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uefi: Add TryFrom u8 slice to DevicePathNode #1197

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Jun 11, 2024
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2 changes: 1 addition & 1 deletion uefi/CHANGELOG.md
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@
- Added `table::{set_system_table, system_table_boot, system_table_runtime}`.
This provides an initial API for global tables that do not require passing
around a reference.
- Added `TryFrom<&[u8]>` for `DevicePathHeader`.
- Added `TryFrom<&[u8]>` for `DevicePathHeader` and `DevicePathNode`.
- Added `ByteConversionError`.

## Changed
Expand Down
42 changes: 42 additions & 0 deletions uefi/src/proto/device_path/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,19 @@ impl PartialEq for DevicePathNode {
}
}

impl<'a> TryFrom<&[u8]> for &'a DevicePathNode {
type Error = ByteConversionError;

fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> {
let dp = <&DevicePathHeader>::try_from(bytes)?;
if usize::from(dp.length) <= bytes.len() {
unsafe { Ok(DevicePathNode::from_ffi_ptr(bytes.as_ptr().cast())) }
} else {
Err(ByteConversionError::InvalidLength)
}
}
}

/// A single device path instance that ends with either an [`END_INSTANCE`]
/// or [`END_ENTIRE`] node. Use [`DevicePath::instance_iter`] to get the
/// path instances in a [`DevicePath`].
Expand Down Expand Up @@ -975,4 +988,33 @@ mod tests {
let owned_dp_ref = &*owned_dp;
assert_eq!(owned_dp_ref, dp)
}

#[test]
fn test_device_path_node_from_bytes() {
let mut raw_data = Vec::new();
let node = [0xa0, 0xb0];
let node_data = &[10, 11];

// Raw data is less than size of a [`DevicePathNode`].
raw_data.push(node[0]);
assert!(<&DevicePathNode>::try_from(raw_data.as_slice()).is_err());

// Raw data is long enough to hold a [`DevicePathNode`].
raw_data.push(node[1]);
raw_data.extend(
u16::try_from(mem::size_of::<DevicePathHeader>() + node_data.len())
.unwrap()
.to_le_bytes(),
);
raw_data.extend(node_data);
let dp = <&DevicePathNode>::try_from(raw_data.as_slice()).unwrap();

// Relevant assertions to verify the conversion is fine.
assert_eq!(mem::size_of_val(dp), 6);
check_node(dp, 0xa0, 0xb0, &[10, 11]);

// [`DevicePathNode`] data length exceeds the raw_data slice.
raw_data[2] += 1;
assert!(<&DevicePathNode>::try_from(raw_data.as_slice()).is_err());
}
}