| 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 | |
| 25 | struct frame_data; |
| 26 | struct frame_info; |
| 27 | struct frame_id; |
| 28 | struct frame_unwind; |
| 29 | struct gdbarch; |
| 30 | struct 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 | |
| 50 | typedef 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 | |
| 77 | typedef 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 | |
| 113 | typedef 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 | |
| 121 | struct 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. */ |
| 140 | extern 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 | |
| 147 | typedef 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 | |
| 153 | extern 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 | |
| 159 | extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *next_frame, |
| 160 | void **this_cache); |
| 161 | |
| 162 | #endif |