From 0ea5772113684f5884b44cd7e76d45508ef3fbd7 Mon Sep 17 00:00:00 2001
From: Alexandre Julliard <julliard@winehq.org>
Date: Mon, 22 Mar 2021 20:38:25 +0100
Subject: [PATCH] ntdll: Use NtAreMappedFilesTheSame() to find duplicated
 module mappings.

Signed-off-by: Alexandre Julliard <julliard@winehq.org>
---
 dlls/ntdll/loader.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/dlls/ntdll/loader.c b/dlls/ntdll/loader.c
index 092c47eac3b..c7e7c86e88f 100644
--- a/dlls/ntdll/loader.c
+++ b/dlls/ntdll/loader.c
@@ -1167,6 +1167,8 @@ static WINE_MODREF *alloc_module( HMODULE hModule, const UNICODE_STRING *nt_name
     wm->ldr.Flags         = LDR_DONT_RESOLVE_REFS | (builtin ? LDR_WINE_INTERNAL : 0);
     wm->ldr.TlsIndex      = -1;
     wm->ldr.LoadCount     = 1;
+    wm->ldr.CheckSum      = nt->OptionalHeader.CheckSum;
+    wm->ldr.TimeDateStamp = nt->FileHeader.TimeDateStamp;
 
     if (!(buffer = RtlAllocateHeap( GetProcessHeap(), 0, nt_name->Length - 3 * sizeof(WCHAR) )))
     {
@@ -2274,6 +2276,33 @@ static NTSTATUS open_dll_file( UNICODE_STRING *nt_name, WINE_MODREF **pwm, HANDL
 }
 
 
+/******************************************************************************
+ *	find_existing_module
+ *
+ * Find an existing module that is the same mapping as the new module.
+ */
+static WINE_MODREF *find_existing_module( HMODULE module )
+{
+    WINE_MODREF *wm;
+    LIST_ENTRY *mark, *entry;
+    LDR_DATA_TABLE_ENTRY *mod;
+    IMAGE_NT_HEADERS *nt = RtlImageNtHeader( module );
+
+    if ((wm = get_modref( module ))) return wm;
+
+    mark = &NtCurrentTeb()->Peb->LdrData->InMemoryOrderModuleList;
+    for (entry = mark->Flink; entry != mark; entry = entry->Flink)
+    {
+        mod = CONTAINING_RECORD( entry, LDR_DATA_TABLE_ENTRY, InMemoryOrderLinks );
+        if (mod->TimeDateStamp != nt->FileHeader.TimeDateStamp) continue;
+        if (mod->CheckSum != nt->OptionalHeader.CheckSum) continue;
+        if (NtAreMappedFilesTheSame( mod->DllBase, module ) != STATUS_SUCCESS) continue;
+        return CONTAINING_RECORD( mod, WINE_MODREF, ldr );
+    }
+    return NULL;
+}
+
+
 /******************************************************************************
  *	load_native_dll  (internal)
  */
@@ -2351,12 +2380,13 @@ static NTSTATUS load_builtin_dll( LPCWSTR load_path, UNICODE_STRING *nt_name,
     status = unix_funcs->load_builtin_dll( nt_name, &module, &image_info, prefer_native );
     if (status) return status;
 
-    if ((*pwm = get_modref( module )))  /* already loaded */
+    if ((*pwm = find_existing_module( module )))  /* already loaded */
     {
         if ((*pwm)->ldr.LoadCount != -1) (*pwm)->ldr.LoadCount++;
         TRACE( "Found %s for %s at %p, count=%d\n",
                debugstr_us(&(*pwm)->ldr.FullDllName), debugstr_us(nt_name),
                (*pwm)->ldr.DllBase, (*pwm)->ldr.LoadCount);
+        if (module != (*pwm)->ldr.DllBase) NtUnmapViewOfSection( NtCurrentProcess(), module );
         return STATUS_SUCCESS;
     }