Experimental 64-bit Operating System written in D
For x86-64
This doesn't do much yet, but has some code for formatted printing, etc. which does not rely on the GC that others may find useful. This is just for fun... for now!
My ultimate goal is to have a simple multi-threaded OS that forces strict application, user and geographic-level restrictions on resource access. Instead of a discretionary access control model based on multiple users, my objective for Fortress is to instead control what particular applications are allowed to do (like AppArmor).
Added code to use a linear framebuffer, so we are into the 20th century now with cool 1024x768x16 graphics!
Reworked memory map, got rid of recursive page mapping.
Kernel boots into higher-half.
Serial output works, and is useful for debugging when using the framebuffer instead of text output. For VirtualBox, you can enable the serial port and change port mode to "Raw File", so all of Fortress' text output goes to that file for later analysis.
Fortress is built on Linux (WSL in Windows also works). It needs a fairly
recent version of DMD (at least since -betterC was introduced). You'll also
require yasm on Linux and GNU binutils for the ld linker.
>make
To generate .iso (which could be used to burn a bootable CD-R or USB stick):
>make iso
Note that the above command relies on grub-mkrescue, which needs mtools and xorriso installed or it will silently fail to produce the .iso. "make iso" also needs the grub-pc-bin package installed to work correctly.
To launch QEMU w/ appropriate arguments for aforementioned .iso:
>make run
Or to just run off the kernel binary:
>make run-raw
It runs in VirtualBox as well, when booting from the .iso.
This is written in D using the -betterC flag to prevent use of garbage collection, but there are some other gotchas in addition to the
D symbols referenced in .asm files needs to be extern(C) __gshared
The extern(C) is so that the name is not mangled. gshared is required because thread-local storage (TLS) is not functional in the early stages of loading the kernel. The -vtls flag is passed to DMD as an extra sanity check, forgetting gshared on a global can be very frustrating to debug!
A lot of debug statements are wrapped in static if() blocks, check config.d for compile-time flags that can be set for additional debugging information.
Instead of the Intel/AMD convention of PML4E, PDPT, PDT, PD, I
call the page tables by P4, P3, P2 and P1 throughout
the code.
Entry point to kernel is boot.asm, which then calls code in trampoline.asm to jump to the kernel in higher-half memory in boot64.asm. This calls kmain in main.d, and we're in D code from this point on with some minor jaunts into asm for some help setting up interrupts, invalidating pages, reloading CR3 with a new page table, etc.
Multiboot struct saved at: 0xFFFF_8000_0001_0000
Kernel Lives at: 0xFFFF_8000_0010_0000
Linear Framebuffer (Kernel Base + wherever GRUB puts it): 0xFFFF_8000_E000_0000
From here is TBD! Next steps include working out memory allocation, userspace and filesystem.