If you've installed the Linux kernel that comes with HardHat, then cross-compiling should already be enabled in the kernel Makefile. If your kernel is not from the HardHat CD, you should enable cross-compiling in the Makefile by defining a CROSS_COMPILE entry in the following manner: (a code segment from the main Makefile)

CROSS_COMPILE 	= /opt/hardhat/devkit/ppc/7xx/bin/ppc_7xx-
AS		= $(CROSS_COMPILE)as
LD		= $(CROSS_COMPILE)ld
CC		= $(CROSS_COMPILE)gcc

The Linux kernel is modular, and allows you to configure it and choose which “blocks” should be compiled with the kernel. In order to do this, first cd /usr/src/linux (assuming your kernel source code is installed at /usr/src/linux). Once there, type make xconfig.After saving your options, you should make vmlinux to create a kernel image suitably for using with VisionICE.

We will not go into more details here, as it's outside the scope of this document. For more information, try http://www.tldp.org/HOWTO/Kernel-HOWTO.html