169 lines
6.8 KiB
Markdown
169 lines
6.8 KiB
Markdown
coreboot lesson 1 - Starting from scratch
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=========================================
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From a fresh Ubuntu 16.04 or 18.04 install, here are all the steps required for
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a very basic build:
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Download, configure, and build coreboot
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---------------------------------------
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### Step 1 - Install tools and libraries needed for coreboot
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$ sudo apt-get install -y bison build-essential curl flex git gnat-5 libncurses5-dev m4 zlib1g-dev
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### Step 2 - Download coreboot source tree
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$ git clone https://review.coreboot.org/coreboot
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$ cd coreboot
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### Step 3 - Build the coreboot toolchain
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Please note that this can take a significant amount of time
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$ make crossgcc-i386 CPUS=$(nproc)
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Also note that you can possibly use your system toolchain, but the results are
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not reproducible, and may have issues, so this is not recommended. See step 5
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to use your system toolchain.
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### Step 4 - Build the payload - coreinfo
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$ make -C payloads/coreinfo olddefconfig
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$ make -C payloads/coreinfo
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### Step 5 - Configure the build
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##### Configure your mainboard
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$ make menuconfig
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select 'Mainboard' menu
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Beside 'Mainboard vendor' should be '(Emulation)'
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Beside 'Mainboard model' should be 'QEMU x86 i440fx/piix4'
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select < Exit >
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These should be the default selections, so if anything else was set, run
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`make distclean` to remove your old config file and start over.
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##### Optionally use your system toolchain (Again, not recommended)
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select 'General Setup' menu
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select 'Allow building with any toolchain'
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select < Exit >
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##### Select the payload
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select 'Payload' menu
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select 'Add a Payload'
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choose 'An Elf executable payload'
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select 'Payload path and filename'
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enter 'payloads/coreinfo/build/coreinfo.elf'
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select < Exit >
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select < Exit >
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select < Yes >
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##### check your configuration (optional step):
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$ make savedefconfig
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$ cat defconfig
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There should only be two lines (or 3 if you're using the system toolchain):
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CONFIG_PAYLOAD_ELF=y
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CONFIG_PAYLOAD_FILE="payloads/coreinfo/build/coreinfo.elf"
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### Step 6 - build coreboot
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$ make
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At the end of the build, you should see:
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Build emulation/qemu-i440fx (QEMU x86 i440fx/piix4)
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This means your build was successful. The output from the build is in the build
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directory. build/coreboot.rom is the full rom file.
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Test the image using QEMU
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-------------------------
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### Step 7 - Install QEMU
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$ sudo apt-get install -y qemu
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### Step 8 - Run QEMU
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Start QEMU, and point it to the ROM you just built:
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$ qemu-system-x86_64 -bios build/coreboot.rom -serial stdio
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You should see the serial output of coreboot in the original console window, and
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a new window will appear running the coreinfo payload.
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Summary
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-------
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### Step 1 summary - Install tools and libraries needed for coreboot
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You installed the minimum additional requirements for ubuntu to download and
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build coreboot. Ubuntu already has most of the other tools that would be
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required installed by default.
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* `build-essential` is the basic tools for doing builds. It comes pre-installed
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on some Ubuntu flavors, and not on others.
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* `git` is needed to download coreboot from the coreboot git repository.
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* `libncurses5-dev` is needed to build the menu for 'make menuconfig'
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* `m4, bison, curl, flex, gnat-5, zlib1g-dev` are needed to build the coreboot
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toolchain.
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If you started with a different distribution, you might need to install many
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other items which vary by distribution.
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### Step 2 summary - Download coreboot source tree
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This will download a 'read-only' copy of the coreboot tree. This just means
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that if you made changes to the coreboot tree, you couldn't immediately
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contribute them back to the community. To pull a copy of coreboot that would
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allow you to contribute back, you would first need to sign up for an account on
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gerrit.
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### Step 3 summary - Build the coreboot toolchain.
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This builds one of the coreboot cross-compiler toolchains for X86 platforms.
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Because of the variability of compilers and the other required tools between
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the various operating systems that coreboot can be built on, coreboot supplies
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and uses its own cross-compiler toolchain to build the binaries that end up as
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part of the coreboot ROM. The toolchain provided by the operating system (the
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'host toolchain') is used to build various tools that will run on the local
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system during the build process.
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### Step 4 summary - Build the payload
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To actually do anything useful with coreboot, you need to build a payload to
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include in the rom. The idea behind coreboot is that it does the minimum amount
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possible before passing control of the machine to a payload. There are various
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payloads such as grub or SeaBIOS that are typically used to boot the operating
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system. Instead, we used coreinfo, a small demonstration payload that allows the
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user to look at various things such as memory and the contents of coreboot's
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cbfs - the pieces that make up the coreboot rom.
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### Step 5 summary - Configure the build
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This step configures coreboot's build options using the menuconfig interface to
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Kconfig. Kconfig is the same configuration program used by the linux kernel. It
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allows you to enable, disable, and change various values to control the coreboot
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build process, including which mainboard(motherboard) to use, which toolchain to
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use, and how the runtime debug console should be presented and saved.
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Anytime you change mainboards in Kconfig, you should always run `make distclean`
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before running `make menuconfig`. Due to the way that Kconfig works, values will
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be kept from the previous mainboard if you skip the clean step. This leads to a
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hybrid configuration which may or may not work as expected.
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### Step 6 summary - Build coreboot
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You may notice that a number of other pieces are downloaded at the beginning of
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the build process. These are the git submodules used in various coreboot builds.
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By default, the BLOBS submodule is not downloaded. This git submodule may be
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required for other builds for microcode or other binaries. To enable downloading
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this submodule, select the option "Allow use of binary-only repository" in the
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"General Setup" menu of Kconfig
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This attempts to build the coreboot rom. The rom file itself ends up in the
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build directory as 'coreboot.rom'. At the end of the build process, the build
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displayed the contents of the rom file.
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### Step 7 summary - Install QEMU
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QEMU is a processor emulator which we can use to show coreboot
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### Step 8 summary - Run QEMU
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Here's the command line broken down:
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* `qemu-system-x86_64`
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This starts the QEMU emulator with the i440FX host PCI bridge and PIIX3 PCI to
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ISA bridge.
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* `-bios build/coreboot.rom`
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Use the bios rom image that we just built. If this is left off, the standard
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SeaBIOS image that comes with QEMU is used.
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* `-serial stdio`
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Send the serial output to the console. This allows you to view the coreboot
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debug output.
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