95 lines
4.2 KiB
Org Mode
95 lines
4.2 KiB
Org Mode
#+title: Aryadev's Virtual Machine (AVM)
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#+author: Aryadev Chavali
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#+date: 2023-10-15
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A virtual machine in C11, stack oriented with a dynamic register.
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Deals primarily in bytes, doesn't make assertions about typing and is
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very simple to target.
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This repository contains both a library ([[file:lib/][lib]]) to
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(de)serialize bytecode and a program ([[file:vm/][vm]]) to execute
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said bytecode.
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* How to build
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Requires =GNU make= and a compliant C11 compiler. Code base has been
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tested against =gcc= and =clang=, but given how the project has been
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written without use of GNU'isms (that I'm aware of) it shouldn't be an
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issue to compile using something like =tcc= or another compiler (look
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at [[file:Makefile::CC=gcc][here]] to change the compiler used).
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To build a release version simply run ~make all RELEASE=1~. To build
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a debug version run ~make all VERBOSE=<n>~ where n can be 0, 1 or 2
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depending on how verbose you want logs to standard output to be. This
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will build:
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+ [[file:lib/][instruction bytecode system]] which provides a shared
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library for serialising and deserialising bytecode
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+ [[file:vm/][VM executable]] to execute bytecode
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You may also build each component individually through the
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corresponding recipe:
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+ ~make lib~
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+ ~make vm~
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* Targeting the virtual machine
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Link with the shared library =libavm.so= which should be located in
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the =build= folder. The general idea is to construct a ~prog_t~
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structure, which consists of:
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1) A program header with some essential properties of the program
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(start address, count, etc)
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2) An array of type ~inst_t~, ordered instructions for execution
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This structure may be executed in two ways.
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** Compilation then separate execution
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The ~prog_t~ structure along with a sufficiently sized buffer of bytes
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(using ~prog_bytecode_size~ to get the size necessary) can be used to
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call ~prog_write_bytecode~, which will populate the buffer with the
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corresponding bytecode.
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The buffer is written to some file then executed using the =avm=
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executable. This is the classical way I expect languages to target
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the virtual machine.
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** In memory virtual machine
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This method is more involved, introducing the virtual machine runtime
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into the program itself. After constructing a ~prog_t~ structure, it
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can be fit into a ~vm_t~ structure. This ~vm_t~ structure also must
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have a stack, heap and call stack (look at [[file:vm/main.c]] to see
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this in practice). This structure can then be used with
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~vm_execute_all~ to execute the program.
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Note that this skips the serialising process (i.e. the /compilation/)
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by utilising the runtime directly. I could see this approach being
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used when writing an interpreted language such as Lisp where code
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should be executed immediately after parsing. Furthermore,
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introducing the runtime directly into the calling program gives much
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greater control over parameters such as stack/heap size and step by
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step execution which can be useful in dynamic contexts. Furthermore,
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the ~prog_t~ can still be compiled into bytecode whenever required.
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* Related projects
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[[https://github.com/aryadev-software/aal][Assembler]] program which
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can compile an assembly-like language to bytecode.
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* Lines of code
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#+begin_src sh :results table :exports results
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wc -lwc $(find vm/ lib/ -regex ".*\.[ch]\(pp\)?")
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#+end_src
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#+RESULTS:
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|------------------+-------+-------+------------|
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| File | Lines | Words | Characters |
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|------------------+-------+-------+------------|
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| vm/runtime.h | 266 | 699 | 7250 |
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| vm/main.c | 135 | 375 | 3448 |
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| vm/runtime.c | 802 | 2441 | 23634 |
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| vm/struct.c | 262 | 783 | 7050 |
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| vm/struct.h | 69 | 196 | 1531 |
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| lib/inst.c | 493 | 1215 | 13043 |
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| lib/darr.h | 149 | 709 | 4482 |
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| lib/inst.h | 248 | 519 | 4964 |
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| lib/inst-macro.h | 71 | 281 | 2806 |
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| lib/heap.h | 125 | 453 | 3050 |
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| lib/base.h | 190 | 710 | 4633 |
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| lib/heap.c | 79 | 214 | 1647 |
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| lib/base.c | 61 | 226 | 1583 |
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| lib/darr.c | 76 | 219 | 1746 |
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|------------------+-------+-------+------------|
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| total | 3026 | 9040 | 80867 |
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|------------------+-------+-------+------------|
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