logd: initial checkin.

* Create a new userspace log daemon for handling logging messages.

Original-Change-Id: I75267df16359684490121e6c31cca48614d79856
Signed-off-by: Nick Kralevich <nnk@google.com>

* Merge conflicts
* rename new syslog daemon to logd to prevent confusion with bionic syslog
* replace racy getGroups call with KISS call to client->getGid()
* Timestamps are filed at logging source
* insert entries into list in timestamp order
* Added LogTimeEntry tail filtration handling
* Added region locking around LogWriter list
* separate threads for each writer
* /dev/socket/logd* permissions

Signed-off-by: Mark Salyzyn <salyzyn@google.com>

(cherry picked from commit 3e76e0a49760c4970b7cda6153e51026af98e4f3)

Author: Nick Kralevich <nnk@google.com>
Change-Id: Ice88b1412d8f9daa7f9119b2b5aaf684a5e28098

1 files changed, 115 insertions, 0 deletions

diff --git a/logd/main.cpp b/logd/main.cpp
new file mode 100644
index 000000000..667e5bbfc
--- /dev/null
+++ b/logd/main.cpp
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2012-2013 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 <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/capability.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <linux/prctl.h>
+
+#include "private/android_filesystem_config.h"
+#include "CommandListener.h"
+#include "LogBuffer.h"
+#include "LogListener.h"
+
+static int drop_privs() {
+    if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
+        return -1;
+    }
+
+    if (setgid(AID_LOGD) != 0) {
+        return -1;
+    }
+
+    if (setuid(AID_LOGD) != 0) {
+        return -1;
+    }
+
+    struct __user_cap_header_struct capheader;
+    struct __user_cap_data_struct capdata[2];
+    memset(&capheader, 0, sizeof(capheader));
+    memset(&capdata, 0, sizeof(capdata));
+    capheader.version = _LINUX_CAPABILITY_VERSION_3;
+    capheader.pid = 0;
+
+    capdata[CAP_TO_INDEX(CAP_SYSLOG)].permitted = CAP_TO_MASK(CAP_SYSLOG);
+    capdata[CAP_TO_INDEX(CAP_SYSLOG)].effective = CAP_TO_MASK(CAP_SYSLOG);
+    capdata[0].inheritable = 0;
+    capdata[1].inheritable = 0;
+
+    if (capset(&capheader, &capdata[0]) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+// Foreground waits for exit of the three main persistent threads that
+// are started here.  The three threads are created to manage UNIX
+// domain client sockets for writing, reading and controlling the user
+// space logger.  Additional transitory per-client threads are created
+// for each reader once they register.
+int main() {
+    if (drop_privs() != 0) {
+        return -1;
+    }
+
+    // Serves the purpose of managing the last logs times read on a
+    // socket connection, and as a reader lock on a range of log
+    // entries.
+
+    LastLogTimes *times = new LastLogTimes();
+
+    // LogBuffer is the object which is responsible for holding all
+    // log entries.
+
+    LogBuffer *logBuf = new LogBuffer(times);
+
+    // LogReader listens on /dev/socket/logdr. When a client
+    // connects, log entries in the LogBuffer are written to the client.
+
+    LogReader *reader = new LogReader(logBuf);
+    if (reader->startListener()) {
+        exit(1);
+    }
+
+    // LogListener listens on /dev/socket/logdw for client
+    // initiated log messages. New log entries are added to LogBuffer
+    // and LogReader is notified to send updates to connected clients.
+
+    LogListener *swl = new LogListener(logBuf, reader);
+    if (swl->startListener()) {
+        exit(1);
+    }
+
+    // Command listener listens on /dev/socket/logd for incoming logd
+    // administrative commands.
+
+    CommandListener *cl = new CommandListener(logBuf, reader, swl);
+    if (cl->startListener()) {
+        exit(1);
+    }
+
+    pause();
+    exit(0);
+}
+