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