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