title: GPT FileSystem after exiting boot services in C/C++
body: <p>I am creating an operating system and have strugled to find a way to implement a filesystem into it for the past several months. I can read files in boot services but after exiting boot services in UEFI the function can't read the file. I am trying to create a filesystem driver outside boot services using GPT (though if possible MBR but based on what I've seen near impossible). All source code and examples I've seen use multiboot with GRUB but I do not use the GRUB bootloader. Instead I followed the one from Poncho's OSDev 2 series. I have seen an example from WYOOS where he uses the MSDos partition system but it depends on multiboot therefore it doesn't work in my scenario. All help will be appreciated. Thanks.</p>