You should enable -g (or higher) for debugging!
 * CPV:  app-emulation/virtualbox-modules-3.2.6
 * REPO: gentoo
 * USE:  elibc_glibc kernel_linux userland_GNU x86
 * Determining the location of the kernel source code
 * Found kernel source directory:
 *     /usr/src/linux
 * Found sources for kernel version:
 *     2.6.33-gentoo-r1
>>> Unpacking source...
>>> Unpacking vbox-kernel-module-src-3.2.6.tar.bz2 to /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work
>>> Source unpacked in /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work
>>> Preparing source in /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work ...
>>> Source prepared.
>>> Configuring source in /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work ...
>>> Source configured.
>>> Compiling source in /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work ...
ln: creating symbolic link `Module.symvers': File exists
 * Preparing vboxdrv module
make -j3 HOSTCC=i686-pc-linux-gnu-gcc CROSS_COMPILE=i686-pc-linux-gnu- LDFLAGS= KERN_DIR=/usr/src/linux KERNOUT=/usr/src/linux all 
*** Building 'vboxdrv' module ***
make[1]: Entering directory `/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv'
make KBUILD_VERBOSE= -C /usr/src/linux SUBDIRS=/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv SRCROOT=/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv modules
make[2]: Entering directory `/usr/src/linux-2.6.33-gentoo-r1'
  CC [M]  /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/linux/SUPDrv-linux.o
  CC [M]  /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/SUPDrv.o
  CC [M]  /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/SUPDrvSem.o
  CC [M]  /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/alloc-r0drv.o
  CC [M]  /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/initterm-r0drv.o
In file included from include/linux/gfp.h:4,
                 from include/linux/kmod.h:22,
                 from include/linux/module.h:13,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/include/internal/iprt.h:52,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/alloc-r0drv.c:32:
include/linux/mmzone.h:18:30: error: generated/bounds.h: No such file or directory
include/linux/mmzone.h:258:5: warning: "MAX_NR_ZONES" is not defined
include/linux/mmzone.h:260:7: warning: "MAX_NR_ZONES" is not defined
include/linux/mmzone.h:262:7: warning: "MAX_NR_ZONES" is not defined
In file included from include/linux/gfp.h:4,
                 from include/linux/kmod.h:22,
                 from include/linux/module.h:13,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/include/internal/iprt.h:52,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/alloc-r0drv.c:32:
include/linux/mmzone.h:300: error: ‘MAX_NR_ZONES’ undeclared here (not in a function)
In file included from include/linux/gfp.h:4,
                 from include/linux/kmod.h:22,
                 from include/linux/module.h:13,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/include/internal/iprt.h:52,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/initterm-r0drv.c:32:
include/linux/mmzone.h:18:30: error: generated/bounds.h: No such file or directory
include/linux/mmzone.h:258:5: warning: "MAX_NR_ZONES" is not defined
include/linux/mmzone.h:260:7: warning: "MAX_NR_ZONES" is not defined
include/linux/mmzone.h:262:7: warning: "MAX_NR_ZONES" is not defined
In file included from include/linux/gfp.h:4,
                 from include/linux/kmod.h:22,
                 from include/linux/module.h:13,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/include/internal/iprt.h:52,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/initterm-r0drv.c:32:
include/linux/mmzone.h:300: error: ‘MAX_NR_ZONES’ undeclared here (not in a function)
In file included from include/linux/gfp.h:4,
                 from include/linux/slab.h:12,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/linux/../SUPDrvInternal.h:100,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/linux/SUPDrv-linux.c:33:
include/linux/mmzone.h:18:30: error: generated/bounds.h: No such file or directory
include/linux/mmzone.h:258:5: warning: "MAX_NR_ZONES" is not defined
include/linux/mmzone.h:260:7: warning: "MAX_NR_ZONES" is not defined
include/linux/mmzone.h:262:7: warning: "MAX_NR_ZONES" is not defined
In file included from include/linux/gfp.h:4,
                 from include/linux/slab.h:12,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/linux/../SUPDrvInternal.h:100,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/linux/SUPDrv-linux.c:33:
include/linux/mmzone.h:300: error: ‘MAX_NR_ZONES’ undeclared here (not in a function)
make[3]: *** [/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/initterm-r0drv.o] Error 1
make[3]: *** Waiting for unfinished jobs....
make[3]: *** [/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/alloc-r0drv.o] Error 1
In file included from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/r0drv/linux/the-linux-kernel.h:78,
                 from /var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/linux/SUPDrv-linux.c:34:
include/linux/mm.h:454:63: warning: "NR_PAGEFLAGS" is not defined
include/linux/mm.h:502:62: warning: "NR_PAGEFLAGS" is not defined
make[3]: *** [/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv/linux/SUPDrv-linux.o] Error 1
make[2]: *** [_module_/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv] Error 2
make[2]: Leaving directory `/usr/src/linux-2.6.33-gentoo-r1'
make[1]: *** [vboxdrv] Error 2
make[1]: Leaving directory `/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work/vboxdrv'
make: *** [all] Error 2
 * ERROR: app-emulation/virtualbox-modules-3.2.6 failed:
 *   Unable to emake HOSTCC=i686-pc-linux-gnu-gcc CROSS_COMPILE=i686-pc-linux-gnu- LDFLAGS=  KERN_DIR=/usr/src/linux KERNOUT=/usr/src/linux all
 * 
 * Call stack:
 *     ebuild.sh, line   47:  Called src_compile
 *   environment, line 3508:  Called linux-mod_src_compile
 *   environment, line 2700:  Called die
 * The specific snippet of code:
 *               eval "emake HOSTCC=\"$(tc-getBUILD_CC)\" 						CROSS_COMPILE=${CHOST}- 						LDFLAGS=\"$(get_abi_LDFLAGS)\" 						${BUILD_FIXES} 						${BUILD_PARAMS} 						${BUILD_TARGETS} " || die "Unable to emake HOSTCC="$(tc-getBUILD_CC)" CROSS_COMPILE=${CHOST}- LDFLAGS="$(get_abi_LDFLAGS)" ${BUILD_FIXES} ${BUILD_PARAMS} ${BUILD_TARGETS}";
 * 
 * If you need support, post the output of 'emerge --info =app-emulation/virtualbox-modules-3.2.6',
 * the complete build log and the output of 'emerge -pqv =app-emulation/virtualbox-modules-3.2.6'.
 * The complete build log is located at '/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/temp/environment'.
 * S: '/var/tmp/portage/app-emulation/virtualbox-modules-3.2.6/work'