[GWP-ASan] Initial build files, implementation of PRNG [1].

Summary:
See D60593 for further information.
This patch slices off the PRNG implementation and the initial build files for GWP-ASan.

Reviewers: vlad.tsyrklevich, morehouse, vitalybuka

Reviewed By: morehouse

Subscribers: srhines, kubamracek, mgorny, #sanitizers, llvm-commits, cryptoad, eugenis

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D61867

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@360710 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 77 insertions, 0 deletions

diff --git a/lib/gwp_asan/CMakeLists.txt b/lib/gwp_asan/CMakeLists.txt
new file mode 100644
index 000000000..b8ab64dd2
--- /dev/null
+++ b/lib/gwp_asan/CMakeLists.txt
@@ -0,0 +1,36 @@
+add_compiler_rt_component(gwp_asan)
+
+include_directories(..)
+
+set(GWP_ASAN_SOURCES
+  random.cpp
+)
+
+set(GWP_ASAN_HEADERS
+  random.h
+)
+
+# Disable RTTI and exception support, as we want these libraries to be
+# C-compatible. Regular C source files can be linked against the generated
+# GwpAsan libraries using the Clang C compiler.
+set(GWP_ASAN_CFLAGS -fno-rtti -fno-exceptions)
+
+if (COMPILER_RT_HAS_GWP_ASAN)
+  foreach(arch ${GWP_ASAN_SUPPORTED_ARCH})
+    add_compiler_rt_runtime(
+      clang_rt.gwp_asan
+      STATIC
+      ARCHS ${arch}
+      SOURCES ${GWP_ASAN_SOURCES}
+      ADDITIONAL_HEADERS ${GWP_ASAN_HEADERS}
+      CFLAGS ${GWP_ASAN_CFLAGS}
+      PARENT_TARGET gwp_asan
+    )
+  endforeach()
+
+  add_compiler_rt_object_libraries(RTGwpAsan
+      ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
+      SOURCES ${GWP_ASAN_SOURCES}
+      ADDITIONAL_HEADERS ${GWP_ASAN_HEADERS}
+      CFLAGS ${GWP_ASAN_CFLAGS})
+endif()
diff --git a/lib/gwp_asan/random.cpp b/lib/gwp_asan/random.cpp
new file mode 100644
index 000000000..625973c48
--- /dev/null
+++ b/lib/gwp_asan/random.cpp
@@ -0,0 +1,21 @@
+//===-- random.cpp ----------------------------------------------*- C++ -*-===//
+//
+// 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 "gwp_asan/random.h"
+
+#include <ctime>
+
+namespace gwp_asan {
+uint32_t getRandomUnsigned32() {
+  thread_local uint32_t RandomState = static_cast<uint64_t>(time(nullptr));
+  RandomState ^= RandomState << 13;
+  RandomState ^= RandomState >> 17;
+  RandomState ^= RandomState << 5;
+  return RandomState;
+}
+} // namespace gwp_asan
diff --git a/lib/gwp_asan/random.h b/lib/gwp_asan/random.h
new file mode 100644
index 000000000..a71f3e59c
--- /dev/null
+++ b/lib/gwp_asan/random.h
@@ -0,0 +1,20 @@
+//===-- random.h ------------------------------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef GWP_ASAN_RANDOM_H_
+#define GWP_ASAN_RANDOM_H_
+
+#include <cstdint>
+
+namespace gwp_asan {
+// xorshift (32-bit output), extremely fast PRNG that uses arithmetic operations
+// only. Seeded using walltime.
+uint32_t getRandomUnsigned32();
+} // namespace gwp_asan
+
+#endif // GWP_ASAN_RANDOM_H_