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, 2009
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"
39 /* Basic byte-swapping routines. GDB has needed these for a long time...
40 All extract a target-format integer at ADDR which is LEN bytes long. */
42 #if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8
43 /* 8 bit characters are a pretty safe assumption these days, so we
44 assume it throughout all these swapping routines. If we had to deal with
45 9 bit characters, we would need to make len be in bits and would have
46 to re-write these routines... */
51 extract_signed_integer (const gdb_byte *addr, int len)
54 const unsigned char *p;
55 const unsigned char *startaddr = addr;
56 const unsigned char *endaddr = startaddr + len;
58 if (len > (int) sizeof (LONGEST))
60 That operation is not available on integers of more than %d bytes."),
61 (int) sizeof (LONGEST));
63 /* Start at the most significant end of the integer, and work towards
64 the least significant. */
65 if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
68 /* Do the sign extension once at the start. */
69 retval = ((LONGEST) * p ^ 0x80) - 0x80;
70 for (++p; p < endaddr; ++p)
71 retval = (retval << 8) | *p;
76 /* Do the sign extension once at the start. */
77 retval = ((LONGEST) * p ^ 0x80) - 0x80;
78 for (--p; p >= startaddr; --p)
79 retval = (retval << 8) | *p;
85 extract_unsigned_integer (const gdb_byte *addr, int len)
88 const unsigned char *p;
89 const unsigned char *startaddr = addr;
90 const unsigned char *endaddr = startaddr + len;
92 if (len > (int) sizeof (ULONGEST))
94 That operation is not available on integers of more than %d bytes."),
95 (int) sizeof (ULONGEST));
97 /* Start at the most significant end of the integer, and work towards
98 the least significant. */
100 if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
102 for (p = startaddr; p < endaddr; ++p)
103 retval = (retval << 8) | *p;
107 for (p = endaddr - 1; p >= startaddr; --p)
108 retval = (retval << 8) | *p;
113 /* Sometimes a long long unsigned integer can be extracted as a
114 LONGEST value. This is done so that we can print these values
115 better. If this integer can be converted to a LONGEST, this
116 function returns 1 and sets *PVAL. Otherwise it returns 0. */
119 extract_long_unsigned_integer (const gdb_byte *addr, int orig_len,
123 const gdb_byte *first_addr;
127 if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
130 len > (int) sizeof (LONGEST) && p < addr + orig_len;
143 for (p = addr + orig_len - 1;
144 len > (int) sizeof (LONGEST) && p >= addr;
154 if (len <= (int) sizeof (LONGEST))
156 *pval = (LONGEST) extract_unsigned_integer (first_addr,
165 /* Treat the bytes at BUF as a pointer of type TYPE, and return the
166 address it represents. */
168 extract_typed_address (const gdb_byte *buf, struct type *type)
170 if (TYPE_CODE (type) != TYPE_CODE_PTR
171 && TYPE_CODE (type) != TYPE_CODE_REF)
172 internal_error (__FILE__, __LINE__,
173 _("extract_typed_address: "
174 "type is not a pointer or reference"));
176 return gdbarch_pointer_to_address (current_gdbarch, type, buf);
181 store_signed_integer (gdb_byte *addr, int len, LONGEST val)
184 gdb_byte *startaddr = addr;
185 gdb_byte *endaddr = startaddr + len;
187 /* Start at the least significant end of the integer, and work towards
188 the most significant. */
189 if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
191 for (p = endaddr - 1; p >= startaddr; --p)
199 for (p = startaddr; p < endaddr; ++p)
208 store_unsigned_integer (gdb_byte *addr, int len, ULONGEST val)
211 unsigned char *startaddr = (unsigned char *) addr;
212 unsigned char *endaddr = startaddr + len;
214 /* Start at the least significant end of the integer, and work towards
215 the most significant. */
216 if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
218 for (p = endaddr - 1; p >= startaddr; --p)
226 for (p = startaddr; p < endaddr; ++p)
234 /* Store the address ADDR as a pointer of type TYPE at BUF, in target
237 store_typed_address (gdb_byte *buf, struct type *type, CORE_ADDR addr)
239 if (TYPE_CODE (type) != TYPE_CODE_PTR
240 && TYPE_CODE (type) != TYPE_CODE_REF)
241 internal_error (__FILE__, __LINE__,
242 _("store_typed_address: "
243 "type is not a pointer or reference"));
245 gdbarch_address_to_pointer (current_gdbarch, type, buf, addr);
250 /* Return a `value' with the contents of (virtual or cooked) register
251 REGNUM as found in the specified FRAME. The register's type is
252 determined by register_type(). */
255 value_of_register (int regnum, struct frame_info *frame)
257 struct gdbarch *gdbarch = get_frame_arch (frame);
260 struct value *reg_val;
262 gdb_byte raw_buffer[MAX_REGISTER_SIZE];
265 /* User registers lie completely outside of the range of normal
266 registers. Catch them early so that the target never sees them. */
267 if (regnum >= gdbarch_num_regs (gdbarch)
268 + gdbarch_num_pseudo_regs (gdbarch))
269 return value_of_user_reg (regnum, frame);
271 frame_register (frame, regnum, &optim, &lval, &addr, &realnum, raw_buffer);
273 reg_val = allocate_value (register_type (gdbarch, regnum));
275 memcpy (value_contents_raw (reg_val), raw_buffer,
276 register_size (gdbarch, regnum));
277 VALUE_LVAL (reg_val) = lval;
278 VALUE_ADDRESS (reg_val) = addr;
279 VALUE_REGNUM (reg_val) = regnum;
280 set_value_optimized_out (reg_val, optim);
281 VALUE_FRAME_ID (reg_val) = get_frame_id (frame);
285 /* Return a `value' with the contents of (virtual or cooked) register
286 REGNUM as found in the specified FRAME. The register's type is
287 determined by register_type(). The value is not fetched. */
290 value_of_register_lazy (struct frame_info *frame, int regnum)
292 struct gdbarch *gdbarch = get_frame_arch (frame);
293 struct value *reg_val;
295 gdb_assert (regnum < (gdbarch_num_regs (gdbarch)
296 + gdbarch_num_pseudo_regs (gdbarch)));
298 /* We should have a valid (i.e. non-sentinel) frame. */
299 gdb_assert (frame_id_p (get_frame_id (frame)));
301 reg_val = allocate_value (register_type (gdbarch, regnum));
302 VALUE_LVAL (reg_val) = lval_register;
303 VALUE_REGNUM (reg_val) = regnum;
304 VALUE_FRAME_ID (reg_val) = get_frame_id (frame);
305 set_value_lazy (reg_val, 1);
309 /* Given a pointer of type TYPE in target form in BUF, return the
310 address it represents. */
312 unsigned_pointer_to_address (struct type *type, const gdb_byte *buf)
314 return extract_unsigned_integer (buf, TYPE_LENGTH (type));
318 signed_pointer_to_address (struct type *type, const gdb_byte *buf)
320 return extract_signed_integer (buf, TYPE_LENGTH (type));
323 /* Given an address, store it as a pointer of type TYPE in target
326 unsigned_address_to_pointer (struct type *type, gdb_byte *buf,
329 store_unsigned_integer (buf, TYPE_LENGTH (type), addr);
333 address_to_signed_pointer (struct type *type, gdb_byte *buf, CORE_ADDR addr)
335 store_signed_integer (buf, TYPE_LENGTH (type), addr);
338 /* Will calling read_var_value or locate_var_value on SYM end
339 up caring what frame it is being evaluated relative to? SYM must
342 symbol_read_needs_frame (struct symbol *sym)
344 switch (SYMBOL_CLASS (sym))
346 /* All cases listed explicitly so that gcc -Wall will detect it if
347 we failed to consider one. */
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);
359 case LOC_REGPARM_ADDR:
369 /* Getting the address of a label can be done independently of the block,
370 even if some *uses* of that address wouldn't work so well without
374 case LOC_CONST_BYTES:
376 case LOC_OPTIMIZED_OUT:
382 /* Given a struct symbol for a variable,
383 and a stack frame id, read the value of the variable
384 and return a (pointer to a) struct value containing the value.
385 If the variable cannot be found, return a zero pointer.
386 If FRAME is NULL, use the selected frame. */
389 read_var_value (struct symbol *var, struct frame_info *frame)
392 struct type *type = SYMBOL_TYPE (var);
396 if (SYMBOL_CLASS (var) == LOC_COMPUTED
397 || SYMBOL_CLASS (var) == LOC_REGISTER)
398 /* These cases do not use V. */
402 v = allocate_value (type);
403 VALUE_LVAL (v) = lval_memory; /* The most likely possibility. */
406 len = TYPE_LENGTH (type);
408 /* FIXME drow/2003-09-06: this call to the selected frame should be
409 pushed upwards to the callers. */
411 frame = deprecated_safe_get_selected_frame ();
413 switch (SYMBOL_CLASS (var))
416 /* Put the constant back in target format. */
417 store_signed_integer (value_contents_raw (v), len,
418 (LONGEST) SYMBOL_VALUE (var));
419 VALUE_LVAL (v) = not_lval;
423 /* Put the constant back in target format. */
424 if (overlay_debugging)
427 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
428 SYMBOL_OBJ_SECTION (var));
429 store_typed_address (value_contents_raw (v), type, addr);
432 store_typed_address (value_contents_raw (v), type,
433 SYMBOL_VALUE_ADDRESS (var));
434 VALUE_LVAL (v) = not_lval;
437 case LOC_CONST_BYTES:
439 memcpy (value_contents_raw (v), SYMBOL_VALUE_BYTES (var), len);
440 VALUE_LVAL (v) = not_lval;
445 if (overlay_debugging)
446 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
447 SYMBOL_OBJ_SECTION (var));
449 addr = SYMBOL_VALUE_ADDRESS (var);
455 addr = get_frame_args_address (frame);
458 addr += SYMBOL_VALUE (var);
467 argref = get_frame_args_address (frame);
470 argref += SYMBOL_VALUE (var);
471 ref = value_at (lookup_pointer_type (type), argref);
472 addr = value_as_address (ref);
479 addr = get_frame_locals_address (frame);
480 addr += SYMBOL_VALUE (var);
484 error (_("Cannot look up value of a typedef"));
488 if (overlay_debugging)
489 VALUE_ADDRESS (v) = symbol_overlayed_address
490 (BLOCK_START (SYMBOL_BLOCK_VALUE (var)), SYMBOL_OBJ_SECTION (var));
492 VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (var));
496 case LOC_REGPARM_ADDR:
498 int regno = SYMBOL_VALUE (var);
499 struct value *regval;
504 if (SYMBOL_CLASS (var) == LOC_REGPARM_ADDR)
506 regval = value_from_register (lookup_pointer_type (type),
511 error (_("Value of register variable not available."));
513 addr = value_as_address (regval);
514 VALUE_LVAL (v) = lval_memory;
518 regval = value_from_register (type, regno, frame);
521 error (_("Value of register variable not available."));
528 /* FIXME: cagney/2004-01-26: It should be possible to
529 unconditionally call the SYMBOL_OPS method when available.
530 Unfortunately DWARF 2 stores the frame-base (instead of the
531 function) location in a function's symbol. Oops! For the
532 moment enable this when/where applicable. */
533 if (frame == 0 && SYMBOL_OPS (var)->read_needs_frame (var))
535 return SYMBOL_OPS (var)->read_variable (var, frame);
539 struct minimal_symbol *msym;
540 struct obj_section *obj_section;
542 msym = lookup_minimal_symbol (SYMBOL_LINKAGE_NAME (var), NULL, NULL);
545 if (overlay_debugging)
546 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym),
547 SYMBOL_OBJ_SECTION (msym));
549 addr = SYMBOL_VALUE_ADDRESS (msym);
551 obj_section = SYMBOL_OBJ_SECTION (msym);
553 && (obj_section->the_bfd_section->flags & SEC_THREAD_LOCAL) != 0)
554 addr = target_translate_tls_address (obj_section->objfile, addr);
558 case LOC_OPTIMIZED_OUT:
559 VALUE_LVAL (v) = not_lval;
560 set_value_optimized_out (v, 1);
564 error (_("Cannot look up value of a botched symbol."));
568 VALUE_ADDRESS (v) = addr;
569 set_value_lazy (v, 1);
573 /* Install default attributes for register values. */
576 default_value_from_register (struct type *type, int regnum,
577 struct frame_info *frame)
579 struct gdbarch *gdbarch = get_frame_arch (frame);
580 int len = TYPE_LENGTH (type);
581 struct value *value = allocate_value (type);
583 VALUE_LVAL (value) = lval_register;
584 VALUE_FRAME_ID (value) = get_frame_id (frame);
585 VALUE_REGNUM (value) = regnum;
587 /* Any structure stored in more than one register will always be
588 an integral number of registers. Otherwise, you need to do
589 some fiddling with the last register copied here for little
591 if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG
592 && len < register_size (gdbarch, regnum))
593 /* Big-endian, and we want less than full size. */
594 set_value_offset (value, register_size (gdbarch, regnum) - len);
596 set_value_offset (value, 0);
601 /* Return a value of type TYPE, stored in register REGNUM, in frame FRAME. */
604 value_from_register (struct type *type, int regnum, struct frame_info *frame)
606 struct gdbarch *gdbarch = get_frame_arch (frame);
607 struct type *type1 = check_typedef (type);
610 if (gdbarch_convert_register_p (gdbarch, regnum, type1))
612 /* The ISA/ABI need to something weird when obtaining the
613 specified value from this register. It might need to
614 re-order non-adjacent, starting with REGNUM (see MIPS and
615 i386). It might need to convert the [float] register into
616 the corresponding [integer] type (see Alpha). The assumption
617 is that gdbarch_register_to_value populates the entire value
618 including the location. */
619 v = allocate_value (type);
620 VALUE_LVAL (v) = lval_register;
621 VALUE_FRAME_ID (v) = get_frame_id (frame);
622 VALUE_REGNUM (v) = regnum;
623 gdbarch_register_to_value (gdbarch,
624 frame, regnum, type1, value_contents_raw (v));
628 int len = TYPE_LENGTH (type);
630 /* Construct the value. */
631 v = gdbarch_value_from_register (gdbarch, type, regnum, frame);
634 if (!get_frame_register_bytes (frame, regnum, value_offset (v), len,
635 value_contents_raw (v)))
636 set_value_optimized_out (v, 1);
641 /* Return contents of register REGNUM in frame FRAME as address,
642 interpreted as value of type TYPE. Will abort if register
643 value is not available. */
646 address_from_register (struct type *type, int regnum, struct frame_info *frame)
651 value = value_from_register (type, regnum, frame);
654 result = value_as_address (value);
655 release_value (value);
662 /* Given a struct symbol for a variable or function,
663 and a stack frame id,
664 return a (pointer to a) struct value containing the properly typed
668 locate_var_value (struct symbol *var, struct frame_info *frame)
670 struct gdbarch *gdbarch;
672 struct type *type = SYMBOL_TYPE (var);
673 struct value *lazy_value;
675 /* Evaluate it first; if the result is a memory address, we're fine.
676 Lazy evaluation pays off here. */
678 lazy_value = read_var_value (var, frame);
680 error (_("Address of \"%s\" is unknown."), SYMBOL_PRINT_NAME (var));
682 if ((VALUE_LVAL (lazy_value) == lval_memory && value_lazy (lazy_value))
683 || TYPE_CODE (type) == TYPE_CODE_FUNC)
687 addr = VALUE_ADDRESS (lazy_value);
688 val = value_from_pointer (lookup_pointer_type (type), addr);
692 /* Not a memory address; check what the problem was. */
693 switch (VALUE_LVAL (lazy_value))
697 gdbarch = get_frame_arch (frame);
698 gdb_assert (gdbarch_register_name
699 (gdbarch, VALUE_REGNUM (lazy_value)) != NULL
700 && *gdbarch_register_name
701 (gdbarch, VALUE_REGNUM (lazy_value)) != '\0');
702 error (_("Address requested for identifier "
703 "\"%s\" which is in register $%s"),
704 SYMBOL_PRINT_NAME (var),
705 gdbarch_register_name (gdbarch, VALUE_REGNUM (lazy_value)));
709 error (_("Can't take address of \"%s\" which isn't an lvalue."),
710 SYMBOL_PRINT_NAME (var));
713 return 0; /* For lint -- never reached */