diff --git a/configs/README.txt b/configs/README.txt
index fc4b4cce9c4..ba746ce6873 100644
--- a/configs/README.txt
+++ b/configs/README.txt
@@ -180,6 +180,8 @@ defconfig -- This is a configuration file similar to the Linux
 		CONFIG_JULIAN_TIME - Enables Julian time conversions
 		CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 		  provides /dev/console.  Enables stdout, stderr, stdin.
+		CONFIG_MUTEX_TYPES - Set to enabled support for recursive and
+		  errorcheck mutexes.  Enables pthread_mutexattr_settype().
 
 	The following can be used to disable categories of APIs supported
 	by the OS.  If the compiler supports weak functions, then it
diff --git a/configs/sim/nettest/Make.defs b/configs/sim/nettest/Make.defs
index 28069e16a36..d0cd57f864e 100644
--- a/configs/sim/nettest/Make.defs
+++ b/configs/sim/nettest/Make.defs
@@ -35,6 +35,8 @@
 
 include ${TOPDIR}/.config
 
+HOSTOS			= ${shell uname -o}
+ 
 ifneq ("${CONFIG_DEBUG}","y")
   ARCHOPTIMIZATION	= -g
 else
@@ -62,7 +64,12 @@ AFLAGS			= $(CFLAGS) -D__ASSEMBLY__
 
 OBJEXT			= .o
 LIBEXT			= .a
-EXEEXT			=
+
+ifeq ($(HOSTOS),Cygwin)
+  EXEEXT		= .exe
+else
+  EXEEXT		=
+endif
 
 ifeq ("${CONFIG_DEBUG}","y")
   LDFLAGS		+= -g
diff --git a/configs/sim/ostest/Make.defs b/configs/sim/ostest/Make.defs
index 28069e16a36..d0cd57f864e 100644
--- a/configs/sim/ostest/Make.defs
+++ b/configs/sim/ostest/Make.defs
@@ -35,6 +35,8 @@
 
 include ${TOPDIR}/.config
 
+HOSTOS			= ${shell uname -o}
+ 
 ifneq ("${CONFIG_DEBUG}","y")
   ARCHOPTIMIZATION	= -g
 else
@@ -62,7 +64,12 @@ AFLAGS			= $(CFLAGS) -D__ASSEMBLY__
 
 OBJEXT			= .o
 LIBEXT			= .a
-EXEEXT			=
+
+ifeq ($(HOSTOS),Cygwin)
+  EXEEXT		= .exe
+else
+  EXEEXT		=
+endif
 
 ifeq ("${CONFIG_DEBUG}","y")
   LDFLAGS		+= -g
diff --git a/configs/sim/pashello/Make.defs b/configs/sim/pashello/Make.defs
index 9f23c5da8d9..8b300eed627 100644
--- a/configs/sim/pashello/Make.defs
+++ b/configs/sim/pashello/Make.defs
@@ -35,6 +35,8 @@
 
 include ${TOPDIR}/.config
 
+HOSTOS			= ${shell uname -o}
+ 
 ifneq ("${CONFIG_DEBUG}","y")
   ARCHOPTIMIZATION	= -g
 else
@@ -62,7 +64,12 @@ AFLAGS			= $(CFLAGS) -D__ASSEMBLY__
 
 OBJEXT			= .o
 LIBEXT			= .a
-EXEEXT			=
+
+ifeq ($(HOSTOS),Cygwin)
+  EXEEXT		= .exe
+else
+  EXEEXT		=
+endif
 
 ifeq ("${CONFIG_DEBUG}","y")
   LDFLAGS		+= -g