Lab2: RISC-V RV32I[MA] emulator with ELF support

rv32emu

• RISCV emulator for the RV32I architecture
• based on TinyEMU by Fabrice Bellard, check Lab0: Web-based Emulators
• stripped down for RV32I only, all "gotos" removed, and fixed some bugs for the compliance test

Sample Usage on Ubuntu Linux

At present, we only verify on Ubuntu GNU/Linux. Please install Ubuntu Linux 20.04-LTS (or later) into your machine. It is fine with virtualization environments such as VirtualBox.

1. Prepare GNU Toolchain for RISC-V. See The xPack GNU RISC-V Embedded GCC

$ cd /tmp
$ wget https://github.com/xpack-dev-tools/riscv-none-embed-gcc-xpack/releases/download/v10.2.0-1.1/xpack-riscv-none-embed-gcc-10.2.0-1.1-linux-x64.tar.gz
$ tar zxvf xpack-riscv-none-embed-gcc-10.2.0-1.1-linux-x64.tar.gz
$ cp -af xpack-riscv-none-embed-gcc-10.2.0-1.1 $HOME/riscv-none-embed-gcc

2. Configure $PATH

$ cd $HOME/riscv-none-embed-gcc
$ echo "export PATH=`pwd`/bin:$PATH" > setenv

Once step (1) and (2) are complete, you can simply update $PATH environment variable via:

$ cd $HOME
$ source riscv-none-embed-gcc/setenv

Check $PATH at the first time:

$ riscv-none-embed-gcc -v

You shall be able to see the following messages:

gcc version 10.1.0 (xPack GNU RISC-V Embedded GCC, 64-bit) 

3. Fetch rv32emu and build from source

$ git clone https://github.com/sysprog21/rv32emu
$ cd rv32emu
$ make

4. Validate rv32emu

$ make check

You shall see the following messages:

./emu-rv32i test1
Hello RISC-V!

>>> Execution time: 29144 ns
>>> Instruction count: 62 (IPS=2127367)
>>> Jumps: 14 (22.58%) - 0 forwards, 14 backwards
>>> Branching T=13 (92.86%) F=1 (7.14%)

Using GNU Toolchain

• objdump

-d : Display the assembler mnemonics for the machine instructions

$ riscv-none-embed-objdump -d test1

Expected output:

test1:     file format elf32-littleriscv

Disassembly of section .text:

00010054 <_start>:
   10054:	000107b7          	lui	a5,0x10
   10058:	07878793          	addi	a5,a5,120 # 10078 <_start+0x24>
   1005c:	04800713          	li	a4,72
   10060:	400026b7          	lui	a3,0x40002
   10064:	00e68023          	sb	a4,0(a3) # 40002000 <__global_pointer$+0x3fff0778>
   10068:	00178793          	addi	a5,a5,1
   1006c:	0007c703          	lbu	a4,0(a5)
   10070:	fe071ae3          	bnez	a4,10064 <_start+0x10>
   10074:	00008067          	ret

• readelf

-h : Display the ELF file header

$ riscv-none-embed-readelf -h test1

Expected output:

ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           RISC-V
  Version:                           0x1
  Entry point address:               0x10054
  Start of program headers:          52 (bytes into file)
  Start of section headers:          540 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         1
  Size of section headers:           40 (bytes)
  Number of section headers:         7
  Section header string table index: 6

• size

list the section sizes–-and the total size–-for each of the object or archive files objfile in its argument list.

$ riscv-none-embed-size test1

Expected output:

   text	   data	    bss	    dec	    hex	filename
     52	      0	      0	     52	     34	test1