aboutsummaryrefslogtreecommitdiff
path: root/gdb/dwarf2expr.c
blob: cf00929e2251f00ce6d4ba723ec5a644c4e9d709 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
/* Dwarf2 Expression Evaluator
   Copyright 2001, 2002, 2003 Free Software Foundation, Inc.
   Contributed by Daniel Berlin (dan@dberlin.org)

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "value.h"
#include "gdbcore.h"
#include "elf/dwarf2.h"
#include "dwarf2expr.h"

/* Local prototypes.  */

static void execute_stack_op (struct dwarf_expr_context *,
			      unsigned char *, unsigned char *);

/* Create a new context for the expression evaluator.  */

struct dwarf_expr_context *
new_dwarf_expr_context (void)
{
  struct dwarf_expr_context *retval;
  retval = xcalloc (1, sizeof (struct dwarf_expr_context));
  retval->stack_len = 0;
  retval->stack_allocated = 10;
  retval->stack = xmalloc (retval->stack_allocated * sizeof (CORE_ADDR));
  return retval;
}

/* Release the memory allocated to CTX.  */

void
free_dwarf_expr_context (struct dwarf_expr_context *ctx)
{
  xfree (ctx->stack);
  xfree (ctx);
}

/* Expand the memory allocated to CTX's stack to contain at least
   NEED more elements than are currently used.  */

static void
dwarf_expr_grow_stack (struct dwarf_expr_context *ctx, size_t need)
{
  if (ctx->stack_len + need > ctx->stack_allocated)
    {
      size_t newlen = ctx->stack_len + need + 10;
      ctx->stack = xrealloc (ctx->stack,
			     newlen * sizeof (CORE_ADDR));
      ctx->stack_allocated = newlen;
    }
}

/* Push VALUE onto CTX's stack.  */

void
dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value)
{
  dwarf_expr_grow_stack (ctx, 1);
  ctx->stack[ctx->stack_len++] = value;
}

/* Pop the top item off of CTX's stack.  */

void
dwarf_expr_pop (struct dwarf_expr_context *ctx)
{
  if (ctx->stack_len <= 0)
    error ("dwarf expression stack underflow");
  ctx->stack_len--;
}

/* Retrieve the N'th item on CTX's stack.  */

CORE_ADDR
dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n)
{
  if (ctx->stack_len < n)
     error ("Asked for position %d of stack, stack only has %d elements on it\n",
	    n, ctx->stack_len);
  return ctx->stack[ctx->stack_len - (1 + n)];

}

/* Evaluate the expression at ADDR (LEN bytes long) using the context
   CTX.  */

void
dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
		 size_t len)
{
  execute_stack_op (ctx, addr, addr + len);
}

/* Decode the unsigned LEB128 constant at BUF into the variable pointed to
   by R, and return the new value of BUF.  Verify that it doesn't extend
   past BUF_END.  */

unsigned char *
read_uleb128 (unsigned char *buf, unsigned char *buf_end, ULONGEST * r)
{
  unsigned shift = 0;
  ULONGEST result = 0;
  unsigned char byte;

  while (1)
    {
      if (buf >= buf_end)
	error ("read_uleb128: Corrupted DWARF expression.");

      byte = *buf++;
      result |= (byte & 0x7f) << shift;
      if ((byte & 0x80) == 0)
	break;
      shift += 7;
    }
  *r = result;
  return buf;
}

/* Decode the signed LEB128 constant at BUF into the variable pointed to
   by R, and return the new value of BUF.  Verify that it doesn't extend
   past BUF_END.  */

unsigned char *
read_sleb128 (unsigned char *buf, unsigned char *buf_end, LONGEST * r)
{
  unsigned shift = 0;
  LONGEST result = 0;
  unsigned char byte;

  while (1)
    {
      if (buf >= buf_end)
	error ("read_sleb128: Corrupted DWARF expression.");

      byte = *buf++;
      result |= (byte & 0x7f) << shift;
      shift += 7;
      if ((byte & 0x80) == 0)
	break;
    }
  if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)
    result |= -(1 << shift);

  *r = result;
  return buf;
}

/* Read an address from BUF, and verify that it doesn't extend past
   BUF_END.  The address is returned, and *BYTES_READ is set to the
   number of bytes read from BUF.  */

CORE_ADDR
dwarf2_read_address (unsigned char *buf, unsigned char *buf_end, int *bytes_read)
{
  CORE_ADDR result;

  if (buf_end - buf < TARGET_ADDR_BIT / TARGET_CHAR_BIT)
    error ("dwarf2_read_address: Corrupted DWARF expression.");

  *bytes_read = TARGET_ADDR_BIT / TARGET_CHAR_BIT;
  /* NOTE: cagney/2003-05-22: This extract is assuming that a DWARF 2
     address is always unsigned.  That may or may not be true.  */
  result = extract_unsigned_integer (buf, TARGET_ADDR_BIT / TARGET_CHAR_BIT);
  return result;
}

/* Return the type of an address, for unsigned arithmetic.  */

static struct type *
unsigned_address_type (void)
{
  switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
    {
    case 2:
      return builtin_type_uint16;
    case 4:
      return builtin_type_uint32;
    case 8:
      return builtin_type_uint64;
    default:
      internal_error (__FILE__, __LINE__,
		      "Unsupported address size.\n");
    }
}

/* Return the type of an address, for signed arithmetic.  */

static struct type *
signed_address_type (void)
{
  switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
    {
    case 2:
      return builtin_type_int16;
    case 4:
      return builtin_type_int32;
    case 8:
      return builtin_type_int64;
    default:
      internal_error (__FILE__, __LINE__,
		      "Unsupported address size.\n");
    }
}

/* The engine for the expression evaluator.  Using the context in CTX,
   evaluate the expression between OP_PTR and OP_END.  */

static void
execute_stack_op (struct dwarf_expr_context *ctx, unsigned char *op_ptr,
		  unsigned char *op_end)
{
  ctx->in_reg = 0;

  while (op_ptr < op_end)
    {
      enum dwarf_location_atom op = *op_ptr++;
      CORE_ADDR result;
      ULONGEST uoffset, reg;
      LONGEST offset;
      int bytes_read;

      switch (op)
	{
	case DW_OP_lit0:
	case DW_OP_lit1:
	case DW_OP_lit2:
	case DW_OP_lit3:
	case DW_OP_lit4:
	case DW_OP_lit5:
	case DW_OP_lit6:
	case DW_OP_lit7:
	case DW_OP_lit8:
	case DW_OP_lit9:
	case DW_OP_lit10:
	case DW_OP_lit11:
	case DW_OP_lit12:
	case DW_OP_lit13:
	case DW_OP_lit14:
	case DW_OP_lit15:
	case DW_OP_lit16:
	case DW_OP_lit17:
	case DW_OP_lit18:
	case DW_OP_lit19:
	case DW_OP_lit20:
	case DW_OP_lit21:
	case DW_OP_lit22:
	case DW_OP_lit23:
	case DW_OP_lit24:
	case DW_OP_lit25:
	case DW_OP_lit26:
	case DW_OP_lit27:
	case DW_OP_lit28:
	case DW_OP_lit29:
	case DW_OP_lit30:
	case DW_OP_lit31:
	  result = op - DW_OP_lit0;
	  break;

	case DW_OP_addr:
	  result = dwarf2_read_address (op_ptr, op_end, &bytes_read);
	  op_ptr += bytes_read;
	  break;

	case DW_OP_const1u:
	  result = extract_unsigned_integer (op_ptr, 1);
	  op_ptr += 1;
	  break;
	case DW_OP_const1s:
	  result = extract_signed_integer (op_ptr, 1);
	  op_ptr += 1;
	  break;
	case DW_OP_const2u:
	  result = extract_unsigned_integer (op_ptr, 2);
	  op_ptr += 2;
	  break;
	case DW_OP_const2s:
	  result = extract_signed_integer (op_ptr, 2);
	  op_ptr += 2;
	  break;
	case DW_OP_const4u:
	  result = extract_unsigned_integer (op_ptr, 4);
	  op_ptr += 4;
	  break;
	case DW_OP_const4s:
	  result = extract_signed_integer (op_ptr, 4);
	  op_ptr += 4;
	  break;
	case DW_OP_const8u:
	  result = extract_unsigned_integer (op_ptr, 8);
	  op_ptr += 8;
	  break;
	case DW_OP_const8s:
	  result = extract_signed_integer (op_ptr, 8);
	  op_ptr += 8;
	  break;
	case DW_OP_constu:
	  op_ptr = read_uleb128 (op_ptr, op_end, &uoffset);
	  result = uoffset;
	  break;
	case DW_OP_consts:
	  op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	  result = offset;
	  break;

	/* The DW_OP_reg operations are required to occur alone in
	   location expressions.  */
	case DW_OP_reg0:
	case DW_OP_reg1:
	case DW_OP_reg2:
	case DW_OP_reg3:
	case DW_OP_reg4:
	case DW_OP_reg5:
	case DW_OP_reg6:
	case DW_OP_reg7:
	case DW_OP_reg8:
	case DW_OP_reg9:
	case DW_OP_reg10:
	case DW_OP_reg11:
	case DW_OP_reg12:
	case DW_OP_reg13:
	case DW_OP_reg14:
	case DW_OP_reg15:
	case DW_OP_reg16:
	case DW_OP_reg17:
	case DW_OP_reg18:
	case DW_OP_reg19:
	case DW_OP_reg20:
	case DW_OP_reg21:
	case DW_OP_reg22:
	case DW_OP_reg23:
	case DW_OP_reg24:
	case DW_OP_reg25:
	case DW_OP_reg26:
	case DW_OP_reg27:
	case DW_OP_reg28:
	case DW_OP_reg29:
	case DW_OP_reg30:
	case DW_OP_reg31:
	  if (op_ptr != op_end && *op_ptr != DW_OP_piece)
	    error ("DWARF-2 expression error: DW_OP_reg operations must be "
		   "used either alone or in conjuction with DW_OP_piece.");

	  result = op - DW_OP_reg0;
	  ctx->in_reg = 1;

	  break;

	case DW_OP_regx:
	  op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	  if (op_ptr != op_end && *op_ptr != DW_OP_piece)
	    error ("DWARF-2 expression error: DW_OP_reg operations must be "
		   "used either alone or in conjuction with DW_OP_piece.");

	  result = reg;
	  ctx->in_reg = 1;
	  break;

	case DW_OP_breg0:
	case DW_OP_breg1:
	case DW_OP_breg2:
	case DW_OP_breg3:
	case DW_OP_breg4:
	case DW_OP_breg5:
	case DW_OP_breg6:
	case DW_OP_breg7:
	case DW_OP_breg8:
	case DW_OP_breg9:
	case DW_OP_breg10:
	case DW_OP_breg11:
	case DW_OP_breg12:
	case DW_OP_breg13:
	case DW_OP_breg14:
	case DW_OP_breg15:
	case DW_OP_breg16:
	case DW_OP_breg17:
	case DW_OP_breg18:
	case DW_OP_breg19:
	case DW_OP_breg20:
	case DW_OP_breg21:
	case DW_OP_breg22:
	case DW_OP_breg23:
	case DW_OP_breg24:
	case DW_OP_breg25:
	case DW_OP_breg26:
	case DW_OP_breg27:
	case DW_OP_breg28:
	case DW_OP_breg29:
	case DW_OP_breg30:
	case DW_OP_breg31:
	  {
	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    result = (ctx->read_reg) (ctx->baton, op - DW_OP_breg0);
	    result += offset;
	  }
	  break;
	case DW_OP_bregx:
	  {
	    op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    result = (ctx->read_reg) (ctx->baton, reg);
	    result += offset;
	  }
	  break;
	case DW_OP_fbreg:
	  {
	    unsigned char *datastart;
	    size_t datalen;
	    unsigned int before_stack_len;

	    op_ptr = read_sleb128 (op_ptr, op_end, &offset);
	    /* Rather than create a whole new context, we simply
	       record the stack length before execution, then reset it
	       afterwards, effectively erasing whatever the recursive
	       call put there.  */
	    before_stack_len = ctx->stack_len;
	    /* FIXME: cagney/2003-03-26: This code should be using
               get_frame_base_address(), and then implement a dwarf2
               specific this_base method.  */
	    (ctx->get_frame_base) (ctx->baton, &datastart, &datalen);
	    dwarf_expr_eval (ctx, datastart, datalen);
	    result = dwarf_expr_fetch (ctx, 0);
	    if (ctx->in_reg)
	      result = (ctx->read_reg) (ctx->baton, result);
	    result = result + offset;
	    ctx->stack_len = before_stack_len;
	    ctx->in_reg = 0;
	  }
	  break;
	case DW_OP_dup:
	  result = dwarf_expr_fetch (ctx, 0);
	  break;

	case DW_OP_drop:
	  dwarf_expr_pop (ctx);
	  goto no_push;

	case DW_OP_pick:
	  offset = *op_ptr++;
	  result = dwarf_expr_fetch (ctx, offset);
	  break;

	case DW_OP_over:
	  result = dwarf_expr_fetch (ctx, 1);
	  break;

	case DW_OP_rot:
	  {
	    CORE_ADDR t1, t2, t3;

	    if (ctx->stack_len < 3)
	       error ("Not enough elements for DW_OP_rot. Need 3, have %d\n",
		      ctx->stack_len);
	    t1 = ctx->stack[ctx->stack_len - 1];
	    t2 = ctx->stack[ctx->stack_len - 2];
	    t3 = ctx->stack[ctx->stack_len - 3];
	    ctx->stack[ctx->stack_len - 1] = t2;
	    ctx->stack[ctx->stack_len - 2] = t3;
	    ctx->stack[ctx->stack_len - 3] = t1;
	    goto no_push;
	  }

	case DW_OP_deref:
	case DW_OP_deref_size:
	case DW_OP_abs:
	case DW_OP_neg:
	case DW_OP_not:
	case DW_OP_plus_uconst:
	  /* Unary operations.  */
	  result = dwarf_expr_fetch (ctx, 0);
	  dwarf_expr_pop (ctx);

	  switch (op)
	    {
	    case DW_OP_deref:
	      {
		char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
		int bytes_read;

		(ctx->read_mem) (ctx->baton, buf, result,
				 TARGET_ADDR_BIT / TARGET_CHAR_BIT);
		result = dwarf2_read_address (buf,
					      buf + (TARGET_ADDR_BIT
						     / TARGET_CHAR_BIT),
					      &bytes_read);
	      }
	      break;

	    case DW_OP_deref_size:
	      {
		char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
		int bytes_read;

		(ctx->read_mem) (ctx->baton, buf, result, *op_ptr++);
		result = dwarf2_read_address (buf,
					      buf + (TARGET_ADDR_BIT
						     / TARGET_CHAR_BIT),
					      &bytes_read);
	      }
	      break;

	    case DW_OP_abs:
	      if ((signed int) result < 0)
		result = -result;
	      break;
	    case DW_OP_neg:
	      result = -result;
	      break;
	    case DW_OP_not:
	      result = ~result;
	      break;
	    case DW_OP_plus_uconst:
	      op_ptr = read_uleb128 (op_ptr, op_end, &reg);
	      result += reg;
	      break;
	    }
	  break;

	case DW_OP_and:
	case DW_OP_div:
	case DW_OP_minus:
	case DW_OP_mod:
	case DW_OP_mul:
	case DW_OP_or:
	case DW_OP_plus:
	case DW_OP_shl:
	case DW_OP_shr:
	case DW_OP_shra:
	case DW_OP_xor:
	case DW_OP_le:
	case DW_OP_ge:
	case DW_OP_eq:
	case DW_OP_lt:
	case DW_OP_gt:
	case DW_OP_ne:
	  {
	    /* Binary operations.  Use the value engine to do computations in
	       the right width.  */
	    CORE_ADDR first, second;
	    enum exp_opcode binop;
	    struct value *val1, *val2;

	    second = dwarf_expr_fetch (ctx, 0);
	    dwarf_expr_pop (ctx);

	    first = dwarf_expr_fetch (ctx, 1);
	    dwarf_expr_pop (ctx);

	    val1 = value_from_longest (unsigned_address_type (), first);
	    val2 = value_from_longest (unsigned_address_type (), second);

	    switch (op)
	      {
	      case DW_OP_and:
		binop = BINOP_BITWISE_AND;
		break;
	      case DW_OP_div:
		binop = BINOP_DIV;
	      case DW_OP_minus:
		binop = BINOP_SUB;
		break;
	      case DW_OP_mod:
		binop = BINOP_MOD;
		break;
	      case DW_OP_mul:
		binop = BINOP_MUL;
		break;
	      case DW_OP_or:
		binop = BINOP_BITWISE_IOR;
		break;
	      case DW_OP_plus:
		binop = BINOP_ADD;
		break;
	      case DW_OP_shl:
		binop = BINOP_LSH;
		break;
	      case DW_OP_shr:
		binop = BINOP_RSH;
	      case DW_OP_shra:
		binop = BINOP_RSH;
		val1 = value_from_longest (signed_address_type (), first);
		break;
	      case DW_OP_xor:
		binop = BINOP_BITWISE_XOR;
		break;
	      case DW_OP_le:
		binop = BINOP_LEQ;
		break;
	      case DW_OP_ge:
		binop = BINOP_GEQ;
		break;
	      case DW_OP_eq:
		binop = BINOP_EQUAL;
		break;
	      case DW_OP_lt:
		binop = BINOP_LESS;
		break;
	      case DW_OP_gt:
		binop = BINOP_GTR;
		break;
	      case DW_OP_ne:
		binop = BINOP_NOTEQUAL;
		break;
	      default:
		internal_error (__FILE__, __LINE__,
				"Can't be reached.");
	      }
	    result = value_as_long (value_binop (val1, val2, binop));
	  }
	  break;

	case DW_OP_GNU_push_tls_address:
	  /* Variable is at a constant offset in the thread-local
	  storage block into the objfile for the current thread and
	  the dynamic linker module containing this expression. Here
	  we return returns the offset from that base.  The top of the
	  stack has the offset from the beginning of the thread
	  control block at which the variable is located.  Nothing
	  should follow this operator, so the top of stack would be
	  returned.  */
	  result = dwarf_expr_fetch (ctx, 0);
	  dwarf_expr_pop (ctx);
	  result = (ctx->get_tls_address) (ctx->baton, result);
	  break;

	case DW_OP_skip:
	  offset = extract_signed_integer (op_ptr, 2);
	  op_ptr += 2;
	  op_ptr += offset;
	  goto no_push;

	case DW_OP_bra:
	  offset = extract_signed_integer (op_ptr, 2);
	  op_ptr += 2;
	  if (dwarf_expr_fetch (ctx, 0) != 0)
	    op_ptr += offset;
	  dwarf_expr_pop (ctx);
	  goto no_push;

	case DW_OP_nop:
	  goto no_push;

	default:
	  error ("Unhandled dwarf expression opcode");
	}

      /* Most things push a result value.  */
      dwarf_expr_push (ctx, result);
    no_push:;
    }
}