uefi: fs: Implement exists

library/std/src/sys/pal/uefi/fs.rs

@@ -311,8 +311,13 @@ pub fn remove_dir_all(_path: &Path) -> io::Result<()> {
     unsupported()
 }
 
-pub fn exists(_path: &Path) -> io::Result<bool> {
-    unsupported()
+pub fn exists(path: &Path) -> io::Result<bool> {
+    let f = uefi_fs::File::from_path(path, r_efi::protocols::file::MODE_READ, 0);
+    match f {
+        Ok(_) => Ok(true),
+        Err(e) if e.kind() == io::ErrorKind::NotFound => Ok(false),
+        Err(e) => Err(e),
+    }
 }
 
 pub fn readlink(_p: &Path) -> io::Result<PathBuf> {
@@ -342,3 +347,122 @@ pub fn canonicalize(_p: &Path) -> io::Result<PathBuf> {
 pub fn copy(_from: &Path, _to: &Path) -> io::Result<u64> {
     unsupported()
 }
+
+mod uefi_fs {
+    use r_efi::protocols::{device_path, file, simple_file_system};
+
+    use super::super::helpers;
+    use crate::boxed::Box;
+    use crate::io;
+    use crate::mem::MaybeUninit;
+    use crate::path::Path;
+    use crate::ptr::NonNull;
+
+    pub(crate) struct File(NonNull<file::Protocol>);
+
+    impl File {
+        pub(crate) fn from_path(path: &Path, open_mode: u64, attr: u64) -> io::Result<Self> {
+            let absoulte = crate::path::absolute(path)?;
+
+            let p = helpers::OwnedDevicePath::from_text(absoulte.as_os_str())?;
+            let (vol, mut path_remaining) = Self::open_volume_from_device_path(p.borrow())?;
+
+            vol.open(&mut path_remaining, open_mode, attr)
+        }
+
+        fn open_volume_from_device_path(
+            path: helpers::BorrowedDevicePath<'_>,
+        ) -> io::Result<(Self, Box<[u16]>)> {
+            let handles = match helpers::locate_handles(simple_file_system::PROTOCOL_GUID) {
+                Ok(x) => x,
+                Err(e) => return Err(e),
+            };
+            for handle in handles {
+                let volume_device_path: NonNull<device_path::Protocol> =
+                    match helpers::open_protocol(handle, device_path::PROTOCOL_GUID) {
+                        Ok(x) => x,
+                        Err(_) => continue,
+                    };
+                let volume_device_path = helpers::BorrowedDevicePath::new(volume_device_path);
+
+                if let Some(left_path) = path_best_match(&volume_device_path, &path) {
+                    return Ok((Self::open_volume(handle)?, left_path));
+                }
+            }
+
+            Err(io::const_error!(io::ErrorKind::NotFound, "Volume Not Found"))
+        }
+
+        // Open volume on device_handle using SIMPLE_FILE_SYSTEM_PROTOCOL
+        fn open_volume(device_handle: NonNull<crate::ffi::c_void>) -> io::Result<Self> {
+            let simple_file_system_protocol = helpers::open_protocol::<simple_file_system::Protocol>(
+                device_handle,
+                simple_file_system::PROTOCOL_GUID,
+            )?;
+
+            let mut file_protocol: MaybeUninit<*mut file::Protocol> = MaybeUninit::uninit();
+            let r = unsafe {
+                ((*simple_file_system_protocol.as_ptr()).open_volume)(
+                    simple_file_system_protocol.as_ptr(),
+                    file_protocol.as_mut_ptr(),
+                )
+            };
+            if r.is_error() {
+                return Err(io::Error::from_raw_os_error(r.as_usize()));
+            }
+
+            // Since no error was returned, file protocol should be non-NULL.
+            let p = NonNull::new(unsafe { file_protocol.assume_init() }).unwrap();
+            Ok(Self(p))
+        }
+
+        fn open(&self, path: &mut [u16], open_mode: u64, attr: u64) -> io::Result<Self> {
+            let file_ptr = self.0.as_ptr();
+            let mut file_opened: MaybeUninit<*mut file::Protocol> = MaybeUninit::uninit();
+
+            let r = unsafe {
+                ((*file_ptr).open)(
+                    file_ptr,
+                    file_opened.as_mut_ptr(),
+                    path.as_mut_ptr(),
+                    open_mode,
+                    attr,
+                )
+            };
+
+            if r.is_error() {
+                return Err(io::Error::from_raw_os_error(r.as_usize()));
+            }
+
+            // Since no error was returned, file protocol should be non-NULL.
+            let p = NonNull::new(unsafe { file_opened.assume_init() }).unwrap();
+            Ok(File(p))
+        }
+    }
+
+    impl Drop for File {
+        fn drop(&mut self) {
+            let file_ptr = self.0.as_ptr();
+            let _ = unsafe { ((*self.0.as_ptr()).close)(file_ptr) };
+        }
+    }
+
+    fn path_best_match<'a>(
+        source: &helpers::BorrowedDevicePath<'a>,
+        target: &helpers::BorrowedDevicePath<'a>,
+    ) -> Option<Box<[u16]>> {
+        let mut source_iter = source.iter().take_while(|x| !x.is_end_instance());
+        let mut target_iter = target.iter().take_while(|x| !x.is_end_instance());
+
+        loop {
+            match (source_iter.next(), target_iter.next()) {
+                (Some(x), Some(y)) if x == y => continue,
+                (None, Some(y)) => {
+                    let p = y.to_path().to_text().ok()?;
+                    return helpers::os_string_to_raw(&p);
+                }
+                _ => return None,
+            }
+        }
+    }
+}

library/std/src/sys/pal/uefi/helpers.rs

@@ -14,6 +14,7 @@ use r_efi::protocols::{device_path, device_path_to_text, shell};
 
 use crate::ffi::{OsStr, OsString};
 use crate::io::{self, const_error};
+use crate::iter::Iterator;
 use crate::marker::PhantomData;
 use crate::mem::{MaybeUninit, size_of};
 use crate::os::uefi::env::boot_services;
@@ -216,6 +217,60 @@ pub(crate) fn device_path_to_text(path: NonNull<device_path::Protocol>) -> io::R
     Err(io::const_error!(io::ErrorKind::NotFound, "No device path to text protocol found"))
 }
 
+fn device_node_to_text(path: NonNull<device_path::Protocol>) -> io::Result<OsString> {
+    fn node_to_text(
+        protocol: NonNull<device_path_to_text::Protocol>,
+        path: NonNull<device_path::Protocol>,
+    ) -> io::Result<OsString> {
+        let path_ptr: *mut r_efi::efi::Char16 = unsafe {
+            ((*protocol.as_ptr()).convert_device_node_to_text)(
+                path.as_ptr(),
+                // DisplayOnly
+                r_efi::efi::Boolean::FALSE,
+                // AllowShortcuts
+                r_efi::efi::Boolean::FALSE,
+            )
+        };
+
+        let path = os_string_from_raw(path_ptr)
+            .ok_or(io::const_error!(io::ErrorKind::InvalidData, "Invalid path"))?;
+
+        if let Some(boot_services) = crate::os::uefi::env::boot_services() {
+            let boot_services: NonNull<r_efi::efi::BootServices> = boot_services.cast();
+            unsafe {
+                ((*boot_services.as_ptr()).free_pool)(path_ptr.cast());
+            }
+        }
+
+        Ok(path)
+    }
+
+    static LAST_VALID_HANDLE: AtomicPtr<crate::ffi::c_void> =
+        AtomicPtr::new(crate::ptr::null_mut());
+
+    if let Some(handle) = NonNull::new(LAST_VALID_HANDLE.load(Ordering::Acquire)) {
+        if let Ok(protocol) = open_protocol::<device_path_to_text::Protocol>(
+            handle,
+            device_path_to_text::PROTOCOL_GUID,
+        ) {
+            return node_to_text(protocol, path);
+        }
+    }
+
+    let device_path_to_text_handles = locate_handles(device_path_to_text::PROTOCOL_GUID)?;
+    for handle in device_path_to_text_handles {
+        if let Ok(protocol) = open_protocol::<device_path_to_text::Protocol>(
+            handle,
+            device_path_to_text::PROTOCOL_GUID,
+        ) {
+            LAST_VALID_HANDLE.store(handle.as_ptr(), Ordering::Release);
+            return node_to_text(protocol, path);
+        }
+    }
+
+    Err(io::const_error!(io::ErrorKind::NotFound, "No device path to text protocol found"))
+}
+
 /// Gets RuntimeServices.
 pub(crate) fn runtime_services() -> Option<NonNull<r_efi::efi::RuntimeServices>> {
     let system_table: NonNull<r_efi::efi::SystemTable> =
@@ -316,6 +371,10 @@ impl<'a> BorrowedDevicePath<'a> {
         Self { protocol, phantom: PhantomData }
     }
 
+    pub(crate) const fn iter(&'a self) -> DevicePathIterator<'a> {
+        DevicePathIterator::new(DevicePathNode::new(self.protocol))
+    }
+
     pub(crate) fn to_text(&self) -> io::Result<OsString> {
         device_path_to_text(self.protocol)
     }
@@ -330,6 +389,99 @@ impl<'a> crate::fmt::Debug for BorrowedDevicePath<'a> {
     }
 }
 
+pub(crate) struct DevicePathIterator<'a>(Option<DevicePathNode<'a>>);
+
+impl<'a> DevicePathIterator<'a> {
+    const fn new(node: DevicePathNode<'a>) -> Self {
+        if node.is_end() { Self(None) } else { Self(Some(node)) }
+    }
+}
+
+impl<'a> Iterator for DevicePathIterator<'a> {
+    type Item = DevicePathNode<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let cur_node = self.0?;
+
+        let next_node = unsafe { cur_node.next_node() };
+        self.0 = if next_node.is_end() { None } else { Some(next_node) };
+
+        Some(cur_node)
+    }
+}
+
+#[derive(Copy, Clone)]
+pub(crate) struct DevicePathNode<'a> {
+    protocol: NonNull<r_efi::protocols::device_path::Protocol>,
+    phantom: PhantomData<&'a r_efi::protocols::device_path::Protocol>,
+}
+
+impl<'a> DevicePathNode<'a> {
+    pub(crate) const fn new(protocol: NonNull<r_efi::protocols::device_path::Protocol>) -> Self {
+        Self { protocol, phantom: PhantomData }
+    }
+
+    pub(crate) const fn length(&self) -> u16 {
+        let len = unsafe { (*self.protocol.as_ptr()).length };
+        u16::from_le_bytes(len)
+    }
+
+    pub(crate) const fn node_type(&self) -> u8 {
+        unsafe { (*self.protocol.as_ptr()).r#type }
+    }
+
+    pub(crate) const fn sub_type(&self) -> u8 {
+        unsafe { (*self.protocol.as_ptr()).sub_type }
+    }
+
+    pub(crate) const fn is_end(&self) -> bool {
+        self.node_type() == r_efi::protocols::device_path::TYPE_END
+            && self.sub_type() == r_efi::protocols::device_path::End::SUBTYPE_ENTIRE
+    }
+
+    pub(crate) const fn is_end_instance(&self) -> bool {
+        self.node_type() == r_efi::protocols::device_path::TYPE_END
+            && self.sub_type() == r_efi::protocols::device_path::End::SUBTYPE_INSTANCE
+    }
+
+    pub(crate) unsafe fn next_node(&self) -> Self {
+        let node = unsafe {
+            self.protocol
+                .cast::<u8>()
+                .add(self.length().into())
+                .cast::<r_efi::protocols::device_path::Protocol>()
+        };
+        Self::new(node)
+    }
+
+    pub(crate) fn to_path(&'a self) -> BorrowedDevicePath<'a> {
+        BorrowedDevicePath::new(self.protocol)
+    }
+}
+
+impl<'a> PartialEq for DevicePathNode<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        let self_len = self.length();
+        let other_len = other.length();
+
+        self_len == other_len
+            && unsafe {
+                compiler_builtins::mem::memcmp(
+                    self.protocol.as_ptr().cast(),
+                    other.protocol.as_ptr().cast(),
+                    usize::from(self_len),
+                ) == 0
+            }
+    }
+}
+
+impl<'a> crate::fmt::Debug for DevicePathNode<'a> {
+    fn fmt(&self, f: &mut crate::fmt::Formatter<'_>) -> crate::fmt::Result {
+        let p = device_node_to_text(self.protocol).unwrap();
+        p.fmt(f)
+    }
+}
+
 pub(crate) struct OwnedProtocol<T> {
     guid: r_efi::efi::Guid,
     handle: NonNull<crate::ffi::c_void>,