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 * llsym() - Access a linker-generated array entry 24 * @_type: Data type of the entry 25 * @_name: Name of the entry 26 * @_list: name of the list. Should contain only characters allowed 27 * in a C variable name! 28 */ 29 #define llsym(_type, _name, _list) \ 30 ((_type *)&_u_boot_list_2_##_list##_2_##_name) 31 32 /** 33 * ll_entry_declare() - Declare linker-generated array entry 34 * @_type: Data type of the entry 35 * @_name: Name of the entry 36 * @_list: name of the list. Should contain only characters allowed 37 * in a C variable name! 38 * 39 * This macro declares a variable that is placed into a linker-generated 40 * array. This is a basic building block for more advanced use of linker- 41 * generated arrays. The user is expected to build their own macro wrapper 42 * around this one. 43 * 44 * A variable declared using this macro must be compile-time initialized. 45 * 46 * Special precaution must be made when using this macro: 47 * 48 * 1) The _type must not contain the "static" keyword, otherwise the 49 * entry is generated and can be iterated but is listed in the map 50 * file and cannot be retrieved by name. 51 * 52 * 2) In case a section is declared that contains some array elements AND 53 * a subsection of this section is declared and contains some elements, 54 * it is imperative that the elements are of the same type. 55 * 56 * 3) In case an outer section is declared that contains some array elements 57 * AND an inner subsection of this section is declared and contains some 58 * elements, then when traversing the outer section, even the elements of 59 * the inner sections are present in the array. 60 * 61 * Example: 62 * 63 * :: 64 * 65 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 66 * .x = 3, 67 * .y = 4, 68 * }; 69 */ 70 #define ll_entry_declare(_type, _name, _list) \ 71 _type _u_boot_list_2_##_list##_2_##_name __aligned(4) \ 72 __attribute__((unused)) \ 73 __section("__u_boot_list_2_"#_list"_2_"#_name) 74 75 /** 76 * ll_entry_declare_list() - Declare a list of link-generated array entries 77 * @_type: Data type of each entry 78 * @_name: Name of the entry 79 * @_list: name of the list. Should contain only characters allowed 80 * in a C variable name! 81 * 82 * This is like ll_entry_declare() but creates multiple entries. It should 83 * be assigned to an array. 84 * 85 * :: 86 * 87 * ll_entry_declare_list(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 88 * { .x = 3, .y = 4 }, 89 * { .x = 8, .y = 2 }, 90 * { .x = 1, .y = 7 } 91 * }; 92 */ 93 #define ll_entry_declare_list(_type, _name, _list) \ 94 _type _u_boot_list_2_##_list##_2_##_name[] __aligned(4) \ 95 __attribute__((unused)) \ 96 __section("__u_boot_list_2_"#_list"_2_"#_name) 97 98 /* 99 * We need a 0-byte-size type for iterator symbols, and the compiler 100 * does not allow defining objects of C type 'void'. Using an empty 101 * struct is allowed by the compiler, but causes gcc versions 4.4 and 102 * below to complain about aliasing. Therefore we use the next best 103 * thing: zero-sized arrays, which are both 0-byte-size and exempt from 104 * aliasing warnings. 105 */ 106 107 /** 108 * ll_entry_start() - Point to first entry of linker-generated array 109 * @_type: Data type of the entry 110 * @_list: Name of the list in which this entry is placed 111 * 112 * This function returns ``(_type *)`` pointer to the very first entry of a 113 * linker-generated array placed into subsection of __u_boot_list section 114 * specified by _list argument. 115 * 116 * Since this macro defines an array start symbol, its leftmost index 117 * must be 2 and its rightmost index must be 1. 118 * 119 * Example: 120 * 121 * :: 122 * 123 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 124 */ 125 #define ll_entry_start(_type, _list) \ 126 ({ \ 127 static char start[0] __aligned(CONFIG_LINKER_LIST_ALIGN) \ 128 __attribute__((unused)) \ 129 __section("__u_boot_list_2_"#_list"_1"); \ 130 _type * tmp = (_type *)&start; \ 131 asm("":"+r"(tmp)); \ 132 tmp; \ 133 }) 134 135 /** 136 * ll_entry_end() - Point after last entry of linker-generated array 137 * @_type: Data type of the entry 138 * @_list: Name of the list in which this entry is placed 139 * (with underscores instead of dots) 140 * 141 * This function returns ``(_type *)`` pointer after the very last entry of 142 * a linker-generated array placed into subsection of __u_boot_list 143 * section specified by _list argument. 144 * 145 * Since this macro defines an array end symbol, its leftmost index 146 * must be 2 and its rightmost index must be 3. 147 * 148 * Example: 149 * 150 * :: 151 * 152 * struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub); 153 */ 154 #define ll_entry_end(_type, _list) \ 155 ({ \ 156 static char end[0] __aligned(4) __attribute__((unused)) \ 157 __section("__u_boot_list_2_"#_list"_3"); \ 158 _type * tmp = (_type *)&end; \ 159 asm("":"+r"(tmp)); \ 160 tmp; \ 161 }) 162 /** 163 * ll_entry_count() - Return the number of elements in linker-generated array 164 * @_type: Data type of the entry 165 * @_list: Name of the list of which the number of elements is computed 166 * 167 * This function returns the number of elements of a linker-generated array 168 * placed into subsection of __u_boot_list section specified by _list 169 * argument. The result is of an unsigned int type. 170 * 171 * Example: 172 * 173 * :: 174 * 175 * int i; 176 * const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub); 177 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub); 178 * for (i = 0; i < count; i++, msc++) 179 * printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y); 180 */ 181 #define ll_entry_count(_type, _list) \ 182 ({ \ 183 _type *start = ll_entry_start(_type, _list); \ 184 _type *end = ll_entry_end(_type, _list); \ 185 unsigned int _ll_result = end - start; \ 186 _ll_result; \ 187 }) 188 189 /** 190 * Declares a symbol that points to the start/end of the list. 191 * 192 * @_sym: Arbitrary name for the symbol (to use later in the file) 193 * @_type: Data type of the entry 194 * @_list: Name of the list in which this entry is placed 195 * 196 * The name of the (new) symbol is arbitrary and can be anything that is not 197 * already declared in the file where it appears. It is provided in _sym and 198 * can then be used (later in the same file) within a data structure. 199 * The _type and _list arguments must match those passed to ll_entry_start/end() 200 * 201 * Example: 202 * 203 * Here we want to record the start of each sub-command in a list. We have two 204 * sub-commands, 'bob' and 'mary'. 205 * 206 * In bob.c:: 207 * 208 * ll_entry_declare(struct my_sub_cmd, bob_cmd, cmd_sub) = {...}; 209 * 210 * In mary.c:: 211 * 212 * ll_entry_declare(struct my_sub_cmd, mary_cmd, cmd_sub) = {...}; 213 * 214 * In a different file where we want a list the start of all sub-commands. 215 * It is not possible to use ll_entry_start() in a data structure, due to its 216 * use of code inside expressions - ({ ... }) - so this fails to compile: 217 * 218 * In sub_cmds.c:: 219 * 220 * struct cmd_sub *my_list[] = { 221 * ll_entry_start(cmd_sub, bob), 222 * ll_entry_start(cmd_sub, bob), 223 * }; 224 * 225 * Instead, we can use:: 226 * 227 * ll_start_decl(bob, struct my_sub_cmd, cmd_sub); 228 * ll_start_decl(mary, struct my_sub_cmd, cmd_sub); 229 * 230 * struct cmd_sub *my_list[] = { 231 * bob, 232 * mary, 233 * }; 234 * 235 * So 'bob' is declared as symbol, a struct my_list * which points to the 236 * start of the bob sub-commands. It is then used in my_list[] 237 */ 238 #define ll_start_decl(_sym, _type, _list) \ 239 static _type _sym[0] __aligned(CONFIG_LINKER_LIST_ALIGN) \ 240 __maybe_unused __section("__u_boot_list_2_" #_list "_1") 241 242 #define ll_end_decl(_sym, _type, _list) \ 243 static _type _sym[0] __aligned(CONFIG_LINKER_LIST_ALIGN) \ 244 __maybe_unused __section("__u_boot_list_2_" #_list "_3") 245 246 /** 247 * ll_entry_get() - Retrieve entry from linker-generated array by name 248 * @_type: Data type of the entry 249 * @_name: Name of the entry 250 * @_list: Name of the list in which this entry is placed 251 * 252 * This function returns a pointer to a particular entry in linker-generated 253 * array identified by the subsection of u_boot_list where the entry resides 254 * and it's name. 255 * 256 * Example: 257 * 258 * :: 259 * 260 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = { 261 * .x = 3, 262 * .y = 4, 263 * }; 264 * ... 265 * struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub); 266 */ 267 #define ll_entry_get(_type, _name, _list) \ 268 ({ \ 269 extern _type _u_boot_list_2_##_list##_2_##_name; \ 270 _type *_ll_result = \ 271 &_u_boot_list_2_##_list##_2_##_name; \ 272 _ll_result; \ 273 }) 274 275 /** 276 * ll_entry_ref() - Get a reference to a linker-generated array entry 277 * 278 * Once an extern ll_entry_declare() has been used to declare the reference, 279 * this macro allows the entry to be accessed. 280 * 281 * This is like ll_entry_get(), but without the extra code, so it is suitable 282 * for putting into data structures. 283 * 284 * @_type: C type of the list entry, e.g. 'struct foo' 285 * @_name: name of the entry 286 * @_list: name of the list 287 */ 288 #define ll_entry_ref(_type, _name, _list) \ 289 ((_type *)&_u_boot_list_2_##_list##_2_##_name) 290 291 /** 292 * ll_start() - Point to first entry of first linker-generated array 293 * @_type: Data type of the entry 294 * 295 * This function returns ``(_type *)`` pointer to the very first entry of 296 * the very first linker-generated array. 297 * 298 * Since this macro defines the start of the linker-generated arrays, 299 * its leftmost index must be 1. 300 * 301 * Example: 302 * 303 * :: 304 * 305 * struct my_sub_cmd *msc = ll_start(struct my_sub_cmd); 306 */ 307 #define ll_start(_type) \ 308 ({ \ 309 static char start[0] __aligned(4) __attribute__((unused)) \ 310 __section("__u_boot_list_1"); \ 311 _type * tmp = (_type *)&start; \ 312 asm("":"+r"(tmp)); \ 313 tmp; \ 314 }) 315 316 /** 317 * ll_end() - Point after last entry of last linker-generated array 318 * @_type: Data type of the entry 319 * 320 * This function returns ``(_type *)`` pointer after the very last entry of 321 * the very last linker-generated array. 322 * 323 * Since this macro defines the end of the linker-generated arrays, 324 * its leftmost index must be 3. 325 * 326 * Example: 327 * 328 * :: 329 * 330 * struct my_sub_cmd *msc = ll_end(struct my_sub_cmd); 331 */ 332 #define ll_end(_type) \ 333 ({ \ 334 static char end[0] __aligned(4) __attribute__((unused)) \ 335 __section("__u_boot_list_3"); \ 336 _type * tmp = (_type *)&end; \ 337 asm("":"+r"(tmp)); \ 338 tmp; \ 339 }) 340 341 #endif /* __ASSEMBLY__ */ 342 343 #endif /* __LINKER_LISTS_H__ */ 344