gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2018 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 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  74    use THIS frame, and through it the NEXT frame's register unwind
  75    method, to determine the frame ID of THIS frame.
  76
  77    A frame ID provides an invariant that can be used to re-identify an
  78    instance of a frame.  It is a combination of the frame's `base' and
  79    the frame's function's code address.
  80
  81    Traditionally, THIS frame's ID was determined by examining THIS
  82    frame's function's prologue, and identifying the register/offset
  83    used as THIS frame's base.
  84
  85    Example: An examination of THIS frame's prologue reveals that, on
  86    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  87    (decrementing the SP by 12).  Consequently, the frame ID's base can
  88    be determined by adding 12 to the THIS frame's stack-pointer, and
  89    the value of THIS frame's SP can be obtained by unwinding the NEXT
  90    frame's SP.
  91
  92    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
  93    with the other unwind methods.  Memory for that cache should be
  94    allocated using FRAME_OBSTACK_ZALLOC().  */
  95
  96 typedef void (frame_this_id_ftype) (struct frame_info *this_frame,
  97                                     void **this_prologue_cache,
  98                                     struct frame_id *this_id);
  99
 100 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
 101    use THIS frame, and implicitly the NEXT frame's register unwind
 102    method, to unwind THIS frame's registers (returning the value of
 103    the specified register REGNUM in the previous frame).
 104
 105    Traditionally, THIS frame's registers were unwound by examining
 106    THIS frame's function's prologue and identifying which registers
 107    that prolog code saved on the stack.
 108
 109    Example: An examination of THIS frame's prologue reveals that, on
 110    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
 111    (decrementing the SP by 12).  Consequently, the value of the PC
 112    register in the previous frame is found in memory at SP+12, and
 113    THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
 114
 115    This function takes THIS_FRAME as an argument.  It can find the
 116    values of registers in THIS frame by calling get_frame_register
 117    (THIS_FRAME), and reinvoke itself to find other registers in the
 118    PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
 119
 120    The result is a GDB value object describing the register value.  It
 121    may be a lazy reference to memory, a lazy reference to the value of
 122    a register in THIS frame, or a non-lvalue.
 123
 124    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
 125    with the other unwind methods.  Memory for that cache should be
 126    allocated using FRAME_OBSTACK_ZALLOC().  */
 127
 128 typedef struct value * (frame_prev_register_ftype)
 129   (struct frame_info *this_frame, void **this_prologue_cache,
 130    int regnum);
 131
 132 /* Deallocate extra memory associated with the frame cache if any.  */
 133
 134 typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
 135                                           void *this_cache);
 136
 137 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
 138    use THIS frame, and implicitly the NEXT frame's register unwind
 139    method, return PREV frame's architecture.  */
 140
 141 typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame,
 142                                                  void **this_prologue_cache);
 143
 144 struct frame_unwind
 145 {
 146   /* The frame's type.  Should this instead be a collection of
 147      predicates that test the frame for various attributes?  */
 148   enum frame_type type;
 149   /* Should an attribute indicating the frame's address-in-block go
 150      here?  */
 151   frame_unwind_stop_reason_ftype *stop_reason;
 152   frame_this_id_ftype *this_id;
 153   frame_prev_register_ftype *prev_register;
 154   const struct frame_data *unwind_data;
 155   frame_sniffer_ftype *sniffer;
 156   frame_dealloc_cache_ftype *dealloc_cache;
 157   frame_prev_arch_ftype *prev_arch;
 158 };
 159
 160 /* Register a frame unwinder, _prepending_ it to the front of the
 161    search list (so it is sniffed before previously registered
 162    unwinders).  By using a prepend, later calls can install unwinders
 163    that override earlier calls.  This allows, for instance, an OSABI
 164    to install a more specific sigtramp unwinder that overrides the
 165    traditional brute-force unwinder.  */
 166 extern void frame_unwind_prepend_unwinder (struct gdbarch *,
 167                                            const struct frame_unwind *);
 168
 169 /* Add a frame sniffer to the list.  The predicates are polled in the
 170    order that they are appended.  The initial list contains the dummy
 171    frame sniffer.  */
 172
 173 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
 174                                           const struct frame_unwind *unwinder);
 175
 176 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 177    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 178    by this function.  Possibly initialize THIS_CACHE.  */
 179
 180 extern void frame_unwind_find_by_frame (struct frame_info *this_frame,
 181                                         void **this_cache);
 182
 183 /* Helper functions for value-based register unwinding.  These return
 184    a (possibly lazy) value of the appropriate type.  */
 185
 186 /* Return a value which indicates that FRAME did not save REGNUM.  */
 187
 188 struct value *frame_unwind_got_optimized (struct frame_info *frame,
 189                                           int regnum);
 190
 191 /* Return a value which indicates that FRAME copied REGNUM into
 192    register NEW_REGNUM.  */
 193
 194 struct value *frame_unwind_got_register (struct frame_info *frame, int regnum,
 195                                          int new_regnum);
 196
 197 /* Return a value which indicates that FRAME saved REGNUM in memory at
 198    ADDR.  */
 199
 200 struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum,
 201                                        CORE_ADDR addr);
 202
 203 /* Return a value which indicates that FRAME's saved version of
 204    REGNUM has a known constant (computed) value of VAL.  */
 205
 206 struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum,
 207                                          ULONGEST val);
 208
 209 /* Return a value which indicates that FRAME's saved version of
 210    REGNUM has a known constant (computed) value which is stored
 211    inside BUF.  */
 212
 213 struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum,
 214                                       gdb_byte *buf);
 215
 216 /* Return a value which indicates that FRAME's saved version of REGNUM
 217    has a known constant (computed) value of ADDR.  Convert the
 218    CORE_ADDR to a target address if necessary.  */
 219
 220 struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,
 221                                         CORE_ADDR addr);
 222
 223 #endif