platform_system_core/logd/LogBuffer.h

/*
 * Copyright (C) 2012-2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef _LOGD_LOG_BUFFER_H__
#define _LOGD_LOG_BUFFER_H__

#include <sys/types.h>

#include <list>
#include <string>

#include <log/log.h>
#include <sysutils/SocketClient.h>

#include <private/android_filesystem_config.h>

#include "LogBufferElement.h"
#include "LogTimes.h"
#include "LogStatistics.h"
#include "LogWhiteBlackList.h"

//
// We are either in 1970ish (MONOTONIC) or 2016+ish (REALTIME) so to
// differentiate without prejudice, we use 1972 to delineate, earlier
// is likely monotonic, later is real. Otherwise we start using a
// dividing line between monotonic and realtime if more than a minute
// difference between them.
//
namespace android {

static bool isMonotonic(const log_time &mono) {
    static const uint32_t EPOCH_PLUS_2_YEARS = 2 * 24 * 60 * 60 * 1461 / 4;
    static const uint32_t EPOCH_PLUS_MINUTE = 60;

    if (mono.tv_sec >= EPOCH_PLUS_2_YEARS) {
        return false;
    }

    log_time now(CLOCK_REALTIME);

    /* Timezone and ntp time setup? */
    if (now.tv_sec >= EPOCH_PLUS_2_YEARS) {
        return true;
    }

    /* no way to differentiate realtime from monotonic time */
    if (now.tv_sec < EPOCH_PLUS_MINUTE) {
        return false;
    }

    log_time cpu(CLOCK_MONOTONIC);
    /* too close to call to differentiate monotonic times from realtime */
    if ((cpu.tv_sec + EPOCH_PLUS_MINUTE) >= now.tv_sec) {
        return false;
    }

    /* dividing line half way between monotonic and realtime */
    return mono.tv_sec < ((cpu.tv_sec + now.tv_sec) / 2);
}

}

typedef std::list<LogBufferElement *> LogBufferElementCollection;

class LogBuffer {
    LogBufferElementCollection mLogElements;
    pthread_mutex_t mLogElementsLock;

    LogStatistics stats;

    PruneList mPrune;
    // watermark of any worst/chatty uid processing
    typedef std::unordered_map<uid_t,
                               LogBufferElementCollection::iterator>
                LogBufferIteratorMap;
    LogBufferIteratorMap mLastWorstUid[LOG_ID_MAX];
    // watermark of any worst/chatty pid of system processing
    typedef std::unordered_map<pid_t,
                               LogBufferElementCollection::iterator>
                LogBufferPidIteratorMap;
    LogBufferPidIteratorMap mLastWorstPidOfSystem[LOG_ID_MAX];

    unsigned long mMaxSize[LOG_ID_MAX];

    bool monotonic;

public:
    LastLogTimes &mTimes;

    LogBuffer(LastLogTimes *times);
    void init();
    bool isMonotonic() { return monotonic; }

    int log(log_id_t log_id, log_time realtime,
            uid_t uid, pid_t pid, pid_t tid,
            const char *msg, unsigned short len);
    uint64_t flushTo(SocketClient *writer, const uint64_t start,
                     bool privileged,
                     int (*filter)(const LogBufferElement *element, void *arg) = NULL,
                     void *arg = NULL);

    bool clear(log_id_t id, uid_t uid = AID_ROOT);
    unsigned long getSize(log_id_t id);
    int setSize(log_id_t id, unsigned long size);
    unsigned long getSizeUsed(log_id_t id);
    // *strp uses malloc, use free to release.
    std::string formatStatistics(uid_t uid, pid_t pid, unsigned int logMask);

    void enableStatistics() {
        stats.enableStatistics();
    }

    int initPrune(const char *cp) { return mPrune.init(cp); }
    std::string formatPrune() { return mPrune.format(); }

    // helper must be protected directly or implicitly by lock()/unlock()
    const char *pidToName(pid_t pid) { return stats.pidToName(pid); }
    uid_t pidToUid(pid_t pid) { return stats.pidToUid(pid); }
    const char *uidToName(uid_t uid) { return stats.uidToName(uid); }
    void lock() { pthread_mutex_lock(&mLogElementsLock); }
    void unlock() { pthread_mutex_unlock(&mLogElementsLock); }

private:

    static constexpr size_t minPrune = 4;
    static constexpr size_t maxPrune = 256;

    void maybePrune(log_id_t id);
    bool prune(log_id_t id, unsigned long pruneRows, uid_t uid = AID_ROOT);
    LogBufferElementCollection::iterator erase(
        LogBufferElementCollection::iterator it, bool coalesce = false);
};

#endif // _LOGD_LOG_BUFFER_H__