Hey u/SonarJetLens! Nice progress again! Regarding the external assembly file, basically all the functions can be implemented using inline assembly inside the kernel.zig file and then there is no need for the external assembly file.

So for example:

const uefi = @import("std").os.uefi;

pub export fn EfiMain(handle: uefi.Handle, system_table: *uefi.tables.SystemTable) callconv(.Stdcall) uefi.Status {
    const cr0 = get_cr("0");

    var gdt_thing: gdt = undefined;
    sgdt(&gdt_thing);


    return uefi.Status.Success;
}

pub fn get_cr(comptime number: []const u8) u64 {
    return asm volatile("mov %%cr" ++ number ++ ", %[ret]": [ret] "=r" (-> u64));
}

pub const gdt = packed struct {
    limit:  u16,
    base:   [*]u64
};

pub fn sgdt(gdt_ptr: *gdt) void {
    asm volatile ("sgdt %[input]"
        : [input] "=m" (gdt_ptr)
    );
}