1 /* Find a variable's value in memory, for GDB, the GNU debugger.
3 Copyright 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
4 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004, 2005 Free
5 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 2 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, write to the Free Software
21 Foundation, Inc., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
32 #include "gdb_string.h"
33 #include "gdb_assert.h"
34 #include "floatformat.h"
35 #include "symfile.h" /* for overlay functions */
37 #include "user-regs.h"
40 /* Basic byte-swapping routines. GDB has needed these for a long time...
41 All extract a target-format integer at ADDR which is LEN bytes long. */
43 #if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8
44 /* 8 bit characters are a pretty safe assumption these days, so we
45 assume it throughout all these swapping routines. If we had to deal with
46 9 bit characters, we would need to make len be in bits and would have
47 to re-write these routines... */
52 extract_signed_integer (const gdb_byte
*addr
, int len
)
55 const unsigned char *p
;
56 const unsigned char *startaddr
= addr
;
57 const unsigned char *endaddr
= startaddr
+ len
;
59 if (len
> (int) sizeof (LONGEST
))
61 That operation is not available on integers of more than %d bytes."),
62 (int) sizeof (LONGEST
));
64 /* Start at the most significant end of the integer, and work towards
65 the least significant. */
66 if (TARGET_BYTE_ORDER
== BFD_ENDIAN_BIG
)
69 /* Do the sign extension once at the start. */
70 retval
= ((LONGEST
) * p
^ 0x80) - 0x80;
71 for (++p
; p
< endaddr
; ++p
)
72 retval
= (retval
<< 8) | *p
;
77 /* Do the sign extension once at the start. */
78 retval
= ((LONGEST
) * p
^ 0x80) - 0x80;
79 for (--p
; p
>= startaddr
; --p
)
80 retval
= (retval
<< 8) | *p
;
86 extract_unsigned_integer (const gdb_byte
*addr
, int len
)
89 const unsigned char *p
;
90 const unsigned char *startaddr
= addr
;
91 const unsigned char *endaddr
= startaddr
+ len
;
93 if (len
> (int) sizeof (ULONGEST
))
95 That operation is not available on integers of more than %d bytes."),
96 (int) sizeof (ULONGEST
));
98 /* Start at the most significant end of the integer, and work towards
99 the least significant. */
101 if (TARGET_BYTE_ORDER
== BFD_ENDIAN_BIG
)
103 for (p
= startaddr
; p
< endaddr
; ++p
)
104 retval
= (retval
<< 8) | *p
;
108 for (p
= endaddr
- 1; p
>= startaddr
; --p
)
109 retval
= (retval
<< 8) | *p
;
114 /* Sometimes a long long unsigned integer can be extracted as a
115 LONGEST value. This is done so that we can print these values
116 better. If this integer can be converted to a LONGEST, this
117 function returns 1 and sets *PVAL. Otherwise it returns 0. */
120 extract_long_unsigned_integer (const gdb_byte
*addr
, int orig_len
,
124 const gdb_byte
*first_addr
;
128 if (TARGET_BYTE_ORDER
== BFD_ENDIAN_BIG
)
131 len
> (int) sizeof (LONGEST
) && p
< addr
+ orig_len
;
144 for (p
= addr
+ orig_len
- 1;
145 len
> (int) sizeof (LONGEST
) && p
>= addr
;
155 if (len
<= (int) sizeof (LONGEST
))
157 *pval
= (LONGEST
) extract_unsigned_integer (first_addr
,
166 /* Treat the bytes at BUF as a pointer of type TYPE, and return the
167 address it represents. */
169 extract_typed_address (const gdb_byte
*buf
, struct type
*type
)
171 if (TYPE_CODE (type
) != TYPE_CODE_PTR
172 && TYPE_CODE (type
) != TYPE_CODE_REF
)
173 internal_error (__FILE__
, __LINE__
,
174 _("extract_typed_address: "
175 "type is not a pointer or reference"));
177 return POINTER_TO_ADDRESS (type
, buf
);
182 store_signed_integer (gdb_byte
*addr
, int len
, LONGEST val
)
185 gdb_byte
*startaddr
= addr
;
186 gdb_byte
*endaddr
= startaddr
+ len
;
188 /* Start at the least significant end of the integer, and work towards
189 the most significant. */
190 if (TARGET_BYTE_ORDER
== BFD_ENDIAN_BIG
)
192 for (p
= endaddr
- 1; p
>= startaddr
; --p
)
200 for (p
= startaddr
; p
< endaddr
; ++p
)
209 store_unsigned_integer (gdb_byte
*addr
, int len
, ULONGEST val
)
212 unsigned char *startaddr
= (unsigned char *) addr
;
213 unsigned char *endaddr
= startaddr
+ len
;
215 /* Start at the least significant end of the integer, and work towards
216 the most significant. */
217 if (TARGET_BYTE_ORDER
== BFD_ENDIAN_BIG
)
219 for (p
= endaddr
- 1; p
>= startaddr
; --p
)
227 for (p
= startaddr
; p
< endaddr
; ++p
)
235 /* Store the address ADDR as a pointer of type TYPE at BUF, in target
238 store_typed_address (gdb_byte
*buf
, struct type
*type
, CORE_ADDR addr
)
240 if (TYPE_CODE (type
) != TYPE_CODE_PTR
241 && TYPE_CODE (type
) != TYPE_CODE_REF
)
242 internal_error (__FILE__
, __LINE__
,
243 _("store_typed_address: "
244 "type is not a pointer or reference"));
246 ADDRESS_TO_POINTER (type
, buf
, addr
);
251 /* Return a `value' with the contents of (virtual or cooked) register
252 REGNUM as found in the specified FRAME. The register's type is
253 determined by register_type().
255 NOTE: returns NULL if register value is not available. Caller will
256 check return value or die! */
259 value_of_register (int regnum
, struct frame_info
*frame
)
263 struct value
*reg_val
;
265 gdb_byte raw_buffer
[MAX_REGISTER_SIZE
];
268 /* User registers lie completely outside of the range of normal
269 registers. Catch them early so that the target never sees them. */
270 if (regnum
>= NUM_REGS
+ NUM_PSEUDO_REGS
)
271 return value_of_user_reg (regnum
, frame
);
273 frame_register (frame
, regnum
, &optim
, &lval
, &addr
, &realnum
, raw_buffer
);
275 /* FIXME: cagney/2002-05-15: This test is just bogus.
277 It indicates that the target failed to supply a value for a
278 register because it was "not available" at this time. Problem
279 is, the target still has the register and so get saved_register()
280 may be returning a value saved on the stack. */
282 if (register_cached (regnum
) < 0)
283 return NULL
; /* register value not available */
285 reg_val
= allocate_value (register_type (current_gdbarch
, regnum
));
287 memcpy (value_contents_raw (reg_val
), raw_buffer
,
288 register_size (current_gdbarch
, regnum
));
289 VALUE_LVAL (reg_val
) = lval
;
290 VALUE_ADDRESS (reg_val
) = addr
;
291 VALUE_REGNUM (reg_val
) = regnum
;
292 set_value_optimized_out (reg_val
, optim
);
293 VALUE_FRAME_ID (reg_val
) = get_frame_id (frame
);
297 /* Given a pointer of type TYPE in target form in BUF, return the
298 address it represents. */
300 unsigned_pointer_to_address (struct type
*type
, const gdb_byte
*buf
)
302 return extract_unsigned_integer (buf
, TYPE_LENGTH (type
));
306 signed_pointer_to_address (struct type
*type
, const gdb_byte
*buf
)
308 return extract_signed_integer (buf
, TYPE_LENGTH (type
));
311 /* Given an address, store it as a pointer of type TYPE in target
314 unsigned_address_to_pointer (struct type
*type
, gdb_byte
*buf
,
317 store_unsigned_integer (buf
, TYPE_LENGTH (type
), addr
);
321 address_to_signed_pointer (struct type
*type
, gdb_byte
*buf
, CORE_ADDR addr
)
323 store_signed_integer (buf
, TYPE_LENGTH (type
), addr
);
326 /* Will calling read_var_value or locate_var_value on SYM end
327 up caring what frame it is being evaluated relative to? SYM must
330 symbol_read_needs_frame (struct symbol
*sym
)
332 switch (SYMBOL_CLASS (sym
))
334 /* All cases listed explicitly so that gcc -Wall will detect it if
335 we failed to consider one. */
337 case LOC_COMPUTED_ARG
:
338 /* FIXME: cagney/2004-01-26: It should be possible to
339 unconditionally call the SYMBOL_OPS method when available.
340 Unfortunately DWARF 2 stores the frame-base (instead of the
341 function) location in a function's symbol. Oops! For the
342 moment enable this when/where applicable. */
343 return SYMBOL_OPS (sym
)->read_needs_frame (sym
);
349 case LOC_REGPARM_ADDR
:
353 case LOC_BASEREG_ARG
:
354 case LOC_HP_THREAD_LOCAL_STATIC
:
364 /* Getting the address of a label can be done independently of the block,
365 even if some *uses* of that address wouldn't work so well without
369 case LOC_CONST_BYTES
:
371 case LOC_OPTIMIZED_OUT
:
377 /* Given a struct symbol for a variable,
378 and a stack frame id, read the value of the variable
379 and return a (pointer to a) struct value containing the value.
380 If the variable cannot be found, return a zero pointer.
381 If FRAME is NULL, use the deprecated_selected_frame. */
384 read_var_value (struct symbol
*var
, struct frame_info
*frame
)
387 struct type
*type
= SYMBOL_TYPE (var
);
391 if (SYMBOL_CLASS (var
) == LOC_COMPUTED
392 || SYMBOL_CLASS (var
) == LOC_COMPUTED_ARG
393 || SYMBOL_CLASS (var
) == LOC_REGISTER
394 || SYMBOL_CLASS (var
) == LOC_REGPARM
)
395 /* These cases do not use V. */
399 v
= allocate_value (type
);
400 VALUE_LVAL (v
) = lval_memory
; /* The most likely possibility. */
403 len
= TYPE_LENGTH (type
);
405 /* FIXME drow/2003-09-06: this call to the selected frame should be
406 pushed upwards to the callers. */
408 frame
= deprecated_safe_get_selected_frame ();
410 switch (SYMBOL_CLASS (var
))
413 /* Put the constant back in target format. */
414 store_signed_integer (value_contents_raw (v
), len
,
415 (LONGEST
) SYMBOL_VALUE (var
));
416 VALUE_LVAL (v
) = not_lval
;
420 /* Put the constant back in target format. */
421 if (overlay_debugging
)
424 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var
),
425 SYMBOL_BFD_SECTION (var
));
426 store_typed_address (value_contents_raw (v
), type
, addr
);
429 store_typed_address (value_contents_raw (v
), type
,
430 SYMBOL_VALUE_ADDRESS (var
));
431 VALUE_LVAL (v
) = not_lval
;
434 case LOC_CONST_BYTES
:
437 bytes_addr
= SYMBOL_VALUE_BYTES (var
);
438 memcpy (value_contents_raw (v
), bytes_addr
, len
);
439 VALUE_LVAL (v
) = not_lval
;
444 if (overlay_debugging
)
445 addr
= symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var
),
446 SYMBOL_BFD_SECTION (var
));
448 addr
= SYMBOL_VALUE_ADDRESS (var
);
453 /* The import slot does not have a real address in it from the
454 dynamic loader (dld.sl on HP-UX), if the target hasn't
455 begun execution yet, so check for that. */
458 if (!target_has_execution
)
460 Attempt to access variable defined in different shared object or load module when\n\
461 addresses have not been bound by the dynamic loader. Try again when executable is running."));
463 locaddr
= SYMBOL_VALUE_ADDRESS (var
);
464 loc
= value_at (lookup_pointer_type (type
), locaddr
);
465 addr
= value_as_address (loc
);
472 addr
= get_frame_args_address (frame
);
475 addr
+= SYMBOL_VALUE (var
);
484 argref
= get_frame_args_address (frame
);
487 argref
+= SYMBOL_VALUE (var
);
488 ref
= value_at (lookup_pointer_type (type
), argref
);
489 addr
= value_as_address (ref
);
497 addr
= get_frame_locals_address (frame
);
498 addr
+= SYMBOL_VALUE (var
);
502 case LOC_BASEREG_ARG
:
503 case LOC_HP_THREAD_LOCAL_STATIC
:
505 struct value
*regval
;
507 regval
= value_from_register (lookup_pointer_type (type
),
508 SYMBOL_BASEREG (var
), frame
);
510 error (_("Value of base register not available."));
511 addr
= value_as_address (regval
);
512 addr
+= SYMBOL_VALUE (var
);
517 error (_("Cannot look up value of a typedef"));
521 if (overlay_debugging
)
522 VALUE_ADDRESS (v
) = symbol_overlayed_address
523 (BLOCK_START (SYMBOL_BLOCK_VALUE (var
)), SYMBOL_BFD_SECTION (var
));
525 VALUE_ADDRESS (v
) = BLOCK_START (SYMBOL_BLOCK_VALUE (var
));
530 case LOC_REGPARM_ADDR
:
533 int regno
= SYMBOL_VALUE (var
);
534 struct value
*regval
;
538 b
= get_frame_block (frame
, 0);
540 if (SYMBOL_CLASS (var
) == LOC_REGPARM_ADDR
)
542 regval
= value_from_register (lookup_pointer_type (type
),
547 error (_("Value of register variable not available."));
549 addr
= value_as_address (regval
);
550 VALUE_LVAL (v
) = lval_memory
;
554 regval
= value_from_register (type
, regno
, frame
);
557 error (_("Value of register variable not available."));
564 case LOC_COMPUTED_ARG
:
565 /* FIXME: cagney/2004-01-26: It should be possible to
566 unconditionally call the SYMBOL_OPS method when available.
567 Unfortunately DWARF 2 stores the frame-base (instead of the
568 function) location in a function's symbol. Oops! For the
569 moment enable this when/where applicable. */
570 if (frame
== 0 && SYMBOL_OPS (var
)->read_needs_frame (var
))
572 return SYMBOL_OPS (var
)->read_variable (var
, frame
);
576 struct minimal_symbol
*msym
;
578 msym
= lookup_minimal_symbol (DEPRECATED_SYMBOL_NAME (var
), NULL
, NULL
);
581 if (overlay_debugging
)
582 addr
= symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym
),
583 SYMBOL_BFD_SECTION (msym
));
585 addr
= SYMBOL_VALUE_ADDRESS (msym
);
589 case LOC_OPTIMIZED_OUT
:
590 VALUE_LVAL (v
) = not_lval
;
591 set_value_optimized_out (v
, 1);
595 error (_("Cannot look up value of a botched symbol."));
599 VALUE_ADDRESS (v
) = addr
;
600 set_value_lazy (v
, 1);
604 /* Return a value of type TYPE, stored in register REGNUM, in frame
607 NOTE: returns NULL if register value is not available.
608 Caller will check return value or die! */
611 value_from_register (struct type
*type
, int regnum
, struct frame_info
*frame
)
613 struct gdbarch
*gdbarch
= get_frame_arch (frame
);
614 struct value
*v
= allocate_value (type
);
615 CHECK_TYPEDEF (type
);
617 if (TYPE_LENGTH (type
) == 0)
619 /* It doesn't matter much what we return for this: since the
620 length is zero, it could be anything. But if allowed to see
621 a zero-length type, the register-finding loop below will set
622 neither mem_stor nor reg_stor, and then report an internal
625 Zero-length types can legitimately arise from declarations
626 like 'struct {}' (a GCC extension, not valid ISO C). GDB may
627 also create them when it finds bogus debugging information;
628 for example, in GCC 2.95.4 and binutils 2.11.93.0.2, the
629 STABS BINCL->EXCL compression process can create bad type
630 numbers. GDB reads these as TYPE_CODE_UNDEF types, with zero
631 length. (That bug is actually the only known way to get a
632 zero-length value allocated to a register --- which is what
633 it takes to make it here.)
635 We'll just attribute the value to the original register. */
636 VALUE_LVAL (v
) = lval_register
;
637 VALUE_ADDRESS (v
) = regnum
;
638 VALUE_REGNUM (v
) = regnum
;
640 else if (CONVERT_REGISTER_P (regnum
, type
))
642 /* The ISA/ABI need to something weird when obtaining the
643 specified value from this register. It might need to
644 re-order non-adjacent, starting with REGNUM (see MIPS and
645 i386). It might need to convert the [float] register into
646 the corresponding [integer] type (see Alpha). The assumption
647 is that REGISTER_TO_VALUE populates the entire value
648 including the location. */
649 REGISTER_TO_VALUE (frame
, regnum
, type
, value_contents_raw (v
));
650 VALUE_LVAL (v
) = lval_register
;
651 VALUE_FRAME_ID (v
) = get_frame_id (frame
);
652 VALUE_REGNUM (v
) = regnum
;
657 int mem_stor
= 0, reg_stor
= 0;
658 int mem_tracking
= 1;
659 CORE_ADDR last_addr
= 0;
660 CORE_ADDR first_addr
= 0;
661 int first_realnum
= regnum
;
662 int len
= TYPE_LENGTH (type
);
663 int value_bytes_copied
;
665 gdb_byte
*value_bytes
= alloca (len
+ MAX_REGISTER_SIZE
);
667 /* Copy all of the data out, whereever it may be. */
668 for (local_regnum
= regnum
, value_bytes_copied
= 0;
669 value_bytes_copied
< len
;
670 (value_bytes_copied
+= register_size (current_gdbarch
, local_regnum
),
677 frame_register (frame
, local_regnum
, &optim
, &lval
, &addr
,
678 &realnum
, value_bytes
+ value_bytes_copied
);
680 if (register_cached (local_regnum
) == -1)
681 return NULL
; /* register value not available */
683 if (regnum
== local_regnum
)
686 first_realnum
= realnum
;
688 if (lval
== lval_register
)
694 /* FIXME: cagney/2004-11-12: I think this is trying to
695 check that the stored registers are adjacent in
696 memory. It isn't doing a good job? */
697 mem_tracking
= (mem_tracking
698 && (regnum
== local_regnum
699 || addr
== last_addr
));
704 if (mem_tracking
&& mem_stor
&& !reg_stor
)
706 VALUE_LVAL (v
) = lval_memory
;
707 VALUE_ADDRESS (v
) = first_addr
;
711 VALUE_LVAL (v
) = lval_register
;
712 VALUE_FRAME_ID (v
) = get_frame_id (frame
);
713 VALUE_REGNUM (v
) = regnum
;
716 set_value_optimized_out (v
, optimized
);
718 /* Any structure stored in more than one register will always be
719 an integral number of registers. Otherwise, you need to do
720 some fiddling with the last register copied here for little
722 if (TARGET_BYTE_ORDER
== BFD_ENDIAN_BIG
723 && len
< register_size (current_gdbarch
, regnum
))
724 /* Big-endian, and we want less than full size. */
725 set_value_offset (v
, register_size (current_gdbarch
, regnum
) - len
);
727 set_value_offset (v
, 0);
728 memcpy (value_contents_raw (v
), value_bytes
+ value_offset (v
), len
);
734 /* Given a struct symbol for a variable or function,
735 and a stack frame id,
736 return a (pointer to a) struct value containing the properly typed
740 locate_var_value (struct symbol
*var
, struct frame_info
*frame
)
743 struct type
*type
= SYMBOL_TYPE (var
);
744 struct value
*lazy_value
;
746 /* Evaluate it first; if the result is a memory address, we're fine.
747 Lazy evaluation pays off here. */
749 lazy_value
= read_var_value (var
, frame
);
751 error (_("Address of \"%s\" is unknown."), SYMBOL_PRINT_NAME (var
));
753 if (value_lazy (lazy_value
)
754 || TYPE_CODE (type
) == TYPE_CODE_FUNC
)
758 addr
= VALUE_ADDRESS (lazy_value
);
759 val
= value_from_pointer (lookup_pointer_type (type
), addr
);
763 /* Not a memory address; check what the problem was. */
764 switch (VALUE_LVAL (lazy_value
))
767 gdb_assert (REGISTER_NAME (VALUE_REGNUM (lazy_value
)) != NULL
768 && *REGISTER_NAME (VALUE_REGNUM (lazy_value
)) != '\0');
769 error (_("Address requested for identifier "
770 "\"%s\" which is in register $%s"),
771 SYMBOL_PRINT_NAME (var
),
772 REGISTER_NAME (VALUE_REGNUM (lazy_value
)));
776 error (_("Can't take address of \"%s\" which isn't an lvalue."),
777 SYMBOL_PRINT_NAME (var
));
780 return 0; /* For lint -- never reached */