1 /*
2  * Copyright (C) 2020 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 #pragma once
18 
19 #include <atomic>
20 #include <list>
21 #include <mutex>
22 
23 #include "LogBuffer.h"
24 #include "LogBufferElement.h"
25 #include "LogReaderList.h"
26 #include "LogStatistics.h"
27 #include "LogTags.h"
28 #include "LogdLock.h"
29 
30 class SimpleLogBuffer : public LogBuffer {
31   public:
32     SimpleLogBuffer(LogReaderList* reader_list, LogTags* tags, LogStatistics* stats);
33     ~SimpleLogBuffer();
34     void Init() override final;
35 
36     int Log(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid, pid_t tid, const char* msg,
37             uint16_t len) override;
38     std::unique_ptr<FlushToState> CreateFlushToState(uint64_t start, LogMask log_mask)
39             REQUIRES(logd_lock) override;
40     bool FlushTo(LogWriter* writer, FlushToState& state,
41                  const std::function<FilterResult(log_id_t log_id, pid_t pid, uint64_t sequence,
42                                                   log_time realtime)>& filter)
43             REQUIRES(logd_lock) override;
44 
45     bool Clear(log_id_t id, uid_t uid) override;
46     size_t GetSize(log_id_t id) override;
47     bool SetSize(log_id_t id, size_t size) override final;
48 
sequence()49     uint64_t sequence() const override { return sequence_.load(std::memory_order_relaxed); }
50 
51   protected:
52     virtual bool Prune(log_id_t id, unsigned long prune_rows, uid_t uid) REQUIRES(logd_lock);
53     virtual void LogInternal(LogBufferElement&& elem) REQUIRES(logd_lock);
54 
55     // Returns an iterator to the oldest element for a given log type, or logs_.end() if
56     // there are no logs for the given log type. Requires logs_logd_lock to be held.
57     std::list<LogBufferElement>::iterator GetOldest(log_id_t log_id) REQUIRES(logd_lock);
58     std::list<LogBufferElement>::iterator Erase(std::list<LogBufferElement>::iterator it)
59             REQUIRES(logd_lock);
60     void KickReader(LogReaderThread* reader, log_id_t id, unsigned long prune_rows)
61             REQUIRES(logd_lock);
62 
stats()63     LogStatistics* stats() { return stats_; }
reader_list()64     LogReaderList* reader_list() { return reader_list_; }
max_size(log_id_t id)65     size_t max_size(log_id_t id) REQUIRES_SHARED(logd_lock) { return max_size_[id]; }
logs()66     std::list<LogBufferElement>& logs() { return logs_; }
67 
68   private:
69     bool ShouldLog(log_id_t log_id, const char* msg, uint16_t len);
70     void MaybePrune(log_id_t id) REQUIRES(logd_lock);
71 
72     LogReaderList* reader_list_;
73     LogTags* tags_;
74     LogStatistics* stats_;
75 
76     std::atomic<uint64_t> sequence_ = 1;
77 
78     size_t max_size_[LOG_ID_MAX] GUARDED_BY(logd_lock);
79     std::list<LogBufferElement> logs_ GUARDED_BY(logd_lock);
80     // Keeps track of the iterator to the oldest log message of a given log type, as an
81     // optimization when pruning logs.  Use GetOldest() to retrieve.
82     std::optional<std::list<LogBufferElement>::iterator> oldest_[LOG_ID_MAX] GUARDED_BY(logd_lock);
83 };
84