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      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 
     27 #include "LogListener.h"
     28 
     29 LogListener::LogListener(LogBuffer *buf, LogReader *reader)
     30         : SocketListener(getLogSocket(), false)
     31         , logbuf(buf)
     32         , reader(reader)
     33 {  }
     34 
     35 bool LogListener::onDataAvailable(SocketClient *cli) {
     36     prctl(PR_SET_NAME, "logd.writer");
     37 
     38     char buffer[sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time)
     39         + LOGGER_ENTRY_MAX_PAYLOAD];
     40     struct iovec iov = { buffer, sizeof(buffer) };
     41     memset(buffer, 0, sizeof(buffer));
     42 
     43     char control[CMSG_SPACE(sizeof(struct ucred))];
     44     struct msghdr hdr = {
     45         NULL,
     46         0,
     47         &iov,
     48         1,
     49         control,
     50         sizeof(control),
     51         0,
     52     };
     53 
     54     int socket = cli->getSocket();
     55 
     56     ssize_t n = recvmsg(socket, &hdr, 0);
     57     if (n <= (ssize_t)(sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time))) {
     58         return false;
     59     }
     60 
     61     struct ucred *cred = NULL;
     62 
     63     struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
     64     while (cmsg != NULL) {
     65         if (cmsg->cmsg_level == SOL_SOCKET
     66                 && cmsg->cmsg_type  == SCM_CREDENTIALS) {
     67             cred = (struct ucred *)CMSG_DATA(cmsg);
     68             break;
     69         }
     70         cmsg = CMSG_NXTHDR(&hdr, cmsg);
     71     }
     72 
     73     if (cred == NULL) {
     74         return false;
     75     }
     76 
     77     if (cred->uid == getuid()) {
     78         // ignore log messages we send to ourself.
     79         // Such log messages are often generated by libraries we depend on
     80         // which use standard Android logging.
     81         return false;
     82     }
     83 
     84     // First log element is always log_id.
     85     log_id_t log_id = (log_id_t) *((typeof_log_id_t *) buffer);
     86     if (log_id < 0 || log_id >= LOG_ID_MAX) {
     87         return false;
     88     }
     89     char *msg = ((char *)buffer) + sizeof_log_id_t;
     90     n -= sizeof_log_id_t;
     91 
     92     // second element is the thread id of the caller
     93     pid_t tid = (pid_t) *((uint16_t *) msg);
     94     msg += sizeof(uint16_t);
     95     n -= sizeof(uint16_t);
     96 
     97     // third element is the realtime at point of caller
     98     log_time realtime(msg);
     99     msg += sizeof(log_time);
    100     n -= sizeof(log_time);
    101 
    102     // NB: hdr.msg_flags & MSG_TRUNC is not tested, silently passing a
    103     // truncated message to the logs.
    104 
    105     logbuf->log(log_id, realtime, cred->uid, cred->pid, tid, msg,
    106         ((size_t) n <= USHRT_MAX) ? (unsigned short) n : USHRT_MAX);
    107     reader->notifyNewLog();
    108 
    109     return true;
    110 }
    111 
    112 int LogListener::getLogSocket() {
    113     static const char socketName[] = "logdw";
    114     int sock = android_get_control_socket(socketName);
    115 
    116     if (sock < 0) {
    117         sock = socket_local_server(socketName,
    118                                    ANDROID_SOCKET_NAMESPACE_RESERVED,
    119                                    SOCK_DGRAM);
    120     }
    121 
    122     int on = 1;
    123     if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
    124         return -1;
    125     }
    126     return sock;
    127 }
    128