1 files changed, 29 insertions, 5 deletions
diff --git a/runtime/mem_map.cc b/runtime/mem_map.cc
index bb07fcbf37..1ec59b3cc7 100644
--- a/runtime/mem_map.cc
+++ b/runtime/mem_map.cc
@@ -318,11 +318,18 @@ MemMap* MemMap::MapAnonymous(const char* name,
     debug_friendly_name += name;
     fd.Reset(ashmem_create_region(debug_friendly_name.c_str(), page_aligned_byte_count),
              /* check_usage */ false);
+
     if (fd.Fd() == -1) {
-      *error_msg = StringPrintf("ashmem_create_region failed for '%s': %s", name, strerror(errno));
-      return nullptr;
+      // We failed to create the ashmem region. Print a warning, but continue
+      // anyway by creating a true anonymous mmap with an fd of -1. It is
+      // better to use an unlabelled anonymous map than to fail to create a
+      // map at all.
+      PLOG(WARNING) << "ashmem_create_region failed for '" << name << "'";
+    } else {
+      // We succeeded in creating the ashmem region. Use the created ashmem
+      // region as backing for the mmap.
+      flags &= ~MAP_ANONYMOUS;
     }
-    flags &= ~MAP_ANONYMOUS;
   }
 
   // We need to store and potentially set an error number for pretty printing of errors
@@ -354,7 +361,6 @@ MemMap* MemMap::MapAnonymous(const char* name,
     }
     return nullptr;
   }
-  std::ostringstream check_map_request_error_msg;
   if (!CheckMapRequest(expected_ptr, actual, page_aligned_byte_count, error_msg)) {
     return nullptr;
   }
@@ -441,7 +447,6 @@ MemMap* MemMap::MapFileAtAddress(uint8_t* expected_ptr,
     }
     return nullptr;
   }
-  std::ostringstream check_map_request_error_msg;
   if (!CheckMapRequest(expected_ptr, actual, page_aligned_byte_count, error_msg)) {
     return nullptr;
   }
@@ -918,4 +923,23 @@ void MemMap::TryReadable() {
   }
 }
 
+void ZeroAndReleasePages(void* address, size_t length) {
+  uint8_t* const mem_begin = reinterpret_cast<uint8_t*>(address);
+  uint8_t* const mem_end = mem_begin + length;
+  uint8_t* const page_begin = AlignUp(mem_begin, kPageSize);
+  uint8_t* const page_end = AlignDown(mem_end, kPageSize);
+  if (!kMadviseZeroes || page_begin >= page_end) {
+    // No possible area to madvise.
+    std::fill(mem_begin, mem_end, 0);
+  } else {
+    // Spans one or more pages.
+    DCHECK_LE(mem_begin, page_begin);
+    DCHECK_LE(page_begin, page_end);
+    DCHECK_LE(page_end, mem_end);
+    std::fill(mem_begin, page_begin, 0);
+    CHECK_NE(madvise(page_begin, page_end - page_begin, MADV_DONTNEED), -1) << "madvise failed";
+    std::fill(page_end, mem_end, 0);
+  }
+}
+
 }  // namespace art