Start adding the supporting code to perform out-of-process allocator

enumeration.

Summary:

This patch introduces the local portion (`LocalAddressSpaceView`) of the
`AddressSpaceView` abstraction and modifies the secondary allocator
so that the `ForEachChunk()` method (and its callees) would work in the
out-of-process case when `AddressSpaceView` is `RemoteAddressSpaceView`.

The `AddressSpaceView` abstraction simply maps pointers from a target
process to a pointer in the local process (via its `Load()` method). For
the local (in-process) case this is a no-op. For the remote
(out-of-process) case this is not a no-op. The implementation of the
out-of-process `RemoteAddressSpaceView` is not included in this patch
and will be introduced later.

This patch is considerably simpler than the `ObjectView` abstraction
used in previous patches but lacks the type safety and stricter memory
management of the `ObjectView` abstraction.

This patch does not introduce any tests because with
`LocalAddressSpaceView` it should be a non functional change and unit
tests already cover the secondary allocator.  When
`RemoteAddressSpaceView` is landed tests will be added to ensure that it
functions as expected.

rdar://problem/45284065

Reviewers: kcc, kubamracek, dvyukov, vitalybuka, cryptoad,
george.karpenkov, morehouse

Subscribers: #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D53975

llvm-svn: 346956

compiler-rt/lib/sanitizer_common/CMakeLists.txt

@@ -144,6 +144,7 @@ set(SANITIZER_IMPL_HEADERS
   sanitizer_libignore.h
   sanitizer_linux.h
   sanitizer_list.h
+  sanitizer_local_address_space_view.h
   sanitizer_mac.h
   sanitizer_malloc_mac.inc
   sanitizer_mutex.h

compiler-rt/lib/sanitizer_common/sanitizer_allocator.h

@@ -14,12 +14,13 @@
 #ifndef SANITIZER_ALLOCATOR_H
 #define SANITIZER_ALLOCATOR_H
 
-#include "sanitizer_internal_defs.h"
 #include "sanitizer_common.h"
+#include "sanitizer_internal_defs.h"
+#include "sanitizer_lfstack.h"
 #include "sanitizer_libc.h"
 #include "sanitizer_list.h"
+#include "sanitizer_local_address_space_view.h"
 #include "sanitizer_mutex.h"
-#include "sanitizer_lfstack.h"
 #include "sanitizer_procmaps.h"
 
 namespace __sanitizer {

compiler-rt/lib/sanitizer_common/sanitizer_allocator_secondary.h

@@ -68,7 +68,8 @@ typedef LargeMmapAllocatorPtrArrayDynamic DefaultLargeMmapAllocatorPtrArray;
 // The main purpose of this allocator is to cover large and rare allocation
 // sizes not covered by more efficient allocators (e.g. SizeClassAllocator64).
 template <class MapUnmapCallback = NoOpMapUnmapCallback,
-          class PtrArrayT = DefaultLargeMmapAllocatorPtrArray>
+          class PtrArrayT = DefaultLargeMmapAllocatorPtrArray,
+          class AddressSpaceView = LocalAddressSpaceView>
 class LargeMmapAllocator {
  public:
   void InitLinkerInitialized() {
@@ -202,9 +203,10 @@ class LargeMmapAllocator {
 
   void EnsureSortedChunks() {
     if (chunks_sorted_) return;
-    Sort(reinterpret_cast<uptr *>(chunks_), n_chunks_);
+    Header **chunks = AddressSpaceView::Load(chunks_, n_chunks_);
+    Sort(reinterpret_cast<uptr *>(chunks), n_chunks_);
     for (uptr i = 0; i < n_chunks_; i++)
-      chunks_[i]->chunk_idx = i;
+      AddressSpaceView::Load(chunks[i])->chunk_idx = i;
     chunks_sorted_ = true;
   }
 
@@ -272,12 +274,13 @@ class LargeMmapAllocator {
   // The allocator must be locked when calling this function.
   void ForEachChunk(ForEachChunkCallback callback, void *arg) {
     EnsureSortedChunks();  // Avoid doing the sort while iterating.
+    Header **chunks = AddressSpaceView::Load(chunks_, n_chunks_);
     for (uptr i = 0; i < n_chunks_; i++) {
-      auto t = chunks_[i];
+      Header *t = chunks[i];
       callback(reinterpret_cast<uptr>(GetUser(t)), arg);
       // Consistency check: verify that the array did not change.
-      CHECK_EQ(chunks_[i], t);
-      CHECK_EQ(chunks_[i]->chunk_idx, i);
+      CHECK_EQ(chunks[i], t);
+      CHECK_EQ(AddressSpaceView::Load(chunks[i])->chunk_idx, i);
     }
   }
 
@@ -316,4 +319,3 @@ class LargeMmapAllocator {
   } stats;
   StaticSpinMutex mutex_;
 };
-

compiler-rt/lib/sanitizer_common/sanitizer_local_address_space_view.h

@@ -0,0 +1,53 @@
+//===-- sanitizer_local_address_space_view.h --------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// `LocalAddressSpaceView` provides the local (i.e. target and current address
+// space are the same) implementation of the `AddressSpaveView` interface which
+// provides a simple interface to load memory from another process (i.e.
+// out-of-process)
+//
+// The `AddressSpaveView` interface requires that the type can be used as a
+// template parameter to objects that wish to be able to operate in an
+// out-of-process manner. In normal usage, objects are in-process and are thus
+// instantiated with the `LocalAddressSpaceView` type. This type is used to
+// load any pointers in instance methods. This implementation is effectively
+// a no-op. When an object is to be used in an out-of-process manner it is
+// instansiated with the `RemoteAddressSpaceView` type.
+//
+// By making `AddressSpaceView` a template parameter of an object, it can
+// change its implementation at compile time which has no run time overhead.
+// This also allows unifying in-process and out-of-process code which avoids
+// code duplication.
+//
+//===----------------------------------------------------------------------===//
+#ifndef SANITIZER_LOCAL_ADDRES_SPACE_VIEW_H
+#define SANITIZER_LOCAL_ADDRES_SPACE_VIEW_H
+
+namespace __sanitizer {
+struct LocalAddressSpaceView {
+  // Load memory `sizeof(T) * num_elements` bytes of memory
+  // from the target process (always local for this implementation)
+  // starting at address `target_address`. The local copy of
+  // this memory is returned as a pointer. It is guaranteed that
+  //
+  // * That the function will always return the same value
+  //   for a given set of arguments.
+  // * That the memory returned is writable and that writes will persist.
+  //
+  // The lifetime of loaded memory is implementation defined.
+  template <typename T>
+  static T *Load(T *target_address, uptr num_elements = 1) {
+    // The target address space is the local address space so
+    // nothing needs to be copied. Just return the pointer.
+    return target_address;
+  }
+};
+}  // namespace __sanitizer
+
+#endif