gdb/frame-unwind.h

   1 /* Definitions for a frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003, 2004, 2007 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
  30 #include "frame.h"              /* For enum frame_type.  */
  31
  32 /* The following unwind functions assume a chain of frames forming the
  33    sequence: (outer) prev <-> this <-> next (inner).  All the
  34    functions are called with called with the next frame's `struct
  35    frame_info' and and this frame's prologue cache.
  36
  37    THIS frame's register values can be obtained by unwinding NEXT
  38    frame's registers (a recursive operation).
  39
  40    THIS frame's prologue cache can be used to cache information such
  41    as where this frame's prologue stores the previous frame's
  42    registers.  */
  43
  44 /* Given the NEXT frame, take a wiff of THIS frame's registers (namely
  45    the PC and attributes) and if SELF is the applicable unwinder,
  46    return non-zero.  Possibly also initialize THIS_PROLOGUE_CACHE.  */
  47
  48 typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
  49                                    struct frame_info *next_frame,
  50                                    void **this_prologue_cache);
  51
  52 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  53    use the NEXT frame, and its register unwind method, to determine
  54    the frame ID of THIS frame.
  55
  56    A frame ID provides an invariant that can be used to re-identify an
  57    instance of a frame.  It is a combination of the frame's `base' and
  58    the frame's function's code address.
  59
  60    Traditionally, THIS frame's ID was determined by examining THIS
  61    frame's function's prologue, and identifying the register/offset
  62    used as THIS frame's base.
  63
  64    Example: An examination of THIS frame's prologue reveals that, on
  65    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  66    (decrementing the SP by 12).  Consequently, the frame ID's base can
  67    be determined by adding 12 to the THIS frame's stack-pointer, and
  68    the value of THIS frame's SP can be obtained by unwinding the NEXT
  69    frame's SP.
  70
  71    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
  72    with the other unwind methods.  Memory for that cache should be
  73    allocated using FRAME_OBSTACK_ZALLOC().  */
  74
  75 typedef void (frame_this_id_ftype) (struct frame_info *next_frame,
  76                                     void **this_prologue_cache,
  77                                     struct frame_id *this_id);
  78
  79 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
  80    use the NEXT frame, and its register unwind method, to unwind THIS
  81    frame's registers (returning the value of the specified register
  82    REGNUM in the previous frame).
  83
  84    Traditionally, THIS frame's registers were unwound by examining
  85    THIS frame's function's prologue and identifying which registers
  86    that prolog code saved on the stack.
  87
  88    Example: An examination of THIS frame's prologue reveals that, on
  89    entry, it saves the PC(+12), SP(+8), and R1(+4) registers
  90    (decrementing the SP by 12).  Consequently, the value of the PC
  91    register in the previous frame is found in memory at SP+12, and
  92    THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
  93
  94    Why not pass in THIS_FRAME?  By passing in NEXT frame and THIS
  95    cache, the supplied parameters are consistent with the sibling
  96    function THIS_ID.
  97
  98    Can the code call ``frame_register (get_prev_frame (NEXT_FRAME))''?
  99    Won't the call frame_register (THIS_FRAME) be faster?  Well,
 100    ignoring the possability that the previous frame does not yet
 101    exist, the ``frame_register (FRAME)'' function is expanded to
 102    ``frame_register_unwind (get_next_frame (FRAME)'' and hence that
 103    call will expand to ``frame_register_unwind (get_next_frame
 104    (get_prev_frame (NEXT_FRAME)))''.  Might as well call
 105    ``frame_register_unwind (NEXT_FRAME)'' directly.
 106
 107    THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
 108    with the other unwind methods.  Memory for that cache should be
 109    allocated using FRAME_OBSTACK_ZALLOC().  */
 110
 111 typedef void (frame_prev_register_ftype) (struct frame_info *next_frame,
 112                                           void **this_prologue_cache,
 113                                           int prev_regnum,
 114                                           int *optimized,
 115                                           enum lval_type * lvalp,
 116                                           CORE_ADDR *addrp,
 117                                           int *realnump, gdb_byte *valuep);
 118
 119 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
 120    use the NEXT frame, and its register unwind method, to return the PREV
 121    frame's program-counter.  */
 122
 123 typedef CORE_ADDR (frame_prev_pc_ftype) (struct frame_info *next_frame,
 124                                          void **this_prologue_cache);
 125
 126 /* Deallocate extra memory associated with the frame cache if any.  */
 127
 128 typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
 129                                           void *this_cache);
 130
 131 struct frame_unwind
 132 {
 133   /* The frame's type.  Should this instead be a collection of
 134      predicates that test the frame for various attributes?  */
 135   enum frame_type type;
 136   /* Should an attribute indicating the frame's address-in-block go
 137      here?  */
 138   frame_this_id_ftype *this_id;
 139   frame_prev_register_ftype *prev_register;
 140   const struct frame_data *unwind_data;
 141   frame_sniffer_ftype *sniffer;
 142   frame_prev_pc_ftype *prev_pc;
 143   frame_dealloc_cache_ftype *dealloc_cache;
 144 };
 145
 146 /* Register a frame unwinder, _prepending_ it to the front of the
 147    search list (so it is sniffed before previously registered
 148    unwinders).  By using a prepend, later calls can install unwinders
 149    that override earlier calls.  This allows, for instance, an OSABI
 150    to install a a more specific sigtramp unwinder that overrides the
 151    traditional brute-force unwinder.  */
 152 extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
 153                                            const struct frame_unwind *unwinder);
 154
 155 /* Given the NEXT frame, take a wiff of THIS frame's registers (namely
 156    the PC and attributes) and if it is the applicable unwinder return
 157    the unwind methods, or NULL if it is not.  */
 158
 159 typedef const struct frame_unwind *(frame_unwind_sniffer_ftype) (struct frame_info *next_frame);
 160
 161 /* Add a frame sniffer to the list.  The predicates are polled in the
 162    order that they are appended.  The initial list contains the dummy
 163    frame sniffer.  */
 164
 165 extern void frame_unwind_append_sniffer (struct gdbarch *gdbarch,
 166                                          frame_unwind_sniffer_ftype *sniffer);
 167
 168 /* Iterate through the next frame's sniffers until one returns with an
 169    unwinder implementation.  Possibly initialize THIS_CACHE.  */
 170
 171 extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *next_frame,
 172                                                               void **this_cache);
 173
 174 #endif