From d60bafbf05f1ee84b1f70a1136701f1d729d1ca8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Quentin?= <bjoernQ@users.noreply.github.com>
Date: Mon, 2 Sep 2024 15:38:10 +0200
Subject: [PATCH] Improve CP0-disabled error message (#2061)

* Improve CP0-disabled error message

* CHANGELOG.md
---
 esp-backtrace/CHANGELOG.md  |  1 +
 esp-backtrace/src/lib.rs    |  2 +-
 esp-backtrace/src/xtensa.rs | 14 ++++++++++++--
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/esp-backtrace/CHANGELOG.md b/esp-backtrace/CHANGELOG.md
index 8db4528b8..ba80eba49 100644
--- a/esp-backtrace/CHANGELOG.md
+++ b/esp-backtrace/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 ### Changed
+- Print a more helpful message in case of a `Cp0Disabled` exception (#2061)
 
 ### Fixed
 
diff --git a/esp-backtrace/src/lib.rs b/esp-backtrace/src/lib.rs
index c51c7742d..f023e605a 100644
--- a/esp-backtrace/src/lib.rs
+++ b/esp-backtrace/src/lib.rs
@@ -100,7 +100,7 @@ unsafe fn __user_exception(cause: arch::ExceptionCause, context: arch::Context)
 
     // Unfortunately, a different formatter string is used
     #[cfg(not(feature = "defmt"))]
-    esp_println::println!("\n\nException occurred '{:?}'", cause);
+    esp_println::println!("\n\nException occurred '{}'", cause);
 
     #[cfg(feature = "defmt")]
     defmt::error!("\n\nException occurred '{}'", cause);
diff --git a/esp-backtrace/src/xtensa.rs b/esp-backtrace/src/xtensa.rs
index e22e1b5a9..eb0c4425c 100644
--- a/esp-backtrace/src/xtensa.rs
+++ b/esp-backtrace/src/xtensa.rs
@@ -1,4 +1,4 @@
-use core::arch::asm;
+use core::{arch::asm, fmt::Display};
 
 use crate::MAX_BACKTRACE_ADDRESSES;
 
@@ -11,7 +11,7 @@ pub(super) const RA_OFFSET: usize = 3;
 
 /// Exception Cause
 #[doc(hidden)]
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[repr(C)]
 pub enum ExceptionCause {
@@ -99,6 +99,16 @@ pub enum ExceptionCause {
     None                           = 255,
 }
 
+impl Display for ExceptionCause {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        if *self == Self::Cp0Disabled {
+            write!(f, "Cp0Disabled (Access to the floating point coprocessor is not allowed. You may want to enable the `float-save-restore` feature of the `xtensa-lx-rt` crate.)")
+        } else {
+            write!(f, "{:?}", self)
+        }
+    }
+}
+
 #[doc(hidden)]
 #[allow(non_snake_case)]
 #[derive(Clone, Copy)]