Unable to build the vmmon module

#uname -r

2.6.20-5-generic

#cat /etc/issue

Ubuntu feisty (development branch) \n \l

\# dpkg -l |grep 2.6.20-5

ii  linux-headers-2.6.20-5                     2.6.20-5.7                           Header files related to Linux kernel version

ii  linux-headers-2.6.20-5-generic             2.6.20-5.7                           Linux kernel headers for version 2.6.20 on x

ii  linux-image-2.6.20-5-generic               2.6.20-5.7                           Linux kernel image for version 2.6.20 on x86

ii  linux-restricted-modules-2.6.20-5-generic  2.6.20.1-6                           Non-free Linux 2.6.20 modules on x86/x86_64

\# ./vmware-install.pl

Using 2.6.x kernel build system.

make: Entering directory `/tmp/vmware-config1/vmmon-only'

make -C /lib/modules/2.6.20-5-generic/build/include/.. SUBDIRS=$PWD SRCROOT=$PWD/. modules

make[1]: Entering directory `/usr/src/linux-headers-2.6.20-5-generic'

  CC   /tmp/vmware-config1/vmmon-only/linux/driver.o

In file included from /tmp/vmware-config1/vmmon-only/linux/driver.c:80:

/tmp/vmware-config1/vmmon-only/./include/compat_kernel.h:21: error: expected declaration specifiers or ‘...’ before ‘compat_exit’

/tmp/vmware-config1/vmmon-only/./include/compat_kernel.h:21: error: expected declaration specifiers or ‘...’ before ‘exit_code’

/tmp/vmware-config1/vmmon-only/./include/compat_kernel.h:21: warning: type defaults to ‘int’ in declaration of ‘_syscall1’

make[2]: *** /tmp/vmware-config1/vmmon-only/linux/driver.o Error 1

make[1]: *** \[_module_/tmp/vmware-config1/vmmon-only] Error 2

make[1]: Leaving directory `/usr/src/linux-headers-2.6.20-5-generic'

make: *** \[vmmon.ko] Error 2

make: Leaving directory `/tmp/vmware-config1/vmmon-only'

Unable to build the vmmon module.