docs/pypowersim_tut.mdwn

   1 # Pypowersim/ISACaller tutorial - In progress!
   2
   3 * Libre-SOC Wiki OpenPOWER ISA Pseudo-code: <https://libre-soc.org/openpower/isa/>
   4 * PowerPC Arch assembler lecture: <https://www.eecs.umich.edu/courses/eecs373.w04/Lectures/stever_old_lectures/lec2.pdf>
   5 * Hello world in PPC64 assembly: <https://github.com/matja/asm-examples/blob/master/ppc64/hello.ppc64.linux.syscall.gas.asm>
   6 * Hello world in PPC64LE assembly: <https://gist.github.com/sandip4n/09b50786e88968faaecdf42360c85b1b>
   7
   8 This tutorial is intended to get started with Libre-SOC's in-house instruction
   9 simulator. The main Python class doing the work is called `ISACaller`, while
  10 the more comprehensive wrapper file used to run binaries is called
  11 `pypowersim`.
  12
  13 ## `-->` START HERE `<--` Run `ISACaller` unit tests first!
  14
  15 TODO: Document tutorial.
  16
  17 Since `pypowersim` is much more involved (as it requires PC, register setup,
  18 etc.), it is *strogly* encouraged to first write a basic unit test involving
  19 the `ISACaller` class.
  20
  21 ### Find appropriate umbrella `test_caller_[FUNCTION].py` class
  22
  23 The directory `openpower-isa/src/openpower/decoder/isa/` contains a set of files
  24 for running unit tests using pytest. If adding tests for a new category, a new
  25 umbrella will need to be created.
  26
  27 The umbrella file has name of the form `test_caller_[FUNCTION].py`.
  28 For example of the ALU test caller, see
  29 [`test_caller_alu.py`](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/decoder/isa/test_caller_alu.py;hb=HEAD).
  30
  31 It's suggested to copy the contents of an existing test caller file.
  32
  33 ### Write unit tests under the `src/openpower/test/[FUNCTION]/` directory
  34
  35 Once a test caller class exists, the actual tests reside under the
  36 `src/openpower/test/[FUNCTION]/` directory. For example of the ALU tests, see
  37 [alu_cases.py](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/test/alu/alu_cases.py;hb=HEAD)
  38
  39 Copy an existing file when writing new tests, which should gradually teach you
  40 how to use the `ISACaller` class.
  41
  42 ### Example of new test - system call instructions
  43
  44
  45
  46 ## Setup a Debian 10 chroot environment
  47
  48 **Skip this section if `pypowersim` is already present on your system.**
  49
  50 Setup new chroot:
  51
  52     $ cd dev-env-setup
  53     $ sudo bash
  54     # ./mk-deb-chroot isacaller
  55     # ./mk-deb-chroot isacaller
  56     # exit
  57     $ schroot -c isacaller
  58     (isacaller):$ cd dev-env-setup
  59     (isacaller):$ sudo bash
  60     (isacaller):# ./install-hdl-apt-reqs
  61     (isacaller):# ./hdl-tools-yosys
  62     (isacaller):# ./hdl-dev-repos
  63     (isacaller):# ./binutils-gdb-install
  64     (isacaller):# exit
  65
  66 *(NOTE to self: check if `hdl-dev-repos` actually necessary)*
  67
  68 From here on, `pypowersim` should be in your `$PATH` and can simply be called
  69 from your terminal (when inside the newly created chroot).
  70
  71     (isacaller):$ pypowersim --help
  72
  73 Help message (may change, so try yourself):
  74
  75     -i --binary=   raw (non-ELF) bare metal executable, loaded at 0x0
  76     -a --listing=  file containing bare-metal assembler (no macros)
  77     -g --intregs=  colon-separated file with GPR values
  78     -f --fpregs=   colon-separated file with FPR values
  79     -s --spregs=   colon-separated file with SPR values
  80     -l --load=     filename:address to load binary into memory
  81     -d --dump=     filename:address:len to binary save from memory
  82     -q --qemu=     run qemu co-simulation
  83     -p --pc=       set initial program counter
  84     -h --help      prints this message
  85     notes:
  86     load and dump may be given multiple times
  87     load and dump must be 8-byte aligned sizes
  88     loading SPRs accepts SPR names (e.g. LR, CTR, SRR0)
  89     numbers may be integer, binary (0bNNN) or hex (0xMMM) but not FP
  90     running ELF binaries: load SPRs, LR set to 0xffffffffffffffff
  91     TODO: dump registers
  92     TODO: load/dump PC, MSR, CR
  93     TODO: print exec and sub-exec counters at end
  94
  95 ## Running existing example
  96
  97 To start with, let's see how a comprehensive example works. A good demonstrator
  98 of the capabilities of SVP64 is the XChaCha20 encryption algorithm. (Difference
  99 between ChaCha20 and XChaCha20 being an
 100 [extended 192-bit nonce](https://crypto.stackexchange.com/a/101505)).
 101
 102 This page will go into the details of running the simulator, not the SVP64
 103 specifics. Please see the SVP64 Cookbook page on
 104 [ChaCha20](https://libre-soc.org/openpower/sv/cookbook/chacha20/)
 105 for more detailed information on the algorithm and SVP64 features.
 106
 107 To run the example.
 108
 109     (isacaller):$ cd ~/src/openpower-isa/crypto/chacha20
 110     (isacaller):$ make
 111     (isacaller):$ ./test-chacha20
 112
 113 Or with `SILENCELOG=1` if you want less terminal output from the simulator:
 114
 115     (isacaller):$ SILENCELOG=1 ./test-chacha20
 116
 117 ## Explanation of the process
 118
 119 Konstantinos
 120 [summarising the process](https://libre-soc.org/irclog/latest.log.html#t2023-09-10T18:44:49).
 121
 122