LogListener.cpp revision ae4d928d816e30dbe57c2c321b0f0759d0567b3f 
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
31LogListener::LogListener(LogBuffer *buf, LogReader *reader)
32        : SocketListener(getLogSocket(), false)
33        , logbuf(buf)
34        , reader(reader)
35{  }
36
37bool 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
110int 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