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.

Execution Environment

The copyin kernel service can be called from the process environment only.

Return Values

Item	Description
0	Indicates a successful operation.
EFAULT	Indicates that the user has insufficient authority to access the data, or the address specified in the uaddr parameter is not valid.
EIO	Indicates that a permanent I/O error occurred while referencing data.
ENOMEM	Indicates insufficient memory for the required paging operation.
ENOSPC	Indicates insufficient file system or paging space.