Implement preinit related features in Rust

native/src/Cargo.lock

@@ -72,6 +72,7 @@ dependencies = [
  "argh",
  "bytemuck",
  "cfg-if",
+ "const_format",
  "cxx",
  "cxx-gen",
  "libc",
@@ -467,7 +468,6 @@ version = "0.0.0"
 dependencies = [
  "base",
  "bytemuck",
- "const_format",
  "cxx",
  "cxx-gen",
  "num-derive",

native/src/base/Cargo.toml

@@ -22,3 +22,4 @@ argh = { workspace = true }
 bytemuck = { workspace = true }
 num-traits = { workspace = true }
 num-derive = { workspace = true }
+const_format = { workspace = true }

native/src/base/cstr.rs

@@ -451,6 +451,7 @@ pub struct FsPathBuf<'a>(&'a mut dyn Utf8CStrWrite);
 
 impl<'a> FsPathBuf<'a> {
     pub fn new(value: &'a mut dyn Utf8CStrWrite) -> Self {
+        value.clear();
         FsPathBuf(value)
     }
 
@@ -656,7 +657,8 @@ macro_rules! cstr {
         );
         #[allow(unused_unsafe)]
         unsafe {
-            $crate::Utf8CStr::from_bytes_unchecked(concat!($($str)*, "\0").as_bytes())
+            $crate::Utf8CStr::from_bytes_unchecked($crate::const_format::concatcp!($($str)*, "\0")
+                .as_bytes())
         }
     }};
 }

native/src/base/lib.rs

@@ -3,6 +3,7 @@
 #![feature(io_error_more)]
 #![feature(utf8_chunks)]
 
+pub use const_format;
 pub use libc;
 use num_traits::FromPrimitive;
 

native/src/core/Cargo.toml

@@ -17,5 +17,4 @@ cxx = { workspace = true }
 num-traits = { workspace = true }
 num-derive = { workspace = true }
 quick-protobuf = { workspace = true }
-const_format = { workspace = true }
 bytemuck = { workspace = true, features = ["derive"] }

native/src/core/bootstages.cpp

@@ -19,157 +19,6 @@ bool zygisk_enabled = false;
 /*********
  * Setup *
  *********/
-static void setup_mounts() {
-    LOGI("* Magic mount setup\n");
-    auto self_mount_info = parse_mount_info("self");
-    char path[PATH_MAX];
-
-    // Bind remount module root to clear nosuid
-    ssprintf(path, sizeof(path), "%s/" MODULEMNT, get_magisk_tmp());
-    xmkdir(path, 0755);
-    xmount(MODULEROOT, path, nullptr, MS_BIND, nullptr);
-    xmount(nullptr, path, nullptr, MS_REMOUNT | MS_BIND | MS_RDONLY, nullptr);
-    xmount(nullptr, path, nullptr, MS_PRIVATE, nullptr);
-
-    // Check and mount preinit mirror
-    char dev_path[64];
-    ssprintf(dev_path, sizeof(dev_path), "%s/" PREINITDEV, get_magisk_tmp());
-    if (struct stat st{}; stat(dev_path, &st) == 0 && S_ISBLK(st.st_mode)) {
-        // DO NOT mount the block device directly, as we do not know the flags and configs
-        // to properly mount the partition; mounting block devices directly as rw could cause
-        // crashes if the filesystem driver is crap (e.g. some broken F2FS drivers).
-        // What we do instead is to scan through the current mountinfo and find a pre-existing
-        // mount point mounting our desired partition, and then bind mount the target folder.
-        dev_t preinit_dev = st.st_rdev;
-        bool mounted = false;
-        ssprintf(path, sizeof(path), "%s/" PREINITMIRR, get_magisk_tmp());
-        for (const auto &info: self_mount_info) {
-            if (info.root == "/" && info.device == preinit_dev) {
-                auto flags = split_view(info.fs_option, ",");
-                auto rw = std::any_of(flags.begin(), flags.end(), [](const auto &flag) {
-                    return flag == "rw"sv;
-                });
-                if (!rw) continue;
-                string preinit_dir = resolve_preinit_dir(info.target.data());
-                xmkdir(preinit_dir.data(), 0700);
-                xmkdirs(path, 0755);
-                mounted = xmount(preinit_dir.data(), path, nullptr, MS_BIND, nullptr) == 0;
-                if (mounted) {
-                    break;
-                }
-            }
-        }
-        if (!mounted) {
-            LOGW("preinit mirror not mounted %u:%u\n", major(preinit_dev), minor(preinit_dev));
-            unlink(dev_path);
-        }
-    }
-
-    // Prepare worker
-    ssprintf(path, sizeof(path), "%s/" WORKERDIR, get_magisk_tmp());
-    xmkdir(path, 0);
-    xmount(path, path, nullptr, MS_BIND, nullptr);
-    xmount(nullptr, path, nullptr, MS_PRIVATE, nullptr);
-}
-
-string find_preinit_device() {
-    enum part_t {
-        UNKNOWN,
-        PERSIST,
-        METADATA,
-        CACHE,
-        DATA,
-    };
-
-    part_t ext4_type = UNKNOWN;
-    part_t f2fs_type = UNKNOWN;
-
-    bool encrypted = get_prop("ro.crypto.state") == "encrypted";
-    bool mount = getuid() == 0 && getenv("MAGISKTMP");
-    bool make_dev = mount && getenv("MAKEDEV");
-
-    string preinit_source;
-    string preinit_dir;
-    dev_t preinit_dev;
-
-    for (const auto &info: parse_mount_info("self")) {
-        if (info.target.ends_with(PREINITMIRR))
-            return basename(info.source.data());
-        if (info.root != "/" || info.source[0] != '/' || info.source.find("/dm-") != string::npos)
-            continue;
-        // Skip all non ext4 partitions once we found a matching ext4 partition
-        if (ext4_type != UNKNOWN && info.type != "ext4")
-            continue;
-        if (info.type != "ext4" && info.type != "f2fs")
-            continue;
-        auto flags = split_view(info.fs_option, ",");
-        auto rw = std::any_of(flags.begin(), flags.end(), [](const auto &flag) {
-            return flag == "rw"sv;
-        });
-        if (!rw) continue;
-        if (auto base = std::string_view(info.source).substr(0, info.source.find_last_of('/'));
-            !base.ends_with("/by-name") && !base.ends_with("/block")) {
-            continue;
-        }
-
-        part_t &matched = (info.type == "f2fs") ? f2fs_type : ext4_type;
-        switch (matched) {
-            case UNKNOWN:
-                if (info.target == "/persist" || info.target == "/mnt/vendor/persist") {
-                    matched = PERSIST;
-                    break;
-                }
-                [[fallthrough]];
-            case PERSIST:
-                if (info.target == "/metadata") {
-                    matched = METADATA;
-                    break;
-                }
-                [[fallthrough]];
-            case METADATA:
-                if (info.target == "/cache") {
-                    matched = CACHE;
-                    break;
-                }
-                [[fallthrough]];
-            case CACHE:
-                if (info.target == "/data") {
-                    if (!encrypted || access("/data/unencrypted", F_OK) == 0) {
-                        matched = DATA;
-                        break;
-                    }
-                }
-                [[fallthrough]];
-            default:
-                continue;
-        }
-
-        if (mount) {
-            preinit_dir = resolve_preinit_dir(info.target.data());
-            preinit_dev = info.device;
-        }
-        preinit_source = info.source;
-
-        // Cannot find any better partition, stop finding
-        if (ext4_type == DATA)
-            break;
-    }
-
-    if (preinit_source.empty())
-        return "";
-
-    if (!preinit_dir.empty()) {
-        auto mirror_dir = string(getenv("MAGISKTMP")) + "/" PREINITMIRR;
-        mkdirs(preinit_dir.data(), 0700);
-        mkdirs(mirror_dir.data(), 0700);
-        xmount(preinit_dir.data(), mirror_dir.data(), nullptr, MS_BIND, nullptr);
-        if (make_dev) {
-            auto dev_path = string(getenv("MAGISKTMP")) + "/" PREINITDEV;
-            xmknod(dev_path.data(), S_IFBLK | 0600, preinit_dev);
-        }
-    }
-    return basename(preinit_source.data());
-}
 
 static bool magisk_env() {
     char buf[4096];

native/src/core/include/core.hpp

@@ -42,7 +42,6 @@ extern std::string native_bridge;
 
 void reset_zygisk(bool restore);
 int connect_daemon(int req, bool create = false);
-std::string find_preinit_device();
 void unlock_blocks();
 
 // Poll control

native/src/core/include/daemon.hpp

@@ -26,4 +26,9 @@ private:
 };
 
 const char *get_magisk_tmp();
+
+// Rust bindings
 static inline rust::Utf8CStr get_magisk_tmp_rs() { return get_magisk_tmp(); }
+static inline rust::String resolve_preinit_dir_rs(rust::Utf8CStr base_dir) {
+    return resolve_preinit_dir(base_dir.c_str());
+}

native/src/core/lib.rs

@@ -1,4 +1,5 @@
 #![feature(format_args_nl)]
+#![feature(try_blocks)]
 #![allow(clippy::missing_safety_doc)]
 
 use base::Utf8CStr;
@@ -7,6 +8,7 @@ use daemon::{daemon_entry, find_apk_path, get_magiskd, MagiskD};
 use logging::{
     android_logging, magisk_logging, zygisk_close_logd, zygisk_get_logd, zygisk_logging,
 };
+use mount::{find_preinit_device, setup_mounts};
 use resetprop::{persist_delete_prop, persist_get_prop, persist_get_props, persist_set_prop};
 
 mod cert;
@@ -14,6 +16,7 @@ mod cert;
 mod consts;
 mod daemon;
 mod logging;
+mod mount;
 mod resetprop;
 
 #[cxx::bridge]
@@ -66,6 +69,8 @@ pub mod ffi {
 
         #[cxx_name = "get_magisk_tmp_rs"]
         fn get_magisk_tmp() -> Utf8CStrRef<'static>;
+        #[cxx_name = "resolve_preinit_dir_rs"]
+        fn resolve_preinit_dir(base_dir: Utf8CStrRef) -> String;
 
         #[cxx_name = "MagiskD"]
         type CxxMagiskD;
@@ -83,6 +88,8 @@ pub mod ffi {
         fn zygisk_get_logd() -> i32;
         fn find_apk_path(pkg: Utf8CStrRef, data: &mut [u8]) -> usize;
         fn read_certificate(fd: i32, version: i32) -> Vec<u8>;
+        fn setup_mounts();
+        fn find_preinit_device() -> String;
         unsafe fn persist_get_prop(name: Utf8CStrRef, prop_cb: Pin<&mut PropCb>);
         unsafe fn persist_get_props(prop_cb: Pin<&mut PropCb>);
         unsafe fn persist_delete_prop(name: Utf8CStrRef) -> bool;

native/src/core/logging.rs

@@ -9,7 +9,6 @@ use std::sync::atomic::{AtomicI32, Ordering};
 use std::{fs, io};
 
 use bytemuck::{bytes_of, bytes_of_mut, write_zeroes, Pod, Zeroable};
-use const_format::concatcp;
 use num_derive::{FromPrimitive, ToPrimitive};
 use num_traits::FromPrimitive;
 
@@ -19,8 +18,8 @@ use base::libc::{
     SIG_SETMASK,
 };
 use base::{
-    exit_on_error, libc, raw_cstr, FsPathBuf, LogLevel, Logger, Utf8CStr, Utf8CStrBuf,
-    Utf8CStrBufArr, Utf8CStrWrite, LOGGER,
+    const_format::concatcp, exit_on_error, libc, raw_cstr, FsPathBuf, LogLevel, Logger, Utf8CStr,
+    Utf8CStrBuf, Utf8CStrBufArr, Utf8CStrWrite, LOGGER,
 };
 
 use crate::consts::{LOGFILE, LOG_PIPE};

native/src/core/magisk.cpp

@@ -137,9 +137,8 @@ int magisk_main(int argc, char *argv[]) {
         install_module(argv[2]);
     } else if (argv[1] == "--preinit-device"sv) {
         auto name = find_preinit_device();
-        LOGD("preinit device: %s\n", name.data());
         if (!name.empty())  {
-            printf("%s\n", name.data());
+            printf("%s\n", name.c_str());
             return 0;
         }
         return 1;

native/src/core/mount.rs

@@ -0,0 +1,276 @@
+use std::path::Path;
+use std::ptr;
+
+use num_traits::AsPrimitive;
+
+use base::libc::{c_uint, dev_t};
+use base::{
+    cstr, debug, info, libc, parse_mount_info, raw_cstr, warn, FsPath, FsPathBuf, LibcReturn,
+    LoggedResult, ResultExt, Utf8CStr, Utf8CStrBufArr,
+};
+
+use crate::consts::{MODULEMNT, MODULEROOT, PREINITDEV, PREINITMIRR, WORKERDIR};
+use crate::ffi::{get_magisk_tmp, resolve_preinit_dir};
+use crate::get_prop;
+
+pub fn setup_mounts() {
+    info!("* Setup internal mounts");
+
+    let magisk_tmp = get_magisk_tmp();
+    let mut buf = Utf8CStrBufArr::default();
+
+    // Mount preinit directory
+    let mut dev_buf = Utf8CStrBufArr::<64>::new();
+    let dev_path = FsPathBuf::new(&mut dev_buf)
+        .join(magisk_tmp)
+        .join(PREINITDEV);
+    if let Ok(attr) = dev_path.get_attr() {
+        if attr.st.st_mode & libc::S_IFMT as c_uint == libc::S_IFBLK.as_() {
+            // DO NOT mount the block device directly, as we do not know the flags and configs
+            // to properly mount the partition; mounting block devices directly as rw could cause
+            // crashes if the filesystem driver is crap (e.g. some broken F2FS drivers).
+            // What we do instead is to scan through the current mountinfo and find a pre-existing
+            // mount point mounting our desired partition, and then bind mount the target folder.
+            let preinit_dev = attr.st.st_rdev;
+            let mnt_path = FsPathBuf::new(&mut buf).join(magisk_tmp).join(PREINITMIRR);
+            let mut mounted = false;
+            for info in parse_mount_info("self") {
+                if info.root == "/" && info.device == preinit_dev {
+                    if !info.fs_option.split(',').any(|s| s == "rw") {
+                        // Only care about rw mounts
+                        continue;
+                    }
+                    let mut target = info.target;
+                    let target = Utf8CStr::from_string(&mut target);
+                    let mut preinit_dir = resolve_preinit_dir(target);
+                    let preinit_dir = Utf8CStr::from_string(&mut preinit_dir);
+                    let r: LoggedResult<()> = try {
+                        FsPath::from(preinit_dir).mkdir(0o700)?;
+                        mnt_path.mkdirs(0o755)?;
+                        unsafe {
+                            libc::mount(
+                                preinit_dir.as_ptr(),
+                                mnt_path.as_ptr(),
+                                ptr::null(),
+                                libc::MS_BIND,
+                                ptr::null(),
+                            )
+                            .as_os_err()?
+                        }
+                    };
+                    if r.is_ok() {
+                        mounted = true;
+                        break;
+                    }
+                }
+            }
+            if !mounted {
+                warn!("mount: preinit mirror not mounted");
+                dev_path.remove().ok();
+            } else {
+                debug!("mount: preinit mirror mounted");
+            }
+        }
+    }
+
+    // Bind remount module root to clear nosuid
+    let module_mnt = FsPathBuf::new(&mut buf).join(magisk_tmp).join(MODULEMNT);
+    let _: LoggedResult<()> = try {
+        module_mnt.mkdir(0o755)?;
+        unsafe {
+            libc::mount(
+                raw_cstr!(MODULEROOT),
+                module_mnt.as_ptr(),
+                ptr::null(),
+                libc::MS_BIND,
+                ptr::null(),
+            )
+            .as_os_err()?;
+            libc::mount(
+                ptr::null(),
+                module_mnt.as_ptr(),
+                ptr::null(),
+                libc::MS_REMOUNT | libc::MS_BIND | libc::MS_RDONLY,
+                ptr::null(),
+            )
+            .as_os_err()?;
+            libc::mount(
+                ptr::null(),
+                module_mnt.as_ptr(),
+                ptr::null(),
+                libc::MS_PRIVATE,
+                ptr::null(),
+            )
+            .as_os_err()?;
+        }
+    };
+
+    // Prepare worker
+    let worker_dir = FsPathBuf::new(&mut buf).join(magisk_tmp).join(WORKERDIR);
+    let _: LoggedResult<()> = try {
+        worker_dir.mkdir(0)?;
+        unsafe {
+            libc::mount(
+                worker_dir.as_ptr(),
+                worker_dir.as_ptr(),
+                ptr::null(),
+                libc::MS_BIND,
+                ptr::null(),
+            )
+            .as_os_err()?;
+            libc::mount(
+                ptr::null(),
+                worker_dir.as_ptr(),
+                ptr::null(),
+                libc::MS_PRIVATE,
+                ptr::null(),
+            )
+            .as_os_err()?;
+        }
+    };
+}
+
+#[derive(Ord, PartialOrd, Eq, PartialEq)]
+enum PartId {
+    Unknown,
+    Persist,
+    Metadata,
+    Cache,
+    Data,
+}
+
+pub fn find_preinit_device() -> String {
+    let encrypted = get_prop(cstr!("ro.crypto.state"), false) == "encrypted";
+    let mount = unsafe { libc::getuid() } == 0 && std::env::var("MAGISKTMP").is_ok();
+    let make_dev = mount && std::env::var_os("MAKEDEV").is_some();
+
+    let mut ext4_type = PartId::Unknown;
+    let mut f2fs_type = PartId::Unknown;
+
+    let mut preinit_source: String = String::new();
+    let mut preinit_dir: String = String::new();
+    let mut preinit_dev: u64 = 0;
+
+    'info_loop: for info in parse_mount_info("self") {
+        if info.target.ends_with(PREINITMIRR) {
+            return Path::new(&info.source)
+                .file_name()
+                .unwrap()
+                .to_str()
+                .unwrap()
+                .to_string();
+        }
+        if info.root != "/" || !info.source.starts_with('/') || info.source.contains("/dm-") {
+            continue;
+        }
+        if ext4_type != PartId::Unknown && info.fs_type != "ext4" {
+            // Skip all non ext4 partitions once we found a matching ext4 partition
+            continue;
+        }
+        if info.fs_type != "ext4" && info.fs_type != "f2fs" {
+            // Only care about ext4 and f2fs filesystems
+            continue;
+        }
+        if !info.fs_option.split(',').any(|s| s == "rw") {
+            // Only care about rw mounts
+            continue;
+        }
+        if let Some(path) = Path::new(&info.source).parent() {
+            if !path.ends_with("by-name") && !path.ends_with("block") {
+                continue;
+            }
+        } else {
+            continue;
+        }
+
+        let matched_type = if info.fs_type == "f2fs" {
+            &mut f2fs_type
+        } else {
+            &mut ext4_type
+        };
+
+        'block: {
+            if *matched_type <= PartId::Unknown
+                && (info.target == "/persist" || info.target == "/mnt/vendor/persist")
+            {
+                *matched_type = PartId::Persist;
+                break 'block;
+            }
+            if *matched_type <= PartId::Persist && info.target == "/metadata" {
+                *matched_type = PartId::Metadata;
+                break 'block;
+            }
+            if *matched_type <= PartId::Metadata && info.target == "/cache" {
+                *matched_type = PartId::Cache;
+                break 'block;
+            }
+            if *matched_type <= PartId::Cache
+                && info.target == "/data"
+                && (!encrypted || FsPath::from(cstr!("/data/unencrypted")).exists())
+            {
+                *matched_type = PartId::Data;
+            }
+
+            // No matches, continue through the loop
+            continue 'info_loop;
+        }
+
+        if mount {
+            let mut target = info.target;
+            preinit_dir = resolve_preinit_dir(Utf8CStr::from_string(&mut target));
+            preinit_dev = info.device;
+        }
+        preinit_source = info.source;
+
+        // Cannot find any better partition, stop finding
+        if ext4_type == PartId::Data {
+            break;
+        }
+    }
+
+    if preinit_source.is_empty() {
+        return String::new();
+    }
+
+    if !preinit_dir.is_empty() {
+        if let Ok(tmp) = std::env::var("MAGISKTMP") {
+            let mut buf = Utf8CStrBufArr::default();
+            let mirror_dir = FsPathBuf::new(&mut buf).join(&tmp).join(PREINITMIRR);
+            let preinit_dir = FsPath::from(Utf8CStr::from_string(&mut preinit_dir));
+            let _: LoggedResult<()> = try {
+                preinit_dir.mkdirs(0o700)?;
+                mirror_dir.mkdirs(0o700)?;
+                unsafe {
+                    libc::mount(
+                        preinit_dir.as_ptr(),
+                        mirror_dir.as_ptr(),
+                        ptr::null(),
+                        libc::MS_BIND,
+                        ptr::null(),
+                    )
+                    .as_os_err()?;
+                }
+            };
+            if make_dev {
+                let dev_path = FsPathBuf::new(&mut buf).join(&tmp).join(PREINITDEV);
+                unsafe {
+                    libc::mknod(
+                        dev_path.as_ptr(),
+                        libc::S_IFBLK | 0o600,
+                        preinit_dev as dev_t,
+                    )
+                    .as_os_err()
+                    .log()
+                    .ok();
+                }
+            }
+        }
+    }
+
+    Path::new(&preinit_source)
+        .file_name()
+        .unwrap()
+        .to_str()
+        .unwrap()
+        .to_string()
+}

native/src/include/consts.rs

@@ -1,6 +1,17 @@
-use const_format::concatcp;
+use base::const_format::concatcp;
 
 pub const LOGFILE: &str = "/cache/magisk.log";
-pub const INTLROOT: &str = ".magisk";
-pub const LOG_PIPE: &str = concatcp!(INTLROOT, "/device/log");
-pub const MAIN_CONFIG: &str = concatcp!(INTLROOT, "/config");
+
+// data paths
+const SECURE_DIR: &str = "/data/adb";
+pub const MODULEROOT: &str = concatcp!(SECURE_DIR, "modules");
+
+// tmpfs paths
+const INTERNAL_DIR: &str = ".magisk";
+pub const LOG_PIPE: &str = concatcp!(INTERNAL_DIR, "/device/log");
+pub const MAIN_CONFIG: &str = concatcp!(INTERNAL_DIR, "/config");
+pub const PREINITMIRR: &str = concatcp!(INTERNAL_DIR, "/preinit");
+pub const MODULEMNT: &str = concatcp!(INTERNAL_DIR, "/modules");
+pub const WORKERDIR: &str = concatcp!(INTERNAL_DIR, "/worker");
+pub const DEVICEDIR: &str = concatcp!(INTERNAL_DIR, "/device");
+pub const PREINITDEV: &str = concatcp!(DEVICEDIR, "/preinit");