Board & processor configuration:
uclinux/linux-2.4.x/arch/armnommu/config.in

In the "System" menu, add the board to be supported in the "ARM system type" selection. In this case an option ACME is added and CONFIG_ARCH_ACME defined.

Next, some of the defaults for the processor and board are defined. These options will have to be selected based on the processor characteristics. Some of the other processor configurations in the file can be used as examples.

Here, the processor clock is defined at 60Mhz, and the RAM and ROM (flash) configuration is set for this particular board. Additional options such as CONFIG_SERIAL_44B0 force the inclusion of corresponding device drivers in the linux build process.

uclinux/linux-2.4.x/arch/armnommu/Makefile

In the architecture specific Makefile, two variables need to be set. The variable TEXTADDR refers to the target location in DRAM where the final binary will be loaded and executed. Linking by the compiler is done with reference to this location. This is usually at the top of DRAM at a 32-bit aligned address. In this case, the binary is loaded at offset 0x8000 into the DRAM base address 0x0c000000. The first 32k bytes of DRAM are used to store interrupt vectors, and to pass bootup parameters to uClinux from the bootloader.

The variable MACHINE defines the directories where the processor specific files will be created, in this case: uclinux/linux-2.4.x/arch/armnommu/mach-s3c44b0x/ and uclinux/linux-2.4.x/include/asm-armnommu/arch-s3c44b0x/

uclinux/linux-2.4.x/arch/armnommu/tools/mach-types

This file holds a database of machine type macros and their numbers. A new machine requires a unique number, which is alloted by the ARM maintainers. To register, follow the steps detailed in uclinux/linux-2.4.x/Documentation/arm/README. Temporarily, add a new line as shown. Select the same name (ARCH_ACME) as was used in config.in to describe the machine configuration. A unique number will also have to be selected.

# machine_is_xxx        CONFIG_xxxx        MACH_TYPE_xxx        number
 acme        ARCH_ACME        ACME        350

Generate the header file using the script in the tools directory by executing "awk -f gen-mach-types mach-types > mach-types.h". Finally, move mach-types.h to uclinux/linux-2.4.x/include/asm-armnommu/mach-types.h

uclinux/linux-2.4.x/arch/armnommu/vmlinux-armv.lds.in

The linker script for the 32-bit processor is vmlinux-armv.lds.in. An important section to consider here is the ROM filesystem storage location. The resultant binary after the uClinux build process is a combination of the uClinux kernel and a filesystem containing selected utilities. Typically the filesystem is a ROMFS and is loaded into DRAM. There are two ways to include the filesystem image in the uClinux binary, either concatenated with the uClinux kernel, or included in the kernel itself. The former case requires movement of the filesystem into the appropriate location in DRAM, while the latter requires no such code during startup. The following code is added at the end of the .text section:

The romfs image romfs.o is written at the location romfs_data in the final binary. This variable is referenced in the blkmem driver.

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