copyout函数

copyout Kernel Service

 

Purpose

Copies data between user and kernel memory.

Syntax

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

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

Parameters

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

Description

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

The copyout service should be called only while executing in kernel mode in the user process.