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 * ll_entry_declare() - Declare 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 * This macro declares a variable that is placed into a linker-generated 113 * array. This is a basic building block for more advanced use of linker- 114 * generated arrays. The user is expected to build their own macro wrapper 115 * around this one. 116 * 117 * A variable declared using this macro must be compile-time initialized. 118 * 119 * Special precaution must be made when using this macro: 120 * 121 * 1) The _type must not contain the "static" keyword, otherwise the 122 * entry is generated and can be iterated but is listed in the map 123 * file and cannot be retrieved by name. 124 * 125 * 2) In case a section is declared that contains some array elements AND 126 * a subsection of this section is declared and contains some elements, 127 * it is imperative that the elements are of the same type. 128 * 129 * 4) In case an outer section is declared that contains some array elements 130 * AND an inner subsection of this section is declared and contains some 131 * elements, then when traversing the outer section, even the elements of 132 * the inner sections are present in the array. 133 * 134 * Example: 135 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub, cmd.sub) = { 136 * .x = 3, 137 * .y = 4, 138 * }; 139 */ 140 #define ll_entry_declare(_type, _name, _list) \ 141 _type _u_boot_list_2_##_list##_2_##_name __aligned(4) \ 142 __attribute__((unused, \ 143 section(".u_boot_list_2_"#_list"_2_"#_name))) 144 145 /** 146 * ll_entry_declare_list() - Declare a list of link-generated array entries 147 * @_type: Data type of each entry 148 * @_name: Name of the entry 149 * @_list: name of the list. Should contain only characters allowed 150 * in a C variable name! 151 * 152 * This is like ll_entry_declare() but creates multiple entries. It should 153 * be assigned to an array. 154 * 155 * ll_entry_declare_list(struct my_sub_cmd, my_sub_cmd, cmd_sub, cmd.sub) = { 156 * { .x = 3, .y = 4 }, 157 * { .x = 8, .y = 2 }, 158 * { .x = 1, .y = 7 } 159 * }; 160 */ 161 #define ll_entry_declare_list(_type, _name, _list) \ 162 _type _u_boot_list_2_##_list##_2_##_name[] __aligned(4) \ 163 __attribute__((unused, \ 164 section(".u_boot_list_2_"#_list"_2_"#_name))) 165 166 /** 167 * We need a 0-byte-size type for iterator symbols, and the compiler 168 * does not allow defining objects of C type 'void'. Using an empty 169 * struct is allowed by the compiler, but causes gcc versions 4.4 and 170 * below to complain about aliasing. Therefore we use the next best 171 * thing: zero-sized arrays, which are both 0-byte-size and exempt from 172 * aliasing warnings. 173 */ 174 175 /** 176 * ll_entry_start() - Point to first entry of linker-generated array 177 * @_type: Data type of the entry 178 * @_list: Name of the list in which this entry is placed 179 * 180 * This function returns (_type *) pointer to the very first entry of a 181 * linker-generated array placed into subsection of .u_boot_list section 182 * specified by _list argument. 183 * 184 * Since this macro defines an array start symbol, its leftmost index 185 * must be 2 and its rightmost index must be 1. 186 * 187 * Example: 188 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 189 */ 190 #define ll_entry_start(_type, _list) \ 191 ({ \ 192 static char start[0] __aligned(4) __attribute__((unused, \ 193 section(".u_boot_list_2_"#_list"_1"))); \ 194 (_type *)&start; \ 195 }) 196 197 /** 198 * ll_entry_end() - Point after last entry of linker-generated array 199 * @_type: Data type of the entry 200 * @_list: Name of the list in which this entry is placed 201 * (with underscores instead of dots) 202 * 203 * This function returns (_type *) pointer after the very last entry of 204 * a linker-generated array placed into subsection of .u_boot_list 205 * section specified by _list argument. 206 * 207 * Since this macro defines an array end symbol, its leftmost index 208 * must be 2 and its rightmost index must be 3. 209 * 210 * Example: 211 * struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub); 212 */ 213 #define ll_entry_end(_type, _list) \ 214 ({ \ 215 static char end[0] __aligned(4) __attribute__((unused, \ 216 section(".u_boot_list_2_"#_list"_3"))); \ 217 (_type *)&end; \ 218 }) 219 /** 220 * ll_entry_count() - Return the number of elements in linker-generated array 221 * @_type: Data type of the entry 222 * @_list: Name of the list of which the number of elements is computed 223 * 224 * This function returns the number of elements of a linker-generated array 225 * placed into subsection of .u_boot_list section specified by _list 226 * argument. The result is of an unsigned int type. 227 * 228 * Example: 229 * int i; 230 * const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub); 231 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 232 * for (i = 0; i < count; i++, msc++) 233 * printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y); 234 */ 235 #define ll_entry_count(_type, _list) \ 236 ({ \ 237 _type *start = ll_entry_start(_type, _list); \ 238 _type *end = ll_entry_end(_type, _list); \ 239 unsigned int _ll_result = end - start; \ 240 _ll_result; \ 241 }) 242 243 /** 244 * ll_entry_get() - Retrieve entry from linker-generated array by name 245 * @_type: Data type of the entry 246 * @_name: Name of the entry 247 * @_list: Name of the list in which this entry is placed 248 * 249 * This function returns a pointer to a particular entry in LG-array 250 * identified by the subsection of u_boot_list where the entry resides 251 * and it's name. 252 * 253 * Example: 254 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 255 * .x = 3, 256 * .y = 4, 257 * }; 258 * ... 259 * struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub); 260 */ 261 #define ll_entry_get(_type, _name, _list) \ 262 ({ \ 263 extern _type _u_boot_list_2_##_list##_2_##_name; \ 264 _type *_ll_result = \ 265 &_u_boot_list_2_##_list##_2_##_name; \ 266 _ll_result; \ 267 }) 268 269 /** 270 * ll_start() - Point to first entry of first linker-generated array 271 * @_type: Data type of the entry 272 * 273 * This function returns (_type *) pointer to the very first entry of 274 * the very first linker-generated array. 275 * 276 * Since this macro defines the start of the linker-generated arrays, 277 * its leftmost index must be 1. 278 * 279 * Example: 280 * struct my_sub_cmd *msc = ll_start(struct my_sub_cmd); 281 */ 282 #define ll_start(_type) \ 283 ({ \ 284 static char start[0] __aligned(4) __attribute__((unused, \ 285 section(".u_boot_list_1"))); \ 286 (_type *)&start; \ 287 }) 288 289 /** 290 * ll_entry_end() - Point after last entry of last linker-generated array 291 * @_type: Data type of the entry 292 * 293 * This function returns (_type *) pointer after the very last entry of 294 * the very last linker-generated array. 295 * 296 * Since this macro defines the end of the linker-generated arrays, 297 * its leftmost index must be 3. 298 * 299 * Example: 300 * struct my_sub_cmd *msc = ll_end(struct my_sub_cmd); 301 */ 302 #define ll_end(_type) \ 303 ({ \ 304 static char end[0] __aligned(4) __attribute__((unused, \ 305 section(".u_boot_list_3"))); \ 306 (_type *)&end; \ 307 }) 308 309 #endif /* __ASSEMBLY__ */ 310 311 #endif /* __LINKER_LISTS_H__ */ 312