[NTOS:CM] Implement Win7+ VolatileBoot support.

Its support is controlled with a REG_DWORD value named
`VolatileBoot` inside the registry key
`HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Configuration Manager` .

Its implementation is very trivial: when enabled, CmpShareSystemHives
is set to TRUE and doesn't change state during runtime.
In a sense this is similar to what happens in WinPE-boot, except that
ALL hives without exception (system hives and others) will be loaded
in shared mode.

ntoskrnl/config/cmdata.c

@@ -54,6 +54,8 @@ UNICODE_STRING CmSymbolicLinkValueName =
 
 UNICODE_STRING CmpLoadOptions;
 
+/* TRUE if all hives must be loaded in shared mode */
+ULONG CmpVolatileBoot;
 /* TRUE if the system hives must be loaded in shared mode */
 BOOLEAN CmpShareSystemHives;
 /* TRUE when the registry is in PE mode */
@@ -673,6 +675,13 @@ DATA_SEG("INITDATA") CM_SYSTEM_CONTROL_VECTOR CmControlVector[] =
         NULL,
         NULL
     },
+    {
+        L"Session Manager\\Configuration Manager",
+        L"VolatileBoot",
+        &CmpVolatileBoot,
+        NULL,
+        NULL
+    },
     {
         L"Session Manager",
         L"ForceNpxEmulation",

ntoskrnl/config/cmsysini.c

@@ -1164,7 +1164,7 @@ CmpCreateRegistryRoot(VOID)
         return FALSE;
     }
 
-    /* Completely sucessful */
+    /* Completely successful */
     return TRUE;
 }
 
@@ -1635,6 +1635,10 @@ CmInitSystem1(VOID)
         CmpMiniNTBoot = TRUE;
         CmpShareSystemHives = TRUE;
     }
+    /* If we are in volatile boot mode, ALL hives without exception
+     * (system hives and others) will be loaded in shared mode */
+    if (CmpVolatileBoot)
+        CmpShareSystemHives = TRUE;
 
     /* Initialize the hive list and lock */
     InitializeListHead(&CmpHiveListHead);

ntoskrnl/include/internal/cm.h

@@ -1420,6 +1420,7 @@ CmGetSystemDriverList(
 extern ULONG CmpTraceLevel;
 extern BOOLEAN CmpSpecialBootCondition;
 extern BOOLEAN CmpFlushOnLockRelease;
+extern ULONG CmpVolatileBoot;
 extern BOOLEAN CmpShareSystemHives;
 extern BOOLEAN CmpMiniNTBoot;
 extern BOOLEAN CmpNoVolatileCreates;