copyin函数

详见：http://pic.dhe.ibm.com/infocenter/aix/v6r1/index.jsp?topic=%2Fcom.ibm.aix.kerneltechref%2Fdoc%2Fktechrf1%2Fcopyin.htm

copyin Kernel Service

Purpose

Copies data between user and kernel memory.

Syntax

#include <sys/types.h>
#include <sys/errno.h>

int copyin ( uaddr,  kaddr,  count)
char *uaddr;
char *kaddr;
int count;

Parameters

Item	Description
uaddr	Specifies the address of user data.
kaddr	Specifies the address of kernel data.
count	Specifies the number of bytes to copy.

Description

The copyin kernel service copies the specified
number of bytes from user memory to kernel memory. This service is
provided so that system calls and device driver top half routines
can safely access user data. The copyin service ensures that
the user has the appropriate authority to access the data. It also
provides recovery from paging I/O errors that would otherwise cause
the system to crash. The copyin service
should be called only while executing in kernel mode in the user process.