1// include/vdso/bits.h
 2/* SPDX-License-Identifier: GPL-2.0 */
 3#ifndef __VDSO_BITS_H
 4#define __VDSO_BITS_H
 5
 6#include <vdso/const.h>
 7
 8#define BIT(nr)			(UL(1) << (nr))
 9
10#endif	/* __VDSO_BITS_H */

1void xxx(const char __user *buffer) {
2    char mode;
3    // 宏实现，mode直接传就好，不需要取地址，返回0就是成功，返回非0就是失败
4    // 从对应类型的用户空间指针取值赋值给内部变量，数组取第一个，非数组直接取值
5    // 只支持1、2、4、8个字节的特定类型，不支持字符串
6    if (get_user(mode, buffer)) return;
7    // do something
8}

 1// include/asm-generic/uaccess.h
 2#define __get_user(x, ptr)					\
 3({								\
 4	int __gu_err = -EFAULT;					\
 5	__chk_user_ptr(ptr);					\
 6	switch (sizeof(*(ptr))) {				\
 7	case 1: {						\
 8		unsigned char __x = 0;				\
 9		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
10					 ptr, &__x);		\
11		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
12		break;						\
13	};							\
14	case 2: {						\
15		unsigned short __x = 0;				\
16		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
17					 ptr, &__x);		\
18		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
19		break;						\
20	};							\
21	case 4: {						\
22		unsigned int __x = 0;				\
23		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
24					 ptr, &__x);		\
25		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
26		break;						\
27	};							\
28	case 8: {						\
29		unsigned long long __x = 0;			\
30		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
31					 ptr, &__x);		\
32		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
33		break;						\
34	};							\
35	default:						\
36		__get_user_bad();				\
37		break;						\
38	}							\
39	__gu_err;						\
40})
41
42#define get_user(x, ptr)					\
43({								\
44	const void __user *__p = (ptr);				\
45	might_fault();						\
46	access_ok(VERIFY_READ, __p, sizeof(*ptr)) ?		\
47		__get_user((x), (__typeof__(*(ptr)) __user *)__p) :\
48		((x) = (__typeof__(*(ptr)))0,-EFAULT);		\
49})
50
51#ifndef __get_user_fn
52static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)
53{
54	return unlikely(raw_copy_from_user(x, ptr, size)) ? -EFAULT : 0;
55}
56
57#define __get_user_fn(sz, u, k)	__get_user_fn(sz, u, k)
58
59#endif

1// include/linux/types.h
2typedef _Bool			bool;
3
4// include/linux/stddef.h
5enum {
6	false	= 0,
7	true	= 1
8};

1// include/linux/stddef.h
2#undef NULL
3#define NULL ((void *)0)

 1// include/linux/init.h
 2#define __init		__section(".init.text") __cold  __latent_entropy __noinitretpoline __nocfi
 3#define __initdata	__section(".init.data")
 4#define __initconst	__section(".init.rodata")
 5#define __exitdata	__section(".exit.data")
 6#define __exit_call	__used __section(".exitcall.exit")
 7...
 8#define __ref            __section(".ref.text") noinline
 9#define __refdata        __section(".ref.data")
10#define __refconst       __section(".ref.rodata")
11#define __exit          __section(".exit.text") __exitused __cold notrace
12...
13/* Used for MEMORY_HOTPLUG */
14#define __meminit        __section(".meminit.text") __cold notrace \
15						  __latent_entropy
16#define __meminitdata    __section(".meminit.data")
17#define __meminitconst   __section(".meminit.rodata")
18#define __memexit        __section(".memexit.text") __exitused __cold notrace
19#define __memexitdata    __section(".memexit.data")
20#define __memexitconst   __section(".memexit.rodata")

1// include/asm-generic/param.h
2# undef HZ
3# define HZ		CONFIG_HZ	/* Internal kernel timer frequency */