From fd669773b69edac5bf0bdd7ab27b709be7dc0777 Mon Sep 17 00:00:00 2001
From: Marek Roszko <mark.roszko@gmail.com>
Date: Tue, 13 Jun 2023 20:41:31 -0400
Subject: [PATCH] Use guarded pages for coroutine stack on windows

---
 include/tool/coroutine.h | 59 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

diff --git a/include/tool/coroutine.h b/include/tool/coroutine.h
index fe086ef413..b40c2d9812 100644
--- a/include/tool/coroutine.h
+++ b/include/tool/coroutine.h
@@ -49,6 +49,11 @@
 #include <trace_helpers.h>
 #include <wx/log.h>
 
+#ifdef _WIN32
+#include <optional>
+#include <windows.h>
+#endif
+
 /**
  *  Implement a coroutine.
  *
@@ -186,7 +191,10 @@ public:
     /**
      * Create a coroutine from a delegate object.
      */
-    COROUTINE( std::function<ReturnType(ArgType)> aEntry ) :
+    COROUTINE( std::function<ReturnType( ArgType )> aEntry ) :
+#ifdef _WIN32
+        m_stack( nullptr ),
+#endif
         m_func( std::move( aEntry ) ),
         m_running( false ),
         m_args( nullptr ),
@@ -215,6 +223,11 @@ public:
 
         if( m_callee.ctx )
             libcontext::release_fcontext( m_callee.ctx );
+
+#ifdef _WIN32
+        if( m_stack )
+            ::VirtualFree( m_stack, 0, MEM_RELEASE );
+#endif
     }
 
 public:
@@ -375,7 +388,46 @@ private:
         void* sp = nullptr;
 
 #ifndef LIBCONTEXT_HAS_OWN_STACK
+#ifdef _WIN32
+        // kind of a hack to avoid calling into GetSystemInfo constantly for page size
+        static std::optional<std::size_t> system_page_size;
+        if( !system_page_size.has_value() )
+        {
+            // For Windows, we want to use VirtualAlloc and VirtualProtect which let us
+            // trap stack overflows with the guard page, it'll still crash but this
+            // has a chance of preserving stack in dumps
+            SYSTEM_INFO si;
+            ::GetSystemInfo( &si );
 
+            system_page_size = static_cast<std::size_t>( si.dwPageSize );
+        }
+
+        // this shouldn't happen but just incase
+        if( m_stack )
+            ::VirtualFree( m_stack, 0, MEM_RELEASE );
+
+        // calculate the correct number of pages to allocate based on request stack size
+        std::size_t pages = ( m_stacksize + system_page_size.value() - 1 ) / system_page_size.value();
+
+        // we allocate an extra page for the guard
+        std::size_t alloc_size = ( pages + 1 ) * system_page_size.value();
+
+        m_stack = ::VirtualAlloc( 0, alloc_size, MEM_COMMIT, PAGE_READWRITE );
+        if( !m_stack )
+            throw std::bad_alloc();
+
+        // now configure the first page (by only specifying a single page_size from vp)
+        // that will act as the guard page
+        // the stack will grow from the end and hopefully never into this guarded region
+        DWORD      old_prot; // dummy var since the arg cannot be NULL
+        const BOOL res = ::VirtualProtect( m_stack, system_page_size.value(),
+                                           PAGE_READWRITE | PAGE_GUARD, &old_prot );
+
+        assert( res != false );
+
+        stackSize = alloc_size;
+        sp = static_cast<char*>( m_stack ) + stackSize;
+#else
         // fixme: Clean up stack stuff. Add a guard
         m_stack.reset( new char[stackSize] );
 
@@ -389,6 +441,7 @@ private:
         m_valgrind_stack = VALGRIND_STACK_REGISTER( sp, m_stack.get() );
 #endif
 #endif
+#endif
 
 #ifdef KICAD_SANITIZE_THREADS
         // Create a new fiber to go with the new context
@@ -475,7 +528,11 @@ private:
     }
 
     ///< coroutine stack
+#ifdef _WIN32
+    void* m_stack;
+#else
     std::unique_ptr<char[]> m_stack;
+#endif
 
     int m_stacksize;