Magisk/native/jni/init/getinfo.cpp

#include <sys/sysmacros.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/input.h>
#include <fcntl.h>
#include <vector>

#include <utils.hpp>

#include "init.hpp"

using namespace std;

template<typename Func>
static void parse_cmdline(const Func &fn) {
	char cmdline[4096];
	int fd = xopen("/proc/cmdline", O_RDONLY | O_CLOEXEC);
	cmdline[read(fd, cmdline, sizeof(cmdline))] = '\0';
	close(fd);

	char *tok, *eql, *tmp, *saveptr;
	saveptr = cmdline;
	while ((tok = strtok_r(nullptr, " \n", &saveptr)) != nullptr) {
		eql = strchr(tok, '=');
		if (eql) {
			*eql = '\0';
			if (eql[1] == '"') {
				tmp = strchr(saveptr, '"');
				if (tmp != nullptr) {
					*tmp = '\0';
					saveptr[-1] = ' ';
					saveptr = tmp + 1;
					eql++;
				}
			}
			fn(tok, eql + 1);
		} else {
			fn(tok, "");
		}
	}
}

#define test_bit(bit, array) (array[bit / 8] & (1 << (bit % 8)))

static bool check_key_combo() {
	uint8_t bitmask[(KEY_MAX + 1) / 8];
	vector<int> events;
	constexpr const char *name = "/event";

	for (int minor = 64; minor < 96; ++minor) {
		if (xmknod(name, S_IFCHR | 0444, makedev(13, minor)))
			continue;
		int fd = open(name, O_RDONLY | O_CLOEXEC);
		unlink(name);
		if (fd < 0)
			continue;
		memset(bitmask, 0, sizeof(bitmask));
		ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(bitmask)), bitmask);
		if (test_bit(KEY_VOLUMEUP, bitmask))
			events.push_back(fd);
		else
			close(fd);
	}
	if (events.empty())
		return false;

	run_finally fin([&]{ std::for_each(events.begin(), events.end(), close); });

	// Return true if volume up key is held for more than 3 seconds
	int count = 0;
	for (int i = 0; i < 500; ++i) {
		for (const int &fd : events) {
			memset(bitmask, 0, sizeof(bitmask));
			ioctl(fd, EVIOCGKEY(sizeof(bitmask)), bitmask);
			if (test_bit(KEY_VOLUMEUP, bitmask)) {
				count++;
				break;
			}
		}
		if (count >= 300) {
			LOGD("KEY_VOLUMEUP detected: disable system-as-root\n");
			return true;
		}
		// Check every 10ms
		usleep(10000);
	}
	return false;
}

static FILE *kmsg;
static char kmsg_buf[4096];
static int vprintk(const char *fmt, va_list ap) {
	vsnprintf(kmsg_buf + 12, sizeof(kmsg_buf) - 12, fmt, ap);
	return fprintf(kmsg, "%s", kmsg_buf);
}
void setup_klog() {
	// Shut down first 3 fds
	int fd;
	if (access("/dev/null", W_OK) == 0) {
		fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
	} else {
		mknod("/null", S_IFCHR | 0666, makedev(1, 3));
		fd = xopen("/null", O_RDWR | O_CLOEXEC);
		unlink("/null");
	}
	xdup3(fd, STDIN_FILENO, O_CLOEXEC);
	xdup3(fd, STDOUT_FILENO, O_CLOEXEC);
	xdup3(fd, STDERR_FILENO, O_CLOEXEC);
	if (fd > STDERR_FILENO)
		close(fd);

	if (access("/dev/kmsg", W_OK) == 0) {
		fd = xopen("/dev/kmsg", O_WRONLY | O_CLOEXEC);
	} else {
		mknod("/kmsg", S_IFCHR | 0666, makedev(1, 11));
		fd = xopen("/kmsg", O_WRONLY | O_CLOEXEC);
		unlink("/kmsg");
	}

	kmsg = fdopen(fd, "w");
	setbuf(kmsg, nullptr);
	log_cb.d = log_cb.i = log_cb.w = log_cb.e = vprintk;
	log_cb.ex = nop_ex;
	strcpy(kmsg_buf, "magiskinit: ");

	// Disable kmsg rate limiting
	if (FILE *rate = fopen("/proc/sys/kernel/printk_devkmsg", "w")) {
		fprintf(rate, "on\n");
		fclose(rate);
	}
}

#define read_dt(name, key) \
sprintf(file_name, "%s/" name, cmd->dt_dir); \
if (access(file_name, R_OK) == 0){ \
    string data = full_read(file_name); \
    if (!data.empty()) { \
        data.pop_back(); \
        strcpy(cmd->key, data.data()); \
    } \
}

void load_kernel_info(cmdline *cmd) {
	// Get kernel data using procfs and sysfs
	xmkdir("/proc", 0755);
	xmount("proc", "/proc", "proc", 0, nullptr);
	xmkdir("/sys", 0755);
	xmount("sysfs", "/sys", "sysfs", 0, nullptr);

	// Log to kernel
	setup_klog();

	parse_cmdline([=](string_view key, const char *value) -> void {
		if (key == "androidboot.slot_suffix") {
			strcpy(cmd->slot, value);
		} else if (key == "androidboot.slot") {
			cmd->slot[0] = '_';
			strcpy(cmd->slot + 1, value);
		} else if (key == "skip_initramfs") {
			cmd->skip_initramfs = true;
		} else if (key == "androidboot.force_normal_boot") {
			cmd->force_normal_boot = value[0] == '1';
		} else if (key == "rootwait") {
			cmd->rootwait = true;
		} else if (key == "androidboot.android_dt_dir") {
			strcpy(cmd->dt_dir, value);
		} else if (key == "androidboot.hardware") {
			strcpy(cmd->hardware, value);
		} else if (key == "androidboot.hardware.platform") {
			strcpy(cmd->hardware_plat, value);
		} else if (key == "androidboot.fstab_suffix") {
			strcpy(cmd->fstab_suffix, value);
		}
	});

	LOGD("Kernel cmdline info:\n");
	LOGD("skip_initramfs=[%d]\n", cmd->skip_initramfs);
	LOGD("force_normal_boot=[%d]\n", cmd->force_normal_boot);
	LOGD("rootwait=[%d]\n", cmd->rootwait);
	LOGD("slot=[%s]\n", cmd->slot);
	LOGD("dt_dir=[%s]\n", cmd->dt_dir);
	LOGD("fstab_suffix=[%s]\n", cmd->fstab_suffix);
	LOGD("hardware=[%s]\n", cmd->hardware);
	LOGD("hardware.platform=[%s]\n", cmd->hardware_plat);

	parse_prop_file("/.backup/.magisk", [=](auto key, auto value) -> bool {
		if (key == "RECOVERYMODE" && value == "true") {
			LOGD("Running in recovery mode, waiting for key...\n");
			cmd->skip_initramfs = !check_key_combo();
			return false;
		}
		return true;
	});

	if (cmd->dt_dir[0] == '\0')
		strcpy(cmd->dt_dir, DEFAULT_DT_DIR);

	char file_name[128];
	read_dt("fstab_suffix", fstab_suffix)
	read_dt("hardware", hardware)
	read_dt("hardware.platform", hardware_plat)

	LOGD("Device tree info:\n");
	LOGD("dt_dir=[%s]\n", cmd->dt_dir);
	LOGD("fstab_suffix=[%s]\n", cmd->fstab_suffix);
	LOGD("hardware=[%s]\n", cmd->hardware);
	LOGD("hardware.platform=[%s]\n", cmd->hardware_plat);
}

bool check_two_stage() {
	if (access("/apex", F_OK) == 0)
		return true;
	if (access("/system/bin/init", F_OK) == 0)
		return true;
	// If we still have no indication, parse the original init and see what's up
	auto init = raw_data::mmap_ro("/.backup/init");
	return init.contains("selinux_setup");
}