Home | History | Annotate | Download | only in logd 
      1 /*
      2  * Copyright (C) 2012-2014 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 #include <limits.h>
     18 #include <sys/prctl.h>
     19 #include <sys/socket.h>
     20 #include <sys/types.h>
     21 #include <sys/un.h>
     22 #include <unistd.h>
     23 
     24 #include <cutils/sockets.h>
     25 #include <log/logger.h>
     26 #include <private/android_filesystem_config.h>
     27 #include <private/android_logger.h>
     28 
     29 #include "LogListener.h"
     30 
     31 LogListener::LogListener(LogBuffer *buf, LogReader *reader) :
     32         SocketListener(getLogSocket(), false),
     33         logbuf(buf),
     34         reader(reader) {
     35 }
     36 
     37 bool LogListener::onDataAvailable(SocketClient *cli) {
     38     static bool name_set;
     39     if (!name_set) {
     40         prctl(PR_SET_NAME, "logd.writer");
     41         name_set = true;
     42     }
     43 
     44     char buffer[sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time)
     45         + LOGGER_ENTRY_MAX_PAYLOAD];
     46     struct iovec iov = { buffer, sizeof(buffer) };
     47     memset(buffer, 0, sizeof(buffer));
     48 
     49     char control[CMSG_SPACE(sizeof(struct ucred))];
     50     struct msghdr hdr = {
     51         NULL,
     52         0,
     53         &iov,
     54         1,
     55         control,
     56         sizeof(control),
     57         0,
     58     };
     59 
     60     int socket = cli->getSocket();
     61 
     62     ssize_t n = recvmsg(socket, &hdr, 0);
     63     if (n <= (ssize_t)(sizeof(android_log_header_t))) {
     64         return false;
     65     }
     66 
     67     struct ucred *cred = NULL;
     68 
     69     struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
     70     while (cmsg != NULL) {
     71         if (cmsg->cmsg_level == SOL_SOCKET
     72                 && cmsg->cmsg_type  == SCM_CREDENTIALS) {
     73             cred = (struct ucred *)CMSG_DATA(cmsg);
     74             break;
     75         }
     76         cmsg = CMSG_NXTHDR(&hdr, cmsg);
     77     }
     78 
     79     if (cred == NULL) {
     80         return false;
     81     }
     82 
     83     if (cred->uid == AID_LOGD) {
     84         // ignore log messages we send to ourself.
     85         // Such log messages are often generated by libraries we depend on
     86         // which use standard Android logging.
     87         return false;
     88     }
     89 
     90     android_log_header_t *header = reinterpret_cast<android_log_header_t *>(buffer);
     91     if (/* header->id < LOG_ID_MIN || */ header->id >= LOG_ID_MAX || header->id == LOG_ID_KERNEL) {
     92         return false;
     93     }
     94 
     95     char *msg = ((char *)buffer) + sizeof(android_log_header_t);
     96     n -= sizeof(android_log_header_t);
     97 
     98     // NB: hdr.msg_flags & MSG_TRUNC is not tested, silently passing a
     99     // truncated message to the logs.
    100 
    101     if (logbuf->log((log_id_t)header->id, header->realtime,
    102             cred->uid, cred->pid, header->tid, msg,
    103             ((size_t) n <= USHRT_MAX) ? (unsigned short) n : USHRT_MAX) >= 0) {
    104         reader->notifyNewLog();
    105     }
    106 
    107     return true;
    108 }
    109 
    110 int LogListener::getLogSocket() {
    111     static const char socketName[] = "logdw";
    112     int sock = android_get_control_socket(socketName);
    113 
    114     if (sock < 0) {
    115         sock = socket_local_server(socketName,
    116                                    ANDROID_SOCKET_NAMESPACE_RESERVED,
    117                                    SOCK_DGRAM);
    118     }
    119 
    120     int on = 1;
    121     if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
    122         return -1;
    123     }
    124     return sock;
    125 }
    126