OS-3752 Increase IOV_MAX to at least 1024

12 files changed, 304 insertions, 95 deletions

diff --git a/manifest b/manifest
index 8b2ce2f682..0c909789a7 100644
--- a/manifest
+++ b/manifest
@@ -3861,6 +3861,7 @@ f usr/include/sys/lgrp.h 0644 root bin
 f usr/include/sys/lgrp_user.h 0644 root bin
 f usr/include/sys/libc_kernel.h 0644 root bin
 f usr/include/sys/libdevid.h 0644 root bin
+f usr/include/sys/limits.h 0644 root bin
 f usr/include/sys/link.h 0644 root bin
 f usr/include/sys/list.h 0644 root bin
 f usr/include/sys/list_impl.h 0644 root bin
diff --git a/usr/src/head/limits.h b/usr/src/head/limits.h
index a6cba76cf8..17aee19837 100644
--- a/usr/src/head/limits.h
+++ b/usr/src/head/limits.h
@@ -24,6 +24,7 @@
  *
  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright 2015 Joyent, Inc.  All rights reserved.
  */
 
 /*	Copyright (c) 1988 AT&T	*/
@@ -36,6 +37,7 @@
 #include <sys/feature_tests.h>
 #include <sys/isa_defs.h>
 #include <iso/limits_iso.h>
+#include <sys/limits.h>
 
 /*
  * Include fixed width type limits as proposed by the ISO/JTC1/SC22/WG14 C
@@ -237,8 +239,6 @@ extern "C" {
 #define	_XOPEN_NAME_MAX	255	/* max # bytes in filename excluding null */
 #define	_XOPEN_PATH_MAX	1024	/* max # bytes in a pathname */
 
-#define	IOV_MAX		_XOPEN_IOV_MAX
-
 #if defined(__EXTENSIONS__) || \
 	(!defined(_STRICT_STDC) && !defined(__XOPEN_OR_POSIX))
 
diff --git a/usr/src/lib/libbc/inc/include/sys/socket.h b/usr/src/lib/libbc/inc/include/sys/socket.h
index 03961f805b..6607721e62 100644
--- a/usr/src/lib/libbc/inc/include/sys/socket.h
+++ b/usr/src/lib/libbc/inc/include/sys/socket.h
@@ -3,8 +3,6 @@
  * Use is subject to license terms.
  */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 /*
  * Copyright (c) 1982, 1985, 1986 Regents of the University of California.
  * All rights reserved.  The Berkeley software License Agreement
@@ -169,6 +167,4 @@ struct msghdr {
 #define	MSG_PEEK	0x2		/* peek at incoming message */
 #define	MSG_DONTROUTE	0x4		/* send without using routing tables */
 
-#define	MSG_MAXIOVLEN	16
-
 #endif /*!_sys_socket_h*/
diff --git a/usr/src/uts/common/fs/sockfs/socksubr.c b/usr/src/uts/common/fs/sockfs/socksubr.c
index 06d76044e5..095d84fc42 100644
--- a/usr/src/uts/common/fs/sockfs/socksubr.c
+++ b/usr/src/uts/common/fs/sockfs/socksubr.c
@@ -21,6 +21,7 @@
 
 /*
  * Copyright (c) 1995, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2015, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/types.h>
@@ -1879,7 +1880,7 @@ ssize_t
 soreadfile(file_t *fp, uchar_t *buf, u_offset_t fileoff, int *err, size_t size)
 {
 	struct uio auio;
-	struct iovec aiov[MSG_MAXIOVLEN];
+	struct iovec aiov[1];
 	register vnode_t *vp;
 	int ioflag, rwflag;
 	ssize_t cnt;
diff --git a/usr/src/uts/common/fs/sockfs/socksyscalls.c b/usr/src/uts/common/fs/sockfs/socksyscalls.c
index e8aba2ad64..067eaedd7c 100644
--- a/usr/src/uts/common/fs/sockfs/socksyscalls.c
+++ b/usr/src/uts/common/fs/sockfs/socksyscalls.c
@@ -22,7 +22,7 @@
 /*
  * Copyright (c) 1995, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013, OmniTI Computer Consulting, Inc. All rights reserved.
- * Copyright (c) 2014, Joyent, Inc.  All rights reserved.
+ * Copyright 2015, Joyent, Inc.  All rights reserved.
  */
 
 #include <sys/types.h>
@@ -51,6 +51,7 @@
 #include <sys/cmn_err.h>
 #include <sys/vmsystm.h>
 #include <sys/policy.h>
+#include <sys/limits.h>
 
 #include <sys/socket.h>
 #include <sys/socketvar.h>
@@ -83,14 +84,6 @@ extern void	nl7c_init(void);
 extern int	sockfs_defer_nl7c_init;
 
 /*
- * For dated (and stupid) reasons, MSG_MAXIOVLEN is 16 -- but it's 1024 on most
- * other systems.  This becomes a problem when running binaries from these
- * other systems, and we therefore need to support an iov length of up to 1024,
- * regardless of the advertised constant for maximum length.
- */
-#define	MSG_MAXMAXIOVLEN	1024
-
-/*
  * Kernel component of socket creation.
  *
  * The socket library determines which version number to use.
@@ -1025,7 +1018,7 @@ recvmsg(int sock, struct nmsghdr *msg, int flags)
 	STRUCT_HANDLE(nmsghdr, umsgptr);
 	struct nmsghdr lmsg;
 	struct uio auio;
-	struct iovec buf[MSG_MAXIOVLEN], *aiov = buf;
+	struct iovec buf[IOV_MAX_STACK], *aiov = buf;
 	ssize_t iovsize = 0;
 	int iovcnt;
 	ssize_t len, rval;
@@ -1071,12 +1064,12 @@ recvmsg(int sock, struct nmsghdr *msg, int flags)
 
 	iovcnt = lmsg.msg_iovlen;
 
-	if (iovcnt <= 0 || iovcnt > MSG_MAXMAXIOVLEN) {
+	if (iovcnt <= 0 || iovcnt > IOV_MAX) {
 		return (set_errno(EMSGSIZE));
 	}
 
-	if (iovcnt > MSG_MAXIOVLEN) {
-		iovsize = MSG_MAXMAXIOVLEN * sizeof (struct iovec);
+	if (iovcnt > IOV_MAX_STACK) {
+		iovsize = iovcnt * sizeof (struct iovec);
 		aiov = kmem_alloc(iovsize, KM_SLEEP);
 	}
 
@@ -1086,16 +1079,17 @@ recvmsg(int sock, struct nmsghdr *msg, int flags)
 	 * that they can't move more than 2Gbytes of data in a single call.
 	 */
 	if (model == DATAMODEL_ILP32) {
-		struct iovec32 buf32[MSG_MAXIOVLEN], *aiov32 = buf32;
+		struct iovec32 buf32[IOV_MAX_STACK], *aiov32 = buf32;
+		ssize_t iov32size;
 		ssize32_t count32;
 
+		iov32size = iovcnt * sizeof (struct iovec32);
 		if (iovsize != 0)
-			aiov32 = kmem_alloc(iovsize, KM_SLEEP);
+			aiov32 = kmem_alloc(iov32size, KM_SLEEP);
 
-		if (copyin((struct iovec32 *)lmsg.msg_iov, aiov32,
-		    iovcnt * sizeof (struct iovec32))) {
+		if (copyin((struct iovec32 *)lmsg.msg_iov, aiov32, iov32size)) {
 			if (iovsize != 0) {
-				kmem_free(aiov32, iovsize);
+				kmem_free(aiov32, iov32size);
 				kmem_free(aiov, iovsize);
 			}
 
@@ -1110,7 +1104,7 @@ recvmsg(int sock, struct nmsghdr *msg, int flags)
 			count32 += iovlen32;
 			if (iovlen32 < 0 || count32 < 0) {
 				if (iovsize != 0) {
-					kmem_free(aiov32, iovsize);
+					kmem_free(aiov32, iov32size);
 					kmem_free(aiov, iovsize);
 				}
 
@@ -1123,7 +1117,7 @@ recvmsg(int sock, struct nmsghdr *msg, int flags)
 		}
 
 		if (iovsize != 0)
-			kmem_free(aiov32, iovsize);
+			kmem_free(aiov32, iov32size);
 	} else
 #endif /* _SYSCALL32_IMPL */
 	if (copyin(lmsg.msg_iov, aiov, iovcnt * sizeof (struct iovec))) {
@@ -1305,7 +1299,7 @@ sendmsg(int sock, struct nmsghdr *msg, int flags)
 	struct nmsghdr lmsg;
 	STRUCT_DECL(nmsghdr, u_lmsg);
 	struct uio auio;
-	struct iovec buf[MSG_MAXIOVLEN], *aiov = buf;
+	struct iovec buf[IOV_MAX_STACK], *aiov = buf;
 	ssize_t iovsize = 0;
 	int iovcnt;
 	ssize_t len, rval;
@@ -1351,7 +1345,7 @@ sendmsg(int sock, struct nmsghdr *msg, int flags)
 
 	iovcnt = lmsg.msg_iovlen;
 
-	if (iovcnt <= 0 || iovcnt > MSG_MAXMAXIOVLEN) {
+	if (iovcnt <= 0 || iovcnt > IOV_MAX) {
 		/*
 		 * Unless this is XPG 4.2 we allow iovcnt == 0 to
 		 * be compatible with SunOS 4.X and 4.4BSD.
@@ -1360,8 +1354,8 @@ sendmsg(int sock, struct nmsghdr *msg, int flags)
 			return (set_errno(EMSGSIZE));
 	}
 
-	if (iovcnt > MSG_MAXIOVLEN) {
-		iovsize = MSG_MAXMAXIOVLEN * sizeof (struct iovec);
+	if (iovcnt > IOV_MAX_STACK) {
+		iovsize = iovcnt * sizeof (struct iovec);
 		aiov = kmem_alloc(iovsize, KM_SLEEP);
 	}
 
@@ -1371,17 +1365,18 @@ sendmsg(int sock, struct nmsghdr *msg, int flags)
 	 * that they can't move more than 2Gbytes of data in a single call.
 	 */
 	if (model == DATAMODEL_ILP32) {
-		struct iovec32 buf32[MSG_MAXIOVLEN], *aiov32 = buf32;
+		struct iovec32 buf32[IOV_MAX_STACK], *aiov32 = buf32;
+		ssize_t iov32size;
 		ssize32_t count32;
 
+		iov32size = iovcnt * sizeof (struct iovec32);
 		if (iovsize != 0)
-			aiov32 = kmem_alloc(iovsize, KM_SLEEP);
+			aiov32 = kmem_alloc(iov32size, KM_SLEEP);
 
 		if (iovcnt != 0 &&
-		    copyin((struct iovec32 *)lmsg.msg_iov, aiov32,
-		    iovcnt * sizeof (struct iovec32))) {
+		    copyin((struct iovec32 *)lmsg.msg_iov, aiov32, iov32size)) {
 			if (iovsize != 0) {
-				kmem_free(aiov32, iovsize);
+				kmem_free(aiov32, iov32size);
 				kmem_free(aiov, iovsize);
 			}
 
@@ -1396,7 +1391,7 @@ sendmsg(int sock, struct nmsghdr *msg, int flags)
 			count32 += iovlen32;
 			if (iovlen32 < 0 || count32 < 0) {
 				if (iovsize != 0) {
-					kmem_free(aiov32, iovsize);
+					kmem_free(aiov32, iov32size);
 					kmem_free(aiov, iovsize);
 				}
 
@@ -1409,7 +1404,7 @@ sendmsg(int sock, struct nmsghdr *msg, int flags)
 		}
 
 		if (iovsize != 0)
-			kmem_free(aiov32, iovsize);
+			kmem_free(aiov32, iov32size);
 	} else
 #endif /* _SYSCALL32_IMPL */
 	if (iovcnt != 0 &&
diff --git a/usr/src/uts/common/io/cons.c b/usr/src/uts/common/io/cons.c
index 6ef1b0b9f7..495ae93cf9 100644
--- a/usr/src/uts/common/io/cons.c
+++ b/usr/src/uts/common/io/cons.c
@@ -21,6 +21,7 @@
 
 /*
  * Copyright (c) 1982, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2015, Joyent, Inc. All rights reserved.
  */
 
 /*
@@ -53,6 +54,7 @@
 #include <sys/vnode.h>
 #include <sys/uio.h>
 #include <sys/stat.h>
+#include <sys/limits.h>
 
 #include <sys/console.h>
 #include <sys/consdev.h>
@@ -414,14 +416,24 @@ cnwrite(dev_t dev, struct uio *uio, struct cred *cred)
 	 */
 	if (vsconsvp != NULL && vsconsvp->v_stream != NULL) {
 		struiod_t uiod;
+		struct iovec buf[IOV_MAX_STACK];
+		int iovlen = 0;
+
+		if (uio->uio_iovcnt > IOV_MAX_STACK) {
+			iovlen = uio->uio_iovcnt * sizeof (iovec_t);
+			uiod.d_iov = kmem_alloc(iovlen, KM_SLEEP);
+		} else {
+			uiod.d_iov = buf;
+		}
 
 		/*
 		 * strwrite modifies uio so need to make copy.
 		 */
-		(void) uiodup(uio, &uiod.d_uio, uiod.d_iov,
-		    sizeof (uiod.d_iov) / sizeof (*uiod.d_iov));
+		(void) uiodup(uio, &uiod.d_uio, uiod.d_iov, uio->uio_iovcnt);
 
 		(void) strwrite(vsconsvp, &uiod.d_uio, cred);
+		if (iovlen != 0)
+			kmem_free(uiod.d_iov, iovlen);
 	}
 
 	if (rconsvp->v_stream != NULL)
diff --git a/usr/src/uts/common/os/streamio.c b/usr/src/uts/common/os/streamio.c
index 4c99f92411..0f3aafcc42 100644
--- a/usr/src/uts/common/os/streamio.c
+++ b/usr/src/uts/common/os/streamio.c
@@ -24,7 +24,7 @@
 
 /*
  * Copyright (c) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2014, Joyent, Inc. All rights reserved.
+ * Copyright 2015, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/types.h>
@@ -77,6 +77,7 @@
 #include <sys/policy.h>
 #include <sys/dld.h>
 #include <sys/zone.h>
+#include <sys/limits.h>
 #include <c2/audit.h>
 
 /*
@@ -985,12 +986,20 @@ strget(struct stdata *stp, queue_t *q, struct uio *uiop, int first,
 		 * (registered in sd_wakeq).
 		 */
 		struiod_t uiod;
+		struct iovec buf[IOV_MAX_STACK];
+		int iovlen = 0;
 
 		if (first)
 			stp->sd_wakeq &= ~RSLEEP;
 
-		(void) uiodup(uiop, &uiod.d_uio, uiod.d_iov,
-		    sizeof (uiod.d_iov) / sizeof (*uiod.d_iov));
+		if (uiop->uio_iovcnt > IOV_MAX_STACK) {
+			iovlen = uiop->uio_iovcnt * sizeof (iovec_t);
+			uiod.d_iov = kmem_alloc(iovlen, KM_SLEEP);
+		} else {
+			uiod.d_iov = buf;
+		}
+
+		(void) uiodup(uiop, &uiod.d_uio, uiod.d_iov, uiop->uio_iovcnt);
 		uiod.d_mp = 0;
 		/*
 		 * Mark that a thread is in rwnext on the read side
@@ -1029,6 +1038,8 @@ strget(struct stdata *stp, queue_t *q, struct uio *uiop, int first,
 			if ((bp = uiod.d_mp) != NULL) {
 				*errorp = 0;
 				ASSERT(MUTEX_HELD(&stp->sd_lock));
+				if (iovlen != 0)
+					kmem_free(uiod.d_iov, iovlen);
 				return (bp);
 			}
 			error = 0;
@@ -1048,8 +1059,14 @@ strget(struct stdata *stp, queue_t *q, struct uio *uiop, int first,
 		} else {
 			*errorp = error;
 			ASSERT(MUTEX_HELD(&stp->sd_lock));
+			if (iovlen != 0)
+				kmem_free(uiod.d_iov, iovlen);
 			return (NULL);
 		}
+
+		if (iovlen != 0)
+			kmem_free(uiod.d_iov, iovlen);
+
 		/*
 		 * Try a getq in case a rwnext() generated mblk
 		 * has bubbled up via strrput().
@@ -2544,6 +2561,8 @@ strput(struct stdata *stp, mblk_t *mctl, struct uio *uiop, ssize_t *iosize,
     int b_flag, int pri, int flags)
 {
 	struiod_t uiod;
+	struct iovec buf[IOV_MAX_STACK];
+	int iovlen = 0;
 	mblk_t *mp;
 	queue_t *wqp = stp->sd_wrq;
 	int error = 0;
@@ -2635,13 +2654,21 @@ strput(struct stdata *stp, mblk_t *mctl, struct uio *uiop, ssize_t *iosize,
 	mp->b_flag |= b_flag;
 	mp->b_band = (uchar_t)pri;
 
-	(void) uiodup(uiop, &uiod.d_uio, uiod.d_iov,
-	    sizeof (uiod.d_iov) / sizeof (*uiod.d_iov));
+	if (uiop->uio_iovcnt > IOV_MAX_STACK) {
+		iovlen = uiop->uio_iovcnt * sizeof (iovec_t);
+		uiod.d_iov = (struct iovec *)kmem_alloc(iovlen, KM_SLEEP);
+	} else {
+		uiod.d_iov = buf;
+	}
+
+	(void) uiodup(uiop, &uiod.d_uio, uiod.d_iov, uiop->uio_iovcnt);
 	uiod.d_uio.uio_offset = 0;
 	uiod.d_mp = mp;
 	error = rwnext(wqp, &uiod);
 	if (! uiod.d_mp) {
 		uioskip(uiop, *iosize);
+		if (iovlen != 0)
+			kmem_free(uiod.d_iov, iovlen);
 		return (error);
 	}
 	ASSERT(mp == uiod.d_mp);
@@ -2659,17 +2686,23 @@ strput(struct stdata *stp, mblk_t *mctl, struct uio *uiop, ssize_t *iosize,
 		error = 0;
 	} else {
 		freemsg(mp);
+		if (iovlen != 0)
+			kmem_free(uiod.d_iov, iovlen);
 		return (error);
 	}
 	/* Have to check canput before consuming data from the uio */
 	if (pri == 0) {
 		if (!canputnext(wqp) && !(flags & MSG_IGNFLOW)) {
 			freemsg(mp);
+			if (iovlen != 0)
+				kmem_free(uiod.d_iov, iovlen);
 			return (EWOULDBLOCK);
 		}
 	} else {
 		if (!bcanputnext(wqp, pri) && !(flags & MSG_IGNFLOW)) {
 			freemsg(mp);
+			if (iovlen != 0)
+				kmem_free(uiod.d_iov, iovlen);
 			return (EWOULDBLOCK);
 		}
 	}
@@ -2677,6 +2710,8 @@ strput(struct stdata *stp, mblk_t *mctl, struct uio *uiop, ssize_t *iosize,
 	/* Copyin data from the uio */
 	if ((error = struioget(wqp, mp, &uiod, 0)) != 0) {
 		freemsg(mp);
+		if (iovlen != 0)
+			kmem_free(uiod.d_iov, iovlen);
 		return (error);
 	}
 	uioskip(uiop, *iosize);
@@ -2693,6 +2728,8 @@ strput(struct stdata *stp, mblk_t *mctl, struct uio *uiop, ssize_t *iosize,
 		putnext(wqp, mp);
 		stream_runservice(stp);
 	}
+	if (iovlen != 0)
+		kmem_free(uiod.d_iov, iovlen);
 	return (0);
 }
 
diff --git a/usr/src/uts/common/sys/Makefile b/usr/src/uts/common/sys/Makefile
index 6f28942704..7acdd7ebe8 100644
--- a/usr/src/uts/common/sys/Makefile
+++ b/usr/src/uts/common/sys/Makefile
@@ -22,7 +22,7 @@
 # Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
 # Copyright 2013, Joyent, Inc. All rights reserved.
 # Copyright 2013 Garrett D'Amore <garrett@damore.org>
-# Copyright (c) 2014, Joyent, Inc. All rights reserved.
+# Copyright 2015, Joyent, Inc. All rights reserved.
 #
 
 include $(SRC)/uts/Makefile.uts
@@ -341,6 +341,7 @@ CHKHDRS=			\
 	lgrp.h			\
 	lgrp_user.h		\
 	libc_kernel.h		\
+	limits.h		\
 	link.h			\
 	list.h			\
 	list_impl.h		\
diff --git a/usr/src/uts/common/sys/limits.h b/usr/src/uts/common/sys/limits.h
new file mode 100644
index 0000000000..88625d1829
--- /dev/null
+++ b/usr/src/uts/common/sys/limits.h
@@ -0,0 +1,32 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+/*
+ * Copyright 2015 Joyent, Inc.  All rights reserved.
+ */
+
+#ifndef _SYS_LIMITS_H
+#define	_SYS_LIMITS_H
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+#define	IOV_MAX	1024
+
+#ifdef _KERNEL
+#define	IOV_MAX_STACK	16	/* max. IOV on-stack allocation */
+#endif /* _KERNEL */
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* _SYS_LIMITS_H */
diff --git a/usr/src/uts/common/sys/socket.h b/usr/src/uts/common/sys/socket.h
index bbe2121d0e..f5864db7d3 100644
--- a/usr/src/uts/common/sys/socket.h
+++ b/usr/src/uts/common/sys/socket.h
@@ -22,6 +22,7 @@
  * Copyright 2014 Garrett D'Amore <garrett@damore.org>
  *
  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2015, Joyent, Inc. All rights reserved.
  */
 
 /*	Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T	*/
@@ -425,6 +426,7 @@ struct msghdr32 {
 #define	MSG_NOTIFICATION 0x100		/* Notification, not data */
 #define	MSG_XPG4_2	0x8000		/* Private: XPG4.2 flag */
 
+/* Obsolete but kept for compilation compatability. Use IOV_MAX. */
 #define	MSG_MAXIOVLEN	16
 
 #ifdef _KERNEL
diff --git a/usr/src/uts/common/sys/stream.h b/usr/src/uts/common/sys/stream.h
index 7a3b4e3448..4151cc0208 100644
--- a/usr/src/uts/common/sys/stream.h
+++ b/usr/src/uts/common/sys/stream.h
@@ -21,6 +21,7 @@
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright 2015 Joyent, Inc.  All rights reserved.
  */
 
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
@@ -627,16 +628,11 @@ struct stroptions {
 /*
  * Structure for rw (read/write) procedure calls. A pointer
  * to a struiod_t is passed as a parameter to the rwnext() call.
- *
- * Note: DEF_IOV_MAX is defined and used as it is in "fs/vncalls.c"
- *	 as there isn't a formal definition of IOV_MAX ???
  */
-#define	DEF_IOV_MAX	16
-
 typedef struct struiod {
 	mblk_t		*d_mp;		/* pointer to mblk (chain) */
 	uio_t		d_uio;		/* uio info */
-	iovec_t d_iov[DEF_IOV_MAX];	/* iov referenced by uio */
+	iovec_t 	*d_iov;		/* iov referenced by uio */
 } struiod_t;
 
 /*
diff --git a/usr/src/uts/common/syscall/rw.c b/usr/src/uts/common/syscall/rw.c
index a28894b2c9..943b7d244e 100644
--- a/usr/src/uts/common/syscall/rw.c
+++ b/usr/src/uts/common/syscall/rw.c
@@ -22,7 +22,7 @@
 /*
  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
- * Copyright (c) 2015, Joyent, Inc.  All rights reserved.
+ * Copyright 2015, Joyent, Inc.  All rights reserved.
  */
 
 /*	Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T	*/
@@ -50,6 +50,7 @@
 #include <sys/debug.h>
 #include <sys/rctl.h>
 #include <sys/nbmlock.h>
+#include <sys/limits.h>
 
 #define	COPYOUT_MAX_CACHE	(1<<17)		/* 128K */
 
@@ -607,19 +608,12 @@ out:
 	return (bcount);
 }
 
-/*
- * XXX -- The SVID refers to IOV_MAX, but doesn't define it.  Grrrr....
- * XXX -- However, SVVS expects readv() and writev() to fail if
- * XXX -- iovcnt > 16 (yes, it's hard-coded in the SVVS source),
- * XXX -- so I guess that's the "interface".
- */
-#define	DEF_IOV_MAX	16
-
 ssize_t
 readv(int fdes, struct iovec *iovp, int iovcnt)
 {
 	struct uio auio;
-	struct iovec aiov[DEF_IOV_MAX];
+	struct iovec buf[IOV_MAX_STACK], *aiov = buf;
+	int aiovlen = 0;
 	file_t *fp;
 	register vnode_t *vp;
 	struct cpu *cp;
@@ -630,9 +624,14 @@ readv(int fdes, struct iovec *iovp, int iovcnt)
 	u_offset_t fileoff;
 	int in_crit = 0;
 
-	if (iovcnt <= 0 || iovcnt > DEF_IOV_MAX)
+	if (iovcnt <= 0 || iovcnt > IOV_MAX)
 		return (set_errno(EINVAL));
 
+	if (iovcnt > IOV_MAX_STACK) {
+		aiovlen = iovcnt * sizeof (iovec_t);
+		aiov = kmem_alloc(aiovlen, KM_SLEEP);
+	}
+
 #ifdef _SYSCALL32_IMPL
 	/*
 	 * 32-bit callers need to have their iovec expanded,
@@ -640,36 +639,63 @@ readv(int fdes, struct iovec *iovp, int iovcnt)
 	 * of data in a single call.
 	 */
 	if (get_udatamodel() == DATAMODEL_ILP32) {
-		struct iovec32 aiov32[DEF_IOV_MAX];
+		struct iovec32 buf32[IOV_MAX_STACK], *aiov32 = buf32;
+		int aiov32len;
 		ssize32_t count32;
 
-		if (copyin(iovp, aiov32, iovcnt * sizeof (struct iovec32)))
+		aiov32len = iovcnt * sizeof (iovec32_t);
+		if (aiovlen != 0)
+			aiov32 = kmem_alloc(aiov32len, KM_SLEEP);
+
+		if (copyin(iovp, aiov32, aiov32len)) {
+			if (aiovlen != 0) {
+				kmem_free(aiov32, aiov32len);
+				kmem_free(aiov, aiovlen);
+			}
 			return (set_errno(EFAULT));
+		}
 
 		count32 = 0;
 		for (i = 0; i < iovcnt; i++) {
 			ssize32_t iovlen32 = aiov32[i].iov_len;
 			count32 += iovlen32;
-			if (iovlen32 < 0 || count32 < 0)
+			if (iovlen32 < 0 || count32 < 0) {
+				if (aiovlen != 0) {
+					kmem_free(aiov32, aiov32len);
+					kmem_free(aiov, aiovlen);
+				}
 				return (set_errno(EINVAL));
+			}
 			aiov[i].iov_len = iovlen32;
 			aiov[i].iov_base =
 			    (caddr_t)(uintptr_t)aiov32[i].iov_base;
 		}
+
+		if (aiovlen != 0)
+			kmem_free(aiov32, aiov32len);
 	} else
 #endif
-	if (copyin(iovp, aiov, iovcnt * sizeof (struct iovec)))
+	if (copyin(iovp, aiov, iovcnt * sizeof (iovec_t))) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EFAULT));
+	}
 
 	count = 0;
 	for (i = 0; i < iovcnt; i++) {
 		ssize_t iovlen = aiov[i].iov_len;
 		count += iovlen;
-		if (iovlen < 0 || count < 0)
+		if (iovlen < 0 || count < 0) {
+			if (aiovlen != 0)
+				kmem_free(aiov, aiovlen);
 			return (set_errno(EINVAL));
+		}
 	}
-	if ((fp = getf(fdes)) == NULL)
+	if ((fp = getf(fdes)) == NULL) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EBADF));
+	}
 	if (((fflag = fp->f_flag) & FREAD) == 0) {
 		error = EBADF;
 		goto out;
@@ -768,6 +794,8 @@ out:
 	if (in_crit)
 		nbl_end_crit(vp);
 	releasef(fdes);
+	if (aiovlen != 0)
+		kmem_free(aiov, aiovlen);
 	if (error)
 		return (set_errno(error));
 	return (count);
@@ -777,7 +805,8 @@ ssize_t
 writev(int fdes, struct iovec *iovp, int iovcnt)
 {
 	struct uio auio;
-	struct iovec aiov[DEF_IOV_MAX];
+	struct iovec buf[IOV_MAX_STACK], *aiov = buf;
+	int aiovlen = 0;
 	file_t *fp;
 	register vnode_t *vp;
 	struct cpu *cp;
@@ -788,9 +817,14 @@ writev(int fdes, struct iovec *iovp, int iovcnt)
 	u_offset_t fileoff;
 	int in_crit = 0;
 
-	if (iovcnt <= 0 || iovcnt > DEF_IOV_MAX)
+	if (iovcnt <= 0 || iovcnt > IOV_MAX)
 		return (set_errno(EINVAL));
 
+	if (iovcnt > IOV_MAX_STACK) {
+		aiovlen = iovcnt * sizeof (iovec_t);
+		aiov = kmem_alloc(aiovlen, KM_SLEEP);
+	}
+
 #ifdef _SYSCALL32_IMPL
 	/*
 	 * 32-bit callers need to have their iovec expanded,
@@ -798,36 +832,62 @@ writev(int fdes, struct iovec *iovp, int iovcnt)
 	 * of data in a single call.
 	 */
 	if (get_udatamodel() == DATAMODEL_ILP32) {
-		struct iovec32 aiov32[DEF_IOV_MAX];
+		struct iovec32 buf32[IOV_MAX_STACK], *aiov32 = buf32;
+		int aiov32len;
 		ssize32_t count32;
 
-		if (copyin(iovp, aiov32, iovcnt * sizeof (struct iovec32)))
+		aiov32len = iovcnt * sizeof (iovec32_t);
+		if (aiovlen != 0)
+			aiov32 = kmem_alloc(aiov32len, KM_SLEEP);
+
+		if (copyin(iovp, aiov32, aiov32len)) {
+			if (aiovlen != 0) {
+				kmem_free(aiov32, aiov32len);
+				kmem_free(aiov, aiovlen);
+			}
 			return (set_errno(EFAULT));
+		}
 
 		count32 = 0;
 		for (i = 0; i < iovcnt; i++) {
 			ssize32_t iovlen = aiov32[i].iov_len;
 			count32 += iovlen;
-			if (iovlen < 0 || count32 < 0)
+			if (iovlen < 0 || count32 < 0) {
+				if (aiovlen != 0) {
+					kmem_free(aiov32, aiov32len);
+					kmem_free(aiov, aiovlen);
+				}
 				return (set_errno(EINVAL));
+			}
 			aiov[i].iov_len = iovlen;
 			aiov[i].iov_base =
 			    (caddr_t)(uintptr_t)aiov32[i].iov_base;
 		}
+		if (aiovlen != 0)
+			kmem_free(aiov32, aiov32len);
 	} else
 #endif
-	if (copyin(iovp, aiov, iovcnt * sizeof (struct iovec)))
+	if (copyin(iovp, aiov, iovcnt * sizeof (iovec_t))) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EFAULT));
+	}
 
 	count = 0;
 	for (i = 0; i < iovcnt; i++) {
 		ssize_t iovlen = aiov[i].iov_len;
 		count += iovlen;
-		if (iovlen < 0 || count < 0)
+		if (iovlen < 0 || count < 0) {
+			if (aiovlen != 0)
+				kmem_free(aiov, aiovlen);
 			return (set_errno(EINVAL));
+		}
 	}
-	if ((fp = getf(fdes)) == NULL)
+	if ((fp = getf(fdes)) == NULL) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EBADF));
+	}
 	if (((fflag = fp->f_flag) & FWRITE) == 0) {
 		error = EBADF;
 		goto out;
@@ -917,6 +977,8 @@ out:
 	if (in_crit)
 		nbl_end_crit(vp);
 	releasef(fdes);
+	if (aiovlen != 0)
+		kmem_free(aiov, aiovlen);
 	if (error)
 		return (set_errno(error));
 	return (count);
@@ -927,7 +989,8 @@ preadv(int fdes, struct iovec *iovp, int iovcnt, off_t offset,
     off_t extended_offset)
 {
 	struct uio auio;
-	struct iovec aiov[DEF_IOV_MAX];
+	struct iovec buf[IOV_MAX_STACK], *aiov = buf;
+	int aiovlen = 0;
 	file_t *fp;
 	register vnode_t *vp;
 	struct cpu *cp;
@@ -952,9 +1015,14 @@ preadv(int fdes, struct iovec *iovp, int iovcnt, off_t offset,
 
 	int in_crit = 0;
 
-	if (iovcnt <= 0 || iovcnt > DEF_IOV_MAX)
+	if (iovcnt <= 0 || iovcnt > IOV_MAX)
 		return (set_errno(EINVAL));
 
+	if (iovcnt > IOV_MAX_STACK) {
+		aiovlen = iovcnt * sizeof (iovec_t);
+		aiov = kmem_alloc(aiovlen, KM_SLEEP);
+	}
+
 #ifdef _SYSCALL32_IMPL
 	/*
 	 * 32-bit callers need to have their iovec expanded,
@@ -962,39 +1030,68 @@ preadv(int fdes, struct iovec *iovp, int iovcnt, off_t offset,
 	 * of data in a single call.
 	 */
 	if (get_udatamodel() == DATAMODEL_ILP32) {
-		struct iovec32 aiov32[DEF_IOV_MAX];
+		struct iovec32 buf32[IOV_MAX_STACK], *aiov32 = buf32;
+		int aiov32len;
 		ssize32_t count32;
 
-		if (copyin(iovp, aiov32, iovcnt * sizeof (struct iovec32)))
+		aiov32len = iovcnt * sizeof (iovec32_t);
+		if (aiovlen != 0)
+			aiov32 = kmem_alloc(aiov32len, KM_SLEEP);
+
+		if (copyin(iovp, aiov32, aiov32len)) {
+			if (aiovlen != 0) {
+				kmem_free(aiov32, aiov32len);
+				kmem_free(aiov, aiovlen);
+			}
 			return (set_errno(EFAULT));
+		}
 
 		count32 = 0;
 		for (i = 0; i < iovcnt; i++) {
 			ssize32_t iovlen32 = aiov32[i].iov_len;
 			count32 += iovlen32;
-			if (iovlen32 < 0 || count32 < 0)
+			if (iovlen32 < 0 || count32 < 0) {
+				if (aiovlen != 0) {
+					kmem_free(aiov32, aiov32len);
+					kmem_free(aiov, aiovlen);
+				}
 				return (set_errno(EINVAL));
+			}
 			aiov[i].iov_len = iovlen32;
 			aiov[i].iov_base =
 			    (caddr_t)(uintptr_t)aiov32[i].iov_base;
 		}
+		if (aiovlen != 0)
+			kmem_free(aiov32, aiov32len);
 	} else
 #endif /* _SYSCALL32_IMPL */
-		if (copyin(iovp, aiov, iovcnt * sizeof (struct iovec)))
+		if (copyin(iovp, aiov, iovcnt * sizeof (iovec_t))) {
+			if (aiovlen != 0)
+				kmem_free(aiov, aiovlen);
 			return (set_errno(EFAULT));
+		}
 
 	count = 0;
 	for (i = 0; i < iovcnt; i++) {
 		ssize_t iovlen = aiov[i].iov_len;
 		count += iovlen;
-		if (iovlen < 0 || count < 0)
+		if (iovlen < 0 || count < 0) {
+			if (aiovlen != 0)
+				kmem_free(aiov, aiovlen);
 			return (set_errno(EINVAL));
+		}
 	}
 
-	if ((bcount = (ssize_t)count) < 0)
+	if ((bcount = (ssize_t)count) < 0) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EINVAL));
-	if ((fp = getf(fdes)) == NULL)
+	}
+	if ((fp = getf(fdes)) == NULL) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EBADF));
+	}
 	if (((fflag = fp->f_flag) & FREAD) == 0) {
 		error = EBADF;
 		goto out;
@@ -1099,6 +1196,8 @@ out:
 	if (in_crit)
 		nbl_end_crit(vp);
 	releasef(fdes);
+	if (aiovlen != 0)
+		kmem_free(aiov, aiovlen);
 	if (error)
 		return (set_errno(error));
 	return (count);
@@ -1109,7 +1208,8 @@ pwritev(int fdes, struct iovec *iovp, int iovcnt, off_t offset,
     off_t extended_offset)
 {
 	struct uio auio;
-	struct iovec aiov[DEF_IOV_MAX];
+	struct iovec buf[IOV_MAX_STACK], *aiov = buf;
+	int aiovlen = 0;
 	file_t *fp;
 	register vnode_t *vp;
 	struct cpu *cp;
@@ -1134,9 +1234,14 @@ pwritev(int fdes, struct iovec *iovp, int iovcnt, off_t offset,
 
 	int in_crit = 0;
 
-	if (iovcnt <= 0 || iovcnt > DEF_IOV_MAX)
+	if (iovcnt <= 0 || iovcnt > IOV_MAX)
 		return (set_errno(EINVAL));
 
+	if (iovcnt > IOV_MAX_STACK) {
+		aiovlen = iovcnt * sizeof (iovec_t);
+		aiov = kmem_alloc(aiovlen, KM_SLEEP);
+	}
+
 #ifdef _SYSCALL32_IMPL
 	/*
 	 * 32-bit callers need to have their iovec expanded,
@@ -1144,39 +1249,68 @@ pwritev(int fdes, struct iovec *iovp, int iovcnt, off_t offset,
 	 * of data in a single call.
 	 */
 	if (get_udatamodel() == DATAMODEL_ILP32) {
-		struct iovec32 aiov32[DEF_IOV_MAX];
+		struct iovec32 buf32[IOV_MAX_STACK], *aiov32 = buf32;
+		int aiov32len;
 		ssize32_t count32;
 
-		if (copyin(iovp, aiov32, iovcnt * sizeof (struct iovec32)))
+		aiov32len = iovcnt * sizeof (iovec32_t);
+		if (aiovlen != 0)
+			aiov32 = kmem_alloc(aiov32len, KM_SLEEP);
+
+		if (copyin(iovp, aiov32, aiov32len)) {
+			if (aiovlen != 0) {
+				kmem_free(aiov32, aiov32len);
+				kmem_free(aiov, aiovlen);
+			}
 			return (set_errno(EFAULT));
+		}
 
 		count32 = 0;
 		for (i = 0; i < iovcnt; i++) {
 			ssize32_t iovlen32 = aiov32[i].iov_len;
 			count32 += iovlen32;
-			if (iovlen32 < 0 || count32 < 0)
+			if (iovlen32 < 0 || count32 < 0) {
+				if (aiovlen != 0) {
+					kmem_free(aiov32, aiov32len);
+					kmem_free(aiov, aiovlen);
+				}
 				return (set_errno(EINVAL));
+			}
 			aiov[i].iov_len = iovlen32;
 			aiov[i].iov_base =
 			    (caddr_t)(uintptr_t)aiov32[i].iov_base;
 		}
+		if (aiovlen != 0)
+			kmem_free(aiov32, aiov32len);
 	} else
 #endif /* _SYSCALL32_IMPL */
-		if (copyin(iovp, aiov, iovcnt * sizeof (struct iovec)))
+		if (copyin(iovp, aiov, iovcnt * sizeof (iovec_t))) {
+			if (aiovlen != 0)
+				kmem_free(aiov, aiovlen);
 			return (set_errno(EFAULT));
+		}
 
 	count = 0;
 	for (i = 0; i < iovcnt; i++) {
 		ssize_t iovlen = aiov[i].iov_len;
 		count += iovlen;
-		if (iovlen < 0 || count < 0)
+		if (iovlen < 0 || count < 0) {
+			if (aiovlen != 0)
+				kmem_free(aiov, aiovlen);
 			return (set_errno(EINVAL));
+		}
 	}
 
-	if ((bcount = (ssize_t)count) < 0)
+	if ((bcount = (ssize_t)count) < 0) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EINVAL));
-	if ((fp = getf(fdes)) == NULL)
+	}
+	if ((fp = getf(fdes)) == NULL) {
+		if (aiovlen != 0)
+			kmem_free(aiov, aiovlen);
 		return (set_errno(EBADF));
+	}
 	if (((fflag = fp->f_flag) & FWRITE) == 0) {
 		error = EBADF;
 		goto out;
@@ -1308,6 +1442,8 @@ out:
 	if (in_crit)
 		nbl_end_crit(vp);
 	releasef(fdes);
+	if (aiovlen != 0)
+		kmem_free(aiov, aiovlen);
 	if (error)
 		return (set_errno(error));
 	return (count);