diff --git a/build.gradle.kts b/build.gradle.kts
index 91b01d6..8661ed5 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -33,6 +33,9 @@ val moduleId by extra("zygisksu")
 val moduleName by extra("Zygisk on KernelSU")
 val verName by extra("v4-0.4.1")
 val verCode by extra(gitCommitCount)
+val minKsuVersion by extra(10626)
+val maxKsuVersion by extra(100000)
+val minMagiskVersion by extra(25000)
 
 val androidMinSdkVersion by extra(29)
 val androidTargetSdkVersion by extra(33)
diff --git a/module/build.gradle.kts b/module/build.gradle.kts
index 7a39072..9ce479f 100644
--- a/module/build.gradle.kts
+++ b/module/build.gradle.kts
@@ -11,6 +11,9 @@ val moduleId: String by rootProject.extra
 val moduleName: String by rootProject.extra
 val verCode: Int by rootProject.extra
 val verName: String by rootProject.extra
+val minKsuVersion: Int by rootProject.extra
+val maxKsuVersion: Int by rootProject.extra
+val minMagiskVersion: Int by rootProject.extra
 
 android.buildFeatures {
     androidResources = false
@@ -49,7 +52,10 @@ androidComponents.onVariants { variant ->
         from("$projectDir/src") {
             include("customize.sh", "daemon.sh")
             val tokens = mapOf(
-                "DEBUG" to if (buildTypeLowered == "debug") "true" else "false"
+                "DEBUG" to if (buildTypeLowered == "debug") "true" else "false",
+                "MIN_KSU_VERSION" to "$minKsuVersion",
+                "MAX_KSU_VERSION" to "$maxKsuVersion",
+                "MIN_MAGISK_VERSION" to "$minMagiskVersion",
             )
             filter<ReplaceTokens>("tokens" to tokens)
             filter<FixCrLfFilter>("eol" to FixCrLfFilter.CrLf.newInstance("lf"))
diff --git a/module/src/customize.sh b/module/src/customize.sh
index aa120b1..2e04098 100644
--- a/module/src/customize.sh
+++ b/module/src/customize.sh
@@ -2,19 +2,28 @@
 SKIPUNZIP=1
 
 DEBUG=@DEBUG@
+MIN_KSU_VERSION=@MIN_KSU_VERSION@
+MAX_KSU_VERSION=@MAX_KSU_VERSION@
+MIN_MAGISK_VERSION=@MIN_MAGISK_VERSION@
 
 if [ "$BOOTMODE" ] && [ "$KSU" ]; then
   ui_print "- Installing from KernelSU app"
   ui_print "- KernelSU version: $KSU_KERNEL_VER_CODE (kernel) + $KSU_VER_CODE (ksud)"
-  if [ "$KSU_KERNEL_VER_CODE" ] && [ "$KSU_KERNEL_VER_CODE" -lt 10575 ]; then
+  if [ "$KSU_KERNEL_VER_CODE" ] && [ "$KSU_KERNEL_VER_CODE" -lt "$MIN_KSU_VERSION" ]; then
     ui_print "*********************************************************"
     ui_print "! KernelSU version is too old!"
     ui_print "! Please update KernelSU to latest version"
     abort    "*********************************************************"
+  elif [ "$KSU_KERNEL_VER_CODE" -ge "$MAX_KSU_VERSION" ]; then
+    ui_print "*********************************************************"
+    ui_print "! KernelSU version abnormal!"
+    ui_print "! Please integrate KernelSU into your kernel"
+    ui_print "  as submodule instead of copying the source code"
+    abort    "*********************************************************"
   fi
 elif [ "$BOOTMODE" ] && [ "$MAGISK_VER_CODE" ]; then
   ui_print "- Installing from Magisk app"
-  if [ "$MAGISK_VER_CODE" -lt 25000 ]; then
+  if [ "$MAGISK_VER_CODE" -lt "$MIN_MAGISK_VERSION" ]; then
     ui_print "*********************************************************"
     ui_print "! Magisk version is too old!"
     ui_print "! Please update Magisk to latest version"
diff --git a/zygiskd/Cargo.toml b/zygiskd/Cargo.toml
index 60f2c57..49bb074 100644
--- a/zygiskd/Cargo.toml
+++ b/zygiskd/Cargo.toml
@@ -10,11 +10,13 @@ android_logger = "0.12.0"
 anyhow = { version = "1.0.68", features = ["backtrace"] }
 clap = { version = "4.1.4", features = ["derive"] }
 const_format = "0.2.5"
+konst = "0.3.4"
 lazy_static = "1.4.0"
 log = "0.4.17"
 memfd = "0.6.2"
 nix = "0.26.2"
 num_enum = "0.5.9"
+once_cell = "1.17.1"
 passfd = "0.1.5"
 rand = "0.8.5"
 
diff --git a/zygiskd/build.gradle.kts b/zygiskd/build.gradle.kts
index 1aa7c8d..7d07fdb 100644
--- a/zygiskd/build.gradle.kts
+++ b/zygiskd/build.gradle.kts
@@ -5,6 +5,9 @@ plugins {
 
 val verName: String by rootProject.extra
 val verCode: Int by rootProject.extra
+val minKsuVersion: Int by rootProject.extra
+val maxKsuVersion: Int by rootProject.extra
+val minMagiskVersion: Int by rootProject.extra
 
 android.buildFeatures {
     androidResources = false
@@ -23,5 +26,8 @@ cargo {
         spec.environment("ANDROID_NDK_HOME", android.ndkDirectory.path)
         spec.environment("VERSION_CODE", verCode)
         spec.environment("VERSION_NAME", verName)
+        spec.environment("MIN_KSU_VERSION", minKsuVersion)
+        spec.environment("MAX_KSU_VERSION", maxKsuVersion)
+        spec.environment("MIN_MAGISK_VERSION", minMagiskVersion)
     }
 }
diff --git a/zygiskd/src/constants.rs b/zygiskd/src/constants.rs
index 4fea015..d87ba9c 100644
--- a/zygiskd/src/constants.rs
+++ b/zygiskd/src/constants.rs
@@ -1,10 +1,15 @@
 use const_format::concatcp;
+use konst::primitive::parse_i32;
+use konst::unwrap_ctx;
 use log::LevelFilter;
 use num_enum::TryFromPrimitive;
 
 pub const VERSION_NAME: &str = env!("VERSION_NAME");
 pub const VERSION_CODE: &str = env!("VERSION_CODE");
 pub const VERSION_FULL: &str = concatcp!(VERSION_NAME, " (", VERSION_CODE, ")");
+pub const MIN_KSU_VERSION: i32 = unwrap_ctx!(parse_i32(env!("MIN_KSU_VERSION")));
+pub const MAX_KSU_VERSION: i32 = unwrap_ctx!(parse_i32(env!("MAX_KSU_VERSION")));
+pub const MIN_MAGISK_VERSION: i32 = unwrap_ctx!(parse_i32(env!("MIN_MAGISK_VERSION")));
 
 #[cfg(debug_assertions)]
 pub const MAX_LOG_LEVEL: LevelFilter = LevelFilter::Trace;
diff --git a/zygiskd/src/main.rs b/zygiskd/src/main.rs
index 4c94d1b..4dd46db 100644
--- a/zygiskd/src/main.rs
+++ b/zygiskd/src/main.rs
@@ -8,6 +8,7 @@ mod utils;
 mod watchdog;
 mod zygiskd;
 
+use anyhow::Result;
 use clap::{Subcommand, Parser};
 
 #[derive(Parser, Debug)]
@@ -36,19 +37,23 @@ fn init_android_logger(tag: &str) {
     );
 }
 
+fn start() -> Result<()> {
+    root_impl::setup()?;
+    let cli = Args::parse();
+    match cli.command {
+        Commands::Watchdog => watchdog::entry()?,
+        Commands::Daemon => zygiskd::entry()?,
+        Commands::Companion { fd } => companion::entry(fd)?,
+    };
+    Ok(())
+}
+
 fn main() {
     let process = std::env::args().next().unwrap();
     let nice_name = process.split('/').last().unwrap();
     init_android_logger(nice_name);
 
-    let cli = Args::parse();
-    let result = match cli.command {
-        Commands::Watchdog => watchdog::entry(),
-        Commands::Daemon => zygiskd::entry(),
-        Commands::Companion { fd } => companion::entry(fd),
-    };
-
-    if let Err(e) = &result {
+    if let Err(e) = start() {
         log::error!("Crashed: {}\n{}", e, e.backtrace());
     }
 }
diff --git a/zygiskd/src/root_impl/kernelsu.rs b/zygiskd/src/root_impl/kernelsu.rs
index 3ba96a6..a34c148 100644
--- a/zygiskd/src/root_impl/kernelsu.rs
+++ b/zygiskd/src/root_impl/kernelsu.rs
@@ -1,15 +1,22 @@
+use anyhow::{bail, Result};
 use nix::libc::prctl;
+use crate::constants::{MIN_KSU_VERSION, MAX_KSU_VERSION};
 
 const KERNEL_SU_OPTION: i32 = 0xdeadbeefu32 as i32;
 
-const CMD_GET_VERSION: u64 = 2;
-const CMD_GET_ALLOW_LIST: u64 = 5;
-const CMD_GET_DENY_LIST: u64 = 6;
+const CMD_GET_VERSION: usize = 2;
+const CMD_GET_ALLOW_LIST: usize = 5;
+const CMD_GET_DENY_LIST: usize = 6;
 
-pub fn is_kernel_su() -> bool {
+pub fn is_kernel_su() -> Result<bool> {
     let mut version = 0;
     unsafe { prctl(KERNEL_SU_OPTION, CMD_GET_VERSION, &mut version as *mut i32) };
-    version > 0
+    return match version {
+        0 => Ok(false),
+        MIN_KSU_VERSION..=MAX_KSU_VERSION => Ok(true),
+        1..=MIN_KSU_VERSION => bail!("KernelSU version too old: {}", version),
+        _ => bail!("KernelSU version abnormal: {}", version)
+    }
 }
 
 pub fn uid_on_allowlist(uid: i32) -> bool {
diff --git a/zygiskd/src/root_impl/magisk.rs b/zygiskd/src/root_impl/magisk.rs
index e2d487c..3dac272 100644
--- a/zygiskd/src/root_impl/magisk.rs
+++ b/zygiskd/src/root_impl/magisk.rs
@@ -1,13 +1,30 @@
+use anyhow::{bail, Result};
+use std::process::{Command, Stdio};
+use crate::constants::MIN_MAGISK_VERSION;
 
-
-pub fn is_magisk() -> bool {
-    todo!("is_magisk")
+pub fn is_magisk() -> Result<bool> {
+    let version: Option<i32> = Command::new("magisk")
+        .arg("--version")
+        .stdout(Stdio::piped())
+        .spawn().ok()
+        .and_then(|child| child.wait_with_output().ok())
+        .and_then(|output| String::from_utf8(output.stdout).ok())
+        .and_then(|output| output.parse().ok());
+    if let Some(version) = version {
+        if version < MIN_MAGISK_VERSION {
+            bail!("Magisk version too old: {}", version);
+        }
+        return Ok(true);
+    }
+    Ok(false)
 }
 
 pub fn uid_on_allowlist(uid: i32) -> bool {
-    todo!("uid_on_allowlist")
+    // TODO: uid_on_allowlist
+    return false;
 }
 
 pub fn uid_on_denylist(uid: i32) -> bool {
-    todo!("uid_on_denylist")
+    // TODO: uid_on_denylist
+    return false;
 }
diff --git a/zygiskd/src/root_impl/mod.rs b/zygiskd/src/root_impl/mod.rs
index 870579c..67137cb 100644
--- a/zygiskd/src/root_impl/mod.rs
+++ b/zygiskd/src/root_impl/mod.rs
@@ -1,24 +1,37 @@
 mod kernelsu;
 mod magisk;
 
-pub fn uid_on_allowlist(uid: i32) -> bool {
-    if kernelsu::is_kernel_su() {
-        kernelsu::uid_on_allowlist(uid)
-    } else if magisk::is_magisk() {
-        magisk::uid_on_allowlist(uid)
+use once_cell::sync::OnceCell;
+use anyhow::{bail, Result};
+
+enum RootImpl {
+    KernelSU,
+    Magisk,
+}
+
+static ROOT_IMPL: OnceCell<RootImpl> = OnceCell::new();
+
+pub fn setup() -> Result<()> {
+    if kernelsu::is_kernel_su()? {
+        let _ = ROOT_IMPL.set(RootImpl::KernelSU);
+    } else if magisk::is_magisk()? {
+        let _ = ROOT_IMPL.set(RootImpl::Magisk);
     } else {
-        log::warn!("Unknown root implementation");
-        false
+        bail!("Unknown root implementation");
+    }
+    Ok(())
+}
+
+pub fn uid_on_allowlist(uid: i32) -> bool {
+    match ROOT_IMPL.get().unwrap() {
+        RootImpl::KernelSU => kernelsu::uid_on_allowlist(uid),
+        RootImpl::Magisk => magisk::uid_on_allowlist(uid),
     }
 }
 
 pub fn uid_on_denylist(uid: i32) -> bool {
-    if kernelsu::is_kernel_su() {
-        kernelsu::uid_on_denylist(uid)
-    } else if magisk::is_magisk() {
-        magisk::uid_on_denylist(uid)
-    } else {
-        log::warn!("Unknown root implementation");
-        false
+    match ROOT_IMPL.get().unwrap() {
+        RootImpl::KernelSU => kernelsu::uid_on_denylist(uid),
+        RootImpl::Magisk => magisk::uid_on_denylist(uid),
     }
 }