1 /* 2 * include/linker_lists.h 3 * 4 * Implementation of linker-generated arrays 5 * 6 * Copyright (C) 2012 Marek Vasut <marex@denx.de> 7 * 8 * SPDX-License-Identifier: GPL-2.0+ 9 */ 10 11 #ifndef __LINKER_LISTS_H__ 12 #define __LINKER_LISTS_H__ 13 14 #include <linux/compiler.h> 15 16 /* 17 * There is no use in including this from ASM files, but that happens 18 * anyway, e.g. PPC kgdb.S includes command.h which incluse us. 19 * So just don't define anything when included from ASM. 20 */ 21 22 #if !defined(__ASSEMBLY__) 23 24 /** 25 * A linker list is constructed by grouping together linker input 26 * sections, each containing one entry of the list. Each input section 27 * contains a constant initialized variable which holds the entry's 28 * content. Linker list input sections are constructed from the list 29 * and entry names, plus a prefix which allows grouping all lists 30 * together. Assuming _list and _entry are the list and entry names, 31 * then the corresponding input section name is 32 * 33 * .u_boot_list_ + 2_ + @_list + _2_ + @_entry 34 * 35 * and the C variable name is 36 * 37 * _u_boot_list + _2_ + @_list + _2_ + @_entry 38 * 39 * This ensures uniqueness for both input section and C variable name. 40 * 41 * Note that the names differ only in the first character, "." for the 42 * section and "_" for the variable, so that the linker cannot confuse 43 * section and symbol names. From now on, both names will be referred 44 * to as 45 * 46 * %u_boot_list_ + 2_ + @_list + _2_ + @_entry 47 * 48 * Entry variables need never be referred to directly. 49 * 50 * The naming scheme for input sections allows grouping all linker lists 51 * into a single linker output section and grouping all entries for a 52 * single list. 53 * 54 * Note the two '_2_' constant components in the names: their presence 55 * allows putting a start and end symbols around a list, by mapping 56 * these symbols to sections names with components "1" (before) and 57 * "3" (after) instead of "2" (within). 58 * Start and end symbols for a list can generally be defined as 59 * 60 * %u_boot_list_2_ + @_list + _1_... 61 * %u_boot_list_2_ + @_list + _3_... 62 * 63 * Start and end symbols for the whole of the linker lists area can be 64 * defined as 65 * 66 * %u_boot_list_1_... 67 * %u_boot_list_3_... 68 * 69 * Here is an example of the sorted sections which result from a list 70 * "array" made up of three entries : "first", "second" and "third", 71 * iterated at least once. 72 * 73 * .u_boot_list_2_array_1 74 * .u_boot_list_2_array_2_first 75 * .u_boot_list_2_array_2_second 76 * .u_boot_list_2_array_2_third 77 * .u_boot_list_2_array_3 78 * 79 * If lists must be divided into sublists (e.g. for iterating only on 80 * part of a list), one can simply give the list a name of the form 81 * 'outer_2_inner', where 'outer' is the global list name and 'inner' 82 * is the sub-list name. Iterators for the whole list should use the 83 * global list name ("outer"); iterators for only a sub-list should use 84 * the full sub-list name ("outer_2_inner"). 85 * 86 * Here is an example of the sections generated from a global list 87 * named "drivers", two sub-lists named "i2c" and "pci", and iterators 88 * defined for the whole list and each sub-list: 89 * 90 * %u_boot_list_2_drivers_1 91 * %u_boot_list_2_drivers_2_i2c_1 92 * %u_boot_list_2_drivers_2_i2c_2_first 93 * %u_boot_list_2_drivers_2_i2c_2_first 94 * %u_boot_list_2_drivers_2_i2c_2_second 95 * %u_boot_list_2_drivers_2_i2c_2_third 96 * %u_boot_list_2_drivers_2_i2c_3 97 * %u_boot_list_2_drivers_2_pci_1 98 * %u_boot_list_2_drivers_2_pci_2_first 99 * %u_boot_list_2_drivers_2_pci_2_second 100 * %u_boot_list_2_drivers_2_pci_2_third 101 * %u_boot_list_2_drivers_2_pci_3 102 * %u_boot_list_2_drivers_3 103 */ 104 105 /** 106 * llsym() - Access a linker-generated array entry 107 * @_type: Data type of the entry 108 * @_name: Name of the entry 109 * @_list: name of the list. Should contain only characters allowed 110 * in a C variable name! 111 */ 112 #define llsym(_type, _name, _list) \ 113 ((_type *)&_u_boot_list_2_##_list##_2_##_name) 114 115 /** 116 * ll_entry_declare() - Declare linker-generated array entry 117 * @_type: Data type of the entry 118 * @_name: Name of the entry 119 * @_list: name of the list. Should contain only characters allowed 120 * in a C variable name! 121 * 122 * This macro declares a variable that is placed into a linker-generated 123 * array. This is a basic building block for more advanced use of linker- 124 * generated arrays. The user is expected to build their own macro wrapper 125 * around this one. 126 * 127 * A variable declared using this macro must be compile-time initialized. 128 * 129 * Special precaution must be made when using this macro: 130 * 131 * 1) The _type must not contain the "static" keyword, otherwise the 132 * entry is generated and can be iterated but is listed in the map 133 * file and cannot be retrieved by name. 134 * 135 * 2) In case a section is declared that contains some array elements AND 136 * a subsection of this section is declared and contains some elements, 137 * it is imperative that the elements are of the same type. 138 * 139 * 4) In case an outer section is declared that contains some array elements 140 * AND an inner subsection of this section is declared and contains some 141 * elements, then when traversing the outer section, even the elements of 142 * the inner sections are present in the array. 143 * 144 * Example: 145 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 146 * .x = 3, 147 * .y = 4, 148 * }; 149 */ 150 #define ll_entry_declare(_type, _name, _list) \ 151 _type _u_boot_list_2_##_list##_2_##_name __aligned(4) \ 152 __attribute__((unused, \ 153 section(".u_boot_list_2_"#_list"_2_"#_name))) 154 155 /** 156 * ll_entry_declare_list() - Declare a list of link-generated array entries 157 * @_type: Data type of each entry 158 * @_name: Name of the entry 159 * @_list: name of the list. Should contain only characters allowed 160 * in a C variable name! 161 * 162 * This is like ll_entry_declare() but creates multiple entries. It should 163 * be assigned to an array. 164 * 165 * ll_entry_declare_list(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 166 * { .x = 3, .y = 4 }, 167 * { .x = 8, .y = 2 }, 168 * { .x = 1, .y = 7 } 169 * }; 170 */ 171 #define ll_entry_declare_list(_type, _name, _list) \ 172 _type _u_boot_list_2_##_list##_2_##_name[] __aligned(4) \ 173 __attribute__((unused, \ 174 section(".u_boot_list_2_"#_list"_2_"#_name))) 175 176 /** 177 * We need a 0-byte-size type for iterator symbols, and the compiler 178 * does not allow defining objects of C type 'void'. Using an empty 179 * struct is allowed by the compiler, but causes gcc versions 4.4 and 180 * below to complain about aliasing. Therefore we use the next best 181 * thing: zero-sized arrays, which are both 0-byte-size and exempt from 182 * aliasing warnings. 183 */ 184 185 /** 186 * ll_entry_start() - Point to first entry of linker-generated array 187 * @_type: Data type of the entry 188 * @_list: Name of the list in which this entry is placed 189 * 190 * This function returns (_type *) pointer to the very first entry of a 191 * linker-generated array placed into subsection of .u_boot_list section 192 * specified by _list argument. 193 * 194 * Since this macro defines an array start symbol, its leftmost index 195 * must be 2 and its rightmost index must be 1. 196 * 197 * Example: 198 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 199 */ 200 #define ll_entry_start(_type, _list) \ 201 ({ \ 202 static char start[0] __aligned(4) __attribute__((unused, \ 203 section(".u_boot_list_2_"#_list"_1"))); \ 204 (_type *)&start; \ 205 }) 206 207 /** 208 * ll_entry_end() - Point after last entry of linker-generated array 209 * @_type: Data type of the entry 210 * @_list: Name of the list in which this entry is placed 211 * (with underscores instead of dots) 212 * 213 * This function returns (_type *) pointer after the very last entry of 214 * a linker-generated array placed into subsection of .u_boot_list 215 * section specified by _list argument. 216 * 217 * Since this macro defines an array end symbol, its leftmost index 218 * must be 2 and its rightmost index must be 3. 219 * 220 * Example: 221 * struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub); 222 */ 223 #define ll_entry_end(_type, _list) \ 224 ({ \ 225 static char end[0] __aligned(4) __attribute__((unused, \ 226 section(".u_boot_list_2_"#_list"_3"))); \ 227 (_type *)&end; \ 228 }) 229 /** 230 * ll_entry_count() - Return the number of elements in linker-generated array 231 * @_type: Data type of the entry 232 * @_list: Name of the list of which the number of elements is computed 233 * 234 * This function returns the number of elements of a linker-generated array 235 * placed into subsection of .u_boot_list section specified by _list 236 * argument. The result is of an unsigned int type. 237 * 238 * Example: 239 * int i; 240 * const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub); 241 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 242 * for (i = 0; i < count; i++, msc++) 243 * printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y); 244 */ 245 #define ll_entry_count(_type, _list) \ 246 ({ \ 247 _type *start = ll_entry_start(_type, _list); \ 248 _type *end = ll_entry_end(_type, _list); \ 249 unsigned int _ll_result = end - start; \ 250 _ll_result; \ 251 }) 252 253 /** 254 * ll_entry_get() - Retrieve entry from linker-generated array by name 255 * @_type: Data type of the entry 256 * @_name: Name of the entry 257 * @_list: Name of the list in which this entry is placed 258 * 259 * This function returns a pointer to a particular entry in linker-generated 260 * array identified by the subsection of u_boot_list where the entry resides 261 * and it's name. 262 * 263 * Example: 264 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 265 * .x = 3, 266 * .y = 4, 267 * }; 268 * ... 269 * struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub); 270 */ 271 #define ll_entry_get(_type, _name, _list) \ 272 ({ \ 273 extern _type _u_boot_list_2_##_list##_2_##_name; \ 274 _type *_ll_result = \ 275 &_u_boot_list_2_##_list##_2_##_name; \ 276 _ll_result; \ 277 }) 278 279 /** 280 * ll_start() - Point to first entry of first linker-generated array 281 * @_type: Data type of the entry 282 * 283 * This function returns (_type *) pointer to the very first entry of 284 * the very first linker-generated array. 285 * 286 * Since this macro defines the start of the linker-generated arrays, 287 * its leftmost index must be 1. 288 * 289 * Example: 290 * struct my_sub_cmd *msc = ll_start(struct my_sub_cmd); 291 */ 292 #define ll_start(_type) \ 293 ({ \ 294 static char start[0] __aligned(4) __attribute__((unused, \ 295 section(".u_boot_list_1"))); \ 296 (_type *)&start; \ 297 }) 298 299 /** 300 * ll_end() - Point after last entry of last linker-generated array 301 * @_type: Data type of the entry 302 * 303 * This function returns (_type *) pointer after the very last entry of 304 * the very last linker-generated array. 305 * 306 * Since this macro defines the end of the linker-generated arrays, 307 * its leftmost index must be 3. 308 * 309 * Example: 310 * struct my_sub_cmd *msc = ll_end(struct my_sub_cmd); 311 */ 312 #define ll_end(_type) \ 313 ({ \ 314 static char end[0] __aligned(4) __attribute__((unused, \ 315 section(".u_boot_list_3"))); \ 316 (_type *)&end; \ 317 }) 318 319 #endif /* __ASSEMBLY__ */ 320 321 #endif /* __LINKER_LISTS_H__ */ 322