add: base for C99 zygiskd

This commit adds the first base for C99 zygiskd, that is not fully working or code-ready.

zygiskd/src/dl.rs

@@ -0,0 +1,85 @@
+use anyhow::{bail, Result};
+use std::ffi::{c_char, c_void};
+
+pub const ANDROID_NAMESPACE_TYPE_SHARED: u64 = 0x2;
+pub const ANDROID_DLEXT_USE_NAMESPACE: u64 = 0x200;
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct AndroidNamespace {
+    _unused: [u8; 0],
+}
+
+#[repr(C)]
+pub struct AndroidDlextinfo {
+    pub flags: u64,
+    pub reserved_addr: *mut c_void,
+    pub reserved_size: libc::size_t,
+    pub relro_fd: libc::c_int,
+    pub library_fd: libc::c_int,
+    pub library_fd_offset: libc::off64_t,
+    pub library_namespace: *mut AndroidNamespace,
+}
+
+extern "C" {
+    pub fn android_dlopen_ext(
+        filename: *const c_char,
+        flags: libc::c_int,
+        extinfo: *const AndroidDlextinfo,
+    ) -> *mut c_void;
+}
+
+type AndroidCreateNamespaceFn = unsafe extern "C" fn(
+    *const c_char,         // name
+    *const c_char,         // ld_library_path
+    *const c_char,         // default_library_path
+    u64,                   // type
+    *const c_char,         // permitted_when_isolated_path
+    *mut AndroidNamespace, // parent
+    *const c_void,         // caller_addr
+) -> *mut AndroidNamespace;
+
+pub unsafe fn dlopen(path: &str, flags: i32) -> Result<*mut c_void> {
+    let filename = std::ffi::CString::new(path)?;
+    let filename = filename.as_ptr() as *mut _;
+    let dir = libc::dirname(filename);
+    let mut info = AndroidDlextinfo {
+        flags: 0,
+        reserved_addr: std::ptr::null_mut(),
+        reserved_size: 0,
+        relro_fd: 0,
+        library_fd: 0,
+        library_fd_offset: 0,
+        library_namespace: std::ptr::null_mut(),
+    };
+
+    let android_create_namespace_fn = libc::dlsym(
+        libc::RTLD_DEFAULT,
+        std::ffi::CString::new("__loader_android_create_namespace")?.as_ptr(),
+    );
+    let android_create_namespace_fn: AndroidCreateNamespaceFn =
+        std::mem::transmute(android_create_namespace_fn);
+    let ns = android_create_namespace_fn(
+        filename,
+        dir,
+        std::ptr::null(),
+        ANDROID_NAMESPACE_TYPE_SHARED,
+        std::ptr::null(),
+        std::ptr::null_mut(),
+        &dlopen as *const _ as *const c_void,
+    );
+    if ns != std::ptr::null_mut() {
+        info.flags = ANDROID_DLEXT_USE_NAMESPACE;
+        info.library_namespace = ns;
+        log::debug!("Open {} with namespace {:p}", path, ns);
+    } else {
+        log::debug!("Cannot create namespace for {}", path);
+    };
+
+    let result = android_dlopen_ext(filename, flags, &info);
+    if result.is_null() {
+        let e = std::ffi::CStr::from_ptr(libc::dlerror()).to_string_lossy();
+        bail!(e);
+    }
+    Ok(result)
+}