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Diffstat (limited to 'gpxe/src/include/gpxe/tables.h')
| -rw-r--r-- | gpxe/src/include/gpxe/tables.h | 434 |
1 files changed, 0 insertions, 434 deletions
diff --git a/gpxe/src/include/gpxe/tables.h b/gpxe/src/include/gpxe/tables.h deleted file mode 100644 index 7dfced8c..00000000 --- a/gpxe/src/include/gpxe/tables.h +++ /dev/null @@ -1,434 +0,0 @@ -#ifndef _GPXE_TABLES_H -#define _GPXE_TABLES_H - -FILE_LICENCE ( GPL2_OR_LATER ); - -/** @page ifdef_harmful #ifdef considered harmful - * - * Overuse of @c #ifdef has long been a problem in Etherboot. - * Etherboot provides a rich array of features, but all these features - * take up valuable space in a ROM image. The traditional solution to - * this problem has been for each feature to have its own @c #ifdef - * option, allowing the feature to be compiled in only if desired. - * - * The problem with this is that it becomes impossible to compile, let - * alone test, all possible versions of Etherboot. Code that is not - * typically used tends to suffer from bit-rot over time. It becomes - * extremely difficult to predict which combinations of compile-time - * options will result in code that can even compile and link - * correctly. - * - * To solve this problem, we have adopted a new approach from - * Etherboot 5.5 onwards. @c #ifdef is now "considered harmful", and - * its use should be minimised. Separate features should be - * implemented in separate @c .c files, and should \b always be - * compiled (i.e. they should \b not be guarded with a @c #ifdef @c - * MY_PET_FEATURE statement). By making (almost) all code always - * compile, we avoid the problem of bit-rot in rarely-used code. - * - * The file config.h, in combination with the @c make command line, - * specifies the objects that will be included in any particular build - * of Etherboot. For example, suppose that config.h includes the line - * - * @code - * - * #define CONSOLE_SERIAL - * #define DOWNLOAD_PROTO_TFTP - * - * @endcode - * - * When a particular Etherboot image (e.g. @c bin/rtl8139.zdsk) is - * built, the options specified in config.h are used to drag in the - * relevant objects at link-time. For the above example, serial.o and - * tftp.o would be linked in. - * - * There remains one problem to solve: how do these objects get used? - * Traditionally, we had code such as - * - * @code - * - * #ifdef CONSOLE_SERIAL - * serial_init(); - * #endif - * - * @endcode - * - * in main.c, but this reintroduces @c #ifdef and so is a Bad Idea. - * We cannot simply remove the @c #ifdef and make it - * - * @code - * - * serial_init(); - * - * @endcode - * - * because then serial.o would end up always being linked in. - * - * The solution is to use @link tables.h linker tables @endlink. - * - */ - -/** @file - * - * Linker tables - * - * Read @ref ifdef_harmful first for some background on the motivation - * for using linker tables. - * - * This file provides macros for dealing with linker-generated tables - * of fixed-size symbols. We make fairly extensive use of these in - * order to avoid @c #ifdef spaghetti and/or linker symbol pollution. - * For example, instead of having code such as - * - * @code - * - * #ifdef CONSOLE_SERIAL - * serial_init(); - * #endif - * - * @endcode - * - * we make serial.c generate an entry in the initialisation function - * table, and then have a function call_init_fns() that simply calls - * all functions present in this table. If and only if serial.o gets - * linked in, then its initialisation function will be called. We - * avoid linker symbol pollution (i.e. always dragging in serial.o - * just because of a call to serial_init()) and we also avoid @c - * #ifdef spaghetti (having to conditionalise every reference to - * functions in serial.c). - * - * The linker script takes care of assembling the tables for us. All - * our table sections have names of the format @c .tbl.NAME.NN where - * @c NAME designates the data structure stored in the table (e.g. @c - * init_fns) and @c NN is a two-digit decimal number used to impose an - * ordering upon the tables if required. @c NN=00 is reserved for the - * symbol indicating "table start", and @c NN=99 is reserved for the - * symbol indicating "table end". - * - * As an example, suppose that we want to create a "frobnicator" - * feature framework, and allow for several independent modules to - * provide frobnicating services. Then we would create a frob.h - * header file containing e.g. - * - * @code - * - * struct frobnicator { - * const char *name; // Name of the frobnicator - * void ( *frob ) ( void ); // The frobnicating function itself - * }; - * - * #define FROBNICATORS __table ( struct frobnicator, "frobnicators" ) - * - * #define __frobnicator __table_entry ( FROBNICATORS, 01 ) - * - * @endcode - * - * Any module providing frobnicating services would look something - * like - * - * @code - * - * #include "frob.h" - * - * static void my_frob ( void ) { - * // Do my frobnicating - * ... - * } - * - * struct frob my_frobnicator __frobnicator = { - * .name = "my_frob", - * .frob = my_frob, - * }; - * - * @endcode - * - * The central frobnicator code (frob.c) would use the frobnicating - * modules as follows - * - * @code - * - * #include "frob.h" - * - * // Call all linked-in frobnicators - * void frob_all ( void ) { - * struct frob *frob; - * - * for_each_table ( frob, FROBNICATORS ) { - * printf ( "Calling frobnicator \"%s\"\n", frob->name ); - * frob->frob (); - * } - * } - * - * @endcode - * - * See init.h and init.c for a real-life example. - * - */ - -#ifdef DOXYGEN -#define __attribute__( x ) -#endif - -/** - * Declare a linker table - * - * @v type Data type - * @v name Table name - * @ret table Linker table - */ -#define __table( type, name ) ( type, name ) - -/** - * Get linker table data type - * - * @v table Linker table - * @ret type Data type - */ -#define __table_type( table ) __table_extract_type table -#define __table_extract_type( type, name ) type - -/** - * Get linker table name - * - * @v table Linker table - * @ret name Table name - */ -#define __table_name( table ) __table_extract_name table -#define __table_extract_name( type, name ) name - -/** - * Get linker table section name - * - * @v table Linker table - * @v idx Sub-table index - * @ret section Section name - */ -#define __table_section( table, idx ) \ - ".tbl." __table_name ( table ) "." __table_str ( idx ) -#define __table_str( x ) #x - -/** - * Get linker table alignment - * - * @v table Linker table - * @ret align Alignment - */ -#define __table_alignment( table ) __alignof__ ( __table_type ( table ) ) - -/** - * Declare a linker table entry - * - * @v table Linker table - * @v idx Sub-table index - * - * Example usage: - * - * @code - * - * #define FROBNICATORS __table ( struct frobnicator, "frobnicators" ) - * - * #define __frobnicator __table_entry ( FROBNICATORS, 01 ) - * - * struct frobnicator my_frob __frobnicator = { - * ... - * }; - * - * @endcode - */ -#define __table_entry( table, idx ) \ - __attribute__ (( __section__ ( __table_section ( table, idx ) ),\ - __aligned__ ( __table_alignment ( table ) ) )) - -/** - * Get start of linker table entries - * - * @v table Linker table - * @v idx Sub-table index - * @ret entries Start of entries - */ -#define __table_entries( table, idx ) ( { \ - static __table_type ( table ) __table_entries[0] \ - __table_entry ( table, idx ); \ - __table_entries; } ) - -/** - * Get start of linker table - * - * @v table Linker table - * @ret start Start of linker table - * - * Example usage: - * - * @code - * - * #define FROBNICATORS __table ( struct frobnicator, "frobnicators" ) - * - * struct frobnicator *frobs = table_start ( FROBNICATORS ); - * - * @endcode - */ -#define table_start( table ) __table_entries ( table, 00 ) - -/** - * Get end of linker table - * - * @v table Linker table - * @ret end End of linker table - * - * Example usage: - * - * @code - * - * #define FROBNICATORS __table ( struct frobnicator, "frobnicators" ) - * - * struct frobnicator *frobs_end = table_end ( FROBNICATORS ); - * - * @endcode - */ -#define table_end( table ) __table_entries ( table, 99 ) - -/** - * Get number of entries in linker table - * - * @v table Linker table - * @ret num_entries Number of entries in linker table - * - * Example usage: - * - * @code - * - * #define FROBNICATORS __table ( struct frobnicator, "frobnicators" ) - * - * unsigned int num_frobs = table_num_entries ( FROBNICATORS ); - * - * @endcode - * - */ -#define table_num_entries( table ) \ - ( ( unsigned int ) ( table_end ( table ) - \ - table_start ( table ) ) ) - -/** - * Iterate through all entries within a linker table - * - * @v pointer Entry pointer - * @v table Linker table - * - * Example usage: - * - * @code - * - * #define FROBNICATORS __table ( struct frobnicator, "frobnicators" ) - * - * struct frobnicator *frob; - * - * for_each_table_entry ( frob, FROBNICATORS ) { - * ... - * } - * - * @endcode - * - */ -#define for_each_table_entry( pointer, table ) \ - for ( pointer = table_start ( table ) ; \ - pointer < table_end ( table ) ; \ - pointer++ ) - -/** - * Iterate through all entries within a linker table in reverse order - * - * @v pointer Entry pointer - * @v table Linker table - * - * Example usage: - * - * @code - * - * #define FROBNICATORS __table ( struct frobnicator, "frobnicators" ) - * - * struct frobnicator *frob; - * - * for_each_table_entry_reverse ( frob, FROBNICATORS ) { - * ... - * } - * - * @endcode - * - */ -#define for_each_table_entry_reverse( pointer, table ) \ - for ( pointer = ( table_end ( table ) - 1 ) ; \ - pointer >= table_start ( table ) ; \ - pointer-- ) - -/****************************************************************************** - * - * Intel's C compiler chokes on several of the constructs used in this - * file. The workarounds are ugly, so we use them only for an icc - * build. - * - */ -#define ICC_ALIGN_HACK_FACTOR 128 -#ifdef __ICC - -/* - * icc miscompiles zero-length arrays by inserting padding to a length - * of two array elements. We therefore have to generate the - * __table_entries() symbols by hand in asm. - * - */ -#undef __table_entries -#define __table_entries( table, idx ) ( { \ - extern __table_type ( table ) \ - __table_temp_sym ( idx, __LINE__ ) [] \ - __table_entry ( table, idx ) \ - asm ( __table_entries_sym ( table, idx ) ); \ - __asm__ ( ".ifndef %c0\n\t" \ - ".section " __table_section ( table, idx ) "\n\t" \ - ".align %c1\n\t" \ - "\n%c0:\n\t" \ - ".previous\n\t" \ - ".endif\n\t" \ - : : "i" ( __table_temp_sym ( idx, __LINE__ ) ), \ - "i" ( __table_alignment ( table ) ) ); \ - __table_temp_sym ( idx, __LINE__ ); } ) -#define __table_entries_sym( table, idx ) \ - "__tbl_" __table_name ( table ) "_" #idx -#define __table_temp_sym( a, b ) \ - ___table_temp_sym( __table_, a, _, b ) -#define ___table_temp_sym( a, b, c, d ) a ## b ## c ## d - -/* - * icc ignores __attribute__ (( aligned (x) )) when it is used to - * decrease the compiler's default choice of alignment (which may be - * higher than the alignment actually required by the structure). We - * work around this by forcing the alignment to a large multiple of - * the required value (so that we are never attempting to decrease the - * default alignment) and then postprocessing the object file to - * reduce the alignment back down to the "real" value. - * - */ -#undef __table_alignment -#define __table_alignment( table ) \ - ( ICC_ALIGN_HACK_FACTOR * __alignof__ ( __table_type ( table ) ) ) - -/* - * Because of the alignment hack, we must ensure that the compiler - * never tries to place multiple objects within the same section, - * otherwise the assembler will insert padding to the (incorrect) - * alignment boundary. Do this by appending the line number to table - * section names. - * - * Note that we don't need to worry about padding between array - * elements, since the alignment is declared on the variable (i.e. the - * whole array) rather than on the type (i.e. on all individual array - * elements). - */ -#undef __table_section -#define __table_section( table, idx ) \ - ".tbl." __table_name ( table ) "." __table_str ( idx ) \ - "." __table_xstr ( __LINE__ ) -#define __table_xstr( x ) __table_str ( x ) - -#endif /* __ICC */ - -#endif /* _GPXE_TABLES_H */ |