rotate_logs.cpp

/*
 * Copyright (C) 2016 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.
 */

#include "rotate_logs.h"

#include <stdio.h>
#include <string.h>
#include <sys/types.h>

#include <string>

#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/parseint.h>
#include <android-base/stringprintf.h>
#include <private/android_logger.h> /* private pmsg functions */

static const std::string LAST_KMSG_FILTER = "recovery/last_kmsg";
static const std::string LAST_LOG_FILTER = "recovery/last_log";

ssize_t logbasename(log_id_t /* id */, char /* prio */, const char* filename, const char* /* buf */,
                    size_t len, void* arg) {
  bool* do_rotate = static_cast<bool*>(arg);
  if (LAST_KMSG_FILTER.find(filename) != std::string::npos ||
      LAST_LOG_FILTER.find(filename) != std::string::npos) {
    *do_rotate = true;
  }
  return len;
}

ssize_t logrotate(log_id_t id, char prio, const char* filename, const char* buf, size_t len,
                  void* arg) {
  bool* do_rotate = static_cast<bool*>(arg);
  if (!*do_rotate) {
    return __android_log_pmsg_file_write(id, prio, filename, buf, len);
  }

  std::string name(filename);
  size_t dot = name.find_last_of('.');
  std::string sub = name.substr(0, dot);

  if (LAST_KMSG_FILTER.find(sub) == std::string::npos &&
      LAST_LOG_FILTER.find(sub) == std::string::npos) {
    return __android_log_pmsg_file_write(id, prio, filename, buf, len);
  }

  // filename rotation
  if (dot == std::string::npos) {
    name += ".1";
  } else {
    std::string number = name.substr(dot + 1);
    if (!isdigit(number[0])) {
      name += ".1";
    } else {
      size_t i;
      if (!android::base::ParseUint(number, &i)) {
        LOG(ERROR) << "failed to parse uint in " << number;
        return -1;
      }
      name = sub + "." + std::to_string(i + 1);
    }
  }

  return __android_log_pmsg_file_write(id, prio, name.c_str(), buf, len);
}

// Rename last_log -> last_log.1 -> last_log.2 -> ... -> last_log.$max.
// Similarly rename last_kmsg -> last_kmsg.1 -> ... -> last_kmsg.$max.
// Overwrite any existing last_log.$max and last_kmsg.$max.
void rotate_logs(const char* last_log_file, const char* last_kmsg_file) {
  // Logs should only be rotated once.
  static bool rotated = false;
  if (rotated) {
    return;
  }
  rotated = true;

  for (int i = KEEP_LOG_COUNT - 1; i >= 0; --i) {
    std::string old_log = android::base::StringPrintf("%s", last_log_file);
    if (i > 0) {
      old_log += "." + std::to_string(i);
    }
    std::string new_log = android::base::StringPrintf("%s.%d", last_log_file, i + 1);
    // Ignore errors if old_log doesn't exist.
    rename(old_log.c_str(), new_log.c_str());

    std::string old_kmsg = android::base::StringPrintf("%s", last_kmsg_file);
    if (i > 0) {
      old_kmsg += "." + std::to_string(i);
    }
    std::string new_kmsg = android::base::StringPrintf("%s.%d", last_kmsg_file, i + 1);
    rename(old_kmsg.c_str(), new_kmsg.c_str());
  }
}