info *next_frame,
78				    void **this_prologue_cache,
79				    struct frame_id *this_id);
80
81/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
82   use the NEXT frame, and its register unwind method, to unwind THIS
83   frame's registers (returning the value of the specified register
84   REGNUM in the previous frame).
85
86   Traditionally, THIS frame's registers were unwound by examining
87   THIS frame's function's prologue and identifying which registers
88   that prolog code saved on the stack.
89
90   Example: An examination of THIS frame's prologue reveals that, on
91   entry, it saves the PC(+12), SP(+8), and R1(+4) registers
92   (decrementing the SP by 12).  Consequently, the value of the PC
93   register in the previous frame is found in memory at SP+12, and
94   THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
95
96   Why not pass in THIS_FRAME?  By passing in NEXT frame and THIS
97   cache, the supplied parameters are consistent with the sibling
98   function THIS_ID.
99
100   Can the code call ``frame_register (get_prev_frame (NEXT_FRAME))''?
101   Won't the call frame_register (THIS_FRAME) be faster?  Well,
102   ignoring the possability that the previous frame does not yet
103   exist, the ``frame_register (FRAME)'' function is expanded to
104   ``frame_register_unwind (get_next_frame (FRAME)'' and hence that
105   call will expand to ``frame_register_unwind (get_next_frame
106   (get_prev_frame (NEXT_FRAME)))''.  Might as well call
107   ``frame_register_unwind (NEXT_FRAME)'' directly.
108
109   THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
110   with the other unwind methods.  Memory for that cache should be
111   allocated using frame_obstack_zalloc().  */
112
113typedef void (frame_prev_register_ftype) (struct frame_info *next_frame,
114					  void **this_prologue_cache,
115					  int prev_regnum,
116					  int *optimized,
117					  enum lval_type * lvalp,
118					  CORE_ADDR *addrp,
119					  int *realnump, void *valuep);
120
121struct frame_unwind
122{
123  /* The frame's type.  Should this instead be a collection of
124     predicates that test the frame for various attributes?  */
125  enum frame_type type;
126  /* Should an attribute indicating the frame's address-in-block go
127     here?  */
128  frame_this_id_ftype *this_id;
129  frame_prev_register_ftype *prev_register;
130  const struct frame_data *unwind_data;
131  frame_sniffer_ftype *sniffer;
132};
133
134/* Register a frame unwinder, _prepending_ it to the front of the
135   search list (so it is sniffed before previously registered
136   unwinders).  By using a prepend, later calls can install unwinders
137   that override earlier calls.  This allows, for instance, an OSABI
138   to install a a more specific sigtramp unwinder that overrides the
139   traditional brute-force unwinder.  */
140extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
141					   const struct frame_unwind *unwinder);
142
143/* Given the NEXT frame, take a wiff of THIS frame's registers (namely
144   the PC and attributes) and if it is the applicable unwinder return
145   the unwind methods, or NULL if it is not.  */
146
147typedef const struct frame_unwind *(frame_unwind_sniffer_ftype) (struct frame_info *next_frame);
148
149/* Add a frame sniffer to the list.  The predicates are polled in the
150   order that they are appended.  The initial list contains the dummy
151   frame sniffer.  */
152
153extern void frame_unwind_append_sniffer (struct gdbarch *gdbarch,
154					 frame_unwind_sniffer_ftype *sniffer);
155
156/* Iterate through the next frame's sniffers until one returns with an
157   unwinder implementation.  Possibly initialize THIS_CACHE.  */
158
159extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *next_frame,
160							      void **this_cache);
161
162#endif
163