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Unlike some other architectures, RISC-V does not expose the current privilege mode in any architecturally-defined register. That is intentional to make it easier to implement virtualization in software, but a Unicorn caller operates outside of the emulated hart and so it can and should be able to observe and change the current privilege mode in order to properly emulate certain behaviors of a real CPU. The current privilege level is therefore now exposed as a new pseudo-register using the name "priv", which matches the name of the virtual register used by RISC-V's debug extension to allow the debugger to read and change the privilege mode while the hart is halted. Unicorn's use of it is conceptually similar to a debugger. The bit encoding of this register is the same as specified in RISC-V Debug Specification v1.0-rc3 Section 4.10.1. It's defined as a "virtual" register exposing a subset of fields from the dcsr register, although here it's implemented directly inside the Unicorn code because QEMU doesn't currently have explicit support for the CSRs from the debug specification. If it supports "dcsr" in a future release then this implementation could change to wrap reading and writing that CSR and then projecting the "prv" and "v" bitfields into the correct locations for the virtual register.
Unicorn
Unicorn is a lightweight, multi-platform, multi-architecture CPU emulator framework based on QEMU.
Unicorn offers some unparalleled features:
- Multi-architecture: ARM, ARM64 (ARMv8), M68K, MIPS, PowerPC, RISCV, SPARC, S390X, TriCore and X86 (16, 32, 64-bit)
- Clean/simple/lightweight/intuitive architecture-neutral API
- Implemented in pure C language, with bindings for Crystal, Clojure, Visual Basic, Perl, Rust, Ruby, Python, Java, .NET, Go, Delphi/Free Pascal, Haskell, Pharo, and Lua.
- Native support for Windows & *nix (with Mac OSX, Linux, *BSD & Solaris confirmed)
- High performance via Just-In-Time compilation
- Support for fine-grained instrumentation at various levels
- Thread-safety by design
- Distributed under free software license GPLv2
Further information is available at http://www.unicorn-engine.org
Python Bindings for Unicorn
Originally written by Nguyen Anh Quynh, polished and redesigned by elicn, maintained by all community contributors.
Install
Install a prebuilt wheel from PyPI:
pip3 install unicorn
In case you would like to develop the bindings:
# Python3
DEBUG=1 THREADS=4 pip3 install --user -e .
# Workaround for Pylance
DEBUG=1 THREADS=4 pip3 install --user -e . --config-settings editable_mode=strict
# Python2
DEBUG=1 THREADS=4 pip install -e .
or install it by building it by yourself:
# Python3
THREADS=4 pip3 install --user .
# Python2, unfortunately `pip2` doesn't support in-tree build
THREADS=4 python3 setup.py install
Explanations for arguments:
THREADS=4will use 4 threads for building.DEBUG=1will build debug version of unicorn.--userwill install the bindings to your user directory instead of requiring root permission.-einfers the editable mode, which gives your instant feedback instead of re-compiling every time.
Note that you should setup a valid building environment according to docs/COMPILE.md but not necessarily build it because setup.py will do this for you.
Python2 compatibility
By default, Unicorn python bindings will be maintained against Python3 as it offers more powerful features which improves developing efficiency. Meanwhile, Unicorn will only keep compatible with all features Unicorn1 offers regarding Python2 because Python2 has reached end-of-life for more than 3 years as the time of writing this README. While offering all features for both Python2 & Python3 is desirable and doable, it inevitably costs too much efforts to maintain and few users really rely on this. Therefore, we assume that if users still stick to Python2, previous Unicorn1 features we offer should be enough. If you really want some new features Unicorn2 offers, please check and pull request to `unicorn/unicorn_py2``. We are happy to review and accept!