src/include/compiler.h

   1 #ifndef COMPILER_H
   2 #define COMPILER_H
   3
   4 /*
   5  * Doxygen can't cope with some of the more esoteric areas of C, so we
   6  * make its life simpler.
   7  *
   8  */
   9 #ifdef DOXYGEN
  10 #define __attribute__(x)
  11 #endif
  12
  13 /** @file
  14  *
  15  * Global compiler definitions.
  16  *
  17  * This file is implicitly included by every @c .c file in Etherboot.
  18  * It defines global macros such as DBG().
  19  *
  20  * We arrange for each object to export the symbol @c obj_OBJECT
  21  * (where @c OBJECT is the object name, e.g. @c rtl8139) as a global
  22  * symbol, so that the linker can drag in selected object files from
  23  * the library using <tt> -u obj_OBJECT </tt>.
  24  *
  25  */
  26
  27 /* Force visibility of all symbols to "hidden", i.e. inform gcc that
  28  * all symbol references resolve strictly within our final binary.
  29  * This avoids unnecessary PLT/GOT entries on x86_64.
  30  *
  31  * This is a stronger claim than specifying "-fvisibility=hidden",
  32  * since it also affects symbols marked with "extern".
  33  */
  34 #ifndef ASSEMBLY
  35 #if __GNUC__ >= 4
  36 #pragma GCC visibility push(hidden)
  37 #endif
  38 #endif /* ASSEMBLY */
  39
  40 #undef _S1
  41 #undef _S2
  42 #undef _C1
  43 #undef _C2
  44
  45 /** Concatenate non-expanded arguments */
  46 #define _C1( x, y ) x ## y
  47 /** Concatenate expanded arguments */
  48 #define _C2( x, y ) _C1 ( x, y )
  49
  50 /** Stringify non-expanded argument */
  51 #define _S1( x ) #x
  52 /** Stringify expanded argument */
  53 #define _S2( x ) _S1 ( x )
  54
  55 /**
  56  * @defgroup symmacros Macros to provide or require explicit symbols
  57  * @{
  58  */
  59
  60 /** Provide a symbol within this object file */
  61 #ifdef ASSEMBLY
  62 #define PROVIDE_SYMBOL( _sym )                          \
  63         .globl  _sym ;                                  \
  64         .comm   _sym, 0
  65 #else /* ASSEMBLY */
  66 #define PROVIDE_SYMBOL( _sym )                          \
  67         char _sym[0]
  68 #endif /* ASSEMBLY */
  69
  70 /** Require a symbol within this object file
  71  *
  72  * The symbol is referenced by a relocation in a discarded section, so
  73  * if it is not available at link time the link will fail.
  74  */
  75 #ifdef ASSEMBLY
  76 #define REQUIRE_SYMBOL( _sym )                          \
  77         .section ".discard", "a", @progbits ;           \
  78         .extern _sym ;                                  \
  79         .long   _sym ;                                  \
  80         .previous
  81 #else /* ASSEMBLY */
  82 #define REQUIRE_SYMBOL( _sym )                          \
  83         extern char _sym;                               \
  84         static char * _C2 ( _C2 ( __require_, _sym ), _C2 ( _, __LINE__ ) ) \
  85                 __attribute__ (( section ( ".discard" ), used )) \
  86                 = &_sym
  87 #endif
  88
  89 /** Request that a symbol be available at runtime
  90  *
  91  * The requested symbol is entered as undefined into the symbol table
  92  * for this object, so the linker will pull in other object files as
  93  * necessary to satisfy the reference. However, the undefined symbol
  94  * is not referenced in any relocations, so the link can still succeed
  95  * if no file contains it.
  96  *
  97  * A symbol passed to this macro may not be referenced anywhere
  98  * else in the file. If you want to do that, see IMPORT_SYMBOL().
  99  */
 100 #ifdef ASSEMBLY
 101 #define REQUEST_SYMBOL( _sym )                          \
 102         .equ    __need_ ## _sym, _sym
 103 #else /* ASSEMBLY */
 104 #define REQUEST_SYMBOL( _sym )                          \
 105         __asm__ ( ".equ\t__need_" #_sym ", " #_sym )
 106 #endif /* ASSEMBLY */
 107
 108 /** Set up a symbol to be usable in another file by IMPORT_SYMBOL()
 109  *
 110  * The symbol must already be marked as global.
 111  */
 112 #define EXPORT_SYMBOL( _sym )   PROVIDE_SYMBOL ( __export_ ## _sym )
 113
 114 /** Make a symbol usable to this file if available at link time
 115  *
 116  * If no file passed to the linker contains the symbol, it will have
 117  * @c NULL value to future uses. Keep in mind that the symbol value is
 118  * really the @e address of a variable or function; see the code
 119  * snippet below.
 120  *
 121  * In C using IMPORT_SYMBOL, you must specify the declaration as the
 122  * second argument, for instance
 123  *
 124  * @code
 125  *   IMPORT_SYMBOL ( my_func, int my_func ( int arg ) );
 126  *   IMPORT_SYMBOL ( my_var, int my_var );
 127  *
 128  *   void use_imports ( void ) {
 129  *      if ( my_func && &my_var )
 130  *         my_var = my_func ( my_var );
 131  *   }
 132  * @endcode
 133  *
 134  * GCC considers a weak declaration to override a strong one no matter
 135  * which comes first, so it is safe to include a header file declaring
 136  * the imported symbol normally, but providing the declaration to
 137  * IMPORT_SYMBOL is still required.
 138  *
 139  * If no EXPORT_SYMBOL declaration exists for the imported symbol in
 140  * another file, the behavior will be most likely be identical to that
 141  * for an unavailable symbol.
 142  */
 143 #ifdef ASSEMBLY
 144 #define IMPORT_SYMBOL( _sym )                           \
 145         REQUEST_SYMBOL ( __export_ ## _sym ) ;          \
 146         .weak   _sym
 147 #else /* ASSEMBLY */
 148 #define IMPORT_SYMBOL( _sym, _decl )                    \
 149         REQUEST_SYMBOL ( __export_ ## _sym ) ;          \
 150         extern _decl __attribute__ (( weak ))
 151 #endif
 152
 153 /** @} */
 154
 155 /**
 156  * @defgroup objmacros Macros to provide or require explicit objects
 157  * @{
 158  */
 159
 160 #define PREFIX_OBJECT( _prefix ) _C2 ( _prefix, OBJECT )
 161 #define OBJECT_SYMBOL PREFIX_OBJECT ( obj_ )
 162 #define REQUEST_EXPANDED( _sym ) REQUEST_SYMBOL ( _sym )
 163 #define CONFIG_SYMBOL PREFIX_OBJECT ( obj_config_ )
 164
 165 /** Always provide the symbol for the current object (defined by -DOBJECT) */
 166 PROVIDE_SYMBOL ( OBJECT_SYMBOL );
 167
 168 /** Pull in an object-specific configuration file if available */
 169 REQUEST_EXPANDED ( CONFIG_SYMBOL );
 170
 171 /** Explicitly require another object */
 172 #define REQUIRE_OBJECT( _obj ) REQUIRE_SYMBOL ( obj_ ## _obj )
 173
 174 /** Pull in another object if it exists */
 175 #define REQUEST_OBJECT( _obj ) REQUEST_SYMBOL ( obj_ ## _obj )
 176
 177 /** @} */
 178
 179 /** Select file identifier for errno.h (if used) */
 180 #define ERRFILE PREFIX_OBJECT ( ERRFILE_ )
 181
 182 #ifndef ASSEMBLY
 183
 184 /** Declare a function as weak (use *before* the definition)
 185  *
 186  * Due to a bug in at least GCC 4.4.4 and earlier, weak symbols may be inlined
 187  * if they have hidden visibility (see above for why hidden visibility is
 188  * used).  This results in the non-weak symbol never being used, so explicitly
 189  * mark the function as noinline to prevent inlining.
 190  */
 191 #define __weak          __attribute__ (( weak, noinline ))
 192
 193 /** Prevent a function from being optimized away without inlining
 194  *
 195  * Calls to functions with void return type that contain no code in their body
 196  * may be removed by gcc's optimizer even when inlining is inhibited. Placing
 197  * this macro in the body of the function prevents that from occurring.
 198  */
 199 #define __keepme        asm("");
 200
 201 #endif
 202
 203 /** @defgroup dbg Debugging infrastructure
 204  * @{
 205  */
 206 #ifndef ASSEMBLY
 207
 208 /** @def DBG
 209  *
 210  * Print a debugging message.
 211  *
 212  * The debug level is set at build time by specifying the @c DEBUG=
 213  * parameter on the @c make command line.  For example, to enable
 214  * debugging for the PCI bus functions (in pci.c) in a @c .dsk image
 215  * for the @c rtl8139 card, you could use the command line
 216  *
 217  * @code
 218  *
 219  *   make bin/rtl8139.dsk DEBUG=pci
 220  *
 221  * @endcode
 222  *
 223  * This will enable the debugging statements (DBG()) in pci.c.  If
 224  * debugging is not enabled, DBG() statements will be ignored.
 225  *
 226  * You can enable debugging in several objects simultaneously by
 227  * separating them with commas, as in
 228  *
 229  * @code
 230  *
 231  *   make bin/rtl8139.dsk DEBUG=pci,buffer,heap
 232  *
 233  * @endcode
 234  *
 235  * You can increase the debugging level for an object by specifying it
 236  * with @c :N, where @c N is the level, as in
 237  *
 238  * @code
 239  *
 240  *   make bin/rtl8139.dsk DEBUG=pci,buffer:2,heap
 241  *
 242  * @endcode
 243  *
 244  * which would enable debugging for the PCI, buffer-handling and
 245  * heap-allocation code, with the buffer-handling code at level 2.
 246  *
 247  */
 248
 249 /*
 250  * If debug_OBJECT is set to a true value, the macro DBG(...) will
 251  * expand to printf(...) when compiling OBJECT, and the symbol
 252  * DEBUG_LEVEL will be inserted into the object file.
 253  *
 254  */
 255 #define DEBUG_SYMBOL PREFIX_OBJECT ( debug_ )
 256
 257 /** printf() for debugging
 258  *
 259  * This function exists so that the DBG() macros can expand to
 260  * printf() calls without dragging the printf() prototype into scope.
 261  *
 262  * As far as the compiler is concerned, dbg_printf() and printf() are
 263  * completely unrelated calls; it's only at the assembly stage that
 264  * references to the dbg_printf symbol are collapsed into references
 265  * to the printf symbol.
 266  */
 267 extern int __attribute__ (( format ( printf, 1, 2 ) ))
 268 dbg_printf ( const char *fmt, ... ) asm ( "printf" );
 269
 270 extern void dbg_autocolourise ( unsigned long id );
 271 extern void dbg_decolourise ( void );
 272 extern void dbg_hex_dump_da ( unsigned long dispaddr,
 273                               const void *data, unsigned long len );
 274
 275 #if DEBUG_SYMBOL
 276 #define DBGLVL_MAX DEBUG_SYMBOL
 277 #else
 278 #define DBGLVL_MAX 0
 279 #endif
 280
 281 /* Allow for selective disabling of enabled debug levels */
 282 #if DBGLVL_MAX
 283 int __debug_disable;
 284 #define DBGLVL ( DBGLVL_MAX & ~__debug_disable )
 285 #define DBG_DISABLE( level ) do {                               \
 286         __debug_disable |= ( (level) & DBGLVL_MAX );            \
 287         } while ( 0 )
 288 #define DBG_ENABLE( level ) do {                                \
 289         __debug_disable &= ~( (level) & DBGLVL_MAX );           \
 290         } while ( 0 )
 291 #else
 292 #define DBGLVL 0
 293 #define DBG_DISABLE( level ) do { } while ( 0 )
 294 #define DBG_ENABLE( level ) do { } while ( 0 )
 295 #endif
 296
 297 #define DBGLVL_LOG      1
 298 #define DBG_LOG         ( DBGLVL & DBGLVL_LOG )
 299 #define DBGLVL_EXTRA    2
 300 #define DBG_EXTRA       ( DBGLVL & DBGLVL_EXTRA )
 301 #define DBGLVL_PROFILE  4
 302 #define DBG_PROFILE     ( DBGLVL & DBGLVL_PROFILE )
 303 #define DBGLVL_IO       8
 304 #define DBG_IO          ( DBGLVL & DBGLVL_IO )
 305
 306 /**
 307  * Print debugging message if we are at a certain debug level
 308  *
 309  * @v level             Debug level
 310  * @v ...               printf() argument list
 311  */
 312 #define DBG_IF( level, ... ) do {                               \
 313                 if ( DBG_ ## level ) {                          \
 314                         dbg_printf ( __VA_ARGS__ );             \
 315                 }                                               \
 316         } while ( 0 )
 317
 318 /**
 319  * Print a hex dump if we are at a certain debug level
 320  *
 321  * @v level             Debug level
 322  * @v dispaddr          Display address
 323  * @v data              Data to print
 324  * @v len               Length of data
 325  */
 326 #define DBG_HDA_IF( level, dispaddr, data, len )  do {          \
 327                 if ( DBG_ ## level ) {                          \
 328                         union {                                 \
 329                                 unsigned long ul;               \
 330                                 typeof ( dispaddr ) raw;        \
 331                         } da;                                   \
 332                         da.raw = dispaddr;                      \
 333                         dbg_hex_dump_da ( da.ul, data, len );   \
 334                 }                                               \
 335         } while ( 0 )
 336
 337 /**
 338  * Print a hex dump if we are at a certain debug level
 339  *
 340  * @v level             Debug level
 341  * @v data              Data to print
 342  * @v len               Length of data
 343  */
 344 #define DBG_HD_IF( level, data, len ) do {                      \
 345                 const void *_data = data;                       \
 346                 DBG_HDA_IF ( level, _data, _data, len );        \
 347         } while ( 0 )
 348
 349 /**
 350  * Select colour for debug messages if we are at a certain debug level
 351  *
 352  * @v level             Debug level
 353  * @v id                Message stream ID
 354  */
 355 #define DBG_AC_IF( level, id ) do {                             \
 356                 if ( DBG_ ## level ) {                          \
 357                         union {                                 \
 358                                 unsigned long ul;               \
 359                                 typeof ( id ) raw;              \
 360                         } dbg_stream;                           \
 361                         dbg_stream.raw = id;                    \
 362                         dbg_autocolourise ( dbg_stream.ul );    \
 363                 }                                               \
 364         } while ( 0 )
 365
 366 /**
 367  * Revert colour for debug messages if we are at a certain debug level
 368  *
 369  * @v level             Debug level
 370  */
 371 #define DBG_DC_IF( level ) do {                                 \
 372                 if ( DBG_ ## level ) {                          \
 373                         dbg_decolourise();                      \
 374                 }                                               \
 375         } while ( 0 )
 376
 377 /* Autocolourising versions of the DBGxxx_IF() macros */
 378
 379 #define DBGC_IF( level, id, ... ) do {                          \
 380                 DBG_AC_IF ( level, id );                        \
 381                 DBG_IF ( level, __VA_ARGS__ );                  \
 382                 DBG_DC_IF ( level );                            \
 383         } while ( 0 )
 384
 385 #define DBGC_HDA_IF( level, id, ... ) do {                      \
 386                 DBG_AC_IF ( level, id );                        \
 387                 DBG_HDA_IF ( level, __VA_ARGS__ );              \
 388                 DBG_DC_IF ( level );                            \
 389         } while ( 0 )
 390
 391 #define DBGC_HD_IF( level, id, ... ) do {                       \
 392                 DBG_AC_IF ( level, id );                        \
 393                 DBG_HD_IF ( level, __VA_ARGS__ );               \
 394                 DBG_DC_IF ( level );                            \
 395         } while ( 0 )
 396
 397 /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( LOG, ... )*/
 398
 399 #define DBG( ... )              DBG_IF          ( LOG, __VA_ARGS__ )
 400 #define DBG_HDA( ... )          DBG_HDA_IF      ( LOG, __VA_ARGS__ )
 401 #define DBG_HD( ... )           DBG_HD_IF       ( LOG, __VA_ARGS__ )
 402 #define DBGC( ... )             DBGC_IF         ( LOG, __VA_ARGS__ )
 403 #define DBGC_HDA( ... )         DBGC_HDA_IF     ( LOG, __VA_ARGS__ )
 404 #define DBGC_HD( ... )          DBGC_HD_IF      ( LOG, __VA_ARGS__ )
 405
 406 /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( EXTRA, ... )*/
 407
 408 #define DBG2( ... )             DBG_IF          ( EXTRA, __VA_ARGS__ )
 409 #define DBG2_HDA( ... )         DBG_HDA_IF      ( EXTRA, __VA_ARGS__ )
 410 #define DBG2_HD( ... )          DBG_HD_IF       ( EXTRA, __VA_ARGS__ )
 411 #define DBGC2( ... )            DBGC_IF         ( EXTRA, __VA_ARGS__ )
 412 #define DBGC2_HDA( ... )        DBGC_HDA_IF     ( EXTRA, __VA_ARGS__ )
 413 #define DBGC2_HD( ... )         DBGC_HD_IF      ( EXTRA, __VA_ARGS__ )
 414
 415 /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( PROFILE, ... )*/
 416
 417 #define DBGP( ... )             DBG_IF          ( PROFILE, __VA_ARGS__ )
 418 #define DBGP_HDA( ... )         DBG_HDA_IF      ( PROFILE, __VA_ARGS__ )
 419 #define DBGP_HD( ... )          DBG_HD_IF       ( PROFILE, __VA_ARGS__ )
 420 #define DBGCP( ... )            DBGC_IF         ( PROFILE, __VA_ARGS__ )
 421 #define DBGCP_HDA( ... )        DBGC_HDA_IF     ( PROFILE, __VA_ARGS__ )
 422 #define DBGCP_HD( ... )         DBGC_HD_IF      ( PROFILE, __VA_ARGS__ )
 423
 424 /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( IO, ... )*/
 425
 426 #define DBGIO( ... )            DBG_IF          ( IO, __VA_ARGS__ )
 427 #define DBGIO_HDA( ... )        DBG_HDA_IF      ( IO, __VA_ARGS__ )
 428 #define DBGIO_HD( ... )         DBG_HD_IF       ( IO, __VA_ARGS__ )
 429 #define DBGCIO( ... )           DBGC_IF         ( IO, __VA_ARGS__ )
 430 #define DBGCIO_HDA( ... )       DBGC_HDA_IF     ( IO, __VA_ARGS__ )
 431 #define DBGCIO_HD( ... )        DBGC_HD_IF      ( IO, __VA_ARGS__ )
 432
 433
 434 #if DEBUG_SYMBOL == 0
 435 #define NDEBUG
 436 #endif
 437
 438 #endif /* ASSEMBLY */
 439 /** @} */
 440
 441 /** @defgroup attrs Miscellaneous attributes
 442  * @{
 443  */
 444 #ifndef ASSEMBLY
 445
 446 /** Declare a variable or data structure as unused. */
 447 #define __unused __attribute__ (( unused ))
 448
 449 /**
 450  * Declare a function as pure - i.e. without side effects
 451  */
 452 #define __pure __attribute__ (( pure ))
 453
 454 /**
 455  * Declare a function as const - i.e. it does not access global memory
 456  * (including dereferencing pointers passed to it) at all.
 457  * Must also not call any non-const functions.
 458  */
 459 #define __const __attribute__ (( const ))
 460
 461 /**
 462  * Declare a function's pointer parameters as non-null - i.e. force
 463  * compiler to check pointers at compile time and enable possible
 464  * optimizations based on that fact
 465  */
 466 #define __nonnull __attribute__ (( nonnull ))
 467
 468 /**
 469  * Declare a pointer returned by a function as a unique memory address
 470  * as returned by malloc-type functions.
 471  */
 472 #define __malloc __attribute__ (( malloc ))
 473
 474 /**
 475  * Declare a function as used.
 476  *
 477  * Necessary only if the function is called only from assembler code.
 478  */
 479 #define __used __attribute__ (( used ))
 480
 481 /** Declare a data structure to be aligned with 16-byte alignment */
 482 #define __aligned __attribute__ (( aligned ( 16 ) ))
 483
 484 /** Declare a function to be always inline */
 485 #define __always_inline __attribute__ (( always_inline ))
 486
 487 /**
 488  * Shared data.
 489  *
 490  * To save space in the binary when multiple-driver images are
 491  * compiled, uninitialised data areas can be shared between drivers.
 492  * This will typically be used to share statically-allocated receive
 493  * and transmit buffers between drivers.
 494  *
 495  * Use as e.g.
 496  *
 497  * @code
 498  *
 499  *   struct {
 500  *      char    rx_buf[NUM_RX_BUF][RX_BUF_SIZE];
 501  *      char    tx_buf[TX_BUF_SIZE];
 502  *   } my_static_data __shared;
 503  *
 504  * @endcode
 505  *
 506  */
 507 #define __shared __asm__ ( "_shared_bss" ) __aligned
 508
 509 #endif /* ASSEMBLY */
 510 /** @} */
 511
 512 /**
 513  * Optimisation barrier
 514  */
 515 #ifndef ASSEMBLY
 516 #define barrier() __asm__ __volatile__ ( "" : : : "memory" )
 517 #endif /* ASSEMBLY */
 518
 519 /**
 520  * @defgroup licences Licence declarations
 521  *
 522  * For reasons that are partly historical, various different files
 523  * within the gPXE codebase have differing licences.
 524  *
 525  * @{
 526  */
 527
 528 /** Declare a file as being in the public domain
 529  *
 530  * This licence declaration is applicable when a file states itself to
 531  * be in the public domain.
 532  */
 533 #define FILE_LICENCE_PUBLIC_DOMAIN \
 534         PROVIDE_SYMBOL ( __licence_public_domain )
 535
 536 /** Declare a file as being under version 2 (or later) of the GNU GPL
 537  *
 538  * This licence declaration is applicable when a file states itself to
 539  * be licensed under the GNU GPL; "either version 2 of the License, or
 540  * (at your option) any later version".
 541  */
 542 #define FILE_LICENCE_GPL2_OR_LATER \
 543         PROVIDE_SYMBOL ( __licence_gpl2_or_later )
 544
 545 /** Declare a file as being under version 2 of the GNU GPL
 546  *
 547  * This licence declaration is applicable when a file states itself to
 548  * be licensed under version 2 of the GPL, and does not include the
 549  * "or, at your option, any later version" clause.
 550  */
 551 #define FILE_LICENCE_GPL2_ONLY \
 552         PROVIDE_SYMBOL ( __licence_gpl2_only )
 553
 554 /** Declare a file as being under any version of the GNU GPL
 555  *
 556  * This licence declaration is applicable when a file states itself to
 557  * be licensed under the GPL, but does not specify a version.
 558  *
 559  * According to section 9 of the GPLv2, "If the Program does not
 560  * specify a version number of this License, you may choose any
 561  * version ever published by the Free Software Foundation".
 562  */
 563 #define FILE_LICENCE_GPL_ANY \
 564         PROVIDE_SYMBOL ( __licence_gpl_any )
 565
 566 /** Declare a file as being under the three-clause BSD licence
 567  *
 568  * This licence declaration is applicable when a file states itself to
 569  * be licensed under terms allowing redistribution in source and
 570  * binary forms (with or without modification) provided that:
 571  *
 572  *     redistributions of source code retain the copyright notice,
 573  *     list of conditions and any attached disclaimers
 574  *
 575  *     redistributions in binary form reproduce the copyright notice,
 576  *     list of conditions and any attached disclaimers in the
 577  *     documentation and/or other materials provided with the
 578  *     distribution
 579  *
 580  *     the name of the author is not used to endorse or promote
 581  *     products derived from the software without specific prior
 582  *     written permission
 583  *
 584  * It is not necessary for the file to explicitly state that it is
 585  * under a "BSD" licence; only that the licensing terms be
 586  * functionally equivalent to the standard three-clause BSD licence.
 587  */
 588 #define FILE_LICENCE_BSD3 \
 589         PROVIDE_SYMBOL ( __licence_bsd3 )
 590
 591 /** Declare a file as being under the two-clause BSD licence
 592  *
 593  * This licence declaration is applicable when a file states itself to
 594  * be licensed under terms allowing redistribution in source and
 595  * binary forms (with or without modification) provided that:
 596  *
 597  *     redistributions of source code retain the copyright notice,
 598  *     list of conditions and any attached disclaimers
 599  *
 600  *     redistributions in binary form reproduce the copyright notice,
 601  *     list of conditions and any attached disclaimers in the
 602  *     documentation and/or other materials provided with the
 603  *     distribution
 604  *
 605  * It is not necessary for the file to explicitly state that it is
 606  * under a "BSD" licence; only that the licensing terms be
 607  * functionally equivalent to the standard two-clause BSD licence.
 608  */
 609 #define FILE_LICENCE_BSD2 \
 610         PROVIDE_SYMBOL ( __licence_bsd2 )
 611
 612 /** Declare a file as being under the one-clause MIT-style licence
 613  *
 614  * This licence declaration is applicable when a file states itself to
 615  * be licensed under terms allowing redistribution for any purpose
 616  * with or without fee, provided that the copyright notice and
 617  * permission notice appear in all copies.
 618  */
 619 #define FILE_LICENCE_MIT \
 620         PROVIDE_SYMBOL ( __licence_mit )
 621
 622 /** Declare a particular licence as applying to a file */
 623 #define FILE_LICENCE( _licence ) FILE_LICENCE_ ## _licence
 624
 625 /** @} */
 626
 627 /* This file itself is under GPLv2-or-later */
 628 FILE_LICENCE ( GPL2_OR_LATER );
 629
 630 #include <bits/compiler.h>
 631
 632 #endif /* COMPILER_H */