From c1062e629eaa4d270ec1834d19e38bf6587a5c11 Mon Sep 17 00:00:00 2001
From: Matthew Parkinson <mattpark@microsoft.com>
Date: Wed, 20 Oct 2021 16:54:45 +0100
Subject: [PATCH] Add Madvise free to Linux layer

---
 src/pal/pal_linux.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/pal/pal_linux.h b/src/pal/pal_linux.h
index 8104b33..f597ff1 100644
--- a/src/pal/pal_linux.h
+++ b/src/pal/pal_linux.h
@@ -65,6 +65,26 @@ namespace snmalloc
         ::memset(p, 0, size);
       }
     }
+
+    static void notify_not_using(void* p, size_t size) noexcept
+    {
+      SNMALLOC_ASSERT(is_aligned_block<page_size>(p, size));
+
+      if constexpr (PalEnforceAccess)
+      {
+#  if !defined(NDEBUG)
+        // Fill memory so that when we switch the pages back on we don't make
+        // assumptions on the content.
+        memset(p, 0x5a, size);
+#  endif
+        madvise(p, size, MADV_FREE);
+        mprotect(p, size, PROT_NONE);
+      }
+      else
+      {
+        madvise(p, size, MADV_FREE);
+      }
+    }
   };
 } // namespace snmalloc
 #endif