arch/um/include/init.h

#ifndef _LINUX_UML_INIT_H
#define _LINUX_UML_INIT_H

/* These macros are used to mark some functions or
 * initialized data (doesn't apply to uninitialized data)
 * as `initialization' functions. The kernel can take this
 * as hint that the function is used only during the initialization
 * phase and free up used memory resources after
 *
 * Usage:
 * For functions:
 *
 * You should add __init immediately before the function name, like:
 *
 * static void __init initme(int x, int y)
 * {
 *    extern int z; z = x * y;
 * }
 *
 * If the function has a prototype somewhere, you can also add
 * __init between closing brace of the prototype and semicolon:
 *
 * extern int initialize_foobar_device(int, int, int) __init;
 *
 * For initialized data:
 * You should insert __initdata between the variable name and equal
 * sign followed by value, e.g.:
 *
 * static int init_variable __initdata = 0;
 * static char linux_logo[] __initdata = { 0x32, 0x36, ... };
 *
 * Don't forget to initialize data not at file scope, i.e. within a function,
 * as gcc otherwise puts the data into the bss section and not into the init
 * section.
 *
 * Also note, that this data cannot be "const".
 */

#ifndef _LINUX_INIT_H
typedef int (*initcall_t)(void);
typedef void (*exitcall_t)(void);

#ifndef __KERNEL__
#ifndef __section
# define __section(S) __attribute__ ((__section__(#S)))
#endif

#if __GNUC__ == 3

#if __GNUC_MINOR__ >= 3
# define __used			__attribute__((__used__))
#else
# define __used			__attribute__((__unused__))
#endif

#else
#if __GNUC__ == 4
# define __used			__attribute__((__used__))
#endif
#endif

#else
#include <linux/compiler.h>
#endif
/* These are for everybody (although not all archs will actually
   discard it in modules) */
#define __init		__section(.init.text)
#define __initdata	__section(.init.data)
#define __exitdata	__section(.exit.data)
#define __exit_call	__used __section(.exitcall.exit)

#ifdef MODULE
#define __exit		__section(.exit.text)
#else
#define __exit		__used __section(.exit.text)
#endif

#endif

#ifndef MODULE
struct uml_param {
        const char *str;
        int (*setup_func)(char *, int *);
};

extern initcall_t __uml_initcall_start, __uml_initcall_end;
extern initcall_t __uml_postsetup_start, __uml_postsetup_end;
extern const char *__uml_help_start, *__uml_help_end;
#endif

#define __uml_initcall(fn)					  	\
	static initcall_t __uml_initcall_##fn __uml_init_call = fn

#define __uml_exitcall(fn)						\
	static exitcall_t __uml_exitcall_##fn __uml_exit_call = fn

extern struct uml_param __uml_setup_start, __uml_setup_end;

#define __uml_postsetup(fn)						\
	static initcall_t __uml_postsetup_##fn __uml_postsetup_call = fn

#define __non_empty_string(dummyname,string)				\
	struct __uml_non_empty_string_struct_##dummyname		\
	{								\
		char _string[sizeof(string)-2];				\
	}

#ifndef MODULE
#define __uml_setup(str, fn, help...)					\
	__non_empty_string(fn ##_setup, str);				\
	__uml_help(fn, help);						\
	static char __uml_setup_str_##fn[] __initdata = str;		\
	static struct uml_param __uml_setup_##fn __uml_init_setup = { __uml_setup_str_##fn, fn }
#else
#define __uml_setup(str, fn, help...)					\

#endif

#define __uml_help(fn, help...)						\
	__non_empty_string(fn ##__help, help);				\
	static char __uml_help_str_##fn[] __initdata = help;		\
	static const char *__uml_help_##fn __uml_setup_help = __uml_help_str_##fn

/*
 * Mark functions and data as being only used at initialization
 * or exit time.
 */
#define __uml_init_setup	__used __section(.uml.setup.init)
#define __uml_setup_help	__used __section(.uml.help.init)
#define __uml_init_call		__used __section(.uml.initcall.init)
#define __uml_postsetup_call	__used __section(.uml.postsetup.init)
#define __uml_exit_call		__used __section(.uml.exitcall.exit)

#ifndef __KERNEL__

#define __define_initcall(level,fn) \
	static initcall_t __initcall_##fn __used \
	__attribute__((__section__(".initcall" level ".init"))) = fn

/* Userspace initcalls shouldn't depend on anything in the kernel, so we'll
 * make them run first.
 */
#define __initcall(fn) __define_initcall("1", fn)

#define __exitcall(fn) static exitcall_t __exitcall_##fn __exit_call = fn

#define __init_call	__used __section(.initcall.init)

#endif

#endif /* _LINUX_UML_INIT_H */