Linux内核网络协议栈2－socket从库函数到内核

2、socket()调用如下：

1)socket()->__socket()：glibc-2.3.6/sysdept/generic/socket.c(weak_alias(name1,name2))

2)__socket()：glibc-2.3.6/sysdept/unix/sysv/linux/i386/socket.S

3)ENTER_KERNEL：

movl $SYS_ify(socketcall), %eax	/* System call number in %eax.  */

/* Use ## so `socket' is a separate token that might be #define'd.  */
movl $P(SOCKOP_,socket), %ebx	/* Subcode is first arg to syscall.  */
lea 4(%esp), %ecx		/* Address of args is 2nd arg.  */

        /* Do the system call trap.  */
ENTER_KERNEL

#define SYS_ify(syscall_name)	__NR_##syscall_name；

#define P(a, b) P2(a, b)
#define P2(a, b) a##b

#define __NR_socketcall		102

#define SOCKOP_socket		1

# define ENTER_KERNEL int $0x80

syscall_call:
	call *sys_call_table(,%eax,4)

6)进入中断向量表：kernel/arch/x86/kernel/syscall_table_32.S中的102号中断：

.long sys_socketcall

7)进入sys_socketcall()函数，根据子中断号以决定走哪个分支：kernel/net/Socket.c：

switch (call) {
	case SYS_SOCKET:
		break;
	case SYS_BIND:
		…...

二、socket其他库函数(bind,accept...)

1、对于其他库函数，都是引用上面提到的glibc-2.3.6/sysdept/unix/sysv/linux/i386/socket.S来实现的，如

a)bind.S：

#define	socket	bind
#define	NARGS	3
#define NO_WEAK_ALIAS	1
#include <socket.S>
weak_alias (bind, __bind)