1 /* Dwarf2 Expression Evaluator
2 Copyright 2001, 2002, 2003 Free Software Foundation, Inc.
3 Contributed by Daniel Berlin (dan@dberlin.org)
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
27 #include "elf/dwarf2.h"
28 #include "dwarf2expr.h"
30 /* Local prototypes. */
32 static void execute_stack_op (struct dwarf_expr_context
*,
33 unsigned char *, unsigned char *);
35 /* Create a new context for the expression evaluator. */
37 struct dwarf_expr_context
*
38 new_dwarf_expr_context (void)
40 struct dwarf_expr_context
*retval
;
41 retval
= xcalloc (1, sizeof (struct dwarf_expr_context
));
42 retval
->stack_len
= 10;
43 retval
->stack
= xmalloc (10 * sizeof (CORE_ADDR
));
47 /* Release the memory allocated to CTX. */
50 free_dwarf_expr_context (struct dwarf_expr_context
*ctx
)
56 /* Expand the memory allocated to CTX's stack to contain at least
57 NEED more elements than are currently used. */
60 dwarf_expr_grow_stack (struct dwarf_expr_context
*ctx
, size_t need
)
62 if (ctx
->stack_len
+ need
> ctx
->stack_allocated
)
64 size_t templen
= ctx
->stack_len
* 2;
65 while (templen
< (ctx
->stack_len
+ need
))
67 ctx
->stack
= xrealloc (ctx
->stack
,
68 templen
* sizeof (CORE_ADDR
));
69 ctx
->stack_allocated
= templen
;
73 /* Push VALUE onto CTX's stack. */
76 dwarf_expr_push (struct dwarf_expr_context
*ctx
, CORE_ADDR value
)
78 dwarf_expr_grow_stack (ctx
, 1);
79 ctx
->stack
[ctx
->stack_len
++] = value
;
82 /* Pop the top item off of CTX's stack. */
85 dwarf_expr_pop (struct dwarf_expr_context
*ctx
)
87 if (ctx
->stack_len
<= 0)
88 error ("dwarf expression stack underflow");
92 /* Retrieve the N'th item on CTX's stack. */
95 dwarf_expr_fetch (struct dwarf_expr_context
*ctx
, int n
)
97 if (ctx
->stack_len
< n
)
98 error ("Asked for position %d of stack, stack only has %d elements on it\n",
100 return ctx
->stack
[ctx
->stack_len
- (1 + n
)];
104 /* Evaluate the expression at ADDR (LEN bytes long) using the context
108 dwarf_expr_eval (struct dwarf_expr_context
*ctx
, unsigned char *addr
,
111 execute_stack_op (ctx
, addr
, addr
+ len
);
114 /* Decode the unsigned LEB128 constant at BUF into the variable pointed to
115 by R, and return the new value of BUF. Verify that it doesn't extend
119 read_uleb128 (unsigned char *buf
, unsigned char *buf_end
, ULONGEST
* r
)
128 error ("read_uleb128: Corrupted DWARF expression.");
131 result
|= (byte
& 0x7f) << shift
;
132 if ((byte
& 0x80) == 0)
140 /* Decode the signed LEB128 constant at BUF into the variable pointed to
141 by R, and return the new value of BUF. Verify that it doesn't extend
145 read_sleb128 (unsigned char *buf
, unsigned char *buf_end
, LONGEST
* r
)
154 error ("read_sleb128: Corrupted DWARF expression.");
157 result
|= (byte
& 0x7f) << shift
;
159 if ((byte
& 0x80) == 0)
162 if (shift
< (sizeof (*r
) * 8) && (byte
& 0x40) != 0)
163 result
|= -(1 << shift
);
169 /* Read an address from BUF, and verify that it doesn't extend past
170 BUF_END. The address is returned, and *BYTES_READ is set to the
171 number of bytes read from BUF. */
174 read_address (unsigned char *buf
, unsigned char *buf_end
, int *bytes_read
)
178 if (buf_end
- buf
< TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
)
179 error ("read_address: Corrupted DWARF expression.");
181 *bytes_read
= TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
;
182 result
= extract_address (buf
, TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
);
186 /* Return the type of an address, for unsigned arithmetic. */
189 unsigned_address_type (void)
191 switch (TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
)
194 return builtin_type_uint16
;
196 return builtin_type_uint32
;
198 return builtin_type_uint64
;
200 internal_error (__FILE__
, __LINE__
,
201 "Unsupported address size.\n");
205 /* Return the type of an address, for signed arithmetic. */
208 signed_address_type (void)
210 switch (TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
)
213 return builtin_type_int16
;
215 return builtin_type_int32
;
217 return builtin_type_int64
;
219 internal_error (__FILE__
, __LINE__
,
220 "Unsupported address size.\n");
224 /* The engine for the expression evaluator. Using the context in CTX,
225 evaluate the expression between OP_PTR and OP_END. */
228 execute_stack_op (struct dwarf_expr_context
*ctx
, unsigned char *op_ptr
,
229 unsigned char *op_end
)
231 while (op_ptr
< op_end
)
233 enum dwarf_location_atom op
= *op_ptr
++;
234 CORE_ADDR result
, memaddr
;
235 ULONGEST uoffset
, reg
;
238 enum lval_type expr_lval
;
276 result
= op
- DW_OP_lit0
;
280 result
= read_address (op_ptr
, op_end
, &bytes_read
);
281 op_ptr
+= bytes_read
;
285 result
= extract_unsigned_integer (op_ptr
, 1);
289 result
= extract_signed_integer (op_ptr
, 1);
293 result
= extract_unsigned_integer (op_ptr
, 2);
297 result
= extract_signed_integer (op_ptr
, 2);
301 result
= extract_unsigned_integer (op_ptr
, 4);
305 result
= extract_signed_integer (op_ptr
, 4);
309 result
= extract_unsigned_integer (op_ptr
, 8);
313 result
= extract_signed_integer (op_ptr
, 8);
317 op_ptr
= read_uleb128 (op_ptr
, op_end
, &uoffset
);
321 op_ptr
= read_sleb128 (op_ptr
, op_end
, &offset
);
325 /* The DW_OP_reg operations are required to occur alone in
326 location expressions. */
359 /* NOTE: in the presence of DW_OP_piece this check is incorrect. */
360 if (op_ptr
!= op_end
)
361 error ("DWARF-2 expression error: DW_OP_reg operations must be "
364 /* FIXME drow/2003-02-21: This call to read_reg could be pushed
365 into the evaluator's caller by changing the semantics for in_reg.
366 Then we wouldn't need to return an lval_type and a memaddr. */
367 result
= (ctx
->read_reg
) (ctx
->baton
, op
- DW_OP_reg0
, &expr_lval
,
370 if (expr_lval
== lval_register
)
372 ctx
->regnum
= op
- DW_OP_reg0
;
381 op_ptr
= read_uleb128 (op_ptr
, op_end
, ®
);
382 if (op_ptr
!= op_end
)
383 error ("DWARF-2 expression error: DW_OP_reg operations must be "
386 result
= (ctx
->read_reg
) (ctx
->baton
, reg
, &expr_lval
, &memaddr
);
388 if (expr_lval
== lval_register
)
431 op_ptr
= read_sleb128 (op_ptr
, op_end
, &offset
);
432 result
= (ctx
->read_reg
) (ctx
->baton
, op
- DW_OP_breg0
,
433 &expr_lval
, &memaddr
);
439 op_ptr
= read_uleb128 (op_ptr
, op_end
, ®
);
440 op_ptr
= read_sleb128 (op_ptr
, op_end
, &offset
);
441 result
= (ctx
->read_reg
) (ctx
->baton
, reg
, &expr_lval
, &memaddr
);
447 unsigned char *datastart
;
449 unsigned int before_stack_len
;
451 op_ptr
= read_sleb128 (op_ptr
, op_end
, &offset
);
452 /* Rather than create a whole new context, we simply
453 record the stack length before execution, then reset it
454 afterwards, effectively erasing whatever the recursive
456 before_stack_len
= ctx
->stack_len
;
457 /* FIXME: cagney/2003-03-26: This code should be using
458 get_frame_base_address(), and then implement a dwarf2
459 specific this_base method. */
460 (ctx
->get_frame_base
) (ctx
->baton
, &datastart
, &datalen
);
461 dwarf_expr_eval (ctx
, datastart
, datalen
);
462 result
= dwarf_expr_fetch (ctx
, 0);
465 char *buf
= alloca (TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
);
468 (ctx
->read_mem
) (ctx
->baton
, buf
, result
,
469 TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
);
470 result
= read_address (buf
,
471 buf
+ TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
,
474 result
= result
+ offset
;
475 ctx
->stack_len
= before_stack_len
;
480 result
= dwarf_expr_fetch (ctx
, 0);
484 dwarf_expr_pop (ctx
);
489 result
= dwarf_expr_fetch (ctx
, offset
);
493 result
= dwarf_expr_fetch (ctx
, 1);
498 CORE_ADDR t1
, t2
, t3
;
500 if (ctx
->stack_len
< 3)
501 error ("Not enough elements for DW_OP_rot. Need 3, have %d\n",
503 t1
= ctx
->stack
[ctx
->stack_len
- 1];
504 t2
= ctx
->stack
[ctx
->stack_len
- 2];
505 t3
= ctx
->stack
[ctx
->stack_len
- 3];
506 ctx
->stack
[ctx
->stack_len
- 1] = t2
;
507 ctx
->stack
[ctx
->stack_len
- 2] = t3
;
508 ctx
->stack
[ctx
->stack_len
- 3] = t1
;
513 case DW_OP_deref_size
:
517 case DW_OP_plus_uconst
:
518 /* Unary operations. */
519 result
= dwarf_expr_fetch (ctx
, 0);
520 dwarf_expr_pop (ctx
);
526 char *buf
= alloca (TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
);
529 (ctx
->read_mem
) (ctx
->baton
, buf
, result
,
530 TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
);
531 result
= read_address (buf
,
532 buf
+ TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
,
537 case DW_OP_deref_size
:
539 char *buf
= alloca (TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
);
542 (ctx
->read_mem
) (ctx
->baton
, buf
, result
, *op_ptr
++);
543 result
= read_address (buf
,
544 buf
+ TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
,
550 if ((signed int) result
< 0)
559 case DW_OP_plus_uconst
:
560 op_ptr
= read_uleb128 (op_ptr
, op_end
, ®
);
584 /* Binary operations. Use the value engine to do computations in
586 CORE_ADDR first
, second
;
587 enum exp_opcode binop
;
588 struct value
*val1
, *val2
;
590 second
= dwarf_expr_fetch (ctx
, 0);
591 dwarf_expr_pop (ctx
);
593 first
= dwarf_expr_fetch (ctx
, 1);
594 dwarf_expr_pop (ctx
);
596 val1
= value_from_longest (unsigned_address_type (), first
);
597 val2
= value_from_longest (unsigned_address_type (), second
);
602 binop
= BINOP_BITWISE_AND
;
616 binop
= BINOP_BITWISE_IOR
;
628 val1
= value_from_longest (signed_address_type (), first
);
631 binop
= BINOP_BITWISE_XOR
;
649 binop
= BINOP_NOTEQUAL
;
652 internal_error (__FILE__
, __LINE__
,
653 "Can't be reached.");
655 result
= value_as_long (value_binop (val1
, val2
, binop
));
659 case DW_OP_GNU_push_tls_address
:
660 result
= dwarf_expr_fetch (ctx
, 0);
661 dwarf_expr_pop (ctx
);
662 result
= (ctx
->get_tls_address
) (ctx
->baton
, result
);
666 offset
= extract_signed_integer (op_ptr
, 2);
672 offset
= extract_signed_integer (op_ptr
, 2);
674 if (dwarf_expr_fetch (ctx
, 0) != 0)
676 dwarf_expr_pop (ctx
);
683 error ("Unhandled dwarf expression opcode");
686 /* Most things push a result value. */
687 dwarf_expr_push (ctx
, result
);