From 32c349d30ed6b08f9c277ca22593479361791494 Mon Sep 17 00:00:00 2001
From: Timo Kreuzer <timo.kreuzer@reactos.org>
Date: Thu, 30 Jan 2025 10:11:38 +0200
Subject: [PATCH] [VCRUNTIME] Add TLS callback support

---
 sdk/lib/vcruntime/CMakeLists.txt        |  1 +
 sdk/lib/vcruntime/inc/internal_shared.h | 16 +++++++++++
 sdk/lib/vcruntime/tlssup.c              | 38 +++++++++++++++++++++++++
 3 files changed, 55 insertions(+)
 create mode 100644 sdk/lib/vcruntime/tlssup.c

diff --git a/sdk/lib/vcruntime/CMakeLists.txt b/sdk/lib/vcruntime/CMakeLists.txt
index 21630765497..633a1b7a466 100644
--- a/sdk/lib/vcruntime/CMakeLists.txt
+++ b/sdk/lib/vcruntime/CMakeLists.txt
@@ -24,6 +24,7 @@ list(APPEND VCRT_COMMON_SOURCES
     _fltused.c
     initializers.cpp
     isa_available.cpp
+    tlssup.c
 )
 
 list(APPEND VCRT_RUNTIME_SOURCES
diff --git a/sdk/lib/vcruntime/inc/internal_shared.h b/sdk/lib/vcruntime/inc/internal_shared.h
index 892799639fc..968f5ecb498 100644
--- a/sdk/lib/vcruntime/inc/internal_shared.h
+++ b/sdk/lib/vcruntime/inc/internal_shared.h
@@ -38,6 +38,20 @@ extern "C" {
 #pragma section(".CRT$XPZ", long, read)
 #pragma section(".CRT$XTA", long, read)
 #pragma section(".CRT$XTZ", long, read)
+
+
+#pragma section(".CRT$XDA",long,read)
+#pragma section(".CRT$XDC",long,read)
+#pragma section(".CRT$XDZ",long,read)
+
+#pragma section(".CRT$XLA",long,read) // TLS callback start
+#pragma section(".CRT$XLC",long,read) // TLS constructors
+#pragma section(".CRT$XLD",long,read) // TLS destructors
+#pragma section(".CRT$XLZ",long,read) // TLS callback end
+
+#pragma section(".tls",long,read,write)
+#pragma section(".tls$AAA",long,read,write)
+#pragma section(".tls$ZZZ",long,read,write)
 #endif
 
 extern _PIFV __xi_a[];
@@ -51,6 +65,8 @@ extern _PVFV __xt_z[];
 
 extern char __ImageBase;
 
+extern const IMAGE_TLS_DIRECTORY _tls_used;
+
 #define CRT_WARNING_DISABLE_PUSH(wn, message) \
     __pragma(warning(push)) \
     __pragma(warning(disable: wn))
diff --git a/sdk/lib/vcruntime/tlssup.c b/sdk/lib/vcruntime/tlssup.c
new file mode 100644
index 00000000000..ba3f97ba1ce
--- /dev/null
+++ b/sdk/lib/vcruntime/tlssup.c
@@ -0,0 +1,38 @@
+//
+// tlssup.c
+//
+//      Copyright (c) 2025 Timo Kreuzer
+//
+// TLS callback support
+//
+// SPDX-License-Identifier: MIT
+//
+
+#include <internal_shared.h>
+
+// Dummy TLS undex
+unsigned int _tls_index;
+
+// The TLS data
+_CRTALLOC(".tls") char *_tls_start = NULL;
+_CRTALLOC(".tls$ZZZ") char *_tls_end = NULL;
+
+// Describes the range of TLS callbacks.
+_CRTALLOC(".CRT$XLA") PIMAGE_TLS_CALLBACK __xl_a = 0;
+_CRTALLOC(".CRT$XLZ") PIMAGE_TLS_CALLBACK __xl_z = 0;
+
+//
+// The TLS directory.
+// The linker will point the executables TLS data directory entry to this.
+// Must be force-included with "#pragma comment(linker, "/INCLUDE:_tls_used")"
+// or by referencing it from another compilation unit.
+//
+const IMAGE_TLS_DIRECTORY _tls_used =
+{
+    (ULONG_PTR)&_tls_start,
+    (ULONG_PTR)&_tls_end,
+    (ULONG_PTR)&_tls_index,
+    (ULONG_PTR)(&__xl_a + 1),
+    (ULONG)0,
+    (ULONG)0
+};