1 /* Find a variable's value in memory, for GDB, the GNU debugger.
3 Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
4 1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004, 2005, 2007
5 Free Software Foundation, Inc.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program. If not, see <http://www.gnu.org/licenses/>. */
30 #include "gdb_string.h"
31 #include "gdb_assert.h"
32 #include "floatformat.h"
33 #include "symfile.h" /* for overlay functions */
35 #include "user-regs.h"
38 /* Basic byte-swapping routines. GDB has needed these for a long time...
39 All extract a target-format integer at ADDR which is LEN bytes long. */
41 #if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8
42 /* 8 bit characters are a pretty safe assumption these days, so we
43 assume it throughout all these swapping routines. If we had to deal with
44 9 bit characters, we would need to make len be in bits and would have
45 to re-write these routines... */
50 extract_signed_integer (const gdb_byte
*addr
, int len
)
53 const unsigned char *p
;
54 const unsigned char *startaddr
= addr
;
55 const unsigned char *endaddr
= startaddr
+ len
;
57 if (len
> (int) sizeof (LONGEST
))
59 That operation is not available on integers of more than %d bytes."),
60 (int) sizeof (LONGEST
));
62 /* Start at the most significant end of the integer, and work towards
63 the least significant. */
64 if (gdbarch_byte_order (current_gdbarch
) == BFD_ENDIAN_BIG
)
67 /* Do the sign extension once at the start. */
68 retval
= ((LONGEST
) * p
^ 0x80) - 0x80;
69 for (++p
; p
< endaddr
; ++p
)
70 retval
= (retval
<< 8) | *p
;
75 /* Do the sign extension once at the start. */
76 retval
= ((LONGEST
) * p
^ 0x80) - 0x80;
77 for (--p
; p
>= startaddr
; --p
)
78 retval
= (retval
<< 8) | *p
;
84 extract_unsigned_integer (const gdb_byte
*addr
, int len
)
87 const unsigned char *p
;
88 const unsigned char *startaddr
= addr
;
89 const unsigned char *endaddr
= startaddr
+ len
;
91 if (len
> (int) sizeof (ULONGEST
))
93 That operation is not available on integers of more than %d bytes."),
94 (int) sizeof (ULONGEST
));
96 /* Start at the most significant end of the integer, and work towards
97 the least significant. */
99 if (gdbarch_byte_order (current_gdbarch
) == BFD_ENDIAN_BIG
)
101 for (p
= startaddr
; p
< endaddr
; ++p
)
102 retval
= (retval
<< 8) | *p
;
106 for (p
= endaddr
- 1; p
>= startaddr
; --p
)
107 retval
= (retval
<< 8) | *p
;
112 /* Sometimes a long long unsigned integer can be extracted as a
113 LONGEST value. This is done so that we can print these values
114 better. If this integer can be converted to a LONGEST, this
115 function returns 1 and sets *PVAL. Otherwise it returns 0. */
118 extract_long_unsigned_integer (const gdb_byte
*addr
, int orig_len
,
122 const gdb_byte
*first_addr
;
126 if (gdbarch_byte_order (current_gdbarch
) == BFD_ENDIAN_BIG
)
129 len
> (int) sizeof (LONGEST
) && p
< addr
+ orig_len
;
142 for (p
= addr
+ orig_len
- 1;
143 len
> (int) sizeof (LONGEST
) && p
>= addr
;
153 if (len
<= (int) sizeof (LONGEST
))
155 *pval
= (LONGEST
) extract_unsigned_integer (first_addr
,
164 /* Treat the bytes at BUF as a pointer of type TYPE, and return the
165 address it represents. */
167 extract_typed_address (const gdb_byte
*buf
, struct type
*type
)
169 if (TYPE_CODE (type
) != TYPE_CODE_PTR
170 && TYPE_CODE (type
) != TYPE_CODE_REF
)
171 internal_error (__FILE__
, __LINE__
,
172 _("extract_typed_address: "
173 "type is not a pointer or reference"));
175 return gdbarch_pointer_to_address (current_gdbarch
, type
, buf
);
180 store_signed_integer (gdb_byte
*addr
, int len
, LONGEST val
)
183 gdb_byte
*startaddr
= addr
;
184 gdb_byte
*endaddr
= startaddr
+ len
;
186 /* Start at the least significant end of the integer, and work towards
187 the most significant. */
188 if (gdbarch_byte_order (current_gdbarch
) == BFD_ENDIAN_BIG
)
190 for (p
= endaddr
- 1; p
>= startaddr
; --p
)
198 for (p
= startaddr
; p
< endaddr
; ++p
)
207 store_unsigned_integer (gdb_byte
*addr
, int len
, ULONGEST val
)
210 unsigned char *startaddr
= (unsigned char *) addr
;
211 unsigned char *endaddr
= startaddr
+ len
;
213 /* Start at the least significant end of the integer, and work towards
214 the most significant. */
215 if (gdbarch_byte_order (current_gdbarch
) == BFD_ENDIAN_BIG
)
217 for (p
= endaddr
- 1; p
>= startaddr
; --p
)
225 for (p
= startaddr
; p
< endaddr
; ++p
)
233 /* Store the address ADDR as a pointer of type TYPE at BUF, in target
236 store_typed_address (gdb_byte
*buf
, struct type
*type
, CORE_ADDR addr
)
238 if (TYPE_CODE (type
) != TYPE_CODE_PTR
239 && TYPE_CODE (type
) != TYPE_CODE_REF
)
240 internal_error (__FILE__
, __LINE__
,
241 _("store_typed_address: "
242 "type is not a pointer or reference"));
244 gdbarch_address_to_pointer (current_gdbarch
, type
, buf
, addr
);
249 /* Return a `value' with the contents of (virtual or cooked) register
250 REGNUM as found in the specified FRAME. The register's type is
251 determined by register_type(). */
254 value_of_register (int regnum
, struct frame_info
*frame
)
258 struct value
*reg_val
;
260 gdb_byte raw_buffer
[MAX_REGISTER_SIZE
];
263 /* User registers lie completely outside of the range of normal
264 registers. Catch them early so that the target never sees them. */
265 if (regnum
>= gdbarch_num_regs (current_gdbarch
)
266 + gdbarch_num_pseudo_regs (current_gdbarch
))
267 return value_of_user_reg (regnum
, frame
);
269 frame_register (frame
, regnum
, &optim
, &lval
, &addr
, &realnum
, raw_buffer
);
271 reg_val
= allocate_value (register_type (current_gdbarch
, regnum
));
273 memcpy (value_contents_raw (reg_val
), raw_buffer
,
274 register_size (current_gdbarch
, regnum
));
275 VALUE_LVAL (reg_val
) = lval
;
276 VALUE_ADDRESS (reg_val
) = addr
;
277 VALUE_REGNUM (reg_val
) = regnum
;
278 set_value_optimized_out (reg_val
, optim
);
279 VALUE_FRAME_ID (reg_val
) = get_frame_id (frame
);
283 /* Given a pointer of type TYPE in target form in BUF, return the
284 address it represents. */
286 unsigned_pointer_to_address (struct type
*type
, const gdb_byte
*buf
)
288 return extract_unsigned_integer (buf
, TYPE_LENGTH (type
));
292 signed_pointer_to_address (struct type
*type
, const gdb_byte
*buf
)
294 return extract_signed_integer (buf
, TYPE_LENGTH (type
));
297 /* Given an address, store it as a pointer of type TYPE in target
300 unsigned_address_to_pointer (struct type
*type
, gdb_byte
*buf
,
303 store_unsigned_integer (buf
, TYPE_LENGTH (type
), addr
);
307 address_to_signed_pointer (struct type
*type
, gdb_byte
*buf
, CORE_ADDR addr
)
309 store_signed_integer (buf
, TYPE_LENGTH (type
), addr
);
312 /* Will calling read_var_value or locate_var_value on SYM end
313 up caring what frame it is being evaluated relative to? SYM must
316 symbol_read_needs_frame (struct symbol
*sym
)
318 switch (SYMBOL_CLASS (sym
))
320 /* All cases listed explicitly so that gcc -Wall will detect it if
321 we failed to consider one. */
323 case LOC_COMPUTED_ARG
:
324 /* FIXME: cagney/2004-01-26: It should be possible to
325 unconditionally call the SYMBOL_OPS method when available.
326 Unfortunately DWARF 2 stores the frame-base (instead of the
327 function) location in a function's symbol. Oops! For the
328 moment enable this when/where applicable. */
329 return SYMBOL_OPS (sym
)->read_needs_frame (sym
);
335 case LOC_REGPARM_ADDR
:
339 case LOC_BASEREG_ARG
:
340 case LOC_HP_THREAD_LOCAL_STATIC
:
350 /* Getting the address of a label can be done independently of the block,
351 even if some *uses* of that address wouldn't work so well without
355 case LOC_CONST_BYTES
:
357 case LOC_OPTIMIZED_OUT
:
363 /* Given a struct symbol for a variable,
364 and a stack frame id, read the value of the variable
365 and return a (pointer to a) struct value containing the value.
366 If the variable cannot be found, return a zero pointer.
367 If FRAME is NULL, use the selected frame. */
370 read_var_value (struct symbol
*var
, struct frame_info
*frame
)
373 struct type
*type
= SYMBOL_TYPE (var
);
377 if (SYMBOL_CLASS (var
) == LOC_COMPUTED
378 || SYMBOL_CLASS (var
) == LOC_COMPUTED_ARG
379 || SYMBOL_CLASS (var
) == LOC_REGISTER
380 || SYMBOL_CLASS (var
) == LOC_REGPARM
)
381 /* These cases do not use V. */
385 v
= allocate_value (type
);
386 VALUE_LVAL (v
) = lval_memory
; /* The most likely possibility. */
389 len
= TYPE_LENGTH (type
);
391 /* FIXME drow/2003-09-06: this call to the selected frame should be
392 pushed upwards to the callers. */
394 frame
= deprecated_safe_get_selected_frame ();
396 switch (SYMBOL_CLASS (var
))
399 /* Put the constant back in target format. */
400 store_signed_integer (value_contents_raw (v
), len
,
401 (LONGEST
) SYMBOL_VALUE (var
));
402 VALUE_LVAL (v
) = not_lval
;
406 /* Put the constant back in target format. */
407 if (overlay_debugging
)
410 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var
),
411 SYMBOL_BFD_SECTION (var
));
412 store_typed_address (value_contents_raw (v
), type
, addr
);
415 store_typed_address (value_contents_raw (v
), type
,
416 SYMBOL_VALUE_ADDRESS (var
));
417 VALUE_LVAL (v
) = not_lval
;
420 case LOC_CONST_BYTES
:
422 memcpy (value_contents_raw (v
), SYMBOL_VALUE_BYTES (var
), len
);
423 VALUE_LVAL (v
) = not_lval
;
428 if (overlay_debugging
)
429 addr
= symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var
),
430 SYMBOL_BFD_SECTION (var
));
432 addr
= SYMBOL_VALUE_ADDRESS (var
);
437 /* The import slot does not have a real address in it from the
438 dynamic loader (dld.sl on HP-UX), if the target hasn't
439 begun execution yet, so check for that. */
442 if (!target_has_execution
)
444 Attempt to access variable defined in different shared object or load module when\n\
445 addresses have not been bound by the dynamic loader. Try again when executable is running."));
447 locaddr
= SYMBOL_VALUE_ADDRESS (var
);
448 loc
= value_at (lookup_pointer_type (type
), locaddr
);
449 addr
= value_as_address (loc
);
456 addr
= get_frame_args_address (frame
);
459 addr
+= SYMBOL_VALUE (var
);
468 argref
= get_frame_args_address (frame
);
471 argref
+= SYMBOL_VALUE (var
);
472 ref
= value_at (lookup_pointer_type (type
), argref
);
473 addr
= value_as_address (ref
);
481 addr
= get_frame_locals_address (frame
);
482 addr
+= SYMBOL_VALUE (var
);
486 case LOC_BASEREG_ARG
:
487 case LOC_HP_THREAD_LOCAL_STATIC
:
489 struct value
*regval
;
491 regval
= value_from_register (lookup_pointer_type (type
),
492 SYMBOL_BASEREG (var
), frame
);
494 error (_("Value of base register not available."));
495 addr
= value_as_address (regval
);
496 addr
+= SYMBOL_VALUE (var
);
501 error (_("Cannot look up value of a typedef"));
505 if (overlay_debugging
)
506 VALUE_ADDRESS (v
) = symbol_overlayed_address
507 (BLOCK_START (SYMBOL_BLOCK_VALUE (var
)), SYMBOL_BFD_SECTION (var
));
509 VALUE_ADDRESS (v
) = BLOCK_START (SYMBOL_BLOCK_VALUE (var
));
514 case LOC_REGPARM_ADDR
:
517 int regno
= SYMBOL_VALUE (var
);
518 struct value
*regval
;
522 b
= get_frame_block (frame
, 0);
524 if (SYMBOL_CLASS (var
) == LOC_REGPARM_ADDR
)
526 regval
= value_from_register (lookup_pointer_type (type
),
531 error (_("Value of register variable not available."));
533 addr
= value_as_address (regval
);
534 VALUE_LVAL (v
) = lval_memory
;
538 regval
= value_from_register (type
, regno
, frame
);
541 error (_("Value of register variable not available."));
548 case LOC_COMPUTED_ARG
:
549 /* FIXME: cagney/2004-01-26: It should be possible to
550 unconditionally call the SYMBOL_OPS method when available.
551 Unfortunately DWARF 2 stores the frame-base (instead of the
552 function) location in a function's symbol. Oops! For the
553 moment enable this when/where applicable. */
554 if (frame
== 0 && SYMBOL_OPS (var
)->read_needs_frame (var
))
556 return SYMBOL_OPS (var
)->read_variable (var
, frame
);
560 struct minimal_symbol
*msym
;
562 msym
= lookup_minimal_symbol (DEPRECATED_SYMBOL_NAME (var
), NULL
, NULL
);
565 if (overlay_debugging
)
566 addr
= symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym
),
567 SYMBOL_BFD_SECTION (msym
));
569 addr
= SYMBOL_VALUE_ADDRESS (msym
);
573 case LOC_OPTIMIZED_OUT
:
574 VALUE_LVAL (v
) = not_lval
;
575 set_value_optimized_out (v
, 1);
579 error (_("Cannot look up value of a botched symbol."));
583 VALUE_ADDRESS (v
) = addr
;
584 set_value_lazy (v
, 1);
588 /* Install default attributes for register values. */
591 default_value_from_register (struct type
*type
, int regnum
,
592 struct frame_info
*frame
)
594 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
595 int len
= TYPE_LENGTH (type
);
596 struct value
*value
= allocate_value (type
);
598 VALUE_LVAL (value
) = lval_register
;
599 VALUE_FRAME_ID (value
) = get_frame_id (frame
);
600 VALUE_REGNUM (value
) = regnum
;
602 /* Any structure stored in more than one register will always be
603 an integral number of registers. Otherwise, you need to do
604 some fiddling with the last register copied here for little
606 if (gdbarch_byte_order (current_gdbarch
) == BFD_ENDIAN_BIG
607 && len
< register_size (gdbarch
, regnum
))
608 /* Big-endian, and we want less than full size. */
609 set_value_offset (value
, register_size (gdbarch
, regnum
) - len
);
611 set_value_offset (value
, 0);
616 /* Return a value of type TYPE, stored in register REGNUM, in frame FRAME. */
619 value_from_register (struct type
*type
, int regnum
, struct frame_info
*frame
)
621 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
622 struct type
*type1
= check_typedef (type
);
625 if (gdbarch_convert_register_p (current_gdbarch
, regnum
, type1
))
627 /* The ISA/ABI need to something weird when obtaining the
628 specified value from this register. It might need to
629 re-order non-adjacent, starting with REGNUM (see MIPS and
630 i386). It might need to convert the [float] register into
631 the corresponding [integer] type (see Alpha). The assumption
632 is that gdbarch_register_to_value populates the entire value
633 including the location. */
634 v
= allocate_value (type
);
635 VALUE_LVAL (v
) = lval_register
;
636 VALUE_FRAME_ID (v
) = get_frame_id (frame
);
637 VALUE_REGNUM (v
) = regnum
;
638 gdbarch_register_to_value (current_gdbarch
,
639 frame
, regnum
, type1
, value_contents_raw (v
));
643 int len
= TYPE_LENGTH (type
);
645 /* Construct the value. */
646 v
= gdbarch_value_from_register (gdbarch
, type
, regnum
, frame
);
649 if (!get_frame_register_bytes (frame
, regnum
, value_offset (v
), len
,
650 value_contents_raw (v
)))
651 set_value_optimized_out (v
, 1);
656 /* Return contents of register REGNUM in frame FRAME as address,
657 interpreted as value of type TYPE. Will abort if register
658 value is not available. */
661 address_from_register (struct type
*type
, int regnum
, struct frame_info
*frame
)
666 value
= value_from_register (type
, regnum
, frame
);
669 result
= value_as_address (value
);
670 release_value (value
);
677 /* Given a struct symbol for a variable or function,
678 and a stack frame id,
679 return a (pointer to a) struct value containing the properly typed
683 locate_var_value (struct symbol
*var
, struct frame_info
*frame
)
686 struct type
*type
= SYMBOL_TYPE (var
);
687 struct value
*lazy_value
;
689 /* Evaluate it first; if the result is a memory address, we're fine.
690 Lazy evaluation pays off here. */
692 lazy_value
= read_var_value (var
, frame
);
694 error (_("Address of \"%s\" is unknown."), SYMBOL_PRINT_NAME (var
));
696 if (value_lazy (lazy_value
)
697 || TYPE_CODE (type
) == TYPE_CODE_FUNC
)
701 addr
= VALUE_ADDRESS (lazy_value
);
702 val
= value_from_pointer (lookup_pointer_type (type
), addr
);
706 /* Not a memory address; check what the problem was. */
707 switch (VALUE_LVAL (lazy_value
))
710 gdb_assert (gdbarch_register_name
711 (current_gdbarch
, VALUE_REGNUM (lazy_value
)) != NULL
712 && *gdbarch_register_name
713 (current_gdbarch
, VALUE_REGNUM (lazy_value
)) != '\0');
714 error (_("Address requested for identifier "
715 "\"%s\" which is in register $%s"),
716 SYMBOL_PRINT_NAME (var
),
717 gdbarch_register_name (current_gdbarch
, VALUE_REGNUM (lazy_value
)));
721 error (_("Can't take address of \"%s\" which isn't an lvalue."),
722 SYMBOL_PRINT_NAME (var
));
725 return 0; /* For lint -- never reached */