The root cause of the previous su-c requirement was that Qualcomm's FastRPC
kernel driver rejects processes spawned via ProcessBuilder fork+exec because
they lose supplementary GIDs on exec. Zygote-forked app processes retain the
proper init-configured credentials and are accepted by the adsprpcd service,
which is why ORT-QNN (Whisper, in-process) worked while the subprocess
qnn_llama_runner did not. Running the LLM in-process via ExecuTorch's
LlmModule bypasses the fork+exec path entirely.
What this commit does:
- ExecuTorchLlmEngine now uses org.pytorch.executorch.extension.llm.LlmModule
with MODEL_TYPE_QNN_LLAMA=4 (routes to example::Runner in jni_layer_llama.cpp,
the same C++ runner that qnn_llama_runner embeds).
- All su, ProcessBuilder, file-based prompt/response plumbing, and run_llm.sh
gone. ChatML template is built in Kotlin; tokens stream in via LlmCallback.
Supporting changes under executorch-patches/llm_in_process_jni.patch:
1. backends/qualcomm/CMakeLists.txt — gate PyQnnManagerAdaptor on NOT ANDROID.
The original guard (CMAKE_SYSTEM_PROCESSOR MATCHES x86_64) misfires in a
nested scope during Android cross-compile and tried to build the host
Python bindings.
2. extension/android/jni/jni_layer_llama.cpp — hardcode decoder_model="qwen3"
(was "llama3") and pass eval_mode=0 (EvalMode::kKVCached) + shared_buffer=true
to match our hybrid_llama_qnn.pte which only contains kv_forward, not
prefill_forward.
Build: scripts/build_android_library.sh arm64-v8a with QNN_SDK_ROOT pointing
to /opt/Kazeia/qnn_sdk_242/qairt/2.42.0.251225 and EXECUTORCH_BUILD_QNN=ON.
Produces libexecutorch_jni.so (192 MB) with QNN v2.42 backend + the llama
runner code, plus libqnn_executorch_backend.so. Both staged in jniLibs.
Validated on OnePlus Pad 3: LlmModule.load() completes in 4.2 s, no su
prompts, Pipeline ready with STT(WhisperHybridEngine) → [VoiceCommands →
LLM] → TTS(Qwen3TtsEngine). TTS .pte still loads with the upgraded v2.42
runtime — no regression.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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