gdb/ax-general.c

   1 /* Functions for manipulating expressions designed to be executed on the agent
   2    Copyright (C) 1998, 1999, 2000, 2007, 2008, 2009
   3    Free Software Foundation, Inc.
   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 3 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, see <http://www.gnu.org/licenses/>.  */
  19
  20 /* Despite what the above comment says about this file being part of
  21    GDB, we would like to keep these functions free of GDB
  22    dependencies, since we want to be able to use them in contexts
  23    outside of GDB (test suites, the stub, etc.)  */
  24
  25 #include "defs.h"
  26 #include "ax.h"
  27
  28 #include "value.h"
  29 #include "gdb_string.h"
  30
  31 static void grow_expr (struct agent_expr *x, int n);
  32
  33 static void append_const (struct agent_expr *x, LONGEST val, int n);
  34
  35 static LONGEST read_const (struct agent_expr *x, int o, int n);
  36
  37 static void generic_ext (struct agent_expr *x, enum agent_op op, int n);
  38 \f
  39 /* Functions for building expressions.  */
  40
  41 /* Allocate a new, empty agent expression.  */
  42 struct agent_expr *
  43 new_agent_expr (CORE_ADDR scope)
  44 {
  45   struct agent_expr *x = xmalloc (sizeof (*x));
  46   x->len = 0;
  47   x->size = 1;                  /* Change this to a larger value once
  48                                    reallocation code is tested.  */
  49   x->buf = xmalloc (x->size);
  50   x->scope = scope;
  51
  52   return x;
  53 }
  54
  55 /* Free a agent expression.  */
  56 void
  57 free_agent_expr (struct agent_expr *x)
  58 {
  59   xfree (x->buf);
  60   xfree (x);
  61 }
  62
  63 static void
  64 do_free_agent_expr_cleanup (void *x)
  65 {
  66   free_agent_expr (x);
  67 }
  68
  69 struct cleanup *
  70 make_cleanup_free_agent_expr (struct agent_expr *x)
  71 {
  72   return make_cleanup (do_free_agent_expr_cleanup, x);
  73 }
  74
  75
  76 /* Make sure that X has room for at least N more bytes.  This doesn't
  77    affect the length, just the allocated size.  */
  78 static void
  79 grow_expr (struct agent_expr *x, int n)
  80 {
  81   if (x->len + n > x->size)
  82     {
  83       x->size *= 2;
  84       if (x->size < x->len + n)
  85         x->size = x->len + n + 10;
  86       x->buf = xrealloc (x->buf, x->size);
  87     }
  88 }
  89
  90
  91 /* Append the low N bytes of VAL as an N-byte integer to the
  92    expression X, in big-endian order.  */
  93 static void
  94 append_const (struct agent_expr *x, LONGEST val, int n)
  95 {
  96   int i;
  97
  98   grow_expr (x, n);
  99   for (i = n - 1; i >= 0; i--)
 100     {
 101       x->buf[x->len + i] = val & 0xff;
 102       val >>= 8;
 103     }
 104   x->len += n;
 105 }
 106
 107
 108 /* Extract an N-byte big-endian unsigned integer from expression X at
 109    offset O.  */
 110 static LONGEST
 111 read_const (struct agent_expr *x, int o, int n)
 112 {
 113   int i;
 114   LONGEST accum = 0;
 115
 116   /* Make sure we're not reading off the end of the expression.  */
 117   if (o + n > x->len)
 118     error (_("GDB bug: ax-general.c (read_const): incomplete constant"));
 119
 120   for (i = 0; i < n; i++)
 121     accum = (accum << 8) | x->buf[o + i];
 122
 123   return accum;
 124 }
 125
 126
 127 /* Append a simple operator OP to EXPR.  */
 128 void
 129 ax_simple (struct agent_expr *x, enum agent_op op)
 130 {
 131   grow_expr (x, 1);
 132   x->buf[x->len++] = op;
 133 }
 134
 135
 136 /* Append a sign-extension or zero-extension instruction to EXPR, to
 137    extend an N-bit value.  */
 138 static void
 139 generic_ext (struct agent_expr *x, enum agent_op op, int n)
 140 {
 141   /* N must fit in a byte.  */
 142   if (n < 0 || n > 255)
 143     error (_("GDB bug: ax-general.c (generic_ext): bit count out of range"));
 144   /* That had better be enough range.  */
 145   if (sizeof (LONGEST) * 8 > 255)
 146     error (_("GDB bug: ax-general.c (generic_ext): opcode has inadequate range"));
 147
 148   grow_expr (x, 2);
 149   x->buf[x->len++] = op;
 150   x->buf[x->len++] = n;
 151 }
 152
 153
 154 /* Append a sign-extension instruction to EXPR, to extend an N-bit value.  */
 155 void
 156 ax_ext (struct agent_expr *x, int n)
 157 {
 158   generic_ext (x, aop_ext, n);
 159 }
 160
 161
 162 /* Append a zero-extension instruction to EXPR, to extend an N-bit value.  */
 163 void
 164 ax_zero_ext (struct agent_expr *x, int n)
 165 {
 166   generic_ext (x, aop_zero_ext, n);
 167 }
 168
 169
 170 /* Append a trace_quick instruction to EXPR, to record N bytes.  */
 171 void
 172 ax_trace_quick (struct agent_expr *x, int n)
 173 {
 174   /* N must fit in a byte.  */
 175   if (n < 0 || n > 255)
 176     error (_("GDB bug: ax-general.c (ax_trace_quick): size out of range for trace_quick"));
 177
 178   grow_expr (x, 2);
 179   x->buf[x->len++] = aop_trace_quick;
 180   x->buf[x->len++] = n;
 181 }
 182
 183
 184 /* Append a goto op to EXPR.  OP is the actual op (must be aop_goto or
 185    aop_if_goto).  We assume we don't know the target offset yet,
 186    because it's probably a forward branch, so we leave space in EXPR
 187    for the target, and return the offset in EXPR of that space, so we
 188    can backpatch it once we do know the target offset.  Use ax_label
 189    to do the backpatching.  */
 190 int
 191 ax_goto (struct agent_expr *x, enum agent_op op)
 192 {
 193   grow_expr (x, 3);
 194   x->buf[x->len + 0] = op;
 195   x->buf[x->len + 1] = 0xff;
 196   x->buf[x->len + 2] = 0xff;
 197   x->len += 3;
 198   return x->len - 2;
 199 }
 200
 201 /* Suppose a given call to ax_goto returns some value PATCH.  When you
 202    know the offset TARGET that goto should jump to, call
 203    ax_label (EXPR, PATCH, TARGET)
 204    to patch TARGET into the ax_goto instruction.  */
 205 void
 206 ax_label (struct agent_expr *x, int patch, int target)
 207 {
 208   /* Make sure the value is in range.  Don't accept 0xffff as an
 209      offset; that's our magic sentinel value for unpatched branches.  */
 210   if (target < 0 || target >= 0xffff)
 211     error (_("GDB bug: ax-general.c (ax_label): label target out of range"));
 212
 213   x->buf[patch] = (target >> 8) & 0xff;
 214   x->buf[patch + 1] = target & 0xff;
 215 }
 216
 217
 218 /* Assemble code to push a constant on the stack.  */
 219 void
 220 ax_const_l (struct agent_expr *x, LONGEST l)
 221 {
 222   static enum agent_op ops[]
 223   =
 224   {aop_const8, aop_const16, aop_const32, aop_const64};
 225   int size;
 226   int op;
 227
 228   /* How big is the number?  'op' keeps track of which opcode to use.
 229      Notice that we don't really care whether the original number was
 230      signed or unsigned; we always reproduce the value exactly, and
 231      use the shortest representation.  */
 232   for (op = 0, size = 8; size < 64; size *= 2, op++)
 233     {
 234       LONGEST lim = 1 << (size - 1);
 235
 236       if (-lim <= l && l <= lim - 1)
 237         break;
 238     }
 239
 240   /* Emit the right opcode... */
 241   ax_simple (x, ops[op]);
 242
 243   /* Emit the low SIZE bytes as an unsigned number.  We know that
 244      sign-extending this will yield l.  */
 245   append_const (x, l, size / 8);
 246
 247   /* Now, if it was negative, and not full-sized, sign-extend it.  */
 248   if (l < 0 && size < 64)
 249     ax_ext (x, size);
 250 }
 251
 252
 253 void
 254 ax_const_d (struct agent_expr *x, LONGEST d)
 255 {
 256   /* FIXME: floating-point support not present yet.  */
 257   error (_("GDB bug: ax-general.c (ax_const_d): floating point not supported yet"));
 258 }
 259
 260
 261 /* Assemble code to push the value of register number REG on the
 262    stack.  */
 263 void
 264 ax_reg (struct agent_expr *x, int reg)
 265 {
 266   /* Make sure the register number is in range.  */
 267   if (reg < 0 || reg > 0xffff)
 268     error (_("GDB bug: ax-general.c (ax_reg): register number out of range"));
 269   grow_expr (x, 3);
 270   x->buf[x->len] = aop_reg;
 271   x->buf[x->len + 1] = (reg >> 8) & 0xff;
 272   x->buf[x->len + 2] = (reg) & 0xff;
 273   x->len += 3;
 274 }
 275
 276 /* Assemble code to operate on a trace state variable.  */
 277
 278 void
 279 ax_tsv (struct agent_expr *x, enum agent_op op, int num)
 280 {
 281   /* Make sure the tsv number is in range.  */
 282   if (num < 0 || num > 0xffff)
 283     internal_error (__FILE__, __LINE__, _("ax-general.c (ax_tsv): variable number is %d, out of range"), num);
 284
 285   grow_expr (x, 3);
 286   x->buf[x->len] = op;
 287   x->buf[x->len + 1] = (num >> 8) & 0xff;
 288   x->buf[x->len + 2] = (num) & 0xff;
 289   x->len += 3;
 290 }
 291 \f
 292
 293
 294 /* Functions for disassembling agent expressions, and otherwise
 295    debugging the expression compiler.  */
 296
 297 struct aop_map aop_map[] =
 298 {
 299   {0, 0, 0, 0, 0},
 300   {"float", 0, 0, 0, 0},        /* 0x01 */
 301   {"add", 0, 0, 2, 1},          /* 0x02 */
 302   {"sub", 0, 0, 2, 1},          /* 0x03 */
 303   {"mul", 0, 0, 2, 1},          /* 0x04 */
 304   {"div_signed", 0, 0, 2, 1},   /* 0x05 */
 305   {"div_unsigned", 0, 0, 2, 1}, /* 0x06 */
 306   {"rem_signed", 0, 0, 2, 1},   /* 0x07 */
 307   {"rem_unsigned", 0, 0, 2, 1}, /* 0x08 */
 308   {"lsh", 0, 0, 2, 1},          /* 0x09 */
 309   {"rsh_signed", 0, 0, 2, 1},   /* 0x0a */
 310   {"rsh_unsigned", 0, 0, 2, 1}, /* 0x0b */
 311   {"trace", 0, 0, 2, 0},        /* 0x0c */
 312   {"trace_quick", 1, 0, 1, 1},  /* 0x0d */
 313   {"log_not", 0, 0, 1, 1},      /* 0x0e */
 314   {"bit_and", 0, 0, 2, 1},      /* 0x0f */
 315   {"bit_or", 0, 0, 2, 1},       /* 0x10 */
 316   {"bit_xor", 0, 0, 2, 1},      /* 0x11 */
 317   {"bit_not", 0, 0, 1, 1},      /* 0x12 */
 318   {"equal", 0, 0, 2, 1},        /* 0x13 */
 319   {"less_signed", 0, 0, 2, 1},  /* 0x14 */
 320   {"less_unsigned", 0, 0, 2, 1},        /* 0x15 */
 321   {"ext", 1, 0, 1, 1},          /* 0x16 */
 322   {"ref8", 0, 8, 1, 1},         /* 0x17 */
 323   {"ref16", 0, 16, 1, 1},       /* 0x18 */
 324   {"ref32", 0, 32, 1, 1},       /* 0x19 */
 325   {"ref64", 0, 64, 1, 1},       /* 0x1a */
 326   {"ref_float", 0, 0, 1, 1},    /* 0x1b */
 327   {"ref_double", 0, 0, 1, 1},   /* 0x1c */
 328   {"ref_long_double", 0, 0, 1, 1},      /* 0x1d */
 329   {"l_to_d", 0, 0, 1, 1},       /* 0x1e */
 330   {"d_to_l", 0, 0, 1, 1},       /* 0x1f */
 331   {"if_goto", 2, 0, 1, 0},      /* 0x20 */
 332   {"goto", 2, 0, 0, 0},         /* 0x21 */
 333   {"const8", 1, 8, 0, 1},       /* 0x22 */
 334   {"const16", 2, 16, 0, 1},     /* 0x23 */
 335   {"const32", 4, 32, 0, 1},     /* 0x24 */
 336   {"const64", 8, 64, 0, 1},     /* 0x25 */
 337   {"reg", 2, 0, 0, 1},          /* 0x26 */
 338   {"end", 0, 0, 0, 0},          /* 0x27 */
 339   {"dup", 0, 0, 1, 2},          /* 0x28 */
 340   {"pop", 0, 0, 1, 0},          /* 0x29 */
 341   {"zero_ext", 1, 0, 1, 1},     /* 0x2a */
 342   {"swap", 0, 0, 2, 2},         /* 0x2b */
 343   {"getv", 2, 0, 0, 1},         /* 0x2c */
 344   {"setv", 2, 0, 0, 1},         /* 0x2d */
 345   {"tracev", 2, 0, 0, 1},       /* 0x2e */
 346   {0, 0, 0, 0, 0},              /* 0x2f */
 347   {"trace16", 2, 0, 1, 1},      /* 0x30 */
 348 };
 349
 350
 351 /* Disassemble the expression EXPR, writing to F.  */
 352 void
 353 ax_print (struct ui_file *f, struct agent_expr *x)
 354 {
 355   int i;
 356   int is_float = 0;
 357
 358   /* Check the size of the name array against the number of entries in
 359      the enum, to catch additions that people didn't sync.  */
 360   if ((sizeof (aop_map) / sizeof (aop_map[0]))
 361       != aop_last)
 362     error (_("GDB bug: ax-general.c (ax_print): opcode map out of sync"));
 363
 364   for (i = 0; i < x->len;)
 365     {
 366       enum agent_op op = x->buf[i];
 367
 368       if (op >= (sizeof (aop_map) / sizeof (aop_map[0]))
 369           || !aop_map[op].name)
 370         {
 371           fprintf_filtered (f, _("%3d  <bad opcode %02x>\n"), i, op);
 372           i++;
 373           continue;
 374         }
 375       if (i + 1 + aop_map[op].op_size > x->len)
 376         {
 377           fprintf_filtered (f, _("%3d  <incomplete opcode %s>\n"),
 378                             i, aop_map[op].name);
 379           break;
 380         }
 381
 382       fprintf_filtered (f, "%3d  %s", i, aop_map[op].name);
 383       if (aop_map[op].op_size > 0)
 384         {
 385           fputs_filtered (" ", f);
 386
 387           print_longest (f, 'd', 0,
 388                          read_const (x, i + 1, aop_map[op].op_size));
 389         }
 390       fprintf_filtered (f, "\n");
 391       i += 1 + aop_map[op].op_size;
 392
 393       is_float = (op == aop_float);
 394     }
 395 }
 396
 397
 398 /* Given an agent expression AX, fill in an agent_reqs structure REQS
 399    describing it.  */
 400 void
 401 ax_reqs (struct agent_expr *ax, struct agent_reqs *reqs)
 402 {
 403   int i;
 404   int height;
 405
 406   /* Bit vector for registers used.  */
 407   int reg_mask_len = 1;
 408   unsigned char *reg_mask = xmalloc (reg_mask_len * sizeof (reg_mask[0]));
 409
 410   /* Jump target table.  targets[i] is non-zero iff we have found a
 411      jump to offset i.  */
 412   char *targets = (char *) alloca (ax->len * sizeof (targets[0]));
 413
 414   /* Instruction boundary table.  boundary[i] is non-zero iff our scan
 415      has reached an instruction starting at offset i.  */
 416   char *boundary = (char *) alloca (ax->len * sizeof (boundary[0]));
 417
 418   /* Stack height record.  If either targets[i] or boundary[i] is
 419      non-zero, heights[i] is the height the stack should have before
 420      executing the bytecode at that point.  */
 421   int *heights = (int *) alloca (ax->len * sizeof (heights[0]));
 422
 423   /* Pointer to a description of the present op.  */
 424   struct aop_map *op;
 425
 426   memset (reg_mask, 0, reg_mask_len * sizeof (reg_mask[0]));
 427   memset (targets, 0, ax->len * sizeof (targets[0]));
 428   memset (boundary, 0, ax->len * sizeof (boundary[0]));
 429
 430   reqs->max_height = reqs->min_height = height = 0;
 431   reqs->flaw = agent_flaw_none;
 432   reqs->max_data_size = 0;
 433
 434   for (i = 0; i < ax->len; i += 1 + op->op_size)
 435     {
 436       if (ax->buf[i] > (sizeof (aop_map) / sizeof (aop_map[0])))
 437         {
 438           reqs->flaw = agent_flaw_bad_instruction;
 439           xfree (reg_mask);
 440           return;
 441         }
 442
 443       op = &aop_map[ax->buf[i]];
 444
 445       if (!op->name)
 446         {
 447           reqs->flaw = agent_flaw_bad_instruction;
 448           xfree (reg_mask);
 449           return;
 450         }
 451
 452       if (i + 1 + op->op_size > ax->len)
 453         {
 454           reqs->flaw = agent_flaw_incomplete_instruction;
 455           xfree (reg_mask);
 456           return;
 457         }
 458
 459       /* If this instruction is a forward jump target, does the
 460          current stack height match the stack height at the jump
 461          source?  */
 462       if (targets[i] && (heights[i] != height))
 463         {
 464           reqs->flaw = agent_flaw_height_mismatch;
 465           xfree (reg_mask);
 466           return;
 467         }
 468
 469       boundary[i] = 1;
 470       heights[i] = height;
 471
 472       height -= op->consumed;
 473       if (height < reqs->min_height)
 474         reqs->min_height = height;
 475       height += op->produced;
 476       if (height > reqs->max_height)
 477         reqs->max_height = height;
 478
 479       if (op->data_size > reqs->max_data_size)
 480         reqs->max_data_size = op->data_size;
 481
 482       /* For jump instructions, check that the target is a valid
 483          offset.  If it is, record the fact that that location is a
 484          jump target, and record the height we expect there.  */
 485       if (aop_goto == op - aop_map
 486           || aop_if_goto == op - aop_map)
 487         {
 488           int target = read_const (ax, i + 1, 2);
 489           if (target < 0 || target >= ax->len)
 490             {
 491               reqs->flaw = agent_flaw_bad_jump;
 492               xfree (reg_mask);
 493               return;
 494             }
 495
 496           /* Do we have any information about what the stack height
 497              should be at the target?  */
 498           if (targets[target] || boundary[target])
 499             {
 500               if (heights[target] != height)
 501                 {
 502                   reqs->flaw = agent_flaw_height_mismatch;
 503                   xfree (reg_mask);
 504                   return;
 505                 }
 506             }
 507
 508           /* Record the target, along with the stack height we expect.  */
 509           targets[target] = 1;
 510           heights[target] = height;
 511         }
 512
 513       /* For unconditional jumps with a successor, check that the
 514          successor is a target, and pick up its stack height.  */
 515       if (aop_goto == op - aop_map
 516           && i + 3 < ax->len)
 517         {
 518           if (!targets[i + 3])
 519             {
 520               reqs->flaw = agent_flaw_hole;
 521               xfree (reg_mask);
 522               return;
 523             }
 524
 525           height = heights[i + 3];
 526         }
 527
 528       /* For reg instructions, record the register in the bit mask.  */
 529       if (aop_reg == op - aop_map)
 530         {
 531           int reg = read_const (ax, i + 1, 2);
 532           int byte = reg / 8;
 533
 534           /* Grow the bit mask if necessary.  */
 535           if (byte >= reg_mask_len)
 536             {
 537               /* It's not appropriate to double here.  This isn't a
 538                  string buffer.  */
 539               int new_len = byte + 1;
 540               reg_mask = xrealloc (reg_mask,
 541                                    new_len * sizeof (reg_mask[0]));
 542               memset (reg_mask + reg_mask_len, 0,
 543                       (new_len - reg_mask_len) * sizeof (reg_mask[0]));
 544               reg_mask_len = new_len;
 545             }
 546
 547           reg_mask[byte] |= 1 << (reg % 8);
 548         }
 549     }
 550
 551   /* Check that all the targets are on boundaries.  */
 552   for (i = 0; i < ax->len; i++)
 553     if (targets[i] && !boundary[i])
 554       {
 555         reqs->flaw = agent_flaw_bad_jump;
 556         xfree (reg_mask);
 557         return;
 558       }
 559
 560   reqs->final_height = height;
 561   reqs->reg_mask_len = reg_mask_len;
 562   reqs->reg_mask = reg_mask;
 563 }