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ExactStep - Instruction Accurate Instruction Set Simulator
Github: https://github.com/ultraembedded/exactstep
ExactStep is a simple multi-target instruction set simulator supporting RISC-V (RV32IMAC, RV64IMAC), MIPS (mips-i), and ARM-v6m (with others to come soon).
The emphasis of this project is on ease of extension, allowing its use as a library for cosimulation, peripheral development and System-C bus interfacing, rather than on raw execution performance.
Unlike QEMU and other CPU emulators which make use of dynamic binary translation, ExactStep executes one instruction per call to cpu::step().
Cloning
git clone https://github.com/ultraembedded/exactstep.git
Building
This project uses make and ELF, BFD, FDT libraries.
If you are using a Debian based Linux distro (Ubuntu / Linux Mint), you can install the required dependencies using;
sudo apt-get install libelf-dev binutils-dev libfdt-dev
To build the default command line simulator and RISC-V Linux simulators;
cd exactstep
make
ExactStep: Usage
exactstep supports various emulated CPU architectures (RISC-V, MIPS, ARM), and is used to run bare-metal executables compiled for those ISAs;
./exactstep
Usage:
--elf | -f FILE File to load (ELF or BIN)
--march | -m MISA Machine variant (e.g. RV32IMAC, RV64I, armv6, mips, ...)
--platform | -P PLATFORM Platform to simulate (basic|virt)
--dtb | -D FILE Device tree blob (binary)
--trace | -t 1/0 Enable instruction trace
--trace-mask | -v 0xXX Trace mask (verbosity level)
--cycles | -c NUM Max instructions to execute
--stop-pc | -r PC Stop at PC address
--trace-pc | -e PC Trace from PC address
--elf-phys | -E Load to ELF section to physical addresses (suitable for bootloaders)
--mem-base | -b VAL Memory base address (for binary loads)
--mem-size | -s VAL Memory size (for binary loads)
--dump-file | -p FILE File to dump memory contents to after completion
--dump-start | -j SYM/A Symbol name for memory dump start (or 0xADDR)
--dump-end | -k SYM/A Symbol name for memory dump end (or 0xADDR)
--dump-reg-f | -R FILE File to dump register file contents to after completion
--dump-reg-s | -S NUM Number of register file entries to dump
--vda | -V FILE Disk image for VirtIO block device (/dev/vda)
--tap | -T TAP Tap device for VirtIO net device
The default architecture is a RV32IMAC CPU model. To run a basic ELF;
./exactstep -f your_elf.elf
Exactstep-riscv-linux: Usage
exactstep-riscv-linux is a RISC-V (32-bit or 64-bit) specific simulator which contains a built-in SBI (Supervisor Binary Interface) implementation that enables booting RISC-V Linux kernels compiled for supervisor mode. Root filesystems can also be provided by initrd, VirtIO block device, or VirtIO network (nfs) boot.
./exactstep-riscv-linux
Usage:
--elf | -f FILE File to load (ELF)
--bin | -b FILE File to load (binary)
--march | -m MISA Machine variant (e.g. RV32IMAC, RV64I, ...)
--platform | -P PLATFORM Platform to simulate (basic|virt)
--dtb | -D FILE Device tree blob (binary)
--dtb-base | -B 0xaddr Device tree blob load address
--trace | -t 1/0 Enable instruction trace
--trace-mask | -v 0xXX Trace mask (verbosity level)
--cycles | -c NUM Max instructions to execute
--stop-pc | -r PC Stop at PC address
--trace-pc | -e PC Trace from PC address
--vda | -V FILE Disk image for VirtIO block device (/dev/vda)
--tap | -T TAP Tap device for VirtIO net device
--initrd | -i FILE initrd binary (optional)
Example usage (with a device tree compiled to a DTB file using the Linux Kernel dtc util);
./exactstep-riscv-linux --elf ./vmlinux-rv32ima-5.0 --dtb ./config.dtb --initrd ./initrd.cpio
Running RISC-V Compliance Tests
ExactStep passes the RISC-V Compliance Tests for the rv32i, rv32im, rv32imc, rv64i, rv64im categories;
# Get compliance test suite
git clone https://github.com/ultraembedded/riscv-compliance.git
cd riscv-compliance
# Set path to built exactstep executable
export TARGET_SIM=/path/to/github/exactstep/exactstep
# Run test suite
make RISCV_TARGET=exactstep
Running RISC-V Linux
# Get prebuilt bootloader + kernel + rootfs images
git clone https://github.com/ultraembedded/riscv-linux-prebuilt.git
cd riscv-linux-prebuilt
# Boot Linux (with Busybox userspace)
exactstep --march RV64IMAC --elf opensbi-kernel-busybox/qemu-virt-rv64-5.4-rc7-busybox-1.32.0.elf --dtb opensbi-kernel-busybox/qemu-virt-rv64-config.dtb