Various fixes for OE (#418)

* Add default for getting chunk allocator state

Makes the API same between the two configurations.

* Reduce address space usage for Open Enclave

* Fix OE Pal concept

* Add support for Pal not to provide time.

The lazy return of pages to the OS uses a simple time
based heuristic.  This enables a PAL to not support time,
and return the memory to a central pool immediately.

* Update src/backend/backend.h

Co-authored-by: Amaury Chamayou <amaury@xargs.fr>

Co-authored-by: Amaury Chamayou <amaury@xargs.fr>

src/pal/pal_apple.h

@@ -28,7 +28,7 @@ namespace snmalloc
      * The features exported by this PAL.
      */
     static constexpr uint64_t pal_features =
-      AlignedAllocation | LazyCommit | Entropy;
+      AlignedAllocation | LazyCommit | Entropy | Time;
 
     /*
      * `page_size`

src/pal/pal_consts.h

@@ -41,6 +41,7 @@ namespace snmalloc
      * whether low memory conditions are still in effect.
      */
     LowMemoryNotification = (1 << 0),
+
     /**
      * This PAL natively supports allocation with a guaranteed alignment.  If
      * this is not supported, then we will over-allocate and round the
@@ -51,22 +52,31 @@ namespace snmalloc
      * `request()` method that takes only a size.
      */
     AlignedAllocation = (1 << 1),
+
     /**
      * This PAL natively supports lazy commit of pages. This means have large
      * allocations and not touching them does not increase memory usage. This is
      * exposed in the Pal.
      */
     LazyCommit = (1 << 2),
+
     /**
      * This Pal does not support allocation.  All memory used with this Pal
      * should be pre-allocated.
      */
     NoAllocation = (1 << 3),
+
     /**
      * This Pal provides a source of Entropy
      */
     Entropy = (1 << 4),
+
+    /**
+     * This Pal provides a millisecond time source
+     */
+    Time = (1 << 5),
   };
+
   /**
    * Flag indicating whether requested memory should be zeroed.
    */
@@ -76,6 +86,7 @@ namespace snmalloc
      * Memory should not be zeroed, contents are undefined.
      */
     NoZero,
+
     /**
      * Memory must be zeroed.  This can be lazily allocated via a copy-on-write
      * mechanism as long as any load from the memory returns zero.

src/pal/pal_noalloc.h

@@ -28,7 +28,7 @@ namespace snmalloc
    * ever use.
    */
   template<SNMALLOC_CONCEPT(PALNoAllocBase) BasePAL>
-  struct PALNoAlloc : public PalTimerDefaultImpl<BasePAL>
+  struct PALNoAlloc : public BasePAL
   {
     /**
      * Bitmap of PalFeatures flags indicating the optional features that this
@@ -38,7 +38,7 @@ namespace snmalloc
 
     static constexpr size_t page_size = BasePAL::page_size;
 
-    static constexpr size_t address_bits = Aal::address_bits;
+    static constexpr size_t address_bits = BasePAL::address_bits;
 
     /**
      * Print a stack trace.

src/pal/pal_open_enclave.h

@@ -19,6 +19,8 @@ namespace snmalloc
       UNUSED(str);
       oe_abort();
     }
+    static constexpr size_t address_bits = Aal::address_bits;
+    static constexpr size_t page_size = Aal::smallest_page_size;
   };
 
   using OpenEnclaveBasePAL = PALNoAlloc<OpenEnclaveErrorHandler>;

src/pal/pal_posix.h

@@ -125,7 +125,7 @@ namespace snmalloc
      * POSIX systems are assumed to support lazy commit. The build system checks
      * getentropy is available, only then this PAL supports Entropy.
      */
-    static constexpr uint64_t pal_features = LazyCommit
+    static constexpr uint64_t pal_features = LazyCommit | Time
 #if defined(SNMALLOC_PLATFORM_HAS_GETENTROPY)
       | Entropy
 #endif

src/pal/pal_windows.h

@@ -55,7 +55,8 @@ namespace snmalloc
      * Bitmap of PalFeatures flags indicating the optional features that this
      * PAL supports.  This PAL supports low-memory notifications.
      */
-    static constexpr uint64_t pal_features = LowMemoryNotification | Entropy
+    static constexpr uint64_t pal_features = LowMemoryNotification | Entropy |
+      Time
 #  if defined(PLATFORM_HAS_VIRTUALALLOC2) && !defined(USE_SYSTEMATIC_TESTING)
       | AlignedAllocation
 #  endif