mirror of
https://gitlab.com/bztsrc/bootboot.git
synced 2023-02-13 20:54:32 -05:00
107 lines
3.8 KiB
Markdown
107 lines
3.8 KiB
Markdown
BOOTBOOT Coreboot x86_64 Implementation
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=======================================
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See [BOOTBOOT Protocol](https://gitlab.com/bztsrc/bootboot) for common details.
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Implements the BOOTBOOT Protocol as a [coreboot](https://coreboot.org) payload.
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Must be compiled using the coreboot build environment.
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Compilation
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-----------
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### Step 1 - Install dependencies
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First, install the [coreboot dependencies](https://doc.coreboot.org/tutorial/part1.html): bison, build-essentials, curl,
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flex, git, gnat, libncurses5-dev, m4, zlib. Please refer to the linked doc for up-to-date list of dependencies.
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### Step 2 - Get coreboot
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Download coreboot and its submodules
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```sh
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$ git clone https://review.coreboot.org/coreboot
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$ cd coreboot
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$ git submodule update --init
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```
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It is very important to initialize submodules, otherwise you won't be able to compile coreboot.
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### Step 3 - Create toolchain
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This step could take a while. Replace *$(nproc)* with the number of CPU cores you have.
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```sh
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$ make crossgcc-i386 CPUS=$(nproc)
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```
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### Step 4 - Configure
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Now configure coreboot for your motherboard (or qemu) and BOOTBOOT.
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```sh
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$ 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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select 'Devices' menu
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select 'Display' menu
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Beside 'Framebuffer mode' should be 'Linear "high-resolution" framebuffer'
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select 'Exit'
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select 'Exit'
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select 'Payload' menu
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select 'Add a Payload'
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choose 'BOOTBOOT'
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select 'Exit'
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select 'Exit'
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select 'Yes'
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```
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It is important to set the display to "linear framebuffer", because BOOTBOOT does not handle the legacy, non-portable VGA
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text mode. Sadly there's no way of configuring this in run-time with libpayload.
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### Step 5 - Build coreboot
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```sh
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$ make
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```
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### Step 6 - Test the newly compiled ROM in QEMU
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For more information, read the [coreboot docs](https://doc.coreboot.org/mainboard/emulation/qemu-i440fx.html). In the
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[images](https://gitlab.com/bztsrc/bootboot/tree/binaries/images) directory you can find a precompiled coreboot-x86.rom binary.
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```sh
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$ qemu-system-x86_64 -bios build/coreboot.rom -drive file=$(BOOTBOOT)/images/disk-x86.img,format=raw -serial stdio
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```
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Adding Initrd to ROM
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--------------------
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To add an initrd into ROM, first you have to generate one. It can be an (optionally gzipped) tar, cpio, etc. archive. You can
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also create it using the [mkbootimg](https://gitlab.com/bztsrc/bootboot/tree/master/mkbootimg) utility:
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```sh
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$ ./mkbootimg myos.json initrd.bin
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```
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Then use the `cbfstool` utility in the coreboot repository to add the initrd image into the ROM image:
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```sh
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$ ./build/cbfstool build/coreboot.rom add -t raw -f $(BOOTBOOT)/initrd.bin -n bootboot/initrd
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```
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You can add a fallback environment configuration similarily (only used if environment cannot be loaded from the usual places):
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```sh
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$ ./build/cbfstool build/coreboot.rom add -t raw -f $(BOOTBOOT)/environment.txt -n bootboot/config
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```
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Obviously this can only work if libpayload was compiled with `CONFIG_LP_CBFS=y`. Without you can still place the initrd on
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a Flashmap partition named "INITRD" (however using the fmaptool and dealing with the fmd format is a rocket science).
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Machine state
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-------------
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IRQs masked. GDT unspecified, but valid, IDT unset. SSE, SMP enabled. Code is running in supervisor mode in ring 0 on all cores.
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Installation
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------------
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Once you have compiled a coreboot ROM with the BOOTBOOT payload, you can
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[flash the build/coreboot.rom](https://doc.coreboot.org/flash_tutorial/index.html) file to your mainboard.
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Limitations
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-----------
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- The CMOS nvram does not store timezone, so always GMT+0 returned in bootboot.timezone.
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- Coreboot does not provide a way to set screen resolution, so "screen=" config option is not used.
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- Only supports SHA-XOR-CBC, no AES
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