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 = mmap_data::ro("/.backup/init");
    return init.contains("selinux_setup");
}