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Step 1. Install tools and libraries needed for coreboot. Depending on your distribution you have installed the minimum additional software requirements to continue with downloading and building coreboot. Not every distribution has the tools, that would be required, installed by default. In the following we shortly introduce the purpose of the installed packages: build-essential or base-devel are the basic tools for building software, git is needed to download coreboot from the coreboot git repository, libncurses5-dev or ncurses is needed to build the menu for 'make menuconfig', m4, bison, curl, flex, zlib1g-dev, gcc, gnat and g++ or clang are needed to build the coreboot toolchain. gcc and gnat have to be of the same version. If you started with a different distribution or package management system you might need to install other packages. Most likely they are named slightly different. If that is the case for you, we'd like to encourage you to contribute to the project and submit a pull request with an update for this documentation for your system. |
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Step 2. Download coreboot source tree. This will download a 'read-only' copy of the coreboot tree. This just means that if you made changes to the coreboot tree, you couldn't immediately contribute them back to the community. To pull a copy of coreboot that would allow you to contribute back, you would first need to sign up for an account on gerrit. |
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Step 3. Build the coreboot toolchain. This builds one of the coreboot cross-compiler toolchains for X86 platforms. Because of the variability of compilers and the other required tools between the various operating systems that coreboot can be built on, coreboot supplies and uses its own cross-compiler toolchain to build the binaries that end up as part of the coreboot ROM. The toolchain provided by the operating system (the 'host toolchain') is used to build various tools that will run on the local system during the build process. |
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Step 4. Build the payload - coreinfo. To actually do anything useful with coreboot, you need to build a payload to include into the rom. The idea behind coreboot is that it does the minimum amount possible before passing control of the machine to a payload. There are various payloads such as grub or SeaBIOS that are typically used to boot the operating system. Instead, we used coreinfo, a small demonstration payload that allows the user to look at various things such as memory and the contents of the coreboot file system (CBFS) - the pieces that make up the coreboot rom. |
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Step 5. Configure the build. This step configures coreboot's build options using the menuconfig interface to Kconfig. Kconfig is the same configuration program used by the linux kernel. It allows you to enable, disable, and change various values to control the coreboot build process, including which mainboard(motherboard) to use, which toolchain to use, and how the runtime debug console should be presented and saved. Anytime you change mainboards in Kconfig, you should always run make distclean before running make menuconfig. Due to the way that Kconfig works, values will be kept from the previous mainboard if you skip the clean step. This leads to a hybrid configuration which may or may not work as expected. |
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Step 6. Build coreboot. You may notice that a number of other pieces are downloaded at the beginning of the build process. These are the git submodules used in various coreboot builds. By default, the blobs submodule is not downloaded. This git submodule may be required for other builds for microcode or other binaries. To enable downloading this submodule, select the option "Allow use of binary-only repository" in the "General Setup" menu of Kconfig This attempts to build the coreboot rom. The rom file itself ends up in the build directory as 'coreboot.rom'. At the end of the build process, the build displayed the contents of the rom file. |
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Step 7. Install QEMU. QEMU is a processor emulator which we can use to show the coreboot boot process in a virtualised environment. |
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Step 8. Run QEMU. Here's the command line instruction broken down: qemu-system-x86_64 This starts the QEMU emulator with the i440FX host PCI bridge and PIIX3 PCI to ISA bridge, -bios build/coreboot.rom Use the coreboot rom image that we just built. If this flag is left out, the standard SeaBIOS image that comes with QEMU is used, -serial stdio Send the serial output to the console. This allows you to view the coreboot boot log. |
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