ac1b37421d
This line appears to be trying to undo the effect of adding 4 to pc above, but does so incorrectly and so ends up returning with next_pc earlier than it was prior to decoding. This causes the translator to malfunction because it does not expect pc_next to decrease during decoding: this is effectively reporting that the invalid construction has a negative size, which is impossible. The decoder uses the increase in next_pc to decide the translation block size, but converts it to uint16_t thereby causing a block containing _only_ an invalid instruction to be treated as having size 65532 (reinterpreted -4) and therefore the translation loop tries to find the next translation block at 65532 bytes after the invalid instruction, which can cause a spurious instruction access/page fault if the page containing that address is not mapped as executable. In practice we don't need to readjust the pc at all here because it is correct to report that the invalid instruction is four bytes long. This allows the translation loop to correctly find the next instruction, and to avoid producing spurious TLB fills that might cause incorrect exceptions.
Unicorn Engine
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, Lua and Zig.
- Native support for Windows & *nix (with Mac OSX, Linux, Android, *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
License
This project is released under the GPL license.
Compilation & Docs
See docs/COMPILE.md file for how to compile and install Unicorn.
More documentation is available in docs/README.md.
Contact
Contact us via mailing list, email or twitter for any questions.
Contribute
If you want to contribute, please pick up something from our Github issues.
We also maintain a list of more challenged problems in milestones for our regular release.
CREDITS.TXT records important contributors of our project.