[libc] add simple tests for vDSO symbols

Author: SchrodingerZhu

libc/test/src/__support/OSUtil/linux/CMakeLists.txt

@@ -1,3 +1,12 @@
 if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
   add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
 endif()
+
+add_libc_test(
+  vdso_test
+  SUITE libc-osutil-tests
+  SRCS vdso_test.cpp
+  DEPENDS
+    libc.src.__support.OSUtil.vdso
+    libc.include.llvm-libc-types.struct_timeval # TODO: update this to proxy header once available
+)

libc/test/src/__support/OSUtil/linux/vdso_test.cpp

@@ -0,0 +1,33 @@
+//===-- Unittests for x86_64 syscalls -------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-libc-types/struct_timeval.h"
+#include "src/__support/OSUtil/vdso.h"
+#include "test/UnitTest/Test.h"
+
+namespace LIBC_NAMESPACE {
+TEST(LlvmLibcOSUtilVDSOTest, SymbolsDefined) {
+  // for now, we simply test all symbols are provided.
+  for (size_t i = 0; i < static_cast<size_t>(vdso::VDSOSym::VDSOSymCount); ++i)
+    EXPECT_NE(vdso::get_symbol(static_cast<vdso::VDSOSym>(i)),
+              static_cast<void *>(nullptr));
+}
+
+#ifdef LIBC_VDSO_HAS_GETTIMEOFDAY
+TEST(LlvmLibcOSUtilVDSOTest, GetTimeOfDay) {
+  using FuncTy = int (*)(timeval *, struct timezone *);
+  auto func =
+      reinterpret_cast<FuncTy>(vdso::get_symbol(vdso::VDSOSym::GetTimeOfDay));
+  timeval tv;
+  EXPECT_EQ(func(&tv, nullptr), 0);
+  // hopefully people are not building time machines using our libc.
+  EXPECT_GT(tv.tv_sec, static_cast<decltype(tv.tv_sec)>(0));
+}
+#endif
+
+} // namespace LIBC_NAMESPACE