blob: d37fba44dcafc6b1ce6813cca4e8f3d6999e95d5
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 | * 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 |