linux常用数据类型

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我是靠谱客的博主烂漫网络，最近开发中收集的这篇文章主要介绍linux常用数据类型，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

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<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

#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__ */ #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<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。

#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<include/asm-arm/posix_types.h>,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