From cf9b6290c7c9104deaab477f7a5f074d7ee30e63 Mon Sep 17 00:00:00 2001
From: David CARLIER <devnexen@gmail.com>
Date: Fri, 4 Mar 2022 11:29:11 +0000
Subject: [PATCH] =?UTF-8?q?Follow-up=20on=20#469=20for=20Linux=20this=20ti?=
 =?UTF-8?q?me,=20overriding=20read=20only=20pages=20cod=E2=80=A6=20(#471)?=
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* Follow-up on #469 for Linux this time, overriding read only pages code path too.
---
 src/pal/pal_linux.h | 48 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 38 insertions(+), 10 deletions(-)

diff --git a/src/pal/pal_linux.h b/src/pal/pal_linux.h
index 139a6af..aa28ded 100644
--- a/src/pal/pal_linux.h
+++ b/src/pal/pal_linux.h
@@ -34,6 +34,14 @@ namespace snmalloc
      */
     static constexpr int default_mmap_flags = MAP_NORESERVE;
 
+    static void* reserve(size_t size) noexcept
+    {
+      void* p = PALPOSIX<PALLinux>::reserve(size);
+      if (p)
+        madvise(p, size, MADV_DONTDUMP);
+      return p;
+    }
+
     /**
      * OS specific function for zeroing memory.
      *
@@ -68,20 +76,40 @@ namespace snmalloc
     {
       SNMALLOC_ASSERT(is_aligned_block<page_size>(p, size));
 
+      // Fill memory so that when we switch the pages back on we don't make
+      // assumptions on the content.
+      if constexpr (DEBUG)
+        memset(p, 0x5a, size);
+
+      madvise(p, size, MADV_DONTDUMP);
+      madvise(p, size, MADV_FREE);
+
       if constexpr (PalEnforceAccess)
       {
-        // Fill memory so that when we switch the pages back on we don't make
-        // assumptions on the content.
-        if constexpr (DEBUG)
-          memset(p, 0x5a, size);
-
-        madvise(p, size, MADV_FREE);
         mprotect(p, size, PROT_NONE);
       }
-      else
-      {
-        madvise(p, size, MADV_FREE);
-      }
+    }
+
+    /**
+     * Notify platform that we will be using these pages for reading.
+     *
+     * This is used only for pages full of zeroes and so we exclude them from
+     * core dumps.
+     */
+    static void notify_using_readonly(void* p, size_t size) noexcept
+    {
+      PALPOSIX<PALLinux>::notify_using_readonly(p, size);
+      madvise(p, size, MADV_DONTDUMP);
+    }
+
+    /**
+     * Notify platform that we will be using these pages.
+     */
+    template<ZeroMem zero_mem>
+    static void notify_using(void* p, size_t size) noexcept
+    {
+      PALPOSIX<PALLinux>::notify_using<zero_mem>(p, size);
+      madvise(p, size, MADV_DODUMP);
     }
 
     static uint64_t get_entropy64()