[PATCH] D73896: [GWP-ASan] Allow late initialisation if single-threaded.

[Mitch Phillips via Phabricator via llvm-commits]

hctim created this revision.
hctim added a reviewer: eugenis.
Herald added subscribers: llvm-commits, Sanitizers, mgorny.
Herald added projects: Sanitizers, LLVM.

This patch allows for late initialisation of the GWP-ASan allocator. Previously, if late initialisation occurred, the sample counter was never updated, meaning we would end up having to wait for 2^32 allocations before getting a sampled allocation.

Now, we initialise the sampling mechanism in init() as well. We require init() to be called single-threaded, so this isn't a problem.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D73896

Files:
  compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp
  compiler-rt/lib/gwp_asan/tests/CMakeLists.txt
  compiler-rt/lib/gwp_asan/tests/late_init.cpp


Index: compiler-rt/lib/gwp_asan/tests/late_init.cpp
===================================================================
--- /dev/null
+++ compiler-rt/lib/gwp_asan/tests/late_init.cpp
@@ -0,0 +1,25 @@
+//===-- late_init.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/guarded_pool_allocator.h"
+#include "gwp_asan/options.h"
+#include "gtest/gtest.h"
+
+TEST(LateInit, CheckLateInitIsOK) {
+  gwp_asan::GuardedPoolAllocator GPA;
+
+  for (size_t i = 0; i < 0x100; ++i)
+    EXPECT_FALSE(GPA.shouldSample());
+
+  gwp_asan::options::Options Opts;
+  Opts.Enabled = true;
+  Opts.SampleRate = 1;
+
+  GPA.init(Opts);
+  EXPECT_TRUE(GPA.shouldSample());
+}
Index: compiler-rt/lib/gwp_asan/tests/CMakeLists.txt
===================================================================
--- compiler-rt/lib/gwp_asan/tests/CMakeLists.txt
+++ compiler-rt/lib/gwp_asan/tests/CMakeLists.txt
@@ -20,7 +20,8 @@
   slot_reuse.cpp
   thread_contention.cpp
   harness.cpp
-  enable_disable.cpp)
+  enable_disable.cpp
+  late_init.cpp)
 
 set(GWP_ASAN_UNIT_TEST_HEADERS
   ${GWP_ASAN_HEADERS}
Index: compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp
===================================================================
--- compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp
+++ compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp
@@ -164,6 +164,9 @@
   else
     AdjustedSampleRatePlusOne = 2;
 
+  ThreadLocals.NextSampleCounter =
+      (getRandomUnsigned32() % (AdjustedSampleRatePlusOne - 1)) + 1;
+
   GuardedPagePool = reinterpret_cast<uintptr_t>(GuardedPoolMemory);
   GuardedPagePoolEnd =
       reinterpret_cast<uintptr_t>(GuardedPoolMemory) + PoolBytesRequired;


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