uefi: Implementing var(), vars(), and set_var() for shell interface protocol

The var() and vars() functions wrap the UEFI get_env() implementation to
retrieve a single and multiple environment variables respectively.
The set_var() function wraps the UEFI set_env() variable to set the value
of an environment variable.

Co-authored-by: Philipp Schuster <phip1611@gmail.com>

Author: RenTrieu

uefi-test-runner/src/proto/shell.rs

@@ -100,6 +100,48 @@ pub fn test_current_dir(shell: &ScopedProtocol<Shell>) {
     assert_eq!(cur_fs_str, expected_fs_str);
 }
 
+/// Test `var()`, `vars()`, and `set_var()`
+pub fn test_var(shell: &ScopedProtocol<Shell>) {
+    /* Test retrieving list of environment variable names */
+    let mut cur_env_vec = shell.vars();
+    assert_eq!(cur_env_vec.next().unwrap().0, cstr16!("path"));
+    // check pre-defined shell variables; see UEFI Shell spec
+    assert_eq!(cur_env_vec.next().unwrap().0, cstr16!("nonesting"));
+    let cur_env_vec = shell.vars();
+    let default_len = cur_env_vec.count();
+
+    /* Test setting and getting a specific environment variable */
+    let test_var = cstr16!("test_var");
+    let test_val = cstr16!("test_val");
+
+    let found_var = shell.vars().any(|(env_var, _)| env_var == test_var);
+    assert!(!found_var);
+    assert!(shell.var(test_var).is_none());
+
+    let status = shell.set_var(test_var, test_val, false);
+    assert!(status.is_ok());
+    let cur_env_str = shell
+        .var(test_var)
+        .expect("Could not get environment variable");
+    assert_eq!(cur_env_str, test_val);
+
+    let found_var = shell.vars().any(|(env_var, _)| env_var == test_var);
+    assert!(found_var);
+    let cur_env_vec = shell.vars();
+    assert_eq!(cur_env_vec.count(), default_len + 1);
+
+    /* Test deleting environment variable */
+    let test_val = cstr16!("");
+    let status = shell.set_var(test_var, test_val, false);
+    assert!(status.is_ok());
+    assert!(shell.var(test_var).is_none());
+
+    let found_var = shell.vars().any(|(env_var, _)| env_var == test_var);
+    assert!(!found_var);
+    let cur_env_vec = shell.vars();
+    assert_eq!(cur_env_vec.count(), default_len);
+}
+
 pub fn test() {
     info!("Running shell protocol tests");
 
@@ -109,4 +151,5 @@ pub fn test() {
         boot::open_protocol_exclusive::<Shell>(handle).expect("Failed to open Shell protocol");
 
     test_current_dir(&shell);
+    test_var(&shell);
 }

uefi/src/proto/mod.rs

@@ -51,6 +51,7 @@ pub mod rng;
 #[cfg(feature = "alloc")]
 pub mod scsi;
 pub mod security;
+#[cfg(feature = "alloc")]
 pub mod shell;
 pub mod shell_params;
 pub mod shim;

uefi/src/proto/shell/mod.rs

@@ -4,6 +4,8 @@
 
 use crate::proto::unsafe_protocol;
 use crate::{CStr16, Char16, Error, Result, Status, StatusExt};
+
+use core::marker::PhantomData;
 use core::ptr;
 use uefi_raw::protocol::shell::ShellProtocol;
 
@@ -13,6 +15,45 @@ use uefi_raw::protocol::shell::ShellProtocol;
 #[unsafe_protocol(ShellProtocol::GUID)]
 pub struct Shell(ShellProtocol);
 
+/// Trait for implementing the var function
+pub trait ShellVarProvider {
+    /// Gets the value of the specified environment variable
+    fn var(&self, name: &CStr16) -> Option<&CStr16>;
+}
+
+/// Iterator over the names of environmental variables obtained from the Shell protocol.
+#[derive(Debug)]
+pub struct Vars<'a, T: ShellVarProvider> {
+    /// Char16 containing names of environment variables
+    names: *const Char16,
+    /// Reference to Shell Protocol
+    protocol: *const T,
+    /// Marker to attach a lifetime to `Vars`
+    _marker: PhantomData<&'a CStr16>,
+}
+
+impl<'a, T: ShellVarProvider + 'a> Iterator for Vars<'a, T> {
+    type Item = (&'a CStr16, Option<&'a CStr16>);
+    // We iterate a list of NUL terminated CStr16s.
+    // The list is terminated with a double NUL.
+    fn next(&mut self) -> Option<Self::Item> {
+        let s = unsafe { CStr16::from_ptr(self.names) };
+        if s.is_empty() {
+            None
+        } else {
+            self.names = unsafe { self.names.add(s.num_chars() + 1) };
+            Some((s, unsafe { self.protocol.as_ref().unwrap().var(s) }))
+        }
+    }
+}
+
+impl ShellVarProvider for Shell {
+    /// Gets the value of the specified environment variable
+    fn var(&self, name: &CStr16) -> Option<&CStr16> {
+        self.var(name)
+    }
+}
+
 impl Shell {
     /// Returns the current directory on the specified device.
     ///
@@ -54,4 +95,159 @@ impl Shell {
         let dir_ptr: *const Char16 = directory.map_or(ptr::null(), |x| x.as_ptr());
         unsafe { (self.0.set_cur_dir)(fs_ptr.cast(), dir_ptr.cast()) }.to_result()
     }
+
+    /// Gets the value of the specified environment variable
+    ///
+    /// # Arguments
+    ///
+    /// * `name` - The environment variable name of which to retrieve the
+    ///   value.
+    ///
+    /// # Returns
+    ///
+    /// * `Some(<env_value>)` - &CStr16 containing the value of the
+    ///   environment variable
+    /// * `None` - If environment variable does not exist
+    #[must_use]
+    pub fn var(&self, name: &CStr16) -> Option<&CStr16> {
+        let name_ptr: *const Char16 = name.as_ptr();
+        let var_val = unsafe { (self.0.get_env)(name_ptr.cast()) };
+        if var_val.is_null() {
+            None
+        } else {
+            unsafe { Some(CStr16::from_ptr(var_val.cast())) }
+        }
+    }
+
+    /// Gets an iterator over the names of all environment variables
+    ///
+    /// # Returns
+    ///
+    /// * `Vars` - Iterator over the names of the environment variables
+    #[must_use]
+    pub fn vars(&self) -> Vars<'_, Self> {
+        let env_ptr = unsafe { (self.0.get_env)(ptr::null()) };
+        Vars {
+            names: env_ptr.cast::<Char16>(),
+            protocol: self,
+            _marker: PhantomData,
+        }
+    }
+
+    /// Sets the environment variable
+    ///
+    /// # Arguments
+    ///
+    /// * `name` - The environment variable for which to set the value
+    /// * `value` - The new value of the environment variable
+    /// * `volatile` - Indicates whether the variable is volatile or
+    ///   not
+    ///
+    /// # Returns
+    ///
+    /// * `Status::SUCCESS` - The variable was successfully set
+    pub fn set_var(&self, name: &CStr16, value: &CStr16, volatile: bool) -> Result {
+        let name_ptr: *const Char16 = name.as_ptr();
+        let value_ptr: *const Char16 = value.as_ptr();
+        unsafe { (self.0.set_env)(name_ptr.cast(), value_ptr.cast(), volatile) }.to_result()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use alloc::collections::BTreeMap;
+    use alloc::vec::Vec;
+    use uefi::cstr16;
+
+    struct ShellMock<'a> {
+        inner: BTreeMap<&'a CStr16, &'a CStr16>,
+    }
+
+    impl<'a> ShellMock<'a> {
+        fn new(pairs: impl IntoIterator<Item = (&'a CStr16, &'a CStr16)>) -> ShellMock<'a> {
+            let mut inner_map = BTreeMap::new();
+            for (name, val) in pairs.into_iter() {
+                inner_map.insert(name, val);
+            }
+            ShellMock { inner: inner_map }
+        }
+    }
+    impl<'a> ShellVarProvider for ShellMock<'a> {
+        fn var(&self, name: &CStr16) -> Option<&CStr16> {
+            if let Some(val) = self.inner.get(name) {
+                Some(*val)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Testing Vars struct
+    #[test]
+    fn test_vars() {
+        // Empty Vars
+        let mut vars_mock = Vec::<u16>::new();
+        vars_mock.extend_from_slice(
+            b"\0\0"
+                .into_iter()
+                .map(|&x| x as u16)
+                .collect::<Vec<_>>()
+                .as_slice(),
+        );
+        let mut vars = Vars {
+            names: vars_mock.as_ptr().cast(),
+            protocol: &ShellMock::new(Vec::new()),
+            _marker: PhantomData,
+        };
+
+        assert!(vars.next().is_none());
+
+        // One environment variable in Vars
+        let mut vars_mock = Vec::<u16>::new();
+        vars_mock.extend_from_slice(
+            b"foo\0\0"
+                .into_iter()
+                .map(|&x| x as u16)
+                .collect::<Vec<_>>()
+                .as_slice(),
+        );
+        let vars = Vars {
+            names: vars_mock.as_ptr().cast(),
+            protocol: &ShellMock::new(Vec::from([(cstr16!("foo"), cstr16!("value"))])),
+            _marker: PhantomData,
+        };
+        assert_eq!(
+            vars.collect::<Vec<_>>(),
+            Vec::from([(cstr16!("foo"), Some(cstr16!("value")))])
+        );
+
+        // Multiple environment variables in Vars
+        let mut vars_mock = Vec::<u16>::new();
+        vars_mock.extend_from_slice(
+            b"foo1\0bar\0baz2\0\0"
+                .into_iter()
+                .map(|&x| x as u16)
+                .collect::<Vec<_>>()
+                .as_slice(),
+        );
+
+        let vars = Vars {
+            names: vars_mock.as_ptr().cast(),
+            protocol: &ShellMock::new(Vec::from([
+                (cstr16!("foo1"), cstr16!("value")),
+                (cstr16!("bar"), cstr16!("one")),
+                (cstr16!("baz2"), cstr16!("two")),
+            ])),
+            _marker: PhantomData,
+        };
+        assert_eq!(
+            vars.collect::<Vec<_>>(),
+            Vec::from([
+                (cstr16!("foo1"), Some(cstr16!("value"))),
+                (cstr16!("bar"), Some(cstr16!("one"))),
+                (cstr16!("baz2"), Some(cstr16!("two")))
+            ])
+        );
+    }
 }