project/captive/doc/APITypes.html.pl

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