linux 驱动程序内核数据类型

小咪咪 2022-06-16 07:50 641阅读 0赞

内核的数据类型

基本数据类型

我们写了两个小的模块来测试实际数据类型和内存对齐的长度。

内核基本数据类型

C语言类型（int）

char、short、int、long long在不同的平台上大小不变。

long、ptr(指针)平台不同其大小不同，但二者的大小始终相同。

char的符号问题：

大多数平台上char默认是signed，但有些平台上默认是 unsigned。

char i = -1; 大部分平台上i是-1，有些平台上是255。

应该使用：signed char i = -1;   unsigned char i = 255;

确定大小的类型（u32）

u8、u16、u32、u64、 s8、s16、s32、s64是Linux内核确定大小的类型。

\_\_u8等式linux用户态确定大小的类型。（头文件linux/types.h）

uint8\_t、uint32\_t是新编译器支持的C99标准确定大小的类型，可以跨平台。

特定内核对象的类型（pid\_t）

进程标识符使用pid\_t类型，而不使用int，屏蔽了实际的数据类型中任何可能的差异。

特定内核对象的类型，打印时，不太好选择printk或printf的输出格式：

一些平台上排除的警告，在另一平台上可能会出现（size\_t在一些平台上是unsigned long，在一些平台上是unsigned int）。

将其强制转换成可能的最大类型，然后用响应的格式打印输出。

字节序   大端、小端   数值0x01020304，内存从低到高依次存储：04 03 02 01 为小端。 存储顺序反过来为大端）   数值0x00000001，内存从低到高依次存储：01 00 00 00 为小端。

转换函数   u32 \_\_cpu\_to\_be32(u32);    /\* 把cpu字节序转为大端字节序 \*/

u32 \_\_be32\_to\_cpu(u32);    /\* 把大端字节序转为cpu字节序 \*/

u32 \_\_cpu\_to\_le32(u32);      /\* 把cpu字节序转为小端字节序 \*/

u32 \_\_le32\_to\_cpu(u32);     /\* 把小端字节序转为cpu字节序 \*/

在头文件<linux/byteorder.h>中时间间隔使用HZ代表一秒。

不能假定每秒就1000个jiffies。   与msec毫秒对应的jiffies数目总是msec\*HZ/1000。

页大小为PAGE\_SIZE个字节，而不是4KB。

分配16KB的空间临时存储数据，如下：

以上，只是基本数据类型中最简单的一部分，绝大多数都是细节问题，要注意。

基本数据类型的长度

对齐数据类型长度

types.h 中的重要数据类型

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 unsigned short umode_t; 
    typedef __u32 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;   
    typedef _Bool bool;   
    typedef __kernel_uid32_t uid_t; 
    typedef __kernel_gid32_t gid_t; 
    typedef __kernel_uid16_t        
    uid16_t; typedef __kernel_gid16_t        gid16_t;  
    typedef unsigned long uintptr_t;   
    #ifdef CONFIG_HAVE_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 */  
    #if defined(__GNUC__) 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; t
    ypedef __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__) 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 __u64 __attribute__((aligned(8))) #define aligned_be64 __be64 __attribute__((aligned(8))) 
    
    #define aligned_le64 __le64 __attribute__((aligned(8)))   /** * The type used for indexing onto a disc or disc partition. * * Linux always considers sectors to be 512 bytes long independently * of the devices real block size. * * blkcnt_t is the type of the inode's block count. */ 
    #ifdef CONFIG_LBDAF 
    typedef u64 sector_t; 
    typedef u64 blkcnt_t; 
    #else typedef unsigned long sector_t; 
    typedef unsigned long blkcnt_t; 
    #endif   /* * The type of an index into the pagecache. */ #define pgoff_t unsigned long   /* * A dma_addr_t can hold any valid DMA address, i.e., any address returned * by the DMA API. * * If the DMA API only uses 32-bit addresses, dma_addr_t need only be 32 * bits wide.  Bus addresses, e.g., PCI BARs, may be wider than 32 bits, * but drivers do memory-mapped I/O to ioremapped kernel virtual addresses, * so they don't care about the size of the actual bus addresses. */ 
    #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT typedef u64 dma_addr_t; 
    #else typedef u32 dma_addr_t; 
    #endif   
    typedef unsigned __bitwise__ gfp_t; 
    typedef unsigned __bitwise__ fmode_t; 
    typedef unsigned __bitwise__ oom_flags_t;   
    #ifdef CONFIG_PHYS_ADDR_T_64BIT typedef u64 phys_addr_t; 
    #else typedef u32 phys_addr_t; 
    #endif   
    typedef phys_addr_t resource_size_t;   /* * This type is the placeholder for a hardware interrupt number. It has to be * big enough to enclose whatever representation is used by a given platform. */ 
    typedef unsigned long irq_hw_number_t;   
    typedef struct { int counter; } atomic_t;   
    #ifdef CONFIG_64BIT typedef struct { long counter; } atomic64_t; 
    #endif  
    struct list_head { struct list_head *next, *prev; };   
    struct hlist_head { struct hlist_node *first; };   
    struct hlist_node { struct hlist_node *next, **pprev; };   
    struct ustat { __kernel_daddr_t f_tfree; __kernel_ino_t f_tinode; char f_fname[6]; char f_fpack[6]; };  
    /** * struct callback_head - callback structure for use with RCU and task_work * @next: next update requests in a list * @func: actual update function to call after the grace period. * * The struct is aligned to size of pointer. On most architectures it happens * naturally due ABI requirements, but some architectures (like CRIS) have * weird ABI and we need to ask it explicitly. * * The alignment is required to guarantee that bits 0 and 1 of @next will be * clear under normal conditions -- as long as we use call_rcu(), * call_rcu_bh(), call_rcu_sched(), or call_srcu() to queue callback. * * This guarantee is important for few reasons: *  - future call_rcu_lazy() will make use of lower bits in the pointer; *  - the structure shares storage spacer in struct page with @compound_head, *  which encode PageTail() in bit 0. The guarantee is needed to avoid *    false-positive PageTail(). */ 
    struct callback_head { struct callback_head *next; void (*func)(struct callback_head *head); } 
    __attribute__((aligned(sizeof(void *)))); 
    #define rcu_head callback_head   typedef void (*rcu_callback_t)(struct rcu_head *head); typedef void (*call_rcu_func_t)(struct rcu_head *head, rcu_callback_t func);   
    /* clocksource cycle base type */ 
    typedef u64 cycle_t;