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

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-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 '<list> ...' 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

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logcat -P '1000 ~2002'

使用logcat -p查询

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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

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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

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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。

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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

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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

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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）

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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。

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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

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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());
}