apkdmverity: use data_model crate for better handling of C structs
The data_model:DataInit trait provides methods for converting between
a C struct and an array of the same size, allowing us to drop the hand
crafted as_u8_slice methods.
Bug: N/A
Test: cargo test
Test: atest apkdmverity.test
Change-Id: Iaff910f0a638e91a428777b94dc6fb0b5fe53831
diff --git a/apkverity/src/dm.rs b/apkverity/src/dm.rs
index 7ac72c8..75a4366 100644
--- a/apkverity/src/dm.rs
+++ b/apkverity/src/dm.rs
@@ -29,6 +29,7 @@
use crate::util::*;
use anyhow::Result;
+use data_model::DataInit;
use std::fs::{File, OpenOptions};
use std::io::Write;
use std::mem::size_of;
@@ -74,6 +75,7 @@
// `DmTargetSpec` is the header of the data structure for a device-mapper target. When doing the
// ioctl, one of more `DmTargetSpec` (and its body) are appened to the `DmIoctl` struct.
#[repr(C)]
+#[derive(Copy, Clone)]
struct DmTargetSpec {
sector_start: u64,
length: u64, // number of 512 sectors
@@ -82,24 +84,22 @@
target_type: [u8; DM_MAX_TYPE_NAME],
}
+// SAFETY: C struct is safe to be initialized from raw data
+unsafe impl DataInit for DmTargetSpec {}
+
impl DmTargetSpec {
fn new(target_type: &str) -> Result<Self> {
- // SAFETY: zero initialized C struct is safe
- let mut spec = unsafe { std::mem::MaybeUninit::<Self>::zeroed().assume_init() };
+ // safe because the size of the array is the same as the size of the struct
+ let mut spec: Self = *DataInit::from_mut_slice(&mut [0; size_of::<Self>()]).unwrap();
spec.target_type.as_mut().write_all(target_type.as_bytes())?;
Ok(spec)
}
-
- fn as_u8_slice(&self) -> &[u8; size_of::<Self>()] {
- // SAFETY: lifetime of the output reference isn't changed.
- unsafe { &*(&self as *const &Self as *const [u8; size_of::<Self>()]) }
- }
}
impl DmIoctl {
fn new(name: &str) -> Result<DmIoctl> {
- // SAFETY: zero initialized C struct is safe
- let mut data = unsafe { std::mem::MaybeUninit::<Self>::zeroed().assume_init() };
+ // safe because the size of the array is the same as the size of the struct
+ let mut data: Self = *DataInit::from_mut_slice(&mut [0; size_of::<Self>()]).unwrap();
data.version[0] = DM_VERSION_MAJOR;
data.version[1] = DM_VERSION_MINOR;
data.version[2] = DM_VERSION_PATCHLEVEL;
@@ -115,11 +115,6 @@
dst.write_all(uuid.as_bytes())?;
Ok(())
}
-
- fn as_u8_slice(&self) -> &[u8; size_of::<Self>()] {
- // SAFETY: lifetime of the output reference isn't changed.
- unsafe { &*(&self as *const &Self as *const [u8; size_of::<Self>()]) }
- }
}
/// `DeviceMapper` is the entry point for the device mapper framework. It essentially is a file
@@ -153,7 +148,7 @@
dm_dev_create(&self, &mut data)?;
// Step 2: load table onto the device
- let payload_size = size_of::<DmIoctl>() + target.as_u8_slice().len();
+ let payload_size = size_of::<DmIoctl>() + target.as_slice().len();
let mut data = DmIoctl::new(&name)?;
data.data_size = payload_size as u32;
@@ -162,8 +157,8 @@
data.flags |= Flag::DM_READONLY_FLAG;
let mut payload = Vec::with_capacity(payload_size);
- payload.extend_from_slice(data.as_u8_slice());
- payload.extend_from_slice(target.as_u8_slice());
+ payload.extend_from_slice(data.as_slice());
+ payload.extend_from_slice(target.as_slice());
dm_table_load(&self, payload.as_mut_ptr() as *mut DmIoctl)?;
// Step 3: activate the device (note: the term 'suspend' might be misleading, but it