Fix rare Xtensa crash (#4580)

* Fix offset of double exception handler

* Fix initial PS value

* Changelog PR number

* Update esp-rtos/src/task/xtensa.rs

Co-authored-by: Copilot <[email protected]>

---------

Co-authored-by: Copilot <[email protected]>

Author: bugadani

esp-rtos/CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed an issue on ESP32 that prevented completing some interrupt handlers (#4459)
 - Fixed a possible deadlock on multi-core chips (#4478)
 - Fixed a memory leak of 48 bytes when deleting esp-radio timers (#4541)
+- Fixed a rare crash on Xtensa MCUs (#4580)
 
 ### Removed
 

esp-rtos/src/task/xtensa.rs

@@ -85,8 +85,10 @@ pub(crate) fn new_task_context(
         A6: task_fn as usize as u32,
         A7: param as usize as u32,
 
-        // For windowed ABI set WOE and CALLINC (pretend task was 'call4'd)
-        PS: 0x00040000 | ((1 & 3) << 16),
+        // For windowed ABI set WOE, UM, EXCM and CALLINC1 (pretend task was 'call4'd)
+        // UM and EXCM are important, so that restoring context will correctly restore an exception
+        // context (where the context switch happens).
+        PS: 0x00050030,
 
         ..Default::default()
     }

xtensa-lx-rt/CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Fixed offset of `DoubleException` handler (#4580)
 
 ### Removed
 

xtensa-lx-rt/exception-esp32.x.template

@@ -54,43 +54,43 @@ SECTIONS {
 
   .vectors :
   {
-    /* 
-      Each vector has 64 bytes that it must fit inside. For each vector we calculate the size of the previous one, 
+    /*
+      Each vector has 64 bytes that it must fit inside. For each vector we calculate the size of the previous one,
       and subtract that from 64 and start the new vector there.
     */
     _init_start = ABSOLUTE(.);
-    . = ALIGN(64);
+    . = 0x0;
     KEEP(*(.WindowOverflow4.text));
-    . = ALIGN(64);
+    . = 0x40;
     KEEP(*(.WindowUnderflow4.text));
-    . = ALIGN(64);
+    . = 0x80;
     KEEP(*(.WindowOverflow8.text));
-    . = ALIGN(64);
+    . = 0xC0;
     KEEP(*(.WindowUnderflow8.text));
-    . = ALIGN(64);
+    . = 0x100;
     KEEP(*(.WindowOverflow12.text));
-    . = ALIGN(64);
+    . = 0x140;
     KEEP(*(.WindowUnderflow12.text));
-    . = ALIGN(64);
+    . = 0x180;
     KEEP(*(.Level2InterruptVector.text));
-    . = ALIGN(64);
+    . = 0x1C0;
     KEEP(*(.Level3InterruptVector.text));
-    . = ALIGN(64);
+    . = 0x200;
     KEEP(*(.Level4InterruptVector.text));
-    . = ALIGN(64);
+    . = 0x240;
     KEEP(*(.Level5InterruptVector.text));
-    . = ALIGN(64);
+    . = 0x280;
     KEEP(*(.DebugExceptionVector.text));
-    . = ALIGN(64);
+    . = 0x2C0;
     KEEP(*(.NMIExceptionVector.text));
-    . = ALIGN(64);
+    . = 0x300;
     KEEP(*(.KernelExceptionVector.text));
-    . = ALIGN(64);
+    . = 0x340;
     KEEP(*(.UserExceptionVector.text));
-    . = ALIGN(128);
+    /* mind the gap */
+    . = 0x3C0;
     KEEP(*(.DoubleExceptionVector.text));
-    . = ALIGN(64);
-    . = ALIGN(0x400);
+    . = 0x400;
     _init_end = ABSOLUTE(.);
   } > vectors_seg
 }