project/captive/doc/APITypes.pm

   1 # $Id$
   2 # Captive project doc APITypes page Perl template.
   3 # Copyright (C) 2003-2005 Jan Kratochvil <project-www.jankratochvil.net@jankratochvil.net>
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License as published by
   7 # the Free Software Foundation; exactly version 2 of June 1991 is required
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU General Public License
  15 # along with this program; if not, write to the Free Software
  16 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17
  18
  19 package project::captive::doc::APITypes;
  20 require 5.6.0;  # at least 'use warnings;' but we need some 5.6.0+ modules anyway
  21 our $VERSION=do { my @r=(q$Revision$=~/\d+/g); sprintf "%d.".("%03d"x$#r),@r; };
  22 our $CVS_ID=q$Id$;
  23 use strict;
  24 use warnings;
  25
  26 use My::Web;
  27 require CGI;
  28 BEGIN { Wuse 'project::captive::doc::Macros'; }
  29
  30
  31 sub handler
  32 {
  33 project::captive::doc::Macros->init(
  34                 "title"=>'Captive NTFS Developer Documentation: API Functions',
  35                 "rel_prev"=>'Details.pm',
  36                 "rel_next"=>'CallType.pm',
  37                 );
  38
  39
  40 print <<"HERE";
  41
  42
  43 <h1 id="functype">API Function Implementation Choices</h1>
  44
  45         <p>For each function exported by W32
  46         <span class="fname">ntoskrnl.exe</span> and imported and called by the
  47         filesystem driver a decision needs to be made to properly implement its
  48         functionality. Currently implemented functionality statistics are provided
  49         below:</p>
  50
  51         <table border="0" width="100%"><tr><td align="center"><table border="1">
  52                 <caption>Function Implementation Types Statistics</caption>
  53                 <tr><th>Function type                                            </th><th>Items</th><th>Portion</th></tr>
  54                 <tr><td>@{[ a_href 'APITypes.pm#functype_pass','pass' ]}                    </td><td>   81</td><td>    26%</td></tr>
  55                 <tr><td>@{[ a_href 'APITypes.pm#functype_wrap','wrap' ]}                    </td><td>    2</td><td>     0%</td></tr>
  56                 <tr><td>@{[ a_href 'APITypes.pm#functype_native_reactos','native-ReactOS' ]}</td><td>  113</td><td>    36%</td></tr>
  57                 <tr><td>@{[ a_href 'APITypes.pm#functype_native_libcaptive','native-own' ]} </td><td>  116</td><td>    38%</td></tr>
  58         </table></td></tr></table>
  59
  60         @{[ doc_img 'ratio','Functions Reusal Ratio' ]}
  61
  62         <p>As there are several choices to implement each function the usual
  63         attempts/investigations ordering is listed in the sections below.</p>
  64
  65         <p>Special case must be taken for data-type symbols since they are
  66         referenced without the possibility of catching the code flow by some
  67         breakpoints (it would be possible only in some special access cases). Data
  68         export symbols of <span class="constant">unpatched</span> libraries must
  69         contain already prepared content at the runtime. There is a&nbsp;problem
  70         with <span class="constant">patched</span> libraries where it is necessary
  71         to also fully implement the data symbol as
  72         @{[ a_href 'APITypes.pm#functype_native','native implementation' ]} since there is no
  73         possibility to @{[ a_href 'APITypes.pm#functype_pass','pass' ]} the data symbol instead of
  74         the original W32 data location and therefore there will be two instances of
  75         such data variable place. As there will be also the uncaught references for
  76         such W32 data location from the <span class="constant">patched</span>
  77         library itself such symbols should be usually only some constants (such as
  78         <span class="constant">KeNumberProcessors</span>).</p>
  79
  80         <p>W32 platform symbols export/import can be based either on the symbol
  81         name itself or it can be also exported and imported just by its
  82         identification number called <span class="constant">Ordinal</span>.
  83         Although it saves some jumptables file binary size it is currently no
  84         longer used by W32 binaries and this project also does not support such
  85         <span class="constant">Ordinal</span> symbol reference type at all.</p>
  86
  87         <p>All the exporting magic is handled by custom script
  88         <span class="fname">captivesym</span> processing the definition file
  89         <span class="fname">@{[ captive_srcfile 'src/libcaptive/ke/exports.captivesym' ]}</span>
  90         to produce the intermediate relaying code
  91         <span class="fname">src/libcaptive/ke/exports.c</span>. For details of the
  92         <span class="fname">captivesym</span>-specific source file syntax please
  93         see its documentation:
  94         <span class="fname">@{[ a_href
  95                         '/project/Pod2Html.pm?cvs=captive/src/libcaptive/ke/captivesym.pl',
  96                         'src/libcaptive/ke/captivesym.pl' ]}</span>
  97         </p>
  98
  99         <h2 id="functype_pass">Direct Pass to Original &quot;ntoskrnl.exe&quot;</h2>
 100
 101                 <p>Simple (standalone) functions such as
 102                 <span class="function">RtlTimeToSecondsSince1970()</span> can be simply
 103                 passed to the original implementation in
 104                 <span class="fname">ntoskrnl.exe</span> as they make no hardware access
 105                 and they do not expect any special internal data structures to be set up
 106                 in advance by an earlier library initialization. A common case are all
 107                 the data structures utility functions such as
 108                 <span class="constant">GenericTable</span> subsystem or
 109                 <span class="constant">LargeMcb</span> handling.</p>
 110
 111                 <h3 id="functype_pass_fromunix">Pass from UNIX Code</h3>
 112
 113                         <p>Control flow begins in some standard UNIX code. Such code is always
 114                         using @{[ a_href 'CallType.pm#calltype_cdecl','cdecl call type' ]} for all its
 115                         intracalls. <a href="APITypes.pm#functype_native_reactos">Native functions
 116                         compiled from <span class="productname">ReactOS</span> sources</a> use
 117                         their own @{[ a_href '#calltype','cdecl/stdcall/fastcall' ]} declarations
 118                         but these call type modifications are discarded during compilation for
 119                         this project by the <span class="constant">LIBCAPTIVE</span>
 120                         symbol.</p>
 121
 122                         <p>UNIX code calls <span class="function">FUNCTIONNAME()</span> relay
 123                         from the generated UNIX jump table. Such relay will debug dump the
 124                         passed arguments and finally pass the control to the original W32
 125                         function code in the proper call type
 126                         @{[ a_href '#calltype','cdecl/stdcall/fastcall' ]} for a&nbsp;given
 127                         function.</p>
 128
 129                         <p>Original W32 code entry point is always trapped by a&nbsp;breakpoint
 130                         although it would not be needed during this specific direct pass from
 131                         UNIX code to the original W32 implementation. Still the breakpoint has
 132                         to be there to catch some other (such as intra-W32) possible calls
 133                         described later. There are several more ways to define breakpoint in
 134                         the code. One way is to use processor hardware breakpoint support but
 135                         the number of breakpoints is limited.  The other way is to patch in the
 136                         <span class="instruction">@{[ 'int $3' ]}</span> instruction but it will invoke
 137                         <span class="constant">SIGTRAP</span> signal handler conflicting with
 138                         the possible debugger (<span class="productname">gdb(1)</span>)
 139                         control. This project uses the <span class="instruction">hlt</span>
 140                         instruction, which also has a&nbsp;single-byte opcode as
 141                         <span class="instruction">@{[ 'int $3' ]}</span> and it is a&nbsp;privileged
 142                         instruction forbidden to be used from the UNIX user space code.
 143                         <span class="instruction">hlt</span> invokes
 144                         <span class="constant">SIGSEGV</span> signal which can be resolved by
 145                         a&nbsp;custom signal handler without any conflict with the possible
 146                         debugger control; <span class="productname">gdb(1)</span> needs the
 147                         following command to pass through such
 148                         <span class="constant">SIGSEGV</span> signal:</p>
 149
 150                         <blockquote class="command">
 151                                 <p>handle SIGSEGV nostop noprint pass</p>
 152                         </blockquote>
 153
 154                         <p>When a breakpoint gets caught, we usually need to return to the
 155                         running code. Unfortunately it is not possible because of the patched
 156                         breakpoint opcode. The breakpoint cannot be simply removed upon return
 157                         as it would permanently loose control over the point of entry. Even if
 158                         the return would include faking of the return address in the bottom
 159                         stack frame to patch the breakpoint back during later function exit it
 160                         still would not solve the caughts of inner calls of recursive
 161                         functions. One of the working possibilities would be to patch the
 162                         original instruction back and perform a&nbsp;singlestep provided by
 163                         <span class="function">ptrace(2)</span> syscall. However such
 164                         singlestep needs another controlling UNIX process and it would again
 165                         conflict with the debuggers such as
 166                         <span class="productname">gdb(1)</span>. This project implements the
 167                         singlestep functionality by two consecutive breakpoints
 168                         (<span class="instruction">hlt</span> instructions to be specific):
 169                         The first two instruction addresses of the W32 functions are called
 170                         <span class="productname">slot #1</span> and
 171                         <span class="productname">slot #2</span>, the length of the first
 172                         function instruction has to be analyzed to get the right address of
 173                         <span class="productname">slot #2</span>. When the first breakpoint is
 174                         caught it is necessary to patch the original instruction back and also
 175                         patch another breakpoint in place of
 176                         <span class="productname">slot #2</span>.
 177                         During the <span class="productname">slot #2</span> breakpoint
 178                         invocation the operation will be reverted &mdash; the breakpoint will be put
 179                         to <span class="productname">slot #1</span> again and the instruction
 180                         of <span class="productname">slot #2</span> will be restored to be able
 181                         to continue the execution of the function.</p>
 182
 183                         <p>W32 function will finish in its specific
 184                         @{[ a_href '#calltype','cdecl/stdcall/fastcall call type' ]}, the control
 185                         will return to the UNIX jump table relay which will debug dump the
 186                         return value and it will finally pass the control back to the UNIX
 187                         caller in the standard UNIX
 188                         @{[ a_href 'CallType.pm#calltype_cdecl','cdecl call type' ]}.</p>
 189
 190                         @{[ doc_img 'fig/functype_patched_pass_fromunix',
 191                                         'Function Type: <span class="constant">pass</span> from UNIX Code' ]}
 192
 193                 <h3 id="functype_pass_fromw32">Pass from W32 Code</h3>
 194
 195                         <p>This function type is similiar to the
 196                         @{[ a_href 'APITypes.pm#functype_pass_fromunix','previous one' ]} with the exception
 197                         of more complicated entry point. Unfortunately W32 libraries call their
 198                         own functions directly, using the <span class="instruction">call</span>
 199                         instructions without any patchable jump table. Even the
 200                         <span class="instruction">call</span> argument itself cannot be patched
 201                         according to the relocation table record as such library intra-call
 202                         instruction has no relocation due to its relative argument offset on
 203                         <span class="constant">i386</span>. This time the double-breakpoint
 204                         mechanism @{[ a_href 'APITypes.pm#functype_pass_fromunix','described above' ]} gets
 205                         handy since it will catch the entry point when the function gets
 206                         called.  <span class="constant">SIGSEGV</span> handler gets invoked by
 207                         the <span class="instruction">hlt</span> instruction and it will
 208                         redirect the control to the jump table relay function to debug dump the
 209                         function entry arguments (it has no other uses in this call type).</p>
 210
 211                         <p>When the relay needs to call the original function it will reach
 212                         exactly the same breakpoint instruction as during the recent
 213                         <span class="constant">SIGSEGV</span> handling redirecting to this
 214                         calling relay.  But this time the
 215                         <span class="constant">through_w32_func</span> field of this function
 216                         record will be set to to prevent repeated redirection and to pass the
 217                         control through the breakpoint mangle instead this time.</p>
 218
 219                         <p>Returning is not much interesting as the first
 220                         <span class="constant">SIGSEGV</span> handler did a&nbsp;straight jump
 221                         for the redirection purposes without any needed consequent
 222                         handling.</p>
 223
 224                         <p>The jump table relay used for the callers from W32 code is
 225                         a&nbsp;different one than the relay being used for the callers
 226                         @{[ a_href 'APITypes.pm#functype_pass_fromunix','from UNIX code' ]}. UNIX code always
 227                         uses relay with external @{[ a_href 'CallType.pm#calltype_cdecl','cdecl call type' ]}
 228                         but in this case a&nbsp;relay with the appropriate
 229                         @{[ a_href '#calltype','cdecl/stdcall/fastcall call type' ]} is used.</p>
 230
 231                         @{[ doc_img 'fig/functype_patched_pass_fromw32',
 232                                         'Function Type: <span class="constant">pass</span> from W32 Code' ]}
 233
 234                 @{[ vskip() ]}
 235
 236                 <table border="0" width="100%"><tr><td align="center"><table border="1">
 237                         <caption>Function Type <span class="constant">pass</span> Characteristics</caption>
 238                         <tr><td><span class="fname">captivesym</span> keyword</td><td>pass</td></tr>
 239                         <tr><td>Native code function name                    </td><td>(no implementation)</td></tr>
 240                         <tr><td>W32 traced code from UNIX function name      </td><td>FUNCNAME</td></tr>
 241                         <tr><td>W32 traced code from W32  function name      </td><td>FUNCNAME_cdecl/_stdcall/_fastcall</td></tr>
 242                         <tr><td>Entry/exit debug tracing from UNIX code      </td><td>yes</td></tr>
 243                         <tr><td>Entry/exit debug tracing from W32 code       </td><td>yes</td></tr>
 244                 </table></td></tr></table>
 245
 246         <h2 id="functype_wrap">Wrap of the Original "ntoskrnl.exe" Function</h2>
 247
 248                 <h3 id="functype_wrap_fromunix">Wrapping of Call from UNIX Code</h3>
 249
 250                         <p>The code control flow has no special hardcore features since it is
 251                         very similiar to <a href="APITypes.pm#functype_pass_fromunix">the direct pass to
 252                         W32 function from UNIX code</a>. All the wrapping is done in the
 253                         standard UNIX @{[ a_href 'CallType.pm#calltype_cdecl','cdecl call type' ]} manner.
 254                         Jump table debug dumping relays are provided twice &mdash; the
 255                         &quot;outer&quot; one to trace the parameters from the function caller
 256                         and the &quot;inner&quot; one to trace the call from the wrapper to the
 257                         original W32 code. The &quot;inner&quot; relay also calls the W32 code
 258                         with the appropriate <a href="#calltype">cdecl/stdcall/fastcall call
 259                         type</a>.</p>
 260
 261                         @{[ doc_img 'fig/functype_patched_wrap_fromunix',
 262                                         'Function Type: <span class="constant">wrap</span> from UNIX Code' ]}
 263
 264                 <h3 id="functype_wrap_fromw32">Wrapping of Call from W32 Code</h3>
 265
 266                         <p>This scheme is a&nbsp;combination of the
 267                         <a href="APITypes.pm#functype_wrap_fromunix">previous wrap of a&nbsp;call from
 268                         UNIX code</a> and the <a href="APITypes.pm#functype_pass_fromw32">direct pass from
 269                         the W32 code</a>. The control is caught and redirected by
 270                         <span class="constant">SIGSEGV</span> handler from the breakpoint
 271                         placed at the entry to the original W32 function code. The second entry
 272                         to the original W32 function with the
 273                         <span class="constant">through_w32_func</span> field of this function
 274                         description already set is done from the &quot;inner&quot; jump table
 275                         relay with the appropriate
 276                         @{[ a_href '#calltype','cdecl/stdcall/fastcall call type' ]}.</p>
 277
 278                         @{[ doc_img 'fig/functype_patched_wrap_fromw32',
 279                                         'Function Type: <span class="constant">wrap</span> from W32 Code' ]}
 280
 281                 @{[ vskip() ]}
 282
 283                 <p>Some functions can be <a href="APITypes.pm#functype_pass">passed to the original
 284                 code</a> but they need their parameters to be checked/prepared.
 285                 Currently, such wrapping is only needed for the
 286                 <span class="function">ExAllocateFromPagedLookasideList()</span> function
 287                 where it is required due to <a href="#init_ntoskrnl">missing execution of
 288                 <span class="fname">ntoskrnl.exe</span> initialization execution</a>,
 289                 which would otherwise properly initialize some internal data structures.
 290                 In this case the wrapping code detects passing of an uninitialized
 291                 parameter and will search through the whole
 292                 <span class="fname">ntoskrnl.exe</span> code body at runtime to find the
 293                 proper initialization routine containing the correct initialization
 294                 parameters.  Passed addresses of static structures must be differentiated
 295                 as each of them usually has different initialization parameters. It is
 296                 proactive to not to have fixed parameters array as these parameters may
 297                 differ across different <span class="fname">ntoskrnl.exe</span>
 298                 versions.</p>
 299
 300                 <table border="0" width="100%"><tr><td align="center"><table border="1">
 301                         <caption>Function Type <span class="constant">wrap</span> Characteristics</caption>
 302                         <tr><td><span class="fname">captivesym</span> keyword</td><td>wrap</td></tr>
 303                         <tr><td>Native UNIX wrapping code function name      </td><td>FUNCNAME_wrap</td></tr>
 304                         <tr><td>W32 traced wraping code from UNIX func. name </td><td>FUNCNAME</td></tr>
 305                         <tr><td>W32 traced wrapping code from W32 func. name </td><td>FUNCNAME_cdecl/_stdcall/...</td></tr>
 306                         <tr><td>W32 traced original code function name       </td><td>FUNCNAME_orig</td></tr>
 307                         <tr><td>Entry/exit debug tracing from UNIX code      </td><td>yes</td></tr>
 308                         <tr><td>Entry/exit debug tracing from W32 code       </td><td>yes</td></tr>
 309                 </table></td></tr></table>
 310
 311         <h2 id="functype_native">Native Implementation</h2>
 312
 313                 <h3 id="functype_native_fromunix">Native Implementation Called from UNIX Code</h3>
 314
 315                         <p>This is the simplest case of a&nbsp;function call as it is fully
 316                         handled only by the compiler and/or linker.</p>
 317
 318                         <p>In this case though, no debug dumping call relay is provided &mdash; such
 319                         relay would need to rename the implementations of native functions to
 320                         prevent its automatic linking with the caller code. This renaming would
 321                         not be possible to do by simple <span class="constant">#define</span>
 322                         since it would also rename any calling statements of such function in
 323                         the same C&nbsp;sources.  One of the possibilities to solve would be to
 324                         utilize <span class="dashdash">--redefine-sym</span> feature of the
 325                         <span class="productname">objcopy(1)</span> utility. On the other hand
 326                         there is not much need to catch/debug such calls as both the caller and
 327                         the callee are provided with full source file debug information for the
 328                         debugger. Also the callee usually debug dumps its entry/exit parameters
 329                         by custom debug dumps in the
 330                         <a href="APITypes.pm#functype_native_reactos"><span class="productname">ReactOS</span> implementations</a>.
 331                         </p>
 332
 333                         @{[ doc_img 'fig/functype_native_fromunix',
 334                                         'Function Type: <span class="constant">native</span> from UNIX Code' ]}
 335
 336                 <h3 id="functype_native_fromw32">Native Implementation of
 337                                 &quot;unpatched&quot; Library Function Called from W32 Code</h3>
 338
 339                         @{[ doc_img 'fig/functype_unpatched_native_fromw32',
 340                                         'Function Type: <span class="constant">native</span> of <span class="constant">unpatched</span> from W32 Code' ]}
 341
 342                         <p>Here comes the differentiation if the project deals either with
 343                         a&nbsp;<span class="constant">patched</span> or an
 344                         <span class="constant">unpatched</span> version of the library
 345                         (<span class="constant">patched</span> is a&nbsp;loaded W32 binary
 346                         library while <span class="constant">unpatched</span> library is
 347                         completely provided by this project with no use of the library's
 348                         original W32 binary file). As the project adjusts the exported symbol
 349                         address during the patching operation, in some cases the
 350                         <span class="constant">patched</span> library call may be handled
 351                         simply as <span class="constant">unpatched</span> library call even for
 352                         the <span class="constant">patched</span> libraries. Fortunately the
 353                         distinction is not much important as the project is prepared to
 354                         properly handle both cases.</p>
 355
 356                         <p>The W32 caller which imported the symbol will be pointed right to
 357                         the relaying function. The debug dumping relay will be called from W32
 358                         code with the appropriate
 359                         @{[ a_href '#calltype','cdecl/stdcall/fastcall call type' ]} while the
 360                         relay will call the implementation of the native function in the
 361                         standard UNIX @{[ a_href 'CallType.pm#calltype_cdecl','cdecl call type' ]} manner.</p>
 362
 363                 <h3 id="functype_native_fromw32_patched">Native Implementation of &quot;patched&quot; Library Function Called from W32 Code</h3>
 364
 365                         @{[ doc_img 'fig/functype_patched_native_fromw32',
 366                                         'Function Type: <span class="constant">native</span> of <span class="constant">patched</span> from W32 Code' ]}
 367
 368                         <p>The calling scheme is similiar to the
 369                         <a href="APITypes.pm#functype_native_fromw32">previous call of
 370                         <span class="constant">unpatched</span> library function from W32
 371                         code</a> but the call control is redirected from the entry point of the
 372                         original W32 binary implementation by the breakpoint and its
 373                         <span class="constant">SIGSEGV</span> handler as in
 374                         <a href="APITypes.pm#functype_pass_fromw32">the case of passing control from W32
 375                         call</a>.</p>
 376
 377                         <p>The original W32 function implementation located in the original
 378                         loaded binary file is never executed but its entry point needs to be
 379                         trapped by the breakpoint to be able to catch the function calls within
 380                         the library.</p>
 381
 382                 @{[ vskip() ]}
 383
 384                 <p>In all cases the final function implementation is a&nbsp;standard UNIX
 385                 code compiled from C&nbsp;sources with full debug information available
 386                 for the debugger. Fortunately all such functions do not need to be coded
 387                 from scratch for this project since there already exist $freespeech
 388                 $ReactOS and $Wine projects and their code can be used instead.</p>
 389
 390                 <p>$Wine project is listed mostly for a&nbsp;completeness as almost no
 391                 code was suitable for reuse as it implements W32 user space while this
 392                 project is running pure W32 kernel space environment (in $gnulinux user
 393                 space!).</p>
 394
 395                 <h3 id="functype_native_reactos">Native Implementation
 396                                 - <span class="productname">ReactOS</span></h3>
 397
 398                         <p>Some functions are already implemented in the $ReactOS
 399                         project and they can be used as they are.  Although it would be
 400                         possible to <a href="APITypes.pm#functype_pass">pass some function calls to the
 401                         original code</a> it is more handy to provide native implementation as
 402                         there is better control of the data handling during debugging sessions
 403                         due to the provided debugging symbols.</p>
 404
 405                         <p>Such functions can be found in
 406                         <span class="fname">src/libcaptive/reactos/</span> subdirectory.
 407                         Some functions had to be adjusted for this project
 408                         - these modifications are compiled conditionally, depending on the
 409                         <span class="constant">LIBCAPTIVE</span> symbol existence.</p>
 410
 411                         <p>Later stages of this project reached the level where
 412                         $ReactOS is yet too immature and the needed functions are usually
 413                         written just with the sad body:</p>
 414
 415                         <blockquote class="command">
 416                                 <p>UNIMPLEMENTED;</p>
 417                         </blockquote>
 418
 419                         <p>Functions that were not possible to
 420                         @{[ a_href 'APITypes.pm#functype_pass','pass' ]} were reimplemented by this project
 421                         and placed in the project's implementation directories
 422                         @{[ a_href '#reactos_nocare','instead of extending' ]} $ReactOS code.</p>
 423
 424                 <h3 id="functype_native_wine">Native Implementation &ndash; <span class="productname">Wine</span></h3>
 425
 426                         <p>Even though $Wine only implements the
 427                         <span class="productname">Microsoft Windows NT</span> user space, there
 428                         still are some common functions which could be copied from the $Wine
 429                         project.</p>
 430
 431                 <h3 id="functype_native_libcaptive">Native Implementation &ndash; Project Specific</h3>
 432
 433                         <p>As the last resort it was necessary to provide completely own
 434                         implementation of some API functions such as PC hardware dependent
 435                         parts or memory management functions.</p>
 436
 437                 @{[ vskip() ]}
 438
 439                 <table border="0" width="100%"><tr><td align="center"><table border="1">
 440                         <caption>Function Type <span class="constant">native</span> Characteristics</caption>
 441                         <tr><td><span class="fname">captivesym</span> keyword</td><td>(none; just the symbol name)</td></tr>
 442                         <tr><td>Native code function name                    </td><td>FUNCTIONNAME</td></tr>
 443                         <tr><td>Native traced code from W32 code func. name  </td><td>FUNCTIONNAME_cdecl/_std...</td></tr>
 444                         <tr><td>Entry/exit debug tracing from UNIX code      </td><td>no</td></tr>
 445                         <tr><td>Entry/exit debug tracing from W32 code       </td><td>yes</td></tr>
 446                 </table></td></tr></table>
 447
 448         <h2 id="functype_undef">Undefined Function</h2>
 449
 450                 <p>Functions not defined by any of the previous function types cannot be
 451                 called by any W32 code including the code of the library implementing
 452                 such function. All functions of <span class="constant">patch</span>ed
 453                 libraries not listed in the <span class="fname">captivesym</span> exports
 454                 file are automatically set to be trapped as fatal program execution
 455                 errors.</p>
 456
 457                 <p>It is not necessary to list the symbols as
 458                 <span class="constant">undef</span> as long as you are just loading the
 459                 W32 <span class="constant">PE-32</span> code and the symbols belong to
 460                 <span class="constant">patch</span>ed library. On the other hand if you
 461                 are loading W32 <span class="fname">.so</span> code or if such symbol is
 462                 a&nbsp;part of <span class="constant">unpatched</span> library (and thus
 463                 being completely provided by the project) you need to list such symbol as
 464                 <span class="constant">undef</span> type to prevent unresolved symbol
 465                 reference.</p>
 466
 467                 <table border="0" width="100%"><tr><td align="center"><table border="1">
 468                         <caption>Function Type <span class="constant">undef</span> Characteristics</caption>
 469                         <tr><td><span class="fname">captivesym</span> keyword</td><td>undef</td></tr>
 470                         <tr><td>Native code function name                    </td><td>(no implementation)</td></tr>
 471                         <tr><td>Native traced code function name             </td><td>FUNCTIONNAME_cdecl/_stdcall/_fastcall</td></tr>
 472                         <tr><td>Debug tracing message from UNIX code         </td><td>yes</td></tr>
 473                         <tr><td>Debug tracing message from W32 code          </td><td>yes</td></tr>
 474                 </table></td></tr></table>
 475
 476
 477 HERE
 478
 479
 480 project::captive::doc::Macros->footer();
 481 }
 482 1;