gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright 2003, 2004 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 2 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, write to the Free Software
  19    Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #if !defined (FRAME_UNWIND_H)
  23 #define FRAME_UNWIND_H 1
  24
  25 struct frame_data;
  26 struct frame_info;
  27 struct frame_id;
  28 struct frame_unwind;
  29 struct gdbarch;
  30 struct regcache;
  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 called with the next frame's `struct
  37    frame_info' and and this frame's 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 the NEXT frame, take a wiff of THIS frame's 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 *next_frame,
  52                                    void **this_prologue_cache);
  53
  54 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  55    use the NEXT frame, and its register unwind method, to determine
  56    the frame ID of THIS frame.
  57
  58    A frame ID provides an invariant that can be used to re-identify an
  59    instance of a frame.  It is a combination of the frame's `base' and
  60    the frame's function's code address.
  61
  62    Traditionally, THIS frame's ID was determined by examining THIS
  63    frame's function's prologue, and identifying the register/offset
  64    used as THIS frame's base.
  65
  66    Example: An examination of THIS frame's prologue reveals that, on
  67    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  68    (decrementing the SP by 12).  Consequently, the frame ID's base can
  69    be determined by adding 12 to the THIS frame's stack-pointer, and
  70    the value of THIS frame's SP can be obtained by unwinding the NEXT
  71    frame's SP.
  72
  73    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
  74    with the other unwind methods.  Memory for that cache should be
  75    allocated using frame_obstack_zalloc().  */
  76
  77 typedef void (frame_this_id_ftype) (struct frame_info *next_frame,
  78                                     void **this_prologue_cache,
  79                                     struct frame_id *this_id);
  80
  81 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  82    use the NEXT frame, and its register unwind method, to unwind THIS
  83    frame's registers (returning the value of the specified register
  84    REGNUM in the previous frame).
  85
  86    Traditionally, THIS frame's registers were unwound by examining
  87    THIS frame's function's prologue and identifying which registers
  88    that prolog code saved on the stack.
  89
  90    Example: An examination of THIS frame's prologue reveals that, on
  91    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  92    (decrementing the SP by 12).  Consequently, the value of the PC
  93    register in the previous frame is found in memory at SP+12, and
  94    THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
  95
  96    Why not pass in THIS_FRAME?  By passing in NEXT frame and THIS
  97    cache, the supplied parameters are consistent with the sibling
  98    function THIS_ID.
  99
 100    Can the code call ``frame_register (get_prev_frame (NEXT_FRAME))''?
 101    Won't the call frame_register (THIS_FRAME) be faster?  Well,
 102    ignoring the possability that the previous frame does not yet
 103    exist, the ``frame_register (FRAME)'' function is expanded to
 104    ``frame_register_unwind (get_next_frame (FRAME)'' and hence that
 105    call will expand to ``frame_register_unwind (get_next_frame
 106    (get_prev_frame (NEXT_FRAME)))''.  Might as well call
 107    ``frame_register_unwind (NEXT_FRAME)'' directly.
 108
 109    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
 110    with the other unwind methods.  Memory for that cache should be
 111    allocated using frame_obstack_zalloc().  */
 112
 113 typedef void (frame_prev_register_ftype) (struct frame_info *next_frame,
 114                                           void **this_prologue_cache,
 115                                           int prev_regnum,
 116                                           int *optimized,
 117                                           enum lval_type * lvalp,
 118                                           CORE_ADDR *addrp,
 119                                           int *realnump, gdb_byte *valuep);
 120
 121 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
 122    use the NEXT frame, and its register unwind method, to return the PREV
 123    frame's program-counter.  */
 124
 125 typedef CORE_ADDR (frame_prev_pc_ftype) (struct frame_info *next_frame,
 126                                          void **this_prologue_cache);
 127
 128
 129 struct frame_unwind
 130 {
 131   /* The frame's type.  Should this instead be a collection of
 132      predicates that test the frame for various attributes?  */
 133   enum frame_type type;
 134   /* Should an attribute indicating the frame's address-in-block go
 135      here?  */
 136   frame_this_id_ftype *this_id;
 137   frame_prev_register_ftype *prev_register;
 138   const struct frame_data *unwind_data;
 139   frame_sniffer_ftype *sniffer;
 140   frame_prev_pc_ftype *prev_pc;
 141 };
 142
 143 /* Register a frame unwinder, _prepending_ it to the front of the
 144    search list (so it is sniffed before previously registered
 145    unwinders).  By using a prepend, later calls can install unwinders
 146    that override earlier calls.  This allows, for instance, an OSABI
 147    to install a a more specific sigtramp unwinder that overrides the
 148    traditional brute-force unwinder.  */
 149 extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
 150                                            const struct frame_unwind *unwinder);
 151
 152 /* Given the NEXT frame, take a wiff of THIS frame's registers (namely
 153    the PC and attributes) and if it is the applicable unwinder return
 154    the unwind methods, or NULL if it is not.  */
 155
 156 typedef const struct frame_unwind *(frame_unwind_sniffer_ftype) (struct frame_info *next_frame);
 157
 158 /* Add a frame sniffer to the list.  The predicates are polled in the
 159    order that they are appended.  The initial list contains the dummy
 160    frame sniffer.  */
 161
 162 extern void frame_unwind_append_sniffer (struct gdbarch *gdbarch,
 163                                          frame_unwind_sniffer_ftype *sniffer);
 164
 165 /* Iterate through the next frame's sniffers until one returns with an
 166    unwinder implementation.  Possibly initialize THIS_CACHE.  */
 167
 168 extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *next_frame,
 169                                                               void **this_cache);
 170
 171 #endif