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1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef SRC_FTRACE_READER_FTRACE_PROCFS_H_
18 #define SRC_FTRACE_READER_FTRACE_PROCFS_H_
19 
20 #include <memory>
21 #include <set>
22 #include <string>
23 
24 #include "perfetto/base/scoped_file.h"
25 
26 namespace perfetto {
27 
28 class FtraceProcfs {
29  public:
30   static std::unique_ptr<FtraceProcfs> Create(const std::string& root);
31   static int g_kmesg_fd;
32 
33   explicit FtraceProcfs(const std::string& root);
34   virtual ~FtraceProcfs();
35 
36   // Enable the event under with the given |group| and |name|.
37   bool EnableEvent(const std::string& group, const std::string& name);
38 
39   // Disable the event under with the given |group| and |name|.
40   bool DisableEvent(const std::string& group, const std::string& name);
41 
42   // Disable all events by writing to the global enable file.
43   bool DisableAllEvents();
44 
45   // Read the format for event with the given |group| and |name|.
46   // virtual for testing.
47   virtual std::string ReadEventFormat(const std::string& group,
48                                       const std::string& name) const;
49 
50   // Read the "/per_cpu/cpuXX/stats" file for the given |cpu|.
51   std::string ReadCpuStats(size_t cpu) const;
52 
53   // Set ftrace buffer size in pages.
54   // This size is *per cpu* so for the total size you have to multiply
55   // by the number of CPUs.
56   bool SetCpuBufferSizeInPages(size_t pages);
57 
58   // Returns the number of CPUs.
59   // This will match the number of tracing/per_cpu/cpuXX directories.
60   size_t virtual NumberOfCpus() const;
61 
62   // Clears the trace buffers for all CPUs. Blocks until this is done.
63   void ClearTrace();
64 
65   // Writes the string |str| as an event into the trace buffer.
66   bool WriteTraceMarker(const std::string& str);
67 
68   // Enable tracing.
69   bool EnableTracing();
70 
71   // Disables tracing, does not clear the buffer.
72   bool DisableTracing();
73 
74   // Enabls/disables tracing, does not clear the buffer.
75   bool SetTracingOn(bool enable);
76 
77   // Returns true iff tracing is enabled.
78   // Necessarily racy: another program could enable/disable tracing at any
79   // point.
80   bool IsTracingEnabled();
81 
82   // Set the clock. |clock_name| should be one of the names returned by
83   // AvailableClocks. Setting the clock clears the buffer.
84   bool SetClock(const std::string& clock_name);
85 
86   // Get the currently set clock.
87   std::string GetClock();
88 
89   // Get all the avaiable clocks.
90   std::set<std::string> AvailableClocks();
91 
92   // Open the raw pipe for |cpu|.
93   virtual base::ScopedFile OpenPipeForCpu(size_t cpu);
94 
95  protected:
96   // virtual and public for testing.
97   virtual bool WriteToFile(const std::string& path, const std::string& str);
98   virtual bool ClearFile(const std::string& path);
99   virtual char ReadOneCharFromFile(const std::string& path);
100   virtual std::string ReadFileIntoString(const std::string& path) const;
101 
102  private:
103   // Checks the trace file is present at the given root path.
104   static bool CheckRootPath(const std::string& root);
105 
106   bool WriteNumberToFile(const std::string& path, size_t value);
107 
108   const std::string root_;
109 };
110 
111 }  // namespace perfetto
112 
113 #endif  // SRC_FTRACE_READER_FTRACE_PROCFS_H_
114