Magisk/native/jni/core/log_daemon.cpp

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/* log_daemon.c - A dedicated daemon to monitor logcat
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*
* A universal logcat monitor for many usages. Add listeners to the list,
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* and the new log line will be sent through sockets to trigger
* asynchronous events without polling
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*/
#include <stdio.h>
#include <pthread.h>
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#include <unistd.h>
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#include <string.h>
#include <stdlib.h>
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#include <sys/wait.h>
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#include <fcntl.h>
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#include <vector>
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#include "magisk.h"
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#include "utils.h"
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#include "daemon.h"
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#include "flags.h"
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using namespace std;
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bool log_daemon_started = false;
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static vector<const char *> log_cmd, clear_cmd;
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static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
enum {
HIDE_EVENT,
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LOG_EVENT
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};
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#define EVENT_NUM 2
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struct log_listener {
int fd;
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bool (*filter)(const char *);
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};
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static bool am_proc_start_filter(const char *log) {
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return strstr(log, "am_proc_start") != nullptr;
}
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static bool magisk_log_filter(const char *log) {
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return !am_proc_start_filter(log);
}
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static struct log_listener events[] = {
{ /* HIDE_EVENT */
.fd = -1,
.filter = am_proc_start_filter
},
{ /* LOG_EVENT */
.fd = -1,
.filter = magisk_log_filter
}
};
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static void sigpipe_handler(int) {
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close(events[HIDE_EVENT].fd);
events[HIDE_EVENT].fd = -1;
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}
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static void *monitor_thread(void *) {
// Block SIGPIPE to prevent interruption
sigset_t block_set;
sigemptyset(&block_set);
sigaddset(&block_set, SIGPIPE);
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pthread_sigmask(SIG_SETMASK, &block_set, nullptr);
// Give the main daemon some time before we monitor it
sleep(5);
int fd;
char b;
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while (true) {
fd = connect_daemon();
write_int(fd, HANDSHAKE);
// This should hold unless the daemon is killed
read(fd, &b, sizeof(b));
// The main daemon crashed, spawn a new one
close(fd);
}
}
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static void *logcat_thread(void *) {
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int log_pid;
char line[4096];
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while (true) {
// Start logcat
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exec_t exec {
.fd = -1,
.argv = log_cmd.data()
};
log_pid = exec_command(exec);
FILE *logs = fdopen(exec.fd, "r");
while (fgets(line, sizeof(line), logs)) {
if (line[0] == '-')
continue;
size_t len = strlen(line);
pthread_mutex_lock(&lock);
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for (auto &event : events) {
if (event.fd > 0 && event.filter(line))
write(event.fd, line, len);
}
pthread_mutex_unlock(&lock);
}
fclose(logs);
kill(log_pid, SIGTERM);
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waitpid(log_pid, nullptr, 0);
LOGI("magisklogd: logcat output EOF");
// Clear buffer
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exec_command_sync(clear_cmd.data());
}
}
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static void log_daemon() {
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setsid();
LOGI("Magisk v" xstr(MAGISK_VERSION) "(" xstr(MAGISK_VER_CODE) ") logger started\n");
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strcpy(argv0, "magisklogd");
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// Set SIGPIPE handler
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struct sigaction act;
memset(&act, 0, sizeof(act));
act.sa_handler = sigpipe_handler;
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sigaction(SIGPIPE, &act, nullptr);
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// Setup log dumps
rename(LOGFILE, LOGFILE ".bak");
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events[LOG_EVENT].fd = xopen(LOGFILE, O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC | O_APPEND, 0644);
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// Construct cmdline
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log_cmd.push_back(MIRRDIR "/system/bin/logcat");
// Test whether these buffers actually works
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const char *b[] = { "main", "events", "crash" };
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for (auto &buffer : b) {
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if (exec_command_sync(MIRRDIR "/system/bin/logcat", "-b", buffer, "-d", "-f", "/dev/null") == 0) {
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log_cmd.push_back("-b");
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log_cmd.push_back(buffer);
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}
}
chmod("/dev/null", 0666);
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clear_cmd = log_cmd;
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log_cmd.insert(log_cmd.end(), { "-v", "threadtime", "-s", "am_proc_start", "Magisk" });
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#ifdef MAGISK_DEBUG
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log_cmd.push_back("*:F");
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#endif
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log_cmd.push_back(nullptr);
clear_cmd.push_back("-c");
clear_cmd.push_back(nullptr);
// Start worker threads
pthread_t thread;
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pthread_create(&thread, nullptr, monitor_thread, nullptr);
pthread_detach(thread);
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xpthread_create(&thread, nullptr, logcat_thread, nullptr);
pthread_detach(thread);
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// Handle socket requests
struct sockaddr_un sun;
socklen_t len = setup_sockaddr(&sun, LOG_SOCKET);
int sockfd = xsocket(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0);
if (xbind(sockfd, (struct sockaddr*) &sun, len))
exit(1);
xlisten(sockfd, 10);
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while(true) {
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int fd = xaccept4(sockfd, nullptr, nullptr, SOCK_CLOEXEC);
switch(read_int(fd)) {
case HIDE_CONNECT:
pthread_mutex_lock(&lock);
close(events[HIDE_EVENT].fd);
events[HIDE_EVENT].fd = fd;
pthread_mutex_unlock(&lock);
break;
case HANDSHAKE:
write_int(fd, HANDSHAKE);
default:
close(fd);
}
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}
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}
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bool start_log_daemon() {
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if (!log_daemon_started) {
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if (exec_command_sync(MIRRDIR "/system/bin/logcat", "-d", "-f", "/dev/null") == 0) {
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if (fork_dont_care() == 0)
log_daemon();
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log_daemon_started = true;
// Wait till we can connect to log_daemon and receive ack
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int fd = connect_log_daemon();
write_int(fd, HANDSHAKE);
read_int(fd);
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close(fd);
}
chmod("/dev/null", 0666);
}
return log_daemon_started;
}
int connect_log_daemon() {
if (!log_daemon_started)
return -1;
struct sockaddr_un sun;
socklen_t len = setup_sockaddr(&sun, LOG_SOCKET);
int fd = xsocket(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0);
while (connect(fd, (struct sockaddr*) &sun, len))
usleep(10000);
return fd;
}