init.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_INIT_H
  3#define _LINUX_INIT_H
  4
  5#include <linux/build_bug.h>
  6#include <linux/compiler.h>
  7#include <linux/stringify.h>
  8#include <linux/types.h>
  9
 10/* These macros are used to mark some functions or 
 11 * initialized data (doesn't apply to uninitialized data)
 12 * as `initialization' functions. The kernel can take this
 13 * as hint that the function is used only during the initialization
 14 * phase and free up used memory resources after
 15 *
 16 * Usage:
 17 * For functions:
 18 * 
 19 * You should add __init immediately before the function name, like:
 20 *
 21 * static void __init initme(int x, int y)
 22 * {
 23 *    extern int z; z = x * y;
 24 * }
 25 *
 26 * If the function has a prototype somewhere, you can also add
 27 * __init between closing brace of the prototype and semicolon:
 28 *
 29 * extern int initialize_foobar_device(int, int, int) __init;
 30 *
 31 * For initialized data:
 32 * You should insert __initdata or __initconst between the variable name
 33 * and equal sign followed by value, e.g.:
 34 *
 35 * static int init_variable __initdata = 0;
 36 * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };
 37 *
 38 * Don't forget to initialize data not at file scope, i.e. within a function,
 39 * as gcc otherwise puts the data into the bss section and not into the init
 40 * section.
 41 */
 42
 43/* These are for everybody (although not all archs will actually
 44   discard it in modules) */
 45#define __init		__section(".init.text") __cold __latent_entropy	\
 46						__no_kstack_erase
 47#define __initdata	__section(".init.data")
 48#define __initconst	__section(".init.rodata")
 49#define __exitdata	__section(".exit.data")
 50#define __exit_call	__used __section(".exitcall.exit")
 51
 52/*
 53 * modpost check for section mismatches during the kernel build.
 54 * A section mismatch happens when there are references from a
 55 * code or data section to an init section (both code or data).
 56 * The init sections are (for most archs) discarded by the kernel
 57 * when early init has completed so all such references are potential bugs.
 58 * For exit sections the same issue exists.
 59 *
 60 * The following markers are used for the cases where the reference to
 61 * the *init / *exit section (code or data) is valid and will teach
 62 * modpost not to issue a warning.  Intended semantics is that a code or
 63 * data tagged __ref* can reference code or data from init section without
 64 * producing a warning (of course, no warning does not mean code is
 65 * correct, so optimally document why the __ref is needed and why it's OK).
 66 *
 67 * The markers follow same syntax rules as __init / __initdata.
 68 */
 69#define __ref            __section(".ref.text") noinline
 70#define __refdata        __section(".ref.data")
 71#define __refconst       __section(".ref.rodata")
 72
 73#ifdef MODULE
 74#define __exitused
 75#else
 76#define __exitused  __used
 77#endif
 78
 79#define __exit          __section(".exit.text") __exitused __cold notrace
 80
 81#ifdef CONFIG_MEMORY_HOTPLUG
 82#define __meminit
 83#define __meminitdata
 84#define __meminitconst
 85#else
 86#define __meminit	__init
 87#define __meminitdata	__initdata
 88#define __meminitconst	__initconst
 89#endif
 90
 91/* For assembly routines */
 92#define __HEAD		.section	".head.text","ax"
 93#define __INIT		.section	".init.text","ax"
 94#define __FINIT		.previous
 95
 96#define __INITDATA	.section	".init.data","aw",%progbits
 97#define __INITRODATA	.section	".init.rodata","a",%progbits
 98#define __FINITDATA	.previous
 99
100/* silence warnings when references are OK */
101#define __REF            .section       ".ref.text", "ax"
102#define __REFDATA        .section       ".ref.data", "aw"
103#define __REFCONST       .section       ".ref.rodata", "a"
104
105#ifndef __ASSEMBLY__
106/*
107 * Used for initialization calls..
108 */
109typedef int (*initcall_t)(void);
110typedef void (*exitcall_t)(void);
111
112#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
113typedef int initcall_entry_t;
114
115static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
116{
117	return offset_to_ptr(entry);
118}
119#else
120typedef initcall_t initcall_entry_t;
121
122static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
123{
124	return *entry;
125}
126#endif
127
128extern initcall_entry_t __con_initcall_start[], __con_initcall_end[];
129
130/* Used for constructor calls. */
131typedef void (*ctor_fn_t)(void);
132
133struct file_system_type;
134
135/* Defined in init/main.c */
136extern int do_one_initcall(initcall_t fn);
137extern char __initdata boot_command_line[];
138extern char *saved_command_line;
139extern unsigned int saved_command_line_len;
140extern unsigned int reset_devices;
141
142/* used by init/main.c */
143void setup_arch(char **);
144void prepare_namespace(void);
145void __init init_rootfs(void);
146
147void init_IRQ(void);
148void time_init(void);
149void poking_init(void);
150void pgtable_cache_init(void);
151
152extern initcall_entry_t __initcall_start[];
153extern initcall_entry_t __initcall0_start[];
154extern initcall_entry_t __initcall1_start[];
155extern initcall_entry_t __initcall2_start[];
156extern initcall_entry_t __initcall3_start[];
157extern initcall_entry_t __initcall4_start[];
158extern initcall_entry_t __initcall5_start[];
159extern initcall_entry_t __initcall6_start[];
160extern initcall_entry_t __initcall7_start[];
161extern initcall_entry_t __initcall_end[];
162
163extern struct file_system_type rootfs_fs_type;
164
165extern bool rodata_enabled;
166void mark_rodata_ro(void);
167
168extern void (*late_time_init)(void);
169
170extern bool initcall_debug;
171
172#ifdef MODULE
173extern struct module __this_module;
174#define THIS_MODULE (&__this_module)
175#else
176#define THIS_MODULE ((struct module *)0)
177#endif
178
179#endif
180  
181#ifndef MODULE
182
183#ifndef __ASSEMBLY__
184
185/*
186 * initcalls are now grouped by functionality into separate
187 * subsections. Ordering inside the subsections is determined
188 * by link order. 
189 * For backwards compatibility, initcall() puts the call in 
190 * the device init subsection.
191 *
192 * The `id' arg to __define_initcall() is needed so that multiple initcalls
193 * can point at the same handler without causing duplicate-symbol build errors.
194 *
195 * Initcalls are run by placing pointers in initcall sections that the
196 * kernel iterates at runtime. The linker can do dead code / data elimination
197 * and remove that completely, so the initcall sections have to be marked
198 * as KEEP() in the linker script.
199 */
200
201/* Format: <modname>__<counter>_<line>_<fn> */
202#define __initcall_id(fn)					\
203	__PASTE(kmod_,						\
204	__PASTE(__KBUILD_MODNAME,				\
205	__PASTE(__,						\
206	__PASTE(__COUNTER__,					\
207	__PASTE(_,						\
208	__PASTE(__LINE__,					\
209	__PASTE(_, fn)))))))
210
211/* Format: __<prefix>__<iid><id> */
212#define __initcall_name(prefix, __iid, id)			\
213	__PASTE(__,						\
214	__PASTE(prefix,						\
215	__PASTE(__,						\
216	__PASTE(__iid, id))))
217
218#ifdef CONFIG_LTO_CLANG
219/*
220 * With LTO, the compiler doesn't necessarily obey link order for
221 * initcalls. In order to preserve the correct order, we add each
222 * variable into its own section and generate a linker script (in
223 * scripts/link-vmlinux.sh) to specify the order of the sections.
224 */
225#define __initcall_section(__sec, __iid)			\
226	#__sec ".init.." #__iid
227
228/*
229 * With LTO, the compiler can rename static functions to avoid
230 * global naming collisions. We use a global stub function for
231 * initcalls to create a stable symbol name whose address can be
232 * taken in inline assembly when PREL32 relocations are used.
233 */
234#define __initcall_stub(fn, __iid, id)				\
235	__initcall_name(initstub, __iid, id)
236
237#define __define_initcall_stub(__stub, fn)			\
238	int __init __stub(void);				\
239	int __init __stub(void)					\
240	{ 							\
241		return fn();					\
242	}							\
243	__ADDRESSABLE(__stub)
244#else
245#define __initcall_section(__sec, __iid)			\
246	#__sec ".init"
247
248#define __initcall_stub(fn, __iid, id)	fn
249
250#define __define_initcall_stub(__stub, fn)			\
251	__ADDRESSABLE(fn)
252#endif
253
254#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
255#define ____define_initcall(fn, __stub, __name, __sec)		\
256	__define_initcall_stub(__stub, fn)			\
257	asm(".section	\"" __sec "\", \"a\"		\n"	\
258	    __stringify(__name) ":			\n"	\
259	    ".long	" __stringify(__stub) " - .	\n"	\
260	    ".previous					\n");	\
261	static_assert(__same_type(initcall_t, &fn));
262#else
263#define ____define_initcall(fn, __unused, __name, __sec)	\
264	static initcall_t __name __used 			\
265		__attribute__((__section__(__sec))) = fn;
266#endif
267
268#define __unique_initcall(fn, id, __sec, __iid)			\
269	____define_initcall(fn,					\
270		__initcall_stub(fn, __iid, id),			\
271		__initcall_name(initcall, __iid, id),		\
272		__initcall_section(__sec, __iid))
273
274#define ___define_initcall(fn, id, __sec)			\
275	__unique_initcall(fn, id, __sec, __initcall_id(fn))
276
277#define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
278
279/*
280 * Early initcalls run before initializing SMP.
281 *
282 * Only for built-in code, not modules.
283 */
284#define early_initcall(fn)		__define_initcall(fn, early)
285
286/*
287 * A "pure" initcall has no dependencies on anything else, and purely
288 * initializes variables that couldn't be statically initialized.
289 *
290 * This only exists for built-in code, not for modules.
291 * Keep main.c:initcall_level_names[] in sync.
292 */
293#define pure_initcall(fn)		__define_initcall(fn, 0)
294
295#define core_initcall(fn)		__define_initcall(fn, 1)
296#define core_initcall_sync(fn)		__define_initcall(fn, 1s)
297#define postcore_initcall(fn)		__define_initcall(fn, 2)
298#define postcore_initcall_sync(fn)	__define_initcall(fn, 2s)
299#define arch_initcall(fn)		__define_initcall(fn, 3)
300#define arch_initcall_sync(fn)		__define_initcall(fn, 3s)
301#define subsys_initcall(fn)		__define_initcall(fn, 4)
302#define subsys_initcall_sync(fn)	__define_initcall(fn, 4s)
303#define fs_initcall(fn)			__define_initcall(fn, 5)
304#define fs_initcall_sync(fn)		__define_initcall(fn, 5s)
305#define rootfs_initcall(fn)		__define_initcall(fn, rootfs)
306#define device_initcall(fn)		__define_initcall(fn, 6)
307#define device_initcall_sync(fn)	__define_initcall(fn, 6s)
308#define late_initcall(fn)		__define_initcall(fn, 7)
309#define late_initcall_sync(fn)		__define_initcall(fn, 7s)
310
311#define __initcall(fn) device_initcall(fn)
312
313#define __exitcall(fn)						\
314	static exitcall_t __exitcall_##fn __exit_call = fn
315
316#define console_initcall(fn)	___define_initcall(fn, con, .con_initcall)
317
318struct obs_kernel_param {
319	const char *str;
320	int (*setup_func)(char *);
321	int early;
322};
323
324extern const struct obs_kernel_param __setup_start[], __setup_end[];
325
326/*
327 * Only for really core code.  See moduleparam.h for the normal way.
328 *
329 * Force the alignment so the compiler doesn't space elements of the
330 * obs_kernel_param "array" too far apart in .init.setup.
331 */
332#define __setup_param(str, unique_id, fn, early)			\
333	static const char __setup_str_##unique_id[] __initconst		\
334		__aligned(1) = str; 					\
335	static struct obs_kernel_param __setup_##unique_id		\
336		__used __section(".init.setup")				\
337		__aligned(__alignof__(struct obs_kernel_param))		\
338		= { __setup_str_##unique_id, fn, early }
339
340/*
341 * NOTE: __setup functions return values:
342 * @fn returns 1 (or non-zero) if the option argument is "handled"
343 * and returns 0 if the option argument is "not handled".
344 */
345#define __setup(str, fn)						\
346	__setup_param(str, fn, fn, 0)
347
348/*
349 * NOTE: @fn is as per module_param, not __setup!
350 * I.e., @fn returns 0 for no error or non-zero for error
351 * (possibly @fn returns a -errno value, but it does not matter).
352 * Emits warning if @fn returns non-zero.
353 */
354#define early_param(str, fn)						\
355	__setup_param(str, fn, fn, 1)
356
357#define early_param_on_off(str_on, str_off, var, config)		\
358									\
359	int var = IS_ENABLED(config);					\
360									\
361	static int __init parse_##var##_on(char *arg)			\
362	{								\
363		var = 1;						\
364		return 0;						\
365	}								\
366	early_param(str_on, parse_##var##_on);				\
367									\
368	static int __init parse_##var##_off(char *arg)			\
369	{								\
370		var = 0;						\
371		return 0;						\
372	}								\
373	early_param(str_off, parse_##var##_off)
374
375/* Relies on boot_command_line being set */
376void __init parse_early_param(void);
377void __init parse_early_options(char *cmdline);
378#endif /* __ASSEMBLY__ */
379
380#else /* MODULE */
381
382#define __setup_param(str, unique_id, fn)	/* nothing */
383#define __setup(str, func) 			/* nothing */
384#endif
385
386/* Data marked not to be saved by software suspend */
387#define __nosavedata __section(".data..nosave")
388
389#ifdef MODULE
390#define __exit_p(x) x
391#else
392#define __exit_p(x) NULL
393#endif
394
395#endif /* _LINUX_INIT_H */