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