add Exception

3 files changed, 57 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5e7ac7b..35a4523 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- `Exception` a enumeration of the kind of exceptions the processor can service.
+  There's also a `Exception::current` constructor that returns the `Exception`
+  that's currently being serviced.
+
 ## [v0.1.5]
 
 ### Added
diff --git a/src/exception.rs b/src/exception.rs
new file mode 100644
index 0000000..7046080
--- /dev/null
+++ b/src/exception.rs
@@ -0,0 +1,47 @@
+/// Kind of exception
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum Exception {
+    /// i.e. currently not servicing an exception
+    ThreadMode,
+    /// Non-maskable interrupt.
+    Nmi,
+    /// All class of fault.
+    HardFault,
+    /// Memory management.
+    MemoryManagementFault,
+    /// Pre-fetch fault, memory access fault.
+    BusFault,
+    /// Undefined instruction or illegal state.
+    UsageFault,
+    /// System service call via SWI instruction
+    SVCall,
+    /// Pendable request for system service
+    PendSV,
+    /// System tick timer
+    Systick,
+    /// An interrupt
+    Interrupt(u8),
+    // Unreachable variant
+    #[doc(hidden)]
+    Reserved,
+}
+
+impl Exception {
+    /// Returns the kind of exception that's currently being serviced
+    pub fn current() -> Exception {
+        match ::peripheral::scb().icsr.read() as u8 {
+            0 => Exception::ThreadMode,
+            2 => Exception::Nmi,
+            3 => Exception::HardFault,
+            4 => Exception::MemoryManagementFault,
+            5 => Exception::BusFault,
+            6 => Exception::UsageFault,
+            11 => Exception::SVCall,
+            14 => Exception::PendSV,
+            15 => Exception::Systick,
+            n if n >= 16 => Exception::Interrupt(n - 16),
+            _ => Exception::Reserved,
+
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 7459c4e..09eeceb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -22,6 +22,10 @@ pub mod interrupt;
 pub mod peripheral;
 pub mod register;
 
+mod exception;
+
+pub use exception::Exception;
+
 /// Stack frame
 #[repr(C)]
 pub struct StackFrame {