---
name: "__copy_to_user"
section: "9"
platform: "linux"
package: "linux-manual-4.9"
version: "4.9.228-1"
release: "Debian 9 (Stretch)"
platforms: ["linux"]
url: "https://new.carta.tech/__copy_to_user"
---

# \_\_copy\_to\_user(9)

Copy a block of data into user space, with less checking.

## NAME

\_\_copy\_to\_user - Copy a block of data into user space, with less checking.

## SYNOPSIS

**unsigned long \_\_copy\_to\_user(void \_\_user \*** *to***, const void \*** *from***, unsigned long** *n***);**

## ARGUMENTS

*to*

Destination address, in user space.

*from*

Source address, in kernel space.

*n*

Number of bytes to copy.

## CONTEXT

User context only. This function may sleep if pagefaults are enabled.

## DESCRIPTION

Copy data from kernel space to user space. Caller must check the specified block with **access\_ok** before calling this function.

Returns number of bytes that could not be copied. On success, this will be zero.

## COPYRIGHT