]>
git.ipfire.org Git - thirdparty/binutils-gdb.git/blob - gdb/findvar.c
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, 2008
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
)
256 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
259 struct value
*reg_val
;
261 gdb_byte raw_buffer
[MAX_REGISTER_SIZE
];
264 /* User registers lie completely outside of the range of normal
265 registers. Catch them early so that the target never sees them. */
266 if (regnum
>= gdbarch_num_regs (gdbarch
)
267 + gdbarch_num_pseudo_regs (gdbarch
))
268 return value_of_user_reg (regnum
, frame
);
270 frame_register (frame
, regnum
, &optim
, &lval
, &addr
, &realnum
, raw_buffer
);
272 reg_val
= allocate_value (register_type (gdbarch
, regnum
));
274 memcpy (value_contents_raw (reg_val
), raw_buffer
,
275 register_size (gdbarch
, regnum
));
276 VALUE_LVAL (reg_val
) = lval
;
277 VALUE_ADDRESS (reg_val
) = addr
;
278 VALUE_REGNUM (reg_val
) = regnum
;
279 set_value_optimized_out (reg_val
, optim
);
280 VALUE_FRAME_ID (reg_val
) = get_frame_id (frame
);
284 /* Return a `value' with the contents of (virtual or cooked) register
285 REGNUM as found in the specified FRAME. The register's type is
286 determined by register_type(). The value is not fetched. */
289 value_of_register_lazy (struct frame_info
*frame
, int regnum
)
291 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
292 struct value
*reg_val
;
294 gdb_assert (regnum
< (gdbarch_num_regs (gdbarch
)
295 + gdbarch_num_pseudo_regs (gdbarch
)));
297 /* We should have a valid (i.e. non-sentinel) frame. */
298 gdb_assert (frame_id_p (get_frame_id (frame
)));
300 reg_val
= allocate_value (register_type (gdbarch
, regnum
));
301 VALUE_LVAL (reg_val
) = lval_register
;
302 VALUE_REGNUM (reg_val
) = regnum
;
303 VALUE_FRAME_ID (reg_val
) = get_frame_id (frame
);
304 set_value_lazy (reg_val
, 1);
308 /* Given a pointer of type TYPE in target form in BUF, return the
309 address it represents. */
311 unsigned_pointer_to_address (struct type
*type
, const gdb_byte
*buf
)
313 return extract_unsigned_integer (buf
, TYPE_LENGTH (type
));
317 signed_pointer_to_address (struct type
*type
, const gdb_byte
*buf
)
319 return extract_signed_integer (buf
, TYPE_LENGTH (type
));
322 /* Given an address, store it as a pointer of type TYPE in target
325 unsigned_address_to_pointer (struct type
*type
, gdb_byte
*buf
,
328 store_unsigned_integer (buf
, TYPE_LENGTH (type
), addr
);
332 address_to_signed_pointer (struct type
*type
, gdb_byte
*buf
, CORE_ADDR addr
)
334 store_signed_integer (buf
, TYPE_LENGTH (type
), addr
);
337 /* Will calling read_var_value or locate_var_value on SYM end
338 up caring what frame it is being evaluated relative to? SYM must
341 symbol_read_needs_frame (struct symbol
*sym
)
343 switch (SYMBOL_CLASS (sym
))
345 /* All cases listed explicitly so that gcc -Wall will detect it if
346 we failed to consider one. */
348 case LOC_COMPUTED_ARG
:
349 /* FIXME: cagney/2004-01-26: It should be possible to
350 unconditionally call the SYMBOL_OPS method when available.
351 Unfortunately DWARF 2 stores the frame-base (instead of the
352 function) location in a function's symbol. Oops! For the
353 moment enable this when/where applicable. */
354 return SYMBOL_OPS (sym
)->read_needs_frame (sym
);
360 case LOC_REGPARM_ADDR
:
364 case LOC_BASEREG_ARG
:
373 /* Getting the address of a label can be done independently of the block,
374 even if some *uses* of that address wouldn't work so well without
378 case LOC_CONST_BYTES
:
380 case LOC_OPTIMIZED_OUT
:
386 /* Given a struct symbol for a variable,
387 and a stack frame id, read the value of the variable
388 and return a (pointer to a) struct value containing the value.
389 If the variable cannot be found, return a zero pointer.
390 If FRAME is NULL, use the selected frame. */
393 read_var_value (struct symbol
*var
, struct frame_info
*frame
)
396 struct type
*type
= SYMBOL_TYPE (var
);
400 if (SYMBOL_CLASS (var
) == LOC_COMPUTED
401 || SYMBOL_CLASS (var
) == LOC_COMPUTED_ARG
402 || SYMBOL_CLASS (var
) == LOC_REGISTER
403 || SYMBOL_CLASS (var
) == LOC_REGPARM
)
404 /* These cases do not use V. */
408 v
= allocate_value (type
);
409 VALUE_LVAL (v
) = lval_memory
; /* The most likely possibility. */
412 len
= TYPE_LENGTH (type
);
414 /* FIXME drow/2003-09-06: this call to the selected frame should be
415 pushed upwards to the callers. */
417 frame
= deprecated_safe_get_selected_frame ();
419 switch (SYMBOL_CLASS (var
))
422 /* Put the constant back in target format. */
423 store_signed_integer (value_contents_raw (v
), len
,
424 (LONGEST
) SYMBOL_VALUE (var
));
425 VALUE_LVAL (v
) = not_lval
;
429 /* Put the constant back in target format. */
430 if (overlay_debugging
)
433 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var
),
434 SYMBOL_BFD_SECTION (var
));
435 store_typed_address (value_contents_raw (v
), type
, addr
);
438 store_typed_address (value_contents_raw (v
), type
,
439 SYMBOL_VALUE_ADDRESS (var
));
440 VALUE_LVAL (v
) = not_lval
;
443 case LOC_CONST_BYTES
:
445 memcpy (value_contents_raw (v
), SYMBOL_VALUE_BYTES (var
), len
);
446 VALUE_LVAL (v
) = not_lval
;
451 if (overlay_debugging
)
452 addr
= symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var
),
453 SYMBOL_BFD_SECTION (var
));
455 addr
= SYMBOL_VALUE_ADDRESS (var
);
461 addr
= get_frame_args_address (frame
);
464 addr
+= SYMBOL_VALUE (var
);
473 argref
= get_frame_args_address (frame
);
476 argref
+= SYMBOL_VALUE (var
);
477 ref
= value_at (lookup_pointer_type (type
), argref
);
478 addr
= value_as_address (ref
);
486 addr
= get_frame_locals_address (frame
);
487 addr
+= SYMBOL_VALUE (var
);
491 case LOC_BASEREG_ARG
:
493 struct value
*regval
;
495 regval
= value_from_register (lookup_pointer_type (type
),
496 SYMBOL_BASEREG (var
), frame
);
498 error (_("Value of base register not available."));
499 addr
= value_as_address (regval
);
500 addr
+= SYMBOL_VALUE (var
);
505 error (_("Cannot look up value of a typedef"));
509 if (overlay_debugging
)
510 VALUE_ADDRESS (v
) = symbol_overlayed_address
511 (BLOCK_START (SYMBOL_BLOCK_VALUE (var
)), SYMBOL_BFD_SECTION (var
));
513 VALUE_ADDRESS (v
) = BLOCK_START (SYMBOL_BLOCK_VALUE (var
));
518 case LOC_REGPARM_ADDR
:
521 int regno
= SYMBOL_VALUE (var
);
522 struct value
*regval
;
526 b
= get_frame_block (frame
, 0);
528 if (SYMBOL_CLASS (var
) == LOC_REGPARM_ADDR
)
530 regval
= value_from_register (lookup_pointer_type (type
),
535 error (_("Value of register variable not available."));
537 addr
= value_as_address (regval
);
538 VALUE_LVAL (v
) = lval_memory
;
542 regval
= value_from_register (type
, regno
, frame
);
545 error (_("Value of register variable not available."));
552 case LOC_COMPUTED_ARG
:
553 /* FIXME: cagney/2004-01-26: It should be possible to
554 unconditionally call the SYMBOL_OPS method when available.
555 Unfortunately DWARF 2 stores the frame-base (instead of the
556 function) location in a function's symbol. Oops! For the
557 moment enable this when/where applicable. */
558 if (frame
== 0 && SYMBOL_OPS (var
)->read_needs_frame (var
))
560 return SYMBOL_OPS (var
)->read_variable (var
, frame
);
564 struct minimal_symbol
*msym
;
566 msym
= lookup_minimal_symbol (DEPRECATED_SYMBOL_NAME (var
), NULL
, NULL
);
569 if (overlay_debugging
)
570 addr
= symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym
),
571 SYMBOL_BFD_SECTION (msym
));
573 addr
= SYMBOL_VALUE_ADDRESS (msym
);
577 case LOC_OPTIMIZED_OUT
:
578 VALUE_LVAL (v
) = not_lval
;
579 set_value_optimized_out (v
, 1);
583 error (_("Cannot look up value of a botched symbol."));
587 VALUE_ADDRESS (v
) = addr
;
588 set_value_lazy (v
, 1);
592 /* Install default attributes for register values. */
595 default_value_from_register (struct type
*type
, int regnum
,
596 struct frame_info
*frame
)
598 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
599 int len
= TYPE_LENGTH (type
);
600 struct value
*value
= allocate_value (type
);
602 VALUE_LVAL (value
) = lval_register
;
603 VALUE_FRAME_ID (value
) = get_frame_id (frame
);
604 VALUE_REGNUM (value
) = regnum
;
606 /* Any structure stored in more than one register will always be
607 an integral number of registers. Otherwise, you need to do
608 some fiddling with the last register copied here for little
610 if (gdbarch_byte_order (gdbarch
) == BFD_ENDIAN_BIG
611 && len
< register_size (gdbarch
, regnum
))
612 /* Big-endian, and we want less than full size. */
613 set_value_offset (value
, register_size (gdbarch
, regnum
) - len
);
615 set_value_offset (value
, 0);
620 /* Return a value of type TYPE, stored in register REGNUM, in frame FRAME. */
623 value_from_register (struct type
*type
, int regnum
, struct frame_info
*frame
)
625 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
626 struct type
*type1
= check_typedef (type
);
629 if (gdbarch_convert_register_p (gdbarch
, regnum
, type1
))
631 /* The ISA/ABI need to something weird when obtaining the
632 specified value from this register. It might need to
633 re-order non-adjacent, starting with REGNUM (see MIPS and
634 i386). It might need to convert the [float] register into
635 the corresponding [integer] type (see Alpha). The assumption
636 is that gdbarch_register_to_value populates the entire value
637 including the location. */
638 v
= allocate_value (type
);
639 VALUE_LVAL (v
) = lval_register
;
640 VALUE_FRAME_ID (v
) = get_frame_id (frame
);
641 VALUE_REGNUM (v
) = regnum
;
642 gdbarch_register_to_value (gdbarch
,
643 frame
, regnum
, type1
, value_contents_raw (v
));
647 int len
= TYPE_LENGTH (type
);
649 /* Construct the value. */
650 v
= gdbarch_value_from_register (gdbarch
, type
, regnum
, frame
);
653 if (!get_frame_register_bytes (frame
, regnum
, value_offset (v
), len
,
654 value_contents_raw (v
)))
655 set_value_optimized_out (v
, 1);
660 /* Return contents of register REGNUM in frame FRAME as address,
661 interpreted as value of type TYPE. Will abort if register
662 value is not available. */
665 address_from_register (struct type
*type
, int regnum
, struct frame_info
*frame
)
670 value
= value_from_register (type
, regnum
, frame
);
673 result
= value_as_address (value
);
674 release_value (value
);
681 /* Given a struct symbol for a variable or function,
682 and a stack frame id,
683 return a (pointer to a) struct value containing the properly typed
687 locate_var_value (struct symbol
*var
, struct frame_info
*frame
)
689 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
691 struct type
*type
= SYMBOL_TYPE (var
);
692 struct value
*lazy_value
;
694 /* Evaluate it first; if the result is a memory address, we're fine.
695 Lazy evaluation pays off here. */
697 lazy_value
= read_var_value (var
, frame
);
699 error (_("Address of \"%s\" is unknown."), SYMBOL_PRINT_NAME (var
));
701 if ((VALUE_LVAL (lazy_value
) == lval_memory
&& value_lazy (lazy_value
))
702 || TYPE_CODE (type
) == TYPE_CODE_FUNC
)
706 addr
= VALUE_ADDRESS (lazy_value
);
707 val
= value_from_pointer (lookup_pointer_type (type
), addr
);
711 /* Not a memory address; check what the problem was. */
712 switch (VALUE_LVAL (lazy_value
))
715 gdb_assert (gdbarch_register_name
716 (gdbarch
, VALUE_REGNUM (lazy_value
)) != NULL
717 && *gdbarch_register_name
718 (gdbarch
, VALUE_REGNUM (lazy_value
)) != '\0');
719 error (_("Address requested for identifier "
720 "\"%s\" which is in register $%s"),
721 SYMBOL_PRINT_NAME (var
),
722 gdbarch_register_name (gdbarch
, VALUE_REGNUM (lazy_value
)));
726 error (_("Can't take address of \"%s\" which isn't an lvalue."),
727 SYMBOL_PRINT_NAME (var
));
730 return 0; /* For lint -- never reached */