1/* Definitions for a frame unwinder, for GDB, the GNU debugger. 2 3 Copyright (C) 2003-2020 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; 29struct 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 52typedef int (frame_sniffer_ftype) (const struct frame_unwind *self, 53 struct frame_info *this_frame, 54 void **this_prologue_cache); 55 56typedef 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 62int 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 69enum 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 76extern 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 82extern 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 108typedef 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 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 143typedef struct value * (frame_prev_register_ftype) 144 (struct frame_info *this_frame, void **this_prologue_cache, 145 int regnum); 146 147/* Deallocate extra memory associated with the frame cache if any. */ 148 149typedef void (frame_dealloc_cache_ftype) (struct 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 156typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame, 157 void **this_prologue_cache); 158 159struct frame_unwind 160{ 161 /* The frame's type. Should this instead be a collection of 162 predicates that test the frame for various attributes? */ 163 enum frame_type type; 164 /* Should an attribute indicating the frame's address-in-block go 165 here? */ 166 frame_unwind_stop_reason_ftype *stop_reason; 167 frame_this_id_ftype *this_id; 168 frame_prev_register_ftype *prev_register; 169 const struct frame_data *unwind_data; 170 frame_sniffer_ftype *sniffer; 171 frame_dealloc_cache_ftype *dealloc_cache; 172 frame_prev_arch_ftype *prev_arch; 173}; 174 175/* Register a frame unwinder, _prepending_ it to the front of the 176 search list (so it is sniffed before previously registered 177 unwinders). By using a prepend, later calls can install unwinders 178 that override earlier calls. This allows, for instance, an OSABI 179 to install a more specific sigtramp unwinder that overrides the 180 traditional brute-force unwinder. */ 181extern void frame_unwind_prepend_unwinder (struct gdbarch *, 182 const struct frame_unwind *); 183 184/* Add a frame sniffer to the list. The predicates are polled in the 185 order that they are appended. The initial list contains the dummy 186 frame sniffer. */ 187 188extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch, 189 const struct frame_unwind *unwinder); 190 191/* Iterate through sniffers for THIS_FRAME frame until one returns with an 192 unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set 193 by this function. Possibly initialize THIS_CACHE. */ 194 195extern void frame_unwind_find_by_frame (struct frame_info *this_frame, 196 void **this_cache); 197 198/* Helper functions for value-based register unwinding. These return 199 a (possibly lazy) value of the appropriate type. */ 200 201/* Return a value which indicates that FRAME did not save REGNUM. */ 202 203struct value *frame_unwind_got_optimized (struct frame_info *frame, 204 int regnum); 205 206/* Return a value which indicates that FRAME copied REGNUM into 207 register NEW_REGNUM. */ 208 209struct value *frame_unwind_got_register (struct frame_info *frame, int regnum, 210 int new_regnum); 211 212/* Return a value which indicates that FRAME saved REGNUM in memory at 213 ADDR. */ 214 215struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum, 216 CORE_ADDR addr); 217 218/* Return a value which indicates that FRAME's saved version of 219 REGNUM has a known constant (computed) value of VAL. */ 220 221struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum, 222 ULONGEST val); 223 224/* Return a value which indicates that FRAME's saved version of 225 REGNUM has a known constant (computed) value which is stored 226 inside BUF. */ 227 228struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum, 229 gdb_byte *buf); 230 231/* Return a value which indicates that FRAME's saved version of REGNUM 232 has a known constant (computed) value of ADDR. Convert the 233 CORE_ADDR to a target address if necessary. */ 234 235struct value *frame_unwind_got_address (struct frame_info *frame, int regnum, 236 CORE_ADDR addr); 237 238#endif 239