gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2021 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    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   (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
 149 typedef 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
 156 typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame,
 157                                                  void **this_prologue_cache);
 158
 159 struct 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.  */
 181 extern 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
 188 extern 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
 195 extern 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
 203 struct 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
 209 struct 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
 215 struct 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
 221 struct 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
 228 struct 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
 235 struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,
 236                                         CORE_ADDR addr);
 237
 238 #endif