Running VirtualBox VM host on ReadyNAS Pro

frodo:/c/.vbox# /usr/bin/VBoxManage extpack install Oracle_VM_VirtualBox_Extension_Pack-4.0.4-70112.vbox-extpack
WARNING: The vboxdrv kernel module is not loaded. Either there is no module
         available for the current kernel (2.6.37.5.RNx86_64.2.1) or it failed to
         load. Please recompile the kernel module and install it by

           sudo /etc/init.d/vboxdrv setup

         You will not be able to start VMs until this problem is fixed.
0%...
Progress state: NS_ERROR_FAILURE
VBoxManage: error: Failed to install "/c/.vbox/Oracle_VM_VirtualBox_Extension_Pack-4.0.4-70112.vbox-extpack": Extension pack 'Oracle VM VirtualBox Extension Pack' is already installed. In case of a reinstallation, please uninstall it first
frodo:/c/.vbox# /etc/init.d/vboxdrv setup
Stopping VirtualBox kernel modules ...done.
Uninstalling old VirtualBox DKMS kernel modules ...done.
Trying to register the VirtualBox kernel modules using DKMS ...failed!
  (Failed, trying without DKMS)
Recompiling VirtualBox kernel modules ...failed!
  (Look at /var/log/vbox-install.log to find out what went wrong)
frodo:/c/.vbox# cat /var/log/vbox-install.log
Makefile:170: Warning: using /usr/src/linux as the source directory of your Linux kernel. If this is not correct, specify KERN_DIR=<directory> and run Make again.
make KBUILD_VERBOSE=1 SUBDIRS=/tmp/vbox.0 SRCROOT=/tmp/vbox.0 -C /usr/src/linux modules
test -e include/generated/autoconf.h -a -e include/config/auto.conf || (        \
        echo;                                                           \
        echo "  ERROR: Kernel configuration is invalid.";               \
        echo "         include/generated/autoconf.h or include/config/auto.conf are missing.";\
        echo "         Run 'make oldconfig && make prepare' on kernel src to fix it.";  \
        echo;                                                           \
        /bin/false)
mkdir -p /tmp/vbox.0/.tmp_versions ; rm -f /tmp/vbox.0/.tmp_versions/*

  WARNING: Symbol version dump /c/.vbox/linux-2.6.37.5/Module.symvers
           is missing; modules will have no dependencies and modversions.

make -f scripts/Makefile.build obj=/tmp/vbox.0
  gcc -Wp,-MD,/tmp/vbox.0/linux/.SUPDrv-linux.o.d  -nostdinc -isystem /usr/lib/gcc/i486-linux-gnu/4.1.2/include -I/c/.vbox/linux-2.6.37.5/arch/x86/include -Iinclude  -include include/generated/autoconf.h -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -fno-delete-null-pointer-checks -O2 -m64 -mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_FXSAVEQ=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -g -Wdeclaration-after-statement -Wno-pointer-sign -I/usr/src/linux/include -I/tmp/vbox.0/ -I/tmp/vbox.0/include -I/tmp/vbox.0/r0drv/linux -I/tmp/vbox.0/vboxdrv/ -I/tmp/vbox.0/vboxdrv/include -I/tmp/vbox.0/vboxdrv/r0drv/linux -D__KERNEL__ -DMODULE -DRT_OS_LINUX -DIN_RING0 -DIN_RT_R0 -DIN_SUP_R0 -DVBOX -DRT_WITH_VBOX -DVBOX_WITH_HARDENING -DCONFIG_VBOXDRV_AS_MISC -DRT_ARCH_AMD64 -DVBOX_WITH_64_BITS_GUESTS  -DMODULE  -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(SUPDrv_linux)"  -D"KBUILD_MODNAME=KBUILD_STR(vboxdrv)" -c -o /tmp/vbox.0/linux/.tmp_SUPDrv-linux.o /tmp/vbox.0/linux/SUPDrv-linux.c
/bin/sh: scripts/genksyms/genksyms: No such file or directory
make[2]: *** [/tmp/vbox.0/linux/SUPDrv-linux.o] Error 1
make[1]: *** [_module_/tmp/vbox.0] Error 2
make: *** [vboxdrv] Error 2
frodo:/c/.vbox#