gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2004, 2007-2012 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.  */
  48
  49 typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
  50                                    struct frame_info *this_frame,
  51                                    void **this_prologue_cache);
  52
  53 typedef enum unwind_stop_reason (frame_unwind_stop_reason_ftype)
  54   (struct frame_info *this_frame, void **this_prologue_cache);
  55
  56 /* A default frame sniffer which always accepts the frame.  Used by
  57    fallback prologue unwinders.  */
  58
  59 int default_frame_sniffer (const struct frame_unwind *self,
  60                            struct frame_info *this_frame,
  61                            void **this_prologue_cache);
  62
  63 /* A default stop_reason callback which always claims the frame is
  64    unwindable.  */
  65
  66 enum unwind_stop_reason
  67   default_frame_unwind_stop_reason (struct frame_info *this_frame,
  68                                     void **this_cache);
  69
  70 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  71    use THIS frame, and through it the NEXT frame's register unwind
  72    method, to determine the frame ID of THIS frame.
  73
  74    A frame ID provides an invariant that can be used to re-identify an
  75    instance of a frame.  It is a combination of the frame's `base' and
  76    the frame's function's code address.
  77
  78    Traditionally, THIS frame's ID was determined by examining THIS
  79    frame's function's prologue, and identifying the register/offset
  80    used as THIS frame's base.
  81
  82    Example: An examination of THIS frame's prologue reveals that, on
  83    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  84    (decrementing the SP by 12).  Consequently, the frame ID's base can
  85    be determined by adding 12 to the THIS frame's stack-pointer, and
  86    the value of THIS frame's SP can be obtained by unwinding the NEXT
  87    frame's SP.
  88
  89    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
  90    with the other unwind methods.  Memory for that cache should be
  91    allocated using FRAME_OBSTACK_ZALLOC().  */
  92
  93 typedef void (frame_this_id_ftype) (struct frame_info *this_frame,
  94                                     void **this_prologue_cache,
  95                                     struct frame_id *this_id);
  96
  97 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  98    use THIS frame, and implicitly the NEXT frame's register unwind
  99    method, to unwind THIS frame's registers (returning the value of
 100    the specified register REGNUM in the previous frame).
 101
 102    Traditionally, THIS frame's registers were unwound by examining
 103    THIS frame's function's prologue and identifying which registers
 104    that prolog code saved on the stack.
 105
 106    Example: An examination of THIS frame's prologue reveals that, on
 107    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
 108    (decrementing the SP by 12).  Consequently, the value of the PC
 109    register in the previous frame is found in memory at SP+12, and
 110    THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
 111
 112    This function takes THIS_FRAME as an argument.  It can find the
 113    values of registers in THIS frame by calling get_frame_register
 114    (THIS_FRAME), and reinvoke itself to find other registers in the
 115    PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
 116
 117    The result is a GDB value object describing the register value.  It
 118    may be a lazy reference to memory, a lazy reference to the value of
 119    a register in THIS frame, or a non-lvalue.
 120
 121    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
 122    with the other unwind methods.  Memory for that cache should be
 123    allocated using FRAME_OBSTACK_ZALLOC().  */
 124
 125 typedef struct value * (frame_prev_register_ftype)
 126   (struct frame_info *this_frame, void **this_prologue_cache,
 127    int regnum);
 128
 129 /* Deallocate extra memory associated with the frame cache if any.  */
 130
 131 typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
 132                                           void *this_cache);
 133
 134 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
 135    use THIS frame, and implicitly the NEXT frame's register unwind
 136    method, return PREV frame's architecture.  */
 137
 138 typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame,
 139                                                  void **this_prologue_cache);
 140
 141 struct frame_unwind
 142 {
 143   /* The frame's type.  Should this instead be a collection of
 144      predicates that test the frame for various attributes?  */
 145   enum frame_type type;
 146   /* Should an attribute indicating the frame's address-in-block go
 147      here?  */
 148   frame_unwind_stop_reason_ftype *stop_reason;
 149   frame_this_id_ftype *this_id;
 150   frame_prev_register_ftype *prev_register;
 151   const struct frame_data *unwind_data;
 152   frame_sniffer_ftype *sniffer;
 153   frame_dealloc_cache_ftype *dealloc_cache;
 154   frame_prev_arch_ftype *prev_arch;
 155 };
 156
 157 /* Register a frame unwinder, _prepending_ it to the front of the
 158    search list (so it is sniffed before previously registered
 159    unwinders).  By using a prepend, later calls can install unwinders
 160    that override earlier calls.  This allows, for instance, an OSABI
 161    to install a more specific sigtramp unwinder that overrides the
 162    traditional brute-force unwinder.  */
 163 extern void frame_unwind_prepend_unwinder (struct gdbarch *,
 164                                            const struct frame_unwind *);
 165
 166 /* Add a frame sniffer to the list.  The predicates are polled in the
 167    order that they are appended.  The initial list contains the dummy
 168    frame sniffer.  */
 169
 170 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
 171                                           const struct frame_unwind *unwinder);
 172
 173 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 174    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 175    by this function.  Possibly initialize THIS_CACHE.  */
 176
 177 extern void frame_unwind_find_by_frame (struct frame_info *this_frame,
 178                                         void **this_cache);
 179
 180 /* Helper functions for value-based register unwinding.  These return
 181    a (possibly lazy) value of the appropriate type.  */
 182
 183 /* Return a value which indicates that FRAME did not save REGNUM.  */
 184
 185 struct value *frame_unwind_got_optimized (struct frame_info *frame,
 186                                           int regnum);
 187
 188 /* Return a value which indicates that FRAME copied REGNUM into
 189    register NEW_REGNUM.  */
 190
 191 struct value *frame_unwind_got_register (struct frame_info *frame, int regnum,
 192                                          int new_regnum);
 193
 194 /* Return a value which indicates that FRAME saved REGNUM in memory at
 195    ADDR.  */
 196
 197 struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum,
 198                                        CORE_ADDR addr);
 199
 200 /* Return a value which indicates that FRAME's saved version of
 201    REGNUM has a known constant (computed) value of VAL.  */
 202
 203 struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum,
 204                                          ULONGEST val);
 205
 206 /* Return a value which indicates that FRAME's saved version of
 207    REGNUM has a known constant (computed) value which is stored
 208    inside BUF.  */
 209
 210 struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum,
 211                                       gdb_byte *buf);
 212
 213 /* Return a value which indicates that FRAME's saved version of REGNUM
 214    has a known constant (computed) value of ADDR.  Convert the
 215    CORE_ADDR to a target address if necessary.  */
 216
 217 struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,
 218                                         CORE_ADDR addr);
 219
 220 #endif