gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003, 2004, 2007, 2008 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 the next frame's `struct frame_info'
  36    and this frame's 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 /* A default frame sniffer which always accepts the frame.  Used by
  54    fallback prologue unwinders.  */
  55
  56 int default_frame_sniffer (const struct frame_unwind *self,
  57                            struct frame_info *this_frame,
  58                            void **this_prologue_cache);
  59
  60 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  61    use THIS frame, and through it the NEXT frame's register unwind
  62    method, to determine the frame ID of THIS frame.
  63
  64    A frame ID provides an invariant that can be used to re-identify an
  65    instance of a frame.  It is a combination of the frame's `base' and
  66    the frame's function's code address.
  67
  68    Traditionally, THIS frame's ID was determined by examining THIS
  69    frame's function's prologue, and identifying the register/offset
  70    used as THIS frame's base.
  71
  72    Example: An examination of THIS frame's prologue reveals that, on
  73    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  74    (decrementing the SP by 12).  Consequently, the frame ID's base can
  75    be determined by adding 12 to the THIS frame's stack-pointer, and
  76    the value of THIS frame's SP can be obtained by unwinding the NEXT
  77    frame's SP.
  78
  79    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
  80    with the other unwind methods.  Memory for that cache should be
  81    allocated using FRAME_OBSTACK_ZALLOC().  */
  82
  83 typedef void (frame_this_id_ftype) (struct frame_info *this_frame,
  84                                     void **this_prologue_cache,
  85                                     struct frame_id *this_id);
  86
  87 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  88    use THIS frame, and implicitly the NEXT frame's register unwind
  89    method, to unwind THIS frame's registers (returning the value of
  90    the specified register REGNUM in the previous frame).
  91
  92    Traditionally, THIS frame's registers were unwound by examining
  93    THIS frame's function's prologue and identifying which registers
  94    that prolog code saved on the stack.
  95
  96    Example: An examination of THIS frame's prologue reveals that, on
  97    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  98    (decrementing the SP by 12).  Consequently, the value of the PC
  99    register in the previous frame is found in memory at SP+12, and
 100    THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
 101
 102    This function takes THIS_FRAME as an argument.  It can find the
 103    values of registers in THIS frame by calling get_frame_register
 104    (THIS_FRAME), and reinvoke itself to find other registers in the
 105    PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
 106
 107    The result is a GDB value object describing the register value.  It
 108    may be a lazy reference to memory, a lazy reference to the value of
 109    a register in THIS frame, or a non-lvalue.
 110
 111    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
 112    with the other unwind methods.  Memory for that cache should be
 113    allocated using FRAME_OBSTACK_ZALLOC().  */
 114
 115 typedef struct value * (frame_prev_register_ftype)
 116   (struct frame_info *this_frame, void **this_prologue_cache,
 117    int regnum);
 118
 119 /* Deallocate extra memory associated with the frame cache if any.  */
 120
 121 typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
 122                                           void *this_cache);
 123
 124 struct frame_unwind
 125 {
 126   /* The frame's type.  Should this instead be a collection of
 127      predicates that test the frame for various attributes?  */
 128   enum frame_type type;
 129   /* Should an attribute indicating the frame's address-in-block go
 130      here?  */
 131   frame_this_id_ftype *this_id;
 132   frame_prev_register_ftype *prev_register;
 133   const struct frame_data *unwind_data;
 134   frame_sniffer_ftype *sniffer;
 135   frame_dealloc_cache_ftype *dealloc_cache;
 136 };
 137
 138 /* Register a frame unwinder, _prepending_ it to the front of the
 139    search list (so it is sniffed before previously registered
 140    unwinders).  By using a prepend, later calls can install unwinders
 141    that override earlier calls.  This allows, for instance, an OSABI
 142    to install a a more specific sigtramp unwinder that overrides the
 143    traditional brute-force unwinder.  */
 144 extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
 145                                            const struct frame_unwind *unwinder);
 146
 147 /* Add a frame sniffer to the list.  The predicates are polled in the
 148    order that they are appended.  The initial list contains the dummy
 149    frame sniffer.  */
 150
 151 extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
 152                                           const struct frame_unwind *unwinder);
 153
 154 /* Iterate through sniffers for THIS frame until one returns with an
 155    unwinder implementation.  Possibly initialize THIS_CACHE.  */
 156
 157 extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *this_frame,
 158                                                               void **this_cache);
 159
 160 /* Helper functions for value-based register unwinding.  These return
 161    a (possibly lazy) value of the appropriate type.  */
 162
 163 /* Return a value which indicates that FRAME did not save REGNUM.  */
 164
 165 struct value *frame_unwind_got_optimized (struct frame_info *frame,
 166                                           int regnum);
 167
 168 /* Return a value which indicates that FRAME copied REGNUM into
 169    register NEW_REGNUM.  */
 170
 171 struct value *frame_unwind_got_register (struct frame_info *frame, int regnum,
 172                                          int new_regnum);
 173
 174 /* Return a value which indicates that FRAME saved REGNUM in memory at
 175    ADDR.  */
 176
 177 struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum,
 178                                        CORE_ADDR addr);
 179
 180 /* Return a value which indicates that FRAME's saved version of
 181    REGNUM has a known constant (computed) value of VAL.  */
 182
 183 struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum,
 184                                          ULONGEST val);
 185
 186 /* Return a value which indicates that FRAME's saved version of
 187    REGNUM has a known constant (computed) value which is stored
 188    inside BUF.  */
 189
 190 struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum,
 191                                       gdb_byte *buf);
 192
 193 /* Return a value which indicates that FRAME's saved version of REGNUM
 194    has a known constant (computed) value of ADDR.  Convert the
 195    CORE_ADDR to a target address if necessary.  */
 196
 197 struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,
 198                                         CORE_ADDR addr);
 199
 200 #endif