commit a8fa4b1487b0ee8fc645d2e5b9c2c318d8c87e07
author Kostya Kortchinsky <kostyak@google.com> Fri Aug 28 11:44:39 2020 -0700
committer Copybara-Service <copybara-worker@google.com> Wed Sep 16 17:09:18 2020 -0700
tree 99c657932a2660994ba63f249db1f7db0680b530
parent 996049d45c81f55a4bf4e98cb741621d8876a586

[scudo][standalone] Enable secondary cache release on Fuchsia

I had left this as a TODO, but it turns out it wasn't complicated.
By specifying `MAP_RESIZABLE`, it allows us to keep the VMO which we
can then use for release purposes.
`releasePagesToOS` also had to be called the "proper" way, as Fuchsia
requires the `Offset` field to be correct. This has no impact on
non-Fuchsia platforms.

Differential Revision: https://reviews.llvm.org/D86800

GitOrigin-RevId: 00d9907a7ac86c3aa49c8cbb21a97094b5887ea9

combined.h

diff --git a/combined.h b/combined.h
index 6ca00c2..465e581 100644
--- a/combined.h
+++ b/combined.h
@@ -306,7 +306,7 @@
 
     void *Block = nullptr;
     uptr ClassId = 0;
-    uptr SecondaryBlockEnd;
+    uptr SecondaryBlockEnd = 0;
     if (LIKELY(PrimaryT::canAllocate(NeededSize))) {
       ClassId = SizeClassMap::getClassIdBySize(NeededSize);
       DCHECK_NE(ClassId, 0U);

secondary.h

diff --git a/secondary.h b/secondary.h
index b5bb53d..da435fd 100644
--- a/secondary.h
+++ b/secondary.h
@@ -75,11 +75,6 @@
           s32 MaxReleaseToOsIntervalMs = INT32_MAX>
 class MapAllocatorCache {
 public:
-  // Fuchsia doesn't allow releasing Secondary blocks yet. Note that 0 length
-  // arrays are an extension for some compilers.
-  // FIXME(kostyak): support (partially) the cache on Fuchsia.
-  static_assert(!SCUDO_FUCHSIA || EntriesArraySize == 0U, "");
-
   // Ensure the default maximum specified fits the array.
   static_assert(DefaultMaxEntriesCount <= EntriesArraySize, "");
 
@@ -392,9 +387,9 @@
   }
 
   const uptr CommitSize = MapEnd - PageSize - CommitBase;
-  const uptr Ptr =
-      reinterpret_cast<uptr>(map(reinterpret_cast<void *>(CommitBase),
-                                 CommitSize, "scudo:secondary", 0, &Data));
+  const uptr Ptr = reinterpret_cast<uptr>(
+      map(reinterpret_cast<void *>(CommitBase), CommitSize, "scudo:secondary",
+          MAP_RESIZABLE, &Data));
   LargeBlock::Header *H = reinterpret_cast<LargeBlock::Header *>(Ptr);
   H->MapBase = MapBase;
   H->MapSize = MapEnd - MapBase;

tests/combined_test.cpp

diff --git a/tests/combined_test.cpp b/tests/combined_test.cpp
index 9689c42..4811583 100644
--- a/tests/combined_test.cpp
+++ b/tests/combined_test.cpp
@@ -14,6 +14,7 @@
 #include <condition_variable>
 #include <memory>
 #include <mutex>
+#include <set>
 #include <thread>
 #include <vector>
 
@@ -23,7 +24,8 @@
 
 static constexpr scudo::Chunk::Origin Origin = scudo::Chunk::Origin::Malloc;
 
-static void disableDebuggerdMaybe() {
+// Fuchsia complains that the function is not used.
+UNUSED static void disableDebuggerdMaybe() {
 #if SCUDO_ANDROID
   // Disable the debuggerd signal handler on Android, without this we can end
   // up spending a significant amount of time creating tombstones.

tests/secondary_test.cpp

diff --git a/tests/secondary_test.cpp b/tests/secondary_test.cpp
index 29efdb3..d9f2d2f 100644
--- a/tests/secondary_test.cpp
+++ b/tests/secondary_test.cpp
@@ -56,18 +56,12 @@
 
 TEST(ScudoSecondaryTest, SecondaryBasic) {
   testSecondaryBasic<scudo::MapAllocator<scudo::MapAllocatorNoCache>>();
-#if !SCUDO_FUCHSIA
   testSecondaryBasic<scudo::MapAllocator<scudo::MapAllocatorCache<>>>();
   testSecondaryBasic<
       scudo::MapAllocator<scudo::MapAllocatorCache<128U, 64U, 1UL << 20>>>();
-#endif
 }
 
-#if SCUDO_FUCHSIA
-using LargeAllocator = scudo::MapAllocator<scudo::MapAllocatorNoCache>;
-#else
 using LargeAllocator = scudo::MapAllocator<scudo::MapAllocatorCache<>>;
-#endif
 
 // This exercises a variety of combinations of size and alignment for the
 // MapAllocator. The size computation done here mimic the ones done by the