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v1.0.0
src/include/compiler.h
650 строк
19 KB
Joshua Oreman
[linker] Add safe weak symbol macros
21 янв 2010, 01:05
21 янв 2010, 01:05
2d58a62
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#ifndef COMPILER_H #define COMPILER_H /* * Doxygen can't cope with some of the more esoteric areas of C, so we * make its life simpler. * */ #ifdef DOXYGEN #define __attribute__(x) #endif /** @file * * Global compiler definitions. * * This file is implicitly included by every @c .c file in Etherboot. * It defines global macros such as DBG(). * * We arrange for each object to export the symbol @c obj_OBJECT * (where @c OBJECT is the object name, e.g. @c rtl8139) as a global * symbol, so that the linker can drag in selected object files from * the library using <tt> -u obj_OBJECT </tt>. * */ /* Force visibility of all symbols to "hidden", i.e. inform gcc that * all symbol references resolve strictly within our final binary. * This avoids unnecessary PLT/GOT entries on x86_64. * * This is a stronger claim than specifying "-fvisibility=hidden", * since it also affects symbols marked with "extern". */ #ifndef ASSEMBLY #if __GNUC__ >= 4 #pragma GCC visibility push(hidden) #endif #endif /* ASSEMBLY */ #undef _S1 #undef _S2 #undef _C1 #undef _C2 /** Concatenate non-expanded arguments */ #define _C1( x, y ) x ## y /** Concatenate expanded arguments */ #define _C2( x, y ) _C1 ( x, y ) /** Stringify non-expanded argument */ #define _S1( x ) #x /** Stringify expanded argument */ #define _S2( x ) _S1 ( x ) /** * @defgroup symmacros Macros to provide or require explicit symbols * @{ */ /** Provide a symbol within this object file */ #ifdef ASSEMBLY #define PROVIDE_SYMBOL( _sym ) \ .globl _sym ; \ .comm _sym, 0 #else /* ASSEMBLY */ #define PROVIDE_SYMBOL( _sym ) \ char _sym[0] #endif /* ASSEMBLY */ /** Require a symbol within this object file * * The symbol is referenced by a relocation in a discarded section, so * if it is not available at link time the link will fail. */ #ifdef ASSEMBLY #define REQUIRE_SYMBOL( _sym ) \ .section ".discard", "a", @progbits ; \ .extern _sym ; \ .long _sym ; \ .previous #else /* ASSEMBLY */ #define REQUIRE_SYMBOL( _sym ) \ extern char _sym; \ static char * _C2 ( _C2 ( __require_, _sym ), _C2 ( _, __LINE__ ) ) \ __attribute__ (( section ( ".discard" ), used )) \ = &_sym #endif /** Request that a symbol be available at runtime * * The requested symbol is entered as undefined into the symbol table * for this object, so the linker will pull in other object files as * necessary to satisfy the reference. However, the undefined symbol * is not referenced in any relocations, so the link can still succeed * if no file contains it. * * A symbol passed to this macro may not be referenced anywhere * else in the file. If you want to do that, see IMPORT_SYMBOL(). */ #ifdef ASSEMBLY #define REQUEST_SYMBOL( _sym ) \ .equ __need_ ## _sym, _sym #else /* ASSEMBLY */ #define REQUEST_SYMBOL( _sym ) \ __asm__ ( ".equ\t__need_" #_sym ", " #_sym ) #endif /* ASSEMBLY */ /** Set up a symbol to be usable in another file by IMPORT_SYMBOL() * * The symbol must already be marked as global. */ #define EXPORT_SYMBOL( _sym ) PROVIDE_SYMBOL ( __export_ ## _sym ) /** Make a symbol usable to this file if available at link time * * If no file passed to the linker contains the symbol, it will have * @c NULL value to future uses. Keep in mind that the symbol value is * really the @e address of a variable or function; see the code * snippet below. * * In C using IMPORT_SYMBOL, you must specify the declaration as the * second argument, for instance * * @code * IMPORT_SYMBOL ( my_func, int my_func ( int arg ) ); * IMPORT_SYMBOL ( my_var, int my_var ); * * void use_imports ( void ) { * if ( my_func && &my_var ) * my_var = my_func ( my_var ); * } * @endcode * * GCC considers a weak declaration to override a strong one no matter * which comes first, so it is safe to include a header file declaring * the imported symbol normally, but providing the declaration to * IMPORT_SYMBOL is still required. * * If no EXPORT_SYMBOL declaration exists for the imported symbol in * another file, the behavior will be most likely be identical to that * for an unavailable symbol. */ #ifdef ASSEMBLY #define IMPORT_SYMBOL( _sym ) \ REQUEST_SYMBOL ( __export_ ## _sym ) ; \ .weak _sym #else /* ASSEMBLY */ #define IMPORT_SYMBOL( _sym, _decl ) \ REQUEST_SYMBOL ( __export_ ## _sym ) ; \ extern _decl __attribute__ (( weak )) #endif /** @} */ /** * @defgroup objmacros Macros to provide or require explicit objects * @{ */ #define PREFIX_OBJECT( _prefix ) _C2 ( _prefix, OBJECT ) #define OBJECT_SYMBOL PREFIX_OBJECT ( obj_ ) #define REQUEST_EXPANDED( _sym ) REQUEST_SYMBOL ( _sym ) #define CONFIG_SYMBOL PREFIX_OBJECT ( obj_config_ ) /** Always provide the symbol for the current object (defined by -DOBJECT) */ PROVIDE_SYMBOL ( OBJECT_SYMBOL ); /** Pull in an object-specific configuration file if available */ REQUEST_EXPANDED ( CONFIG_SYMBOL ); /** Explicitly require another object */ #define REQUIRE_OBJECT( _obj ) REQUIRE_SYMBOL ( obj_ ## _obj ) /** Pull in another object if it exists */ #define REQUEST_OBJECT( _obj ) REQUEST_SYMBOL ( obj_ ## _obj ) /** @} */ /** Select file identifier for errno.h (if used) */ #define ERRFILE PREFIX_OBJECT ( ERRFILE_ ) /** * @defgroup weakmacros Macros to manage weak symbol definitions * * Weak symbols allow one to reference a function in another file * without necessarily requiring that file to be linked in. In their * native form, the function will be @c NULL if its file is not linked * in; these macros provide an inline wrapper that returns an * appropriate error indication or default value. * * @{ */ #ifndef ASSEMBLY /** Mangle @a name into its weakly-referenced implementation */ #define __weak_impl( name ) _w_ ## name /** * Declare a weak function with inline safety wrapper * * @v ret Return type of weak function * @v name Name of function to expose * @v proto Parenthesized list of arguments with types * @v args Parenthesized list of argument names * @v dfl Value to return if weak function is not available */ #define __weak_decl( ret, name, proto, args, dfl ) \ ret __weak_impl( name ) proto __attribute__ (( weak )); \ static inline ret name proto { \ if ( __weak_impl( name ) ) \ return __weak_impl( name ) args; \ return dfl; \ } #endif /** @} */ /** @defgroup dbg Debugging infrastructure * @{ */ #ifndef ASSEMBLY /** @def DBG * * Print a debugging message. * * The debug level is set at build time by specifying the @c DEBUG= * parameter on the @c make command line. For example, to enable * debugging for the PCI bus functions (in pci.c) in a @c .dsk image * for the @c rtl8139 card, you could use the command line * * @code * * make bin/rtl8139.dsk DEBUG=pci * * @endcode * * This will enable the debugging statements (DBG()) in pci.c. If * debugging is not enabled, DBG() statements will be ignored. * * You can enable debugging in several objects simultaneously by * separating them with commas, as in * * @code * * make bin/rtl8139.dsk DEBUG=pci,buffer,heap * * @endcode * * You can increase the debugging level for an object by specifying it * with @c :N, where @c N is the level, as in * * @code * * make bin/rtl8139.dsk DEBUG=pci,buffer:2,heap * * @endcode * * which would enable debugging for the PCI, buffer-handling and * heap-allocation code, with the buffer-handling code at level 2. * */ /* * If debug_OBJECT is set to a true value, the macro DBG(...) will * expand to printf(...) when compiling OBJECT, and the symbol * DEBUG_LEVEL will be inserted into the object file. * */ #define DEBUG_SYMBOL PREFIX_OBJECT ( debug_ ) /** printf() for debugging * * This function exists so that the DBG() macros can expand to * printf() calls without dragging the printf() prototype into scope. * * As far as the compiler is concerned, dbg_printf() and printf() are * completely unrelated calls; it's only at the assembly stage that * references to the dbg_printf symbol are collapsed into references * to the printf symbol. */ extern int __attribute__ (( format ( printf, 1, 2 ) )) dbg_printf ( const char *fmt, ... ) asm ( "printf" ); extern void dbg_autocolourise ( unsigned long id ); extern void dbg_decolourise ( void ); extern void dbg_hex_dump_da ( unsigned long dispaddr, const void *data, unsigned long len ); #if DEBUG_SYMBOL #define DBGLVL_MAX DEBUG_SYMBOL #else #define DBGLVL_MAX 0 #endif /* Allow for selective disabling of enabled debug levels */ #if DBGLVL_MAX int __debug_disable; #define DBGLVL ( DBGLVL_MAX & ~__debug_disable ) #define DBG_DISABLE( level ) do { \ __debug_disable |= ( (level) & DBGLVL_MAX ); \ } while ( 0 ) #define DBG_ENABLE( level ) do { \ __debug_disable &= ~( (level) & DBGLVL_MAX ); \ } while ( 0 ) #else #define DBGLVL 0 #define DBG_DISABLE( level ) do { } while ( 0 ) #define DBG_ENABLE( level ) do { } while ( 0 ) #endif #define DBGLVL_LOG 1 #define DBG_LOG ( DBGLVL & DBGLVL_LOG ) #define DBGLVL_EXTRA 2 #define DBG_EXTRA ( DBGLVL & DBGLVL_EXTRA ) #define DBGLVL_PROFILE 4 #define DBG_PROFILE ( DBGLVL & DBGLVL_PROFILE ) #define DBGLVL_IO 8 #define DBG_IO ( DBGLVL & DBGLVL_IO ) /** * Print debugging message if we are at a certain debug level * * @v level Debug level * @v ... printf() argument list */ #define DBG_IF( level, ... ) do { \ if ( DBG_ ## level ) { \ dbg_printf ( __VA_ARGS__ ); \ } \ } while ( 0 ) /** * Print a hex dump if we are at a certain debug level * * @v level Debug level * @v dispaddr Display address * @v data Data to print * @v len Length of data */ #define DBG_HDA_IF( level, dispaddr, data, len ) do { \ if ( DBG_ ## level ) { \ union { \ unsigned long ul; \ typeof ( dispaddr ) raw; \ } da; \ da.raw = dispaddr; \ dbg_hex_dump_da ( da.ul, data, len ); \ } \ } while ( 0 ) /** * Print a hex dump if we are at a certain debug level * * @v level Debug level * @v data Data to print * @v len Length of data */ #define DBG_HD_IF( level, data, len ) do { \ const void *_data = data; \ DBG_HDA_IF ( level, _data, _data, len ); \ } while ( 0 ) /** * Select colour for debug messages if we are at a certain debug level * * @v level Debug level * @v id Message stream ID */ #define DBG_AC_IF( level, id ) do { \ if ( DBG_ ## level ) { \ union { \ unsigned long ul; \ typeof ( id ) raw; \ } dbg_stream; \ dbg_stream.raw = id; \ dbg_autocolourise ( dbg_stream.ul ); \ } \ } while ( 0 ) /** * Revert colour for debug messages if we are at a certain debug level * * @v level Debug level */ #define DBG_DC_IF( level ) do { \ if ( DBG_ ## level ) { \ dbg_decolourise(); \ } \ } while ( 0 ) /* Autocolourising versions of the DBGxxx_IF() macros */ #define DBGC_IF( level, id, ... ) do { \ DBG_AC_IF ( level, id ); \ DBG_IF ( level, __VA_ARGS__ ); \ DBG_DC_IF ( level ); \ } while ( 0 ) #define DBGC_HDA_IF( level, id, ... ) do { \ DBG_AC_IF ( level, id ); \ DBG_HDA_IF ( level, __VA_ARGS__ ); \ DBG_DC_IF ( level ); \ } while ( 0 ) #define DBGC_HD_IF( level, id, ... ) do { \ DBG_AC_IF ( level, id ); \ DBG_HD_IF ( level, __VA_ARGS__ ); \ DBG_DC_IF ( level ); \ } while ( 0 ) /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( LOG, ... )*/ #define DBG( ... ) DBG_IF ( LOG, __VA_ARGS__ ) #define DBG_HDA( ... ) DBG_HDA_IF ( LOG, __VA_ARGS__ ) #define DBG_HD( ... ) DBG_HD_IF ( LOG, __VA_ARGS__ ) #define DBGC( ... ) DBGC_IF ( LOG, __VA_ARGS__ ) #define DBGC_HDA( ... ) DBGC_HDA_IF ( LOG, __VA_ARGS__ ) #define DBGC_HD( ... ) DBGC_HD_IF ( LOG, __VA_ARGS__ ) /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( EXTRA, ... )*/ #define DBG2( ... ) DBG_IF ( EXTRA, __VA_ARGS__ ) #define DBG2_HDA( ... ) DBG_HDA_IF ( EXTRA, __VA_ARGS__ ) #define DBG2_HD( ... ) DBG_HD_IF ( EXTRA, __VA_ARGS__ ) #define DBGC2( ... ) DBGC_IF ( EXTRA, __VA_ARGS__ ) #define DBGC2_HDA( ... ) DBGC_HDA_IF ( EXTRA, __VA_ARGS__ ) #define DBGC2_HD( ... ) DBGC_HD_IF ( EXTRA, __VA_ARGS__ ) /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( PROFILE, ... )*/ #define DBGP( ... ) DBG_IF ( PROFILE, __VA_ARGS__ ) #define DBGP_HDA( ... ) DBG_HDA_IF ( PROFILE, __VA_ARGS__ ) #define DBGP_HD( ... ) DBG_HD_IF ( PROFILE, __VA_ARGS__ ) #define DBGCP( ... ) DBGC_IF ( PROFILE, __VA_ARGS__ ) #define DBGCP_HDA( ... ) DBGC_HDA_IF ( PROFILE, __VA_ARGS__ ) #define DBGCP_HD( ... ) DBGC_HD_IF ( PROFILE, __VA_ARGS__ ) /* Versions of the DBGxxx_IF() macros that imply DBGxxx_IF( IO, ... )*/ #define DBGIO( ... ) DBG_IF ( IO, __VA_ARGS__ ) #define DBGIO_HDA( ... ) DBG_HDA_IF ( IO, __VA_ARGS__ ) #define DBGIO_HD( ... ) DBG_HD_IF ( IO, __VA_ARGS__ ) #define DBGCIO( ... ) DBGC_IF ( IO, __VA_ARGS__ ) #define DBGCIO_HDA( ... ) DBGC_HDA_IF ( IO, __VA_ARGS__ ) #define DBGCIO_HD( ... ) DBGC_HD_IF ( IO, __VA_ARGS__ ) #if DEBUG_SYMBOL == 0 #define NDEBUG #endif #endif /* ASSEMBLY */ /** @} */ /** @defgroup attrs Miscellaneous attributes * @{ */ #ifndef ASSEMBLY /** Declare a data structure as packed. */ #define PACKED __attribute__ (( packed )) /** Declare a variable or data structure as unused. */ #define __unused __attribute__ (( unused )) /** * Declare a function as pure - i.e. without side effects */ #define __pure __attribute__ (( pure )) /** * Declare a function as const - i.e. it does not access global memory * (including dereferencing pointers passed to it) at all. * Must also not call any non-const functions. */ #define __const __attribute__ (( const )) /** * Declare a function's pointer parameters as non-null - i.e. force * compiler to check pointers at compile time and enable possible * optimizations based on that fact */ #define __nonnull __attribute__ (( nonnull )) /** * Declare a pointer returned by a function as a unique memory address * as returned by malloc-type functions. */ #define __malloc __attribute__ (( malloc )) /** * Declare a function as used. * * Necessary only if the function is called only from assembler code. */ #define __used __attribute__ (( used )) /** Declare a data structure to be aligned with 16-byte alignment */ #define __aligned __attribute__ (( aligned ( 16 ) )) /** Declare a function to be always inline */ #define __always_inline __attribute__ (( always_inline )) /** * Shared data. * * To save space in the binary when multiple-driver images are * compiled, uninitialised data areas can be shared between drivers. * This will typically be used to share statically-allocated receive * and transmit buffers between drivers. * * Use as e.g. * * @code * * struct { * char rx_buf[NUM_RX_BUF][RX_BUF_SIZE]; * char tx_buf[TX_BUF_SIZE]; * } my_static_data __shared; * * @endcode * */ #define __shared __asm__ ( "_shared_bss" ) __aligned #endif /* ASSEMBLY */ /** @} */ /** * Optimisation barrier */ #ifndef ASSEMBLY #define barrier() __asm__ __volatile__ ( "" : : : "memory" ) #endif /* ASSEMBLY */ /** * @defgroup licences Licence declarations * * For reasons that are partly historical, various different files * within the gPXE codebase have differing licences. * * @{ */ /** Declare a file as being in the public domain * * This licence declaration is applicable when a file states itself to * be in the public domain. */ #define FILE_LICENCE_PUBLIC_DOMAIN \ PROVIDE_SYMBOL ( __licence_public_domain ) /** Declare a file as being under version 2 (or later) of the GNU GPL * * This licence declaration is applicable when a file states itself to * be licensed under the GNU GPL; "either version 2 of the License, or * (at your option) any later version". */ #define FILE_LICENCE_GPL2_OR_LATER \ PROVIDE_SYMBOL ( __licence_gpl2_or_later ) /** Declare a file as being under version 2 of the GNU GPL * * This licence declaration is applicable when a file states itself to * be licensed under version 2 of the GPL, and does not include the * "or, at your option, any later version" clause. */ #define FILE_LICENCE_GPL2_ONLY \ PROVIDE_SYMBOL ( __licence_gpl2_only ) /** Declare a file as being under any version of the GNU GPL * * This licence declaration is applicable when a file states itself to * be licensed under the GPL, but does not specify a version. * * According to section 9 of the GPLv2, "If the Program does not * specify a version number of this License, you may choose any * version ever published by the Free Software Foundation". */ #define FILE_LICENCE_GPL_ANY \ PROVIDE_SYMBOL ( __licence_gpl_any ) /** Declare a file as being under the three-clause BSD licence * * This licence declaration is applicable when a file states itself to * be licensed under terms allowing redistribution in source and * binary forms (with or without modification) provided that: * * redistributions of source code retain the copyright notice, * list of conditions and any attached disclaimers * * redistributions in binary form reproduce the copyright notice, * list of conditions and any attached disclaimers in the * documentation and/or other materials provided with the * distribution * * the name of the author is not used to endorse or promote * products derived from the software without specific prior * written permission * * It is not necessary for the file to explicitly state that it is * under a "BSD" licence; only that the licensing terms be * functionally equivalent to the standard three-clause BSD licence. */ #define FILE_LICENCE_BSD3 \ PROVIDE_SYMBOL ( __licence_bsd3 ) /** Declare a file as being under the two-clause BSD licence * * This licence declaration is applicable when a file states itself to * be licensed under terms allowing redistribution in source and * binary forms (with or without modification) provided that: * * redistributions of source code retain the copyright notice, * list of conditions and any attached disclaimers * * redistributions in binary form reproduce the copyright notice, * list of conditions and any attached disclaimers in the * documentation and/or other materials provided with the * distribution * * It is not necessary for the file to explicitly state that it is * under a "BSD" licence; only that the licensing terms be * functionally equivalent to the standard two-clause BSD licence. */ #define FILE_LICENCE_BSD2 \ PROVIDE_SYMBOL ( __licence_bsd2 ) /** Declare a file as being under the one-clause MIT-style licence * * This licence declaration is applicable when a file states itself to * be licensed under terms allowing redistribution for any purpose * with or without fee, provided that the copyright notice and * permission notice appear in all copies. */ #define FILE_LICENCE_MIT \ PROVIDE_SYMBOL ( __licence_mit ) /** Declare a particular licence as applying to a file */ #define FILE_LICENCE( _licence ) FILE_LICENCE_ ## _licence /** @} */ /* This file itself is under GPLv2-or-later */ FILE_LICENCE ( GPL2_OR_LATER ); #include <bits/compiler.h> #endif /* COMPILER_H */