ksud: support post-fs-data.sh run as daemon.

1. We should make the `post-fs-data.sh` use itself a process group, otherwise it will receive signal from other process and make it exit accidentally.
2. And we should also switch child process' cgroup out of parent process, otherwise it would be kill by cgroup.

userspace/ksud/src/module.rs

@@ -3,17 +3,18 @@ use java_properties::PropertiesIter;
 use log::{info, warn};
 use std::{
     collections::HashMap,
-    fs::{create_dir_all, remove_dir_all, File},
-    io::Cursor,
+    fs::{create_dir_all, remove_dir_all, File, OpenOptions},
+    io::{Cursor, Write},
+    os::unix::{prelude::PermissionsExt, process::CommandExt},
     path::{Path, PathBuf},
     process::{Command, Stdio},
-    str::FromStr, os::unix::prelude::PermissionsExt,
+    str::FromStr,
 };
 use subprocess::Exec;
 use zip_extensions::*;
 
-use crate::{utils::*, restorecon::setsyscon};
 use crate::{defs, restorecon};
+use crate::{restorecon::setsyscon, utils::*};
 
 use anyhow::{bail, ensure, Context, Result};
 
@@ -127,6 +128,30 @@ fn grow_image_size(img: &str, extra_size: u64) -> Result<()> {
     Ok(())
 }
 
+fn switch_cgroup(grp: &str, pid: u32) {
+    let path = Path::new(grp).join("cgroup.procs");
+    if !path.exists() {
+        return;
+    }
+
+    let fp = OpenOptions::new().append(true).open(path);
+    if let Ok(mut fp) = fp {
+        let _ = writeln!(fp, "{}", pid);
+    }
+}
+
+fn switch_cgroups() -> Result<()> {
+    let pid = std::process::id();
+    switch_cgroup("/acct", pid);
+    switch_cgroup("/dev/cg2_bpf", pid);
+    switch_cgroup("/sys/fs/cgroup", pid);
+    if getprop("ro.config.per_app_memcg")? != "false" {
+        switch_cgroup("/dev/memcg/apps", pid);
+    }
+
+    Ok(())
+}
+
 /// execute every modules' post-fs-data.sh
 pub fn exec_post_fs_data() -> Result<()> {
     let modules_dir = Path::new(defs::MODULE_DIR);
@@ -145,13 +170,22 @@ pub fn exec_post_fs_data() -> Result<()> {
         }
         println!("exec {} post-fs-data.sh", path.display());
 
+        // pre_exec is unsafe!
+        unsafe {
             Command::new("/system/bin/sh")
                 .arg(&post_fs_data)
+                .process_group(0)
+                .pre_exec(|| {
+                    // ignore the error?
+                    let _ = switch_cgroups();
+                    Ok(())
+                })
                 .current_dir(path)
                 .env("KSU", "true")
                 .status()
                 .with_context(|| format!("Failed to exec {}", post_fs_data.display()))?;
         }
+    }
 
     Ok(())
 }
@@ -169,7 +203,6 @@ fn ensure_resetprop() -> Result<()> {
 }
 
 pub fn load_system_prop() -> Result<()> {
-
     ensure_resetprop()?;
 
     let modules_dir = Path::new(defs::MODULE_DIR);
@@ -224,9 +257,11 @@ pub fn install_module(zip: String) -> Result<()> {
     zip_extract_file_to_memory(&zip_path, &entry_path, &mut buffer)?;
 
     let mut module_prop = HashMap::new();
-    PropertiesIter::new_with_encoding(Cursor::new(buffer), encoding::all::UTF_8).read_into(|k, v| {
+    PropertiesIter::new_with_encoding(Cursor::new(buffer), encoding::all::UTF_8).read_into(
+        |k, v| {
             module_prop.insert(k, v);
-    })?;
+        },
+    )?;
 
     let Some(module_id) = module_prop.get("id") else {
         bail!("module id not found in module.prop!");
@@ -417,7 +452,8 @@ pub fn uninstall_module(id: String) -> Result<()> {
             }
             let content = std::fs::read(module_prop)?;
             let mut module_id: String = String::new();
-            PropertiesIter::new_with_encoding(Cursor::new(content), encoding::all::UTF_8).read_into(|k, v| {
+            PropertiesIter::new_with_encoding(Cursor::new(content), encoding::all::UTF_8)
+                .read_into(|k, v| {
                     if k.eq("id") {
                         module_id = v;
                     }