docs/pypowersim_tut.mdwn

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