内核---数据类型所占空间

当Linux内核在体系结构差异较大的平台之间移植时，会产生与数据类型相关的问题。

.在编译内核时使用 -Wall  -W strict-prototypes 选项, 可以避免很多错误的发生

.内核使用的基本数据类型主要有:
     int           标准C语言整数类型
     u32         32位整数类型
     pid_t       特定内核对象pid的类型

.在不同的CPU体系结构上，C语言的数据类型所占空间不一样。
 

arch	char	short	int	long	ptr	long-long	u8	u16	u32	u64
i686	1	2	4	4	4	8	1	2	4	8
i386	1	2	4	4	4	8	1	2	4	8
alpha	1	2	4	8	8	8	1	2	4	8
armv41	1	2	4	4	4	8	1	2	4	8
ia64	1	2	4	8	8	8	1	2	4	8
m68k	1	2	4	4	4	8	1	2	4	8
mips	1	2	4	4	4	8	1	2	4	8
ppc	1	2	4	4	4	8	1	2	4	8
sparc	1	2	4	4	4	8	1	2	4	8
sparc64	1	2	4	4	4	8	1	2	4	8

.内核中的地址是unsigned long类型， 指针大小和long类型相同

.内核提供下列数据类型， 所有类型在头文件中声明， 这个文件又被头文件所包含， 下面是 include/asm/typs.h文件

[File] /usr/src/kernels/2.6.9-22.EL-i686/include/asm-i386/types.h


#ifndef _I386_TYPES_H
#define _I386_TYPES_H

#ifndef __ASSEMBLY__

typedef unsigned short umode_t;

/*
 * __xx is ok: it doesn't pollute the POSIX namespace. Use these in the
 * header files exported to user space
 */

typedef __signed__ char __s8;
typedef unsigned char __u8;

typedef __signed__ short __s16;
typedef unsigned short __u16;

typedef __signed__ int __s32;
typedef unsigned int __u32;

#if defined(__GNUC__) && !defined(__STRICT_ANSI__)
typedef __signed__ long long __s64;
typedef unsigned long long __u64;
#endif

#endif /* __ASSEMBLY__ */

/*
 * These aren't exported outside the kernel to avoid name space clashes
 */
#ifdef __KERNEL__

#define BITS_PER_LONG 32

#ifndef __ASSEMBLY__

#include

typedef signed char s8;
typedef unsigned char u8;

typedef signed short s16;
typedef unsigned short u16;

typedef signed int s32;
typedef unsigned int u32;

typedef signed long long s64;
typedef unsigned long long u64;

/* DMA addresses come in generic and 64-bit flavours.  */

#ifdef CONFIG_HIGHMEM64G
typedef u64 dma_addr_t;
#else
typedef u32 dma_addr_t;
#endif
typedef u64 dma64_addr_t;

#ifdef CONFIG_LBD
typedef u64 sector_t;
#define HAVE_SECTOR_T
#endif

typedef unsigned short kmem_bufctl_t;

#endif /* __ASSEMBLY__ */

#endif /* __KERNEL__ */

#endif


[File] /usr/src/kernels/2.6.9-22.EL-i686/include/linux/types.h

#ifndef _LINUX_TYPES_H
#define _LINUX_TYPES_H

#ifdef    __KERNEL__
#include

#define BITS_TO_LONGS(bits) \
    (((bits)+BITS_PER_LONG-1)/BITS_PER_LONG)
#define DECLARE_BITMAP(name,bits) \
    unsigned long name[BITS_TO_LONGS(bits)]
#endif

#include
#include

#ifndef __KERNEL_STRICT_NAMES

typedef __u32 __kernel_dev_t;

typedef __kernel_fd_set        fd_set;
typedef __kernel_dev_t        dev_t;
typedef __kernel_ino_t        ino_t;
typedef __kernel_mode_t        mode_t;
typedef __kernel_nlink_t    nlink_t;
typedef __kernel_off_t        off_t;
typedef __kernel_pid_t        pid_t;
typedef __kernel_daddr_t    daddr_t;
typedef __kernel_key_t        key_t;
typedef __kernel_suseconds_t    suseconds_t;
typedef __kernel_timer_t    timer_t;
typedef __kernel_clockid_t    clockid_t;
typedef __kernel_mqd_t        mqd_t;

#ifdef __KERNEL__
typedef __kernel_uid32_t    uid_t;
typedef __kernel_gid32_t    gid_t;
typedef __kernel_uid16_t        uid16_t;
typedef __kernel_gid16_t        gid16_t;

#ifdef CONFIG_UID16
/* This is defined by include/asm-{arch}/posix_types.h */
typedef __kernel_old_uid_t    old_uid_t;
typedef __kernel_old_gid_t    old_gid_t;
#endif /* CONFIG_UID16 */

/* libc5 includes this file to define uid_t, thus uid_t can never change
 * when it is included by non-kernel code
 */
#else
typedef __kernel_uid_t        uid_t;
typedef __kernel_gid_t        gid_t;
#endif /* __KERNEL__ */

#if defined(__GNUC__) && !defined(__STRICT_ANSI__)
typedef __kernel_loff_t        loff_t;
#endif

/*
 * The following typedefs are also protected by individual ifdefs for
 * historical reasons:
 */
#ifndef _SIZE_T
#define _SIZE_T
typedef __kernel_size_t        size_t;
#endif

#ifndef _SSIZE_T
#define _SSIZE_T
typedef __kernel_ssize_t    ssize_t;
#endif

#ifndef _PTRDIFF_T
#define _PTRDIFF_T
typedef __kernel_ptrdiff_t    ptrdiff_t;
#endif

#ifndef _TIME_T
#define _TIME_T
typedef __kernel_time_t        time_t;
#endif

#ifndef _CLOCK_T
#define _CLOCK_T
typedef __kernel_clock_t    clock_t;
#endif

#ifndef _CADDR_T
#define _CADDR_T
typedef __kernel_caddr_t    caddr_t;
#endif

/* bsd */
typedef unsigned char        u_char;
typedef unsigned short        u_short;
typedef unsigned int        u_int;
typedef unsigned long        u_long;

/* sysv */
typedef unsigned char        unchar;
typedef unsigned short        ushort;
typedef unsigned int        uint;
typedef unsigned long        ulong;

#ifndef __BIT_TYPES_DEFINED__
#define __BIT_TYPES_DEFINED__

typedef        __u8        u_int8_t;
typedef        __s8        int8_t;
typedef        __u16        u_int16_t;
typedef        __s16        int16_t;
typedef        __u32        u_int32_t;
typedef        __s32        int32_t;

#endif /* !(__BIT_TYPES_DEFINED__) */

typedef        __u8        uint8_t;
typedef        __u16        uint16_t;
typedef        __u32        uint32_t;

#if defined(__GNUC__) && !defined(__STRICT_ANSI__)
typedef        __u64        uint64_t;
typedef        __u64        u_int64_t;
typedef        __s64        int64_t;
#endif

/*
 * The type used for indexing onto a disc or disc partition.
 * If required, asm/types.h can override it and define
 * HAVE_SECTOR_T
 */
#ifndef HAVE_SECTOR_T
typedef unsigned long sector_t;
#endif

/*
 * The type of an index into the pagecache.  Use a #define so asm/types.h
 * can override it.
 */
#ifndef pgoff_t
#define pgoff_t unsigned long
#endif

#ifdef __CHECKER__
#define __bitwise __attribute__((bitwise))
#else
#define __bitwise
#endif

typedef __u16 __bitwise __le16;
typedef __u16 __bitwise __be16;
typedef __u32 __bitwise __le32;
typedef __u32 __bitwise __be32;
typedef __u64 __bitwise __le64;
typedef __u64 __bitwise __be64;

#endif /* __KERNEL_STRICT_NAMES */

/*
 * Below are truly Linux-specific types that should never collide with
 * any application/library that wants linux/types.h.
 */

struct ustat {
    __kernel_daddr_t    f_tfree;
    __kernel_ino_t        f_tinode;
    char                         f_fname[6];
    char                         f_fpack[6];
};

#endif /* _LINUX_TYPES_H */