xref: /openbmc/u-boot/include/linker_lists.h (revision 2ae23a28)
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(4) __attribute__((unused,	\
128 		section(".u_boot_list_2_"#_list"_1")));			\
129 	(_type *)&start;						\
130 })
131 
132 /**
133  * ll_entry_end() - Point after last entry of linker-generated array
134  * @_type:	Data type of the entry
135  * @_list:	Name of the list in which this entry is placed
136  *		(with underscores instead of dots)
137  *
138  * This function returns ``(_type *)`` pointer after the very last entry of
139  * a linker-generated array placed into subsection of .u_boot_list
140  * section specified by _list argument.
141  *
142  * Since this macro defines an array end symbol, its leftmost index
143  * must be 2 and its rightmost index must be 3.
144  *
145  * Example:
146  *
147  * ::
148  *
149  *   struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub);
150  */
151 #define ll_entry_end(_type, _list)					\
152 ({									\
153 	static char end[0] __aligned(4) __attribute__((unused,		\
154 		section(".u_boot_list_2_"#_list"_3")));			\
155 	(_type *)&end;							\
156 })
157 /**
158  * ll_entry_count() - Return the number of elements in linker-generated array
159  * @_type:	Data type of the entry
160  * @_list:	Name of the list of which the number of elements is computed
161  *
162  * This function returns the number of elements of a linker-generated array
163  * placed into subsection of .u_boot_list section specified by _list
164  * argument. The result is of an unsigned int type.
165  *
166  * Example:
167  *
168  * ::
169  *
170  *   int i;
171  *   const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub);
172  *   struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
173  *   for (i = 0; i < count; i++, msc++)
174  *           printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y);
175  */
176 #define ll_entry_count(_type, _list)					\
177 	({								\
178 		_type *start = ll_entry_start(_type, _list);		\
179 		_type *end = ll_entry_end(_type, _list);		\
180 		unsigned int _ll_result = end - start;			\
181 		_ll_result;						\
182 	})
183 
184 /**
185  * ll_entry_get() - Retrieve entry from linker-generated array by name
186  * @_type:	Data type of the entry
187  * @_name:	Name of the entry
188  * @_list:	Name of the list in which this entry is placed
189  *
190  * This function returns a pointer to a particular entry in linker-generated
191  * array identified by the subsection of u_boot_list where the entry resides
192  * and it's name.
193  *
194  * Example:
195  *
196  * ::
197  *
198  *   ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
199  *           .x = 3,
200  *           .y = 4,
201  *   };
202  *   ...
203  *   struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub);
204  */
205 #define ll_entry_get(_type, _name, _list)				\
206 	({								\
207 		extern _type _u_boot_list_2_##_list##_2_##_name;	\
208 		_type *_ll_result =					\
209 			&_u_boot_list_2_##_list##_2_##_name;		\
210 		_ll_result;						\
211 	})
212 
213 /**
214  * ll_start() - Point to first entry of first linker-generated array
215  * @_type:	Data type of the entry
216  *
217  * This function returns ``(_type *)`` pointer to the very first entry of
218  * the very first linker-generated array.
219  *
220  * Since this macro defines the start of the linker-generated arrays,
221  * its leftmost index must be 1.
222  *
223  * Example:
224  *
225  * ::
226  *
227  *   struct my_sub_cmd *msc = ll_start(struct my_sub_cmd);
228  */
229 #define ll_start(_type)							\
230 ({									\
231 	static char start[0] __aligned(4) __attribute__((unused,	\
232 		section(".u_boot_list_1")));				\
233 	(_type *)&start;						\
234 })
235 
236 /**
237  * ll_end() - Point after last entry of last linker-generated array
238  * @_type:	Data type of the entry
239  *
240  * This function returns ``(_type *)`` pointer after the very last entry of
241  * the very last linker-generated array.
242  *
243  * Since this macro defines the end of the linker-generated arrays,
244  * its leftmost index must be 3.
245  *
246  * Example:
247  *
248  * ::
249  *
250  *   struct my_sub_cmd *msc = ll_end(struct my_sub_cmd);
251  */
252 #define ll_end(_type)							\
253 ({									\
254 	static char end[0] __aligned(4) __attribute__((unused,		\
255 		section(".u_boot_list_3")));				\
256 	(_type *)&end;							\
257 })
258 
259 #endif /* __ASSEMBLY__ */
260 
261 #endif	/* __LINKER_LISTS_H__ */
262