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 * ll_entry_get() - Retrieve entry from linker-generated array by name
191 * @_type:	Data type of the entry
192 * @_name:	Name of the entry
193 * @_list:	Name of the list in which this entry is placed
194 *
195 * This function returns a pointer to a particular entry in linker-generated
196 * array identified by the subsection of u_boot_list where the entry resides
197 * and it's name.
198 *
199 * Example:
200 *
201 * ::
202 *
203 *   ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
204 *           .x = 3,
205 *           .y = 4,
206 *   };
207 *   ...
208 *   struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub);
209 */
210#define ll_entry_get(_type, _name, _list)				\
211	({								\
212		extern _type _u_boot_list_2_##_list##_2_##_name;	\
213		_type *_ll_result =					\
214			&_u_boot_list_2_##_list##_2_##_name;		\
215		_ll_result;						\
216	})
217
218/**
219 * ll_entry_ref() - Get a reference to a linker-generated array entry
220 *
221 * Once an extern ll_entry_declare() has been used to declare the reference,
222 * this macro allows the entry to be accessed.
223 *
224 * This is like ll_entry_get(), but without the extra code, so it is suitable
225 * for putting into data structures.
226 *
227 * @_type: C type of the list entry, e.g. 'struct foo'
228 * @_name: name of the entry
229 * @_list: name of the list
230 */
231#define ll_entry_ref(_type, _name, _list)				\
232	((_type *)&_u_boot_list_2_##_list##_2_##_name)
233
234/**
235 * ll_start() - Point to first entry of first linker-generated array
236 * @_type:	Data type of the entry
237 *
238 * This function returns ``(_type *)`` pointer to the very first entry of
239 * the very first linker-generated array.
240 *
241 * Since this macro defines the start of the linker-generated arrays,
242 * its leftmost index must be 1.
243 *
244 * Example:
245 *
246 * ::
247 *
248 *   struct my_sub_cmd *msc = ll_start(struct my_sub_cmd);
249 */
250#define ll_start(_type)							\
251({									\
252	static char start[0] __aligned(4) __attribute__((unused))	\
253		__section("__u_boot_list_1");				\
254	_type * tmp = (_type *)&start;					\
255	asm("":"+r"(tmp));						\
256	tmp;								\
257})
258
259/**
260 * ll_end() - Point after last entry of last linker-generated array
261 * @_type:	Data type of the entry
262 *
263 * This function returns ``(_type *)`` pointer after the very last entry of
264 * the very last linker-generated array.
265 *
266 * Since this macro defines the end of the linker-generated arrays,
267 * its leftmost index must be 3.
268 *
269 * Example:
270 *
271 * ::
272 *
273 *   struct my_sub_cmd *msc = ll_end(struct my_sub_cmd);
274 */
275#define ll_end(_type)							\
276({									\
277	static char end[0] __aligned(4) __attribute__((unused))		\
278		__section("__u_boot_list_3");				\
279	_type * tmp = (_type *)&end;					\
280	asm("":"+r"(tmp));						\
281	tmp;								\
282})
283
284#endif /* __ASSEMBLY__ */
285
286#endif	/* __LINKER_LISTS_H__ */
287