gdb/ax-general.c

   1 /* Functions for manipulating expressions designed to be executed on the agent
   2    Copyright 1998, 1999, 2000 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 /* Despite what the above comment says about this file being part of
  22    GDB, we would like to keep these functions free of GDB
  23    dependencies, since we want to be able to use them in contexts
  24    outside of GDB (test suites, the stub, etc.)  */
  25
  26 #include "defs.h"
  27 #include "ax.h"
  28
  29 #include "value.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     if (-((LONGEST) 1 << size) <= l && l < ((LONGEST) 1 << size))
 234       break;
 235
 236   /* Emit the right opcode... */
 237   ax_simple (x, ops[op]);
 238
 239   /* Emit the low SIZE bytes as an unsigned number.  We know that
 240      sign-extending this will yield l.  */
 241   append_const (x, l, size / 8);
 242
 243   /* Now, if it was negative, and not full-sized, sign-extend it.  */
 244   if (l < 0 && size < 64)
 245     ax_ext (x, size);
 246 }
 247
 248
 249 void
 250 ax_const_d (struct agent_expr *x, LONGEST d)
 251 {
 252   /* FIXME: floating-point support not present yet.  */
 253   error ("GDB bug: ax-general.c (ax_const_d): floating point not supported yet");
 254 }
 255
 256
 257 /* Assemble code to push the value of register number REG on the
 258    stack.  */
 259 void
 260 ax_reg (struct agent_expr *x, int reg)
 261 {
 262   /* Make sure the register number is in range.  */
 263   if (reg < 0 || reg > 0xffff)
 264     error ("GDB bug: ax-general.c (ax_reg): register number out of range");
 265   grow_expr (x, 3);
 266   x->buf[x->len] = aop_reg;
 267   x->buf[x->len + 1] = (reg >> 8) & 0xff;
 268   x->buf[x->len + 2] = (reg) & 0xff;
 269   x->len += 3;
 270 }
 271 \f
 272
 273
 274 /* Functions for disassembling agent expressions, and otherwise
 275    debugging the expression compiler.  */
 276
 277 struct aop_map aop_map[] =
 278 {
 279   {0, 0, 0, 0, 0},
 280   {"float", 0, 0, 0, 0},        /* 0x01 */
 281   {"add", 0, 0, 2, 1},          /* 0x02 */
 282   {"sub", 0, 0, 2, 1},          /* 0x03 */
 283   {"mul", 0, 0, 2, 1},          /* 0x04 */
 284   {"div_signed", 0, 0, 2, 1},   /* 0x05 */
 285   {"div_unsigned", 0, 0, 2, 1}, /* 0x06 */
 286   {"rem_signed", 0, 0, 2, 1},   /* 0x07 */
 287   {"rem_unsigned", 0, 0, 2, 1}, /* 0x08 */
 288   {"lsh", 0, 0, 2, 1},          /* 0x09 */
 289   {"rsh_signed", 0, 0, 2, 1},   /* 0x0a */
 290   {"rsh_unsigned", 0, 0, 2, 1}, /* 0x0b */
 291   {"trace", 0, 0, 2, 0},        /* 0x0c */
 292   {"trace_quick", 1, 0, 1, 1},  /* 0x0d */
 293   {"log_not", 0, 0, 1, 1},      /* 0x0e */
 294   {"bit_and", 0, 0, 2, 1},      /* 0x0f */
 295   {"bit_or", 0, 0, 2, 1},       /* 0x10 */
 296   {"bit_xor", 0, 0, 2, 1},      /* 0x11 */
 297   {"bit_not", 0, 0, 1, 1},      /* 0x12 */
 298   {"equal", 0, 0, 2, 1},        /* 0x13 */
 299   {"less_signed", 0, 0, 2, 1},  /* 0x14 */
 300   {"less_unsigned", 0, 0, 2, 1},        /* 0x15 */
 301   {"ext", 1, 0, 1, 1},          /* 0x16 */
 302   {"ref8", 0, 8, 1, 1},         /* 0x17 */
 303   {"ref16", 0, 16, 1, 1},       /* 0x18 */
 304   {"ref32", 0, 32, 1, 1},       /* 0x19 */
 305   {"ref64", 0, 64, 1, 1},       /* 0x1a */
 306   {"ref_float", 0, 0, 1, 1},    /* 0x1b */
 307   {"ref_double", 0, 0, 1, 1},   /* 0x1c */
 308   {"ref_long_double", 0, 0, 1, 1},      /* 0x1d */
 309   {"l_to_d", 0, 0, 1, 1},       /* 0x1e */
 310   {"d_to_l", 0, 0, 1, 1},       /* 0x1f */
 311   {"if_goto", 2, 0, 1, 0},      /* 0x20 */
 312   {"goto", 2, 0, 0, 0},         /* 0x21 */
 313   {"const8", 1, 8, 0, 1},       /* 0x22 */
 314   {"const16", 2, 16, 0, 1},     /* 0x23 */
 315   {"const32", 4, 32, 0, 1},     /* 0x24 */
 316   {"const64", 8, 64, 0, 1},     /* 0x25 */
 317   {"reg", 2, 0, 0, 1},          /* 0x26 */
 318   {"end", 0, 0, 0, 0},          /* 0x27 */
 319   {"dup", 0, 0, 1, 2},          /* 0x28 */
 320   {"pop", 0, 0, 1, 0},          /* 0x29 */
 321   {"zero_ext", 1, 0, 1, 1},     /* 0x2a */
 322   {"swap", 0, 0, 2, 2},         /* 0x2b */
 323   {0, 0, 0, 0, 0},              /* 0x2c */
 324   {0, 0, 0, 0, 0},              /* 0x2d */
 325   {0, 0, 0, 0, 0},              /* 0x2e */
 326   {0, 0, 0, 0, 0},              /* 0x2f */
 327   {"trace16", 2, 0, 1, 1},      /* 0x30 */
 328 };
 329
 330
 331 /* Disassemble the expression EXPR, writing to F.  */
 332 void
 333 ax_print (struct ui_file *f, struct agent_expr *x)
 334 {
 335   int i;
 336   int is_float = 0;
 337
 338   /* Check the size of the name array against the number of entries in
 339      the enum, to catch additions that people didn't sync.  */
 340   if ((sizeof (aop_map) / sizeof (aop_map[0]))
 341       != aop_last)
 342     error ("GDB bug: ax-general.c (ax_print): opcode map out of sync");
 343
 344   for (i = 0; i < x->len;)
 345     {
 346       enum agent_op op = x->buf[i];
 347
 348       if (op >= (sizeof (aop_map) / sizeof (aop_map[0]))
 349           || !aop_map[op].name)
 350         {
 351           fprintf_filtered (f, "%3d  <bad opcode %02x>\n", i, op);
 352           i++;
 353           continue;
 354         }
 355       if (i + 1 + aop_map[op].op_size > x->len)
 356         {
 357           fprintf_filtered (f, "%3d  <incomplete opcode %s>\n",
 358                             i, aop_map[op].name);
 359           break;
 360         }
 361
 362       fprintf_filtered (f, "%3d  %s", i, aop_map[op].name);
 363       if (aop_map[op].op_size > 0)
 364         {
 365           fputs_filtered (" ", f);
 366
 367           print_longest (f, 'd', 0,
 368                          read_const (x, i + 1, aop_map[op].op_size));
 369         }
 370       fprintf_filtered (f, "\n");
 371       i += 1 + aop_map[op].op_size;
 372
 373       is_float = (op == aop_float);
 374     }
 375 }
 376
 377
 378 /* Given an agent expression AX, fill in an agent_reqs structure REQS
 379    describing it.  */
 380 void
 381 ax_reqs (struct agent_expr *ax, struct agent_reqs *reqs)
 382 {
 383   int i;
 384   int height;
 385
 386   /* Bit vector for registers used.  */
 387   int reg_mask_len = 1;
 388   unsigned char *reg_mask = xmalloc (reg_mask_len * sizeof (reg_mask[0]));
 389
 390   /* Jump target table.  targets[i] is non-zero iff there is a jump to
 391      offset i.  */
 392   char *targets = (char *) alloca (ax->len * sizeof (targets[0]));
 393
 394   /* Instruction boundary table.  boundary[i] is non-zero iff an
 395      instruction starts at offset i.  */
 396   char *boundary = (char *) alloca (ax->len * sizeof (boundary[0]));
 397
 398   /* Stack height record.  iff either targets[i] or boundary[i] is
 399      non-zero, heights[i] is the height the stack should have before
 400      executing the bytecode at that point.  */
 401   int *heights = (int *) alloca (ax->len * sizeof (heights[0]));
 402
 403   /* Pointer to a description of the present op.  */
 404   struct aop_map *op;
 405
 406   memset (reg_mask, 0, reg_mask_len * sizeof (reg_mask[0]));
 407   memset (targets, 0, ax->len * sizeof (targets[0]));
 408   memset (boundary, 0, ax->len * sizeof (boundary[0]));
 409
 410   reqs->max_height = reqs->min_height = height = 0;
 411   reqs->flaw = agent_flaw_none;
 412   reqs->max_data_size = 0;
 413
 414   for (i = 0; i < ax->len; i += 1 + op->op_size)
 415     {
 416       if (ax->buf[i] > (sizeof (aop_map) / sizeof (aop_map[0])))
 417         {
 418           reqs->flaw = agent_flaw_bad_instruction;
 419           xfree (reg_mask);
 420           return;
 421         }
 422
 423       op = &aop_map[ax->buf[i]];
 424
 425       if (!op->name)
 426         {
 427           reqs->flaw = agent_flaw_bad_instruction;
 428           xfree (reg_mask);
 429           return;
 430         }
 431
 432       if (i + 1 + op->op_size > ax->len)
 433         {
 434           reqs->flaw = agent_flaw_incomplete_instruction;
 435           xfree (reg_mask);
 436           return;
 437         }
 438
 439       /* If this instruction is a jump target, does the current stack
 440          height match the stack height at the jump source?  */
 441       if (targets[i] && (heights[i] != height))
 442         {
 443           reqs->flaw = agent_flaw_height_mismatch;
 444           xfree (reg_mask);
 445           return;
 446         }
 447
 448       boundary[i] = 1;
 449       heights[i] = height;
 450
 451       height -= op->consumed;
 452       if (height < reqs->min_height)
 453         reqs->min_height = height;
 454       height += op->produced;
 455       if (height > reqs->max_height)
 456         reqs->max_height = height;
 457
 458       if (op->data_size > reqs->max_data_size)
 459         reqs->max_data_size = op->data_size;
 460
 461       /* For jump instructions, check that the target is a valid
 462          offset.  If it is, record the fact that that location is a
 463          jump target, and record the height we expect there.  */
 464       if (aop_goto == op - aop_map
 465           || aop_if_goto == op - aop_map)
 466         {
 467           int target = read_const (ax, i + 1, 2);
 468           if (target < 0 || target >= ax->len)
 469             {
 470               reqs->flaw = agent_flaw_bad_jump;
 471               xfree (reg_mask);
 472               return;
 473             }
 474           /* Have we already found other jumps to the same location?  */
 475           else if (targets[target])
 476             {
 477               if (heights[i] != height)
 478                 {
 479                   reqs->flaw = agent_flaw_height_mismatch;
 480                   xfree (reg_mask);
 481                   return;
 482                 }
 483             }
 484           else
 485             {
 486               targets[target] = 1;
 487               heights[target] = height;
 488             }
 489         }
 490
 491       /* For unconditional jumps with a successor, check that the
 492          successor is a target, and pick up its stack height.  */
 493       if (aop_goto == op - aop_map
 494           && i + 3 < ax->len)
 495         {
 496           if (!targets[i + 3])
 497             {
 498               reqs->flaw = agent_flaw_hole;
 499               xfree (reg_mask);
 500               return;
 501             }
 502
 503           height = heights[i + 3];
 504         }
 505
 506       /* For reg instructions, record the register in the bit mask.  */
 507       if (aop_reg == op - aop_map)
 508         {
 509           int reg = read_const (ax, i + 1, 2);
 510           int byte = reg / 8;
 511
 512           /* Grow the bit mask if necessary.  */
 513           if (byte >= reg_mask_len)
 514             {
 515               /* It's not appropriate to double here.  This isn't a
 516                  string buffer.  */
 517               int new_len = byte + 1;
 518               reg_mask = xrealloc (reg_mask,
 519                                    new_len * sizeof (reg_mask[0]));
 520               memset (reg_mask + reg_mask_len, 0,
 521                       (new_len - reg_mask_len) * sizeof (reg_mask[0]));
 522               reg_mask_len = new_len;
 523             }
 524
 525           reg_mask[byte] |= 1 << (reg % 8);
 526         }
 527     }
 528
 529   /* Check that all the targets are on boundaries.  */
 530   for (i = 0; i < ax->len; i++)
 531     if (targets[i] && !boundary[i])
 532       {
 533         reqs->flaw = agent_flaw_bad_jump;
 534         xfree (reg_mask);
 535         return;
 536       }
 537
 538   reqs->final_height = height;
 539   reqs->reg_mask_len = reg_mask_len;
 540   reqs->reg_mask = reg_mask;
 541 }