使用logcat命令增加logd白名单 黑名单

logd的白名单和黑名单我们在之前的logd中分析过了，这里的白名单和黑名单只是在logd丢失log时使用。logd丢失log会先删除黑名单的log，然后删除普通log。最后还不够的话再删除白名单的log。

这个命令对调试还是很有用 但本质原因还是cpu调度不够 加上log太多导致丢失。

命令使用

我们先看下logcat的help,注意下面-p（小写）代表获取白名单和黑名单，而-P（大写）代表设置白名单和黑名单。注意-P后面有单引号的

  -p              print prune white and ~black list. Service is specified as
                  UID, UID/PID or /PID. Weighed for quicker pruning if prefix
                  with ~, otherwise weighed for longevity if unadorned. All
                  other pruning activity is oldest first. Special case ~!
                  represents an automatic quicker pruning for the noisiest
                  UID as determined by the current statistics.
  -P ' ...' set prune white and ~black list, using same format as
                  printed above. Must be quoted.

设置uid1000为白名单 2002为黑名单

logcat -P '1000 ~2002'

使用logcat -p查询

root@lte26007:/ # logcat -p
1000 ~2002

当然我们也可以用pid

只用uid：
logcat –P uid
只用Pid:
logcat –P /pid
都用uid+pid:
logcat –P uid/pid

二、代码

2.1 logcat

logcat处理当是P命令，把字符串放到setPruneList，最后调用android_logger_set_prune_list函数

    case 'P':
        setPruneList = optarg;
    break;
    ......
    if (setPruneList) {
        size_t len = strlen(setPruneList);
        /*extra 32 bytes are needed by  android_logger_set_prune_list */
        size_t bLen = len + 32;
        char *buf = NULL;
        if (asprintf(&buf, "%-*s", (int)(bLen - 1), setPruneList) > 0) {
            buf[len] = '\0';
            if (android_logger_set_prune_list(logger_list, buf, bLen)) {
                logcat_panic(false, "failed to set the prune list");
            }
            free(buf);
        } else {
            logcat_panic(false, "failed to set the prune list (alloc)");
        }
    }

android_logger_set_prune_list函数就是往logd发送 setPruneList命令

int android_logger_set_prune_list(struct logger_list *logger_list __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));
}

send_log_msg就是获取logd的socket，往其write。

static ssize_t send_log_msg(struct 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->id : (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;
}

2.2 logd

我们再来看看logd的代码处理

2.2.1 设置白黑名单

int CommandListener::SetPruneListCmd::runCommand(SocketClient *cli,
                                         int argc, char **argv) {
    setname();
    if (!clientHasLogCredentials(cli)) {
        cli->sendMsg("Permission Denied");
        return 0;
    }

    char *cp = NULL;
    for (int i = 1; i < argc; ++i) {
        char *p = cp;
        if (p) {
            cp = NULL;
            asprintf(&cp, "%s %s", p, argv[i]);
            free(p);
        } else {
            asprintf(&cp, "%s", argv[i]);
        }
    }

    int ret = mBuf.initPrune(cp);
    free(cp);

    if (ret) {
        cli->sendMsg("Invalid");
        return 0;
    }

    cli->sendMsg("success");

    return 0;
}

这里主要调用了LogBuffer的initPrune函数

    int initPrune(char *cp) { return mPrune.init(cp); }

而这个函数又是调用了PruneList的init函数，我们来看下这个函数。首先就是把白黑名单清除，然后根据传入的字符串首个字母是~或者！就是这部分是黑名单，否则就是白名单。然后处理其uid、pid最后加入到list中（这里的list要么是mNaughty要么是mNice）

int PruneList::init(char *str) {
    mWorstUidEnabled = true;
    PruneCollection::iterator it;
    for (it = mNice.begin(); it != mNice.end();) {//清空白名单
        it = mNice.erase(it);
    }
    for (it = mNaughty.begin(); it != mNaughty.end();) {//清空黑名单
        it = mNaughty.erase(it);
    }

    if (!str) {
        return 0;
    }

    mWorstUidEnabled = false;

    for(; *str; ++str) {
        if (isspace(*str)) {
            continue;
        }

        PruneCollection *list;
        if ((*str == '~') || (*str == '!')) { // ~ supported, ! undocumented
            ++str;
            // special case, translates to worst UID at priority in blacklist
            if (*str == '!') {
                mWorstUidEnabled = true;
                ++str;
                if (!*str) {
                    break;
                }
                if (!isspace(*str)) {
                    return 1;
                }
                continue;
            }
            if (!*str) {
                return 1;
            }
            list = &mNaughty;//有~或者！开头的代表这次是黑名单
        } else {
            list = &mNice;//否则就是白名单
        }

        uid_t uid = Prune::uid_all;
        if (isdigit(*str)) {//uid
            uid = 0;
            do {
                uid = uid * 10 + *str++ - '0';
            } while (isdigit(*str));
        }

        pid_t pid = Prune::pid_all;
        if (*str == '/') {//有/代表pid
            ++str;
            if (isdigit(*str)) {
                pid = 0;
                do {
                    pid = pid * 10 + *str++ - '0';
                } while (isdigit(*str));
            }
        }

        if ((uid == Prune::uid_all) && (pid == Prune::pid_all)) {
            return 1;
        }

        if (*str && !isspace(*str)) {
            return 1;
        }

        // insert sequentially into list
        PruneCollection::iterator it = list->begin();
        while (it != list->end()) {
            Prune &p = *it;
            int m = uid - p.mUid;
            if (m == 0) {
                if (p.mPid == p.pid_all) {
                    break;
                }
                if ((pid == p.pid_all) && (p.mPid != p.pid_all)) {
                    it = list->erase(it);
                    continue;
                }
                m = pid - p.mPid;
            }
            if (m <= 0) {
                if (m < 0) {
                    list->insert(it, Prune(uid,pid));
                }
                break;
            }
            ++it;
        }
        if (it == list->end()) {
            list->push_back(Prune(uid,pid));//放入list，这里的list要么是白名单要么是黑名单
        }
        if (!*str) {
            break;
        }
    }

    return 0;
}

而最后判断是白名单还是黑名单就是通过下面的函数，最终还是看mNaughty和mNice列表是否有符合的。

bool PruneList::naughty(LogBufferElement *element) {
    PruneCollection::iterator it;
    for (it = mNaughty.begin(); it != mNaughty.end(); ++it) {
        if (!(*it).cmp(element)) {
            return true;
        }
    }
    return false;
}

bool PruneList::nice(LogBufferElement *element) {
    PruneCollection::iterator it;
    for (it = mNice.begin(); it != mNice.end(); ++it) {
        if (!(*it).cmp(element)) {
            return true;
        }
    }
    return false;
}

2.2 获取白黑名单

获取白黑名单logcat的代码就不看了，最终到如下函数，也就是把mNice和mNaughty的获取传给logcat再显示出来

void PruneList::format(char **strp) {
    if (*strp) {
        free(*strp);
        *strp = NULL;
    }

    static const char nice_format[] = " %s";
    const char *fmt = nice_format + 1;

    android::String8 string;

    if (mWorstUidEnabled) {
        string.setTo("~!");
        fmt = nice_format;
    }

    PruneCollection::iterator it;

    for (it = mNice.begin(); it != mNice.end(); ++it) {
        char *a = NULL;
        (*it).format(&a);

        string.appendFormat(fmt, a);
        fmt = nice_format;

        free(a);
    }

    static const char naughty_format[] = " ~%s";
    fmt = naughty_format + (*fmt != ' ');
    for (it = mNaughty.begin(); it != mNaughty.end(); ++it) {
        char *a = NULL;
        (*it).format(&a);

        string.appendFormat(fmt, a);
        fmt = naughty_format;

        free(a);
    }

    *strp = strdup(string.string());
}