LogListener.cpp revision 8daa9af02dc0e63ce220e3fa95bf5fe4d6b7a99a 
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 <sys/prctl.h>
18#include <sys/socket.h>
19#include <sys/types.h>
20#include <sys/un.h>
21#include <unistd.h>
22
23#include <cutils/sockets.h>
24#include <log/logger.h>
25
26#include "LogListener.h"
27
28LogListener::LogListener(LogBuffer *buf, LogReader *reader)
29        : SocketListener(getLogSocket(), false)
30        , logbuf(buf)
31        , reader(reader)
32{  }
33
34bool LogListener::onDataAvailable(SocketClient *cli) {
35    prctl(PR_SET_NAME, "logd.writer");
36
37    char buffer[sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time)
38        + LOGGER_ENTRY_MAX_PAYLOAD];
39    struct iovec iov = { buffer, sizeof(buffer) };
40    memset(buffer, 0, sizeof(buffer));
41
42    char control[CMSG_SPACE(sizeof(struct ucred))];
43    struct msghdr hdr = {
44        NULL,
45        0,
46        &iov,
47        1,
48        control,
49        sizeof(control),
50        0,
51    };
52
53    int socket = cli->getSocket();
54
55    ssize_t n = recvmsg(socket, &hdr, 0);
56    if (n <= (ssize_t)(sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time))) {
57        return false;
58    }
59
60    struct ucred *cred = NULL;
61
62    struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
63    while (cmsg != NULL) {
64        if (cmsg->cmsg_level == SOL_SOCKET
65                && cmsg->cmsg_type  == SCM_CREDENTIALS) {
66            cred = (struct ucred *)CMSG_DATA(cmsg);
67            break;
68        }
69        cmsg = CMSG_NXTHDR(&hdr, cmsg);
70    }
71
72    if (cred == NULL) {
73        return false;
74    }
75
76    if (cred->uid == getuid()) {
77        // ignore log messages we send to ourself.
78        // Such log messages are often generated by libraries we depend on
79        // which use standard Android logging.
80        return false;
81    }
82
83    // First log element is always log_id.
84    log_id_t log_id = (log_id_t) *((typeof_log_id_t *) buffer);
85    if (log_id < 0 || log_id >= LOG_ID_MAX) {
86        return false;
87    }
88    char *msg = ((char *)buffer) + sizeof_log_id_t;
89    n -= sizeof_log_id_t;
90
91    // second element is the thread id of the caller
92    pid_t tid = (pid_t) *((uint16_t *) msg);
93    msg += sizeof(uint16_t);
94    n -= sizeof(uint16_t);
95
96    // third element is the realtime at point of caller
97    log_time realtime(msg);
98    msg += sizeof(log_time);
99    n -= sizeof(log_time);
100
101    // NB: hdr.msg_flags & MSG_TRUNC is not tested, silently passing a
102    // truncated message to the logs.
103    unsigned short len = n; // cap to internal maximum
104    if (len == n) {
105        logbuf->log(log_id, realtime, cred->uid, cred->pid, tid, msg, len);
106        reader->notifyNewLog();
107    }
108
109    return true;
110}
111
112int 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