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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Tue, 14 Aug 2012 11:47:07 +0000 (UTC)
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Subject: svn commit: r239247 - head/sys/vm
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Author: kib
Date: Tue Aug 14 11:47:07 2012
New Revision: 239247
URL: http://svn.freebsd.org/changeset/base/239247

Log:
  Adjust the r205536, by allowing a non-zero offset for anonymous
  mappings for a.out binaries. Apparently, a.out ld.so from FreeBSD
  1.1.5.1 can issue such requests.
  
  Reported and tested by:	Dan Plassche <dplassche@gmail.com>
  MFC after:	1 week

Modified:
  head/sys/vm/vm_mmap.c

Modified: head/sys/vm/vm_mmap.c
==============================================================================
--- head/sys/vm/vm_mmap.c	Tue Aug 14 11:45:47 2012	(r239246)
+++ head/sys/vm/vm_mmap.c	Tue Aug 14 11:47:07 2012	(r239247)
@@ -207,11 +207,23 @@ sys_mmap(td, uap)
 
 	fp = NULL;
 
-	/* Make sure mapping fits into numeric range, etc. */
-	if ((uap->len == 0 && !SV_CURPROC_FLAG(SV_AOUT) &&
-	     curproc->p_osrel >= P_OSREL_MAP_ANON) ||
-	    ((flags & MAP_ANON) && (uap->fd != -1 || pos != 0)))
-		return (EINVAL);
+	/*
+	 * Enforce the constraints.
+	 * Mapping of length 0 is only allowed for old binaries.
+	 * Anonymous mapping shall specify -1 as filedescriptor and
+	 * zero position for new code. Be nice to ancient a.out
+	 * binaries and correct pos for anonymous mapping, since old
+	 * ld.so sometimes issues anonymous map requests with non-zero
+	 * pos.
+	 */
+	if (!SV_CURPROC_FLAG(SV_AOUT)) {
+		if ((uap->len == 0 && curproc->p_osrel >= P_OSREL_MAP_ANON) ||
+		    ((flags & MAP_ANON) != 0 && (uap->fd != -1 || pos != 0)))
+			return (EINVAL);
+	} else {
+		if ((flags & MAP_ANON) != 0)
+			pos = 0;
+	}
 
 	if (flags & MAP_STACK) {
 		if ((uap->fd != -1) ||