InMemoryDexClassLoader path does not work on pie or earlier

[nift4]

Hi,

thanks for this library :) I've been using this in my music player app to access some hidden APIs in libmedia.so / libaudioclient.so - however, while testing on emulators, I noticed that version 0.1.1 only works on Android Q or later, on P for example it only prints following message to logcat: cannot find class lab/galaxy/dlfunc/JNIHelper I found that 0.1.0 works fine on older Android versions, however the change to InMemoryDexClassLoader codepath obviously was done to fix a bug. So I was thinking, is it fine to just use older codepath from version 0.1.0 before Q based on checking sdk level at runtime or will I run into problems? Or maybe you have any tips related to why 0.1.1 doesn't work on Nougat to Pie versions?

Thanks, Nick

[nift4]

I implemented that idea in my fork for now: https://github.com/nift4/dlfunc/blob/ede150fda4915366226e361bd4c916e22383dc80/dlfunc/src/main/jni/dlfunc.c#L102

[shuajinanhai]

不知道为什么，原版dlfunc测试5.1系统，7系统，15系统全部正常，但有台11系统dlfunc_dlopen和dlfunc_dlsym获取到的全都为null

[nift4]

@shuajinanhai it works for me on Android 11 emulator

[shuajinanhai]

在11系统上 dlfunc_init(env); void* handle6 = dlfunc_dlopen(env, "/apex/com.android.runtime/lib64/bionic/libc.so", RTLD_LAZY); LOGE("dlfunc handle=%p", handle6); void* addr6 = dlfunc_dlsym(env, handle6, "open"); LOGE("dlfunc sym=%p", addr6); 这个没问题 dlfunc handle=0x9a66bdbb06dd0339 dlfunc sym=0x740ca3375b40

dlfunc_init(env);
void* dlfunc_handle = dlfunc_dlopen(env, "libart.so", RTLD_LAZY);
LOGE("dlfunc handle=%p", dlfunc_handle);
void* dlfunc_sym = dlfunc_dlsym(env, dlfunc_handle, "_ZN3art11ClassLinker40MakeInitializedClassesVisiblyInitializedEPNS_6ThreadEb");
LOGE("dlfunc sym=%p", dlfunc_sym);

dlfunc handle=0x0 dlfunc sym=0x0

对比其他几个，比如shadowhook ，fake_dlopen都是没问题

[nift4]

@shuajinanhai maybe the library you are trying to load is outside art namespace, on new android version (since Android 8) I use dlfunc to get access to ld-android.so and then use that to create unrestricted namespace, it's based on a method by Billy Laws but works on non-arm64: https://github.com/AkaneTan/Gramophone/blob/214ee60fe0690ed634cd9ac6a5b763194cdf8782/app/src/main/cpp/android_linker_ns.cpp