frida-gum: force frida-gum init to use Module (frida#98)

In order to use the underlying C API global init should be called.

We hence force the creation of Gum to use Module::* functions.

We also use OnceLock instead of lazy_static! as discussed in the issue.

examples/gum/debug_symbol/src/main.rs

@@ -1,15 +1,14 @@
 use frida_gum::DebugSymbol;
 use frida_gum::{Gum, Module};
-use lazy_static::lazy_static;
-
-lazy_static! {
-    static ref GUM: Gum = unsafe { Gum::obtain() };
-}
+use std::iter::Once;
+use std::sync::OnceLock;
 
 fn main() {
-    lazy_static::initialize(&GUM);
+    static CELL: OnceLock<Gum> = OnceLock::new();
+    let gum = CELL.get_or_init(|| Gum::obtain());
 
-    let symbol = Module::find_export_by_name(None, "mmap").unwrap();
+    let module = Module::from_gum(gum);
+    let symbol = module.find_export_by_name(None, "mmap").unwrap();
     let symbol_details = DebugSymbol::from_address(symbol).unwrap();
     println!(
         "address={:#x?} module_name={:?} symbol_name={:?} file_name={:?} line_number={:?}",

examples/gum/hook_instruction/Cargo.toml

@@ -11,5 +11,4 @@ crate-type = ["cdylib"]
 
 [dependencies]
 frida-gum = { path = "../../../frida-gum", features = ["invocation-listener"] }
-lazy_static = "1.4"
 ctor = "0.2"

examples/gum/hook_instruction/src/lib.rs

@@ -3,11 +3,7 @@ use frida_gum::{
     interceptor::{Interceptor, InvocationContext, ProbeListener},
     Gum, Module,
 };
-use lazy_static::lazy_static;
-
-lazy_static! {
-    static ref GUM: Gum = unsafe { Gum::obtain() };
-}
+use std::sync::OnceLock;
 #[derive(Default, Debug)]
 struct OpenProbeListener;
 
@@ -19,8 +15,11 @@ impl ProbeListener for OpenProbeListener {
 
 #[ctor]
 fn init() {
-    let mut interceptor = Interceptor::obtain(&GUM);
-    let open = Module::find_export_by_name(None, "open").unwrap();
+    static CELL: OnceLock<Gum> = OnceLock::new();
+    let gum = CELL.get_or_init(|| Gum::obtain());
+    let mut interceptor = Interceptor::obtain(gum);
+    let module = Module::from_gum(gum);
+    let open = module.find_export_by_name(None, "open").unwrap();
     let mut listener = OpenProbeListener;
     interceptor.attach_instruction(open, &mut listener).unwrap();
 }

examples/gum/hook_open/src/lib.rs

@@ -4,9 +4,9 @@ use lazy_static::lazy_static;
 use libc::{c_char, c_int, c_void};
 use std::cell::UnsafeCell;
 use std::sync::Mutex;
+use std::sync::OnceLock;
 
 lazy_static! {
-    static ref GUM: Gum = unsafe { Gum::obtain() };
     static ref ORIGINAL_OPEN: Mutex<UnsafeCell<Option<OpenFunc>>> =
         Mutex::new(UnsafeCell::new(None));
 }
@@ -29,8 +29,11 @@ unsafe extern "C" fn open_detour(name: *const c_char, flags: c_int) -> c_int {
 
 #[ctor]
 fn init() {
-    let mut interceptor = Interceptor::obtain(&GUM);
-    let open = Module::find_export_by_name(None, "open").unwrap();
+    static CELL: OnceLock<Gum> = OnceLock::new();
+    let gum = CELL.get_or_init(|| Gum::obtain());
+    let module = Module::from_gum(gum);
+    let mut interceptor = Interceptor::obtain(gum);
+    let open = module.find_export_by_name(None, "open").unwrap();
     unsafe {
         *ORIGINAL_OPEN.lock().unwrap().get_mut() = Some(std::mem::transmute::<
             *mut libc::c_void,

examples/gum/open/Cargo.toml

@@ -11,4 +11,3 @@ crate-type = ["cdylib"]
 
 [dependencies]
 frida-gum = { path = "../../../frida-gum", features = ["invocation-listener"] }
-lazy_static = "1.4"

examples/gum/open/src/lib.rs

@@ -5,12 +5,8 @@ use gum::{
     interceptor::{Interceptor, InvocationContext, InvocationListener},
     Gum, Module,
 };
-use lazy_static::lazy_static;
 use std::os::raw::{c_int, c_void};
-
-lazy_static! {
-    static ref GUM: Gum = unsafe { Gum::obtain() };
-}
+use std::sync::OnceLock;
 
 struct OpenListener;
 
@@ -28,17 +24,21 @@ impl InvocationListener for OpenListener {
 extern "C" fn example_agent_main(_user_data: *const c_void, resident: *mut c_int) {
     unsafe { *resident = 1 };
 
-    let mut interceptor = Interceptor::obtain(&GUM);
+    static CELL: OnceLock<Gum> = OnceLock::new();
+    let gum = CELL.get_or_init(|| Gum::obtain());
+
+    let mut interceptor = Interceptor::obtain(gum);
     let mut listener = OpenListener {};
 
-    let modules = Module::enumerate_modules();
+    let module = Module::from_gum(gum);
+    let modules = module.enumerate_modules();
     for module in modules {
         println!(
             "{}@{:#x}/{:#x}",
             module.name, module.base_address, module.size
         );
     }
 
-    let open = Module::find_export_by_name(None, "open").unwrap();
+    let open = module.find_export_by_name(None, "open").unwrap();
     interceptor.attach(open, &mut listener).unwrap();
 }

frida-gum/src/module.rs

@@ -14,7 +14,7 @@
 )]
 
 use {
-    crate::{NativePointer, PageProtection, RangeDetails},
+    crate::{Gum, NativePointer, PageProtection, RangeDetails},
     core::ffi::c_void,
     cstr_core::CString,
     frida_gum_sys as gum_sys,
@@ -56,12 +56,23 @@ pub struct ModuleDetailsOwned {
     pub size: usize,
 }
 
-pub struct Module;
+pub struct Module {
+    // This is to verify that Gum is initialized before using any Module methods which requires
+    // intialization.
+    // Note that Gum is expected to be initialized via OnceCell which provides &Gum for every
+    // instance.
+    _gum: &'static Gum,
+}
 
 impl Module {
+    pub fn from_gum(gum: &'static Gum) -> Module {
+        Module { _gum: gum }
+    }
+
     /// The absolute address of the export. In the event that no such export
     /// could be found, returns NULL.
     pub fn find_export_by_name(
+        self: &Self,
         module_name: Option<&str>,
         symbol_name: &str,
     ) -> Option<NativePointer> {
@@ -92,7 +103,11 @@ impl Module {
 
     /// The absolute address of the symbol. In the event that no such symbol
     /// could be found, returns NULL.
-    pub fn find_symbol_by_name(module_name: &str, symbol_name: &str) -> Option<NativePointer> {
+    pub fn find_symbol_by_name(
+        self: &Self,
+        module_name: &str,
+        symbol_name: &str,
+    ) -> Option<NativePointer> {
         let symbol_name = CString::new(symbol_name).unwrap();
 
         let module_name = CString::new(module_name).unwrap();
@@ -112,7 +127,7 @@ impl Module {
 
     /// Returns the base address of the specified module. In the event that no
     /// such module could be found, returns NULL.
-    pub fn find_base_address(module_name: &str) -> NativePointer {
+    pub fn find_base_address(self: &Self, module_name: &str) -> NativePointer {
         let module_name = CString::new(module_name).unwrap();
 
         unsafe {
@@ -124,6 +139,7 @@ impl Module {
 
     /// Enumerates memory ranges satisfying protection given.
     pub fn enumerate_ranges(
+        self: &Self,
         module_name: &str,
         prot: PageProtection,
         callout: impl FnMut(RangeDetails) -> bool,
@@ -147,7 +163,7 @@ impl Module {
     }
 
     /// Enumerates modules.
-    pub fn enumerate_modules() -> Vec<ModuleDetailsOwned> {
+    pub fn enumerate_modules(self: &Self) -> Vec<ModuleDetailsOwned> {
         let result: Vec<ModuleDetailsOwned> = vec![];
 
         unsafe extern "C" fn callback(
@@ -187,7 +203,7 @@ impl Module {
     }
 
     /// Enumerates exports in module.
-    pub fn enumerate_exports(module_name: &str) -> Vec<ExportDetails> {
+    pub fn enumerate_exports(self: &Self, module_name: &str) -> Vec<ExportDetails> {
         let result: Vec<ExportDetails> = vec![];
 
         unsafe extern "C" fn callback(
@@ -219,7 +235,7 @@ impl Module {
     }
 
     /// Enumerates symbols in module.
-    pub fn enumerate_symbols(module_name: &str) -> Vec<SymbolDetails> {
+    pub fn enumerate_symbols(self: &Self, module_name: &str) -> Vec<SymbolDetails> {
         let result: Vec<SymbolDetails> = vec![];
         unsafe extern "C" fn callback(
             details: *const GumSymbolDetails,