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/* Definitions for a frame unwinder, for GDB, the GNU debugger.

   Copyright (C) 2003, 2004, 2007, 2008 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#if !defined (FRAME_UNWIND_H)

#define FRAME_UNWIND_H 1

struct frame_data;

struct frame_info;

struct frame_id;

struct frame_unwind;

struct gdbarch;

struct regcache;

#include "frame.h"              /* For enum frame_type.  */

/* The following unwind functions assume a chain of frames forming the

   sequence: (outer) prev <-> this <-> next (inner).  All the

   functions are called with called with the next frame's `struct

   frame_info' and and this frame's prologue cache.

   THIS frame's register values can be obtained by unwinding NEXT

   frame's registers (a recursive operation).

   THIS frame's prologue cache can be used to cache information such

   as where this frame's prologue stores the previous frame's

   registers.  */

/* Given the NEXT frame, take a wiff of THIS frame's registers (namely

   the PC and attributes) and if SELF is the applicable unwinder,

   return non-zero.  Possibly also initialize THIS_PROLOGUE_CACHE.  */

typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,

                                   struct frame_info *next_frame,

                                   void **this_prologue_cache);

/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);

   use the NEXT frame, and its register unwind method, to determine

   the frame ID of THIS frame.

   A frame ID provides an invariant that can be used to re-identify an

   instance of a frame.  It is a combination of the frame's `base' and

   the frame's function's code address.

   Traditionally, THIS frame's ID was determined by examining THIS

   frame's function's prologue, and identifying the register/offset

   used as THIS frame's base.

   Example: An examination of THIS frame's prologue reveals that, on

   entry, it saves the PC(+12), SP(+8), and R1(+4) registers

   (decrementing the SP by 12).  Consequently, the frame ID's base can

   be determined by adding 12 to the THIS frame's stack-pointer, and

   the value of THIS frame's SP can be obtained by unwinding the NEXT

   frame's SP.

   THIS_PROLOGUE_CACHE can be used to share any prolog analysis data

   with the other unwind methods.  Memory for that cache should be

   allocated using FRAME_OBSTACK_ZALLOC().  */

typedef void (frame_this_id_ftype) (struct frame_info *next_frame,

                                    void **this_prologue_cache,

                                    struct frame_id *this_id);

/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);

   use the NEXT frame, and its register unwind method, to unwind THIS

   frame's registers (returning the value of the specified register

   REGNUM in the previous frame).

   Traditionally, THIS frame's registers were unwound by examining

   THIS frame's function's prologue and identifying which registers

   that prolog code saved on the stack.

   Example: An examination of THIS frame's prologue reveals that, on

   entry, it saves the PC(+12), SP(+8), and R1(+4) registers

   (decrementing the SP by 12).  Consequently, the value of the PC

   register in the previous frame is found in memory at SP+12, and

   THIS frame's SP can be obtained by unwinding the NEXT frame's SP.

   Why not pass in THIS_FRAME?  By passing in NEXT frame and THIS

   cache, the supplied parameters are consistent with the sibling

   function THIS_ID.

   Can the code call ``frame_register (get_prev_frame (NEXT_FRAME))''?

   Won't the call frame_register (THIS_FRAME) be faster?  Well,

   ignoring the possability that the previous frame does not yet

   exist, the ``frame_register (FRAME)'' function is expanded to

   ``frame_register_unwind (get_next_frame (FRAME)'' and hence that

   call will expand to ``frame_register_unwind (get_next_frame

   (get_prev_frame (NEXT_FRAME)))''.  Might as well call

   ``frame_register_unwind (NEXT_FRAME)'' directly.

   THIS_PROLOGUE_CACHE can be used to share any prolog analysis data

   with the other unwind methods.  Memory for that cache should be

   allocated using FRAME_OBSTACK_ZALLOC().  */

typedef void (frame_prev_register_ftype) (struct frame_info *next_frame,

                                          void **this_prologue_cache,

                                          int prev_regnum,

                                          int *optimized,

                                          enum lval_type * lvalp,

                                          CORE_ADDR *addrp,

                                          int *realnump, gdb_byte *valuep);

/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);

   use the NEXT frame, and its register unwind method, to return the PREV

   frame's program-counter.  */

typedef CORE_ADDR (frame_prev_pc_ftype) (struct frame_info *next_frame,

                                         void **this_prologue_cache);

/* Deallocate extra memory associated with the frame cache if any.  */

typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,

                                          void *this_cache);

struct frame_unwind

{

  /* The frame's type.  Should this instead be a collection of

     predicates that test the frame for various attributes?  */

  enum frame_type type;

  /* Should an attribute indicating the frame's address-in-block go

     here?  */

  frame_this_id_ftype *this_id;

  frame_prev_register_ftype *prev_register;

  const struct frame_data *unwind_data;

  frame_sniffer_ftype *sniffer;

  frame_prev_pc_ftype *prev_pc;

  frame_dealloc_cache_ftype *dealloc_cache;

};

/* Register a frame unwinder, _prepending_ it to the front of the

   search list (so it is sniffed before previously registered

   unwinders).  By using a prepend, later calls can install unwinders

   that override earlier calls.  This allows, for instance, an OSABI

   to install a a more specific sigtramp unwinder that overrides the

   traditional brute-force unwinder.  */

extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,

                                           const struct frame_unwind *unwinder);

/* Given the NEXT frame, take a wiff of THIS frame's registers (namely

   the PC and attributes) and if it is the applicable unwinder return

   the unwind methods, or NULL if it is not.  */

typedef const struct frame_unwind *(frame_unwind_sniffer_ftype) (struct frame_info *next_frame);

/* Add a frame sniffer to the list.  The predicates are polled in the

   order that they are appended.  The initial list contains the dummy

   frame sniffer.  */

extern void frame_unwind_append_sniffer (struct gdbarch *gdbarch,

                                         frame_unwind_sniffer_ftype *sniffer);

/* Iterate through the next frame's sniffers until one returns with an

   unwinder implementation.  Possibly initialize THIS_CACHE.  */

extern const struct frame_unwind *frame_unwind_find_by_frame (struct frame_info *next_frame,

                                                              void **this_cache);

#endif