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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 __latent_entropy
 43 #define __initdata      __section(.init.data)
 44 #define __initconst     __section(.init.rodata)
 45 #define __exitdata      __section(.exit.data)
 46 #define __exit_call     __used __section(.exitcall.exit)
 47 
 48 /*
 49  * modpost check for section mismatches during the kernel build.
 50  * A section mismatch happens when there are references from a
 51  * code or data section to an init section (both code or data).
 52  * The init sections are (for most archs) discarded by the kernel
 53  * when early init has completed so all such references are potential bugs.
 54  * For exit sections the same issue exists.
 55  *
 56  * The following markers are used for the cases where the reference to
 57  * the *init / *exit section (code or data) is valid and will teach
 58  * modpost not to issue a warning.  Intended semantics is that a code or
 59  * data tagged __ref* can reference code or data from init section without
 60  * producing a warning (of course, no warning does not mean code is
 61  * correct, so optimally document why the __ref is needed and why it's OK).
 62  *
 63  * The markers follow same syntax rules as __init / __initdata.
 64  */
 65 #define __ref            __section(.ref.text) noinline
 66 #define __refdata        __section(.ref.data)
 67 #define __refconst       __section(.ref.rodata)
 68 
 69 #ifdef MODULE
 70 #define __exitused
 71 #else
 72 #define __exitused  __used
 73 #endif
 74 
 75 #define __exit          __section(.exit.text) __exitused __cold notrace
 76 
 77 /* Used for MEMORY_HOTPLUG */
 78 #define __meminit        __section(.meminit.text) __cold notrace \
 79                                                   __latent_entropy
 80 #define __meminitdata    __section(.meminit.data)
 81 #define __meminitconst   __section(.meminit.rodata)
 82 #define __memexit        __section(.memexit.text) __exitused __cold notrace
 83 #define __memexitdata    __section(.memexit.data)
 84 #define __memexitconst   __section(.memexit.rodata)
 85 
 86 /* For assembly routines */
 87 #define __HEAD          .section        ".head.text","ax"
 88 #define __INIT          .section        ".init.text","ax"
 89 #define __FINIT         .previous
 90 
 91 #define __INITDATA      .section        ".init.data","aw",%progbits
 92 #define __INITRODATA    .section        ".init.rodata","a",%progbits
 93 #define __FINITDATA     .previous
 94 
 95 #define __MEMINIT        .section       ".meminit.text", "ax"
 96 #define __MEMINITDATA    .section       ".meminit.data", "aw"
 97 #define __MEMINITRODATA  .section       ".meminit.rodata", "a"
 98 
 99 /* silence warnings when references are OK */
100 #define __REF            .section       ".ref.text", "ax"
101 #define __REFDATA        .section       ".ref.data", "aw"
102 #define __REFCONST       .section       ".ref.rodata", "a"
103 
104 #ifndef __ASSEMBLY__
105 /*
106  * Used for initialization calls..
107  */
108 typedef int (*initcall_t)(void);
109 typedef void (*exitcall_t)(void);
110 
111 extern initcall_t __con_initcall_start[], __con_initcall_end[];
112 extern initcall_t __security_initcall_start[], __security_initcall_end[];
113 
114 /* Used for contructor calls. */
115 typedef void (*ctor_fn_t)(void);
116 
117 /* Defined in init/main.c */
118 extern int do_one_initcall(initcall_t fn);
119 extern char __initdata boot_command_line[];
120 extern char *saved_command_line;
121 extern unsigned int reset_devices;
122 
123 /* used by init/main.c */
124 void setup_arch(char **);
125 void prepare_namespace(void);
126 void __init load_default_modules(void);
127 int __init init_rootfs(void);
128 
129 #ifdef CONFIG_DEBUG_RODATA
130 void mark_rodata_ro(void);
131 #endif
132 
133 extern void (*late_time_init)(void);
134 
135 extern bool initcall_debug;
136 
137 #endif
138   
139 #ifndef MODULE
140 
141 #ifndef __ASSEMBLY__
142 
143 /*
144  * initcalls are now grouped by functionality into separate
145  * subsections. Ordering inside the subsections is determined
146  * by link order. 
147  * For backwards compatibility, initcall() puts the call in 
148  * the device init subsection.
149  *
150  * The `id' arg to __define_initcall() is needed so that multiple initcalls
151  * can point at the same handler without causing duplicate-symbol build errors.
152  *
153  * Initcalls are run by placing pointers in initcall sections that the
154  * kernel iterates at runtime. The linker can do dead code / data elimination
155  * and remove that completely, so the initcall sections have to be marked
156  * as KEEP() in the linker script.
157  */
158 
159 #define __define_initcall(fn, id) \
160         static initcall_t __initcall_##fn##id __used \
161         __attribute__((__section__(".initcall" #id ".init"))) = fn;
162 
163 /*
164  * Early initcalls run before initializing SMP.
165  *
166  * Only for built-in code, not modules.
167  */
168 #define early_initcall(fn)              __define_initcall(fn, early)
169 
170 /*
171  * A "pure" initcall has no dependencies on anything else, and purely
172  * initializes variables that couldn't be statically initialized.
173  *
174  * This only exists for built-in code, not for modules.
175  * Keep main.c:initcall_level_names[] in sync.
176  */
177 #define pure_initcall(fn)               __define_initcall(fn, 0)
178 
179 #define core_initcall(fn)               __define_initcall(fn, 1)
180 #define core_initcall_sync(fn)          __define_initcall(fn, 1s)
181 #define postcore_initcall(fn)           __define_initcall(fn, 2)
182 #define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
183 #define arch_initcall(fn)               __define_initcall(fn, 3)
184 #define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
185 #define subsys_initcall(fn)             __define_initcall(fn, 4)
186 #define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
187 #define fs_initcall(fn)                 __define_initcall(fn, 5)
188 #define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
189 #define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
190 #define device_initcall(fn)             __define_initcall(fn, 6)
191 #define device_initcall_sync(fn)        __define_initcall(fn, 6s)
192 #define late_initcall(fn)               __define_initcall(fn, 7)
193 #define late_initcall_sync(fn)          __define_initcall(fn, 7s)
194 
195 #define __initcall(fn) device_initcall(fn)
196 
197 #define __exitcall(fn)                                          \
198         static exitcall_t __exitcall_##fn __exit_call = fn
199 
200 #define console_initcall(fn)                                    \
201         static initcall_t __initcall_##fn                       \
202         __used __section(.con_initcall.init) = fn
203 
204 #define security_initcall(fn)                                   \
205         static initcall_t __initcall_##fn                       \
206         __used __section(.security_initcall.init) = fn
207 
208 struct obs_kernel_param {
209         const char *str;
210         int (*setup_func)(char *);
211         int early;
212 };
213 
214 /*
215  * Only for really core code.  See moduleparam.h for the normal way.
216  *
217  * Force the alignment so the compiler doesn't space elements of the
218  * obs_kernel_param "array" too far apart in .init.setup.
219  */
220 #define __setup_param(str, unique_id, fn, early)                        \
221         static const char __setup_str_##unique_id[] __initconst         \
222                 __aligned(1) = str;                                     \
223         static struct obs_kernel_param __setup_##unique_id              \
224                 __used __section(.init.setup)                           \
225                 __attribute__((aligned((sizeof(long)))))                \
226                 = { __setup_str_##unique_id, fn, early }
227 
228 #define __setup(str, fn)                                                \
229         __setup_param(str, fn, fn, 0)
230 
231 /*
232  * NOTE: fn is as per module_param, not __setup!
233  * Emits warning if fn returns non-zero.
234  */
235 #define early_param(str, fn)                                            \
236         __setup_param(str, fn, fn, 1)
237 
238 #define early_param_on_off(str_on, str_off, var, config)                \
239                                                                         \
240         int var = IS_ENABLED(config);                                   \
241                                                                         \
242         static int __init parse_##var##_on(char *arg)                   \
243         {                                                               \
244                 var = 1;                                                \
245                 return 0;                                               \
246         }                                                               \
247         __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
248                                                                         \
249         static int __init parse_##var##_off(char *arg)                  \
250         {                                                               \
251                 var = 0;                                                \
252                 return 0;                                               \
253         }                                                               \
254         __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
255 
256 /* Relies on boot_command_line being set */
257 void __init parse_early_param(void);
258 void __init parse_early_options(char *cmdline);
259 #endif /* __ASSEMBLY__ */
260 
261 #else /* MODULE */
262 
263 #define __setup_param(str, unique_id, fn)       /* nothing */
264 #define __setup(str, func)                      /* nothing */
265 #endif
266 
267 /* Data marked not to be saved by software suspend */
268 #define __nosavedata __section(.data..nosave)
269 
270 #ifdef MODULE
271 #define __exit_p(x) x
272 #else
273 #define __exit_p(x) NULL
274 #endif
275 
276 #endif /* _LINUX_INIT_H */
277 

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