Removing magic numbers from drivers sample

Author: Sanjukta Mitra

general/echo/kmdf/driver/DriverSync/src/device.rs

@@ -30,6 +30,10 @@ use crate::{
     WDF_REQUEST_CONTEXT_TYPE_INFO,
 };
 
+// Define constants for magic numbers
+const DEFAULT_PRIVATE_DATA: u32 = 0;
+const TIMER_DUE_TIME_MS: i64 = -100 * 10000;
+
 /// Worker routine called to create a device and its software resources.
 ///
 /// # Arguments:
@@ -108,7 +112,7 @@ pub fn echo_device_create(mut device_init: &mut WDFDEVICE_INIT) -> NTSTATUS {
         // it will return NULL and assert if run under framework verifier mode.
         let device_context: *mut DeviceContext =
             unsafe { wdf_object_get_device_context(device as WDFOBJECT) };
-        unsafe { (*device_context).private_device_data = 0 };
+        unsafe { (*device_context).private_device_data = DEFAULT_PRIVATE_DATA };
 
         // Create a device interface so that application can find and talk
         // to us.
@@ -162,7 +166,7 @@ extern "C" fn echo_evt_device_self_managed_io_start(device: WDFDEVICE) -> NTSTAT
     // into low power state.
     unsafe { call_unsafe_wdf_function_binding!(WdfIoQueueStart, queue) };
 
-    let due_time: i64 = -(100) * (10000);
+    let due_time: i64 = TIMER_DUE_TIME_MS;
 
     let _ = unsafe { (*queue_context).timer.start(due_time) };
 

general/echo/kmdf/driver/DriverSync/src/queue.rs

@@ -44,12 +44,18 @@ use crate::{
     WDF_TIMER_CONFIG_SIZE,
 };
 
-/// Set max write length for testing
+/// Set max write length for testing (40KB)
 const MAX_WRITE_LENGTH: usize = 1024 * 40;
 
-/// Set timer period in ms
+/// Set timer period in ms (10 seconds)
 const TIMER_PERIOD: u32 = 1000 * 10;
 
+/// Increment value for atomic operations
+const ATOMIC_INCREMENT_VALUE: i32 = 1;
+
+/// Floor value for zero-based operations
+const ZERO_FLOOR: i32 = 0;
+
 /// This routine will interlock increment a value only if the current value
 /// is greater then the floor value.
 ///
@@ -79,7 +85,7 @@ fn echo_interlocked_increment_floor(target: &AtomicI32, floor: i32) -> i32 {
         //
         match target.compare_exchange(
             current_value,
-            current_value + 1,
+            current_value + ATOMIC_INCREMENT_VALUE,
             Ordering::SeqCst,
             Ordering::SeqCst,
         ) {
@@ -91,7 +97,7 @@ fn echo_interlocked_increment_floor(target: &AtomicI32, floor: i32) -> i32 {
         }
     }
 
-    current_value + 1
+    current_value + ATOMIC_INCREMENT_VALUE
 }
 
 /// Increment the value only if it is currently > 0.
@@ -104,7 +110,7 @@ fn echo_interlocked_increment_floor(target: &AtomicI32, floor: i32) -> i32 {
 ///
 /// Upon success, a value > 0.  Upon failure, a value <= 0.
 fn echo_interlocked_increment_gtzero(target: &AtomicI32) -> i32 {
-    echo_interlocked_increment_floor(target, 0)
+    echo_interlocked_increment_floor(target, ZERO_FLOOR)
 }
 
 /// The I/O dispatch callbacks for the frameworks device object
@@ -208,7 +214,7 @@ pub unsafe fn echo_queue_initialize(device: WDFDEVICE) -> NTSTATUS {
         EvtTimerFunc: Some(echo_evt_timer_func),
         Period: TIMER_PERIOD,
         AutomaticSerialization: u8::from(true),
-        TolerableDelay: 0,
+        TolerableDelay: TOLERABLE_DELAY,
         ..WDF_TIMER_CONFIG::default()
     };
 
@@ -266,7 +272,7 @@ fn echo_decrement_request_cancel_ownership_count(request_context: *mut RequestCo
             .fetch_sub(1, Ordering::SeqCst)
     };
 
-    result - 1 == 0
+    result - RESULT_SUCCESS_THRESHOLD == 0
 }
 
 /// Attempts to increment the request ownership count so that it cannot be
@@ -727,3 +733,7 @@ unsafe extern "C" fn echo_evt_timer_func(timer: WDFTIMER) {
         }
     }
 }
+
+// Define constants for magic numbers
+const TOLERABLE_DELAY: u32 = 0;
+const RESULT_SUCCESS_THRESHOLD: i32 = 1;

general/echo/kmdf/exe/src/main.rs

@@ -59,6 +59,15 @@ use windows_sys::Win32::{
     },
 };
 
+// Define constants for magic numbers
+const READER_TYPE: u32 = 1;
+const WRITER_TYPE: u32 = 2;
+const NUM_ASYNCH_IO: usize = 100;
+const BUFFER_SIZE: usize = 40 * 1024;
+const TEST_SIZE_SMALL: usize = 512;
+const TEST_SIZE_LARGE: usize = 30 * 1024;
+const NULL_TERMINATOR: u16 = 0;
+
 #[derive(Default, Debug)]
 struct Globals {
     perform_async_io: bool,
@@ -69,10 +78,6 @@ struct Globals {
 
 static GLOBAL_DATA: Lazy<RwLock<Globals>> = Lazy::new(|| RwLock::new(Globals::default()));
 static GUID_DEVINTERFACE_ECHO: Uuid = uuid!("CDC35B6E-0BE4-4936-BF5F-5537380A7C1A");
-static READER_TYPE: u32 = 1;
-static WRITER_TYPE: u32 = 2;
-static NUM_ASYNCH_IO: usize = 100;
-static BUFFER_SIZE: usize = 40 * 1024;
 
 fn main() -> Result<(), Box<dyn Error>> {
     let argument_vector: Vec<String> = env::args().collect();
@@ -111,7 +116,7 @@ Exit the app anytime by pressing Ctrl-C
     drop(globals);
 
     let h_device: HANDLE;
-    path_vec.push(0);
+    path_vec.push(NULL_TERMINATOR);
     let path = path_vec.as_ptr();
 
     // SAFETY:
@@ -153,9 +158,9 @@ Exit the app anytime by pressing Ctrl-C
 
         h.join().unwrap().unwrap();
     } else {
-        perform_write_read_test(h_device, 512)?;
+        perform_write_read_test(h_device, u32::try_from(TEST_SIZE_SMALL).unwrap())?;
 
-        perform_write_read_test(h_device, 30 * 1024)?;
+        perform_write_read_test(h_device, u32::try_from(TEST_SIZE_LARGE).unwrap())?;
     }
 
     Ok(())

tools/dv/kmdf/fail_driver_pool_leak/src/driver.rs

@@ -25,6 +25,10 @@ use wdk_sys::{
 
 use crate::{GLOBAL_BUFFER, GUID_DEVINTERFACE};
 
+// Define constants for magic numbers
+const POOL_ALLOCATION_SIZE: usize = 64;
+const POOL_TAG: u32 = 's' as u32;
+
 /// `DriverEntry` initializes the driver and is the first routine called by the
 /// system after the driver is loaded. `DriverEntry` specifies the other entry
 /// points in the function driver, such as `EvtDevice` and `DriverUnload`.
@@ -147,8 +151,11 @@ extern "C" fn evt_driver_device_add(
     // Global buffer. This pool of memory is intentionally not freed by
     // the driver.
     unsafe {
-        const LENGTH: usize = 64;
-        GLOBAL_BUFFER = ExAllocatePool2(POOL_FLAG_NON_PAGED, LENGTH as SIZE_T, 's' as u32);
+        GLOBAL_BUFFER = ExAllocatePool2(
+            POOL_FLAG_NON_PAGED,
+            POOL_ALLOCATION_SIZE as SIZE_T,
+            POOL_TAG,
+        );
     }
 
     nt_status = unsafe {