core/liblog/logd_reader.c

/*
 * Copyright (C) 2007-2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <poll.h>
#include <stdarg.h>
#include <stdatomic.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <time.h>
#include <unistd.h>

#include <cutils/sockets.h>
#include <log/logd.h>
#include <log/logger.h>
#include <log/log_read.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>

#include "config_read.h"
#include "log_portability.h"
#include "logger.h"

/* branchless on many architectures. */
#define min(x,y) ((y) ^ (((x) ^ (y)) & -((x) < (y))))

static int logdAvailable(log_id_t LogId);
static int logdVersion(struct android_log_logger *logger,
                       struct android_log_transport_context *transp);
static int logdRead(struct android_log_logger_list *logger_list,
                    struct android_log_transport_context *transp,
                    struct log_msg *log_msg);
static int logdPoll(struct android_log_logger_list *logger_list,
                    struct android_log_transport_context *transp);
static void logdClose(struct android_log_logger_list *logger_list,
                      struct android_log_transport_context *transp);
static int logdClear(struct android_log_logger *logger,
                     struct android_log_transport_context *transp);
static ssize_t logdSetSize(struct android_log_logger *logger,
                           struct android_log_transport_context *transp,
                           size_t size);
static ssize_t logdGetSize(struct android_log_logger *logger,
                           struct android_log_transport_context *transp);
static ssize_t logdGetReadableSize(struct android_log_logger *logger,
                                   struct android_log_transport_context *transp);
static ssize_t logdGetPrune(struct android_log_logger_list *logger,
                            struct android_log_transport_context *transp,
                            char *buf, size_t len);
static ssize_t logdSetPrune(struct android_log_logger_list *logger,
                            struct android_log_transport_context *transp,
                            char *buf, size_t len);
static ssize_t logdGetStats(struct android_log_logger_list *logger,
                            struct android_log_transport_context *transp,
                            char *buf, size_t len);

LIBLOG_HIDDEN struct android_log_transport_read logdLoggerRead = {
    .node = { &logdLoggerRead.node, &logdLoggerRead.node },
    .name = "logd",
    .available = logdAvailable,
    .version = logdVersion,
    .read = logdRead,
    .poll = logdPoll,
    .close = logdClose,
    .clear = logdClear,
    .getSize = logdGetSize,
    .setSize = logdSetSize,
    .getReadableSize = logdGetReadableSize,
    .getPrune = logdGetPrune,
    .setPrune = logdSetPrune,
    .getStats = logdGetStats,
};

static int logdAvailable(log_id_t logId)
{
    if (logId > LOG_ID_KERNEL) {
        return -EINVAL;
    }
    if (logId == LOG_ID_SECURITY) {
        uid_t uid = __android_log_uid();
        if (uid != AID_SYSTEM) {
            return -EPERM;
        }
    }
    if (access("/dev/socket/logdw", W_OK) == 0) {
        return 0;
    }
    return -EBADF;
}

/* Private copy of ../libcutils/socket_local_client.c prevent library loops */

#if defined(_WIN32)

LIBLOG_WEAK int socket_local_client(const char *name, int namespaceId, int type)
{
    errno = ENOSYS;
    return -ENOSYS;
}

#else /* !_WIN32 */

#include <sys/socket.h>
#include <sys/un.h>
#include <sys/select.h>
#include <sys/types.h>

/* Private copy of ../libcutils/socket_local.h prevent library loops */
#define FILESYSTEM_SOCKET_PREFIX "/tmp/"
#define ANDROID_RESERVED_SOCKET_PREFIX "/dev/socket/"
/* End of ../libcutils/socket_local.h */

#define LISTEN_BACKLOG 4

/* Documented in header file. */
LIBLOG_WEAK int socket_make_sockaddr_un(const char *name, int namespaceId,
                                        struct sockaddr_un *p_addr,
                                        socklen_t *alen)
{
    memset (p_addr, 0, sizeof (*p_addr));
    size_t namelen;

    switch (namespaceId) {
    case ANDROID_SOCKET_NAMESPACE_ABSTRACT:
#if defined(__linux__)
        namelen  = strlen(name);

        /* Test with length +1 for the *initial* '\0'. */
        if ((namelen + 1) > sizeof(p_addr->sun_path)) {
            goto error;
        }

        /*
         * Note: The path in this case is *not* supposed to be
         * '\0'-terminated. ("man 7 unix" for the gory details.)
         */

        p_addr->sun_path[0] = 0;
        memcpy(p_addr->sun_path + 1, name, namelen);
#else
        /* this OS doesn't have the Linux abstract namespace */

        namelen = strlen(name) + strlen(FILESYSTEM_SOCKET_PREFIX);
        /* unix_path_max appears to be missing on linux */
        if (namelen > sizeof(*p_addr)
                - offsetof(struct sockaddr_un, sun_path) - 1) {
            goto error;
        }

        strcpy(p_addr->sun_path, FILESYSTEM_SOCKET_PREFIX);
        strcat(p_addr->sun_path, name);
#endif
        break;

    case ANDROID_SOCKET_NAMESPACE_RESERVED:
        namelen = strlen(name) + strlen(ANDROID_RESERVED_SOCKET_PREFIX);
        /* unix_path_max appears to be missing on linux */
        if (namelen > sizeof(*p_addr)
                - offsetof(struct sockaddr_un, sun_path) - 1) {
            goto error;
        }

        strcpy(p_addr->sun_path, ANDROID_RESERVED_SOCKET_PREFIX);
        strcat(p_addr->sun_path, name);
        break;

    case ANDROID_SOCKET_NAMESPACE_FILESYSTEM:
        namelen = strlen(name);
        /* unix_path_max appears to be missing on linux */
        if (namelen > sizeof(*p_addr)
                - offsetof(struct sockaddr_un, sun_path) - 1) {
            goto error;
        }

        strcpy(p_addr->sun_path, name);
        break;

    default:
        /* invalid namespace id */
        return -1;
    }

    p_addr->sun_family = AF_LOCAL;
    *alen = namelen + offsetof(struct sockaddr_un, sun_path) + 1;
    return 0;
error:
    return -1;
}

/**
 * connect to peer named "name" on fd
 * returns same fd or -1 on error.
 * fd is not closed on error. that's your job.
 *
 * Used by AndroidSocketImpl
 */
LIBLOG_WEAK int socket_local_client_connect(int fd, const char *name,
                                            int namespaceId, int type __unused)
{
    struct sockaddr_un addr;
    socklen_t alen;
    int err;

    err = socket_make_sockaddr_un(name, namespaceId, &addr, &alen);

    if (err < 0) {
        goto error;
    }

    if(connect(fd, (struct sockaddr *) &addr, alen) < 0) {
        goto error;
    }

    return fd;

error:
    return -1;
}

/**
 * connect to peer named "name"
 * returns fd or -1 on error
 */
LIBLOG_WEAK int socket_local_client(const char *name, int namespaceId, int type)
{
    int s;

    s = socket(AF_LOCAL, type, 0);
    if(s < 0) return -1;

    if ( 0 > socket_local_client_connect(s, name, namespaceId, type)) {
        close(s);
        return -1;
    }

    return s;
}

#endif /* !_WIN32 */
/* End of ../libcutils/socket_local_client.c */

/* worker for sending the command to the logger */
static ssize_t send_log_msg(struct android_log_logger *logger,
                            const char *msg, char *buf, size_t buf_size)
{
    ssize_t ret;
    size_t len;
    char *cp;
    int errno_save = 0;
    int sock = socket_local_client("logd", ANDROID_SOCKET_NAMESPACE_RESERVED,
                                   SOCK_STREAM);
    if (sock < 0) {
        return sock;
    }

    if (msg) {
        snprintf(buf, buf_size, msg, logger ? logger->logId : (unsigned) -1);
    }

    len = strlen(buf) + 1;
    ret = TEMP_FAILURE_RETRY(write(sock, buf, len));
    if (ret <= 0) {
        goto done;
    }

    len = buf_size;
    cp = buf;
    while ((ret = TEMP_FAILURE_RETRY(read(sock, cp, len))) > 0) {
        struct pollfd p;

        if (((size_t)ret == len) || (buf_size < PAGE_SIZE)) {
            break;
        }

        len -= ret;
        cp += ret;

        memset(&p, 0, sizeof(p));
        p.fd = sock;
        p.events = POLLIN;

        /* Give other side 20ms to refill pipe */
        ret = TEMP_FAILURE_RETRY(poll(&p, 1, 20));

        if (ret <= 0) {
            break;
        }

        if (!(p.revents & POLLIN)) {
            ret = 0;
            break;
        }
    }

    if (ret >= 0) {
        ret += buf_size - len;
    }

done:
    if ((ret == -1) && errno) {
        errno_save = errno;
    }
    close(sock);
    if (errno_save) {
        errno = errno_save;
    }
    return ret;
}

static int check_log_success(char *buf, ssize_t ret)
{
    if (ret < 0) {
        return ret;
    }

    if (strncmp(buf, "success", 7)) {
        errno = EINVAL;
        return -1;
    }

    return 0;
}

static int logdClear(struct android_log_logger *logger,
                     struct android_log_transport_context *transp __unused)
{
    char buf[512];

    return check_log_success(buf,
        send_log_msg(logger, "clear %d", buf, sizeof(buf)));
}

/* returns the total size of the log's ring buffer */
static ssize_t logdGetSize(struct android_log_logger *logger,
                           struct android_log_transport_context *transp __unused)
{
    char buf[512];

    ssize_t ret = send_log_msg(logger, "getLogSize %d", buf, sizeof(buf));
    if (ret < 0) {
        return ret;
    }

    if ((buf[0] < '0') || ('9' < buf[0])) {
        return -1;
    }

    return atol(buf);
}

static ssize_t logdSetSize(
        struct android_log_logger *logger,
        struct android_log_transport_context *transp __unused,
        size_t size)
{
    char buf[512];

    snprintf(buf, sizeof(buf), "setLogSize %d %zu", logger->logId, size);

    return check_log_success(buf, send_log_msg(NULL, NULL, buf, sizeof(buf)));
}

/*
 * returns the readable size of the log's ring buffer (that is, amount of the
 * log consumed)
 */
static ssize_t logdGetReadableSize(
       struct android_log_logger *logger,
       struct android_log_transport_context *transp __unused)
{
    char buf[512];

    ssize_t ret = send_log_msg(logger, "getLogSizeUsed %d", buf, sizeof(buf));
    if (ret < 0) {
        return ret;
    }

    if ((buf[0] < '0') || ('9' < buf[0])) {
        return -1;
    }

    return atol(buf);
}

/*
 * returns the logger version
 */
static int logdVersion(
        struct android_log_logger *logger __unused,
        struct android_log_transport_context *transp __unused)
{
    uid_t uid = __android_log_uid();
    return ((uid != AID_ROOT) && (uid != AID_LOG) && (uid != AID_SYSTEM)) ? 3 : 4;
}

/*
 * returns statistics
 */
static ssize_t logdGetStats(struct android_log_logger_list *logger_list,
                            struct android_log_transport_context *transp __unused,
                            char *buf, size_t len)
{
    struct android_log_logger *logger;
    char *cp = buf;
    size_t remaining = len;
    size_t n;

    n = snprintf(cp, remaining, "getStatistics");
    n = min(n, remaining);
    remaining -= n;
    cp += n;

    logger_for_each(logger, logger_list) {
        n = snprintf(cp, remaining, " %d", logger->logId);
        n = min(n, remaining);
        remaining -= n;
        cp += n;
    }

    if (logger_list->pid) {
        snprintf(cp, remaining, " pid=%u", logger_list->pid);
    }

    return send_log_msg(NULL, NULL, buf, len);
}

static ssize_t logdGetPrune(
        struct android_log_logger_list *logger_list __unused,
        struct android_log_transport_context *transp __unused,
        char *buf, size_t len)
{
    return send_log_msg(NULL, "getPruneList", buf, len);
}

static ssize_t logdSetPrune(
        struct android_log_logger_list *logger_list __unused,
        struct android_log_transport_context *transp __unused,
        char *buf, size_t len)
{
    const char cmd[] = "setPruneList ";
    const size_t cmdlen = sizeof(cmd) - 1;

    if (strlen(buf) > (len - cmdlen)) {
        return -ENOMEM; /* KISS */
    }
    memmove(buf + cmdlen, buf, len - cmdlen);
    buf[len - 1] = '\0';
    memcpy(buf, cmd, cmdlen);

    return check_log_success(buf, send_log_msg(NULL, NULL, buf, len));
}


static void caught_signal(int signum __unused)
{
}

static int logdOpen(struct android_log_logger_list *logger_list,
                    struct android_log_transport_context *transp)
{
    struct android_log_logger *logger;
    struct sigaction ignore;
    struct sigaction old_sigaction;
    unsigned int old_alarm = 0;
    char buffer[256], *cp, c;
    int e, ret, remaining;

    int sock = transp->context.sock;
    if (sock > 0) {
        return sock;
    }

    if (!logger_list) {
        return -EINVAL;
    }

    sock = socket_local_client("logdr",
                               ANDROID_SOCKET_NAMESPACE_RESERVED,
                               SOCK_SEQPACKET);
    if (sock == 0) {
        /* Guarantee not file descriptor zero */
        int newsock = socket_local_client("logdr",
                                   ANDROID_SOCKET_NAMESPACE_RESERVED,
                                   SOCK_SEQPACKET);
        close(sock);
        sock = newsock;
    }
    if (sock <= 0) {
        if ((sock == -1) && errno) {
            return -errno;
        }
        return sock;
    }

    strcpy(buffer, (logger_list->mode & ANDROID_LOG_NONBLOCK) ?
            "dumpAndClose" : "stream");
    cp = buffer + strlen(buffer);

    strcpy(cp, " lids");
    cp += 5;
    c = '=';
    remaining = sizeof(buffer) - (cp - buffer);
    logger_for_each(logger, logger_list) {
        ret = snprintf(cp, remaining, "%c%u", c, logger->logId);
        ret = min(ret, remaining);
        remaining -= ret;
        cp += ret;
        c = ',';
    }

    if (logger_list->tail) {
        ret = snprintf(cp, remaining, " tail=%u", logger_list->tail);
        ret = min(ret, remaining);
        remaining -= ret;
        cp += ret;
    }

    if (logger_list->start.tv_sec || logger_list->start.tv_nsec) {
        if (logger_list->mode & ANDROID_LOG_WRAP) {
            // ToDo: alternate API to allow timeout to be adjusted.
            ret = snprintf(cp, remaining, " timeout=%u",
                           ANDROID_LOG_WRAP_DEFAULT_TIMEOUT);
            ret = min(ret, remaining);
            remaining -= ret;
            cp += ret;
        }
        ret = snprintf(cp, remaining, " start=%" PRIu32 ".%09" PRIu32,
                       logger_list->start.tv_sec,
                       logger_list->start.tv_nsec);
        ret = min(ret, remaining);
        remaining -= ret;
        cp += ret;
    }

    if (logger_list->pid) {
        ret = snprintf(cp, remaining, " pid=%u", logger_list->pid);
        ret = min(ret, remaining);
        cp += ret;
    }

    if (logger_list->mode & ANDROID_LOG_NONBLOCK) {
        /* Deal with an unresponsive logd */
        memset(&ignore, 0, sizeof(ignore));
        ignore.sa_handler = caught_signal;
        sigemptyset(&ignore.sa_mask);
        /* particularily useful if tombstone is reporting for logd */
        sigaction(SIGALRM, &ignore, &old_sigaction);
        old_alarm = alarm(30);
    }
    ret = write(sock, buffer, cp - buffer);
    e = errno;
    if (logger_list->mode & ANDROID_LOG_NONBLOCK) {
        if (e == EINTR) {
            e = ETIMEDOUT;
        }
        alarm(old_alarm);
        sigaction(SIGALRM, &old_sigaction, NULL);
    }

    if (ret <= 0) {
        close(sock);
        if ((ret == -1) && e) {
            return -e;
        }
        if (ret == 0) {
            return -EIO;
        }
        return ret;
    }

    return transp->context.sock = sock;
}

/* Read from the selected logs */
static int logdRead(struct android_log_logger_list *logger_list,
                    struct android_log_transport_context *transp,
                    struct log_msg *log_msg)
{
    int ret, e;
    struct sigaction ignore;
    struct sigaction old_sigaction;
    unsigned int old_alarm = 0;

    ret = logdOpen(logger_list, transp);
    if (ret < 0) {
        return ret;
    }

    memset(log_msg, 0, sizeof(*log_msg));

    if (logger_list->mode & ANDROID_LOG_NONBLOCK) {
        memset(&ignore, 0, sizeof(ignore));
        ignore.sa_handler = caught_signal;
        sigemptyset(&ignore.sa_mask);
        /* particularily useful if tombstone is reporting for logd */
        sigaction(SIGALRM, &ignore, &old_sigaction);
        old_alarm = alarm(30);
    }

    /* NOTE: SOCK_SEQPACKET guarantees we read exactly one full entry */
    ret = recv(ret, log_msg, LOGGER_ENTRY_MAX_LEN, 0);
    e = errno;

    if (logger_list->mode & ANDROID_LOG_NONBLOCK) {
        if ((ret == 0) || (e == EINTR)) {
            e = EAGAIN;
            ret = -1;
        }
        alarm(old_alarm);
        sigaction(SIGALRM, &old_sigaction, NULL);
    }

    if ((ret == -1) && e) {
        return -e;
    }
    return ret;
}

static int logdPoll(struct android_log_logger_list *logger_list,
                    struct android_log_transport_context *transp)
{
    struct pollfd p;

    int ret = logdOpen(logger_list, transp);
    if (ret < 0) {
        return ret;
    }

    memset(&p, 0, sizeof(p));
    p.fd = ret;
    p.events = POLLIN;
    ret = poll(&p, 1, 20);
    if ((ret > 0) && !(p.revents & POLLIN)) {
        ret = 0;
    }
    if ((ret == -1) && errno) {
        return -errno;
    }
    return ret;
}

/* Close all the logs */
static void logdClose(struct android_log_logger_list *logger_list __unused,
                      struct android_log_transport_context *transp)
{
    if (transp->context.sock > 0) {
        close (transp->context.sock);
        transp->context.sock = -1;
    }
}