1 /* Definitions for a frame unwinder, for GDB, the GNU debugger. 2 3 Copyright (C) 2003-2023 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 class frame_info_ptr; 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 frame_info_ptr this_frame, 54 void **this_prologue_cache); 55 56 typedef enum unwind_stop_reason (frame_unwind_stop_reason_ftype) 57 (frame_info_ptr 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 frame_info_ptr 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 (frame_info_ptr 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 frame_info_ptr 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 frame_info_ptr 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) (frame_info_ptr 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 If the previous frame's register was not saved by THIS_FRAME and is 137 therefore undefined, return a wholly optimized-out not_lval value. 138 139 THIS_PROLOGUE_CACHE can be used to share any prolog analysis data 140 with the other unwind methods. Memory for that cache should be 141 allocated using FRAME_OBSTACK_ZALLOC(). */ 142 143 typedef struct value * (frame_prev_register_ftype) 144 (frame_info_ptr this_frame, void **this_prologue_cache, 145 int regnum); 146 147 /* Deallocate extra memory associated with the frame cache if any. */ 148 149 typedef void (frame_dealloc_cache_ftype) (frame_info *self, 150 void *this_cache); 151 152 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner); 153 use THIS frame, and implicitly the NEXT frame's register unwind 154 method, return PREV frame's architecture. */ 155 156 typedef struct gdbarch *(frame_prev_arch_ftype) (frame_info_ptr this_frame, 157 void **this_prologue_cache); 158 159 struct frame_unwind 160 { 161 const char *name; 162 /* The frame's type. Should this instead be a collection of 163 predicates that test the frame for various attributes? */ 164 enum frame_type type; 165 /* Should an attribute indicating the frame's address-in-block go 166 here? */ 167 frame_unwind_stop_reason_ftype *stop_reason; 168 frame_this_id_ftype *this_id; 169 frame_prev_register_ftype *prev_register; 170 const struct frame_data *unwind_data; 171 frame_sniffer_ftype *sniffer; 172 frame_dealloc_cache_ftype *dealloc_cache; 173 frame_prev_arch_ftype *prev_arch; 174 }; 175 176 /* Register a frame unwinder, _prepending_ it to the front of the 177 search list (so it is sniffed before previously registered 178 unwinders). By using a prepend, later calls can install unwinders 179 that override earlier calls. This allows, for instance, an OSABI 180 to install a more specific sigtramp unwinder that overrides the 181 traditional brute-force unwinder. */ 182 extern void frame_unwind_prepend_unwinder (struct gdbarch *, 183 const struct frame_unwind *); 184 185 /* Add a frame sniffer to the list. The predicates are polled in the 186 order that they are appended. The initial list contains the dummy 187 frame sniffer. */ 188 189 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch, 190 const struct frame_unwind *unwinder); 191 192 /* Iterate through sniffers for THIS_FRAME frame until one returns with an 193 unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set 194 by this function. Possibly initialize THIS_CACHE. */ 195 196 extern void frame_unwind_find_by_frame (frame_info_ptr this_frame, 197 void **this_cache); 198 199 /* Helper functions for value-based register unwinding. These return 200 a (possibly lazy) value of the appropriate type. */ 201 202 /* Return a value which indicates that FRAME did not save REGNUM. */ 203 204 struct value *frame_unwind_got_optimized (frame_info_ptr frame, 205 int regnum); 206 207 /* Return a value which indicates that FRAME copied REGNUM into 208 register NEW_REGNUM. */ 209 210 struct value *frame_unwind_got_register (frame_info_ptr frame, int regnum, 211 int new_regnum); 212 213 /* Return a value which indicates that FRAME saved REGNUM in memory at 214 ADDR. */ 215 216 struct value *frame_unwind_got_memory (frame_info_ptr frame, int regnum, 217 CORE_ADDR addr); 218 219 /* Return a value which indicates that FRAME's saved version of 220 REGNUM has a known constant (computed) value of VAL. */ 221 222 struct value *frame_unwind_got_constant (frame_info_ptr frame, int regnum, 223 ULONGEST val); 224 225 /* Return a value which indicates that FRAME's saved version of 226 REGNUM has a known constant (computed) value which is stored 227 inside BUF. */ 228 229 struct value *frame_unwind_got_bytes (frame_info_ptr frame, int regnum, 230 const gdb_byte *buf); 231 232 /* Return a value which indicates that FRAME's saved version of REGNUM 233 has a known constant (computed) value of ADDR. Convert the 234 CORE_ADDR to a target address if necessary. */ 235 236 struct value *frame_unwind_got_address (frame_info_ptr frame, int regnum, 237 CORE_ADDR addr); 238 239 #endif 240