1 /* Definitions for a frame unwinder, for GDB, the GNU debugger. 2 3 Copyright (C) 2003-2019 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 23 struct frame_data; 24 struct frame_info; 25 struct frame_id; 26 struct frame_unwind; 27 struct gdbarch; 28 struct regcache; 29 struct value; 30 31 #include "frame.h" /* For enum frame_type. */ 32 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 this frame's `struct frame_info' and 36 prologue cache. 37 38 THIS frame's register values can be obtained by unwinding NEXT 39 frame's registers (a recursive operation). 40 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 43 registers. */ 44 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; but 48 only if returning 1. Initializing THIS_PROLOGUE_CACHE in other 49 cases (0 return) is invalid. In case of exception, the caller has 50 to set *THIS_PROLOGUE_CACHE to NULL. */ 51 52 typedef int (frame_sniffer_ftype) (const struct frame_unwind *self, 53 struct frame_info *this_frame, 54 void **this_prologue_cache); 55 56 typedef enum unwind_stop_reason (frame_unwind_stop_reason_ftype) 57 (struct frame_info *this_frame, void **this_prologue_cache); 58 59 /* A default frame sniffer which always accepts the frame. Used by 60 fallback prologue unwinders. */ 61 62 int default_frame_sniffer (const struct frame_unwind *self, 63 struct frame_info *this_frame, 64 void **this_prologue_cache); 65 66 /* A default stop_reason callback which always claims the frame is 67 unwindable. */ 68 69 enum unwind_stop_reason 70 default_frame_unwind_stop_reason (struct frame_info *this_frame, 71 void **this_cache); 72 73 /* A default unwind_pc callback that simply unwinds the register identified 74 by GDBARCH_PC_REGNUM. */ 75 76 extern CORE_ADDR default_unwind_pc (struct gdbarch *gdbarch, 77 struct frame_info *next_frame); 78 79 /* A default unwind_sp callback that simply unwinds the register identified 80 by GDBARCH_SP_REGNUM. */ 81 82 extern CORE_ADDR default_unwind_sp (struct gdbarch *gdbarch, 83 struct frame_info *next_frame); 84 85 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner); 86 use THIS frame, and through it the NEXT frame's register unwind 87 method, to determine the frame ID of THIS frame. 88 89 A frame ID provides an invariant that can be used to re-identify an 90 instance of a frame. It is a combination of the frame's `base' and 91 the frame's function's code address. 92 93 Traditionally, THIS frame's ID was determined by examining THIS 94 frame's function's prologue, and identifying the register/offset 95 used as THIS frame's base. 96 97 Example: An examination of THIS frame's prologue reveals that, on 98 entry, it saves the PC(+12), SP(+8), and R1(+4) registers 99 (decrementing the SP by 12). Consequently, the frame ID's base can 100 be determined by adding 12 to the THIS frame's stack-pointer, and 101 the value of THIS frame's SP can be obtained by unwinding the NEXT 102 frame's SP. 103 104 THIS_PROLOGUE_CACHE can be used to share any prolog analysis data 105 with the other unwind methods. Memory for that cache should be 106 allocated using FRAME_OBSTACK_ZALLOC(). */ 107 108 typedef void (frame_this_id_ftype) (struct frame_info *this_frame, 109 void **this_prologue_cache, 110 struct frame_id *this_id); 111 112 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner); 113 use THIS frame, and implicitly the NEXT frame's register unwind 114 method, to unwind THIS frame's registers (returning the value of 115 the specified register REGNUM in the previous frame). 116 117 Traditionally, THIS frame's registers were unwound by examining 118 THIS frame's function's prologue and identifying which registers 119 that prolog code saved on the stack. 120 121 Example: An examination of THIS frame's prologue reveals that, on 122 entry, it saves the PC(+12), SP(+8), and R1(+4) registers 123 (decrementing the SP by 12). Consequently, the value of the PC 124 register in the previous frame is found in memory at SP+12, and 125 THIS frame's SP can be obtained by unwinding the NEXT frame's SP. 126 127 This function takes THIS_FRAME as an argument. It can find the 128 values of registers in THIS frame by calling get_frame_register 129 (THIS_FRAME), and reinvoke itself to find other registers in the 130 PREVIOUS frame by calling frame_unwind_register (THIS_FRAME). 131 132 The result is a GDB value object describing the register value. It 133 may be a lazy reference to memory, a lazy reference to the value of 134 a register in THIS frame, or a non-lvalue. 135 136 THIS_PROLOGUE_CACHE can be used to share any prolog analysis data 137 with the other unwind methods. Memory for that cache should be 138 allocated using FRAME_OBSTACK_ZALLOC(). */ 139 140 typedef struct value * (frame_prev_register_ftype) 141 (struct frame_info *this_frame, void **this_prologue_cache, 142 int regnum); 143 144 /* Deallocate extra memory associated with the frame cache if any. */ 145 146 typedef void (frame_dealloc_cache_ftype) (struct frame_info *self, 147 void *this_cache); 148 149 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner); 150 use THIS frame, and implicitly the NEXT frame's register unwind 151 method, return PREV frame's architecture. */ 152 153 typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame, 154 void **this_prologue_cache); 155 156 struct frame_unwind 157 { 158 /* The frame's type. Should this instead be a collection of 159 predicates that test the frame for various attributes? */ 160 enum frame_type type; 161 /* Should an attribute indicating the frame's address-in-block go 162 here? */ 163 frame_unwind_stop_reason_ftype *stop_reason; 164 frame_this_id_ftype *this_id; 165 frame_prev_register_ftype *prev_register; 166 const struct frame_data *unwind_data; 167 frame_sniffer_ftype *sniffer; 168 frame_dealloc_cache_ftype *dealloc_cache; 169 frame_prev_arch_ftype *prev_arch; 170 }; 171 172 /* Register a frame unwinder, _prepending_ it to the front of the 173 search list (so it is sniffed before previously registered 174 unwinders). By using a prepend, later calls can install unwinders 175 that override earlier calls. This allows, for instance, an OSABI 176 to install a more specific sigtramp unwinder that overrides the 177 traditional brute-force unwinder. */ 178 extern void frame_unwind_prepend_unwinder (struct gdbarch *, 179 const struct frame_unwind *); 180 181 /* Add a frame sniffer to the list. The predicates are polled in the 182 order that they are appended. The initial list contains the dummy 183 frame sniffer. */ 184 185 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch, 186 const struct frame_unwind *unwinder); 187 188 /* Iterate through sniffers for THIS_FRAME frame until one returns with an 189 unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set 190 by this function. Possibly initialize THIS_CACHE. */ 191 192 extern void frame_unwind_find_by_frame (struct frame_info *this_frame, 193 void **this_cache); 194 195 /* Helper functions for value-based register unwinding. These return 196 a (possibly lazy) value of the appropriate type. */ 197 198 /* Return a value which indicates that FRAME did not save REGNUM. */ 199 200 struct value *frame_unwind_got_optimized (struct frame_info *frame, 201 int regnum); 202 203 /* Return a value which indicates that FRAME copied REGNUM into 204 register NEW_REGNUM. */ 205 206 struct value *frame_unwind_got_register (struct frame_info *frame, int regnum, 207 int new_regnum); 208 209 /* Return a value which indicates that FRAME saved REGNUM in memory at 210 ADDR. */ 211 212 struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum, 213 CORE_ADDR addr); 214 215 /* Return a value which indicates that FRAME's saved version of 216 REGNUM has a known constant (computed) value of VAL. */ 217 218 struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum, 219 ULONGEST val); 220 221 /* Return a value which indicates that FRAME's saved version of 222 REGNUM has a known constant (computed) value which is stored 223 inside BUF. */ 224 225 struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum, 226 gdb_byte *buf); 227 228 /* Return a value which indicates that FRAME's saved version of REGNUM 229 has a known constant (computed) value of ADDR. Convert the 230 CORE_ADDR to a target address if necessary. */ 231 232 struct value *frame_unwind_got_address (struct frame_info *frame, int regnum, 233 CORE_ADDR addr); 234 235 #endif 236