gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003, 2004, 2007, 2008, 2009, 2010, 2011
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #if !defined (FRAME_UNWIND_H)
  22 #define FRAME_UNWIND_H 1
  23
  24 struct frame_data;
  25 struct frame_info;
  26 struct frame_id;
  27 struct frame_unwind;
  28 struct gdbarch;
  29 struct regcache;
  30 struct value;
  31
  32 #include "frame.h"              /* For enum frame_type.  */
  33
  34 /* The following unwind functions assume a chain of frames forming the
  35    sequence: (outer) prev <-> this <-> next (inner).  All the
  36    functions are called with this frame's `struct frame_info' and
  37    prologue cache.
  38
  39    THIS frame's register values can be obtained by unwinding NEXT
  40    frame's registers (a recursive operation).
  41
  42    THIS frame's prologue cache can be used to cache information such
  43    as where this frame's prologue stores the previous frame's
  44    registers.  */
  45
  46 /* Given THIS frame, take a whiff of its registers (namely
  47    the PC and attributes) and if SELF is the applicable unwinder,
  48    return non-zero.  Possibly also initialize THIS_PROLOGUE_CACHE.  */
  49
  50 typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
  51                                    struct frame_info *this_frame,
  52                                    void **this_prologue_cache);
  53
  54 /* A default frame sniffer which always accepts the frame.  Used by
  55    fallback prologue unwinders.  */
  56
  57 int default_frame_sniffer (const struct frame_unwind *self,
  58                            struct frame_info *this_frame,
  59                            void **this_prologue_cache);
  60
  61 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  62    use THIS frame, and through it the NEXT frame's register unwind
  63    method, to determine the frame ID of THIS frame.
  64
  65    A frame ID provides an invariant that can be used to re-identify an
  66    instance of a frame.  It is a combination of the frame's `base' and
  67    the frame's function's code address.
  68
  69    Traditionally, THIS frame's ID was determined by examining THIS
  70    frame's function's prologue, and identifying the register/offset
  71    used as THIS frame's base.
  72
  73    Example: An examination of THIS frame's prologue reveals that, on
  74    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  75    (decrementing the SP by 12).  Consequently, the frame ID's base can
  76    be determined by adding 12 to the THIS frame's stack-pointer, and
  77    the value of THIS frame's SP can be obtained by unwinding the NEXT
  78    frame's SP.
  79
  80    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
  81    with the other unwind methods.  Memory for that cache should be
  82    allocated using FRAME_OBSTACK_ZALLOC().  */
  83
  84 typedef void (frame_this_id_ftype) (struct frame_info *this_frame,
  85                                     void **this_prologue_cache,
  86                                     struct frame_id *this_id);
  87
  88 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  89    use THIS frame, and implicitly the NEXT frame's register unwind
  90    method, to unwind THIS frame's registers (returning the value of
  91    the specified register REGNUM in the previous frame).
  92
  93    Traditionally, THIS frame's registers were unwound by examining
  94    THIS frame's function's prologue and identifying which registers
  95    that prolog code saved on the stack.
  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 value of the PC
 100    register in the previous frame is found in memory at SP+12, and
 101    THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
 102
 103    This function takes THIS_FRAME as an argument.  It can find the
 104    values of registers in THIS frame by calling get_frame_register
 105    (THIS_FRAME), and reinvoke itself to find other registers in the
 106    PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
 107
 108    The result is a GDB value object describing the register value.  It
 109    may be a lazy reference to memory, a lazy reference to the value of
 110    a register in THIS frame, or a non-lvalue.
 111
 112    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
 113    with the other unwind methods.  Memory for that cache should be
 114    allocated using FRAME_OBSTACK_ZALLOC().  */
 115
 116 typedef struct value * (frame_prev_register_ftype)
 117   (struct frame_info *this_frame, void **this_prologue_cache,
 118    int regnum);
 119
 120 /* Deallocate extra memory associated with the frame cache if any.  */
 121
 122 typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
 123                                           void *this_cache);
 124
 125 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
 126    use THIS frame, and implicitly the NEXT frame's register unwind
 127    method, return PREV frame's architecture.  */
 128
 129 typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame,
 130                                                  void **this_prologue_cache);
 131
 132 struct frame_unwind
 133 {
 134   /* The frame's type.  Should this instead be a collection of
 135      predicates that test the frame for various attributes?  */
 136   enum frame_type type;
 137   /* Should an attribute indicating the frame's address-in-block go
 138      here?  */
 139   frame_this_id_ftype *this_id;
 140   frame_prev_register_ftype *prev_register;
 141   const struct frame_data *unwind_data;
 142   frame_sniffer_ftype *sniffer;
 143   frame_dealloc_cache_ftype *dealloc_cache;
 144   frame_prev_arch_ftype *prev_arch;
 145 };
 146
 147 /* Register a frame unwinder, _prepending_ it to the front of the
 148    search list (so it is sniffed before previously registered
 149    unwinders).  By using a prepend, later calls can install unwinders
 150    that override earlier calls.  This allows, for instance, an OSABI
 151    to install a a more specific sigtramp unwinder that overrides the
 152    traditional brute-force unwinder.  */
 153 extern void frame_unwind_prepend_unwinder (struct gdbarch *,
 154                                            const struct frame_unwind *);
 155
 156 /* Add a frame sniffer to the list.  The predicates are polled in the
 157    order that they are appended.  The initial list contains the dummy
 158    frame sniffer.  */
 159
 160 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
 161                                           const struct frame_unwind *unwinder);
 162
 163 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 164    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 165    by this function.  Possibly initialize THIS_CACHE.  */
 166
 167 extern void frame_unwind_find_by_frame (struct frame_info *this_frame,
 168                                         void **this_cache);
 169
 170 /* Helper functions for value-based register unwinding.  These return
 171    a (possibly lazy) value of the appropriate type.  */
 172
 173 /* Return a value which indicates that FRAME did not save REGNUM.  */
 174
 175 struct value *frame_unwind_got_optimized (struct frame_info *frame,
 176                                           int regnum);
 177
 178 /* Return a value which indicates that FRAME copied REGNUM into
 179    register NEW_REGNUM.  */
 180
 181 struct value *frame_unwind_got_register (struct frame_info *frame, int regnum,
 182                                          int new_regnum);
 183
 184 /* Return a value which indicates that FRAME saved REGNUM in memory at
 185    ADDR.  */
 186
 187 struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum,
 188                                        CORE_ADDR addr);
 189
 190 /* Return a value which indicates that FRAME's saved version of
 191    REGNUM has a known constant (computed) value of VAL.  */
 192
 193 struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum,
 194                                          ULONGEST val);
 195
 196 /* Return a value which indicates that FRAME's saved version of
 197    REGNUM has a known constant (computed) value which is stored
 198    inside BUF.  */
 199
 200 struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum,
 201                                       gdb_byte *buf);
 202
 203 /* Return a value which indicates that FRAME's saved version of REGNUM
 204    has a known constant (computed) value of ADDR.  Convert the
 205    CORE_ADDR to a target address if necessary.  */
 206
 207 struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,
 208                                         CORE_ADDR addr);
 209
 210 #endif