[nsan] Add nsan_preinit.cpp and make it static library only

#94322 defines .preinit_array to initialize nsan early.
DT_PREINIT_ARRAY can only be used with the main executable. GNU ld would
complain when a DSO has .preinit_array .

Author: MaskRay

compiler-rt/lib/nsan/CMakeLists.txt

@@ -11,6 +11,9 @@ set(NSAN_SOURCES
   nsan_suppressions.cpp
 )
 
+set(NSAN_PREINIT_SOURCES
+  nsan_preinit.cpp)
+
 set(NSAN_HEADERS
   nsan.h
   nsan_flags.h
@@ -61,6 +64,12 @@ if(NOT APPLE)
       ADDITIONAL_HEADERS ${NSAN_HEADERS}
       CFLAGS ${NSAN_CFLAGS})
 
+  add_compiler_rt_object_libraries(RTNsan_preinit
+    ARCHS ${NSAN_SUPPORTED_ARCH}
+    SOURCES ${NSAN_PREINIT_SOURCES}
+    ADDITIONAL_HEADERS ${NSAN_HEADERS}
+    CFLAGS ${NSAN_CFLAGS})
+
   file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp "")
   add_compiler_rt_object_libraries(RTNsan_dynamic_version_script_dummy
     ARCHS ${NSAN_SUPPORTED_ARCH}
@@ -72,7 +81,7 @@ add_compiler_rt_runtime(
   clang_rt.nsan
   STATIC
   ARCHS ${NSAN_SUPPORTED_ARCH}
-  OBJECT_LIBS RTNsan
+  OBJECT_LIBS RTNsan_preinit RTNsan
               ${NSAN_COMMON_RUNTIME_OBJECT_LIBS}
   CFLAGS ${NSAN_CFLAGS}
   PARENT_TARGET nsan)

compiler-rt/lib/nsan/nsan.cpp

@@ -779,7 +779,7 @@ extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __nsan_dump_shadow_args() {
 bool __nsan::nsan_initialized;
 bool __nsan::nsan_init_is_running;
 
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __nsan_init() {
+extern "C" void __nsan_init() {
   CHECK(!nsan_init_is_running);
   if (nsan_initialized)
     return;
@@ -801,8 +801,3 @@ extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __nsan_init() {
   nsan_init_is_running = false;
   nsan_initialized = true;
 }
-
-#if SANITIZER_CAN_USE_PREINIT_ARRAY
-__attribute__((section(".preinit_array"),
-               used)) static void (*nsan_init_ptr)() = __nsan_init;
-#endif

compiler-rt/lib/nsan/nsan.h

@@ -32,6 +32,8 @@ using __sanitizer::uptr;
 // Private nsan interface. Used e.g. by interceptors.
 extern "C" {
 
+void __nsan_init();
+
 // This marks the shadow type of the given block of application memory as
 // unknown.
 // printf-free (see comment in nsan_interceptors.cc).

compiler-rt/lib/nsan/nsan_preinit.cpp

@@ -0,0 +1,21 @@
+//===- nsan_preinit.cpp ---------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Call __nsan_init early using ELF DT_PREINIT_ARRAY.
+//
+//===----------------------------------------------------------------------===//
+
+#include "nsan/nsan.h"
+#include "sanitizer_common/sanitizer_internal_defs.h"
+
+#if SANITIZER_CAN_USE_PREINIT_ARRAY
+
+__attribute__((section(".preinit_array"), used)) static auto nsan_preinit =
+    __nsan_init;
+
+#endif