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