WORK CHANGE LIST

PA1 Infrastructure

pa1.1 implement sdb (simple debugger) mimicing instruction of gdb:

• nemu/src/monitor/sdb/sdb.c

• support step run (si [N]), info register (info r), memory scanning (x N ADDR_EXPR).

• support EXPR parsing with regex. (Arith Calculator!) Therefore support print command (p EXPR)

  • added and tested in pa1.2

• support watchpoint (w EXPR), info watchpoint (info w), delete watchpoint (d N)

  • added in pa1.3

pa1.2 implement a random unit test generator and test sdb commands on evaluating expression.

• generating sequence of expression using recursion, deal with buffer overflow, zero division, and unsigned int problem.

  • nemu/tools/gen-expr/gen-expr.c
  • nemu/tools/gen-expr/testout (10000 lines of generated unit test)

• Add testing function when booting

  • nemu/src/nemu-main.c:42 test_expr()

pa1.3 Watchpoint

• extend EXPR evaluation functionality, support register value ($reg), ptr dereference (*), and other logic operator (!=,&&)

  • nemu/src/monitor/sdb/sdb.c

• set up watchpoint pool API using linkedlist implementation:

  • nemu/src/monitor/sdb/watchpoint.c

• scan for watchpoint change in main and set NEMU state to STOP.

  • nemu/src/cpu/cpu-exec.c
  • add functions for printing and checking wp change in nemu/src/monitor/sdb/watchpoint.c.

• use Kconfig to control functionality.

  • understand Kconfig and modify: nemu/Kconfig
  • set up config entry for watchpoint function and debug output;
  • change setting by running make menuconfig in nemu/.

PA2 RISC-V bare-metal

pa2.1 implement all RISC-V instruction set: include RV32I and RV32M

• nemu/src/isa/riscv32/inst.c

• Read through risc-V inst set and implement every instruction:

  • support integer arithmetic through I and R instruction decoding.
  • support memory load and store through I/U and S instrucion decoding.
  • support jumping and branching through B and J/I instrucion decoding.

• Run a bunch of simple C program's object file through nemu and pass.

  • tests located in am-kernels/tests/cpu-tests/tests, and can be run though command: make ARCH=riscv32-nemu ALL={test program without .c suffix} run

• Abstract-machine lib function

  • look through man pages and implement string functions: strlen, strcpy, strncpy, strcat, strcmp, strncmp; (abstract-machine/klib/src/string.c)
  • memory functions: memset, memmove, memcmp, memcpy; (abstract-machine/klib/src/string.c)
  • print functions: sprintf,vsprintf,snprintf,vsnprintf. (abstract-machine/klib/src/stdio.c)

pa2.2 tracing (Infrastructure part 2)

• set up Instruction Ring Buffer and integrate into sdb:

  • nemu/src/monitor/sdb/iringbuf.c
  • nemu/include/monitor/iringbuf.h

• add Memory Trace function and enabling control through Kconfig:

  • nemu/src/memory/paddr.c
  • nemu/Kconfig

• add Function Tracing:

  • add -e argument to main to parse elf file, modify makefile to load elf file
    • abstract-machine/scripts/platform/nemu.mk
    • nemu/src/monitor/monitor.c
  • detect function calling and return with jal and jalr instruction, and print trace appropiately
    • nemu/src/isa/riscv32/inst.c
  • modify Kconfig to add option on opening ftrace

• klib testing:

  • add folder for klib testing: am-kernels/tests/klib-tests.
  • write testsuite for klib functions, and test on native.
    • am-kernels/tests/klib-tests/src/tests/test_memory.c
    • am-kernels/tests/klib-tests/src/tests/test_string.c
    • am-kernels/tests/klib-tests/src/tests/test_printf.c
    • am-kernels/tests/klib-tests/src/tests/test_test_setup.c

• DIFF test:

  • nemu/src/isa/riscv32/difftest/dut.c
  • add differential testing for nemu,comparing with REF spike. Comparing only register each step!

pa2.3 IO device

• read source code, fix bug in printf when invoking nemu putch.

• implement timer device. Understand AM abstraction level better.

  • run benchmark at /home/tom/ics2023/am-kernels/benchmarks, get score ~200 / 100000 Marks (i9-9900K @ 3.60GHz)

• dtrace. tracing of device access. (with Kconfig)

• keyboard device. Record and detect make code and break code.

  • abstract-machine/am/src/platform/nemu/ioe/input.c
  • nemu/src/device/keyboard.c

• VGA: implement VGA display IOE

  • NEMU part, include registering this device and register read write behaviors and maps: nemu/src/device/vga.c
  • AM part, include drawing rect and syncing through io_read/io_write: abstract-machine/am/src/platform/nemu/ioe/gpu.c

• Run NEMU on NEMU

  • Fix Bug
  • Turing Complete, use the following command to run NEMU(no image) on NEMU, or run SNAKE on NEMU on NEMU... (Very Slow!)
  • make ARCH=riscv32-nemu mainargs=/home/<username>/ics2023/am-kernels/kernels/snake/build/snake-riscv32-nemu.bin

PA3 Operating System

pa3.1 Error Handling and OS context change.

• Hardware level: implement privileged instruction set RV32-Zicsr extension along CSR hardware.

  • Implement the CSR registers in NEMU and raise_intr function for ecall.
  • implement atomic read/write csr instructions: csrrw,csrrs,csrrc,csrrwi,csrrsi,csrrci,ecall,mret.
  • nemu/src/isa/riscv32/inst.c
  • pass yield test: ~/ics2023/am-kernels/tests/am-tests$ make ARCH=riscv32-nemu mainargs=i run

• Software level: AM save/restore Context, Event handling

  • save/restore context in abstract-machine/am/src/riscv/nemu/trap.S
    • note this is the OS define routine. Also: it should be adding 34 to the mepc CSR to avoid caughtup infinitely at ecall.
  • handling event in abstract-machine/am/src/riscv/nemu/cte.c:__am_irq_handle, called by trap.S.
  • the journey:
    • start with client software program calling yield,
    • in assembly code, its doing ecall.
    • our NEMU hardware translate this instruction to storing CSR and jump PC to mtvec (nemu/src/isa/riscv32/system/intr.c:isa_raise_intr)
    • the code at mtvec is AM(OS) defined (abstract-machine/am/src/riscv/nemu/trap.S:__am_asm_trap), which store context, and handle events by calling abstract-machine/am/src/riscv/nemu/cte.c:__am_irq_handle, and restore context, then mret.
    • mret , translated by NEMU: restore pc to CSR mepc, and continue program going on "user level". (returning control from OS)

• etrace: Exception Tracing

  • nemu/Kconfig
  • nemu/src/isa/riscv32/system/intr.c

pa3.2 User Program and Syscall.

• setting up nanos-lite, simple OS.

  • fix instruction bug on yield. change mcause to store a7 register.
  • handled YIELD event.

• program loader.

  • load program that is Cmake into ramdisk.img
  • read ELF file, extract segments, and memset/copy to virtual locations: 0x83000000.
  • nanos-lite/src/loader.c

• syscall upper level API

  • implement syscall function on nanos level, used by navy.
    • SYS_yield: handle yield event initiated by user program
    • SYS_exit: exiting program, signify OS to change program.
    • SYS_read, SYS_write (_read,_write): read and write from ramdisk.
    • SYS_brk (_sbrk): set up sbrk for heap management, for malloc/free.
  • strace: trace the syscall.

• File System

  • Simple File System

    • update loader to handled loading by filename.
    • update syscall (open,read,write) to support fd argument, by calling:
      • fs_open, fs_close
      • fs_read, fs_write
      • fs_lseek

  • Virtual File System (IOE as files)

    • update fs_read and fs_write by implementing special read write functions for the virtual files.
    • implement serial output as file write.
    • implement gettimeofday as file read. (and implement the navy:NDL_GetTicks)
    • impelment keyboard info as file read.
    • impelment VGA display info as file read.
    • impelment VGA display as file write.

NOTE: nanos user call syscall by calling ecall with param, the irq classify it as syscall event and hand to do_syscall, do_syscall (OS) delegate to am-yield, am yield do ecall/mtvec/... use do_event handler and return a value. do_syscall store the return val and hand it back to user

pa3.3 More interesting User Program.

• implement fixedpt to simulate float number algebra without the float number riscv extension. (fixedptc.h)

• SDL: (navy-apps/libs/libminiSDL/)[https://www.libsdl.org/release/SDL-1.2.15/docs/]

  • implement the SDL_updateRect function, upper level API update an area to VGA. (NSlider)
  • SDL_FillRect(),SDL_BlitSurface(): GPU basic ability on VGA.(MENU)
  • SDL_GetTicks(): calling NDL function.
  • SDL_WaitEvent, SDL_PollEvent(): wait or poll an event, that is keyboard or user defined.(NTerm)
  • IMG_Load: Load Image (Flappy bird)