linux内核的数据类型 转载

转自songlinux.cublog.cn

对linux内核的数据类型做一下总结。

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 -Wstrict-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：

ØØ int          标准C语言整数类型；

ØØ u32          32位整数类型；

ØØ 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。下面是在x86下数据类型所占的字节数：

arch	char	short	int	long	ptr	long-long	u8	u16	u32	u64
i686	1	2	4	4	4	8	1	2	4	8

下面是在其他平台上的数据类型所占的字节数：

arch	char	short	int	long	ptr	long-long	u8	u16	u32	u64
i386	1	2	4	4	4	8	1	2	4	8
alpha	1	2	4	8	8	8	1	2	4	8
armv4l	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

其中基于sparc64平台的Linux用户空间可以运行32位代码，用户空间指针是32位宽的，但内核空间是64位的。

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/types.h文件。这是对ARM体系结构中 /asm/types.h文件中的一些定义： 因为我是对arm体系结构进行了配置

#ifndef __ASM_ARM_TYPES_H
#define __ASM_ARM_TYPES_H


 /*
  * This file is never included by application software unless
  * explicitly requested (e.g., via linux/types.h) in which case the
  * application is Linux specific so (user-) name space pollution is
  * not a major issue.  However, for interoperability, libraries still
  * need to be careful to avoid a name clashes.
  */

#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__

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 are 32-bits wide. */

typedef u32 dma_addr_t;
typedef u32 dma64_addr_t;

#endif /* __ASSEMBLY__ */

#endif /* __KERNEL__ */

#endif



 

使用有前缀的类型用于将变量显露给用户空间，如_ _u8类型。例如：一个驱动程序通过ioctl函数与运行在用户空间的程序交换数据，应该用_ _u32来声明32位的数据类型。

有时内核使用C语言的类型，如unsigned int，这通常用于大小独立于体系结构的数据项。 内核中许多数据类型由typedef声明，这样方便移植。如使用pid_t类型作为进程标志符（pid）的类型，而不是int类型，pid_t屏蔽了在不同平台上的实际数据类型的差异。

如果不容易选择合适的类型，就将其强制转换成最可能的类型（long或unsigned long）。

如上面所说，在中又把你所配置的体系结构中定义的类型的类型定义

包含进去了：下面把这个文件贴出来，我的内核版本是2.6.16.28。

 

#ifndef _LINUX_TYPES_H
#define _LINUX_TYPES_H

#ifdef    __KERNEL__
#include <linux/config.h>

#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)]

#define BITS_PER_BYTE 8
#endif

#include <linux/posix_types.h>
#include <asm/types.h>

#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

/* this is a special 64bit data type that is 8-byte aligned */
#define aligned_u64 unsigned long long __attribute__((aligned(8)))

/*
 * 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

#endif /* __KERNEL_STRICT_NAMES */

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

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

typedef __u16 __bitwise __le16;
typedef __u16 __bitwise __be16;
typedef __u32 __bitwise __le32;
typedef __u32 __bitwise __be32;
#if defined(__GNUC__) && !defined(__STRICT_ANSI__)
typedef __u64 __bitwise __le64;
typedef __u64 __bitwise __be64;
#endif

#ifdef __KERNEL__
typedef unsigned __bitwise__ gfp_t;
#endif

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

#endif /* _LINUX_TYPES_H */


 

这里面我以可以看到一些自定义类型，如loff_t,size_t等。

typedef __kernel_uid_t        uid_t;
typedef __kernel_gid_t        gid_t;

typedef __kernel_loff_t        loff_t;

这样就将loff_t类型定义为__kernel_loff_t这个类型 了,uid_t类型定义了__kernel_uid_t类型了，但是现在__kernel_loff_t __kernel_uid_t这种类型是很明显地与体系结构是相关的，对于arm的体系结构，则定义在,代码如下：

 

/*
 * linux/include/asm-arm/posix_types.h
 *
 * Copyright (C) 1996-1998 Russell King.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Changelog:
 * 27-06-1996    RMK    Created
 */
#ifndef __ARCH_ARM_POSIX_TYPES_H
#define __ARCH_ARM_POSIX_TYPES_H

/*
 * This file is generally used by user-level software, so you need to
 * be a little careful about namespace pollution etc. Also, we cannot
 * assume GCC is being used.
 */

typedef unsigned long        __kernel_ino_t;
typedef unsigned short        __kernel_mode_t;
typedef unsigned short        __kernel_nlink_t;
typedef long            __kernel_off_t;
typedef int            __kernel_pid_t;
typedef unsigned short        __kernel_ipc_pid_t;
typedef unsigned short        __kernel_uid_t;
typedef unsigned short        __kernel_gid_t;
typedef unsigned int        __kernel_size_t;
typedef int            __kernel_ssize_t;
typedef int            __kernel_ptrdiff_t;
typedef long            __kernel_time_t;
typedef long            __kernel_suseconds_t;
typedef long            __kernel_clock_t;
typedef int            __kernel_timer_t;
typedef int            __kernel_clockid_t;
typedef int            __kernel_daddr_t;
typedef char *            __kernel_caddr_t;
typedef unsigned short        __kernel_uid16_t;
typedef unsigned short        __kernel_gid16_t;
typedef unsigned int        __kernel_uid32_t;
typedef unsigned int        __kernel_gid32_t;

typedef unsigned short        __kernel_old_uid_t;
typedef unsigned short        __kernel_old_gid_t;
typedef unsigned short        __kernel_old_dev_t;

#ifdef __GNUC__
typedef long long        __kernel_loff_t;
#endif

typedef struct {
#if defined(__KERNEL__) || defined(__USE_ALL)
    int    val[2];
#else /* !defined(__KERNEL__) && !defined(__USE_ALL) */
    int    __val[2];
#endif /* !defined(__KERNEL__) && !defined(__USE_ALL) */
} __kernel_fsid_t;

#if defined(__KERNEL__) || !defined(__GLIBC__) || (__GLIBC__ < 2)

#undef    __FD_SET
#define __FD_SET(fd, fdsetp) \
        (((fd_set *)(fdsetp))->fds_bits[(fd) >> 5] |= (1<<((fd) & 31)))

#undef    __FD_CLR
#define __FD_CLR(fd, fdsetp) \
        (((fd_set *)(fdsetp))->fds_bits[(fd) >> 5] &= ~(1<<((fd) & 31)))

#undef    __FD_ISSET
#define __FD_ISSET(fd, fdsetp) \
        ((((fd_set *)(fdsetp))->fds_bits[(fd) >> 5] & (1<<((fd) & 31))) != 0)

#undef    __FD_ZERO
#define __FD_ZERO(fdsetp) \
        (memset (fdsetp, 0, sizeof (*(fd_set *)(fdsetp))))

#endif

#endif


 

现在，你看起内核的一些函数的参数的类型为loff_t，ssize_t这些类型就不会发怵了吧！呵呵。

不过我也发现了一个非常不错网站，你可以把linux 的一个参数或者数据类型输入进去，便可查询内部相关数据类型。