From 64dad88a32b7f6d4767e992963d5d24921adfc40 Mon Sep 17 00:00:00 2001
From: pca006132 <john.lck40@gmail.com>
Date: Thu, 23 Jul 2020 14:03:23 +0800
Subject: [PATCH] Kernel exception: fixed top level finally. (#70)

Fixes #70.
---
 src/llvm_libunwind/src/Unwind-EHABI.cpp |  5 +++++
 src/runtime/src/eh_artiq.rs             | 21 +++++++++++++--------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/llvm_libunwind/src/Unwind-EHABI.cpp b/src/llvm_libunwind/src/Unwind-EHABI.cpp
index bfa4b303..14bc15f7 100644
--- a/src/llvm_libunwind/src/Unwind-EHABI.cpp
+++ b/src/llvm_libunwind/src/Unwind-EHABI.cpp
@@ -551,6 +551,7 @@ static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor
                              static_cast<void *>(exception_object));
   int frame_count = 0;
 
+  unw_word_t prev_sp = 0x0;
   // Walk each frame until we reach where search phase said to stop.
   while (true) {
     // Ask libunwind to get next frame (skip over first which is
@@ -576,6 +577,10 @@ static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor
     unw_word_t sp;
     unw_proc_info_t frameInfo;
     __unw_get_reg(cursor, UNW_REG_SP, &sp);
+    if (sp == prev_sp) {
+        return _URC_END_OF_STACK;
+    }
+    prev_sp = sp;
     if (__unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
       _LIBUNWIND_TRACE_UNWINDING(
           "unwind_phase2(ex_ojb=%p): __unw_get_proc_info "
diff --git a/src/runtime/src/eh_artiq.rs b/src/runtime/src/eh_artiq.rs
index f4ca871e..41938517 100644
--- a/src/runtime/src/eh_artiq.rs
+++ b/src/runtime/src/eh_artiq.rs
@@ -128,8 +128,15 @@ pub unsafe fn artiq_personality(state: uw::_Unwind_State,
     let exception = &exception_info.exception.unwrap();
     if search_phase {
         match eh_action {
-            EHAction::None |
-            EHAction::Cleanup(_) => return continue_unwind(exception_object, context),
+            EHAction::None => return continue_unwind(exception_object, context),
+            // Actually, cleanup should not return handler found, this is to workaround
+            // the issue of terminating directly when no catch cause is found while
+            // having some cleanup routines defined by finally.
+            // The best way to handle this is to force unwind the stack in the raise
+            // function when end of stack is reached, and call terminate at the end of
+            // the unwind. Unfortunately, there is no forced unwind function defined
+            // for EHABI, and I have no idea how to implement that, so this is a hack.
+            EHAction::Cleanup(_) => return uw::_URC_HANDLER_FOUND,
             EHAction::Catch(_) => {
                 // EHABI requires the personality routine to update the
                 // SP value in the barrier cache of the exception object.
@@ -195,10 +202,9 @@ static mut INFLIGHT: ExceptionInfo = ExceptionInfo {
 };
 
 pub unsafe extern fn raise(exception: *const Exception) -> ! {
-    // Zing! The Exception<'a> to Exception<'static> transmute is not really sound in case
-    // the exception is ever captured. Fortunately, they currently aren't, and we save
-    // on the hassle of having to allocate exceptions somewhere except on stack.
     trace!("Trying to raise exception");
+    // FIXME: unsound transmute
+    // This would cause stack memory corruption.
     INFLIGHT.exception = Some(mem::transmute::<Exception, Exception<'static>>(*exception));
     INFLIGHT.handled   = false;
 
@@ -219,9 +225,8 @@ pub unsafe extern fn raise(exception: *const Exception) -> ! {
 pub unsafe extern fn reraise() -> ! {
     use cslice::AsCSlice;
 
-    trace!("Re-raise");
-    // current implementation uses raise as _Unwind_Resume is not working now
-    // would debug that later.
+    // Reraise is basically cxa_rethrow, which calls _Unwind_Resume_or_Rethrow,
+    // which for EHABI would always call _Unwind_RaiseException.
     match INFLIGHT.exception {
         Some(ref exception) => raise(exception),
         None => raise(&Exception {