nomount: Add a built-in NoMount backend

.github/workflows/ddk-lkm.yml

@@ -92,11 +92,22 @@ jobs:
         llvm-strip -d "$OUT_DIR/$OUTPUT_NAME"
         echo "Size after stripping: $(du -h "$OUT_DIR/$OUTPUT_NAME" | cut -f1)"
 
+    - name: Build nomount.ko
+      run: |
+        echo "=== Building NoMount for KMI: ${{ inputs.kmi }} ==="
+        # The checkout lives at $GITHUB_WORKSPACE; /github/workspace is only the
+        # scratch directory the kernelsu.ko step creates for its artifacts.
+        NOMOUNT_OUT="/github/workspace/out/aarch64/${{ inputs.kmi }}_nomount.ko" \
+          sh "$GITHUB_WORKSPACE/userspace/nomount/build-lkm.sh"
+        echo "Size: $(du -h "/github/workspace/out/aarch64/${{ inputs.kmi }}_nomount.ko" | cut -f1)"
+
     - name: Upload kernelsu.ko artifact
       uses: actions/upload-artifact@v7
       with:
         name: aarch64-${{ inputs.kmi }}-lkm
-        path: /github/workspace/out/aarch64/${{ inputs.kmi }}_kernelsu.ko
+        path: |
+          /github/workspace/out/aarch64/${{ inputs.kmi }}_kernelsu.ko
+          /github/workspace/out/aarch64/${{ inputs.kmi }}_nomount.ko
 
     - name: Build kernelsu.ko for x64
       env:

.github/workflows/ksud-extra.yml

@@ -32,6 +32,7 @@ jobs:
       if: ${{ inputs.pack_lkm }}
       run: |
         cp aarch64-android*-lkm/*_kernelsu.ko ./userspace/ksud/bin/aarch64/
+        cp aarch64-android*-lkm/*_nomount.ko ./userspace/ksud/bin/aarch64/
         cp x86_64-android*-lkm/*_kernelsu.ko ./userspace/ksud/bin/x86_64/
 
     - name: Prepare ksuinit

.github/workflows/ksud.yml

@@ -28,6 +28,7 @@ jobs:
       if: ${{ inputs.pack_lkm }}
       run: |
         cp aarch64-android*-lkm/*_kernelsu.ko ./userspace/ksud/bin/aarch64/
+        cp aarch64-android*-lkm/*_nomount.ko ./userspace/ksud/bin/aarch64/
         cp x86_64-android*-lkm/*_kernelsu.ko ./userspace/ksud/bin/x86_64/
 
     - name: Prepare ksuinit

README.md

@@ -49,7 +49,7 @@ Standard KernelSU modules are managed from the manager. A single active metamodu
 
 ### FolkZygisk
 
-FolkZygisk is a built-in Zygisk engine. The manager exposes its installation and activation controls, and `ksud` handles provider registration without conflicting with an existing Zygisk provider.
+FolkZygisk is a built-in Zygisk engine. The manager exposes its installation and activation controls, and `ksud` steps the built-in engine aside whenever an external Zygisk provider is active, so provider modules install normally.
 
 ### SUSFS
 
@@ -59,6 +59,12 @@ SUSFS management is capability-gated. The controls appear only on kernels that s
 
 Folk-Mount is the built-in module mount engine. It can run in auto, built-in, or metamodule mode.
 
+### NoMount
+
+NoMount is the built-in VFS redirection backend: instead of mounting anything it takes over path resolution and directory iteration in a kernel module, so `/proc/mounts` stays clean. The module ships inside ksud (embedded per KMI, built by this repository); the backend needs neither a metamodule nor the `nm` binary.
+
+The manager exposes the driver state, the number of active rules, visibility exclusions and a "mounting off" mode; the backend can be set to automatic, built-in Folk Mount, metamodule only, NoMount or off. Choosing NoMount falls back to the built-in engine when the driver is unavailable and says so on the settings page. Visibility is an exception list kept by ksud: every app sees the injected files until it is added, and the NoMount page copies each app profile's "unmount modules" verdict into that list on demand, so later profile changes need another copy.
+
 ## Security
 
 The manager authenticates itself by APK signature: only the trusted manager and apps the user has explicitly claimed can manage the kernel. Root access is whitelist-based, so only granted apps can reach `su`. See [SECURITY.md](./SECURITY.md) for vulnerability reporting.

README_CN.md

@@ -49,7 +49,7 @@ FinaSU 提供：
 
 ### FolkZygisk
 
-FolkZygisk 是内置的 Zygisk 引擎。管理器提供安装与激活控制，`ksud` 负责注册 provider，并与已有的 Zygisk provider 互不冲突。
+FolkZygisk 是内置的 Zygisk 引擎。管理器提供安装与激活控制；已有外置 Zygisk provider 时 `ksud` 会让内置引擎自动让位，因此 provider 模块可正常安装。
 
 ### SUSFS
 
@@ -59,6 +59,12 @@ SUSFS 管理按能力开关。仅在支持的内核上显示相关控件，每
 
 Folk-Mount 是内置的模块挂载引擎，可在自动、内置或 metamodule 模式间切换。
 
+### NoMount
+
+NoMount 是内建的 VFS 路径重定向后端：不产生任何挂载，而是由内核模块直接接管路径解析与目录遍历，因此不会污染 `/proc/mounts`。内核模块随 ksud 一起分发（按 KMI 内嵌，由本仓库自行编译），后端本身不依赖模块或 `nm` 二进制。
+
+管理器提供驱动状态、注入规则数、可见性例外与「关闭挂载」；挂载模式可选 `自动 / 内建 Folk Mount / 仅 metamodule / NoMount / 关闭`。选择 NoMount 时若驱动不可用会自动回退到内建引擎，并在设置页说明原因。可见性是一份由 ksud 保存的例外名单：名单内的应用看到原厂文件系统，其余应用都能看到注入的文件；NoMount 页可以按需把各应用 Profile 的「卸载模块」判定复制进这份名单，改动 Profile 后需要再复制一次。
+
 ## 安全提示
 
 管理器通过 APK 签名验证自身身份：只有受信任的管理器以及用户显式认领的应用才能管理内核。Root 权限基于白名单，只有被授权的应用才能访问 `su`。漏洞上报请参阅 [SECURITY.md](./SECURITY.md)。

build.sh

@@ -1,4 +1,8 @@
 #!/usr/bin/env bash
+# ANDROID_NDK_HOME is exported inside a subshell on purpose: every build stage
+# gets it for its own cargo invocation and the parent shell keeps none of it, so
+# ShellCheck's subshell-scope notes (SC2030/SC2031) do not apply here.
+# shellcheck disable=SC2030,SC2031
 #
 # FolkSU build driver - a local mirror of the GitHub Actions pipeline.
 #
@@ -55,8 +59,12 @@ have() { command -v "$1" >/dev/null 2>&1; }
 
 read_keystore_cfg() {
     [[ -f "$KEYSTORE_PROPS" ]] || die "missing $KEYSTORE_PROPS (copy sign.example.properties and fill it in)"
+    set -a
+    # The keystore file is a user-provided path, so its content cannot be
+    # analysed up front.
     # shellcheck disable=SC1090
-    set -a; source "$KEYSTORE_PROPS"; set +a
+    source "$KEYSTORE_PROPS"
+    set +a
     : "${KEYSTORE_FILE:?KEYSTORE_FILE not set in $KEYSTORE_PROPS}"
     : "${KEYSTORE_PASSWORD:?KEYSTORE_PASSWORD not set in $KEYSTORE_PROPS}"
     : "${KEY_ALIAS:?KEY_ALIAS not set in $KEYSTORE_PROPS}"
@@ -139,6 +147,42 @@ build_lkm() {
     done
 }
 
+# NoMount's kernel module is vendored at userspace/nomount (GPL-2.0-only, see
+# userspace/nomount/UPSTREAM.md) and built out-of-tree with the same DDK matrix
+# as kernelsu.ko. The stripped module is staged into ksud's embedded assets as
+# <kmi>_nomount.ko; it is never flashed and has no standalone module zip.
+build_nomount() {
+    have docker || die "docker is required to build the NoMount LKM"
+    mkdir -p userspace/ksud/bin/aarch64 userspace/nomount/build
+
+    local kmi image rel dest
+    for kmi in $KMIS; do
+        image="ghcr.io/ylarod/ddk-min:${kmi}-${DDK_RELEASE}"
+        log "building NoMount LKM for $kmi ($image)"
+        docker image inspect "$image" >/dev/null 2>&1 || docker pull "$image"
+
+        # The container sees the repository mounted at /build, so the output
+        # path has to be given in container coordinates.
+        rel="userspace/nomount/build/${kmi}_nomount.ko"
+        dest="$REPO_ROOT/$rel"
+        rm -f "$dest"
+        docker run --rm --privileged \
+            -v "$REPO_ROOT":/build \
+            -e CONFIG_NOMOUNT=m -e CC=clang -e NOMOUNT_OUT="/build/$rel" \
+            "$image" sh /build/userspace/nomount/build-lkm.sh
+
+        [[ -f "$dest" ]] || die "NoMount LKM for $kmi was not produced"
+        cp "$dest" userspace/ksud/bin/aarch64/
+        log "staged userspace/ksud/bin/aarch64/${kmi}_nomount.ko"
+
+        # The container runs as root, so hand the artifacts back to us.
+        docker run --rm -v "$REPO_ROOT/userspace/nomount":/n \
+            --entrypoint /bin/sh "$image" \
+            -c "chown -R $(id -u):$(id -g) /n" >/dev/null 2>&1 || \
+            warn "could not restore ownership of userspace/nomount/ (artifacts may be root-owned)"
+    done
+}
+
 abi_to_triple() {
     case "$1" in
         arm64-v8a)   echo aarch64-linux-android ;;
@@ -254,11 +298,13 @@ usage: ./build.sh <step> [step...]
 steps:
   lkm      build the kernel module(s) via the DDK docker image, stage them
            into userspace/ksud/bin/aarch64/ so ksud embeds them
+  nomount  build the vendored NoMount module(s) the same way, stage them as
+           userspace/ksud/bin/aarch64/<kmi>_nomount.ko for ksud to embed
   ksuinit  cross-compile the ksuinit helper ksud embeds (needed by boot-patch)
   ksud     cross-compile the ksud daemon with cargo-ndk
   apk      gradle assembleRelease (signed with manager/keystore.properties)
   repack   inject the freshly built ksud into the APK and re-sign it
-  all      lkm -> ksuinit -> ksud -> apk -> repack
+  all      lkm -> nomount -> ksuinit -> ksud -> apk -> repack
 
 environment overrides:
   KMIS=android15-6.6        kernel modules to build
@@ -278,11 +324,12 @@ main() {
     for step in "$@"; do
         case "$step" in
             lkm)     build_lkm ;;
+            nomount) build_nomount ;;
             ksuinit) build_ksuinit ;;
             ksud)    build_ksud ;;
             apk)     build_apk ;;
             repack)  build_repack ;;
-            all)     build_lkm; build_ksuinit; build_ksud; build_apk; build_repack ;;
+            all)     build_lkm; build_nomount; build_ksuinit; build_ksud; build_apk; build_repack ;;
             -h|--help|help) usage ;;
             *) die "unknown step: $step (try --help)" ;;
         esac

manager/app/src/main/java/me/weishu/kernelsu/data/model/FolkMount.kt

@@ -11,7 +11,9 @@ import org.json.JSONObject
 enum class FolkMountMode(val token: String) {
     AUTO("auto"),
     BUILTIN("builtin"),
-    METAMODULE("metamodule");
+    METAMODULE("metamodule"),
+    NOMOUNT("nomount"),
+    OFF("off");
 
     companion object {
         fun fromToken(token: String?): FolkMountMode? =
@@ -25,7 +27,9 @@ enum class FolkMountMode(val token: String) {
  */
 enum class FolkMountProvider(val token: String) {
     BUILTIN("builtin"),
-    METAMODULE("metamodule");
+    METAMODULE("metamodule"),
+    NOMOUNT("nomount"),
+    NONE("none");
 
     companion object {
         fun fromToken(token: String?): FolkMountProvider? =
@@ -34,14 +38,14 @@ enum class FolkMountProvider(val token: String) {
 }
 
 /**
- * Decoded `ksud mount status --json` payload (`schema_version = 1`).
+ * Decoded `ksud mount status --json` payload (`schema_version` 1 or 2).
  *
  * Property names map one-to-one to the ksud JSON keys:
  * [configuredMode] <- `configured_mode`, [nextProvider] <- `next_provider`,
  * [metamoduleId] <- `metamodule_id`, [metamoduleEnabled] <- `metamodule_enabled`,
  * [bootId] <- `boot_id`, [bootProvider] <- `boot_provider`,
  * [bootResult] <- `boot_result`, [targetCount] <- `target_count`,
- * [error] <- `error`.
+ * [bootWarning] <- `boot_warning` (schema 2), [error] <- `error`.
  */
 @Immutable
 data class FolkMountStatus(
@@ -53,10 +57,14 @@ data class FolkMountStatus(
     val bootProvider: FolkMountProvider?,
     val bootResult: String,
     val targetCount: Int?,
+    /** Provider-specific degradation for this boot, e.g. a NoMount fallback. */
+    val bootWarning: String?,
     val error: String?,
 ) {
     companion object {
-        const val SCHEMA_VERSION = 1
+        /** Newest schema this app understands; older schemas stay readable. */
+        const val SCHEMA_VERSION = 2
+        private const val OLDEST_SCHEMA_VERSION = 1
 
         /**
          * Decode a `ksud mount status --json` object.
@@ -66,6 +74,10 @@ data class FolkMountStatus(
          * than falling back to a default mode.
          */
         fun fromJson(json: JSONObject): FolkMountStatus {
+            val schema = json.optInt("schema_version", -1)
+            check(schema in OLDEST_SCHEMA_VERSION..SCHEMA_VERSION) {
+                "unsupported folk mount schema_version $schema"
+            }
             val configuredMode = FolkMountMode.fromToken(json.optStringOrNull("configured_mode"))
                 ?: error("folk mount status has no valid configured_mode")
             return FolkMountStatus(
@@ -77,6 +89,7 @@ data class FolkMountStatus(
                 bootProvider = FolkMountProvider.fromToken(json.optStringOrNull("boot_provider")),
                 bootResult = json.optString("boot_result", "unknown"),
                 targetCount = json.optIntOrNull("target_count"),
+                bootWarning = json.optStringOrNull("boot_warning"),
                 error = json.optStringOrNull("error"),
             )
         }