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UEFI paths can be of 4 types: 1. Absolute Shell Path: Uses shell mappings 2. Absolute Device Path: this is what we want 3: Relative root: path relative to the current root. 4: Relative Absolute shell path can be identified with `:` and Absolute Device path can be identified with `/`. Relative root path will start with `\`. The algorithm is mostly taken from edk2 UEFI shell implementation and is somewhat simple. Check for the path type in order. For Absolute Shell path, use `EFI_SHELL->GetDevicePathFromMap` to get a BorrowedDevicePath for the volume. For Relative paths, we use the current working directory to construct the new path. BorrowedDevicePath abstraction is needed to interact with `EFI_SHELL->GetDevicePathFromMap` which returns a Device Path Protocol with the lifetime of UEFI shell. Absolute Shell paths cannot exist if UEFI shell is missing. Signed-off-by: Ayush Singh <ayush@beagleboard.org>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,102 @@ | ||
| #![forbid(unsafe_op_in_unsafe_fn)] | ||
| use crate::ffi::OsStr; | ||
| use crate::io; | ||
| use crate::path::{Path, PathBuf, Prefix}; | ||
| use crate::sys::{helpers, unsupported_err}; | ||
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| const FORWARD_SLASH: u8 = b'/'; | ||
| const COLON: u8 = b':'; | ||
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| #[inline] | ||
| pub fn is_sep_byte(b: u8) -> bool { | ||
| b == b'\\' | ||
| } | ||
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| #[inline] | ||
| pub fn is_verbatim_sep(b: u8) -> bool { | ||
| b == b'\\' | ||
| } | ||
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| pub fn parse_prefix(_: &OsStr) -> Option<Prefix<'_>> { | ||
| None | ||
| } | ||
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| pub const MAIN_SEP_STR: &str = "\\"; | ||
| pub const MAIN_SEP: char = '\\'; | ||
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| /// UEFI paths can be of 4 types: | ||
| /// | ||
| /// 1. Absolute Shell Path: Uses shell mappings. Does not exist if UEFI shell not present. | ||
| /// It can be identified with `:`. | ||
| /// Eg: FS0:\abc\run.efi | ||
| /// | ||
| /// 2. Absolute Device Path: this is what we want | ||
| /// It can be identified with `/`. | ||
| /// Eg: PciRoot(0x0)/Pci(0x1,0x1)/Ata(Secondary,Slave,0x0)/\abc\run.efi | ||
| /// | ||
| /// 3: Relative root: path relative to the current volume. | ||
| /// It will start with `\`. | ||
| /// Eg: \abc\run.efi | ||
| /// | ||
| /// 4: Relative | ||
| /// Eg: run.efi | ||
| /// | ||
| /// The algorithm is mostly taken from edk2 UEFI shell implementation and is | ||
| /// somewhat simple. Check for the path type in order. | ||
| /// | ||
| /// The volume mapping in Absolute Shell Path (not the rest of the path) can be converted to Device | ||
| /// Path Protocol using `EFI_SHELL->GetDevicePathFromMap`. The rest of the path (Relative root | ||
| /// path), can just be appended to the remaining path. | ||
| /// | ||
| /// For Relative root, we get the current volume (either in Shell Mapping, or Device Path Protocol | ||
| /// form) and join it with the relative root path. We then recurse the function to resolve the Shell | ||
| /// Mapping if present. | ||
| /// | ||
| /// For Relative paths, we use the current working directory to construct | ||
| /// the new path and recurse the function to resolve the Shell mapping if present. | ||
| pub(crate) fn absolute(path: &Path) -> io::Result<PathBuf> { | ||
| // Absolute Shell Path | ||
| if path.as_os_str().as_encoded_bytes().contains(&COLON) { | ||
| let mut path_components = path.components(); | ||
| // Since path is not empty, it has at least one Component | ||
| let prefix = path_components.next().unwrap(); | ||
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| let dev_path = helpers::get_device_path_from_map(prefix.as_ref())?; | ||
| let dev_path_text = dev_path.to_text().map_err(|_| unsupported_err())?; | ||
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| let mut ans = PathBuf::new(); | ||
| ans.push(&dev_path_text); | ||
| // The Device Path Protocol mapping text representation can sometimes miss the final | ||
| // seperator (Device path protocol seperator, aka '/'). | ||
| if *dev_path_text.as_encoded_bytes().last().unwrap() != FORWARD_SLASH { | ||
| ans.push("/"); | ||
| } | ||
| ans.push(path_components); | ||
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| return Ok(ans); | ||
| } | ||
|
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| // Absolute Device Path | ||
| if path.as_os_str().as_encoded_bytes().contains(&FORWARD_SLASH) { | ||
| return Ok(path.to_path_buf()); | ||
| } | ||
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| // cur_dir() always returns something | ||
| let cur_dir = crate::env::current_dir().unwrap(); | ||
| let mut path_components = path.components(); | ||
|
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| // Relative Root | ||
| if path_components.next().unwrap() == crate::path::Component::RootDir { | ||
| let mut ans = PathBuf::new(); | ||
| ans.push(cur_dir.components().next().unwrap()); | ||
| ans.push(path_components); | ||
| return absolute(&ans); | ||
| } | ||
|
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| absolute(&cur_dir.join(path)) | ||
| } | ||
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| pub(crate) fn is_absolute(path: &Path) -> bool { | ||
| let temp = path.as_os_str().as_encoded_bytes(); | ||
| temp.contains(&COLON) || temp.contains(&FORWARD_SLASH) | ||
| } |