[deliverable/binutils-gdb.git] / gdb / frame-unwind.h

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

   Copyright 2003, 2004 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 2 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, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#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, void *valuep);

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;
};

/* 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
Commit	Line	Data
494cca16 AC	1	/* Definitions for a frame unwinder, for GDB, the GNU debugger.
494cca16 AC	2
82417da5	3	Copyright 2003, 2004 Free Software Foundation, Inc.
494cca16 AC	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
82417da5	25	struct frame_data;
494cca16 AC	26	struct frame_info;
	27	struct frame_id;
	28	struct frame_unwind;
	29	struct gdbarch;
	30	struct regcache;
	31
7df05f2b AC	32	#include "frame.h" /* For enum frame_type. */
7df05f2b AC	33
6dc42492 AC	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
82417da5 AC	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
6dc42492 AC	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, void valuep);
494cca16	120
494cca16 AC	121	struct frame_unwind
494cca16 AC	122	{
7df05f2b AC	123	/* The frame's type. Should this instead be a collection of
	124	predicates that test the frame for various attributes? */
	125	enum frame_type type;
494cca16 AC	126	/* Should an attribute indicating the frame's address-in-block go
494cca16 AC	127	here? */
6dc42492 AC	128	frame_this_id_ftype *this_id;
6dc42492 AC	129	frame_prev_register_ftype *prev_register;
82417da5 AC	130	const struct frame_data *unwind_data;
82417da5 AC	131	frame_sniffer_ftype *sniffer;
494cca16 AC	132	};
494cca16 AC	133
fb2be677 AC	134	/* Register a frame unwinder, _prepending_ it to the front of the
	135	search list (so it is sniffed before previously registered
	136	unwinders). By using a prepend, later calls can install unwinders
	137	that override earlier calls. This allows, for instance, an OSABI
	138	to install a a more specific sigtramp unwinder that overrides the
	139	traditional brute-force unwinder. */
	140	extern void frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
	141	const struct frame_unwind *unwinder);
82417da5	142
e8a89fe2 AC	143	/* Given the NEXT frame, take a wiff of THIS frame's registers (namely
	144	the PC and attributes) and if it is the applicable unwinder return
	145	the unwind methods, or NULL if it is not. */
	146
	147	typedef const struct frame_unwind (frame_unwind_sniffer_ftype) (struct frame_info next_frame);
	148
	149	/* Add a frame sniffer to the list. The predicates are polled in the
	150	order that they are appended. The initial list contains the dummy
	151	frame sniffer. */
	152
	153	extern void frame_unwind_append_sniffer (struct gdbarch *gdbarch,
	154	frame_unwind_sniffer_ftype *sniffer);
	155
	156	/* Iterate through the next frame's sniffers until one returns with an
82417da5	157	unwinder implementation. Possibly initialize THIS_CACHE. */
e8a89fe2	158
82417da5 AC	159	extern const struct frame_unwind frame_unwind_find_by_frame (struct frame_info next_frame,
82417da5 AC	160	void **this_cache);
e8a89fe2	161
494cca16	162	#endif