1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>__copy_to_user</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="The Linux Kernel API"><link rel="up" href="ch04s02.html" title="User Space Memory Access"><link rel="prev" href="API---copy-to-user-inatomic.html" title="__copy_to_user_inatomic"><link rel="next" href="API---copy-from-user.html" title="__copy_from_user"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">__copy_to_user</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API---copy-to-user-inatomic.html">Prev</a>&#160;</td><th width="60%" align="center">User Space Memory Access</th><td width="20%" align="right">&#160;<a accesskey="n" href="API---copy-from-user.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API---copy-to-user"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>__copy_to_user &#8212; 
2     Copy a block of data into user space, with less checking.
3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">unsigned long <b class="fsfunc">__copy_to_user </b>(</code></td><td>void __user * <var class="pdparam">to</var>, </td></tr><tr><td>&#160;</td><td>const void * <var class="pdparam">from</var>, </td></tr><tr><td>&#160;</td><td>unsigned long <var class="pdparam">n</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1123905588"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>to</code></em></span></dt><dd><p>
4     Destination address, in user space.
5    </p></dd><dt><span class="term"><em class="parameter"><code>from</code></em></span></dt><dd><p>
6     Source address, in kernel space.
7    </p></dd><dt><span class="term"><em class="parameter"><code>n</code></em></span></dt><dd><p>
8     Number of bytes to copy.
9    </p></dd></dl></div></div><div class="refsect1"><a name="idp1123909244"></a><h2>Context</h2><p>
10   User context only.  This function may sleep.
11</p></div><div class="refsect1"><a name="idp1123909892"></a><h2>Description</h2><p>
12   Copy data from kernel space to user space.  Caller must check
13   the specified block with <code class="function">access_ok</code> before calling this function.
14   </p><p>
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16   Returns number of bytes that could not be copied.
17   On success, this will be zero.
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