第十五章 Linux核心数据结构
本章列出了Linux实用的主要数据结构。
block_dev_struct
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; /* Mcast mac addrs */
int mc_count; /* No installed mcasts */
struct ip_mc_list *ip_mc_list; /* IP mcast 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理解的二进制文件格式。
struct linux_binfmt {
struct linux_binfmt * next;
long *use_count;
int (*load_binary)(struct linux_binprm *, struct pt_regs * regs);
int (*load_shlib)(int fd);
int (*core_dump)(long signr, struct pt_regs * regs);
};
mem_map_t
用来保存每个物理页面的信息。
typedef struct page {
/* these must be first (free area handling) */
struct page *next;
struct page *prev;
struct inode *inode;
unsigned long offset;
struct page *next_hash;
atomic_t count;
unsigned flags; /* atomic flags, some possibly
updated asynchronously */
unsigned dirty:16,
age:8;
struct wait_queue *wait;
struct page *prev_hash;
struct buffer_head *buffers;
unsigned long swap_unlock_entry;
unsigned long map_nr; /* page->map_nr == page - mem_map */
} mem_map_t;
mm_struct
用来描叙某任务或进程的虚拟内存。
struct mm_struct {
int count;
pgd_t * pgd;
unsigned long context;
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack, start_mmap;
unsigned long arg_start, arg_end, env_start, env_end;
unsigned long rss, total_vm, locked_vm;
unsigned long def_flags;
struct vm_area_struct * mmap;
struct vm_area_struct * mmap_avl;
struct semaphore mmap_sem;
};
pci_bus
表示系统中的一个PCI总线。
struct pci_bus {
struct pci_bus *parent; /* parent bus this bridge is on */
struct pci_bus *children; /* chain of P2P bridges on this bus */
struct pci_bus *next; /* chain of all PCI buses */
struct pci_dev *self; /* bridge device as seen by parent */
struct pci_dev *devices; /* devices behind this bridge */
void *sysdata; /* hook for sys-specific extension */
unsigned char number; /* bus number */
unsigned char primary; /* number of primary bridge */
unsigned char secondary; /* number of secondary bridge */
unsigned char subordinate; /* max number of subordinate buses */
};
pci_dev
表示系统中的每个PCI设备，包括PCI-PCI和PCI-PCI桥接器。
/*
* There is one pci_dev structure for each slot-number/function-number
* combination:
*/
struct pci_dev {
struct pci_bus *bus; /* bus this device is on */
struct pci_dev *sibling; /* next device on this bus */
struct pci_dev *next; /* chain of all devices */
void *sysdata; /* hook for sys-specific extension */
unsigned int devfn; /* encoded device & function index */
unsigned short vendor;
unsigned short device;
unsigned int class; /* 3 bytes: (base,sub,prog-if) */
unsigned int master : 1; /* set if device is master capable */
/*
* In theory, the irq level can be read from configuration
* space and all would be fine. However, old PCI chips dont
* support these registers and return 0 instead. For example,
* the Vision864-P rev 0 chip can uses INTA, but returns 0 in
* the interrupt line and pin registers. pci_init()
* initializes this field with the value at PCI_INTERRUPT_LINE
* and it is the job of pcibios_fixup() to change it if
* necessary. The field must not be 0 unless the device
* cannot generate interrupts at all.
*/
unsigned char irq; /* irq generated by this device */
};
request
被用来向系统的块设备发送请求。它总是向buffer cache读出或写入数据块。
struct request {
volatile int rq_status;
#define RQ_INACTIVE (-1)
#define RQ_ACTIVE 1
#define RQ_SCSI_BUSY 0xffff
#define RQ_SCSI_DONE 0xfffe
#define RQ_SCSI_DISCONNECTING 0xffe0
kdev_t rq_dev;
int cmd; /* READ or WRITE */
int errors;
unsigned long sector;
unsigned long nr_sectors;
unsigned long current_nr_sectors;
char * buffer;
struct semaphore * sem;
struct buffer_head * bh;
struct buffer_head * bhtail;
struct request * next;
};
rtable
用来描叙向某个IP主机发送包的路由信息。此结构在IP路由cache内部实用。
struct rtable
{
struct rtable *rt_next;
__u32 rt_dst;
__u32 rt_src;
__u32 rt_gateway;
atomic_t rt_refcnt;
atomic_t rt_use;
unsigned long rt_window;
atomic_t rt_lastuse;
struct hh_cache *rt_hh;
struct device *rt_dev;
unsigned short rt_flags;
unsigned short rt_mtu;
unsigned short rt_irtt;
unsigned char rt_tos;
};
semaphore
保护临界区数据结构和代码信号灯。
struct semaphore {
int count;
int waking;
int lock ; /* to make waking testing atomic */
struct wait_queue *wait;
};
sk_buff
用来描叙在协议层之间交换的网络数据。
struct sk_buff
{
struct sk_buff *next; /* Next buffer in list
*/
struct sk_buff *prev; /* Previous buffer in list
*/
struct sk_buff_head *list; /* List we are on
*/
int magic_debug_cookie;
struct sk_buff *link3; /* Link for IP protocol level buffer chai
ns *
struct sock *sk; /* Socket we are owned by
*/
unsigned long when; /* used to compute rtts
*/
struct timeval stamp; /* Time we arrived
*/
struct device *dev; /* Device we arrived on/are leaving by
*/
union
{
struct tcphdr *th;
struct ethhdr *eth;
struct iphdr *iph;
struct udphdr *uh;
unsigned char *raw;
/* for passing file handles in a unix domain socket */
void *filp;
} h;
union
{
/* As yet incomplete physical layer views */
unsigned char *raw;
struct ethhdr *ethernet;
} mac;
struct iphdr *ip_hdr; /* For IPPROTO_RAW
*/
unsigned long len; /* Length of actual data
*/
unsigned long csum; /* Checksum
*/
__u32 saddr; /* IP source address
*/
__u32 daddr; /* IP target address
*/
__u32 raddr; /* IP next hop address
*/
__u32 seq; /* TCP sequence number
*/
__u32 end_seq; /* seq [+ fin] [+ syn] + datalen
*/
__u32 ack_seq; /* TCP ack sequence number
*/
unsigned char proto_priv[16];
volatile char acked, /* Are we acked ?
*/
used, /* Are we in use ?
*/
free, /* How to free this buffer
*/
arp; /* Has IP/ARP resolution finished
*/
unsigned char tries, /* Times tried
*/
lock, /* Are we locked ?
*/
localroute, /* Local routing asserted for this frame
*/
pkt_type, /* Packet class
*/
pkt_bridged, /* Tracker for bridging
*/
ip_summed; /* Driver fed us an IP checksum
*/
#define PACKET_HOST 0 /* To us
*/
#define PACKET_BROADCAST 1 /* To all
*/
#define PACKET_MULTICAST 2 /* To group
*/
#define PACKET_OTHERHOST 3 /* To someone else
*/
unsigned short users; /* User count - see datagram.c,tcp.c
*/
unsigned short protocol; /* Packet protocol from driver.
*/
unsigned int truesize; /* Buffer size
*/
atomic_t count; /* reference count
*/
struct sk_buff *data_skb; /* Link to the actual data skb
*/
unsigned char *head; /* Head of buffer
*/
unsigned char *data; /* Data head pointer
*/
unsigned char *tail; /* Tail pointer
*/
unsigned char *end; /* End pointer
*/
void (*destructor)(struct sk_buff *); /* Destruct function
*/
__u16 redirport; /* Redirect port
*/
};
sock
包含BSD套接口的协议相关信息。例如对于一个INET（Internet AddressDomain）套接口
此数据结构 包含TCP/IP和UDP/IP信息。
struct sock
{
/* This must be first. */
struct sock *sklist_next;
struct sock *sklist_prev;
struct options *opt;
atomic_t wmem_alloc;
atomic_t rmem_alloc;
unsigned long allocation; /* Allocation mode */
__u32 write_seq;
__u32 sent_seq;
__u32 acked_seq;
__u32 copied_seq;
__u32 rcv_ack_seq;
unsigned short rcv_ack_cnt; /* count of same ack */
__u32 window_seq;
__u32 fin_seq;
__u32 urg_seq;
__u32 urg_data;
__u32 syn_seq;
int users; /* user count */
/*
* Not all are volatile, but some are, so we
* might as well say they all are.
*/
volatile char dead,
urginline,
intr,
blog,
done,
reuse,
keepopen,
linger,
delay_acks,
destroy,
ack_timed,
no_check,
zapped,
broadcast,
nonagle,
bsdism;
unsigned long lingertime;
int proc;
struct sock *next;
struct sock **pprev;
struct sock *bind_next;
struct sock **bind_pprev;
struct sock *pair;
int hashent;
struct sock *prev;
struct sk_buff *volatile send_head;
struct sk_buff *volatile send_next;
struct sk_buff *volatile send_tail;
struct sk_buff_head back_log;
struct sk_buff *partial;
struct timer_list partial_timer;
long retransmits;
struct sk_buff_head write_queue,
receive_queue;
struct proto *prot;
struct wait_queue **sleep;
__u32 daddr;
__u32 saddr; /* Sending source */
__u32 rcv_saddr; /* Bound address */
unsigned short max_unacked;
unsigned short window;
__u32 lastwin_seq; /* sequence number when we las
t
updated the window we offer
*/
__u32 high_seq; /* sequence number when we did
current fast retransmit */
volatile unsigned long ato; /* ack timeout */
volatile unsigned long lrcvtime; /* jiffies at last data rcv */