rust: panic: Call into arch panic handler

When the panic happens, call into the Zephyr `k_panic()` handler instead
of just spinning.  This should halt the whole system, not just the
current thread.

Signed-off-by: David Brown <[email protected]>

lib/rust/main.c

@@ -16,4 +16,12 @@ int main(void)
 	return 0;
 }
 
+/* On most arches, panic is entirely macros resulting in some kind of inline assembly.  Create this
+ * wrapper so the Rust panic handler can call the same kind of panic.
+ */
+void rust_panic_wrap(void)
+{
+	k_panic();
+}
+
 #endif

lib/rust/zephyr/src/lib.rs

@@ -33,7 +33,13 @@ fn panic(info :&PanicInfo) -> ! {
         printkln!("panic: {}", info);
     }
     let _ = info;
-    loop {
+
+    // Call into the wrapper for the system panic function.
+    unsafe {
+        extern "C" {
+            fn rust_panic_wrap() -> !;
+        }
+        rust_panic_wrap();
     }
 }