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 Free Software
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 void *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 void *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 void *addr, int orig_len, LONGEST *pval)
122 char *p, *first_addr;
126 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
128 for (p = (char *) addr;
129 len > (int) sizeof (LONGEST) && p < (char *) addr + orig_len;
141 first_addr = (char *) addr;
142 for (p = (char *) addr + orig_len - 1;
143 len > (int) sizeof (LONGEST) && p >= (char *) 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 void *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 POINTER_TO_ADDRESS (type, buf);
180 store_signed_integer (void *addr, int len, LONGEST val)
183 unsigned char *startaddr = (unsigned char *) addr;
184 unsigned char *endaddr = startaddr + len;
186 /* Start at the least significant end of the integer, and work towards
187 the most significant. */
188 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
190 for (p = endaddr - 1; p >= startaddr; --p)
198 for (p = startaddr; p < endaddr; ++p)
207 store_unsigned_integer (void *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 (TARGET_BYTE_ORDER == 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 (void *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 ADDRESS_TO_POINTER (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().
253 NOTE: returns NULL if register value is not available. Caller will
254 check return value or die! */
257 value_of_register (int regnum, struct frame_info *frame)
261 struct value *reg_val;
263 char raw_buffer[MAX_REGISTER_SIZE];
266 /* User registers lie completely outside of the range of normal
267 registers. Catch them early so that the target never sees them. */
268 if (regnum >= NUM_REGS + NUM_PSEUDO_REGS)
269 return value_of_user_reg (regnum, frame);
271 frame_register (frame, regnum, &optim, &lval, &addr, &realnum, raw_buffer);
273 /* FIXME: cagney/2002-05-15: This test is just bogus.
275 It indicates that the target failed to supply a value for a
276 register because it was "not available" at this time. Problem
277 is, the target still has the register and so get saved_register()
278 may be returning a value saved on the stack. */
280 if (register_cached (regnum) < 0)
281 return NULL; /* register value not available */
283 reg_val = allocate_value (register_type (current_gdbarch, regnum));
285 memcpy (VALUE_CONTENTS_RAW (reg_val), raw_buffer,
286 register_size (current_gdbarch, regnum));
287 VALUE_LVAL (reg_val) = lval;
288 VALUE_ADDRESS (reg_val) = addr;
289 VALUE_REGNO (reg_val) = regnum;
290 VALUE_OPTIMIZED_OUT (reg_val) = optim;
294 /* Given a pointer of type TYPE in target form in BUF, return the
295 address it represents. */
297 unsigned_pointer_to_address (struct type *type, const void *buf)
299 return extract_unsigned_integer (buf, TYPE_LENGTH (type));
303 signed_pointer_to_address (struct type *type, const void *buf)
305 return extract_signed_integer (buf, TYPE_LENGTH (type));
308 /* Given an address, store it as a pointer of type TYPE in target
311 unsigned_address_to_pointer (struct type *type, void *buf, CORE_ADDR addr)
313 store_unsigned_integer (buf, TYPE_LENGTH (type), addr);
317 address_to_signed_pointer (struct type *type, void *buf, CORE_ADDR addr)
319 store_signed_integer (buf, TYPE_LENGTH (type), addr);
322 /* Will calling read_var_value or locate_var_value on SYM end
323 up caring what frame it is being evaluated relative to? SYM must
326 symbol_read_needs_frame (struct symbol *sym)
328 switch (SYMBOL_CLASS (sym))
330 /* All cases listed explicitly so that gcc -Wall will detect it if
331 we failed to consider one. */
333 case LOC_COMPUTED_ARG:
334 /* FIXME: cagney/2004-01-26: It should be possible to
335 unconditionally call the SYMBOL_OPS method when available.
336 Unfortunately DWARF 2 stores the frame-base (instead of the
337 function) location in a function's symbol. Oops! For the
338 moment enable this when/where applicable. */
339 return SYMBOL_OPS (sym)->read_needs_frame (sym);
345 case LOC_REGPARM_ADDR:
349 case LOC_BASEREG_ARG:
350 case LOC_HP_THREAD_LOCAL_STATIC:
360 /* Getting the address of a label can be done independently of the block,
361 even if some *uses* of that address wouldn't work so well without
365 case LOC_CONST_BYTES:
367 case LOC_OPTIMIZED_OUT:
373 /* Given a struct symbol for a variable,
374 and a stack frame id, read the value of the variable
375 and return a (pointer to a) struct value containing the value.
376 If the variable cannot be found, return a zero pointer.
377 If FRAME is NULL, use the deprecated_selected_frame. */
380 read_var_value (struct symbol *var, struct frame_info *frame)
383 struct type *type = SYMBOL_TYPE (var);
387 v = allocate_value (type);
388 VALUE_LVAL (v) = lval_memory; /* The most likely possibility. */
389 VALUE_BFD_SECTION (v) = SYMBOL_BFD_SECTION (var);
391 len = TYPE_LENGTH (type);
394 /* FIXME drow/2003-09-06: this call to the selected frame should be
395 pushed upwards to the callers. */
397 frame = deprecated_safe_get_selected_frame ();
399 switch (SYMBOL_CLASS (var))
402 /* Put the constant back in target format. */
403 store_signed_integer (VALUE_CONTENTS_RAW (v), len,
404 (LONGEST) SYMBOL_VALUE (var));
405 VALUE_LVAL (v) = not_lval;
409 /* Put the constant back in target format. */
410 if (overlay_debugging)
413 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
414 SYMBOL_BFD_SECTION (var));
415 store_typed_address (VALUE_CONTENTS_RAW (v), type, addr);
418 store_typed_address (VALUE_CONTENTS_RAW (v), type,
419 SYMBOL_VALUE_ADDRESS (var));
420 VALUE_LVAL (v) = not_lval;
423 case LOC_CONST_BYTES:
426 bytes_addr = SYMBOL_VALUE_BYTES (var);
427 memcpy (VALUE_CONTENTS_RAW (v), bytes_addr, len);
428 VALUE_LVAL (v) = not_lval;
433 if (overlay_debugging)
434 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
435 SYMBOL_BFD_SECTION (var));
437 addr = SYMBOL_VALUE_ADDRESS (var);
442 /* The import slot does not have a real address in it from the
443 dynamic loader (dld.sl on HP-UX), if the target hasn't
444 begun execution yet, so check for that. */
447 if (!target_has_execution)
449 Attempt to access variable defined in different shared object or load module when\n\
450 addresses have not been bound by the dynamic loader. Try again when executable is running.");
452 locaddr = SYMBOL_VALUE_ADDRESS (var);
453 loc = value_at (lookup_pointer_type (type), locaddr, NULL);
454 addr = value_as_address (loc);
460 addr = get_frame_args_address (frame);
463 addr += SYMBOL_VALUE (var);
472 argref = get_frame_args_address (frame);
475 argref += SYMBOL_VALUE (var);
476 ref = value_at (lookup_pointer_type (type), argref, NULL);
477 addr = value_as_address (ref);
485 addr = get_frame_locals_address (frame);
486 addr += SYMBOL_VALUE (var);
490 case LOC_BASEREG_ARG:
491 case LOC_HP_THREAD_LOCAL_STATIC:
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 VALUE_OPTIMIZED_OUT (v) = 1;
583 error ("Cannot look up value of a botched symbol.");
587 VALUE_ADDRESS (v) = addr;
592 /* Return a value of type TYPE, stored in register REGNUM, in frame
595 NOTE: returns NULL if register value is not available.
596 Caller will check return value or die! */
599 value_from_register (struct type *type, int regnum, struct frame_info *frame)
601 struct gdbarch *gdbarch = get_frame_arch (frame);
602 struct value *v = allocate_value (type);
603 CHECK_TYPEDEF (type);
605 if (TYPE_LENGTH (type) == 0)
607 /* It doesn't matter much what we return for this: since the
608 length is zero, it could be anything. But if allowed to see
609 a zero-length type, the register-finding loop below will set
610 neither mem_stor nor reg_stor, and then report an internal
613 Zero-length types can legitimately arise from declarations
614 like 'struct {}' (a GCC extension, not valid ISO C). GDB may
615 also create them when it finds bogus debugging information;
616 for example, in GCC 2.95.4 and binutils 2.11.93.0.2, the
617 STABS BINCL->EXCL compression process can create bad type
618 numbers. GDB reads these as TYPE_CODE_UNDEF types, with zero
619 length. (That bug is actually the only known way to get a
620 zero-length value allocated to a register --- which is what
621 it takes to make it here.)
623 We'll just attribute the value to the original register. */
624 VALUE_LVAL (v) = lval_register;
625 VALUE_ADDRESS (v) = regnum;
626 VALUE_REGNO (v) = regnum;
628 else if (CONVERT_REGISTER_P (regnum, type))
630 /* The ISA/ABI need to something weird when obtaining the
631 specified value from this register. It might need to
632 re-order non-adjacent, starting with REGNUM (see MIPS and
633 i386). It might need to convert the [float] register into
634 the corresponding [integer] type (see Alpha). The assumption
635 is that REGISTER_TO_VALUE populates the entire value
636 including the location. */
637 REGISTER_TO_VALUE (frame, regnum, type, VALUE_CONTENTS_RAW (v));
638 VALUE_LVAL (v) = lval_reg_frame_relative;
639 VALUE_FRAME_ID (v) = get_frame_id (frame);
640 VALUE_FRAME_REGNUM (v) = regnum;
645 int mem_stor = 0, reg_stor = 0;
646 int mem_tracking = 1;
647 CORE_ADDR last_addr = 0;
648 CORE_ADDR first_addr = 0;
649 int first_realnum = regnum;
650 int len = TYPE_LENGTH (type);
651 int value_bytes_copied;
653 char *value_bytes = (char *) alloca (len + MAX_REGISTER_SIZE);
655 /* Copy all of the data out, whereever it may be. */
656 for (local_regnum = regnum, value_bytes_copied = 0;
657 value_bytes_copied < len;
658 (value_bytes_copied += register_size (current_gdbarch, local_regnum),
665 frame_register (frame, local_regnum, &optim, &lval, &addr,
666 &realnum, value_bytes + value_bytes_copied);
668 if (register_cached (local_regnum) == -1)
669 return NULL; /* register value not available */
671 if (regnum == local_regnum)
674 first_realnum = realnum;
676 if (lval == lval_register)
682 mem_tracking = (mem_tracking
683 && (regnum == local_regnum
684 || addr == last_addr));
689 /* FIXME: cagney/2003-06-04: Shouldn't this always use
690 lval_reg_frame_relative? If it doesn't and the register's
691 location changes (say after a resume) then this value is
692 going to have wrong information. */
693 if ((reg_stor && mem_stor)
694 || (mem_stor && !mem_tracking))
695 /* Mixed storage; all of the hassle we just went through was
696 for some good purpose. */
698 VALUE_LVAL (v) = lval_reg_frame_relative;
699 VALUE_FRAME_ID (v) = get_frame_id (frame);
700 VALUE_FRAME_REGNUM (v) = regnum;
704 VALUE_LVAL (v) = lval_memory;
705 VALUE_ADDRESS (v) = first_addr;
709 VALUE_LVAL (v) = lval_register;
710 VALUE_ADDRESS (v) = first_addr;
711 VALUE_REGNO (v) = first_realnum;
714 internal_error (__FILE__, __LINE__,
715 "value_from_register: Value not stored anywhere!");
717 VALUE_OPTIMIZED_OUT (v) = optimized;
719 /* Any structure stored in more than one register will always be
720 an integral number of registers. Otherwise, you need to do
721 some fiddling with the last register copied here for little
723 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
724 && len < register_size (current_gdbarch, regnum))
725 /* Big-endian, and we want less than full size. */
726 VALUE_OFFSET (v) = register_size (current_gdbarch, regnum) - len;
728 VALUE_OFFSET (v) = 0;
729 memcpy (VALUE_CONTENTS_RAW (v), value_bytes + VALUE_OFFSET (v), len);
735 /* Given a struct symbol for a variable or function,
736 and a stack frame id,
737 return a (pointer to a) struct value containing the properly typed
741 locate_var_value (struct symbol *var, struct frame_info *frame)
744 struct type *type = SYMBOL_TYPE (var);
745 struct value *lazy_value;
747 /* Evaluate it first; if the result is a memory address, we're fine.
748 Lazy evaluation pays off here. */
750 lazy_value = read_var_value (var, frame);
752 error ("Address of \"%s\" is unknown.", SYMBOL_PRINT_NAME (var));
754 if (VALUE_LAZY (lazy_value)
755 || TYPE_CODE (type) == TYPE_CODE_FUNC)
759 addr = VALUE_ADDRESS (lazy_value);
760 val = value_from_pointer (lookup_pointer_type (type), addr);
761 VALUE_BFD_SECTION (val) = VALUE_BFD_SECTION (lazy_value);
765 /* Not a memory address; check what the problem was. */
766 switch (VALUE_LVAL (lazy_value))
769 gdb_assert (REGISTER_NAME (VALUE_REGNO (lazy_value)) != NULL
770 && *REGISTER_NAME (VALUE_REGNO (lazy_value)) != '\0');
771 error("Address requested for identifier "
772 "\"%s\" which is in register $%s",
773 SYMBOL_PRINT_NAME (var),
774 REGISTER_NAME (VALUE_REGNO (lazy_value)));
777 case lval_reg_frame_relative:
778 gdb_assert (REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)) != NULL
779 && *REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)) != '\0');
780 error("Address requested for identifier "
781 "\"%s\" which is in frame register $%s",
782 SYMBOL_PRINT_NAME (var),
783 REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)));
787 error ("Can't take address of \"%s\" which isn't an lvalue.",
788 SYMBOL_PRINT_NAME (var));
791 return 0; /* For lint -- never reached */