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