1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
3 Copyright (C) 2003, 2004, 2007, 2008 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/>. */
20 #if !defined (FRAME_UNWIND_H)
21 #define FRAME_UNWIND_H 1
31 #include "frame.h" /* For enum frame_type. */
33 /* The following unwind functions assume a chain of frames forming the
34 sequence: (outer) prev <-> this <-> next (inner). All the
35 functions are called with called with the next frame's `struct
36 frame_info' and and this frame's prologue cache.
38 THIS frame's register values can be obtained by unwinding NEXT
39 frame's registers (a recursive operation).
41 THIS frame's prologue cache can be used to cache information such
42 as where this frame's prologue stores the previous frame's
45 /* Given THIS frame, take a whiff of its registers (namely
46 the PC and attributes) and if SELF is the applicable unwinder,
47 return non-zero. Possibly also initialize THIS_PROLOGUE_CACHE. */
49 typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
50 struct frame_info *this_frame,
51 void **this_prologue_cache);
53 /* A default frame sniffer which always accepts the frame. Used by
54 fallback prologue unwinders. */
56 int default_frame_sniffer (const struct frame_unwind *self,
57 struct frame_info *this_frame,
58 void **this_prologue_cache);
60 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
61 use THIS frame, and through it the NEXT frame's register unwind
62 method, to determine the frame ID of THIS frame.
64 A frame ID provides an invariant that can be used to re-identify an
65 instance of a frame. It is a combination of the frame's `base' and
66 the frame's function's code address.
68 Traditionally, THIS frame's ID was determined by examining THIS
69 frame's function's prologue, and identifying the register/offset
70 used as THIS frame's base.
72 Example: An examination of THIS frame's prologue reveals that, on
73 entry, it saves the PC(+12), SP(+8), and R1(+4) registers
74 (decrementing the SP by 12). Consequently, the frame ID's base can
75 be determined by adding 12 to the THIS frame's stack-pointer, and
76 the value of THIS frame's SP can be obtained by unwinding the NEXT
79 THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
80 with the other unwind methods. Memory for that cache should be
81 allocated using FRAME_OBSTACK_ZALLOC(). */
83 typedef void (frame_this_id_ftype) (struct frame_info *this_frame,
84 void **this_prologue_cache,
85 struct frame_id *this_id);
87 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
88 use THIS frame, and implicitly the NEXT frame's register unwind
89 method, to unwind THIS frame's registers (returning the value of
90 the specified register REGNUM in the previous frame).
92 Traditionally, THIS frame's registers were unwound by examining
93 THIS frame's function's prologue and identifying which registers
94 that prolog code saved on the stack.
96 Example: An examination of THIS frame's prologue reveals that, on
97 entry, it saves the PC(+12), SP(+8), and R1(+4) registers
98 (decrementing the SP by 12). Consequently, the value of the PC
99 register in the previous frame is found in memory at SP+12, and
100 THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
102 This function takes THIS_FRAME as an argument. It can find the
103 values of registers in THIS frame by calling get_frame_register
104 (THIS_FRAME), and reinvoke itself to find other registers in the
105 PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
107 The result is a GDB value object describing the register value. It
108 may be a lazy reference to memory, a lazy reference to the value of
109 a register in THIS frame, or a non-lvalue.
111 THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
112 with the other unwind methods. Memory for that cache should be
113 allocated using FRAME_OBSTACK_ZALLOC(). */
115 typedef struct value * (frame_prev_register_ftype)
116 (struct frame_info *this_frame, void **this_prologue_cache,
119 /* Deallocate extra memory associated with the frame cache if any. */
121 typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
126 /* The frame's type. Should this instead be a collection of
127 predicates that test the frame for various attributes? */
128 enum frame_type type;
129 /* Should an attribute indicating the frame's address-in-block go
131 frame_this_id_ftype *this_id;
132 frame_prev_register_ftype *prev_register;
133 const struct frame_data *unwind_data;
134 frame_sniffer_ftype *sniffer;
135 frame_dealloc_cache_ftype *dealloc_cache;
138 /* Register a frame unwinder, _prepending_ it to the front of the
139 search list (so it is sniffed before previously registered
140 unwinders). By using a prepend, later calls can install unwinders
141 that override earlier calls. This allows, for instance, an OSABI
142 to install a a more specific sigtramp unwinder that overrides the
143 traditional brute-force unwinder. */
144 extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
145 const struct frame_unwind *unwinder);
147 /* Add a frame sniffer to the list. The predicates are polled in the
148 order that they are appended. The initial list contains the dummy
151 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
152 const struct frame_unwind *unwinder);
154 /* Iterate through sniffers for THIS frame until one returns with an
155 unwinder implementation. Possibly initialize THIS_CACHE. */
157 extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *this_frame,
160 /* Helper functions for value-based register unwinding. These return
161 a (possibly lazy) value of the appropriate type. */
163 /* Return a value which indicates that FRAME did not save REGNUM. */
165 struct value *frame_unwind_got_optimized (struct frame_info *frame,
168 /* Return a value which indicates that FRAME copied REGNUM into
169 register NEW_REGNUM. */
171 struct value *frame_unwind_got_register (struct frame_info *frame, int regnum,
174 /* Return a value which indicates that FRAME saved REGNUM in memory at
177 struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum,
180 /* Return a value which indicates that FRAME's saved version of
181 REGNUM has a known constant (computed) value of VAL. */
183 struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum,
186 /* Return a value which indicates that FRAME's saved version of REGNUM
187 has a known constant (computed) value of ADDR. Convert the
188 CORE_ADDR to a target address if necessary. */
190 struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,