text: /* Definitions for a frame unwinder, for GDB, the GNU debugger.
  
     Copyright (C) 2003-2015 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;
  struct value;
  
  #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 this frame's `struct frame_info' and
     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 THIS frame, take a whiff of its registers (namely
     the PC and attributes) and if SELF is the applicable unwinder,
     return non-zero.  Possibly also initialize THIS_PROLOGUE_CACHE; but
     only if returning 1.  Initializing THIS_PROLOGUE_CACHE in other
     cases (0 return, or exception) is invalid.  */
  
  typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
  				   struct frame_info *this_frame,
  				   void **this_prologue_cache);
  
  typedef enum unwind_stop_reason (frame_unwind_stop_reason_ftype)
    (struct frame_info *this_frame, void **this_prologue_cache);
  
  /* A default frame sniffer which always accepts the frame.  Used by
     fallback prologue unwinders.  */
  
  int default_frame_sniffer (const struct frame_unwind *self,
  			   struct frame_info *this_frame,
  			   void **this_prologue_cache);
  
  /* A default stop_reason callback which always claims the frame is
     unwindable.  */
  
  enum unwind_stop_reason
    default_frame_unwind_stop_reason (struct frame_info *this_frame,
  				    void **this_cache);
  
  /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
     use THIS frame, and through it the NEXT frame's 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 *this_frame,
  				    void **this_prologue_cache,
  				    struct frame_id *this_id);
  
  /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
     use THIS frame, and implicitly the NEXT frame's 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.
  
     This function takes THIS_FRAME as an argument.  It can find the
     values of registers in THIS frame by calling get_frame_register
     (THIS_FRAME), and reinvoke itself to find other registers in the
     PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
  
     The result is a GDB value object describing the register value.  It
     may be a lazy reference to memory, a lazy reference to the value of
     a register in THIS frame, or a non-lvalue.
  
     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 struct value * (frame_prev_register_ftype)
    (struct frame_info *this_frame, void **this_prologue_cache,
     int regnum);
  
  /* Deallocate extra memory associated with the frame cache if any.  */
  
  typedef void (frame_dealloc_cache_ftype) (struct frame_info *self,
  					  void *this_cache);
  
  /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
     use THIS frame, and implicitly the NEXT frame's register unwind
     method, return PREV frame's architecture.  */
  
  typedef struct gdbarch *(frame_prev_arch_ftype) (struct frame_info *this_frame,
  						 void **this_prologue_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_unwind_stop_reason_ftype *stop_reason;
    frame_this_id_ftype *this_id;
    frame_prev_register_ftype *prev_register;
    const struct frame_data *unwind_data;
    frame_sniffer_ftype *sniffer;
    frame_dealloc_cache_ftype *dealloc_cache;
    frame_prev_arch_ftype *prev_arch;
  };
  
  /* 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 more specific sigtramp unwinder that overrides the
     traditional brute-force unwinder.  */
  extern void frame_unwind_prepend_unwinder (struct gdbarch *,
  					   const struct frame_unwind *);
  
  /* 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_unwinder (struct gdbarch *gdbarch,
  					  const struct frame_unwind *unwinder);
  
  /* Iterate through sniffers for THIS_FRAME frame until one returns with an
     unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
     by this function.  Possibly initialize THIS_CACHE.  */
  
  extern void frame_unwind_find_by_frame (struct frame_info *this_frame,
  					void **this_cache);
  
  /* Helper functions for value-based register unwinding.  These return
     a (possibly lazy) value of the appropriate type.  */
  
  /* Return a value which indicates that FRAME did not save REGNUM.  */
  
  struct value *frame_unwind_got_optimized (struct frame_info *frame,
  					  int regnum);
  
  /* Return a value which indicates that FRAME copied REGNUM into
     register NEW_REGNUM.  */
  
  struct value *frame_unwind_got_register (struct frame_info *frame, int regnum,
  					 int new_regnum);
  
  /* Return a value which indicates that FRAME saved REGNUM in memory at
     ADDR.  */
  
  struct value *frame_unwind_got_memory (struct frame_info *frame, int regnum,
  				       CORE_ADDR addr);
  
  /* Return a value which indicates that FRAME's saved version of
     REGNUM has a known constant (computed) value of VAL.  */
  
  struct value *frame_unwind_got_constant (struct frame_info *frame, int regnum,
  					 ULONGEST val);
  
  /* Return a value which indicates that FRAME's saved version of
     REGNUM has a known constant (computed) value which is stored
     inside BUF.  */
  
  struct value *frame_unwind_got_bytes (struct frame_info *frame, int regnum,
                                        gdb_byte *buf);
  
  /* Return a value which indicates that FRAME's saved version of REGNUM
     has a known constant (computed) value of ADDR.  Convert the
     CORE_ADDR to a target address if necessary.  */
  
  struct value *frame_unwind_got_address (struct frame_info *frame, int regnum,
  					CORE_ADDR addr);
  
  #endif
  