uefi: Add get_variable_boxed

This alloc-only method is a more convenient form of `get_variable`.

Author: nicholasbishop

CHANGELOG.md

@@ -19,6 +19,7 @@
   - `From<&CStr16>` for `CString16`
   - `From<&CStr16>` for `String`
   - `From<&CString16>` for `String`
+- Added `RuntimeServices::get_variable_boxed` (requires the `alloc` feature).
 
 ### Changed
 

uefi-test-runner/src/runtime/vars.rs

@@ -29,6 +29,13 @@ fn test_variables(rt: &RuntimeServices) {
     assert_eq!(data, test_value);
     assert_eq!(attrs, test_attrs);
 
+    info!("Testing get_variable_boxed");
+    let (data, attrs) = rt
+        .get_variable_boxed(name, &vendor)
+        .expect("failed to get variable");
+    assert_eq!(&*data, test_value);
+    assert_eq!(attrs, test_attrs);
+
     info!("Testing variable_keys");
     let variable_keys = rt.variable_keys().expect("failed to get variable keys");
     info!("Found {} variables", variable_keys.len());

uefi/src/table/runtime.rs

@@ -1,20 +1,22 @@
 //! UEFI services available at runtime, even after the OS boots.
 
 use super::{Header, Revision};
-#[cfg(feature = "alloc")]
-use crate::data_types::FromSliceWithNulError;
-use crate::result::Error;
 use crate::table::boot::MemoryDescriptor;
-use crate::{guid, CStr16, Char16, Guid, Result, Status, StatusExt};
-#[cfg(feature = "alloc")]
-use alloc::{vec, vec::Vec};
+use crate::{guid, CStr16, Char16, Error, Guid, Result, Status, StatusExt};
 use bitflags::bitflags;
 use core::ffi::c_void;
 use core::fmt::{Debug, Formatter};
-#[cfg(feature = "alloc")]
-use core::mem;
 use core::mem::MaybeUninit;
 use core::{fmt, ptr};
+
+#[cfg(feature = "alloc")]
+use {
+    crate::data_types::FromSliceWithNulError,
+    alloc::boxed::Box,
+    alloc::{vec, vec::Vec},
+    core::mem,
+};
+
 /// Contains pointers to all of the runtime services.
 ///
 /// This table, and the function pointers it contains are valid
@@ -159,6 +161,38 @@ impl RuntimeServices {
         }
     }
 
+    /// Get the contents and attributes of a variable.
+    #[cfg(feature = "alloc")]
+    pub fn get_variable_boxed(
+        &self,
+        name: &CStr16,
+        vendor: &VariableVendor,
+    ) -> Result<(Box<[u8]>, VariableAttributes)> {
+        let mut attributes = VariableAttributes::empty();
+
+        let mut data_size = self.get_variable_size(name, vendor)?;
+        let mut data = Vec::with_capacity(data_size);
+
+        let status = unsafe {
+            (self.get_variable)(
+                name.as_ptr(),
+                &vendor.0,
+                &mut attributes,
+                &mut data_size,
+                data.as_mut_ptr(),
+            )
+        };
+        if !status.is_success() {
+            return Err(Error::from(status));
+        }
+
+        unsafe {
+            data.set_len(data_size);
+        }
+
+        Ok((data.into_boxed_slice(), attributes))
+    }
+
     /// Get the names and vendor GUIDs of all currently-set variables.
     #[cfg(feature = "alloc")]
     pub fn variable_keys(&self) -> Result<Vec<VariableKey>> {