<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>syscall_set_return_value</title><meta name="generator" content="DocBook XSL Stylesheets V1.76.1" /><link rel="home" href="index.html" title="The utrace User Debugging Infrastructure" /><link rel="up" href="syscall.html" title="System Call Tracing" /><link rel="prev" href="API-syscall-get-return-value.html" title="syscall_get_return_value" /><link rel="next" href="API-syscall-get-arguments.html" title="syscall_get_arguments" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>syscall_set_return_value</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-syscall-get-return-value.html">Prev</a> </td><th width="60%" align="center"><code class="filename">System Call Tracing</code></th><td width="20%" align="right"> <a accesskey="n" href="API-syscall-get-arguments.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="syscall_set_return_value"><a id="API-syscall-set-return-value"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>syscall_set_return_value — change the return value of a traced system call </p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <strong>fsfuncsyscall_set_return_value </strong>(</code></td><td>struct task_struct * <var class="pdparam">task</var>, </td></tr><tr><td> </td><td>struct pt_regs * <var class="pdparam">regs</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">error</var>, </td></tr><tr><td> </td><td>long <var class="pdparam">val</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2772859"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>task</code></em></span></dt><dd><p> task of interest, must be blocked </p></dd><dt><span class="term"><em class="parameter"><code>regs</code></em></span></dt><dd><p> <code class="function">task_pt_regs</code> of <em class="parameter"><code>task</code></em> </p></dd><dt><span class="term"><em class="parameter"><code>error</code></em></span></dt><dd><p> negative error code, or zero to indicate success </p></dd><dt><span class="term"><em class="parameter"><code>val</code></em></span></dt><dd><p> user return value if <em class="parameter"><code>error</code></em> is zero </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2772950"></a><h2>Description</h2><p> This changes the results of the system call that user mode will see. If <em class="parameter"><code>error</code></em> is zero, the user sees a successful system call with a return value of <em class="parameter"><code>val</code></em>. If <em class="parameter"><code>error</code></em> is nonzero, it's a negated errno code; the user sees a failed system call with this errno code. </p><p> It's only valid to call this when <em class="parameter"><code>task</code></em> is stopped for tracing on exit from a system call, due to <code class="constant">TIF_SYSCALL_TRACE</code> or <code class="constant">TIF_SYSCALL_AUDIT</code>. </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-syscall-get-return-value.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="syscall.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="API-syscall-get-arguments.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>syscall_get_return_value</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>syscall_get_arguments</span></td></tr></table></div></body></html>