gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2024 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 #ifndef GDB_FRAME_UNWIND_H
  21 #define GDB_FRAME_UNWIND_H
  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                                    const frame_info_ptr &this_frame,
  54                                    void **this_prologue_cache);
  55
  56 typedef unwind_stop_reason (frame_unwind_stop_reason_ftype)
  57   (const 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                            const 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 (const 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                                     const 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                                     const 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) (const 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 value *(frame_prev_register_ftype) (const frame_info_ptr &this_frame,
 144                                             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 gdbarch *(frame_prev_arch_ftype) (const frame_info_ptr &this_frame,
 157                                           void **this_prologue_cache);
 158
 159 /* Unwinders are classified by what part of GDB code created it.  */
 160 enum frame_unwind_class
 161 {
 162   /* This is mostly handled by core GDB code.  */
 163   FRAME_UNWIND_GDB,
 164   /* This unwinder was added by one of GDB's extension languages.  */
 165   FRAME_UNWIND_EXTENSION,
 166   /* The unwinder was created and mostly handles debug information.  */
 167   FRAME_UNWIND_DEBUGINFO,
 168   /* The unwinder was created and handles target dependent things.  */
 169   FRAME_UNWIND_ARCH,
 170   /* Meta enum value, to ensure we're always sent a valid unwinder class.  */
 171   UNWIND_CLASS_NUMBER,
 172 };
 173
 174 class frame_unwind
 175 {
 176 public:
 177   frame_unwind (const char *name, frame_type type, frame_unwind_class uclass,
 178                 const frame_data *data)
 179     : m_name (name), m_type (type), m_unwinder_class (uclass),
 180       m_unwind_data (data)
 181   { }
 182
 183   const char *name () const
 184   { return m_name; }
 185
 186   frame_type type () const
 187   { return m_type; }
 188
 189   frame_unwind_class unwinder_class () const
 190   { return m_unwinder_class; }
 191
 192   const frame_data *unwind_data () const
 193   { return m_unwind_data; }
 194
 195   bool enabled () const
 196   { return m_enabled; }
 197
 198   void set_enabled (bool state) const
 199   { m_enabled = state; }
 200
 201   /* Default stop_reason implementation.  It reports NO_REASON, unless the
 202      frame is the outermost.  */
 203
 204   virtual unwind_stop_reason stop_reason (const frame_info_ptr &this_frame,
 205                                           void **this_prologue_cache) const
 206   {
 207     return default_frame_unwind_stop_reason (this_frame, this_prologue_cache);
 208   }
 209
 210   /* Default frame sniffer.  Will always return that the unwinder
 211      is able to unwind the frame.  */
 212
 213   virtual int sniff (const frame_info_ptr &this_frame,
 214                      void **this_prologue_cache) const
 215   { return 1; }
 216
 217   /* Calculate the ID of the given frame using this unwinder.  */
 218
 219   virtual void this_id (const frame_info_ptr &this_frame,
 220                         void **this_prologue_cache,
 221                         struct frame_id *id) const = 0;
 222
 223   /* Get the value of a register in a previous frame.  */
 224
 225   virtual struct value *prev_register (const frame_info_ptr &this_frame,
 226                                        void **this_prologue_cache,
 227                                        int regnum) const = 0;
 228
 229   /* Properly deallocate the cache.  */
 230
 231   virtual void dealloc_cache (frame_info *self, void *this_cache) const
 232   { }
 233
 234   /* Get the previous architecture.  */
 235
 236   virtual gdbarch *prev_arch (const frame_info_ptr &this_frame,
 237                               void **this_prologue_cache) const
 238   { return get_frame_arch (this_frame); }
 239
 240 private:
 241
 242   /* Name of the unwinder.  Used to uniquely identify unwinders.  */
 243   const char *m_name;
 244
 245   /* The frame's type.  Should this instead be a collection of
 246      predicates that test the frame for various attributes?  */
 247   frame_type m_type;
 248
 249   /* What kind of unwinder is this.  It generally follows from where
 250      the unwinder was added or where it looks for information to do the
 251      unwinding.  */
 252   frame_unwind_class m_unwinder_class;
 253
 254   /* Additional data used by the trampoline and python frame unwinders.  */
 255   const frame_data *m_unwind_data;
 256
 257   /* Whether this unwinder can be used when sniffing.  */
 258   mutable bool m_enabled = true;
 259 };
 260
 261 /* This is a legacy version of the frame unwinder.  The original struct
 262    used function pointers for callbacks, this updated version has a
 263    method that just passes the parameters along to the callback
 264    pointer.
 265    Do not use this class for new unwinders.  Instead, see other classes
 266    that inherit from frame_unwind, such as the python unwinder.  */
 267 struct frame_unwind_legacy : public frame_unwind
 268 {
 269   frame_unwind_legacy (const char *name, frame_type type,
 270                        frame_unwind_class uclass,
 271                        frame_unwind_stop_reason_ftype *stop_reason_func,
 272                        frame_this_id_ftype *this_id_func,
 273                        frame_prev_register_ftype *prev_register_func,
 274                        const struct frame_data *data,
 275                        frame_sniffer_ftype *sniffer_func,
 276                        frame_dealloc_cache_ftype *dealloc_cache_func = nullptr,
 277                        frame_prev_arch_ftype *prev_arch_func = nullptr)
 278   : frame_unwind (name, type, uclass, data), m_stop_reason (stop_reason_func),
 279     m_this_id (this_id_func), m_prev_register (prev_register_func),
 280     m_sniffer (sniffer_func), m_dealloc_cache (dealloc_cache_func),
 281     m_prev_arch (prev_arch_func)
 282   { }
 283
 284   /* This method just passes the parameters to the callback pointer.  */
 285
 286   enum unwind_stop_reason stop_reason (const frame_info_ptr &this_frame,
 287                                        void **this_prologue_cache) const override;
 288
 289   /* This method just passes the parameters to the callback pointer.  */
 290
 291   void this_id (const frame_info_ptr &this_frame, void **this_prologue_cache,
 292                 struct frame_id *id) const override;
 293
 294   /* This method just passes the parameters to the callback pointer.  */
 295
 296   struct value *prev_register (const frame_info_ptr &this_frame,
 297                                void **this_prologue_cache,
 298                                int regnum) const override;
 299
 300   /* This method just passes the parameters to the callback pointer.  */
 301
 302   int sniff (const frame_info_ptr &this_frame,
 303              void **this_prologue_cache) const override;
 304
 305   /* This method just passes the parameters to the callback pointer.
 306      It is safe to call this method if no callback is installed, it
 307      just turns into a noop.  */
 308
 309   void dealloc_cache (frame_info *self, void *this_cache) const override;
 310
 311   /* This method just passes the parameters to the callback pointer.  */
 312
 313   struct gdbarch *prev_arch (const frame_info_ptr &this_frame,
 314                              void **this_prologue_cache) const override;
 315
 316 private:
 317
 318   frame_unwind_stop_reason_ftype *m_stop_reason;
 319   frame_this_id_ftype *m_this_id;
 320   frame_prev_register_ftype *m_prev_register;
 321   frame_sniffer_ftype *m_sniffer;
 322   frame_dealloc_cache_ftype *m_dealloc_cache;
 323   frame_prev_arch_ftype *m_prev_arch;
 324 };
 325
 326 /* Register a frame unwinder, _prepending_ it to the front of the
 327    search list (so it is sniffed before previously registered
 328    unwinders).  By using a prepend, later calls can install unwinders
 329    that override earlier calls.  This allows, for instance, an OSABI
 330    to install a more specific sigtramp unwinder that overrides the
 331    traditional brute-force unwinder.  */
 332 extern void frame_unwind_prepend_unwinder (struct gdbarch *,
 333                                            const struct frame_unwind *);
 334
 335 /* Add a frame sniffer to the list.  The predicates are polled in the
 336    order that they are appended.  The initial list contains the dummy
 337    frame sniffer.  */
 338
 339 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
 340                                           const struct frame_unwind *unwinder);
 341
 342 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 343    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 344    by this function.  Possibly initialize THIS_CACHE.  */
 345
 346 extern void frame_unwind_find_by_frame (const frame_info_ptr &this_frame,
 347                                         void **this_cache);
 348
 349 /* Helper functions for value-based register unwinding.  These return
 350    a (possibly lazy) value of the appropriate type.  */
 351
 352 /* Return a value which indicates that FRAME did not save REGNUM.  */
 353
 354 value *frame_unwind_got_optimized (const frame_info_ptr &frame, int regnum);
 355
 356 /* Return a value which indicates that FRAME copied REGNUM into
 357    register NEW_REGNUM.  */
 358
 359 value *frame_unwind_got_register (const frame_info_ptr &frame, int regnum,
 360                                   int new_regnum);
 361
 362 /* Return a value which indicates that FRAME saved REGNUM in memory at
 363    ADDR.  */
 364
 365 value *frame_unwind_got_memory (const frame_info_ptr &frame, int regnum,
 366                                 CORE_ADDR addr);
 367
 368 /* Return a value which indicates that FRAME's saved version of
 369    REGNUM has a known constant (computed) value of VAL.  */
 370
 371 value *frame_unwind_got_constant (const frame_info_ptr &frame, int regnum,
 372                                   ULONGEST val);
 373
 374 /* Return a value which indicates that FRAME's saved version of
 375    REGNUM has a known constant (computed) value which is stored
 376    inside BUF.  */
 377
 378 value *frame_unwind_got_bytes (const frame_info_ptr &frame, int regnum,
 379                                gdb::array_view<const gdb_byte> buf);
 380
 381 /* Return a value which indicates that FRAME's saved version of REGNUM
 382    has a known constant (computed) value of ADDR.  Convert the
 383    CORE_ADDR to a target address if necessary.  */
 384
 385 value *frame_unwind_got_address (const frame_info_ptr &frame, int regnum,
 386                                  CORE_ADDR addr);
 387
 388 #endif /* GDB_FRAME_UNWIND_H */