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TOMOYO Linux Cross Reference
Linux/include/linux/init.h

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  2 #ifndef _LINUX_INIT_H
  3 #define _LINUX_INIT_H
  4 
  5 #include <linux/compiler.h>
  6 #include <linux/types.h>
  7 
  8 /* Built-in __init functions needn't be compiled with retpoline */
  9 #if defined(__noretpoline) && !defined(MODULE)
 10 #define __noinitretpoline __noretpoline
 11 #else
 12 #define __noinitretpoline
 13 #endif
 14 
 15 /* These macros are used to mark some functions or 
 16  * initialized data (doesn't apply to uninitialized data)
 17  * as `initialization' functions. The kernel can take this
 18  * as hint that the function is used only during the initialization
 19  * phase and free up used memory resources after
 20  *
 21  * Usage:
 22  * For functions:
 23  * 
 24  * You should add __init immediately before the function name, like:
 25  *
 26  * static void __init initme(int x, int y)
 27  * {
 28  *    extern int z; z = x * y;
 29  * }
 30  *
 31  * If the function has a prototype somewhere, you can also add
 32  * __init between closing brace of the prototype and semicolon:
 33  *
 34  * extern int initialize_foobar_device(int, int, int) __init;
 35  *
 36  * For initialized data:
 37  * You should insert __initdata or __initconst between the variable name
 38  * and equal sign followed by value, e.g.:
 39  *
 40  * static int init_variable __initdata = 0;
 41  * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };
 42  *
 43  * Don't forget to initialize data not at file scope, i.e. within a function,
 44  * as gcc otherwise puts the data into the bss section and not into the init
 45  * section.
 46  */
 47 
 48 /* These are for everybody (although not all archs will actually
 49    discard it in modules) */
 50 #define __init          __section(".init.text") __cold  __latent_entropy __noinitretpoline
 51 #define __initdata      __section(".init.data")
 52 #define __initconst     __section(".init.rodata")
 53 #define __exitdata      __section(".exit.data")
 54 #define __exit_call     __used __section(".exitcall.exit")
 55 
 56 /*
 57  * modpost check for section mismatches during the kernel build.
 58  * A section mismatch happens when there are references from a
 59  * code or data section to an init section (both code or data).
 60  * The init sections are (for most archs) discarded by the kernel
 61  * when early init has completed so all such references are potential bugs.
 62  * For exit sections the same issue exists.
 63  *
 64  * The following markers are used for the cases where the reference to
 65  * the *init / *exit section (code or data) is valid and will teach
 66  * modpost not to issue a warning.  Intended semantics is that a code or
 67  * data tagged __ref* can reference code or data from init section without
 68  * producing a warning (of course, no warning does not mean code is
 69  * correct, so optimally document why the __ref is needed and why it's OK).
 70  *
 71  * The markers follow same syntax rules as __init / __initdata.
 72  */
 73 #define __ref            __section(".ref.text") noinline
 74 #define __refdata        __section(".ref.data")
 75 #define __refconst       __section(".ref.rodata")
 76 
 77 #ifdef MODULE
 78 #define __exitused
 79 #else
 80 #define __exitused  __used
 81 #endif
 82 
 83 #define __exit          __section(".exit.text") __exitused __cold notrace
 84 
 85 /* Used for MEMORY_HOTPLUG */
 86 #define __meminit        __section(".meminit.text") __cold notrace \
 87                                                   __latent_entropy
 88 #define __meminitdata    __section(".meminit.data")
 89 #define __meminitconst   __section(".meminit.rodata")
 90 #define __memexit        __section(".memexit.text") __exitused __cold notrace
 91 #define __memexitdata    __section(".memexit.data")
 92 #define __memexitconst   __section(".memexit.rodata")
 93 
 94 /* For assembly routines */
 95 #define __HEAD          .section        ".head.text","ax"
 96 #define __INIT          .section        ".init.text","ax"
 97 #define __FINIT         .previous
 98 
 99 #define __INITDATA      .section        ".init.data","aw",%progbits
100 #define __INITRODATA    .section        ".init.rodata","a",%progbits
101 #define __FINITDATA     .previous
102 
103 #define __MEMINIT        .section       ".meminit.text", "ax"
104 #define __MEMINITDATA    .section       ".meminit.data", "aw"
105 #define __MEMINITRODATA  .section       ".meminit.rodata", "a"
106 
107 /* silence warnings when references are OK */
108 #define __REF            .section       ".ref.text", "ax"
109 #define __REFDATA        .section       ".ref.data", "aw"
110 #define __REFCONST       .section       ".ref.rodata", "a"
111 
112 #ifndef __ASSEMBLY__
113 /*
114  * Used for initialization calls..
115  */
116 typedef int (*initcall_t)(void);
117 typedef void (*exitcall_t)(void);
118 
119 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
120 typedef int initcall_entry_t;
121 
122 static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
123 {
124         return offset_to_ptr(entry);
125 }
126 #else
127 typedef initcall_t initcall_entry_t;
128 
129 static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
130 {
131         return *entry;
132 }
133 #endif
134 
135 extern initcall_entry_t __con_initcall_start[], __con_initcall_end[];
136 
137 /* Used for contructor calls. */
138 typedef void (*ctor_fn_t)(void);
139 
140 struct file_system_type;
141 
142 /* Defined in init/main.c */
143 extern int do_one_initcall(initcall_t fn);
144 extern char __initdata boot_command_line[];
145 extern char *saved_command_line;
146 extern unsigned int reset_devices;
147 
148 /* used by init/main.c */
149 void setup_arch(char **);
150 void prepare_namespace(void);
151 void __init init_rootfs(void);
152 extern struct file_system_type rootfs_fs_type;
153 
154 #if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
155 extern bool rodata_enabled;
156 #endif
157 #ifdef CONFIG_STRICT_KERNEL_RWX
158 void mark_rodata_ro(void);
159 #endif
160 
161 extern void (*late_time_init)(void);
162 
163 extern bool initcall_debug;
164 
165 #endif
166   
167 #ifndef MODULE
168 
169 #ifndef __ASSEMBLY__
170 
171 /*
172  * initcalls are now grouped by functionality into separate
173  * subsections. Ordering inside the subsections is determined
174  * by link order. 
175  * For backwards compatibility, initcall() puts the call in 
176  * the device init subsection.
177  *
178  * The `id' arg to __define_initcall() is needed so that multiple initcalls
179  * can point at the same handler without causing duplicate-symbol build errors.
180  *
181  * Initcalls are run by placing pointers in initcall sections that the
182  * kernel iterates at runtime. The linker can do dead code / data elimination
183  * and remove that completely, so the initcall sections have to be marked
184  * as KEEP() in the linker script.
185  */
186 
187 /* Format: <modname>__<counter>_<line>_<fn> */
188 #define __initcall_id(fn)                                       \
189         __PASTE(__KBUILD_MODNAME,                               \
190         __PASTE(__,                                             \
191         __PASTE(__COUNTER__,                                    \
192         __PASTE(_,                                              \
193         __PASTE(__LINE__,                                       \
194         __PASTE(_, fn))))))
195 
196 /* Format: __<prefix>__<iid><id> */
197 #define __initcall_name(prefix, __iid, id)                      \
198         __PASTE(__,                                             \
199         __PASTE(prefix,                                         \
200         __PASTE(__,                                             \
201         __PASTE(__iid, id))))
202 
203 #ifdef CONFIG_LTO_CLANG
204 /*
205  * With LTO, the compiler doesn't necessarily obey link order for
206  * initcalls. In order to preserve the correct order, we add each
207  * variable into its own section and generate a linker script (in
208  * scripts/link-vmlinux.sh) to specify the order of the sections.
209  */
210 #define __initcall_section(__sec, __iid)                        \
211         #__sec ".init.." #__iid
212 
213 /*
214  * With LTO, the compiler can rename static functions to avoid
215  * global naming collisions. We use a global stub function for
216  * initcalls to create a stable symbol name whose address can be
217  * taken in inline assembly when PREL32 relocations are used.
218  */
219 #define __initcall_stub(fn, __iid, id)                          \
220         __initcall_name(initstub, __iid, id)
221 
222 #define __define_initcall_stub(__stub, fn)                      \
223         int __init __stub(void);                                \
224         int __init __stub(void)                                 \
225         {                                                       \
226                 return fn();                                    \
227         }                                                       \
228         __ADDRESSABLE(__stub)
229 #else
230 #define __initcall_section(__sec, __iid)                        \
231         #__sec ".init"
232 
233 #define __initcall_stub(fn, __iid, id)  fn
234 
235 #define __define_initcall_stub(__stub, fn)                      \
236         __ADDRESSABLE(fn)
237 #endif
238 
239 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
240 #define ____define_initcall(fn, __stub, __name, __sec)          \
241         __define_initcall_stub(__stub, fn)                      \
242         asm(".section   \"" __sec "\", \"a\"            \n"     \
243             __stringify(__name) ":                      \n"     \
244             ".long      " __stringify(__stub) " - .     \n"     \
245             ".previous                                  \n");
246 #else
247 #define ____define_initcall(fn, __unused, __name, __sec)        \
248         static initcall_t __name __used                         \
249                 __attribute__((__section__(__sec))) = fn;
250 #endif
251 
252 #define __unique_initcall(fn, id, __sec, __iid)                 \
253         ____define_initcall(fn,                                 \
254                 __initcall_stub(fn, __iid, id),                 \
255                 __initcall_name(initcall, __iid, id),           \
256                 __initcall_section(__sec, __iid))
257 
258 #define ___define_initcall(fn, id, __sec)                       \
259         __unique_initcall(fn, id, __sec, __initcall_id(fn))
260 
261 #define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
262 
263 /*
264  * Early initcalls run before initializing SMP.
265  *
266  * Only for built-in code, not modules.
267  */
268 #define early_initcall(fn)              __define_initcall(fn, early)
269 
270 /*
271  * A "pure" initcall has no dependencies on anything else, and purely
272  * initializes variables that couldn't be statically initialized.
273  *
274  * This only exists for built-in code, not for modules.
275  * Keep main.c:initcall_level_names[] in sync.
276  */
277 #define pure_initcall(fn)               __define_initcall(fn, 0)
278 
279 #define core_initcall(fn)               __define_initcall(fn, 1)
280 #define core_initcall_sync(fn)          __define_initcall(fn, 1s)
281 #define postcore_initcall(fn)           __define_initcall(fn, 2)
282 #define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
283 #define arch_initcall(fn)               __define_initcall(fn, 3)
284 #define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
285 #define subsys_initcall(fn)             __define_initcall(fn, 4)
286 #define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
287 #define fs_initcall(fn)                 __define_initcall(fn, 5)
288 #define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
289 #define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
290 #define device_initcall(fn)             __define_initcall(fn, 6)
291 #define device_initcall_sync(fn)        __define_initcall(fn, 6s)
292 #define late_initcall(fn)               __define_initcall(fn, 7)
293 #define late_initcall_sync(fn)          __define_initcall(fn, 7s)
294 
295 #define __initcall(fn) device_initcall(fn)
296 
297 #define __exitcall(fn)                                          \
298         static exitcall_t __exitcall_##fn __exit_call = fn
299 
300 #define console_initcall(fn)    ___define_initcall(fn, con, .con_initcall)
301 
302 struct obs_kernel_param {
303         const char *str;
304         int (*setup_func)(char *);
305         int early;
306 };
307 
308 /*
309  * Only for really core code.  See moduleparam.h for the normal way.
310  *
311  * Force the alignment so the compiler doesn't space elements of the
312  * obs_kernel_param "array" too far apart in .init.setup.
313  */
314 #define __setup_param(str, unique_id, fn, early)                        \
315         static const char __setup_str_##unique_id[] __initconst         \
316                 __aligned(1) = str;                                     \
317         static struct obs_kernel_param __setup_##unique_id              \
318                 __used __section(".init.setup")                         \
319                 __aligned(__alignof__(struct obs_kernel_param))         \
320                 = { __setup_str_##unique_id, fn, early }
321 
322 #define __setup(str, fn)                                                \
323         __setup_param(str, fn, fn, 0)
324 
325 /*
326  * NOTE: fn is as per module_param, not __setup!
327  * Emits warning if fn returns non-zero.
328  */
329 #define early_param(str, fn)                                            \
330         __setup_param(str, fn, fn, 1)
331 
332 #define early_param_on_off(str_on, str_off, var, config)                \
333                                                                         \
334         int var = IS_ENABLED(config);                                   \
335                                                                         \
336         static int __init parse_##var##_on(char *arg)                   \
337         {                                                               \
338                 var = 1;                                                \
339                 return 0;                                               \
340         }                                                               \
341         early_param(str_on, parse_##var##_on);                          \
342                                                                         \
343         static int __init parse_##var##_off(char *arg)                  \
344         {                                                               \
345                 var = 0;                                                \
346                 return 0;                                               \
347         }                                                               \
348         early_param(str_off, parse_##var##_off)
349 
350 /* Relies on boot_command_line being set */
351 void __init parse_early_param(void);
352 void __init parse_early_options(char *cmdline);
353 #endif /* __ASSEMBLY__ */
354 
355 #else /* MODULE */
356 
357 #define __setup_param(str, unique_id, fn)       /* nothing */
358 #define __setup(str, func)                      /* nothing */
359 #endif
360 
361 /* Data marked not to be saved by software suspend */
362 #define __nosavedata __section(".data..nosave")
363 
364 #ifdef MODULE
365 #define __exit_p(x) x
366 #else
367 #define __exit_p(x) NULL
368 #endif
369 
370 #endif /* _LINUX_INIT_H */
371 

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