aboutsummaryrefslogtreecommitdiff
path: root/gdb/ax-general.c
blob: e5dc240576ad3681985b412a64254701049e0c4d (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
/* Functions for manipulating expressions designed to be executed on the agent
   Copyright (C) 1998-2015 Free Software Foundation, Inc.

   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 3 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, see <http://www.gnu.org/licenses/>.  */

/* Despite what the above comment says about this file being part of
   GDB, we would like to keep these functions free of GDB
   dependencies, since we want to be able to use them in contexts
   outside of GDB (test suites, the stub, etc.)  */

#include "defs.h"
#include "ax.h"

#include "value.h"
#include "user-regs.h"

static void grow_expr (struct agent_expr *x, int n);

static void append_const (struct agent_expr *x, LONGEST val, int n);

static LONGEST read_const (struct agent_expr *x, int o, int n);

static void generic_ext (struct agent_expr *x, enum agent_op op, int n);

/* Functions for building expressions.  */

/* Allocate a new, empty agent expression.  */
struct agent_expr *
new_agent_expr (struct gdbarch *gdbarch, CORE_ADDR scope)
{
  struct agent_expr *x = XNEW (struct agent_expr);

  x->len = 0;
  x->size = 1;			/* Change this to a larger value once
				   reallocation code is tested.  */
  x->buf = (unsigned char *) xmalloc (x->size);

  x->gdbarch = gdbarch;
  x->scope = scope;

  /* Bit vector for registers used.  */
  x->reg_mask_len = 1;
  x->reg_mask = XCNEWVEC (unsigned char, x->reg_mask_len);

  x->tracing = 0;
  x->trace_string = 0;

  return x;
}

/* Free a agent expression.  */
void
free_agent_expr (struct agent_expr *x)
{
  xfree (x->buf);
  xfree (x->reg_mask);
  xfree (x);
}

static void
do_free_agent_expr_cleanup (void *x)
{
  free_agent_expr ((struct agent_expr *) x);
}

struct cleanup *
make_cleanup_free_agent_expr (struct agent_expr *x)
{
  return make_cleanup (do_free_agent_expr_cleanup, x);
}


/* Make sure that X has room for at least N more bytes.  This doesn't
   affect the length, just the allocated size.  */
static void
grow_expr (struct agent_expr *x, int n)
{
  if (x->len + n > x->size)
    {
      x->size *= 2;
      if (x->size < x->len + n)
	x->size = x->len + n + 10;
      x->buf = (unsigned char *) xrealloc (x->buf, x->size);
    }
}


/* Append the low N bytes of VAL as an N-byte integer to the
   expression X, in big-endian order.  */
static void
append_const (struct agent_expr *x, LONGEST val, int n)
{
  int i;

  grow_expr (x, n);
  for (i = n - 1; i >= 0; i--)
    {
      x->buf[x->len + i] = val & 0xff;
      val >>= 8;
    }
  x->len += n;
}


/* Extract an N-byte big-endian unsigned integer from expression X at
   offset O.  */
static LONGEST
read_const (struct agent_expr *x, int o, int n)
{
  int i;
  LONGEST accum = 0;

  /* Make sure we're not reading off the end of the expression.  */
  if (o + n > x->len)
    error (_("GDB bug: ax-general.c (read_const): incomplete constant"));

  for (i = 0; i < n; i++)
    accum = (accum << 8) | x->buf[o + i];

  return accum;
}


/* Append a simple operator OP to EXPR.  */
void
ax_simple (struct agent_expr *x, enum agent_op op)
{
  grow_expr (x, 1);
  x->buf[x->len++] = op;
}

/* Append a pick operator to EXPR.  DEPTH is the stack item to pick,
   with 0 being top of stack.  */

void
ax_pick (struct agent_expr *x, int depth)
{
  if (depth < 0 || depth > 255)
    error (_("GDB bug: ax-general.c (ax_pick): stack depth out of range"));
  ax_simple (x, aop_pick);
  append_const (x, 1, depth);
}


/* Append a sign-extension or zero-extension instruction to EXPR, to
   extend an N-bit value.  */
static void
generic_ext (struct agent_expr *x, enum agent_op op, int n)
{
  /* N must fit in a byte.  */
  if (n < 0 || n > 255)
    error (_("GDB bug: ax-general.c (generic_ext): bit count out of range"));
  /* That had better be enough range.  */
  if (sizeof (LONGEST) * 8 > 255)
    error (_("GDB bug: ax-general.c (generic_ext): "
	     "opcode has inadequate range"));

  grow_expr (x, 2);
  x->buf[x->len++] = op;
  x->buf[x->len++] = n;
}


/* Append a sign-extension instruction to EXPR, to extend an N-bit value.  */
void
ax_ext (struct agent_expr *x, int n)
{
  generic_ext (x, aop_ext, n);
}


/* Append a zero-extension instruction to EXPR, to extend an N-bit value.  */
void
ax_zero_ext (struct agent_expr *x, int n)
{
  generic_ext (x, aop_zero_ext, n);
}


/* Append a trace_quick instruction to EXPR, to record N bytes.  */
void
ax_trace_quick (struct agent_expr *x, int n)
{
  /* N must fit in a byte.  */
  if (n < 0 || n > 255)
    error (_("GDB bug: ax-general.c (ax_trace_quick): "
	     "size out of range for trace_quick"));

  grow_expr (x, 2);
  x->buf[x->len++] = aop_trace_quick;
  x->buf[x->len++] = n;
}


/* Append a goto op to EXPR.  OP is the actual op (must be aop_goto or
   aop_if_goto).  We assume we don't know the target offset yet,
   because it's probably a forward branch, so we leave space in EXPR
   for the target, and return the offset in EXPR of that space, so we
   can backpatch it once we do know the target offset.  Use ax_label
   to do the backpatching.  */
int
ax_goto (struct agent_expr *x, enum agent_op op)
{
  grow_expr (x, 3);
  x->buf[x->len + 0] = op;
  x->buf[x->len + 1] = 0xff;
  x->buf[x->len + 2] = 0xff;
  x->len += 3;
  return x->len - 2;
}

/* Suppose a given call to ax_goto returns some value PATCH.  When you
   know the offset TARGET that goto should jump to, call
   ax_label (EXPR, PATCH, TARGET)
   to patch TARGET into the ax_goto instruction.  */
void
ax_label (struct agent_expr *x, int patch, int target)
{
  /* Make sure the value is in range.  Don't accept 0xffff as an
     offset; that's our magic sentinel value for unpatched branches.  */
  if (target < 0 || target >= 0xffff)
    error (_("GDB bug: ax-general.c (ax_label): label target out of range"));

  x->buf[patch] = (target >> 8) & 0xff;
  x->buf[patch + 1] = target & 0xff;
}


/* Assemble code to push a constant on the stack.  */
void
ax_const_l (struct agent_expr *x, LONGEST l)
{
  static enum agent_op ops[]
  =
  {aop_const8, aop_const16, aop_const32, aop_const64};
  int size;
  int op;

  /* How big is the number?  'op' keeps track of which opcode to use.
     Notice that we don't really care whether the original number was
     signed or unsigned; we always reproduce the value exactly, and
     use the shortest representation.  */
  for (op = 0, size = 8; size < 64; size *= 2, op++)
    {
      LONGEST lim = ((LONGEST) 1) << (size - 1);

      if (-lim <= l && l <= lim - 1)
        break;
    }

  /* Emit the right opcode...  */
  ax_simple (x, ops[op]);

  /* Emit the low SIZE bytes as an unsigned number.  We know that
     sign-extending this will yield l.  */
  append_const (x, l, size / 8);

  /* Now, if it was negative, and not full-sized, sign-extend it.  */
  if (l < 0 && size < 64)
    ax_ext (x, size);
}


void
ax_const_d (struct agent_expr *x, LONGEST d)
{
  /* FIXME: floating-point support not present yet.  */
  error (_("GDB bug: ax-general.c (ax_const_d): "
	   "floating point not supported yet"));
}


/* Assemble code to push the value of register number REG on the
   stack.  */
void
ax_reg (struct agent_expr *x, int reg)
{
  if (reg >= gdbarch_num_regs (x->gdbarch))
    {
      /* This is a pseudo-register.  */
      if (!gdbarch_ax_pseudo_register_push_stack_p (x->gdbarch))
	error (_("'%s' is a pseudo-register; "
		 "GDB cannot yet trace its contents."),
	       user_reg_map_regnum_to_name (x->gdbarch, reg));
      if (gdbarch_ax_pseudo_register_push_stack (x->gdbarch, x, reg))
	error (_("Trace '%s' failed."),
	       user_reg_map_regnum_to_name (x->gdbarch, reg));
    }
  else
    {
      /* Make sure the register number is in range.  */
      if (reg < 0 || reg > 0xffff)
        error (_("GDB bug: ax-general.c (ax_reg): "
		 "register number out of range"));
      grow_expr (x, 3);
      x->buf[x->len] = aop_reg;
      x->buf[x->len + 1] = (reg >> 8) & 0xff;
      x->buf[x->len + 2] = (reg) & 0xff;
      x->len += 3;
    }
}

/* Assemble code to operate on a trace state variable.  */

void
ax_tsv (struct agent_expr *x, enum agent_op op, int num)
{
  /* Make sure the tsv number is in range.  */
  if (num < 0 || num > 0xffff)
    internal_error (__FILE__, __LINE__, 
		    _("ax-general.c (ax_tsv): variable "
		      "number is %d, out of range"), num);

  grow_expr (x, 3);
  x->buf[x->len] = op;
  x->buf[x->len + 1] = (num >> 8) & 0xff;
  x->buf[x->len + 2] = (num) & 0xff;
  x->len += 3;
}

/* Append a string to the expression.  Note that the string is going
   into the bytecodes directly, not on the stack.  As a precaution,
   include both length as prefix, and terminate with a NUL.  (The NUL
   is counted in the length.)  */

void
ax_string (struct agent_expr *x, const char *str, int slen)
{
  int i;

  /* Make sure the string length is reasonable.  */
  if (slen < 0 || slen > 0xffff)
    internal_error (__FILE__, __LINE__, 
		    _("ax-general.c (ax_string): string "
		      "length is %d, out of allowed range"), slen);

  grow_expr (x, 2 + slen + 1);
  x->buf[x->len++] = ((slen + 1) >> 8) & 0xff;
  x->buf[x->len++] = (slen + 1) & 0xff;
  for (i = 0; i < slen; ++i)
    x->buf[x->len++] = str[i];
  x->buf[x->len++] = '\0';
}



/* Functions for disassembling agent expressions, and otherwise
   debugging the expression compiler.  */

struct aop_map aop_map[] =
{
  {0, 0, 0, 0, 0}
#define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \
  , { # NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED }
#include "ax.def"
#undef DEFOP
};


/* Disassemble the expression EXPR, writing to F.  */
void
ax_print (struct ui_file *f, struct agent_expr *x)
{
  int i;

  fprintf_filtered (f, _("Scope: %s\n"), paddress (x->gdbarch, x->scope));
  fprintf_filtered (f, _("Reg mask:"));
  for (i = 0; i < x->reg_mask_len; ++i)
    fprintf_filtered (f, _(" %02x"), x->reg_mask[i]);
  fprintf_filtered (f, _("\n"));

  /* Check the size of the name array against the number of entries in
     the enum, to catch additions that people didn't sync.  */
  if ((sizeof (aop_map) / sizeof (aop_map[0]))
      != aop_last)
    error (_("GDB bug: ax-general.c (ax_print): opcode map out of sync"));

  for (i = 0; i < x->len;)
    {
      enum agent_op op = (enum agent_op) x->buf[i];

      if (op >= (sizeof (aop_map) / sizeof (aop_map[0]))
	  || !aop_map[op].name)
	{
	  fprintf_filtered (f, _("%3d  <bad opcode %02x>\n"), i, op);
	  i++;
	  continue;
	}
      if (i + 1 + aop_map[op].op_size > x->len)
	{
	  fprintf_filtered (f, _("%3d  <incomplete opcode %s>\n"),
			    i, aop_map[op].name);
	  break;
	}

      fprintf_filtered (f, "%3d  %s", i, aop_map[op].name);
      if (aop_map[op].op_size > 0)
	{
	  fputs_filtered (" ", f);

	  print_longest (f, 'd', 0,
			 read_const (x, i + 1, aop_map[op].op_size));
	}
      /* Handle the complicated printf arguments specially.  */
      else if (op == aop_printf)
	{
	  int slen, nargs;

	  i++;
	  nargs = x->buf[i++];
	  slen = x->buf[i++];
	  slen = slen * 256 + x->buf[i++];
	  fprintf_filtered (f, _(" \"%s\", %d args"),
			    &(x->buf[i]), nargs);
	  i += slen - 1;
	}
      fprintf_filtered (f, "\n");
      i += 1 + aop_map[op].op_size;
    }
}

/* Add register REG to the register mask for expression AX.  */
void
ax_reg_mask (struct agent_expr *ax, int reg)
{
  if (reg >= gdbarch_num_regs (ax->gdbarch))
    {
      /* This is a pseudo-register.  */
      if (!gdbarch_ax_pseudo_register_collect_p (ax->gdbarch))
	error (_("'%s' is a pseudo-register; "
		 "GDB cannot yet trace its contents."),
	       user_reg_map_regnum_to_name (ax->gdbarch, reg));
      if (gdbarch_ax_pseudo_register_collect (ax->gdbarch, ax, reg))
	error (_("Trace '%s' failed."),
	       user_reg_map_regnum_to_name (ax->gdbarch, reg));
    }
  else
    {
      int byte = reg / 8;

      /* Grow the bit mask if necessary.  */
      if (byte >= ax->reg_mask_len)
        {
          /* It's not appropriate to double here.  This isn't a
	     string buffer.  */
          int new_len = byte + 1;
          unsigned char *new_reg_mask
	    = XRESIZEVEC (unsigned char, ax->reg_mask, new_len);

          memset (new_reg_mask + ax->reg_mask_len, 0,
	          (new_len - ax->reg_mask_len) * sizeof (ax->reg_mask[0]));
          ax->reg_mask_len = new_len;
          ax->reg_mask = new_reg_mask;
        }

      ax->reg_mask[byte] |= 1 << (reg % 8);
    }
}

/* Given an agent expression AX, fill in requirements and other descriptive
   bits.  */
void
ax_reqs (struct agent_expr *ax)
{
  int i;
  int height;

  /* Jump target table.  targets[i] is non-zero iff we have found a
     jump to offset i.  */
  char *targets = (char *) alloca (ax->len * sizeof (targets[0]));

  /* Instruction boundary table.  boundary[i] is non-zero iff our scan
     has reached an instruction starting at offset i.  */
  char *boundary = (char *) alloca (ax->len * sizeof (boundary[0]));

  /* Stack height record.  If either targets[i] or boundary[i] is
     non-zero, heights[i] is the height the stack should have before
     executing the bytecode at that point.  */
  int *heights = (int *) alloca (ax->len * sizeof (heights[0]));

  /* Pointer to a description of the present op.  */
  struct aop_map *op;

  memset (targets, 0, ax->len * sizeof (targets[0]));
  memset (boundary, 0, ax->len * sizeof (boundary[0]));

  ax->max_height = ax->min_height = height = 0;
  ax->flaw = agent_flaw_none;
  ax->max_data_size = 0;

  for (i = 0; i < ax->len; i += 1 + op->op_size)
    {
      if (ax->buf[i] > (sizeof (aop_map) / sizeof (aop_map[0])))
	{
	  ax->flaw = agent_flaw_bad_instruction;
	  return;
	}

      op = &aop_map[ax->buf[i]];

      if (!op->name)
	{
	  ax->flaw = agent_flaw_bad_instruction;
	  return;
	}

      if (i + 1 + op->op_size > ax->len)
	{
	  ax->flaw = agent_flaw_incomplete_instruction;
	  return;
	}

      /* If this instruction is a forward jump target, does the
         current stack height match the stack height at the jump
         source?  */
      if (targets[i] && (heights[i] != height))
	{
	  ax->flaw = agent_flaw_height_mismatch;
	  return;
	}

      boundary[i] = 1;
      heights[i] = height;

      height -= op->consumed;
      if (height < ax->min_height)
	ax->min_height = height;
      height += op->produced;
      if (height > ax->max_height)
	ax->max_height = height;

      if (op->data_size > ax->max_data_size)
	ax->max_data_size = op->data_size;

      /* For jump instructions, check that the target is a valid
         offset.  If it is, record the fact that that location is a
         jump target, and record the height we expect there.  */
      if (aop_goto == op - aop_map
	  || aop_if_goto == op - aop_map)
	{
	  int target = read_const (ax, i + 1, 2);
	  if (target < 0 || target >= ax->len)
	    {
	      ax->flaw = agent_flaw_bad_jump;
	      return;
	    }

	  /* Do we have any information about what the stack height
             should be at the target?  */
	  if (targets[target] || boundary[target])
	    {
	      if (heights[target] != height)
		{
		  ax->flaw = agent_flaw_height_mismatch;
		  return;
		}
	    }

          /* Record the target, along with the stack height we expect.  */
          targets[target] = 1;
          heights[target] = height;
	}

      /* For unconditional jumps with a successor, check that the
         successor is a target, and pick up its stack height.  */
      if (aop_goto == op - aop_map
	  && i + 3 < ax->len)
	{
	  if (!targets[i + 3])
	    {
	      ax->flaw = agent_flaw_hole;
	      return;
	    }

	  height = heights[i + 3];
	}

      /* For reg instructions, record the register in the bit mask.  */
      if (aop_reg == op - aop_map)
	{
	  int reg = read_const (ax, i + 1, 2);

	  ax_reg_mask (ax, reg);
	}
    }

  /* Check that all the targets are on boundaries.  */
  for (i = 0; i < ax->len; i++)
    if (targets[i] && !boundary[i])
      {
	ax->flaw = agent_flaw_bad_jump;
	return;
      }

  ax->final_height = height;
}