什么是linux核心数据结构??
发布网友
发布时间：2022-03-17 01:42
共2个回答
热心网友
时间：2022-03-17 03:12
2.3.1 连接列表
Linux使用的许多软件工程的技术来连接它的数据结构。在许多场合下，它使用linked或者chained数据结构。 每个数据结构描叙某一事物，比如某个进程或网络设备，核心必须能够访问到所有这些结构。在链表结构中，个根节点指针包含第一个结构的地址，而在每个结构中又包含表中下一个结构的指针。表的最后一项必须是0或者NULL，以表明这是表的尾部。在双向链表中，每个结构包含着指向表中前一结构和后一结构的指针。使用双向链表的好处在于更容易在表的中部添加与删除节点，但需要更多的内存操作。这是一种典型的操作系统开销与CPU循环之间的折中。
2.3.2 散列表
链表用来连接数据结构比较方便，但链表的操作效率不高。如果要搜寻某个特定内容，我们可能不得不遍历整个链表。Linux使用另外一种技术:散列表来提高效率。散列表是指针的数组或向量，指向内存中连续的相邻数据集合。散列表中每个指针元素指向一个独立链表。如果你使用数据结构来描叙村子里的人，则你可以使用年龄作为索引。为了找到某个人的数据，可以在人口散列表中使用年龄作为索引，找到包含此人特定数据的数据结构。但是在村子里有很多人的年龄相同，这样散列表指针变成了一个指向具有相同年龄的人数据链表的指针。搜索这个小链表的速度显然要比搜索整个数据链表快得多。 由于散列表加快了对数据结构的访问速度，Linux经常使用它来实现Caches。Caches是保存经常访问的信息的子集。经常被核心使用的数据结构将被放入Cache中保存。Caches的缺点是比使用和维护单一链表和散列表更复杂。寻找某个数据结构时，如果在Cache中能够找到（这种情况称为cache 命中），这的确很不错。但是如果没有找到，则必须找出它，并且添加到Cache中去。如果Cache空间已经用完则Linux必须决定哪一个结构将从其中抛弃，但是有可能这个要抛弃的数据就是Linux下次要使用的数据。
2.3.3 抽象接口
Linux核心常将其接口抽象出来。接口指一组以特定方式执行的子程序和数据结构的集合。例如，所有的网络设备驱动必须提供对某些特定数据结构进行操作的子程序。通用代码可能会使用底层的某些代码。例如网络层代码是通用的，它得到遵循标准接口的特定设备相关代码的支持。 通常在系统启动时，底层接口向更高层接口注册(Register)自身。这些注册操作包括向链表中加入结构节点。例如，构造进核心的每个文件系统在系统启动时将其自身向核心注册。文件/proc/filesysems中可以看到已经向核心注册过的文件系统。注册数据结构通常包括指向函数的指针，以文件系统注册为例，它向Linux核心注册时必须将那些mount文件系统连接时使用的一些相关函数的地址传入。
参考资料：http://net.fstc.cn/personal/liming/index.asp
热心网友
时间：2022-03-17 04:30
http://www.hlib.cn/article/os/186.asp
此结构用于向核心登记块设备，它还被buffer cache实用。所有此类结构都位于blk_dev数组中。
Struct blk_dev_struct {
void (*request_fn)(void);
struct request * current_request;
struct request plug;
struct tq_struct plug_tq;
};
buffer_head
此结构包含关于buffer cache中一块缓存的信息。
/* bh state bits */
#define BH_Uptodate 0 /* 1 if the buffer contains valid data */
#define BH_Dirty 1 /* 1 if the buffer is dirty */
#define BH_Lock 2 /* 1 if the buffer is locked */
#define BH_Req 3 /* 0 if the buffer has been invalidated */
#define BH_Touched 4 /* 1 if the buffer has been touched (aging) */
#define BH_Has_aged 5 /* 1 if the buffer has been aged (aging) */
#define BH_Protected 6 /* 1 if the buffer is protected */
#define BH_FreeOnIO 7 /* 1 to discard the buffer_head after IO */
struct buffer_head {
/* First cache line: */
unsigned long b_blocknr; /* block number */
kdev_t b_dev; /* device (B_FREE = free) */
kdev_t b_rdev; /* Real device */
unsigned long b_rsector; /* Real buffer location on disk */
struct buffer_head *b_next; /* Hash queue list */
struct buffer_head *b_this_page; /* circular list of buffers in one
page */
/* Second cache line: */
unsigned long b_state; /* buffer state bitmap (above) */
struct buffer_head *b_next_free;
unsigned int b_count; /* users using this block */
unsigned long b_size; /* block size */
/* Non-performance-critical data follows. */
char *b_data; /* pointer to data block */
unsigned int b_list; /* List that this buffer appears */
unsigned long b_flushtime; /* Time when this (dirty) buffer
* should be written */
unsigned long b_lru_time; /* Time when this buffer was
* last used. */
struct wait_queue *b_wait;
struct buffer_head *b_prev; /* doubly linked hash list */
struct buffer_head *b_prev_free; /* doubly linked list of buffers */
struct buffer_head *b_reqnext; /* request queue */
};
device
系统中每个网络设备都用一个设备数据结构来表示。
Struct device
{
/*
* This is the first field of the visible part of this structure
* (I.e. as seen by users in the Space.c file). It is the name
* the interface.
*/
char *name;
/* I/O specific fields */
unsigned long rmem_end; /* shmem recv end */
unsigned long rmem_start; /* shmem recv start */
unsigned long mem_end; /* shared mem end */
unsigned long mem_start; /* shared mem start */
unsigned long base_addr; /* device I/O address */
unsigned char irq; /* device IRQ number */
/* Low-level status flags. */
volatile unsigned char start, /* start an operation */
interrupt; /* interrupt arrived */
unsigned long tbusy; /* transmitter busy */
struct device *next;
/* The device initialization function. Called only once. */
int (*init)(struct device *dev);
/* Some hardware also needs these fields, but they are not part of
the usual set specified in Space.c. */
unsigned char if_port; /* Selectable AUI,TP, */
unsigned char dma; /* DMA channel */
struct enet_statistics* (*get_stats)(struct device *dev);
/*
* This marks the end of the visible part of the structure. All
* fields hereafter are internal to the system, and may change at
* will (read: may be cleaned up at will).
*/
/* These may be needed for future network-power-down code. */
unsigned long trans_start; /* Time (jiffies) of last transmit */
unsigned long last_rx; /* Time of last Rx */
unsigned short flags; /* interface flags (BSD)*/
unsigned short family; /* address family ID */
unsigned short metric; /* routing metric */
unsigned short mtu; /* MTU value */
unsigned short type; /* hardware type */
unsigned short hard_header_len; /* hardware hdr len */
void *priv; /* private data */
/* Interface address info. */
unsigned char broadcast[MAX_ADDR_LEN];
unsigned char pad;
unsigned char dev_addr[MAX_ADDR_LEN];
unsigned char addr_len; /* hardware addr len */
unsigned long pa_addr; /* protocol address */
unsigned long pa_brdaddr; /* protocol broadcast addr*/
unsigned long pa_dstaddr; /* protocol P-P other addr*/
unsigned long pa_mask; /* protocol netmask */
unsigned short pa_alen; /* protocol address len */
struct dev_mc_list *mc_list; /* M'cast mac addrs */
int mc_count; /* No installed mcasts */
struct ip_mc_list *ip_mc_list; /* IP m'cast filter chain */
__u32 tx_queue_len; /* Max frames per queue */
/* For load balancing driver pair support */
unsigned long pkt_queue; /* Packets queued */
struct device *slave; /* Slave device */
struct net_alias_info *alias_info; /* main dev alias info */
struct net_alias *my_alias; /* alias devs */
/* Pointer to the interface buffers. */
struct sk_buff_head buffs[DEV_NUMBUFFS];
/* Pointers to interface service routines. */
int (*open)(struct device *dev);
int (*stop)(struct device *dev);
int (*hard_start_xmit) (struct sk_buff *skb,
struct device *dev);
int (*hard_header) (struct sk_buff *skb,
struct device *dev,
unsigned short type,
void *daddr,
void *saddr,
unsigned len);
int (*rebuild_header)(void *eth,
struct device *dev,
unsigned long raddr,
struct sk_buff *skb);
void (*set_multicast_list)(struct device *dev);
int (*set_mac_address)(struct device *dev,
void *addr);
int (*do_ioctl)(struct device *dev,
struct ifreq *ifr,
int cmd);
int (*set_config)(struct device *dev,
struct ifmap *map);
void (*header_cache_bind)(struct hh_cache **hhp,
struct device *dev,
unsigned short htype,
__u32 daddr);
void (*header_cache_update)(struct hh_cache *hh,
struct device *dev,
unsigned char * haddr);
int (*change_mtu)(struct device *dev,
int new_mtu);
struct iw_statistics* (*get_wireless_stats)(struct device *dev);
};
device_struct
此结构被块设备和字符设备用来向核心登记（包含设备名称以及可对此设备进行的文件操作）。Chrdevs和blkdevs中的每个有效分别表示一个字符设备和块设备。
Struct device_struct {
const char * name;
struct file_operations * fops;
};
file
每个打开的文件、套接口都用此结构表示。
Struct file {
mode_t f_mode;
loff_t f_pos;
unsigned short f_flags;
unsigned short f_count;
unsigned long f_reada, f_ramax, f_raend, f_ralen, f_rawin;
struct file *f_next, *f_prev;
int f_owner; /* pid or -pgrp where SIGIO should be sent */
struct inode * f_inode;
struct file_operations * f_op;
unsigned long f_version;
void *private_data; /* needed for tty driver, and maybe others */
};
files_struct
描叙被某进程打开的所有文件。
Struct files_struct {
int count;
fd_set close_on_exec;
fd_set open_fds;
struct file * fd[NR_OPEN];
};
fs_struct
struct fs_struct {
int count;
unsigned short umask;
struct inode * root, * pwd;
};
gendisk
包含关于某个硬盘的信息。用于磁盘初始化与分区检查时。
Struct hd_struct {
long start_sect;
long nr_sects;
};
struct gendisk {
int major; /* major number of driver */
const char *major_name; /* name of major driver */
int minor_shift; /* number of times minor is shifted to get real minor */
int max_p; /* maximum partitions per device */
int max_nr; /* maximum number of real devices */
void (*init)(struct gendisk *);
/* Initialization called before we do our thing */
struct hd_struct *part; /* partition table */
int *sizes; /* device size in blocks, copied to blk_size[] */
int nr_real; /* number of real devices */
void *real_devices; /* internal use */
struct gendisk *next;
};
inode
此VFS inode结构描叙磁盘上一个文件或目录的信息。
Struct inode {
kdev_t I_dev;
unsigned long I_ino;
umode_t I_mode;
nlink_t I_nlink;
uid_t I_uid;
gid_t I_gid;
kdev_t I_rdev;
off_t I_size;
time_t I_atime;
time_t I_mtime;
time_t I_ctime;
unsigned long I_blksize;
unsigned long I_blocks;
unsigned long I_version;
unsigned long I_nrpages;
struct semaphore I_sem;
struct inode_operations *I_op;
struct super_block *I_sb;
struct wait_queue *I_wait;
struct file_lock *I_flock;
struct vm_area_struct *I_mmap;
struct page *I_pages;
struct dquot *I_dquot[MAXQUOTAS];
struct inode *I_next, *I_prev;
struct inode *I_hash_next, *I_hash_prev;
struct inode *I_bound_to, *I_bound_by;
struct inode *I_mount;
unsigned short I_count;
unsigned short I_flags;
unsigned char I_lock;
unsigned char I_dirt;
unsigned char I_pipe;
unsigned char I_sock;
unsigned char I_seek;
unsigned char I_update;
unsigned short I_writecount;
union {
struct pipe_inode_info pipe_I;
struct minix_inode_info minix_I;
struct ext_inode_info ext_I;
struct ext2_inode_info ext2_I;
struct hpfs_inode_info hpfs_I;
struct msdos_inode_info msdos_I;
struct umsdos_inode_info umsdos_I;
struct iso_inode_info isofs_I;
struct nfs_inode_info nfs_I;
struct xiafs_inode_info xiafs_I;
struct sysv_inode_info sysv_I;
struct affs_inode_info affs_I;
struct ufs_inode_info ufs_I;
struct socket socket_I;
void *generic_ip;
} u;
};
ipc_perm
此结构描叙对一个系统V IPC对象的存取权限。
Struct ipc_perm
{
key_t key;
ushort uid; /* owner euid and egid */
ushort gid;
ushort cuid; /* creator euid and egid */
ushort cgid;
ushort mode; /* access modes see mode flags below */
ushort seq; /* sequence number */
};
irqaction
用来描叙系统的中断处理过程。
Struct irqaction {
void (*handler)(int, void *, struct pt_regs *);
unsigned long flags;
unsigned long mask;
const char *name;
void *dev_id;
struct irqaction *next;
};
linux_binfmt
用来表示可被Linux理解的二进
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