macOS: Partition alloc should use memory tag 254.

base/allocator/partition_allocator/page_allocator.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/allocator/partition_allocator/page_allocator.h"
 
 #include <limits.h>
 
 #include <atomic>
 
 #include "base/allocator/partition_allocator/address_space_randomization.h"
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "build/build_config.h"
 
+#if defined(OS_MACOSX)
+#include <mach/mach.h>
+#endif
+
 #if defined(OS_POSIX)
 
 #include <errno.h>
 #include <sys/mman.h>
 
 #ifndef MADV_FREE
 #define MADV_FREE MADV_DONTNEED
 #endif
 
 #ifndef MAP_ANONYMOUS
@@ skipping 28 matching lines @@
   DCHECK(!(reinterpret_cast<uintptr_t>(hint) &
            kPageAllocationGranularityOffsetMask));
   void* ret;
 #if defined(OS_WIN)
   DWORD access_flag =
       page_accessibility == PageAccessible ? PAGE_READWRITE : PAGE_NOACCESS;
   ret = VirtualAlloc(hint, length, MEM_RESERVE | MEM_COMMIT, access_flag);
   if (!ret)
     s_allocPageErrorCode = GetLastError();
 #else
+
+#if defined(OS_MACOSX)
+  // Use a custom tag to make it easier to distinguish partition alloc regions
+  // in vmmap.
+  int fd = VM_MAKE_TAG(254);
+#else
+  int fd = -1;
+#endif
+
   int access_flag = page_accessibility == PageAccessible
                         ? (PROT_READ | PROT_WRITE)
                         : PROT_NONE;
-  ret = mmap(hint, length, access_flag, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  ret = mmap(hint, length, access_flag, MAP_ANONYMOUS | MAP_PRIVATE, fd, 0);
   if (ret == MAP_FAILED) {
     s_allocPageErrorCode = errno;
     ret = 0;
   }
 #endif
   return ret;
 }
 
 // Trims base to given length and alignment. Windows returns null on failure and
 // frees base.
@@ skipping 199 matching lines @@
     CHECK(ret);
   }
 #endif
 }
 
 uint32_t GetAllocPageErrorCode() {
   return s_allocPageErrorCode;
 }
 
 }  // namespace base