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 containning 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 * setion 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 * We need a 0-byte-size type for iterator symbols, and the compiler 147 * does not allow defining objects of C type 'void'. Using an empty 148 * struct is allowed by the compiler, but causes gcc versions 4.4 and 149 * below to complain about aliasing. Therefore we use the next best 150 * thing: zero-sized arrays, which are both 0-byte-size and exempt from 151 * aliasing warnings. 152 */ 153 154 /** 155 * ll_entry_start() - Point to first entry of linker-generated array 156 * @_type: Data type of the entry 157 * @_list: Name of the list in which this entry is placed 158 * 159 * This function returns (_type *) pointer to the very first entry of a 160 * linker-generated array placed into subsection of .u_boot_list section 161 * specified by _list argument. 162 * 163 * Since this macro defines an array start symbol, its leftmost index 164 * must be 2 and its rightmost index must be 1. 165 * 166 * Example: 167 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 168 */ 169 #define ll_entry_start(_type, _list) \ 170 ({ \ 171 static char start[0] __aligned(4) __attribute__((unused, \ 172 section(".u_boot_list_2_"#_list"_1"))); \ 173 (_type *)&start; \ 174 }) 175 176 /** 177 * ll_entry_end() - Point after last entry of linker-generated array 178 * @_type: Data type of the entry 179 * @_list: Name of the list in which this entry is placed 180 * (with underscores instead of dots) 181 * 182 * This function returns (_type *) pointer after the very last entry of 183 * a linker-generated array placed into subsection of .u_boot_list 184 * section specified by _list argument. 185 * 186 * Since this macro defines an array end symbol, its leftmost index 187 * must be 2 and its rightmost index must be 3. 188 * 189 * Example: 190 * struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub); 191 */ 192 #define ll_entry_end(_type, _list) \ 193 ({ \ 194 static char end[0] __aligned(4) __attribute__((unused, \ 195 section(".u_boot_list_2_"#_list"_3"))); \ 196 (_type *)&end; \ 197 }) 198 /** 199 * ll_entry_count() - Return the number of elements in linker-generated array 200 * @_type: Data type of the entry 201 * @_list: Name of the list of which the number of elements is computed 202 * 203 * This function returns the number of elements of a linker-generated array 204 * placed into subsection of .u_boot_list section specified by _list 205 * argument. The result is of an unsigned int type. 206 * 207 * Example: 208 * int i; 209 * const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub); 210 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 211 * for (i = 0; i < count; i++, msc++) 212 * printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y); 213 */ 214 #define ll_entry_count(_type, _list) \ 215 ({ \ 216 _type *start = ll_entry_start(_type, _list); \ 217 _type *end = ll_entry_end(_type, _list); \ 218 unsigned int _ll_result = end - start; \ 219 _ll_result; \ 220 }) 221 222 /** 223 * ll_entry_get() - Retrieve entry from linker-generated array by name 224 * @_type: Data type of the entry 225 * @_name: Name of the entry 226 * @_list: Name of the list in which this entry is placed 227 * 228 * This function returns a pointer to a particular entry in LG-array 229 * identified by the subsection of u_boot_list where the entry resides 230 * and it's name. 231 * 232 * Example: 233 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 234 * .x = 3, 235 * .y = 4, 236 * }; 237 * ... 238 * struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub); 239 */ 240 #define ll_entry_get(_type, _name, _list) \ 241 ({ \ 242 extern _type _u_boot_list_2_##_list##_2_##_name; \ 243 _type *_ll_result = \ 244 &_u_boot_list_2_##_list##_2_##_name; \ 245 _ll_result; \ 246 }) 247 248 /** 249 * ll_start() - Point to first entry of first linker-generated array 250 * @_type: Data type of the entry 251 * 252 * This function returns (_type *) pointer to the very first entry of 253 * the very first linker-generated array. 254 * 255 * Since this macro defines the start of the linker-generated arrays, 256 * its leftmost index must be 1. 257 * 258 * Example: 259 * struct my_sub_cmd *msc = ll_start(struct my_sub_cmd); 260 */ 261 #define ll_start(_type) \ 262 ({ \ 263 static char start[0] __aligned(4) __attribute__((unused, \ 264 section(".u_boot_list_1"))); \ 265 (_type *)&start; \ 266 }) 267 268 /** 269 * ll_entry_end() - Point after last entry of last linker-generated array 270 * @_type: Data type of the entry 271 * 272 * This function returns (_type *) pointer after the very last entry of 273 * the very last linker-generated array. 274 * 275 * Since this macro defines the end of the linker-generated arrays, 276 * its leftmost index must be 3. 277 * 278 * Example: 279 * struct my_sub_cmd *msc = ll_end(struct my_sub_cmd); 280 */ 281 #define ll_end(_type) \ 282 ({ \ 283 static char end[0] __aligned(4) __attribute__((unused, \ 284 section(".u_boot_list_3"))); \ 285 (_type *)&end; \ 286 }) 287 288 #endif /* __ASSEMBLY__ */ 289 290 #endif /* __LINKER_LISTS_H__ */ 291