From 5b6285e7c5548adf74396650c473efb163363705 Mon Sep 17 00:00:00 2001
From: Evan Brown <ezb@google.com>
Date: Wed, 10 Jul 2024 12:44:39 -0700
Subject: Roll forward poisoned pointer API and fix portability issues.

Also, return the middle of the poisoned block.

PiperOrigin-RevId: 651119057
Change-Id: Iae0fc3dcb40e32cd449f469d9b8d62c37f3773f4
---
 absl/base/internal/poison.cc | 82 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 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..9afa0687
--- /dev/null
+++ b/absl/base/internal/poison.cc
@@ -0,0 +1,82 @@
+// 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 <cstdlib>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/direct_mmap.h"
+
+#ifndef _WIN32
+#include <unistd.h>
+#endif
+
+#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)
+#include <sys/mman.h>
+#elif defined(_WIN32)
+#include <windows.h>
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace base_internal {
+
+namespace {
+
+size_t GetPageSize() {
+#ifdef _WIN32
+  SYSTEM_INFO system_info;
+  GetSystemInfo(&system_info);
+  return system_info.dwPageSize;
+#elif defined(__wasm__) || defined(__asmjs__) || defined(__hexagon__)
+  return getpagesize();
+#else
+  return static_cast<size_t>(sysconf(_SC_PAGESIZE));
+#endif
+}
+
+}  // namespace
+
+void* InitializePoisonedPointerInternal() {
+  const size_t block_size = GetPageSize();
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER)
+  void* data = malloc(block_size);
+  ASAN_POISON_MEMORY_REGION(data, block_size);
+#elif defined(ABSL_HAVE_MEMORY_SANITIZER)
+  void* data = malloc(block_size);
+  __msan_poison(data, block_size);
+#elif defined(ABSL_HAVE_MMAP)
+  void* data = DirectMmap(nullptr, block_size, PROT_NONE,
+                          MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  if (data == MAP_FAILED) return GetBadPointerInternal();
+#elif defined(_WIN32)
+  void* data = VirtualAlloc(nullptr, block_size, MEM_RESERVE | MEM_COMMIT,
+                            PAGE_NOACCESS);
+  if (data == nullptr) return GetBadPointerInternal();
+#else
+  return GetBadPointerInternal();
+#endif
+  // Return the middle of the block so that dereferences before and after the
+  // pointer will both crash.
+  return static_cast<char*>(data) + block_size / 2;
+}
+
+}  // namespace base_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
-- 
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