BOOTBOOT: Difference between revisions

Optionally you can load your OS from ROM (see qemu's -option-rom command line argument, or bochs rc file; or with [https://coreboot.org coreboot] as a BIOS using qemu -bios), and the Raspberry Pi version can also load the ramdisk over serial line. Although it's not implemented as of yet, the BOOTBOOT protocol allows loading the initrd from a TFTP server.

You can use ELF64 or PE32+ formats for your kernel. You must link it as a [[Higher Half Kernel]], and your entry point should point to [[Long Mode]] code. That's all. Unlike all the other boot protocols (e.g. [[Multiboot]] and [[stivale]]), there's absolutely no need for special sections nor for magic structs, unimplementable in some languages. No real mode nor protected mode trampoline code needed at alleither, which simplifies your build environment significantly. Example linker script provided for both x86_64 and AArch64. There are [https://gitlab.com/bztsrc/bootboot/tree/master/mykernel example kernels] forwritten in [[C]], and[[C++]], [[Pascal]], [[Ada]], [[Rust]] and [[Go]].

BOOTBOOT does not support VGA text mode, it sets up graphic mode regardless to the platform. You don't have to mess around with [[VESA]] or [[GOP]] any more, you will get the frame buffer ready to use. The example Hello World kernel provided with the BOOTBOOT source has a minimal puts() example, which outputs text on that frame buffer using [[PC Screen Font]] (same that Linux Console uses). You can also use the [[Scalable Screen Font]] library's ''ssfn_putc()''.