mingw/html/lib/Opcode.html

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  13 <big><strong><span class="block">&nbsp;Opcode - Disable named opcodes when compiling perl code</span></strong></big>
  14 </td></tr>
  15 </table>
  16
  17 <p><a name="__index__"></a></p>
  18 <!-- INDEX BEGIN -->
  19
  20 <ul>
  21
  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#note">NOTE</a></li>
  26         <li><a href="#warning">WARNING</a></li>
  27         <li><a href="#operator_names_and_operator_lists">Operator Names and Operator Lists</a></li>
  28         <li><a href="#opcode_functions">Opcode Functions</a></li>
  29         <li><a href="#manipulating_opsets">Manipulating Opsets</a></li>
  30         <li><a href="#to_do__maybe_">TO DO (maybe)</a></li>
  31         <li><a href="#predefined_opcode_tags">Predefined Opcode Tags</a></li>
  32         <li><a href="#see_also">SEE ALSO</a></li>
  33         <li><a href="#authors">AUTHORS</a></li>
  34 </ul>
  35 <!-- INDEX END -->
  36
  37 <hr />
  38 <p>
  39 </p>
  40 <h1><a name="name">NAME</a></h1>
  41 <p>Opcode - Disable named opcodes when compiling perl code</p>
  42 <p>
  43 </p>
  44 <hr />
  45 <h1><a name="synopsis">SYNOPSIS</a></h1>
  46 <pre>
  47   use Opcode;</pre>
  48 <p>
  49 </p>
  50 <hr />
  51 <h1><a name="description">DESCRIPTION</a></h1>
  52 <p>Perl code is always compiled into an internal format before execution.</p>
  53 <p>Evaluating perl code (e.g. via ``eval'' or ``do 'file''') causes
  54 the code to be compiled into an internal format and then,
  55 provided there was no error in the compilation, executed.
  56 The internal format is based on many distinct <em>opcodes</em>.</p>
  57 <p>By default no opmask is in effect and any code can be compiled.</p>
  58 <p>The Opcode module allow you to define an <em>operator mask</em> to be in
  59 effect when perl <em>next</em> compiles any code.  Attempting to compile code
  60 which contains a masked opcode will cause the compilation to fail
  61 with an error. The code will not be executed.</p>
  62 <p>
  63 </p>
  64 <hr />
  65 <h1><a name="note">NOTE</a></h1>
  66 <p>The Opcode module is not usually used directly. See the ops pragma and
  67 Safe modules for more typical uses.</p>
  68 <p>
  69 </p>
  70 <hr />
  71 <h1><a name="warning">WARNING</a></h1>
  72 <p>The authors make <strong>no warranty</strong>, implied or otherwise, about the
  73 suitability of this software for safety or security purposes.</p>
  74 <p>The authors shall not in any case be liable for special, incidental,
  75 consequential, indirect or other similar damages arising from the use
  76 of this software.</p>
  77 <p>Your mileage will vary. If in any doubt <strong>do not use it</strong>.</p>
  78 <p>
  79 </p>
  80 <hr />
  81 <h1><a name="operator_names_and_operator_lists">Operator Names and Operator Lists</a></h1>
  82 <p>The canonical list of operator names is the contents of the array
  83 PL_op_name defined and initialised in file <em>opcode.h</em> of the Perl
  84 source distribution (and installed into the perl library).</p>
  85 <p>Each operator has both a terse name (its opname) and a more verbose or
  86 recognisable descriptive name. The opdesc function can be used to
  87 return a list of descriptions for a list of operators.</p>
  88 <p>Many of the functions and methods listed below take a list of
  89 operators as parameters. Most operator lists can be made up of several
  90 types of element. Each element can be one of</p>
  91 <dl>
  92 <dt><strong><a name="item_name">an operator name (opname)</a></strong>
  93
  94 <dd>
  95 <p>Operator names are typically small lowercase words like enterloop,
  96 leaveloop, last, next, redo etc. Sometimes they are rather cryptic
  97 like gv2cv, i_ncmp and ftsvtx.</p>
  98 </dd>
  99 </li>
 100 <dt><strong>an operator tag name (optag)</strong>
 101
 102 <dd>
 103 <p>Operator tags can be used to refer to groups (or sets) of operators.
 104 Tag names always begin with a colon. The Opcode module defines several
 105 optags and the user can define others using the define_optag function.</p>
 106 </dd>
 107 </li>
 108 <dt><strong><a name="item_a_negated_opname_or_optag">a negated opname or optag</a></strong>
 109
 110 <dd>
 111 <p>An opname or optag can be prefixed with an exclamation mark, e.g., !mkdir.
 112 Negating an opname or optag means remove the corresponding ops from the
 113 accumulated set of ops at that point.</p>
 114 </dd>
 115 </li>
 116 <dt><strong><a name="item_set">an operator set (opset)</a></strong>
 117
 118 <dd>
 119 <p>An <em>opset</em> as a binary string of approximately 44 bytes which holds a
 120 set or zero or more operators.</p>
 121 </dd>
 122 <dd>
 123 <p>The opset and opset_to_ops functions can be used to convert from
 124 a list of operators to an opset and <em>vice versa</em>.</p>
 125 </dd>
 126 <dd>
 127 <p>Wherever a list of operators can be given you can use one or more opsets.
 128 See also Manipulating Opsets below.</p>
 129 </dd>
 130 </li>
 131 </dl>
 132 <p>
 133 </p>
 134 <hr />
 135 <h1><a name="opcode_functions">Opcode Functions</a></h1>
 136 <p>The Opcode package contains functions for manipulating operator names
 137 tags and sets. All are available for export by the package.</p>
 138 <dl>
 139 <dt><strong><a name="item_opcodes">opcodes</a></strong>
 140
 141 <dd>
 142 <p>In a scalar context opcodes returns the number of opcodes in this
 143 version of perl (around 350 for perl-5.7.0).</p>
 144 </dd>
 145 <dd>
 146 <p>In a list context it returns a list of all the operator names.
 147 (Not yet implemented, use @names = <a href="#item_opset_to_ops"><code>opset_to_ops(full_opset).)</code></a></p>
 148 </dd>
 149 </li>
 150 <dt><strong><a name="item_opset">opset (OP, ...)</a></strong>
 151
 152 <dd>
 153 <p>Returns an opset containing the listed operators.</p>
 154 </dd>
 155 </li>
 156 <dt><strong><a name="item_opset_to_ops">opset_to_ops (OPSET)</a></strong>
 157
 158 <dd>
 159 <p>Returns a list of operator names corresponding to those operators in
 160 the set.</p>
 161 </dd>
 162 </li>
 163 <dt><strong><a name="item_opset_to_hex">opset_to_hex (OPSET)</a></strong>
 164
 165 <dd>
 166 <p>Returns a string representation of an opset. Can be handy for debugging.</p>
 167 </dd>
 168 </li>
 169 <dt><strong><a name="item_full_opset">full_opset</a></strong>
 170
 171 <dd>
 172 <p>Returns an opset which includes all operators.</p>
 173 </dd>
 174 </li>
 175 <dt><strong><a name="item_empty_opset">empty_opset</a></strong>
 176
 177 <dd>
 178 <p>Returns an opset which contains no operators.</p>
 179 </dd>
 180 </li>
 181 <dt><strong><a name="item_invert_opset">invert_opset (OPSET)</a></strong>
 182
 183 <dd>
 184 <p>Returns an opset which is the inverse set of the one supplied.</p>
 185 </dd>
 186 </li>
 187 <dt><strong><a name="item_verify_opset">verify_opset (OPSET, ...)</a></strong>
 188
 189 <dd>
 190 <p>Returns true if the supplied opset looks like a valid opset (is the
 191 right length etc) otherwise it returns false. If an optional second
 192 parameter is true then verify_opset will croak on an invalid opset
 193 instead of returning false.</p>
 194 </dd>
 195 <dd>
 196 <p>Most of the other Opcode functions call verify_opset automatically
 197 and will croak if given an invalid opset.</p>
 198 </dd>
 199 </li>
 200 <dt><strong><a name="item_define_optag">define_optag (OPTAG, OPSET)</a></strong>
 201
 202 <dd>
 203 <p>Define OPTAG as a symbolic name for OPSET. Optag names always start
 204 with a colon <code>:</code>.</p>
 205 </dd>
 206 <dd>
 207 <p>The optag name used must not be defined already (define_optag will
 208 croak if it is already defined). Optag names are global to the perl
 209 process and optag definitions cannot be altered or deleted once
 210 defined.</p>
 211 </dd>
 212 <dd>
 213 <p>It is strongly recommended that applications using Opcode should use a
 214 leading capital letter on their tag names since lowercase names are
 215 reserved for use by the Opcode module. If using Opcode within a module
 216 you should prefix your tags names with the name of your module to
 217 ensure uniqueness and thus avoid clashes with other modules.</p>
 218 </dd>
 219 </li>
 220 <dt><strong><a name="item_opmask_add">opmask_add (OPSET)</a></strong>
 221
 222 <dd>
 223 <p>Adds the supplied opset to the current opmask. Note that there is
 224 currently <em>no</em> mechanism for unmasking ops once they have been masked.
 225 This is intentional.</p>
 226 </dd>
 227 </li>
 228 <dt><strong><a name="item_opmask">opmask</a></strong>
 229
 230 <dd>
 231 <p>Returns an opset corresponding to the current opmask.</p>
 232 </dd>
 233 </li>
 234 <dt><strong><a name="item_opdesc">opdesc (OP, ...)</a></strong>
 235
 236 <dd>
 237 <p>This takes a list of operator names and returns the corresponding list
 238 of operator descriptions.</p>
 239 </dd>
 240 </li>
 241 <dt><strong><a name="item_opdump">opdump (PAT)</a></strong>
 242
 243 <dd>
 244 <p>Dumps to STDOUT a two column list of op names and op descriptions.
 245 If an optional pattern is given then only lines which match the
 246 (case insensitive) pattern will be output.</p>
 247 </dd>
 248 <dd>
 249 <p>It's designed to be used as a handy command line utility:</p>
 250 </dd>
 251 <dd>
 252 <pre>
 253         perl -MOpcode=opdump -e opdump
 254         perl -MOpcode=opdump -e 'opdump Eval'</pre>
 255 </dd>
 256 </li>
 257 </dl>
 258 <p>
 259 </p>
 260 <hr />
 261 <h1><a name="manipulating_opsets">Manipulating Opsets</a></h1>
 262 <p>Opsets may be manipulated using the perl bit vector operators &amp; (and), | (or),
 263 ^ (xor) and ~ (negate/invert).</p>
 264 <p>However you should never rely on the numerical position of any opcode
 265 within the opset. In other words both sides of a bit vector operator
 266 should be opsets returned from Opcode functions.</p>
 267 <p>Also, since the number of opcodes in your current version of perl might
 268 not be an exact multiple of eight, there may be unused bits in the last
 269 byte of an upset. This should not cause any problems (Opcode functions
 270 ignore those extra bits) but it does mean that using the ~ operator
 271 will typically not produce the same 'physical' opset 'string' as the
 272 invert_opset function.</p>
 273 <p>
 274 </p>
 275 <hr />
 276 <h1><a name="to_do__maybe_">TO DO (maybe)</a></h1>
 277 <pre>
 278     $bool = opset_eq($opset1, $opset2)  true if opsets are logically eqiv</pre>
 279 <pre>
 280     $yes = opset_can($opset, @ops)      true if $opset has all @ops set</pre>
 281 <pre>
 282     @diff = opset_diff($opset1, $opset2) =&gt; ('foo', '!bar', ...)</pre>
 283 <p>
 284 </p>
 285 <hr />
 286 <h1><a name="predefined_opcode_tags">Predefined Opcode Tags</a></h1>
 287 <dl>
 288 <dt><strong><a name="item__3abase_core">:base_core</a></strong>
 289
 290 <dd>
 291 <pre>
 292     null stub scalar pushmark wantarray const defined undef</pre>
 293 </dd>
 294 <dd>
 295 <pre>
 296     rv2sv sassign</pre>
 297 </dd>
 298 <dd>
 299 <pre>
 300     rv2av aassign aelem aelemfast aslice av2arylen</pre>
 301 </dd>
 302 <dd>
 303 <pre>
 304     rv2hv helem hslice each values keys exists delete</pre>
 305 </dd>
 306 <dd>
 307 <pre>
 308     preinc i_preinc predec i_predec postinc i_postinc postdec i_postdec
 309     int hex oct abs pow multiply i_multiply divide i_divide
 310     modulo i_modulo add i_add subtract i_subtract</pre>
 311 </dd>
 312 <dd>
 313 <pre>
 314     left_shift right_shift bit_and bit_xor bit_or negate i_negate
 315     not complement</pre>
 316 </dd>
 317 <dd>
 318 <pre>
 319     lt i_lt gt i_gt le i_le ge i_ge eq i_eq ne i_ne ncmp i_ncmp
 320     slt sgt sle sge seq sne scmp</pre>
 321 </dd>
 322 <dd>
 323 <pre>
 324     substr vec stringify study pos length index rindex ord chr</pre>
 325 </dd>
 326 <dd>
 327 <pre>
 328     ucfirst lcfirst uc lc quotemeta trans chop schop chomp schomp</pre>
 329 </dd>
 330 <dd>
 331 <pre>
 332     match split qr</pre>
 333 </dd>
 334 <dd>
 335 <pre>
 336     list lslice splice push pop shift unshift reverse</pre>
 337 </dd>
 338 <dd>
 339 <pre>
 340     cond_expr flip flop andassign orassign and or xor</pre>
 341 </dd>
 342 <dd>
 343 <pre>
 344     warn die lineseq nextstate scope enter leave setstate</pre>
 345 </dd>
 346 <dd>
 347 <pre>
 348     rv2cv anoncode prototype</pre>
 349 </dd>
 350 <dd>
 351 <pre>
 352     entersub leavesub leavesublv return method method_named -- XXX loops via recursion?</pre>
 353 </dd>
 354 <dd>
 355 <pre>
 356     leaveeval -- needed for Safe to operate, is safe without entereval</pre>
 357 </dd>
 358 <dt><strong><a name="item__3abase_mem">:base_mem</a></strong>
 359
 360 <dd>
 361 <p>These memory related ops are not included in :base_core because they
 362 can easily be used to implement a resource attack (e.g., consume all
 363 available memory).</p>
 364 </dd>
 365 <dd>
 366 <pre>
 367     concat repeat join range</pre>
 368 </dd>
 369 <dd>
 370 <pre>
 371     anonlist anonhash</pre>
 372 </dd>
 373 <dd>
 374 <p>Note that despite the existence of this optag a memory resource attack
 375 may still be possible using only :base_core ops.</p>
 376 </dd>
 377 <dd>
 378 <p>Disabling these ops is a <em>very</em> heavy handed way to attempt to prevent
 379 a memory resource attack. It's probable that a specific memory limit
 380 mechanism will be added to perl in the near future.</p>
 381 </dd>
 382 </li>
 383 <dt><strong><a name="item__3abase_loop">:base_loop</a></strong>
 384
 385 <dd>
 386 <p>These loop ops are not included in :base_core because they can easily be
 387 used to implement a resource attack (e.g., consume all available CPU time).</p>
 388 </dd>
 389 <dd>
 390 <pre>
 391     grepstart grepwhile
 392     mapstart mapwhile
 393     enteriter iter
 394     enterloop leaveloop unstack
 395     last next redo
 396     goto</pre>
 397 </dd>
 398 </li>
 399 <dt><strong><a name="item__3abase_io">:base_io</a></strong>
 400
 401 <dd>
 402 <p>These ops enable <em>filehandle</em> (rather than filename) based input and
 403 output. These are safe on the assumption that only pre-existing
 404 filehandles are available for use.  To create new filehandles other ops
 405 such as open would need to be enabled.</p>
 406 </dd>
 407 <dd>
 408 <pre>
 409     readline rcatline getc read</pre>
 410 </dd>
 411 <dd>
 412 <pre>
 413     formline enterwrite leavewrite</pre>
 414 </dd>
 415 <dd>
 416 <pre>
 417     print sysread syswrite send recv</pre>
 418 </dd>
 419 <dd>
 420 <pre>
 421     eof tell seek sysseek</pre>
 422 </dd>
 423 <dd>
 424 <pre>
 425     readdir telldir seekdir rewinddir</pre>
 426 </dd>
 427 </li>
 428 <dt><strong><a name="item__3abase_orig">:base_orig</a></strong>
 429
 430 <dd>
 431 <p>These are a hotchpotch of opcodes still waiting to be considered</p>
 432 </dd>
 433 <dd>
 434 <pre>
 435     gvsv gv gelem</pre>
 436 </dd>
 437 <dd>
 438 <pre>
 439     padsv padav padhv padany</pre>
 440 </dd>
 441 <dd>
 442 <pre>
 443     rv2gv refgen srefgen ref</pre>
 444 </dd>
 445 <dd>
 446 <pre>
 447     bless -- could be used to change ownership of objects (reblessing)</pre>
 448 </dd>
 449 <dd>
 450 <pre>
 451     pushre regcmaybe regcreset regcomp subst substcont</pre>
 452 </dd>
 453 <dd>
 454 <pre>
 455     sprintf prtf -- can core dump</pre>
 456 </dd>
 457 <dd>
 458 <pre>
 459     crypt</pre>
 460 </dd>
 461 <dd>
 462 <pre>
 463     tie untie</pre>
 464 </dd>
 465 <dd>
 466 <pre>
 467     dbmopen dbmclose
 468     sselect select
 469     pipe_op sockpair</pre>
 470 </dd>
 471 <dd>
 472 <pre>
 473     getppid getpgrp setpgrp getpriority setpriority localtime gmtime</pre>
 474 </dd>
 475 <dd>
 476 <pre>
 477     entertry leavetry -- can be used to 'hide' fatal errors</pre>
 478 </dd>
 479 <dd>
 480 <pre>
 481     custom -- where should this go</pre>
 482 </dd>
 483 </li>
 484 <dt><strong><a name="item__3abase_math">:base_math</a></strong>
 485
 486 <dd>
 487 <p>These ops are not included in :base_core because of the risk of them being
 488 used to generate floating point exceptions (which would have to be caught
 489 using a $SIG{FPE} handler).</p>
 490 </dd>
 491 <dd>
 492 <pre>
 493     atan2 sin cos exp log sqrt</pre>
 494 </dd>
 495 <dd>
 496 <p>These ops are not included in :base_core because they have an effect
 497 beyond the scope of the compartment.</p>
 498 </dd>
 499 <dd>
 500 <pre>
 501     rand srand</pre>
 502 </dd>
 503 </li>
 504 <dt><strong><a name="item__3abase_thread">:base_thread</a></strong>
 505
 506 <dd>
 507 <p>These ops are related to multi-threading.</p>
 508 </dd>
 509 <dd>
 510 <pre>
 511     lock threadsv</pre>
 512 </dd>
 513 </li>
 514 <dt><strong><a name="item__3adefault">:default</a></strong>
 515
 516 <dd>
 517 <p>A handy tag name for a <em>reasonable</em> default set of ops.  (The current ops
 518 allowed are unstable while development continues. It will change.)</p>
 519 </dd>
 520 <dd>
 521 <pre>
 522     :base_core :base_mem :base_loop :base_io :base_orig :base_thread</pre>
 523 </dd>
 524 <dd>
 525 <p>If safety matters to you (and why else would you be using the Opcode module?)
 526 then you should not rely on the definition of this, or indeed any other, optag!</p>
 527 </dd>
 528 </li>
 529 <dt><strong><a name="item__3afilesys_read">:filesys_read</a></strong>
 530
 531 <dd>
 532 <pre>
 533     stat lstat readlink</pre>
 534 </dd>
 535 <dd>
 536 <pre>
 537     ftatime ftblk ftchr ftctime ftdir fteexec fteowned fteread
 538     ftewrite ftfile ftis ftlink ftmtime ftpipe ftrexec ftrowned
 539     ftrread ftsgid ftsize ftsock ftsuid fttty ftzero ftrwrite ftsvtx</pre>
 540 </dd>
 541 <dd>
 542 <pre>
 543     fttext ftbinary</pre>
 544 </dd>
 545 <dd>
 546 <pre>
 547     fileno</pre>
 548 </dd>
 549 <dt><strong><a name="item__3asys_db">:sys_db</a></strong>
 550
 551 <dd>
 552 <pre>
 553     ghbyname ghbyaddr ghostent shostent ehostent      -- hosts
 554     gnbyname gnbyaddr gnetent snetent enetent         -- networks
 555     gpbyname gpbynumber gprotoent sprotoent eprotoent -- protocols
 556     gsbyname gsbyport gservent sservent eservent      -- services</pre>
 557 </dd>
 558 <dd>
 559 <pre>
 560     gpwnam gpwuid gpwent spwent epwent getlogin       -- users
 561     ggrnam ggrgid ggrent sgrent egrent                -- groups</pre>
 562 </dd>
 563 <dt><strong><a name="item__3abrowse">:browse</a></strong>
 564
 565 <dd>
 566 <p>A handy tag name for a <em>reasonable</em> default set of ops beyond the
 567 :default optag.  Like :default (and indeed all the other optags) its
 568 current definition is unstable while development continues. It will change.</p>
 569 </dd>
 570 <dd>
 571 <p>The :browse tag represents the next step beyond :default. It it a
 572 superset of the :default ops and adds :filesys_read the :sys_db.
 573 The intent being that scripts can access more (possibly sensitive)
 574 information about your system but not be able to change it.</p>
 575 </dd>
 576 <dd>
 577 <pre>
 578     :default :filesys_read :sys_db</pre>
 579 </dd>
 580 </li>
 581 <dt><strong><a name="item__3afilesys_open">:filesys_open</a></strong>
 582
 583 <dd>
 584 <pre>
 585     sysopen open close
 586     umask binmode</pre>
 587 </dd>
 588 <dd>
 589 <pre>
 590     open_dir closedir -- other dir ops are in :base_io</pre>
 591 </dd>
 592 <dt><strong><a name="item__3afilesys_write">:filesys_write</a></strong>
 593
 594 <dd>
 595 <pre>
 596     link unlink rename symlink truncate</pre>
 597 </dd>
 598 <dd>
 599 <pre>
 600     mkdir rmdir</pre>
 601 </dd>
 602 <dd>
 603 <pre>
 604     utime chmod chown</pre>
 605 </dd>
 606 <dd>
 607 <pre>
 608     fcntl -- not strictly filesys related, but possibly as dangerous?</pre>
 609 </dd>
 610 <dt><strong><a name="item__3asubprocess">:subprocess</a></strong>
 611
 612 <dd>
 613 <pre>
 614     backtick system</pre>
 615 </dd>
 616 <dd>
 617 <pre>
 618     fork</pre>
 619 </dd>
 620 <dd>
 621 <pre>
 622     wait waitpid</pre>
 623 </dd>
 624 <dd>
 625 <pre>
 626     glob -- access to Cshell via &lt;`rm *`&gt;</pre>
 627 </dd>
 628 <dt><strong><a name="item__3aownprocess">:ownprocess</a></strong>
 629
 630 <dd>
 631 <pre>
 632     exec exit kill</pre>
 633 </dd>
 634 <dd>
 635 <pre>
 636     time tms -- could be used for timing attacks (paranoid?)</pre>
 637 </dd>
 638 <dt><strong><a name="item__3aothers">:others</a></strong>
 639
 640 <dd>
 641 <p>This tag holds groups of assorted specialist opcodes that don't warrant
 642 having optags defined for them.</p>
 643 </dd>
 644 <dd>
 645 <p>SystemV Interprocess Communications:</p>
 646 </dd>
 647 <dd>
 648 <pre>
 649     msgctl msgget msgrcv msgsnd</pre>
 650 </dd>
 651 <dd>
 652 <pre>
 653     semctl semget semop</pre>
 654 </dd>
 655 <dd>
 656 <pre>
 657     shmctl shmget shmread shmwrite</pre>
 658 </dd>
 659 </li>
 660 <dt><strong><a name="item__3astill_to_be_decided">:still_to_be_decided</a></strong>
 661
 662 <dd>
 663 <pre>
 664     chdir
 665     flock ioctl</pre>
 666 </dd>
 667 <dd>
 668 <pre>
 669     socket getpeername ssockopt
 670     bind connect listen accept shutdown gsockopt getsockname</pre>
 671 </dd>
 672 <dd>
 673 <pre>
 674     sleep alarm -- changes global timer state and signal handling
 675     sort -- assorted problems including core dumps
 676     tied -- can be used to access object implementing a tie
 677     pack unpack -- can be used to create/use memory pointers</pre>
 678 </dd>
 679 <dd>
 680 <pre>
 681     entereval -- can be used to hide code from initial compile
 682     require dofile</pre>
 683 </dd>
 684 <dd>
 685 <pre>
 686     caller -- get info about calling environment and args</pre>
 687 </dd>
 688 <dd>
 689 <pre>
 690     reset</pre>
 691 </dd>
 692 <dd>
 693 <pre>
 694     dbstate -- perl -d version of nextstate(ment) opcode</pre>
 695 </dd>
 696 <dt><strong><a name="item__3adangerous">:dangerous</a></strong>
 697
 698 <dd>
 699 <p>This tag is simply a bucket for opcodes that are unlikely to be used via
 700 a tag name but need to be tagged for completeness and documentation.</p>
 701 </dd>
 702 <dd>
 703 <pre>
 704     syscall dump chroot</pre>
 705 </dd>
 706 </li>
 707 </dl>
 708 <p>
 709 </p>
 710 <hr />
 711 <h1><a name="see_also">SEE ALSO</a></h1>
 712 <p><code>ops(3)</code> -- perl pragma interface to Opcode module.</p>
 713 <p><code>Safe(3)</code> -- Opcode and namespace limited execution compartments</p>
 714 <p>
 715 </p>
 716 <hr />
 717 <h1><a name="authors">AUTHORS</a></h1>
 718 <p>Originally designed and implemented by Malcolm Beattie,
 719 <a href="mailto:mbeattie@sable.ox.ac.uk">mbeattie@sable.ox.ac.uk</a> as part of Safe version 1.</p>
 720 <p>Split out from Safe module version 1, named opcode tags and other
 721 changes added by Tim Bunce.</p>
 722 <table border="0" width="100%" cellspacing="0" cellpadding="3">
 723 <tr><td class="block" style="background-color: #cccccc" valign="middle">
 724 <big><strong><span class="block">&nbsp;Opcode - Disable named opcodes when compiling perl code</span></strong></big>
 725 </td></tr>
 726 </table>
 727
 728 </body>
 729
 730 </html>