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      1 // Copyright 2015 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include <stdint.h>
      6 
      7 #include "base/logging.h"
      8 #include "base/process/process_handle.h"
      9 #include "build/build_config.h"
     10 
     11 namespace base {
     12 
     13 namespace {
     14 bool g_have_unique_id = false;
     15 uint32_t g_unique_id;
     16 
     17 // The process which set |g_unique_id|.
     18 ProcessId g_procid;
     19 
     20 // Mangle IDs so that they are not accidentally used as PIDs, e.g. as an
     21 // argument to kill or waitpid.
     22 uint32_t MangleProcessId(ProcessId process_id) {
     23   // Add a large power of 10 so that the pid is still the pid is still readable
     24   // inside the mangled id.
     25   return static_cast<uint32_t>(process_id) + 1000000000U;
     26 }
     27 
     28 }  // namespace
     29 
     30 uint32_t GetUniqueIdForProcess() {
     31   if (!g_have_unique_id) {
     32     return MangleProcessId(GetCurrentProcId());
     33   }
     34 
     35   // Make sure we are the same process that set |g_procid|. This check may have
     36   // false negatives (if a process ID was reused) but should have no false
     37   // positives.
     38   DCHECK_EQ(GetCurrentProcId(), g_procid);
     39   return g_unique_id;
     40 }
     41 
     42 #if defined(OS_LINUX)
     43 
     44 void InitUniqueIdForProcessInPidNamespace(ProcessId pid_outside_of_namespace) {
     45   g_unique_id = MangleProcessId(pid_outside_of_namespace);
     46   g_procid = GetCurrentProcId();
     47   g_have_unique_id = true;
     48 }
     49 
     50 #endif
     51 
     52 }  // namespace base
     53