fuchsia: allocate vmo/vmar instead of mmap/mprotect to create guarded memory

Fuchsia doesn't (currently? uncertain) support mprotect(...NONE...).
Work around this by using native apis to create a memory block and a
virtual memory mapping, and then leaving a guard page unmapped at the
end of the mapping.

Bug: 706592
Change-Id: I5329cf9206e5aa8056edf0cfb50b8745b9d1c83e
Reviewed-on: https://chromium-review.googlesource.com/545155
Commit-Queue: Scott Graham <scottmg@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#481742}

base/trace_event/heap_profiler_allocation_register_posix.cc

@@ -16,6 +16,11 @@
 #define MAP_ANONYMOUS MAP_ANON
 #endif
 
+#if defined(OS_FUCHSIA)
+#include <magenta/process.h>
+#include <magenta/syscalls.h>
+#endif  // OS_FUCHSIA
+
 namespace base {
 namespace trace_event {
 namespace internal {
@@ -32,25 +37,53 @@ void* AllocateGuardedVirtualMemory(size_t size) {
   // Add space for a guard page at the end.
   size_t map_size = size + GetGuardSize();
 
+#if defined(OS_FUCHSIA)
+  // Fuchsia does not currently support PROT_NONE, see MG-546 upstream. Instead,
+  // create a virtual mapping with the size of the guard page unmapped after the
+  // block.
+  mx_handle_t vmo;
+  CHECK(mx_vmo_create(map_size, 0, &vmo) == MX_OK);
+  mx_handle_t vmar;
+  uintptr_t addr_uint;
+  CHECK(mx_vmar_allocate(mx_vmar_root_self(), 0, map_size,
+                         MX_VM_FLAG_CAN_MAP_READ | MX_VM_FLAG_CAN_MAP_WRITE |
+                             MX_VM_FLAG_CAN_MAP_SPECIFIC,
+                         &vmar, &addr_uint) == MX_OK);
+  CHECK(mx_vmar_map(
+            vmar, 0, vmo, 0, size,
+            MX_VM_FLAG_PERM_READ | MX_VM_FLAG_PERM_WRITE | MX_VM_FLAG_SPECIFIC,
+            &addr_uint) == MX_OK);
+  CHECK(mx_handle_close(vmar) == MX_OK);
+  CHECK(mx_handle_close(vmo) == MX_OK);
+  void* addr = reinterpret_cast<void*>(addr_uint);
+#else
   void* addr = mmap(nullptr, map_size, PROT_READ | PROT_WRITE,
                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-
   PCHECK(addr != MAP_FAILED);
 
   // Mark the last page of the allocated address space as inaccessible
-  // (PROT_NONE). The read/write accessible space is still at least |min_size|
+  // (PROT_NONE). The read/write accessible space is still at least |size|
   // bytes.
   void* guard_addr =
       reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(addr) + size);
   int result = mprotect(guard_addr, GetGuardSize(), PROT_NONE);
   PCHECK(result == 0);
+#endif  // defined(OS_FUCHSIA)
 
   return addr;
 }
 
 void FreeGuardedVirtualMemory(void* address, size_t allocated_size) {
   size_t size = bits::Align(allocated_size, GetPageSize()) + GetGuardSize();
+#if defined(OS_FUCHSIA)
+  mx_status_t status = mx_vmar_unmap(
+      mx_vmar_root_self(), reinterpret_cast<uintptr_t>(address), size);
+  if (status != MX_OK) {
+    DLOG(ERROR) << "mx_vmar_unmap failed, status=" << status;
+  }
+#else
   munmap(address, size);
+#endif
 }
 
 }  // namespace internal

testing/buildbot/filters/fuchsia.base_unittests.filter

@@ -4,14 +4,6 @@
 -ActivityTrackerTest.CreateWithFileTest
 -ActivityTrackerTest.ProcessDeathTest
 -ActivityTrackerTest.ThreadDeathTest
--AllocationRegisterTest.ChangeContextAfterInsertion
--AllocationRegisterTest.DoubleFreeIsAllowed
--AllocationRegisterTest.DoubleInsertOverwrites
--AllocationRegisterTest.InsertRemove
--AllocationRegisterTest.InsertRemoveCollisions
--AllocationRegisterTest.InsertRemoveRandomOrder
--AllocationRegisterTest.OverflowAllocationTest
--AllocationRegisterTest.OverflowBacktraceTest
 -CrashLoggingTest.ChunkValue
 -CrashLoggingTest.InitSize
 -CrashLoggingTest.ScopedCrashKey
@@ -28,9 +20,6 @@
 -DiscardableSharedMemoryTest.MappedSize
 -DiscardableSharedMemoryTest.Purge
 -DiscardableSharedMemoryTest.ZeroSize
--EventWriterTest.HeapDumpAggregation
--EventWriterTest.HeapDumpNoBacktraceNoType
--EventWriterTest.SerializeHeapProfileEventData
 -FeatureListTest.StoreAndRetrieveAssociatedFeaturesFromSharedMemory
 -FeatureListTest.StoreAndRetrieveFeaturesFromSharedMemory
 -FieldTrialListTest.AddTrialsToAllocator
@@ -77,8 +66,6 @@
 -FileUtilTest.ExecutableExistsInPath
 -FileUtilTest.FileToFILE
 -FileUtilTest.NormalizeFilePathSymlinks
--HeapDumpWriterTest.BacktraceIndex
--HeapDumpWriterTest.TypeId
 -LoggingTest.CheckCausesDistinctBreakpoints
 -MemoryMappedFileTest.ExtendableFile
 -MemoryMappedFileTest.MapLargePartialRegionInTheMiddle
@@ -198,7 +185,6 @@
 -TaskSchedulerWorkerPoolImplPostTaskBeforeStartTest.PostTasksBeforeStart
 -TaskSchedulerWorkerPoolStandbyPolicyTest.InitLazy
 -TaskSchedulerWorkerPoolStandbyPolicyTest.InitOne
--TraceEventTestFixture.TestTraceFlush
 -TrackedObjectsTest.ReuseRetiredThreadData
 -TrackedTimeTest.TrackedTimerDuration
 -VerifyPathControlledByUserTest.BadPaths