Improved OEPal integration with the new snmalloc architecture (#346)

* Improved OEPal integration with the new snmalloc architecture

* Applied PR feedback

src/pal/pal.h

@@ -16,11 +16,11 @@
 #  include "pal_haiku.h"
 #  include "pal_linux.h"
 #  include "pal_netbsd.h"
-#  include "pal_noalloc.h"
 #  include "pal_openbsd.h"
 #  include "pal_solaris.h"
 #  include "pal_windows.h"
 #endif
+#include "pal_noalloc.h"
 #include "pal_plain.h"
 
 namespace snmalloc
@@ -56,7 +56,7 @@ namespace snmalloc
 #if defined(SNMALLOC_MEMORY_PROVIDER)
     PALPlainMixin<SNMALLOC_MEMORY_PROVIDER>;
 #elif defined(OPEN_ENCLAVE)
-    PALPlainMixin<PALOpenEnclave>;
+    PALOpenEnclave;
 #else
     DefaultPal;
 #endif

src/pal/pal_open_enclave.h

@@ -1,10 +1,7 @@
 #pragma once
 
-#include "ds/address.h"
-#include "ds/flaglock.h"
-#include "pal_plain.h"
+#include "pal_noalloc.h"
 
-#include <array>
 #ifdef OPEN_ENCLAVE
 extern "C" void* oe_memset_s(void* p, size_t p_size, int c, size_t size);
 extern "C" int oe_random(void* data, size_t size);
@@ -12,55 +9,29 @@ extern "C" [[noreturn]] void oe_abort();
 
 namespace snmalloc
 {
-  class PALOpenEnclave
+  class OpenEnclaveErrorHandler
   {
-    /// Base of OE heap
-    static inline void* heap_base = nullptr;
-
-    /// Size of OE heap
-    static inline size_t heap_size;
-
-    // This is infrequently used code, a spin lock simplifies the code
-    // considerably, and should never be on the fast path.
-    static inline std::atomic_flag spin_lock;
-
   public:
-    /**
-     * This will be called by oe_allocator_init to set up enclave heap bounds.
-     */
-    static void setup_initial_range(void* base, void* end)
-    {
-      heap_size = pointer_diff(base, end);
-      heap_base = base;
-    }
-
-    /**
-     * Bitmap of PalFeatures flags indicating the optional features that this
-     * PAL supports.
-     */
-    static constexpr uint64_t pal_features = Entropy;
-
-    static constexpr size_t page_size = Aal::smallest_page_size;
+    static void print_stack_trace() {}
 
     [[noreturn]] static void error(const char* const str)
     {
       UNUSED(str);
       oe_abort();
     }
+  };
 
-    static std::pair<void*, size_t>
-    reserve_at_least(size_t request_size) noexcept
-    {
-      // First call returns the entire address space
-      // subsequent calls return {nullptr, 0}
-      FlagLock lock(spin_lock);
-      if (request_size > heap_size)
-        return {nullptr, 0};
+  using OpenEnclaveBasePAL = PALNoAlloc<OpenEnclaveErrorHandler>;
 
-      auto result = std::make_pair(heap_base, heap_size);
-      heap_size = 0;
-      return result;
-    }
+  class PALOpenEnclave : public OpenEnclaveBasePAL
+  {
+  public:
+    /**
+     * Bitmap of PalFeatures flags indicating the optional features that this
+     * PAL supports.
+     */
+    static constexpr uint64_t pal_features =
+      OpenEnclaveBasePAL::pal_features | Entropy;
 
     template<bool page_aligned = false>
     static void zero(void* p, size_t size) noexcept