create/sel4-panicking: Refactor

Signed-off-by: Nick Spinale <[email protected]>
seL4 · Jan 18, 2024 · 42569be · 42569be
1 parent b9588b5
commit 42569be
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Showing 6 changed files with 43 additions and 35 deletions.
diff --git a/crates/private/tests/root-task/panicking/src/main.rs b/crates/private/tests/root-task/panicking/src/main.rs
@@ -58,7 +58,7 @@ cfg_if::cfg_if! {
             assert_eq!(r.err().unwrap().inner().downcast_ref::<String>().unwrap().as_str(), "foo");
         }
     } else {
-        use panicking::FitsWithinSmallPayload;
+        use panicking::SmallPayload;
 
         fn whether_alloc() {
             let r = panicking::catch_unwind(|| {
@@ -70,6 +70,6 @@ cfg_if::cfg_if! {
         #[derive(Copy, Clone)]
         struct Foo(usize);
 
-        impl FitsWithinSmallPayload for Foo {}
+        impl SmallPayload for Foo {}
     }
 }
diff --git a/crates/sel4-microkit/src/panicking.rs b/crates/sel4-microkit/src/panicking.rs
@@ -9,8 +9,7 @@ use sel4_panicking::set_hook as set_outer_hook;
 use sel4_panicking_env::debug_println;
 
 pub use sel4_panicking::{
-    catch_unwind, panic_any, ExternalPanicInfo, FitsWithinSmallPayload, PanicHook, Payload,
-    SmallPayloadValue, UpcastIntoPayload,
+    catch_unwind, panic_any, ExternalPanicInfo, PanicHook, Payload, SmallPayload, UpcastIntoPayload,
 };
 
 use crate::pd_name;

diff --git a/crates/sel4-panicking/src/lib.rs b/crates/sel4-panicking/src/lib.rs
@@ -34,9 +34,7 @@ use payload::NoPayload;
 use strategy::{panic_cleanup, start_panic};
 
 pub use hook::{set_hook, PanicHook};
-pub use payload::{FitsWithinSmallPayload, Payload, SmallPayloadValue, UpcastIntoPayload};
-
-// // //
+pub use payload::{Payload, SmallPayload, UpcastIntoPayload, SMALL_PAYLOAD_MAX_SIZE};
 
 pub struct ExternalPanicInfo<'a> {
     payload: Payload,
@@ -110,8 +108,6 @@ fn do_panic(info: ExternalPanicInfo) -> ! {
     }
 }
 
-// // //
-
 pub fn catch_unwind<R, F: FnOnce() -> R>(f: F) -> Result<R, Payload> {
     union Data<F, R> {
         f: ManuallyDrop<F>,

diff --git a/crates/sel4-panicking/src/payload/mod.rs b/crates/sel4-panicking/src/payload/mod.rs
@@ -5,7 +5,6 @@
 //
 
 use core::mem;
-use core::slice;
 
 cfg_if::cfg_if! {
     if #[cfg(feature = "alloc")] {
@@ -23,34 +22,26 @@ pub trait UpcastIntoPayload {
     fn upcast_into_payload(self) -> Payload;
 }
 
-#[derive(Clone, Copy)]
-pub struct SmallPayloadValue([u8; Self::SIZE]);
-
-impl SmallPayloadValue {
-    pub const SIZE: usize = 32;
+pub const SMALL_PAYLOAD_MAX_SIZE: usize = 32;
 
-    pub const fn ensure_fits<T: FitsWithinSmallPayload>() {
-        assert!(mem::size_of::<T>() <= Self::SIZE);
-    }
+#[allow(dead_code)]
+#[inline(always)]
+const fn check_small_payload_size<T: SmallPayload>() {
+    struct Check<T>(T);
 
-    pub fn write<T: FitsWithinSmallPayload + Copy>(val: &T) -> Self {
-        Self::ensure_fits::<T>();
-        let val_bytes =
-            unsafe { slice::from_raw_parts(val as *const T as *const u8, mem::size_of::<T>()) };
-        let mut payload_arr = [0; Self::SIZE];
-        payload_arr[..val_bytes.len()].copy_from_slice(val_bytes);
-        Self(payload_arr)
+    impl<T> Check<T> {
+        const CHECK: () = assert!(
+            mem::size_of::<T>() <= SMALL_PAYLOAD_MAX_SIZE,
+            "type is is too large to implement SmallPayload",
+        );
     }
 
-    pub fn read<T: FitsWithinSmallPayload + Copy>(&self) -> T {
-        Self::ensure_fits::<T>();
-        unsafe { mem::transmute_copy(&self.0) }
-    }
+    Check::<T>::CHECK
 }
 
-pub trait FitsWithinSmallPayload {}
+pub trait SmallPayload {}
 
 #[derive(Clone, Copy)]
 pub(crate) struct NoPayload;
 
-impl FitsWithinSmallPayload for NoPayload {}
+impl SmallPayload for NoPayload {}
diff --git a/crates/sel4-panicking/src/payload/with_alloc.rs b/crates/sel4-panicking/src/payload/with_alloc.rs
@@ -13,7 +13,7 @@ use super::UpcastIntoPayload;
 pub struct Payload(Box<dyn Any + Send + 'static>);
 
 impl Payload {
-    pub fn new(inner: Box<dyn Any + Send + 'static>) -> Self {
+    fn new(inner: Box<dyn Any + Send + 'static>) -> Self {
         Self(inner)
     }
 

diff --git a/crates/sel4-panicking/src/payload/without_alloc.rs b/crates/sel4-panicking/src/payload/without_alloc.rs
@@ -5,8 +5,11 @@
 //
 
 use core::any::{Any, TypeId};
+use core::mem;
+use core::ptr;
+use core::slice;
 
-use super::{FitsWithinSmallPayload, SmallPayloadValue, UpcastIntoPayload};
+use super::{check_small_payload_size, SmallPayload, UpcastIntoPayload, SMALL_PAYLOAD_MAX_SIZE};
 
 pub struct Payload {
     type_id: TypeId,
@@ -18,7 +21,7 @@ impl Payload {
         self.type_id
     }
 
-    pub fn downcast<T: FitsWithinSmallPayload + Copy + 'static>(self) -> Result<T, Self> {
+    pub fn downcast<T: SmallPayload + Copy + 'static>(self) -> Result<T, Self> {
         if self.type_id() == TypeId::of::<T>() {
             Ok(self.value.read())
         } else {
@@ -27,7 +30,7 @@ impl Payload {
     }
 }
 
-impl<T: FitsWithinSmallPayload + Copy + Any> UpcastIntoPayload for T {
+impl<T: SmallPayload + Copy + Any> UpcastIntoPayload for T {
     fn upcast_into_payload(self) -> Payload {
         let type_id = self.type_id();
         Payload {
@@ -36,3 +39,22 @@ impl<T: FitsWithinSmallPayload + Copy + Any> UpcastIntoPayload for T {
         }
     }
 }
+
+#[derive(Clone, Copy)]
+struct SmallPayloadValue([u8; SMALL_PAYLOAD_MAX_SIZE]);
+
+impl SmallPayloadValue {
+    fn write<T: SmallPayload + Copy>(val: &T) -> Self {
+        check_small_payload_size::<T>();
+        let val_bytes =
+            unsafe { slice::from_raw_parts(ptr::addr_of!(*val).cast::<u8>(), mem::size_of::<T>()) };
+        let mut payload_arr = [0; SMALL_PAYLOAD_MAX_SIZE];
+        payload_arr[..val_bytes.len()].copy_from_slice(val_bytes);
+        Self(payload_arr)
+    }
+
+    fn read<T: SmallPayload + Copy>(&self) -> T {
+        check_small_payload_size::<T>();
+        unsafe { mem::transmute_copy(&self.0) }
+    }
+}