Use xHook to hook functions in PLT

native/jni/inject/hook.cpp

@@ -0,0 +1,70 @@
+#include <jni.h>
+
+#include <xhook.h>
+#include <utils.hpp>
+#include <flags.hpp>
+
+#include "inject.hpp"
+
+using namespace std;
+
+// Static vector won't work, use a pointer instead
+static vector<tuple<const char *, const char *, void **>> *hook_list;
+
+#define DEF_HOOK_FUNC(ret, func, ...) \
+    static ret (*old_##func)(__VA_ARGS__); \
+    static ret new_##func(__VA_ARGS__)
+
+DEF_HOOK_FUNC(int, jniRegisterNativeMethods,
+        JNIEnv *env, const char *className, const JNINativeMethod *methods, int numMethods) {
+    LOGD("hook: jniRegisterNativeMethods %s", className);
+
+    // TODO: actually do things like replacing JNI native methods
+
+    return old_jniRegisterNativeMethods(env, className, methods, numMethods);
+}
+
+static bool hook_refresh() {
+    if (xhook_refresh(0) == 0) {
+        xhook_clear();
+        LOGI("hook: xhook success\n");
+        return true;
+    } else {
+        LOGE("hook: xhook failed\n");
+        return false;
+    }
+}
+
+static int hook_register(const char *path, const char *symbol, void *new_func, void **old_func) {
+    int ret = xhook_register(path, symbol, new_func, old_func);
+    if (ret != 0) {
+        LOGE("hook: Failed to register hook \"%s\"\n", symbol);
+        return ret;
+    }
+    hook_list->emplace_back(path, symbol, old_func);
+    return 0;
+}
+
+#define XHOOK_REGISTER(PATH_REGEX, NAME) \
+    hook_register(PATH_REGEX, #NAME, (void*) new_##NAME, (void **) &old_##NAME)
+
+void hook_functions() {
+#ifdef MAGISK_DEBUG
+    xhook_enable_debug(1);
+    xhook_enable_sigsegv_protection(0);
+#endif
+    hook_list = new remove_pointer_t<decltype(hook_list)>();
+    XHOOK_REGISTER(".*\\libandroid_runtime.so$", jniRegisterNativeMethods);
+    hook_refresh();
+}
+
+bool unhook_functions() {
+    for (auto &[path, sym, old_func] : *hook_list) {
+        if (xhook_register(path, sym, *old_func, nullptr) != 0) {
+            LOGE("hook: Failed to register hook \"%s\"\n", sym); \
+            return false;
+        }
+    }
+    delete hook_list;
+    return hook_refresh();
+}