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From: Brooks Davis <brooks@FreeBSD.org>
Date: Fri, 13 Jul 2018 11:32:27 +0000 (UTC)
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Subject: svn commit: r336238 - head/sys/kern
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Author: brooks
Date: Fri Jul 13 11:32:27 2018
New Revision: 336238
URL: https://svnweb.freebsd.org/changeset/base/336238

Log:
  Round down the location of execpathp to slightly improve copyout speed.
  
  In practice, this moves the padding from below the canary to above
  execpathp has no impact on stack consumption.
  
  Submitted by:		Wuyang-Chung (via github pull request #159)
  MFC after:	1 week

Modified:
  head/sys/kern/kern_exec.c

Modified: head/sys/kern/kern_exec.c
==============================================================================
--- head/sys/kern/kern_exec.c	Fri Jul 13 07:08:06 2018	(r336237)
+++ head/sys/kern/kern_exec.c	Fri Jul 13 11:32:27 2018	(r336238)
@@ -1512,6 +1512,7 @@ exec_copyout_strings(struct image_params *imgp)
 	 */
 	if (execpath_len != 0) {
 		destp -= execpath_len;
+		destp = rounddown2(destp, sizeof(void *));
 		imgp->execpathp = destp;
 		copyout(imgp->execpath, (void *)destp, execpath_len);
 	}