gdb/frame-unwind.h

   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"
  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