linux内核的数据类型总结

本文载自网络，备用！对linux内核的数据类型做一下总结。下面部分内容参考了：http://book.csdn.net/bookfiles/12/100126.shtml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：?? 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。下面是在x86下数据类型所占的字节数：archcharshortintlongptrlong-longu8u16u32u64i6861244481248下面是在其他平台上的数据类型所占的字节数：archcharshortintlongptrlong-longu8u16u32u64i3861244481248alpha1248881248armv4l1244481248ia641248881248m68k1244481248mips1244481248ppc1244481248sparc1244481248sparc641244481248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<include/asm/types.h>中声明，这个文件又被头文件<Linux/types.h>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de>#ifndef __ASM_ARM_TYPES_H#define __ASM_ARM_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__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__ */#endifde> 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<include/linux/types.h>中又把你所配置的体系结构中定义的类型的类型定义<include/asm /types.h>包含进去了：下面把<include/linux/types.h>这个文件贴出来，我的内核版本是 2.6.16.28。 de>#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_NAMEStypedef __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 */#elsetypedef __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_Ttypedef __kernel_size_t size_t;#endif#ifndef _SSIZE_T#define _SSIZE_Ttypedef __kernel_ssize_t ssize_t;#endif#ifndef _PTRDIFF_T#define _PTRDIFF_Ttypedef __kernel_ptrdiff_t ptrdiff_t;#endif#ifndef _TIME_T#define _TIME_Ttypedef __kernel_time_t time_t;#endif#ifndef _CLOCK_T#define _CLOCK_Ttypedef __kernel_clock_t clock_t;#endif#ifndef _CADDR_T#define _CADDR_Ttypedef __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_Ttypedef 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#endiftypedef __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;#endifstruct ustat { __kernel_daddr_t f_tfree; __kernel_ino_t f_tinode; char f_fname[6]; char f_fpack[6];};#endif /* _LINUX_TYPES_H */de> 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<include/asm-arm /posix_types.h>,代码如下：