uefi: Add initial working version of ConfigurationString (Spec 35.2.1) parser

Author: seijikun

uefi/CHANGELOG.md

@@ -6,6 +6,7 @@
 - Added `proto::pci::PciRootBridgeIo`.
 - Added `proto::hii::config::HiiKeywordHandler`.
 - Added `proto::hii::config::HiiConfigAccess`.
+- Added `proto::hii::config_str::ConfigurationString`.
 
 ## Changed
 - **Breaking:** `boot::stall` now take `core::time::Duration` instead of `usize`.

uefi/src/proto/hii/config_str.rs

@@ -0,0 +1,261 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+//! UEFI Configuration String parsing according to Spec 35.2.1
+
+use alloc::boxed::Box;
+use alloc::string::{String, ToString};
+use alloc::vec::Vec;
+use core::slice;
+use core::str::{self, FromStr};
+use uguid::Guid;
+
+use crate::proto::device_path::DevicePath;
+use crate::{CStr16, Char16};
+
+/// A helper struct to split and parse a UEFI Configuration String.
+///
+/// Configuration strings consist of key-value pairs separated by `&`. Keys
+/// and values are separated by `=`. This struct provides an iterator for
+/// easy traversal of the key-value pairs.
+///
+/// For reasons of developer sanity, this is operating on &str instead of &CStr16.
+#[derive(Debug)]
+pub struct ConfigurationStringSplitter<'a> {
+    bfr: &'a str,
+}
+
+impl<'a> ConfigurationStringSplitter<'a> {
+    /// Creates a new splitter instance for a given configuration string buffer.
+    #[must_use]
+    pub const fn new(bfr: &'a str) -> Self {
+        Self { bfr }
+    }
+}
+
+impl<'a> Iterator for ConfigurationStringSplitter<'a> {
+    type Item = (&'a str, Option<&'a str>);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.bfr.is_empty() {
+            return None;
+        }
+        let (keyval, remainder) = self
+            .bfr
+            .split_once('&')
+            .unwrap_or((self.bfr, &self.bfr[0..0]));
+        self.bfr = remainder;
+        let (key, value) = keyval
+            .split_once('=')
+            .map(|(key, value)| (key, Some(value)))
+            .unwrap_or((keyval, None));
+        Some((key, value))
+    }
+}
+
+/// Enum representing different sections of a UEFI Configuration Header.
+///
+/// These sections include GUID, Name, and Path elements, which provide
+/// routing and identification information for UEFI components.
+#[derive(Debug, PartialEq, Eq)]
+pub enum ConfigHdrSection {
+    /// UEFI ConfigurationString {GuidHdr} element
+    Guid,
+    /// UEFI ConfigurationString {NameHdr} element
+    Name,
+    /// UEFI ConfigurationString {PathHdr} element
+    Path,
+}
+
+/// Enum representing possible parsing errors encountered when processing
+/// UEFI Configuration Strings.
+#[derive(Debug)]
+pub enum ParseError {
+    /// Error while parsing the UEFI {ConfigHdr} configuration string section.
+    ConfigHdr(ConfigHdrSection),
+    /// Error while parsing the UEFI {BlockName} configuration string section.
+    BlockName,
+    /// Error while parsing the UEFI {BlockConfig} configuration string section.
+    BlockConfig,
+}
+
+/// Represents an individual element within a UEFI Configuration String.
+///
+/// Each element contains an offset, width, and value, defining the data
+/// stored at specific memory locations within the configuration.
+#[derive(Debug, Default)]
+pub struct ConfigurationStringElement {
+    /// Byte offset in the configuration block
+    pub offset: u64,
+    /// Length of the value starting at offset
+    pub width: u64,
+    /// Value bytes
+    pub value: Vec<u8>,
+    // TODO
+    // nvconfig: HashMap<String, Vec<u8>>,
+}
+
+/// A full UEFI Configuration String representation.
+///
+/// This structure contains routing information such as GUID and device path,
+/// along with the parsed configuration elements.
+#[derive(Debug)]
+pub struct ConfigurationString {
+    /// GUID used for identifying the configuration
+    pub guid: Guid,
+    /// Name field (optional identifier)
+    pub name: String,
+    /// Associated UEFI device path
+    pub device_path: Box<DevicePath>,
+    /// Parsed UEFI {ConfigElement} sections
+    pub elements: Vec<ConfigurationStringElement>,
+}
+
+impl ConfigurationString {
+    fn try_parse_with<T, F: FnOnce() -> Option<T>>(
+        err: ParseError,
+        parse_fn: F,
+    ) -> Result<T, ParseError> {
+        parse_fn().ok_or(err)
+    }
+
+    /// Parses a hexadecimal string into an iterator of bytes.
+    ///
+    /// # Arguments
+    ///
+    /// * `hex` - The hexadecimal string representing binary data.
+    ///
+    /// # Returns
+    ///
+    /// An iterator over bytes.
+    pub fn parse_bytes_from_hex(hex: &str) -> impl Iterator<Item = u8> {
+        hex.as_bytes().chunks(2).map(|chunk| {
+            let chunk = str::from_utf8(chunk).unwrap_or_default();
+            u8::from_str_radix(chunk, 16).unwrap_or_default()
+        })
+    }
+
+    /// Converts a hexadecimal string representation into a numeric value.
+    ///
+    /// # Arguments
+    ///
+    /// * `data` - The hexadecimal string to convert.
+    ///
+    /// # Returns
+    ///
+    /// An `Option<u64>` representing the parsed number.
+    #[must_use]
+    pub fn parse_number_from_hex(data: &str) -> Option<u64> {
+        let data: Vec<_> = Self::parse_bytes_from_hex(data).collect();
+        match data.len() {
+            8 => Some(u64::from_be_bytes(data.try_into().unwrap())),
+            4 => Some(u32::from_be_bytes(data.try_into().unwrap()) as u64),
+            2 => Some(u16::from_be_bytes(data.try_into().unwrap()) as u64),
+            1 => Some(u8::from_be_bytes(data.try_into().unwrap()) as u64),
+            _ => None,
+        }
+    }
+
+    /// Converts a hexadecimal string into a UTF-16 string.
+    ///
+    /// # Arguments
+    ///
+    /// * `data` - The hexadecimal representation of a string.
+    ///
+    /// # Returns
+    ///
+    /// An `Option<String>` containing the parsed string.
+    #[must_use]
+    pub fn parse_string_from_hex(data: &str) -> Option<String> {
+        if data.len() % 2 != 0 {
+            return None;
+        }
+        let mut data: Vec<_> = Self::parse_bytes_from_hex(data).collect();
+        data.chunks_exact_mut(2).for_each(|c| c.swap(0, 1));
+        data.extend_from_slice(&[0, 0]);
+        let data: &[Char16] =
+            unsafe { slice::from_raw_parts(data.as_slice().as_ptr().cast(), data.len() / 2) };
+        Some(CStr16::from_char16_with_nul(data).ok()?.to_string())
+    }
+
+    /// Parses a hexadecimal string into a UEFI GUID.
+    ///
+    /// # Arguments
+    ///
+    /// * `data` - The hexadecimal GUID representation.
+    ///
+    /// # Returns
+    ///
+    /// An `Option<Guid>` containing the parsed GUID.
+    #[must_use]
+    pub fn parse_guid_from_hex(data: &str) -> Option<Guid> {
+        let v: Vec<_> = Self::parse_bytes_from_hex(data).collect();
+        Some(Guid::from_bytes(v.try_into().ok()?))
+    }
+}
+
+impl FromStr for ConfigurationString {
+    type Err = ParseError;
+
+    fn from_str(bfr: &str) -> Result<Self, Self::Err> {
+        let mut splitter = ConfigurationStringSplitter::new(bfr).peekable();
+
+        let guid = Self::try_parse_with(ParseError::ConfigHdr(ConfigHdrSection::Guid), || {
+            let v = splitter.next()?;
+            let v = (v.0 == "GUID").then_some(v.1).flatten()?;
+            Self::parse_guid_from_hex(v)
+        })?;
+        let name = Self::try_parse_with(ParseError::ConfigHdr(ConfigHdrSection::Name), || {
+            let v = splitter.next()?;
+            let v = (v.0 == "NAME").then_some(v.1).flatten()?;
+            Self::parse_string_from_hex(v)
+        })?;
+        let device_path =
+            Self::try_parse_with(ParseError::ConfigHdr(ConfigHdrSection::Path), || {
+                let v = splitter.next()?.1?;
+                let v: Vec<_> = Self::parse_bytes_from_hex(v).collect();
+                let v = <&DevicePath>::try_from(v.as_slice()).ok()?;
+                Some(v.to_boxed())
+            })?;
+
+        let mut elements = Vec::new();
+        loop {
+            let offset = match splitter.next() {
+                Some(("OFFSET", Some(data))) => {
+                    Self::parse_number_from_hex(data).ok_or(ParseError::BlockName)?
+                }
+                None => break,
+                _ => return Err(ParseError::BlockName),
+            };
+            let width = match splitter.next() {
+                Some(("WIDTH", Some(data))) => {
+                    Self::parse_number_from_hex(data).ok_or(ParseError::BlockName)?
+                }
+                _ => return Err(ParseError::BlockName),
+            };
+            let value = match splitter.next() {
+                Some(("VALUE", Some(data))) => Self::parse_bytes_from_hex(data).collect(),
+                _ => return Err(ParseError::BlockConfig),
+            };
+
+            while let Some(next) = splitter.peek() {
+                if next.0 == "OFFSET" {
+                    break;
+                }
+                let _ = splitter.next(); // drop nvconfig entries for now
+            }
+
+            elements.push(ConfigurationStringElement {
+                offset,
+                width,
+                value,
+            });
+        }
+
+        Ok(Self {
+            guid,
+            name,
+            device_path,
+            elements,
+        })
+    }
+}

uefi/src/proto/hii/mod.rs

@@ -3,3 +3,5 @@
 //! HII Protocols
 
 pub mod config;
+#[cfg(feature = "alloc")]
+pub mod config_str;