LogListener.cpp revision dfc47e86858ea67c72f1df2fdb97094b8e8248f2 
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/socket.h>
18#include <sys/types.h>
19#include <sys/un.h>
20#include <unistd.h>
21
22#include <cutils/sockets.h>
23#include <log/logger.h>
24
25#include "LogListener.h"
26
27LogListener::LogListener(LogBuffer *buf, LogReader *reader)
28        : SocketListener(getLogSocket(), false)
29        , logbuf(buf)
30        , reader(reader)
31{  }
32
33bool LogListener::onDataAvailable(SocketClient *cli) {
34    char buffer[sizeof_log_id_t + sizeof(log_time) + sizeof(char)
35        + LOGGER_ENTRY_MAX_PAYLOAD];
36    struct iovec iov = { buffer, sizeof(buffer) };
37    memset(buffer, 0, sizeof(buffer));
38
39    char control[CMSG_SPACE(sizeof(struct ucred))];
40    struct msghdr hdr = {
41        NULL,
42        0,
43        &iov,
44        1,
45        control,
46        sizeof(control),
47        0,
48    };
49
50    int socket = cli->getSocket();
51
52    ssize_t n = recvmsg(socket, &hdr, 0);
53    if (n <= (ssize_t)(sizeof_log_id_t + sizeof(uint16_t) + sizeof(log_time))) {
54        return false;
55    }
56
57    struct ucred *cred = NULL;
58
59    struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
60    while (cmsg != NULL) {
61        if (cmsg->cmsg_level == SOL_SOCKET
62                && cmsg->cmsg_type  == SCM_CREDENTIALS) {
63            cred = (struct ucred *)CMSG_DATA(cmsg);
64            break;
65        }
66        cmsg = CMSG_NXTHDR(&hdr, cmsg);
67    }
68
69    if (cred == NULL) {
70        return false;
71    }
72
73    if (cred->uid == getuid()) {
74        // ignore log messages we send to ourself.
75        // Such log messages are often generated by libraries we depend on
76        // which use standard Android logging.
77        return false;
78    }
79
80    // First log element is always log_id.
81    log_id_t log_id = (log_id_t) *((typeof_log_id_t *) buffer);
82    if (log_id < 0 || log_id >= LOG_ID_MAX) {
83        return false;
84    }
85    char *msg = ((char *)buffer) + sizeof_log_id_t;
86    n -= sizeof_log_id_t;
87
88    // second element is the thread id of the caller
89    pid_t tid = (pid_t) *((uint16_t *) msg);
90    msg += sizeof(uint16_t);
91    n -= sizeof(uint16_t);
92
93    // third element is the realtime at point of caller
94    log_time realtime(msg);
95    msg += sizeof(log_time);
96    n -= sizeof(log_time);
97
98    // NB: hdr.msg_flags & MSG_TRUNC is not tested, silently passing a
99    // truncated message to the logs.
100    unsigned short len = n; // cap to internal maximum
101    if (len == n) {
102        logbuf->log(log_id, realtime, cred->uid, cred->pid, tid, msg, len);
103        reader->notifyNewLog();
104    }
105
106    return true;
107}
108
109int LogListener::getLogSocket() {
110    static const char socketName[] = "logdw";
111    int sock = android_get_control_socket(socketName);
112
113    if (sock < 0) {
114        sock = socket_local_server(socketName,
115                                   ANDROID_SOCKET_NAMESPACE_RESERVED,
116                                   SOCK_DGRAM);
117    }
118
119    int on = 1;
120    if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
121        return -1;
122    }
123    return sock;
124}
125