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[binutils.git] / gdb / dwarf2expr.c
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4c2df51b
DJ		 1/* Dwarf2 Expression Evaluator
2 Copyright 2001, 2002, 2003 Free Software Foundation, Inc.
3 Contributed by Daniel Berlin ([email protected])
4
5 This file is part of GDB.
6
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.
11
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.
16
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. */
21
22#include "defs.h"
23#include "symtab.h"
24#include "gdbtypes.h"
25#include "value.h"
26#include "gdbcore.h"
27#include "elf/dwarf2.h"
28#include "dwarf2expr.h"
29
30/* Local prototypes. */
31
32static void execute_stack_op (struct dwarf_expr_context *,
33 unsigned char *, unsigned char *);
34
35/* Create a new context for the expression evaluator. */
36
37struct dwarf_expr_context *
e4adbba9 38new_dwarf_expr_context (void)
4c2df51b
DJ		 39{
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));
44 return retval;
45}
46
47/* Release the memory allocated to CTX. */
48
49void
50free_dwarf_expr_context (struct dwarf_expr_context *ctx)
51{
52 xfree (ctx->stack);
53 xfree (ctx);
54}
55
56/* Expand the memory allocated to CTX's stack to contain at least
57 NEED more elements than are currently used. */
58
59static void
60dwarf_expr_grow_stack (struct dwarf_expr_context *ctx, size_t need)
61{
62 if (ctx->stack_len + need > ctx->stack_allocated)
63 {
64 size_t templen = ctx->stack_len * 2;
65 while (templen < (ctx->stack_len + need))
66 templen *= 2;
67 ctx->stack = xrealloc (ctx->stack,
68 templen * sizeof (CORE_ADDR));
69 ctx->stack_allocated = templen;
70 }
71}
72
73/* Push VALUE onto CTX's stack. */
74
75void
76dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value)
77{
78 dwarf_expr_grow_stack (ctx, 1);
79 ctx->stack[ctx->stack_len++] = value;
80}
81
82/* Pop the top item off of CTX's stack. */
83
84void
85dwarf_expr_pop (struct dwarf_expr_context *ctx)
86{
87 if (ctx->stack_len <= 0)
88 error ("dwarf expression stack underflow");
89 ctx->stack_len--;
90}
91
92/* Retrieve the N'th item on CTX's stack. */
93
94CORE_ADDR
95dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n)
96{
97 if (ctx->stack_len < n)
98 error ("Asked for position %d of stack, stack only has %d elements on it\n",
99 n, ctx->stack_len);
100 return ctx->stack[ctx->stack_len - (1 + n)];
101
102}
103
104/* Evaluate the expression at ADDR (LEN bytes long) using the context
105 CTX. */
106
107void
108dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
109 size_t len)
110{
111 execute_stack_op (ctx, addr, addr + len);
112}
113
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
116 past BUF_END. */
117
a55cc764 118unsigned char *
4c2df51b
DJ		 119read_uleb128 (unsigned char *buf, unsigned char *buf_end, ULONGEST * r)
120{
121 unsigned shift = 0;
122 ULONGEST result = 0;
123 unsigned char byte;
124
125 while (1)
126 {
127 if (buf >= buf_end)
128 error ("read_uleb128: Corrupted DWARF expression.");
129
130 byte = *buf++;
131 result |= (byte & 0x7f) << shift;
132 if ((byte & 0x80) == 0)
133 break;
134 shift += 7;
135 }
136 *r = result;
137 return buf;
138}
139
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
142 past BUF_END. */
143
a55cc764 144unsigned char *
4c2df51b
DJ		 145read_sleb128 (unsigned char *buf, unsigned char *buf_end, LONGEST * r)
146{
147 unsigned shift = 0;
148 LONGEST result = 0;
149 unsigned char byte;
150
151 while (1)
152 {
153 if (buf >= buf_end)
154 error ("read_sleb128: Corrupted DWARF expression.");
155
156 byte = *buf++;
157 result |= (byte & 0x7f) << shift;
158 shift += 7;
159 if ((byte & 0x80) == 0)
160 break;
161 }
162 if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)
163 result |= -(1 << shift);
164
165 *r = result;
166 return buf;
167}
168
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. */
172
173static CORE_ADDR
174read_address (unsigned char *buf, unsigned char *buf_end, int *bytes_read)
175{
176 CORE_ADDR result;
177
178 if (buf_end - buf < TARGET_ADDR_BIT / TARGET_CHAR_BIT)
179 error ("read_address: Corrupted DWARF expression.");
180
181 *bytes_read = TARGET_ADDR_BIT / TARGET_CHAR_BIT;
182 result = extract_address (buf, TARGET_ADDR_BIT / TARGET_CHAR_BIT);
183 return result;
184}
185
186/* Return the type of an address, for unsigned arithmetic. */
187
188static struct type *
189unsigned_address_type (void)
190{
191 switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
192 {
193 case 2:
194 return builtin_type_uint16;
195 case 4:
196 return builtin_type_uint32;
197 case 8:
198 return builtin_type_uint64;
199 default:
200 internal_error (__FILE__, __LINE__,
201 "Unsupported address size.\n");
202 }
203}
204
205/* Return the type of an address, for signed arithmetic. */
206
207static struct type *
208signed_address_type (void)
209{
210 switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
211 {
212 case 2:
213 return builtin_type_int16;
214 case 4:
215 return builtin_type_int32;
216 case 8:
217 return builtin_type_int64;
218 default:
219 internal_error (__FILE__, __LINE__,
220 "Unsupported address size.\n");
221 }
222}
223\f
224/* The engine for the expression evaluator. Using the context in CTX,
225 evaluate the expression between OP_PTR and OP_END. */
226
227static void
228execute_stack_op (struct dwarf_expr_context *ctx, unsigned char *op_ptr,
229 unsigned char *op_end)
230{
231 while (op_ptr < op_end)
232 {
233 enum dwarf_location_atom op = *op_ptr++;
234 CORE_ADDR result, memaddr;
235 ULONGEST uoffset, reg;
236 LONGEST offset;
237 int bytes_read;
238 enum lval_type expr_lval;
239
240 ctx->in_reg = 0;
241
242 switch (op)
243 {
244 case DW_OP_lit0:
245 case DW_OP_lit1:
246 case DW_OP_lit2:
247 case DW_OP_lit3:
248 case DW_OP_lit4:
249 case DW_OP_lit5:
250 case DW_OP_lit6:
251 case DW_OP_lit7:
252 case DW_OP_lit8:
253 case DW_OP_lit9:
254 case DW_OP_lit10:
255 case DW_OP_lit11:
256 case DW_OP_lit12:
257 case DW_OP_lit13:
258 case DW_OP_lit14:
259 case DW_OP_lit15:
260 case DW_OP_lit16:
261 case DW_OP_lit17:
262 case DW_OP_lit18:
263 case DW_OP_lit19:
264 case DW_OP_lit20:
265 case DW_OP_lit21:
266 case DW_OP_lit22:
267 case DW_OP_lit23:
268 case DW_OP_lit24:
269 case DW_OP_lit25:
270 case DW_OP_lit26:
271 case DW_OP_lit27:
272 case DW_OP_lit28:
273 case DW_OP_lit29:
274 case DW_OP_lit30:
275 case DW_OP_lit31:
276 result = op - DW_OP_lit0;
277 break;
278
279 case DW_OP_addr:
280 result = read_address (op_ptr, op_end, &bytes_read);
281 op_ptr += bytes_read;
282 break;
283
284 case DW_OP_const1u:
285 result = extract_unsigned_integer (op_ptr, 1);
286 op_ptr += 1;
287 break;
288 case DW_OP_const1s:
289 result = extract_signed_integer (op_ptr, 1);
290 op_ptr += 1;
291 break;
292 case DW_OP_const2u:
293 result = extract_unsigned_integer (op_ptr, 2);
294 op_ptr += 2;
295 break;
296 case DW_OP_const2s:
297 result = extract_signed_integer (op_ptr, 2);
298 op_ptr += 2;
299 break;
300 case DW_OP_const4u:
301 result = extract_unsigned_integer (op_ptr, 4);
302 op_ptr += 4;
303 break;
304 case DW_OP_const4s:
305 result = extract_signed_integer (op_ptr, 4);
306 op_ptr += 4;
307 break;
308 case DW_OP_const8u:
309 result = extract_unsigned_integer (op_ptr, 8);
310 op_ptr += 8;
311 break;
312 case DW_OP_const8s:
313 result = extract_signed_integer (op_ptr, 8);
314 op_ptr += 8;
315 break;
316 case DW_OP_constu:
317 op_ptr = read_uleb128 (op_ptr, op_end, &uoffset);
318 result = uoffset;
319 break;
320 case DW_OP_consts:
321 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
322 result = offset;
323 break;
324
325 /* The DW_OP_reg operations are required to occur alone in
326 location expressions. */
327 case DW_OP_reg0:
328 case DW_OP_reg1:
329 case DW_OP_reg2:
330 case DW_OP_reg3:
331 case DW_OP_reg4:
332 case DW_OP_reg5:
333 case DW_OP_reg6:
334 case DW_OP_reg7:
335 case DW_OP_reg8:
336 case DW_OP_reg9:
337 case DW_OP_reg10:
338 case DW_OP_reg11:
339 case DW_OP_reg12:
340 case DW_OP_reg13:
341 case DW_OP_reg14:
342 case DW_OP_reg15:
343 case DW_OP_reg16:
344 case DW_OP_reg17:
345 case DW_OP_reg18:
346 case DW_OP_reg19:
347 case DW_OP_reg20:
348 case DW_OP_reg21:
349 case DW_OP_reg22:
350 case DW_OP_reg23:
351 case DW_OP_reg24:
352 case DW_OP_reg25:
353 case DW_OP_reg26:
354 case DW_OP_reg27:
355 case DW_OP_reg28:
356 case DW_OP_reg29:
357 case DW_OP_reg30:
358 case DW_OP_reg31:
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 "
362 "used alone.");
363
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,
368 &memaddr);
369
370 if (expr_lval == lval_register)
371 {
372 ctx->regnum = op - DW_OP_reg0;
373 ctx->in_reg = 1;
374 }
375 else
376 result = memaddr;
377
378 break;
379
380 case DW_OP_regx:
381 op_ptr = read_uleb128 (op_ptr, op_end, &reg);
382 if (op_ptr != op_end)
383 error ("DWARF-2 expression error: DW_OP_reg operations must be "
384 "used alone.");
385
386 result = (ctx->read_reg) (ctx->baton, reg, &expr_lval, &memaddr);
387
388 if (expr_lval == lval_register)
389 {
390 ctx->regnum = reg;
391 ctx->in_reg = 1;
392 }
393 else
394 result = memaddr;
395
396 break;
397
398 case DW_OP_breg0:
399 case DW_OP_breg1:
400 case DW_OP_breg2:
401 case DW_OP_breg3:
402 case DW_OP_breg4:
403 case DW_OP_breg5:
404 case DW_OP_breg6:
405 case DW_OP_breg7:
406 case DW_OP_breg8:
407 case DW_OP_breg9:
408 case DW_OP_breg10:
409 case DW_OP_breg11:
410 case DW_OP_breg12:
411 case DW_OP_breg13:
412 case DW_OP_breg14:
413 case DW_OP_breg15:
414 case DW_OP_breg16:
415 case DW_OP_breg17:
416 case DW_OP_breg18:
417 case DW_OP_breg19:
418 case DW_OP_breg20:
419 case DW_OP_breg21:
420 case DW_OP_breg22:
421 case DW_OP_breg23:
422 case DW_OP_breg24:
423 case DW_OP_breg25:
424 case DW_OP_breg26:
425 case DW_OP_breg27:
426 case DW_OP_breg28:
427 case DW_OP_breg29:
428 case DW_OP_breg30:
429 case DW_OP_breg31:
430 {
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);
434 result += offset;
435 }
436 break;
437 case DW_OP_bregx:
438 {
439 op_ptr = read_uleb128 (op_ptr, op_end, &reg);
440 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
441 result = (ctx->read_reg) (ctx->baton, reg, &expr_lval, &memaddr);
442 result += offset;
443 }
444 break;
445 case DW_OP_fbreg:
446 {
447 unsigned char *datastart;
448 size_t datalen;
449 unsigned int before_stack_len;
450
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
455 call put there. */
456 before_stack_len = ctx->stack_len;
da62e633
AC		 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. */
4c2df51b
DJ		 460 (ctx->get_frame_base) (ctx->baton, &datastart, &datalen);
461 dwarf_expr_eval (ctx, datastart, datalen);
462 result = dwarf_expr_fetch (ctx, 0);
463 if (! ctx->in_reg)
464 {
465 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
466 int bytes_read;
467
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,
472 &bytes_read);
473 }
474 result = result + offset;
475 ctx->stack_len = before_stack_len;
476 ctx->in_reg = 0;
477 }
478 break;
479 case DW_OP_dup:
480 result = dwarf_expr_fetch (ctx, 0);
481 break;
482
483 case DW_OP_drop:
484 dwarf_expr_pop (ctx);
485 goto no_push;
486
487 case DW_OP_pick:
488 offset = *op_ptr++;
489 result = dwarf_expr_fetch (ctx, offset);
490 break;
491
492 case DW_OP_over:
493 result = dwarf_expr_fetch (ctx, 1);
494 break;
495
496 case DW_OP_rot:
497 {
498 CORE_ADDR t1, t2, t3;
499
500 if (ctx->stack_len < 3)
501 error ("Not enough elements for DW_OP_rot. Need 3, have %d\n",
502 ctx->stack_len);
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;
509 goto no_push;
510 }
511
512 case DW_OP_deref:
513 case DW_OP_deref_size:
514 case DW_OP_abs:
515 case DW_OP_neg:
516 case DW_OP_not:
517 case DW_OP_plus_uconst:
518 /* Unary operations. */
519 result = dwarf_expr_fetch (ctx, 0);
520 dwarf_expr_pop (ctx);
521
522 switch (op)
523 {
524 case DW_OP_deref:
525 {
526 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
527 int bytes_read;
528
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,
533 &bytes_read);
534 }
535 break;
536
537 case DW_OP_deref_size:
538 {
539 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
540 int bytes_read;
541
542 (ctx->read_mem) (ctx->baton, buf, result, *op_ptr++);
543 result = read_address (buf,
544 buf + TARGET_ADDR_BIT / TARGET_CHAR_BIT,
545 &bytes_read);
546 }
547 break;
548
549 case DW_OP_abs:
550 if ((signed int) result < 0)
551 result = -result;
552 break;
553 case DW_OP_neg:
554 result = -result;
555 break;
556 case DW_OP_not:
557 result = ~result;
558 break;
559 case DW_OP_plus_uconst:
560 op_ptr = read_uleb128 (op_ptr, op_end, &reg);
561 result += reg;
562 break;
563 }
564 break;
565
566 case DW_OP_and:
567 case DW_OP_div:
568 case DW_OP_minus:
569 case DW_OP_mod:
570 case DW_OP_mul:
571 case DW_OP_or:
572 case DW_OP_plus:
573 case DW_OP_shl:
574 case DW_OP_shr:
575 case DW_OP_shra:
576 case DW_OP_xor:
577 case DW_OP_le:
578 case DW_OP_ge:
579 case DW_OP_eq:
580 case DW_OP_lt:
581 case DW_OP_gt:
582 case DW_OP_ne:
583 {
584 /* Binary operations. Use the value engine to do computations in
585 the right width. */
586 CORE_ADDR first, second;
587 enum exp_opcode binop;
588 struct value *val1, *val2;
589
590 second = dwarf_expr_fetch (ctx, 0);
591 dwarf_expr_pop (ctx);
592
593 first = dwarf_expr_fetch (ctx, 1);
594 dwarf_expr_pop (ctx);
595
596 val1 = value_from_longest (unsigned_address_type (), first);
597 val2 = value_from_longest (unsigned_address_type (), second);
598
599 switch (op)
600 {
601 case DW_OP_and:
602 binop = BINOP_BITWISE_AND;
603 break;
604 case DW_OP_div:
605 binop = BINOP_DIV;
606 case DW_OP_minus:
607 binop = BINOP_SUB;
608 break;
609 case DW_OP_mod:
610 binop = BINOP_MOD;
611 break;
612 case DW_OP_mul:
613 binop = BINOP_MUL;
614 break;
615 case DW_OP_or:
616 binop = BINOP_BITWISE_IOR;
617 break;
618 case DW_OP_plus:
619 binop = BINOP_ADD;
620 break;
621 case DW_OP_shl:
622 binop = BINOP_LSH;
623 break;
624 case DW_OP_shr:
625 binop = BINOP_RSH;
626 case DW_OP_shra:
627 binop = BINOP_RSH;
628 val1 = value_from_longest (signed_address_type (), first);
629 break;
630 case DW_OP_xor:
631 binop = BINOP_BITWISE_XOR;
632 break;
633 case DW_OP_le:
634 binop = BINOP_LEQ;
635 break;
636 case DW_OP_ge:
637 binop = BINOP_GEQ;
638 break;
639 case DW_OP_eq:
640 binop = BINOP_EQUAL;
641 break;
642 case DW_OP_lt:
643 binop = BINOP_LESS;
644 break;
645 case DW_OP_gt:
646 binop = BINOP_GTR;
647 break;
648 case DW_OP_ne:
649 binop = BINOP_NOTEQUAL;
650 break;
651 default:
652 internal_error (__FILE__, __LINE__,
653 "Can't be reached.");
654 }
655 result = value_as_long (value_binop (val1, val2, binop));
656 }
657 break;
658
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);
663 break;
664
665 case DW_OP_skip:
666 offset = extract_signed_integer (op_ptr, 2);
667 op_ptr += 2;
668 op_ptr += offset;
669 goto no_push;
670
671 case DW_OP_bra:
672 offset = extract_signed_integer (op_ptr, 2);
673 op_ptr += 2;
674 if (dwarf_expr_fetch (ctx, 0) != 0)
675 op_ptr += offset;
676 dwarf_expr_pop (ctx);
677 goto no_push;
678
679 case DW_OP_nop:
680 goto no_push;
681
682 default:
683 error ("Unhandled dwarf expression opcode");
684 }
685
686 /* Most things push a result value. */
687 dwarf_expr_push (ctx, result);
688 no_push:;
689 }
690}
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