The Linux kernel
From IGEP - ISEE Wiki
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Contents
What is Linux?
It has all the features you would expect in a modern fully-fledged Unix, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management, and multistack networking including IPv4 and IPv6.
Although originally developed first for 32-bit x86-based PCs (386 or higher), today Linux also runs on a multitude of other processor architectures, in both 32- and 64-bit variants.
Overview of How-To
This How-To is meant to be a starting point for people to learn build a kernel image for IGEP Processor Boards as quickly and easily as possible.
How to cross compile the linux kernel
In order to build the Linux Kernel for IGEP PROCESSOR BOARDS it's recommended to cross-compile the kernel, that's, build the kernel in your HOST machine for a target architecture.
To setup the cross-compiling there are two fundamental variables that the kernel uses to select the target architecture. Normally these values are guessed based on your build environment, but of course that environment here does not match our target embedded system, so we'll need to override them. The variables in question are ARCH and CROSS_COMPILE.
The ARCH variable is the architecture you're targetting as the kernel knows it. For IGEP PROCESSOR BOARDS you'll set to "arm" architecture.
Hopefully the CROSS_COMPILE variable is pretty self-explanatory. Set this to the prefix of your toolchain (including the trailing dash "-"). So if your toolchain is invoked as say arm-linux-gnueabi-gcc, just chop off that trailing gcc and that's what you use: arm-linux-gnu-.
There is an additional variable, INSTALL_MOD_PATH, which defines where the /lib directory will be created, and all the modules stored. While you don't have to transfer the kernel sources to your target device, if you build any modules, you'll want this directory.
As example, once you've downloaded the kernel source, you should follow these steps:
make ARCH=arm CROSS_COMPILE=[cross compiler] [defconfig] make ARCH=arm CROSS_COMPILE=[cross compiler] zImage modules
The result will be a zImage file in arch/arm/boot directory. You can install the kernel modules to your target rootfs
make ARCH=arm CROSS_COMPILE=[cross compiler] modules_install INSTALL_MOD_PATH=[path to your target rootfs]
Stable kernels
NOTE: These are the kernels considered stable and recommended for normal use. CHOOSE YOUR KERNEL BASED ON THE SUPPORTED PLATFORM
Linux 2.6.37.y series
The 2.6.37.y kernel series are supported by IGEP PROCESSOR BOARDS based on:
- omap3.png
See the Linux Kernel 2.6.37.y article
Unstable kernels
NOTE: These kernel series are where the development work takes place and you should use this if you're after to work with the latest cutting edge developments. It is possible trunk can suffer temporary periods of instability while new features are developed and if this is undesirable we recommend using one of the release branches. USE AT YOUR OWN RISK
Linux 3.8.y series
The 3.8.y kernel series are supported by IGEP PROCESSOR BOARDS based on:
- am335x.png
See the Linux Kernel 3.8.y article
Linux mainline series
The mainline series are supported by IGEP Platforms based on:
- omap3.png
- am335x.png
- omap5.png
See the Linux Kernel Mainline article
End Of Life kernels (EOL)
An "End of Life" kernel means that its support will stop and all the users are urged to upgrade to a new version.Life-EOL.png?1368432307
Linux 2.6.35.y series
NOTE: These kernel series are end-of-life, dead, gone, buried ..., please move to the v2.6.37 kernel series at this time.
The 2.6.35.y kernel series are supported by IGEP PROCESSOR BOARDS based on:
- omap3.png
See the Linux Kernel 2.6.35.y article.
