LKML: Jeff Garzik: Re: [PATCH] Reduce stack usage in time.c

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <!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=UTF-8" /><title>LKML: Jeff Garzik: Re: [PATCH] Reduce stack usage in time.c</title><link href="/css/message.css" rel="stylesheet" type="text/css" /><link href="/css/wrap.css" rel="alternate stylesheet" type="text/css" title="wrap" /><link href="/css/nowrap.css" rel="stylesheet" type="text/css" title="nowrap" /><link href="/favicon.ico" rel="shortcut icon" /><script src="/js/simple-calendar.js" type="text/javascript"></script><script src="/js/styleswitcher.js" type="text/javascript"></script><link rel="alternate" type="application/rss+xml" title="lkml.org : last 100 messages" href="/rss.php" /><link rel="alternate" type="application/rss+xml" title="lkml.org : last messages by Jeff Garzik" href="/groupie.php?aid=46" /><script> var _paq = window._paq = window._paq || []; /* tracker methods like "setCustomDimension" should be called before "trackPageView" */ _paq.push(["setDoNotTrack", true]); _paq.push(["disableCookies"]); _paq.push(['trackPageView']); _paq.push(['enableLinkTracking']); (function() { var u="//m.lkml.org/"; _paq.push(['setTrackerUrl', u+'matomo.php']); _paq.push(['setSiteId', '1']); var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0]; g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s); })(); </script></head><body onload="es.jasper.simpleCalendar.init();" itemscope="itemscope" itemtype="http://schema.org/BlogPosting"><table border="0" cellpadding="0" cellspacing="0"><tr><td width="180" align="center"><a href="/"><img style="border:0;width:135px;height:32px" src="/images/toprowlk.gif" alt="lkml.org" /></a></td><td width="32">聽</td><td class="nb"><div><a class="nb" href="/lkml"> [lkml]</a> 聽 <a class="nb" href="/lkml/2005"> [2005]</a> 聽 <a class="nb" href="/lkml/2005/3"> [Mar]</a> 聽 <a class="nb" href="/lkml/2005/3/31"> [31]</a> 聽 <a class="nb" href="/lkml/last100"> [last100]</a> 聽 <a href="/rss.php"><img src="/images/rss-or.gif" border="0" alt="RSS Feed" /></a></div><div>Views: <a href="#" class="nowrap" onclick="setActiveStyleSheet('wrap');return false;">[wrap]</a><a href="#" class="wrap" onclick="setActiveStyleSheet('nowrap');return false;">[no wrap]</a> 聽 <a class="nb" href="/lkml/mheaders/2005/3/31/46" onclick="this.href='/lkml/headers'+'/2005/3/31/46';">[headers]</a>聽 <a href="/lkml/bounce/2005/3/31/46">[forward]</a>聽 </div></td><td width="32">聽</td></tr><tr><td valign="top"><div class="es-jasper-simpleCalendar" baseurl="/lkml/"></div><div class="threadlist">Messages in this thread</div><ul class="threadlist"><li class="root"><a href="/lkml/2005/3/31/36">First message in thread</a></li><li><a href="/lkml/2005/3/31/36">Yum Rayan</a><ul><li class="origin"><a href="/lkml/2005/3/31/63">Jeff Garzik</a><ul><li><a href="/lkml/2005/3/31/63">Denis Vlasenko</a><ul><li><a href="/lkml/2005/3/31/128">=?iso-8859-1?Q?J=F6rn?= Engel</a></li></ul></li></ul></li></ul></li></ul></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerl.gif" width="32" height="32" alt="/" /></td><td class="c" rowspan="2" valign="top" style="padding-top: 1em"><table><tr><td><table><tr><td class="lp">Date</td><td class="rp" itemprop="datePublished">Thu, 31 Mar 2005 03:26:43 -0500</td></tr><tr><td class="lp">From</td><td class="rp" itemprop="author">Jeff Garzik <></td></tr><tr><td class="lp">Subject</td><td class="rp" itemprop="name">Re: [PATCH] Reduce stack usage in time.c</td></tr></table></td><td></td></tr></table><pre itemprop="articleBody">Yum Rayan wrote:<br />> Attempt to reduce stack usage in time.c (linux-2.6.12-rc1-mm3). Stack<br />> usage was noted using checkstack.pl. Specifically:<br />> <br />> Before patch<br />> ------------<br />> sys_adjtimex - 128<br />> <br />> After patch<br />> -----------<br />> sys_adjtimex - none (register usage only)<br />> <br />> Signed-off-by: Yum Rayan <yum.rayan@gmail.com><br />> <br />> --- a/kernel/time.c 2005-03-25 22:11:06.000000000 -0800<br />> +++ b/kernel/time.c 2005-03-30 16:59:51.000000000 -0800<br />> @@ -413,17 +413,27 @@<br />> <br />> asmlinkage long sys_adjtimex(struct timex __user *txc_p)<br />> {<br />> - struct timex txc; /* Local copy of parameter */<br />> - int ret;<br />> + struct timex *txc; /* Local copy of parameter */<br />> + int retval;<br />> +<br />> + txc = kmalloc(sizeof(struct timex), GFP_KERNEL);<br />> + if (!txc)<br />> + return -ENOMEM;<br />> <br />> /* Copy the user data space into the kernel copy<br />> * structure. But bear in mind that the structures<br />> * may change<br />> */<br />> - if(copy_from_user(&txc, txc_p, sizeof(struct timex)))<br />> - return -EFAULT;<br />> - ret = do_adjtimex(&txc);<br />> - return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;<br />> + if(copy_from_user(txc, txc_p, sizeof(struct timex))) {<br />> + retval = -EFAULT;<br />> + goto free_txc;<br />> + }<br />> + retval = do_adjtimex(txc);<br />> + if (copy_to_user(txc_p, txc, sizeof(struct timex)))<br />> + retval = -EFAULT;<br />> +free_txc:<br /><br />It seems quite unhealthy to add a kmalloc(,GFP_KERNEL) allocation into a <br />time-sensitive function.<br /><br /> Jeff<br /><br /><br /><br />-<br />To unsubscribe from this list: send the line "unsubscribe linux-kernel" in<br />the body of a message to majordomo@vger.kernel.org<br />More majordomo info at <a href="http://vger.kernel.org/majordomo-info.html">http://vger.kernel.org/majordomo-info.html</a><br />Please read the FAQ at <a href="http://www.tux.org/lkml/">http://www.tux.org/lkml/</a><br /><br /></pre></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerr.gif" width="32" height="32" alt="\" /></td></tr><tr><td align="right" valign="bottom"> 聽 </td></tr><tr><td align="right" valign="bottom">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerl.gif" width="32" height="32" alt="\" /></td><td class="c">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerr.gif" width="32" height="32" alt="/" /></td></tr><tr><td align="right" valign="top" colspan="2"> 聽 </td><td class="lm">Last update: 2005-04-06 13:31 聽聽 [from the cache]<br />漏2003-2020 <a href="http://blog.jasper.es/"><span itemprop="editor">Jasper Spaans</span></a>|hosted at <a href="https://www.digitalocean.com/?refcode=9a8e99d24cf9">Digital Ocean</a> and my Meterkast|<a href="http://blog.jasper.es/categories.html#lkml-ref">Read the blog</a></td><td>聽</td></tr></table><script language="javascript" src="/js/styleswitcher.js" type="text/javascript"></script></body></html>

CINXE.COM

LKML: Jeff Garzik: Re: [PATCH] Reduce stack usage in time.c