1 /* SPDX-License-Identifier: GPL-2.0+ */
3 * include/linker_lists.h
5 * Implementation of linker-generated arrays
7 * Copyright (C) 2012 Marek Vasut <marex@denx.de>
10 #ifndef __LINKER_LISTS_H__
11 #define __LINKER_LISTS_H__
13 #include <linux/compiler.h>
16 * There is no use in including this from ASM files.
17 * So just don't define anything when included from ASM.
20 #if !defined(__ASSEMBLY__)
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
31 * .u_boot_list_ + 2_ + @_list + _2_ + @_entry
33 * and the C variable name is
35 * _u_boot_list + _2_ + @_list + _2_ + @_entry
37 * This ensures uniqueness for both input section and C variable name.
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
44 * %u_boot_list_ + 2_ + @_list + _2_ + @_entry
46 * Entry variables need never be referred to directly.
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
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
58 * %u_boot_list_2_ + @_list + _1_...
59 * %u_boot_list_2_ + @_list + _3_...
61 * Start and end symbols for the whole of the linker lists area can be
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.
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
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").
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:
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
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!
110 #define llsym(_type, _name, _list) \
111 ((_type *)&_u_boot_list_2_##_list##_2_##_name)
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!
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
125 * A variable declared using this macro must be compile-time initialized.
127 * Special precaution must be made when using this macro:
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.
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.
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.
143 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
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)))
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!
160 * This is like ll_entry_declare() but creates multiple entries. It should
161 * be assigned to an array.
163 * ll_entry_declare_list(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
164 * { .x = 3, .y = 4 },
165 * { .x = 8, .y = 2 },
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)))
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
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
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.
192 * Since this macro defines an array start symbol, its leftmost index
193 * must be 2 and its rightmost index must be 1.
196 * struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
198 #define ll_entry_start(_type, _list) \
200 static char start[0] __aligned(4) __attribute__((unused, \
201 section(".u_boot_list_2_"#_list"_1"))); \
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)
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.
215 * Since this macro defines an array end symbol, its leftmost index
216 * must be 2 and its rightmost index must be 3.
219 * struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub);
221 #define ll_entry_end(_type, _list) \
223 static char end[0] __aligned(4) __attribute__((unused, \
224 section(".u_boot_list_2_"#_list"_3"))); \
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
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.
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);
243 #define ll_entry_count(_type, _list) \
245 _type *start = ll_entry_start(_type, _list); \
246 _type *end = ll_entry_end(_type, _list); \
247 unsigned int _ll_result = end - start; \
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
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
262 * ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
267 * struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub);
269 #define ll_entry_get(_type, _name, _list) \
271 extern _type _u_boot_list_2_##_list##_2_##_name; \
272 _type *_ll_result = \
273 &_u_boot_list_2_##_list##_2_##_name; \
278 * ll_start() - Point to first entry of first linker-generated array
279 * @_type: Data type of the entry
281 * This function returns (_type *) pointer to the very first entry of
282 * the very first linker-generated array.
284 * Since this macro defines the start of the linker-generated arrays,
285 * its leftmost index must be 1.
288 * struct my_sub_cmd *msc = ll_start(struct my_sub_cmd);
290 #define ll_start(_type) \
292 static char start[0] __aligned(4) __attribute__((unused, \
293 section(".u_boot_list_1"))); \
298 * ll_end() - Point after last entry of last linker-generated array
299 * @_type: Data type of the entry
301 * This function returns (_type *) pointer after the very last entry of
302 * the very last linker-generated array.
304 * Since this macro defines the end of the linker-generated arrays,
305 * its leftmost index must be 3.
308 * struct my_sub_cmd *msc = ll_end(struct my_sub_cmd);
310 #define ll_end(_type) \
312 static char end[0] __aligned(4) __attribute__((unused, \
313 section(".u_boot_list_3"))); \
317 #endif /* __ASSEMBLY__ */
319 #endif /* __LINKER_LISTS_H__ */