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Linux/include/linux/init.h

  1 #ifndef _LINUX_INIT_H
  2 #define _LINUX_INIT_H
  3 
  4 #include <linux/compiler.h>
  5 #include <linux/types.h>
  6 
  7 /* These macros are used to mark some functions or 
  8  * initialized data (doesn't apply to uninitialized data)
  9  * as `initialization' functions. The kernel can take this
 10  * as hint that the function is used only during the initialization
 11  * phase and free up used memory resources after
 12  *
 13  * Usage:
 14  * For functions:
 15  * 
 16  * You should add __init immediately before the function name, like:
 17  *
 18  * static void __init initme(int x, int y)
 19  * {
 20  *    extern int z; z = x * y;
 21  * }
 22  *
 23  * If the function has a prototype somewhere, you can also add
 24  * __init between closing brace of the prototype and semicolon:
 25  *
 26  * extern int initialize_foobar_device(int, int, int) __init;
 27  *
 28  * For initialized data:
 29  * You should insert __initdata or __initconst between the variable name
 30  * and equal sign followed by value, e.g.:
 31  *
 32  * static int init_variable __initdata = 0;
 33  * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };
 34  *
 35  * Don't forget to initialize data not at file scope, i.e. within a function,
 36  * as gcc otherwise puts the data into the bss section and not into the init
 37  * section.
 38  */
 39 
 40 /* These are for everybody (although not all archs will actually
 41    discard it in modules) */
 42 #define __init          __section(.init.text) __cold notrace
 43 #define __initdata      __section(.init.data)
 44 #define __initconst     __constsection(.init.rodata)
 45 #define __exitdata      __section(.exit.data)
 46 #define __exit_call     __used __section(.exitcall.exit)
 47 
 48 /*
 49  * Some architecture have tool chains which do not handle rodata attributes
 50  * correctly. For those disable special sections for const, so that other
 51  * architectures can annotate correctly.
 52  */
 53 #ifdef CONFIG_BROKEN_RODATA
 54 #define __constsection(x)
 55 #else
 56 #define __constsection(x) __section(x)
 57 #endif
 58 
 59 /*
 60  * modpost check for section mismatches during the kernel build.
 61  * A section mismatch happens when there are references from a
 62  * code or data section to an init section (both code or data).
 63  * The init sections are (for most archs) discarded by the kernel
 64  * when early init has completed so all such references are potential bugs.
 65  * For exit sections the same issue exists.
 66  *
 67  * The following markers are used for the cases where the reference to
 68  * the *init / *exit section (code or data) is valid and will teach
 69  * modpost not to issue a warning.  Intended semantics is that a code or
 70  * data tagged __ref* can reference code or data from init section without
 71  * producing a warning (of course, no warning does not mean code is
 72  * correct, so optimally document why the __ref is needed and why it's OK).
 73  *
 74  * The markers follow same syntax rules as __init / __initdata.
 75  */
 76 #define __ref            __section(.ref.text) noinline
 77 #define __refdata        __section(.ref.data)
 78 #define __refconst       __constsection(.ref.rodata)
 79 
 80 /* compatibility defines */
 81 #define __init_refok     __ref
 82 #define __initdata_refok __refdata
 83 #define __exit_refok     __ref
 84 
 85 
 86 #ifdef MODULE
 87 #define __exitused
 88 #else
 89 #define __exitused  __used
 90 #endif
 91 
 92 #define __exit          __section(.exit.text) __exitused __cold notrace
 93 
 94 /* Used for MEMORY_HOTPLUG */
 95 #define __meminit        __section(.meminit.text) __cold notrace
 96 #define __meminitdata    __section(.meminit.data)
 97 #define __meminitconst   __constsection(.meminit.rodata)
 98 #define __memexit        __section(.memexit.text) __exitused __cold notrace
 99 #define __memexitdata    __section(.memexit.data)
100 #define __memexitconst   __constsection(.memexit.rodata)
101 
102 /* For assembly routines */
103 #define __HEAD          .section        ".head.text","ax"
104 #define __INIT          .section        ".init.text","ax"
105 #define __FINIT         .previous
106 
107 #define __INITDATA      .section        ".init.data","aw",%progbits
108 #define __INITRODATA    .section        ".init.rodata","a",%progbits
109 #define __FINITDATA     .previous
110 
111 #define __MEMINIT        .section       ".meminit.text", "ax"
112 #define __MEMINITDATA    .section       ".meminit.data", "aw"
113 #define __MEMINITRODATA  .section       ".meminit.rodata", "a"
114 
115 /* silence warnings when references are OK */
116 #define __REF            .section       ".ref.text", "ax"
117 #define __REFDATA        .section       ".ref.data", "aw"
118 #define __REFCONST       .section       ".ref.rodata", "a"
119 
120 #ifndef __ASSEMBLY__
121 /*
122  * Used for initialization calls..
123  */
124 typedef int (*initcall_t)(void);
125 typedef void (*exitcall_t)(void);
126 
127 extern initcall_t __con_initcall_start[], __con_initcall_end[];
128 extern initcall_t __security_initcall_start[], __security_initcall_end[];
129 
130 /* Used for contructor calls. */
131 typedef void (*ctor_fn_t)(void);
132 
133 /* Defined in init/main.c */
134 extern int do_one_initcall(initcall_t fn);
135 extern char __initdata boot_command_line[];
136 extern char *saved_command_line;
137 extern unsigned int reset_devices;
138 
139 /* used by init/main.c */
140 void setup_arch(char **);
141 void prepare_namespace(void);
142 void __init load_default_modules(void);
143 int __init init_rootfs(void);
144 
145 #ifdef CONFIG_DEBUG_RODATA
146 void mark_rodata_ro(void);
147 #endif
148 
149 extern void (*late_time_init)(void);
150 
151 extern bool initcall_debug;
152 
153 #endif
154   
155 #ifndef MODULE
156 
157 #ifndef __ASSEMBLY__
158 
159 #ifdef CONFIG_LTO
160 /* Work around a LTO gcc problem: when there is no reference to a variable
161  * in a module it will be moved to the end of the program. This causes
162  * reordering of initcalls which the kernel does not like.
163  * Add a dummy reference function to avoid this. The function is
164  * deleted by the linker.
165  */
166 #define LTO_REFERENCE_INITCALL(x) \
167         ; /* yes this is needed */                      \
168         static __used __exit void *reference_##x(void)  \
169         {                                               \
170                 return &x;                              \
171         }
172 #else
173 #define LTO_REFERENCE_INITCALL(x)
174 #endif
175 
176 /* initcalls are now grouped by functionality into separate 
177  * subsections. Ordering inside the subsections is determined
178  * by link order. 
179  * For backwards compatibility, initcall() puts the call in 
180  * the device init subsection.
181  *
182  * The `id' arg to __define_initcall() is needed so that multiple initcalls
183  * can point at the same handler without causing duplicate-symbol build errors.
184  */
185 
186 #define __define_initcall(fn, id) \
187         static initcall_t __initcall_##fn##id __used \
188         __attribute__((__section__(".initcall" #id ".init"))) = fn; \
189         LTO_REFERENCE_INITCALL(__initcall_##fn##id)
190 
191 /*
192  * Early initcalls run before initializing SMP.
193  *
194  * Only for built-in code, not modules.
195  */
196 #define early_initcall(fn)              __define_initcall(fn, early)
197 
198 /*
199  * A "pure" initcall has no dependencies on anything else, and purely
200  * initializes variables that couldn't be statically initialized.
201  *
202  * This only exists for built-in code, not for modules.
203  * Keep main.c:initcall_level_names[] in sync.
204  */
205 #define pure_initcall(fn)               __define_initcall(fn, 0)
206 
207 #define core_initcall(fn)               __define_initcall(fn, 1)
208 #define core_initcall_sync(fn)          __define_initcall(fn, 1s)
209 #define postcore_initcall(fn)           __define_initcall(fn, 2)
210 #define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
211 #define arch_initcall(fn)               __define_initcall(fn, 3)
212 #define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
213 #define subsys_initcall(fn)             __define_initcall(fn, 4)
214 #define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
215 #define fs_initcall(fn)                 __define_initcall(fn, 5)
216 #define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
217 #define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
218 #define device_initcall(fn)             __define_initcall(fn, 6)
219 #define device_initcall_sync(fn)        __define_initcall(fn, 6s)
220 #define late_initcall(fn)               __define_initcall(fn, 7)
221 #define late_initcall_sync(fn)          __define_initcall(fn, 7s)
222 
223 #define __initcall(fn) device_initcall(fn)
224 
225 #define __exitcall(fn) \
226         static exitcall_t __exitcall_##fn __exit_call = fn
227 
228 #define console_initcall(fn) \
229         static initcall_t __initcall_##fn \
230         __used __section(.con_initcall.init) = fn
231 
232 #define security_initcall(fn) \
233         static initcall_t __initcall_##fn \
234         __used __section(.security_initcall.init) = fn
235 
236 struct obs_kernel_param {
237         const char *str;
238         int (*setup_func)(char *);
239         int early;
240 };
241 
242 /*
243  * Only for really core code.  See moduleparam.h for the normal way.
244  *
245  * Force the alignment so the compiler doesn't space elements of the
246  * obs_kernel_param "array" too far apart in .init.setup.
247  */
248 #define __setup_param(str, unique_id, fn, early)                        \
249         static const char __setup_str_##unique_id[] __initconst         \
250                 __aligned(1) = str;                                     \
251         static struct obs_kernel_param __setup_##unique_id              \
252                 __used __section(.init.setup)                           \
253                 __attribute__((aligned((sizeof(long)))))                \
254                 = { __setup_str_##unique_id, fn, early }
255 
256 #define __setup(str, fn)                                                \
257         __setup_param(str, fn, fn, 0)
258 
259 /*
260  * NOTE: fn is as per module_param, not __setup!
261  * Emits warning if fn returns non-zero.
262  */
263 #define early_param(str, fn)                                            \
264         __setup_param(str, fn, fn, 1)
265 
266 #define early_param_on_off(str_on, str_off, var, config)                \
267                                                                         \
268         int var = IS_ENABLED(config);                                   \
269                                                                         \
270         static int __init parse_##var##_on(char *arg)                   \
271         {                                                               \
272                 var = 1;                                                \
273                 return 0;                                               \
274         }                                                               \
275         __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
276                                                                         \
277         static int __init parse_##var##_off(char *arg)                  \
278         {                                                               \
279                 var = 0;                                                \
280                 return 0;                                               \
281         }                                                               \
282         __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
283 
284 /* Relies on boot_command_line being set */
285 void __init parse_early_param(void);
286 void __init parse_early_options(char *cmdline);
287 #endif /* __ASSEMBLY__ */
288 
289 #else /* MODULE */
290 
291 #define __setup_param(str, unique_id, fn)       /* nothing */
292 #define __setup(str, func)                      /* nothing */
293 #endif
294 
295 /* Data marked not to be saved by software suspend */
296 #define __nosavedata __section(.data..nosave)
297 
298 #ifdef MODULE
299 #define __exit_p(x) x
300 #else
301 #define __exit_p(x) NULL
302 #endif
303 
304 #endif /* _LINUX_INIT_H */
305 

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