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platform_system_core
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platform_system_core/logd/main.cpp

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/*
* 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 <poll.h>
#include <sched.h>
#include <semaphore.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/capability.h>
#include <sys/klog.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <syslog.h>
#include <unistd.h>
#include <memory>
#include <cutils/properties.h>
#include <cutils/sched_policy.h>
#include <cutils/sockets.h>
#include <log/event_tag_map.h>
#include <private/android_filesystem_config.h>
#include <utils/threads.h>
#include "CommandListener.h"
#include "LogBuffer.h"
#include "LogListener.h"
#include "LogAudit.h"
#include "LogKlog.h"
#define KMSG_PRIORITY(PRI) \
'<', \
'0' + LOG_MAKEPRI(LOG_DAEMON, LOG_PRI(PRI)) / 10, \
'0' + LOG_MAKEPRI(LOG_DAEMON, LOG_PRI(PRI)) % 10, \
'>'
//
// The service is designed to be run by init, it does not respond well
// to starting up manually. When starting up manually the sockets will
// fail to open typically for one of the following reasons:
// EADDRINUSE if logger is running.
// EACCESS if started without precautions (below)
//
// Here is a cookbook procedure for starting up logd manually assuming
// init is out of the way, pedantically all permissions and selinux
// security is put back in place:
//
// setenforce 0
// rm /dev/socket/logd*
// chmod 777 /dev/socket
// # here is where you would attach the debugger or valgrind for example
// runcon u:r:logd:s0 /system/bin/logd </dev/null >/dev/null 2>&1 &
// sleep 1
// chmod 755 /dev/socket
// chown logd.logd /dev/socket/logd*
// restorecon /dev/socket/logd*
// setenforce 1
//
// If minimalism prevails, typical for debugging and security is not a concern:
//
// setenforce 0
// chmod 777 /dev/socket
// logd
//
static int drop_privs() {
struct sched_param param;
memset(&param, 0, sizeof(param));
if (set_sched_policy(0, SP_BACKGROUND) < 0) {
return -1;
}
if (sched_setscheduler((pid_t) 0, SCHED_BATCH, &param) < 0) {
return -1;
}
if (setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND) < 0) {
return -1;
}
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_AUDIT_CONTROL)].permitted |= CAP_TO_MASK(CAP_AUDIT_CONTROL);
capdata[0].effective = capdata[0].permitted;
capdata[1].effective = capdata[1].permitted;
capdata[0].inheritable = 0;
capdata[1].inheritable = 0;
if (capset(&capheader, &capdata[0]) < 0) {
return -1;
}
return 0;
}
// Property helper
static bool property_get_bool(const char *key, bool def) {
char property[PROPERTY_VALUE_MAX];
property_get(key, property, "");
if (!strcasecmp(property, "true")) {
return true;
}
if (!strcasecmp(property, "false")) {
return false;
}
return def;
}
// Remove the static, and use this variable
// globally for debugging if necessary. eg:
// write(fdDmesg, "I am here\n", 10);
static int fdDmesg = -1;
static sem_t uidName;
static uid_t uid;
static char *name;
static sem_t reinit;
static bool reinit_running = false;
static LogBuffer *logBuf = NULL;
static void *reinit_thread_start(void * /*obj*/) {
prctl(PR_SET_NAME, "logd.daemon");
set_sched_policy(0, SP_BACKGROUND);
setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND);
setgid(AID_SYSTEM);
setuid(AID_SYSTEM);
while (reinit_running && !sem_wait(&reinit) && reinit_running) {
// uidToName Privileged Worker
if (uid) {
name = NULL;
FILE *fp = fopen("/data/system/packages.list", "r");
if (fp) {
// This simple parser is sensitive to format changes in
// frameworks/base/services/core/java/com/android/server/pm/Settings.java
// A dependency note has been added to that file to correct
// this parser.
char *buffer = NULL;
size_t len;
while (getline(&buffer, &len, fp) > 0) {
char *userId = strchr(buffer, ' ');
if (!userId) {
continue;
}
*userId = '\0';
unsigned long value = strtoul(userId + 1, NULL, 10);
if (value != uid) {
continue;
}
name = strdup(buffer);
break;
}
free(buffer);
fclose(fp);
}
uid = 0;
sem_post(&uidName);
continue;
}
if (fdDmesg >= 0) {
static const char reinit_message[] = { KMSG_PRIORITY(LOG_INFO),
'l', 'o', 'g', 'd', '.', 'd', 'a', 'e', 'm', 'o', 'n', ':',
' ', 'r', 'e', 'i', 'n', 'i', 't', '\n' };
write(fdDmesg, reinit_message, sizeof(reinit_message));
}
// Anything that reads persist.<property>
if (logBuf) {
logBuf->init();
}
}
return NULL;
}
static sem_t sem_name;
char *android::uidToName(uid_t u) {
if (!u || !reinit_running) {
return NULL;
}
sem_wait(&sem_name);
// Not multi-thread safe, we use sem_name to protect
uid = u;
name = NULL;
sem_post(&reinit);
sem_wait(&uidName);
char *ret = name;
sem_post(&sem_name);
return ret;
}
// Serves as a global method to trigger reinitialization
// and as a function that can be provided to signal().
void reinit_signal_handler(int /*signal*/) {
sem_post(&reinit);
}
// tagToName converts an events tag into a name
const char *android::tagToName(uint32_t tag) {
static const EventTagMap *map;
if (!map) {
sem_wait(&sem_name);
if (!map) {
map = android_openEventTagMap(EVENT_TAG_MAP_FILE);
}
sem_post(&sem_name);
if (!map) {
return NULL;
}
}
return android_lookupEventTag(map, tag);
}
static bool property_get_bool_svelte(const char *key) {
bool not_user;
{
char property[PROPERTY_VALUE_MAX];
property_get("ro.build.type", property, "");
not_user = !!strcmp(property, "user");
}
return property_get_bool(key, not_user
&& !property_get_bool("ro.config.low_ram", false));
}
static void readDmesg(LogAudit *al, LogKlog *kl) {
if (!al && !kl) {
return;
}
int len = klogctl(KLOG_SIZE_BUFFER, NULL, 0);
if (len <= 0) {
return;
}
len += 1024; // Margin for additional input race or trailing nul
std::unique_ptr<char []> buf(new char[len]);
int rc = klogctl(KLOG_READ_ALL, buf.get(), len);
if (rc <= 0) {
return;
}
if (rc < len) {
len = rc + 1;
}
buf[len - 1] = '\0';
if (kl) {
kl->synchronize(buf.get());
}
for (char *ptr = NULL, *tok = buf.get();
(rc >= 0) && ((tok = log_strtok_r(tok, &ptr)));
tok = NULL) {
if (al) {
rc = al->log(tok);
}
if (kl) {
rc = kl->log(tok);
}
}
}
// Foreground waits for exit of the main persistent threads
// that are started here. The threads are created to manage
// UNIX domain client sockets for writing, reading and
// controlling the user space logger, and for any additional
// logging plugins like auditd and restart control. Additional
// transitory per-client threads are created for each reader.
int main(int argc, char *argv[]) {
int fdPmesg = -1;
bool klogd = property_get_bool_svelte("logd.klogd");
if (klogd) {
fdPmesg = open("/proc/kmsg", O_RDONLY | O_NDELAY);
}
fdDmesg = open("/dev/kmsg", O_WRONLY);
// issue reinit command. KISS argument parsing.
if ((argc > 1) && argv[1] && !strcmp(argv[1], "--reinit")) {
int sock = TEMP_FAILURE_RETRY(
socket_local_client("logd",
ANDROID_SOCKET_NAMESPACE_RESERVED,
SOCK_STREAM));
if (sock < 0) {
return -errno;
}
static const char reinit[] = "reinit";
ssize_t ret = TEMP_FAILURE_RETRY(write(sock, reinit, sizeof(reinit)));
if (ret < 0) {
return -errno;
}
struct pollfd p;
memset(&p, 0, sizeof(p));
p.fd = sock;
p.events = POLLIN;
ret = TEMP_FAILURE_RETRY(poll(&p, 1, 100));
if (ret < 0) {
return -errno;
}
if ((ret == 0) || !(p.revents & POLLIN)) {
return -ETIME;
}
static const char success[] = "success";
char buffer[sizeof(success) - 1];
memset(buffer, 0, sizeof(buffer));
ret = TEMP_FAILURE_RETRY(read(sock, buffer, sizeof(buffer)));
if (ret < 0) {
return -errno;
}
return strncmp(buffer, success, sizeof(success) - 1) != 0;
}
// Reinit Thread
sem_init(&reinit, 0, 0);
sem_init(&uidName, 0, 0);
sem_init(&sem_name, 0, 1);
pthread_attr_t attr;
if (!pthread_attr_init(&attr)) {
struct sched_param param;
memset(&param, 0, sizeof(param));
pthread_attr_setschedparam(&attr, &param);
pthread_attr_setschedpolicy(&attr, SCHED_BATCH);
if (!pthread_attr_setdetachstate(&attr,
PTHREAD_CREATE_DETACHED)) {
pthread_t thread;
reinit_running = true;
if (pthread_create(&thread, &attr, reinit_thread_start, NULL)) {
reinit_running = false;
}
}
pthread_attr_destroy(&attr);
}
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.
logBuf = new LogBuffer(times);
signal(SIGHUP, reinit_signal_handler);
if (property_get_bool_svelte("logd.statistics")) {
logBuf->enableStatistics();
}
// 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);
// Backlog and /proc/sys/net/unix/max_dgram_qlen set to large value
if (swl->startListener(300)) {
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);
}
// LogAudit listens on NETLINK_AUDIT socket for selinux
// initiated log messages. New log entries are added to LogBuffer
// and LogReader is notified to send updates to connected clients.
bool auditd = property_get_bool("logd.auditd", true);
LogAudit *al = NULL;
if (auditd) {
bool dmesg = property_get_bool("logd.auditd.dmesg", true);
al = new LogAudit(logBuf, reader, dmesg ? fdDmesg : -1);
}
LogKlog *kl = NULL;
if (klogd) {
kl = new LogKlog(logBuf, reader, fdDmesg, fdPmesg, al != NULL);
}
readDmesg(al, kl);
// failure is an option ... messages are in dmesg (required by standard)
if (kl && kl->startListener()) {
delete kl;
}
if (al && al->startListener()) {
delete al;
}
TEMP_FAILURE_RETRY(pause());
exit(0);
}
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