android log丢失（三）动态切换logd机制和kernel机制

最新推荐文章于 2024-07-10 19:02:09 发布

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最新推荐文章于 2024-07-10 19:02:09 发布

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分类专栏： android log机制

本文链接：https://blog.youkuaiyun.com/kc58236582/article/details/72279744

之前我们分析了如何修改版本使log机制变成kernel的log机制。这篇博客我们继续修改可以动态切换，这样方便平时log丢失时调试。

我们先来看liblog库的编译mk文件，这个文件中主要修改了对使用使用logd 使用不同文件进行编译这块做了修改，增加了log_write_common.c 和log_read_common.c两个通用文件。

#
# Copyright (C) 2008-2014 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.
#
LOCAL_PATH := $(my-dir)
include $(CLEAR_VARS)

# This is what we want to do:
#  liblog_cflags := $(shell \
#   sed -n \
#       's/^\([0-9]*\)[ \t]*liblog[ \t].*/-DLIBLOG_LOG_TAG=\1/p' \
#       $(LOCAL_PATH)/event.logtags)
# so make sure we do not regret hard-coding it as follows:
liblog_cflags := -DLIBLOG_LOG_TAG=1005

#ifneq ($(TARGET_USES_LOGD),false)//注释了 不需要区分使用使用logd
#liblog_sources := logd_write.c log_event_write.c
#else
#liblog_sources := logd_write_kern.c log_event_write.c
#endif


liblog_sources := log_write_common.c log_event_write.c//增加log_write_common.c 

# some files must not be compiled when building against Mingw
# they correspond to features not used by our host development tools
# which are also hard or even impossible to port to native Win32

ifeq ($(strip $(USE_MINGW)),)
    liblog_sources += \
        event_tag_map.c
else
    liblog_sources += \
        uio.c
endif

liblog_host_sources := $(liblog_sources) fake_log_device.c event.logtags
liblog_target_sources := $(liblog_sources) log_time.cpp log_is_loggable.c
ifeq ($(strip $(USE_MINGW)),)
liblog_target_sources += logprint.c
endif

#ifneq ($(TARGET_USES_LOGD),false)//注释了，不用区分是否使用logd
#liblog_target_sources += log_read.c
#else
#liblog_target_sources += log_read_kern.c
#endif

liblog_target_sources += log_read_common.c//增加log_read_common.c
# Shared and static library for host
# ========================================================
LOCAL_MODULE := liblog
LOCAL_SRC_FILES := $(liblog_host_sources)
LOCAL_CFLAGS := -DFAKE_LOG_DEVICE=1 -Werror $(liblog_cflags)
LOCAL_MULTILIB := both
include $(BUILD_HOST_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := liblog
LOCAL_WHOLE_STATIC_LIBRARIES := liblog
ifeq ($(strip $(HOST_OS)),linux)
LOCAL_LDLIBS := -lrt
endif
LOCAL_MULTILIB := both
include $(BUILD_HOST_SHARED_LIBRARY)


# Shared and static library for target
# ========================================================
include $(CLEAR_VARS)
LOCAL_MODULE := liblog
LOCAL_SRC_FILES := $(liblog_target_sources)
LOCAL_CFLAGS := -Werror $(liblog_cflags)
include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := liblog
LOCAL_WHOLE_STATIC_LIBRARIES := liblog
LOCAL_CFLAGS := -Werror $(liblog_cflags)

# TODO: This is to work around b/19059885. Remove after root cause is fixed
LOCAL_LDFLAGS_arm := -Wl,--hash-style=both

include $(BUILD_SHARED_LIBRARY)

include $(call first-makefiles-under,$(LOCAL_PATH))

我们先来看log_read_common.c文件，这样主要就是将原来的logd_write.c 和logd_write_kern.c 文件进行合并。一些对外的接口，统一使用use_logd这个全局变量来控制，选择logd的函数，还是kernel的函数（logd的函数和kernel的函数就是static函数了，不用对外）。另外在__write_to_log_init函数中，第一次初始化的使用，先看system/etc/disable_logd是否有这样一个文件，有就将use_logd为0，代表使用kernel机制。

/*
 * Copyright (C) 2007-2014 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.
 */
#if (FAKE_LOG_DEVICE == 0)
#include <endian.h>
#endif
#include <errno.h>
#include <fcntl.h>
#if !defined(_WIN32)
#include <pthread.h>
#endif
#include <stdarg.h>
#include <stdatomic.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#if (FAKE_LOG_DEVICE == 0)
#include <sys/socket.h>
#include <sys/un.h>
#endif
#include <time.h>
#include <unistd.h>

#ifdef __BIONIC__
#include <android/set_abort_message.h>
#endif

#include <log/log.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>

#define LOGGER_LOG_MAIN     "log/main"
#define LOGGER_LOG_RADIO    "log/radio"
#define LOGGER_LOG_EVENTS   "log/events"
#define LOGGER_LOG_SYSTEM   "log/system"

#define LOG_BUF_SIZE 1024

#if FAKE_LOG_DEVICE
/* This will be defined when building for the host. */
#include "fake_log_device.h"
#endif

#define log_open(pathname, flags) open(pathname, (flags) | O_CLOEXEC)
#define log_writev(filedes, vector, count) writev(filedes, vector, count)
#define log_close(filedes) close(filedes)

static int __write_to_log_init(log_id_t, struct iovec *vec, size_t nr);
static int (*write_to_log)(log_id_t, struct iovec *vec, size_t nr) = __write_to_log_init;
#if !defined(_WIN32)
static pthread_mutex_t log_init_lock = PTHREAD_MUTEX_INITIALIZER;
#endif

#ifndef __unused
#define __unused  __attribute__((__unused__))
#endif

static int8_t use_logd = 1;//做区分

#if FAKE_LOG_DEVICE
static int log_fds_fake[(int)LOG_ID_MAX] = { -1, -1, -1, -1, -1 };
#else
static int logd_fd = -1;
static int pstore_fd = -1;
#endif

static int log_fds_kernel[(int)LOG_ID_MAX] = { -1, -1, -1, -1 };


/*
 * This is used by the C++ code to decide if it should write logs through
 * the C code.  Basically, if /dev/socket/logd is available, we're running in
 * the simulator rather than a desktop tool and want to use the device.
 */
static enum {
    kLogUninitialized, kLogNotAvailable, kLogAvailable
} g_log_status = kLogUninitialized;

static int __android_log_dev_available_logd(void)
{
    if (g_log_status == kLogUninitialized) {
        if (access("/dev/socket/logdw", W_OK) == 0)
            g_log_status = kLogAvailable;
        else
            g_log_status = kLogNotAvailable;
    }

    return (g_log_status == kLogAvailable);
}

static int __android_log_dev_available_kernel(void)
{
    if (g_log_status == kLogUninitialized) {
        if (access("/dev/"LOGGER_LOG_MAIN, W_OK) == 0)
            g_log_status = kLogAvailable;
        else
            g_log_status = kLogNotAvailable;
    }

    return (g_log_status == kLogAvailable);
}

int __android_log_dev_available(void)
{
    if (use_logd) {
        return __android_log_dev_available_logd();
    } else {
        return __android_log_dev_available_kernel();
    }
}

/* log_init_lock assumed */
static int __write_to_log_initialize()
{
    int i, ret = 0;

#if FAKE_LOG_DEVICE
    for (i = 0; i < LOG_ID_MAX; i++) {
        char buf[sizeof("/dev/log_system")];
        snprintf(buf, sizeof(buf), "/dev/log_%s", android_log_id_to_name(i));
        log_fds_fake[i] = fakeLogOpen(buf, O_WRONLY);
    }
#else
    if (pstore_fd < 0) {
        pstore_fd = TEMP_FAILURE_RETRY(open("/dev/pmsg0", O_WRONLY));
    }

    if (logd_fd < 0) {
        i = TEMP_FAILURE_RETRY(socket(PF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0));
        if (i < 0) {
            ret = -errno;
        } else if (TEMP_FAILURE_RETRY(fcntl(i, F_SETFL, O_NONBLOCK)) < 0) {
            ret = -errno;
            close(i);
        } else {
            struct sockaddr_un un;
            memset(&un, 0, sizeof(struct sockaddr_un));
            un.sun_family = AF_UNIX;
            strcpy(un.sun_path, "/dev/socket/logdw");

            if (TEMP_FAILURE_RETRY(connect(i, (struct sockaddr *)&un,
                                           sizeof(struct sockaddr_un))) < 0) {
                ret = -errno;
                close(i);
            } else {
                logd_fd = i;
            }
        }
    }
#endif

    return ret;
}


static int __write_to_log_daemon(log_id_t log_id, struct iovec *vec, size_t nr)
{
    ssize_t ret;
#if FAKE_LOG_DEVICE
    int log_fd;

    if (/*(int)log_id >= 0 &&*/ (int)log_id < (int)LOG_ID_MAX) {
        log_fd = log_fds_fake[(int)log_id];
    } else {
        return -EBADF;
    }
    do {
        ret = fakeLogWritev(log_fd, vec, nr);
        if (ret < 0) {
            ret = -errno;
        }
    } while (ret == -EINTR);
#else
    static const unsigned header_length = 2;
    struct iovec newVec[nr + header_length];
    android_log_header_t header;
    android_pmsg_log_header_t pmsg_header;
    struct timespec ts;
    size_t i, payload_size;
    static uid_t last_uid = AID_ROOT; /* logd *always* starts up as AID_ROOT */
    static pid_t last_pid = (pid_t) -1;
    static atomic_int_fast32_t dropped;

    if (!nr) {
        return -EINVAL;
    }

    if (last_uid == AID_ROOT) { /* have we called to get the UID yet? */
        last_uid = getuid();
    }
    if (last_pid == (pid_t) -1) {
        last_pid = getpid();
    }
    /*
     *  struct {
     *      // what we provide to pstore
     *      android_pmsg_log_header_t pmsg_header;
     *      // what we provide to socket
     *      android_log_header_t header;
     *      // caller provides
     *      union {
     *          struct {
     *              char     prio;
     *              char     payload[];
     *          } string;
     *          struct {
     *              uint32_t tag
     *              char     payload[];
     *          } binary;
     *      };
     *  };
     */

    clock_gettime(CLOCK_REALTIME, &ts);

    pmsg_header.magic = LOGGER_MAGIC;
    pmsg_header.len = sizeof(pmsg_header) + sizeof(header);
    pmsg_header.uid = last_uid;
    pmsg_header.pid = last_pid;

    header.tid = gettid();
    header.realtime.tv_sec = ts.tv_sec;
    header.realtime.tv_nsec = ts.tv_nsec;

    newVec[0].iov_base   = (unsigned char *) &pmsg_header;
    newVec[0].iov_len    = sizeof(pmsg_header);
    newVec[1].iov_base   = (unsigned char *) &header;
    newVec[1].iov_len    = sizeof(header);

    if (logd_fd > 0) {
        int32_t snapshot = atomic_exchange_explicit(&dropped, 0, memory_order_relaxed);
        if (snapshot) {
            android_log_event_int_t buffer;

            header.id = LOG_ID_EVENTS;
            buffer.header.tag = htole32(LIBLOG_LOG_TAG);
            buffer.payload.type = EVENT_TYPE_INT;
            buffer.payload.data = htole32(snapshot);

            newVec[2].iov_base = &buffer;
            newVec[2].iov_len  = sizeof(buffer);

            ret = TEMP_FAILURE_RETRY(writev(logd_fd, newVec + 1, 2));
            if (ret != (ssize_t)(sizeof(header) + sizeof(buffer))) {
                atomic_fetch_add_explicit(&dropped, snapshot, memory_order_relaxed);
            }
        }
    }

    header.id = log_id;

    for (payload_size = 0, i = header_length; i < nr + header_length; i++) {
        newVec[i].iov_base = vec[i - header_length].iov_base;
        payload_size += newVec[i].iov_len = vec[i - header_length].iov_len;

        if (payload_size > LOGGER_ENTRY_MAX_PAYLOAD) {
            newVec[i].iov_len -= payload_size - LOGGER_ENTRY_MAX_PAYLOAD;
            if (newVec[i].iov_len) {
                ++i;
            }
            payload_size = LOGGER_ENTRY_MAX_PAYLOAD;
            break;
        }
    }
    pmsg_header.len += payload_size;

    if (pstore_fd >= 0) {
        TEMP_FAILURE_RETRY(writev(pstore_fd, newVec, i));
    }

    if (last_uid == AID_LOGD) { /* logd, after initialization and priv drop */
        /*
         * ignore log messages we send to ourself (logd).
         * Such log messages are often generated by libraries we depend on
         * which use standard Android logging.
         */
        return 0;
    }

    if (logd_fd < 0) {
        return -EBADF;
    }

    /*
     * The write below could be lost, but will never block.
     *
     * To logd, we drop the pmsg_header
     *
     * ENOTCONN occurs if logd dies.
     * EAGAIN occurs if logd is overloaded.
     */
    ret = TEMP_FAILURE_RETRY(writev(logd_fd, newVec + 1, i - 1));
    if (ret < 0) {
        ret = -errno;
        if (ret == -ENOTCONN) {
#if !defined(_WIN32)
            pthread_mutex_lock(&log_init_lock);
#endif
            close(logd_fd);
            logd_fd = -1;
            ret = __write_to_log_initialize();
#if !defined(_WIN32)
            pthread_mutex_unlock(&log_init_lock);
#endif

            if (ret < 0) {
                return ret;
            }

            ret = TEMP_FAILURE_RETRY(writev(logd_fd, newVec + 1, i - 1));
            if (ret < 0) {
                ret = -errno;
            }
        }
    }

    if (ret > (ssize_t)sizeof(header)) {
        ret -= sizeof(header);
    } else if (ret == -EAGAIN) {
        atomic_fetch_add_explicit(&dropped, 1, memory_order_relaxed);
    }
#endif

    return ret;
}

#if FAKE_LOG_DEVICE
static const char *LOG_NAME[LOG_ID_MAX] = {
    [LOG_ID_MAIN] = "main",
    [LOG_ID_RADIO] = "radio",
    [LOG_ID_EVENTS] = "events",
    [LOG_ID_SYSTEM] = "system",
    [LOG_ID_CRASH] = "crash",
    [LOG_ID_KERNEL] = "kernel",
};

const char *android_log_id_to_name(log_id_t log_id)
{
    if (log_id >= LOG_ID_MAX) {
        log_id = LOG_ID_MAIN;
    }
    return LOG_NAME[log_id];
}
#endif

static int __write_to_log_init_logd(log_id_t log_id, struct iovec *vec, size_t nr)
{
#if !defined(_WIN32)
    pthread_mutex_lock(&log_init_lock);
#endif

    if (write_to_log == __write_to_log_init) {
        int ret;

        ret = __write_to_log_initialize();
        if (ret < 0) {
#if !defined(_WIN32)
            pthread_mutex_unlock(&log_init_lock);
#endif
#if (FAKE_LOG_DEVICE == 0)
            if (pstore_fd >= 0) {
                __write_to_log_daemon(log_id, vec, nr);
            }