From e486af700c822704d24f50a875c0bb0bdda18052 Mon Sep 17 00:00:00 2001
From: Evan Brown <ezb@google.com>
Date: Mon, 24 Jun 2024 14:53:09 -0700
Subject: Add an internal API to get a poisoned pointer.

The motivation is to make destroyed/moved-from objects cause crashes when they are accessed.

PiperOrigin-RevId: 646229564
Change-Id: I68d9c189b542df0933af08f5ad63dc1f5764d856
---
 absl/base/internal/poison.cc | 79 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 absl/base/internal/poison.cc

(limited to 'absl/base/internal/poison.cc')

diff --git a/absl/base/internal/poison.cc b/absl/base/internal/poison.cc
new file mode 100644
index 00000000..c6d8f8ee
--- /dev/null
+++ b/absl/base/internal/poison.cc
@@ -0,0 +1,79 @@
+// Copyright 2024 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/base/internal/poison.h"
+
+#include <atomic>
+#include <cstdint>  // NOLINT - used in ifdef
+#include <cstdlib>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER)
+#include <sanitizer/asan_interface.h>
+#elif defined(ABSL_HAVE_MEMORY_SANITIZER)
+#include <sanitizer/msan_interface.h>
+#elif defined(ABSL_HAVE_MMAP) && !defined(SGX_SIM)
+#include <sys/mman.h>
+#elif defined(_MSC_VER)
+#include <windows.h>
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace base_internal {
+namespace {
+constexpr size_t kPageSize = 1 << 12;
+alignas(kPageSize) static char poison_page[kPageSize];
+}  // namespace
+
+std::atomic<void*> poison_data = {&poison_page};
+
+namespace {
+
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER)
+void PoisonBlock(void* data) { ASAN_POISON_MEMORY_REGION(data, kPageSize); }
+#elif defined(ABSL_HAVE_MEMORY_SANITIZER)
+void PoisonBlock(void* data) { __msan_poison(data, kPageSize); }
+#elif defined(ABSL_HAVE_MMAP)
+void PoisonBlock(void* data) { mprotect(data, kPageSize, PROT_NONE); }
+#elif defined(_MSC_VER)
+void PoisonBlock(void* data) {
+  DWORD old_mode = 0;
+  VirtualProtect(data, kPageSize, PAGE_NOACCESS, &old_mode);
+}
+#else
+void PoisonBlock(void* data) {
+  // We can't make poisoned memory, so just use a likely bad pointer.
+  // Pointers are required to have high bits that are all zero or all one for
+  // certain 64-bit CPUs. This pointer value will hopefully cause a crash on
+  // dereference and also be clearly recognizable as invalid.
+  constexpr uint64_t kBadPtr = 0xBAD0BAD0BAD0BAD0;
+  poison_data = reinterpret_cast<void*>(static_cast<uintptr_t>(kBadPtr));
+}
+#endif
+
+void* InitializePoisonedPointer() {
+  PoisonBlock(&poison_page);
+  return &poison_page;
+}
+
+}  // namespace
+
+ABSL_ATTRIBUTE_UNUSED void* force_initialize = InitializePoisonedPointer();
+
+}  // namespace base_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
-- 
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