ZeroOS/src/fs/uefi.rs

use core::ffi::c_void;

use crate::efi::{
    EFI_LOADED_IMAGE_PROTOCOL_GUID, EFI_NOT_FOUND, EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID,
    EFI_SUCCESS, EfiBootServices, EfiGuid, EfiHandle, EfiLoadedImageProtocol, EfiStatus,
};
use crate::memory::{PAGE_SIZE, PhysicalMemoryManager};

pub const BASH_PATH: &[u16] = &[
    '\\' as u16,
    'b' as u16,
    'i' as u16,
    'n' as u16,
    '\\' as u16,
    'b' as u16,
    'a' as u16,
    's' as u16,
    'h' as u16,
    0,
];

pub const SH_PATH: &[u16] = &[
    '\\' as u16,
    'b' as u16,
    'i' as u16,
    'n' as u16,
    '\\' as u16,
    's' as u16,
    'h' as u16,
    0,
];

const EFI_FILE_MODE_READ: u64 = 1;
const EFI_FILE_INFO_GUID: EfiGuid = EfiGuid::new(
    0x09576e92,
    0x6d3f,
    0x11d2,
    [0x8e, 0x39, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b],
);

pub struct LoadedFile {
    pub ptr: *const u8,
    pub len: usize,
}

#[repr(C)]
struct EfiSimpleFileSystemProtocol {
    revision: u64,
    open_volume: extern "efiapi" fn(
        this: *mut EfiSimpleFileSystemProtocol,
        root: *mut *mut EfiFileProtocol,
    ) -> EfiStatus,
}

#[repr(C)]
struct EfiFileProtocol {
    revision: u64,
    open: extern "efiapi" fn(
        this: *mut EfiFileProtocol,
        new_handle: *mut *mut EfiFileProtocol,
        file_name: *const u16,
        open_mode: u64,
        attributes: u64,
    ) -> EfiStatus,
    close: extern "efiapi" fn(this: *mut EfiFileProtocol) -> EfiStatus,
    delete: usize,
    read: extern "efiapi" fn(
        this: *mut EfiFileProtocol,
        buffer_size: *mut usize,
        buffer: *mut c_void,
    ) -> EfiStatus,
    write: usize,
    get_position: usize,
    set_position: usize,
    get_info: extern "efiapi" fn(
        this: *mut EfiFileProtocol,
        information_type: *const EfiGuid,
        buffer_size: *mut usize,
        buffer: *mut c_void,
    ) -> EfiStatus,
}

#[repr(C)]
struct EfiFileInfoPrefix {
    size: u64,
    file_size: u64,
    physical_size: u64,
}

pub unsafe fn load_file(
    image_handle: EfiHandle,
    boot_services: *mut EfiBootServices,
    memory: &mut PhysicalMemoryManager,
    path: &[u16],
) -> Option<LoadedFile> {
    let mut loaded_image = core::ptr::null_mut();
    let status = unsafe {
        ((*boot_services).handle_protocol)(
            image_handle,
            &EFI_LOADED_IMAGE_PROTOCOL_GUID,
            &mut loaded_image,
        )
    };
    if status != EFI_SUCCESS || loaded_image.is_null() {
        return None;
    }

    let loaded_image = loaded_image as *mut EfiLoadedImageProtocol;
    let mut fs = core::ptr::null_mut();
    let status = unsafe {
        ((*boot_services).handle_protocol)(
            (*loaded_image).device_handle,
            &EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID,
            &mut fs,
        )
    };
    if status != EFI_SUCCESS || fs.is_null() {
        return None;
    }

    let fs = fs as *mut EfiSimpleFileSystemProtocol;
    let mut root = core::ptr::null_mut();
    let status = unsafe { ((*fs).open_volume)(fs, &mut root) };
    if status != EFI_SUCCESS || root.is_null() {
        return None;
    }

    let mut file = core::ptr::null_mut();
    let status = unsafe { ((*root).open)(root, &mut file, path.as_ptr(), EFI_FILE_MODE_READ, 0) };
    unsafe {
        ((*root).close)(root);
    }
    if status == EFI_NOT_FOUND || status != EFI_SUCCESS || file.is_null() {
        return None;
    }

    let size = unsafe { file_size(file)? };
    let pages = size.div_ceil(PAGE_SIZE).max(1);
    let buffer = memory.alloc_pages(pages)?;
    let mut read_len = size;
    let status = unsafe { ((*file).read)(file, &mut read_len, buffer.cast::<c_void>()) };
    unsafe {
        ((*file).close)(file);
    }

    if status != EFI_SUCCESS || read_len == 0 {
        unsafe {
            memory.free_pages(buffer, pages);
        }
        return None;
    }

    Some(LoadedFile {
        ptr: buffer as *const u8,
        len: read_len,
    })
}

unsafe fn file_size(file: *mut EfiFileProtocol) -> Option<usize> {
    let mut info_buffer = [0u8; 1024];
    let mut info_size = info_buffer.len();
    let status = unsafe {
        ((*file).get_info)(
            file,
            &EFI_FILE_INFO_GUID,
            &mut info_size,
            info_buffer.as_mut_ptr().cast::<c_void>(),
        )
    };
    if status != EFI_SUCCESS {
        return None;
    }
    if info_size < core::mem::size_of::<EfiFileInfoPrefix>() {
        return None;
    }

    let info = unsafe { &*(info_buffer.as_ptr() as *const EfiFileInfoPrefix) };
    usize::try_from(info.file_size).ok()
}