Mount temp dir at /debug_ramdisk (#1226)

kernel/core_hook.c

@@ -569,6 +569,7 @@ int ksu_handle_setuid(struct cred *new, const struct cred *old)
 	try_umount("/vendor", true, 0);
 	try_umount("/product", true, 0);
 	try_umount("/data/adb/modules", false, MNT_DETACH);
+	try_umount("/debug_ramdisk", false, MNT_DETACH);
 
 	return 0;
 }

userspace/ksud/src/defs.rs

@@ -25,6 +25,8 @@ pub const MODULE_UPDATE_TMP_IMG: &str = concatcp!(WORKING_DIR, "update_tmp.img")
 // warning: this directory should not change, or you need to change the code in module_installer.sh!!!
 pub const MODULE_UPDATE_TMP_DIR: &str = concatcp!(ADB_DIR, "modules_update/");
 
+pub const TEMP_DIR: &str = "/debug_ramdisk/";
+
 pub const DISABLE_FILE_NAME: &str = "disable";
 pub const UPDATE_FILE_NAME: &str = "update";
 pub const REMOVE_FILE_NAME: &str = "remove";

userspace/ksud/src/event.rs

@@ -194,6 +194,11 @@ pub fn on_post_data_fs() -> Result<()> {
         warn!("do systemless mount failed: {}", e);
     }
 
+    // mount temp dir
+    if let Err(e) = mount::mount_tmpfs(defs::TEMP_DIR) {
+        warn!("do temp dir mount failed: {}", e);
+    }
+
     run_stage("post-mount", true);
 
     std::env::set_current_dir("/").with_context(|| "failed to chdir to /")?;

userspace/ksud/src/mount.rs

@@ -161,6 +161,16 @@ fn mount_overlayfs(
     Ok(())
 }
 
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn mount_tmpfs(dest: impl AsRef<Path>) -> Result<()> {
+    info!("mount tmpfs on {}", dest.as_ref().display());
+    Mount::builder()
+        .fstype(FilesystemType::from("tmpfs"))
+        .mount(KSU_OVERLAY_SOURCE, dest.as_ref())
+        .with_context(|| format!("mount tmpfs on {} failed", dest.as_ref().display()))?;
+    Ok(())
+}
+
 #[cfg(any(target_os = "linux", target_os = "android"))]
 fn bind_mount(from: impl AsRef<Path>, to: impl AsRef<Path>) -> Result<()> {
     info!(
@@ -276,3 +286,8 @@ pub fn umount_dir(_src: &str) -> Result<()> {
 pub fn mount_overlay(_dest: &String, _lower_dirs: &Vec<String>) -> Result<()> {
     unimplemented!()
 }
+
+#[cfg(not(any(target_os = "linux", target_os = "android")))]
+pub fn mount_tmpfs(_dest: impl AsRef<Path>) -> Result<()> {
+    unimplemented!()
+}