rv8

RISC-V simulator for x86-64

rv8 is a RISC-V simulation suite comprising a high performance x86-64 binary translator, a user mode simulator, a full system emulator, an ELF binary analysis tool and ISA metadata:

• rv-jit - user mode x86-64 binary translator
• rv-sim - user mode system call proxy simulator
• rv-sys - full system emulator with soft MMU
• rv-bin - ELF disassembler and histogram tool
• rv-meta - code and documentation generator

The rv8 simulator suite contains libraries and command line tools for creating instruction opcode maps, C headers and source containing instruction set metadata, instruction decoders, a JIT assembler, LaTeX documentation, a metadata based RISC-V disassembler, a histogram tool for generating statistics on RISC-V ELF executables, a RISC-V proxy syscall simulator, a RISC-V full system emulator that implements the RISC-V 1.9.1 privileged specification and an x86-64 binary translator.

RISC-V to x86-64 binary translator

The rv8 binary translation engine works by interpreting code while profiling it for hot paths. Hot paths are translated on the fly to native code. The translation engine maintains a call stack to allow runtime inlining of hot functions. A jump target cache is used to accelerate returns and indirect calls through function pointers. The translator supports hybrid binary translation and interpretation to handle instructions that do not have native translations. Currently ‘IM’ code is translated and ‘AFD’ is interpreted. The translator supports RVC compressed code.

The rv8 binary translator supports a number of simple optimisations:

• Hybrid interpretation and compilation of hot code paths
• Incremental translation with dynamic trace linking
• Inline caching of function calls in hot code paths
• L1 jump target cache for indirect calls and returns
• Macro-op fusion for common RISC-V instruction sequences

RISC-V full system emulator

The rv8 suite includes a full system emulator that implements the RISC-V privileged ISA with support for interrupts, MMIO (memory mapped input output) devices, a soft MMU (memory management unit) with separate instruction and data TLBs (translation lookaside buffers). The full system emulator has a simple integrated debugger that allows setting breakpoints, single stepping and disassembling instructions as they are executed.

The rv8 full system emulator has the following features:

• RISC-V IMAFD Base plus Privileged ISA (riscv32 and riscv64)
• Simple integrated debug command line interface
• Histograms (registers, instruction and program counter frequency)
• Soft MMU supporting sv32, sv39, sv48 page translation modes
• Abstract MMIO device interface for device emulation
• Extensible interpreter generated from ISA metadata
• Protected address space

RISC-V user mode simulator

The rv8 user mode simulator is a single address space implementation of the RISC-V ISA that implements a subset of the RISC-V Linux syscall ABI (application binary interface) and delegates system calls to the underlying native host operating system. The user mode simulator can run RISC-V Linux binaries on non-Linux operating systems via system call emulation. The current user mode simulator implements a small number of system calls to allow running RISC-V Linux ELF static binaries.

The rv8 user mode simulator has the following features:

• RISC-V IMAFD Base ISA (riscv32 and riscv64)
• Simple integrated debug command line interface
• A small set of emulated Linux system calls for simple file IO
• Extensible interpreter generated from ISA metadata
• Instruction logging mode for tracing program execution
• Shared address space
  • 0x000000000000 - 0x000000000fff (zero)
  • 0x000000001000 - 0x7ffdffffffff (guest)
  • 0x7ffe00000000 - 0x7fffffffffff (host)

Project Goals

The future goals of the rv8 project are:

• Concise metadata representing the RISC-V ISA
• Tools for metadata-based generation of source and documentation
• High performance emulation, sandboxing and binary translation
• RISC-V-(n) → RISC-V-(n+1)
• RISC-V-(n) → Intel i7 / AMD64 + AVX-512
• RISC-V Linux ABI emulation on MacOS, Windows, Linux and *BSD
• RISC-V Linux ABI randomisation and entropy coding
• RISC-V Specification undefined behaviour investigation
• RISC-V Virtualization and memory protection investigation

Supported Platforms

• Target
  • RV32IMAFDC
  • RV64IMAFDC
  • Privilged ISA 1.9.1
• Host
  • Linux (Debian 9.0 x86-64, Ubuntu 16.04 x86-64, Fedora 25 x86-64) (stable)
  • macOS (Sierra 10.11 x86-64) (stable)
  • FreeBSD (11 x86-64) (alpha)

Getting Started

Building riscv-gnu-toolchain

$ sudo apt-get install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev gawk build-essential bison flex texinfo gperf libtool patchutils bc zlib1g-dev
$ git clone https://github.com/riscv/riscv-gnu-toolchain.git
$ cd riscv-gnu-toolchain
$ git submodule update --init --recursive
$ ./configure --prefix=/opt/riscv/toolchain
$ make

Building rv8

$ export RISCV=/opt/riscv/toolchain
$ git clone https://github.com/rv8-io/rv8.git
$ cd rv8
$ git submodule update --init --recursive
$ make
$ sudo make install

Running rv8

$ make test-build
$ rv-jit build/riscv64-unknown-elf/bin/test-dhrystone

Build Dependencies

• gmake
• gcc-5.4 or clang-3.4 (Linux minimum)
• gcc-6.3 or clang-3.8 (Linux recommended)
• RISC-V GNU Toolchain
• RISCV environment variable

Ubuntu 14.04LTS Dependencies

The compiler in Ubuntu 14.04LTS doesn't support C++14. These instructions will install g++6 from the ubuntu toolchain repository and build the project using g++6.

sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
sudo apt-get update
sudo apt-get install g++-6
make CXX=g++-6 CC=gcc-6

Screenshots

Example ASCII map output from make map

Example Instructions Histogram from rv-bin histogram

Example Registers Histogram from rv-bin histogram

Example Disassembly output from rv-bin dump

See RISC-V Instruction Set Listing and RISC-V Instruction Types for sample LaTeX output.

Useful Commands

Notes

• The linux target requires the RISC-V GNU Linux Toolchain
• The test-build target requires the RISC-V ELF Toolchain
• The qemu-tests target requires the third_party/qemu-tests to be built

Project Structure

Directories

Libraries

The following table shows the RISC-V Meta libraries:

Program Options

RISC-V x86-64 Simulator

RISC-V x86-64 JIT Simulator command line options:

$ rv-jit -h
usage: rv-jit [<emulator_options>] [--] <elf_file> [<options>]
            --log-instructions, -l            Log Instructions
                --log-operands, -o            Log Instructions and Operands
                 --symbolicate, -S            Symbolicate addresses in instruction log
              --log-memory-map, -m            Log Memory Map Information
                --log-syscalls, -c            Log System Calls
               --log-registers, -r            Log Registers (defaults to integer registers)
               --log-jit-trace, -T            Log JIT trace
            --log-jit-regalloc, -T            Log JIT register allocation
              --log-exit-stats, -E            Log Registers and Statistics at Exit
             --save-exit-stats, -D <string>   Save Registers and Statistics at Exit
          --pc-usage-histogram, -P            Record program counter usage
    --register-usage-histogram, -R            Record register usage
 --instruction-usage-histogram, -I            Record instruction usage
                       --debug, -d            Start up in debugger CLI
                   --no-pseudo, -x            Disable Pseudoinstruction decoding
                   --no-fusion, -N            Disable JIT macro-op fusion
     --memory-mapped-registers, -M            Disable JIT host register mapping
              --update-instret, -i            Update instret in JIT code
                    --no-trace, -t            Disable JIT tracer
                       --audit, -a            Enable JIT audit
                 --trace-iters, -I <string>   Trace iterations
                        --seed, -s <string>   Random seed
                        --help, -h            Show help

Notes

• Currently only the Linux syscall ABI proxy is implemented for the JIT simulator

RISC-V Proxy Simulator

The ABI Proxy Simulator command line options:

$ rv-sim -h
usage: rv-sim [<emulator_options>] [--] <elf_file> [<options>]
            --log-instructions, -l            Log Instructions
                --log-operands, -o            Log Instructions and Operands
                 --symbolicate, -S            Symbolicate addresses in instruction log
              --log-memory-map, -m            Log Memory Map Information
                --log-syscalls, -c            Log System Calls
               --log-registers, -r            Log Registers (defaults to integer registers)
              --log-exit-stats, -E            Log Registers and Statistics at Exit
             --save-exit-stats, -D <string>   Save Registers and Statistics at Exit
          --pc-usage-histogram, -P            Record program counter usage
    --register-usage-histogram, -R            Record register usage
 --instruction-usage-histogram, -I            Record instruction usage
                       --debug, -d            Start up in debugger CLI
                   --no-pseudo, -x            Disable Pseudoinstruction decoding
                        --seed, -s <string>   Random seed
                        --help, -h            Show help

To run the simple Hello World program (Proxy Mode):

rv-sim build/riscv64-unknown-elf/bin/hello-world-libc

RISC-V Full System Emulator

The Privilged ISA Full System Emulator command line options:

$ rv-sys -h
usage: rv-sys [<options>] <elf_file>
            --log-instructions, -l            Log Instructions
                --log-operands, -o            Log Instructions and Operands
                    --log-mmio, -O            Log Memory Mapped IO
              --log-memory-map, -m            Log Memory Map Information
               --log-mmode-csr, -M            Log Machine Control and Status Registers
               --log-smode-csr, -S            Log Supervisor Control and Status Registers
               --log-registers, -r            Log Registers (defaults to integer registers)
               --log-pagewalks, -v            Log Pagewalks
                  --log-config, -c            Log Config
                   --log-traps, -t            Log Traps
              --log-exit-stats, -E            Log Registers and Statistics at Exit
             --save-exit-stats, -D <string>   Save Registers and Statistics at Exit
          --pc-usage-histogram, -P            Record program counter usage
    --register-usage-histogram, -R            Record register usage
 --instruction-usage-histogram, -I            Record instruction usage
                       --debug, -d            Start up in debugger
                  --debug-trap, -T            Start up in debugger and enter debugger on trap
                   --no-pseudo, -x            Disable Pseudoinstruction decoding
                --map-physical, -p <string>   Map execuatable at physical address
                      --binary, -b <string>   Boot Binary ( 32, 64 )
                        --seed, -s <string>   Random seed
                        --help, -h            Show help

To run the privilged UART echo program (Privileged Mode):

rv-sys build/riscv64-unknown-elf/bin/test-m-mmio-uart

RISC-V ELF Dump Utility

ELF Dump usage command line options:

$ rv-bin dump -h
usage: dump [<options>] <elf_file>
                       --color, -c            Enable Color
            --print-elf-header, -e            Print ELF header
        --print-elf-header-ext, -x            Print ELF header (extended)
       --print-section-headers, -s            Print Section headers
       --print-program-headers, -p            Print Program headers
          --print-symbol-table, -t            Print Symbol Table
           --print-relocations, -r            Print Relocations
           --print-disassembly, -d            Print Disassembly
                      --pseudo, -P            Decode Pseudoinstructions
               --print-headers, -h            Print All Headers
                   --print-all, -a            Print All Headers and Disassembly
                        --help, -h            Show help

To run the ELF parser and disassembler:

rv-bin dump -c -a build/riscv64-unknown-elf/bin/hello-world-pcrel

Notes

• The ELF dissassembler output requires 125 column terminal window

RISC-V ELF Histogram Utility

The ELF Histogram Utility usage command line options:

$ rv-bin histogram -h
usage: histogram [<options>] <elf_file>
                        --help, -h            Show help
                        --char, -c <string>   Character to use in bars
                        --bars, -b            Print bars next to counts
                --instructions, -I            Instruction Usage Histogram
                   --registers, -R            Register Usage Histogram
          --registers-operands, -P            Register Usage Histogram (with operand positions)
                   --max-chars, -m <string>   Maximum number of characters for bars
                --reverse-sort, -r            Sort in Reverse

To print the top 20 instructions in a RISC-V ELF binary:

rv-bin histogram -I -b -c █ linux/vmlinux | head -20

To print the top 20 registers in a RISC-V ELF binary:

rv-bin histogram -R -b -c █ linux/vmlinux | head -20

RISC-V Metadata Utility

The RV source and documentation generator usage command line options:

$ rv-meta -h
usage: rv-meta [<options>]
                        --help, -h            Show help
                  --isa-subset, -I <string>   ISA subset (e.g. RV32IMA, RV32G, RV32GSC, RV64IMA, RV64G, RV64GSC)
                    --read-isa, -r <string>   Read instruction set metadata from directory
                  --no-comment, -N            Don't emit comments in generated source
           --numeric-constants, -0            Use numeric constants in generated source
         --print-constraints-h, -XC           Print constraints header
            --print-fpu-test-h, -FH           Print FPU test header
            --print-fpu-test-c, -FC           Print FPU test source
              --print-interp-h, -V            Print interpreter header
                 --print-jit-h, -J            Print jit header
                --print-jit-cc, -K            Print jit source
   --substitute-question-marks, -?            Substitute question marks for zeros in LaTeX output
                 --print-latex, -l            Print LaTeX instruction listing
                       --color, -c            Enable ANSI color map
                   --print-map, -m            Print instruction map
      --print-map-pseudocode-c, -mc           Print instruction map with C pseudocode
    --print-map-pseudocode-alt, -ma           Print instruction map with alternate pseudocode
              --print-markdown, -md           Print instruction reference in markdown
                --print-meta-h, -H            Print metadata header
               --print-meta-cc, -C            Print metadata source
            --print-operands-h, -A            Print operands header
             --print-strings-h, -SH           Print strings header
            --print-strings-cc, -SC           Print strings source
              --print-switch-h, -S            Print switch header

To print a colour opcode map for the RV32IMA ISA subset:

rv-meta -I RV32IMA -m -c -r meta

To print a colour opcode map for the RV64IMAFDS ISA subset:

rv-meta -I RV64IMAFDS -m -c -r meta

To output LaTeX for the RV32C ISA subset:

rv-meta -I RV32C -l -r meta

To output LaTeX for the RV64G ISA subset:

rv-meta -I RV64G -l -r meta

References

• lowRISC project
• Native Client x86-64 Sandbox
• Native Client ARM 32-bit Sandbox
• Design of the RISC-V Instruction Set Architecture
• RISC-V ISA Specification
• RISC-V Privileged ISA Specification
• RISC-V ISA Simulator
• RISC-V Opcodes
• RISC-V LLVM
• RISC-V Clang
• Clang SafeStack
• musl libc
• Yocto Project
• Bit Twiddling Hacks
• The Netwide Assembler
• Complete x86/x64 JIT and Remote Assembler for C++
• The Renewed Case for the Reduced Instruction Set - Macro-Op Fusion for RISC-V
• An Approach for Implementing Efficient Superscalar CISC Processors
• Optimizing Binary Translation of Dynamically Generated Code
• Live Range Hole Allocation in Dynamic Binary Translation
• Dynamic Re-compilation of Binary RISC Code for CISC Architectures
• Using Dynamic Binary Translation to Fuse Dependent Instructions
• librando: Transparent Code Randomization for Just-in-Time Compilers
• Practical Control Flow Integrity & Randomization for Binary Executables
• Abstractions for Practical Virtual Machine Replay
• A Secure Processor Architecture for Encrypted Computation on Untrusted Programs
• Jump Over ASLR: Attacking Branch Predictors to Bypass ASLR
• SoK: Eternal War in Memory
• SoK: Introspections on Trust and the Semantic Gap
• Hacking Blind
• Code Pointer Integrity
• Geometric Memory Management
• Two-Level Segregated Fit memory allocator implementation
• TLSF: a New Dynamic Memory Allocator for Real-Time Systems
• A Precise Memory Model for Low-Level Bounded Model Checking
• IEEE Std 1003.1™, 2013 Edition
• Virtual IO Device Specification
• Standard C++
• Exception Handling in LLVM
• AMD64 System V Application Binary Interface
• ELF Handling for Thread-Local Storage
• DWARF Debugging Information Format Version 4
• The Error Model and other essays
• No sane compiler would optimize atomics
• A Guide to Undefined Behavior in C and C++ (part 1 part 2 part 3)