Index: head/sys/boot/common/md.c
===================================================================
--- head/sys/boot/common/md.c
+++ head/sys/boot/common/md.c
@@ -106,7 +106,7 @@
 	if (rsize != NULL)
 		*rsize = size;
 
-	switch (rw) {
+	switch (rw & F_MASK) {
 	case F_READ:
 		bcopy(md_image.start + ofs, buf, size);
 		return (0);
Index: head/sys/boot/efi/libefi/efipart.c
===================================================================
--- head/sys/boot/efi/libefi/efipart.c
+++ head/sys/boot/efi/libefi/efipart.c
@@ -819,7 +819,7 @@
 	if ((blk + nblks - 1) > blkio->Media->LastBlock)
 		return (EIO);
 
-	switch (rw) {
+	switch (rw & F_MASK) {
 	case F_READ:
 		status = blkio->ReadBlocks(blkio, blkio->Media->MediaId, blk,
 		    nblks * blkio->Media->BlockSize, buf);
Index: head/sys/boot/i386/libi386/bioscd.c
===================================================================
--- head/sys/boot/i386/libi386/bioscd.c
+++ head/sys/boot/i386/libi386/bioscd.c
@@ -268,7 +268,7 @@
 		return (EINVAL);
 #endif
 
-	if (rw != F_READ)
+	if ((rw & F_MASK) != F_READ)
 		return(EROFS);
 	dev = (struct i386_devdesc *)devdata;
 	unit = dev->d_unit;
Index: head/sys/boot/i386/libi386/biosdisk.c
===================================================================
--- head/sys/boot/i386/libi386/biosdisk.c
+++ head/sys/boot/i386/libi386/biosdisk.c
@@ -618,7 +618,7 @@
 	DEBUG("short read %d", blks);
     }
 
-    switch(rw){
+    switch (rw & F_MASK) {
     case F_READ:
 	DEBUG("read %d from %lld to %p", blks, dblk, buf);
 
Index: head/sys/boot/mips/beri/loader/beri_disk_cfi.c
===================================================================
--- head/sys/boot/mips/beri/loader/beri_disk_cfi.c
+++ head/sys/boot/mips/beri/loader/beri_disk_cfi.c
@@ -73,6 +73,7 @@
 {
 	int error;
 
+	flag &= F_MASK;
 	if (flag == F_WRITE)
 		return (EROFS);
 	if (flag != F_READ)
Index: head/sys/boot/mips/beri/loader/beri_disk_sdcard.c
===================================================================
--- head/sys/boot/mips/beri/loader/beri_disk_sdcard.c
+++ head/sys/boot/mips/beri/loader/beri_disk_sdcard.c
@@ -73,6 +73,7 @@
 {
 	int error;
 
+	flag &= F_MASK;
 	if (flag == F_WRITE)
 		return (EROFS);
 	if (flag != F_READ)
Index: head/sys/boot/powerpc/ps3/ps3cdrom.c
===================================================================
--- head/sys/boot/powerpc/ps3/ps3cdrom.c
+++ head/sys/boot/powerpc/ps3/ps3cdrom.c
@@ -83,6 +83,7 @@
 
 	DEBUG("d_unit=%u dblk=%llu size=%u", dev->d_unit, dblk, size);
 
+	flag &= F_MASK;
 	if (flag != F_READ) {
 		dev_printf(dev, "write operation is not supported!");
 		return EROFS;
Index: head/sys/boot/powerpc/ps3/ps3disk.c
===================================================================
--- head/sys/boot/powerpc/ps3/ps3disk.c
+++ head/sys/boot/powerpc/ps3/ps3disk.c
@@ -115,6 +115,7 @@
 	struct open_dev *od = (struct open_dev *) dev->d_disk.data;
 	int err;
 
+	flag &= F_MASK;
 	if (flag != F_READ) {
 		dev_printf(dev, "write operation is not supported!\n");
 		return EROFS;
Index: head/sys/boot/uboot/lib/disk.c
===================================================================
--- head/sys/boot/uboot/lib/disk.c
+++ head/sys/boot/uboot/lib/disk.c
@@ -149,6 +149,7 @@
 	daddr_t bcount;
 	int err;
 
+	rw &= F_MASK;
 	if (rw != F_READ) {
 		stor_printf("write attempt, operation not supported!\n");
 		return (EROFS);
Index: head/sys/boot/usb/storage/umass_loader.c
===================================================================
--- head/sys/boot/usb/storage/umass_loader.c
+++ head/sys/boot/usb/storage/umass_loader.c
@@ -92,6 +92,7 @@
 	if (rsizep != NULL)
 		*rsizep = 0;
 
+	flag &= F_MASK;
 	if (flag == F_WRITE) {
 		if (usb_msc_write_10(umass_uaa.device, 0, dblk, size >> 9, buf) != 0)
 			return (EINVAL);
Index: head/sys/boot/userboot/userboot/userboot_disk.c
===================================================================
--- head/sys/boot/userboot/userboot/userboot_disk.c
+++ head/sys/boot/userboot/userboot/userboot_disk.c
@@ -211,6 +211,7 @@
 	size_t		resid;
 	int		rc;
 
+	rw &= F_MASK;
 	if (rw == F_WRITE)
 		return (EROFS);
 	if (rw != F_READ)