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Bytecode Virtual Machine (BVM)

A simple virtual machine (VM) that executes a custom bytecode instruction set. The BVM supports a variety of operations, including arithmetic, stack manipulation, flow control, and system calls. To program this vm see https://github.com/BlagojeBlagojevic/blang.

Features

• Stack-based architecture
• Supports integer, float, and character operations
• Arithmetic operations (ADD, MUL, DIV, MOD, DEC, INC)
• Bitwise operations (SHR, SHL, OR, AND, BNOT)
• Stack manipulation (PUSH, POP, DUP, OVER, ROT, SWAP)
• Flow control (IF, JMP, JMPT, JMPF,)
• Memory operations (MEM, COPY, COPYSTACK, MEMSTACK)
• System calls (WRITE, READ, EXIT, SYSTEM, etc.) via SYSCALLS define
• FFI(DRIVER)
• Input/output operations (PRINT, PRINTSTRING, PRINTSTACK)

Getting Started

Prerequisites

• A C compiler (GCC, Clang, etc.)

Building the Project

1. Clone the repository:

   git clone https://github.com/BlagojeBlagojevic/BVM.git
   cd BVM

2. Compile the project (enable syscalls with -DSYSCALLS -DSYSTEM if needed):

   gcc -o bvm main.c -DSYSCALLS -DSYSTEM

Running the VM

Execute a program from a text file:

./bvm program.txt

Bytecode Instruction Set

Stack Operations

• PUSH <value>: Push an integer onto the stack.
• PUSHF <value>: Push a float onto the stack.
• PUSHIP: Push the current instruction pointer (IP) onto the stack.
• PUSHSP: Push the stack pointer (SP) onto the stack.
• POP: Remove the top value from the stack.
• DUP: Duplicate the top stack value.
• OVER: Copy the second stack item to the top.
• ROT: Rotate the top three stack items.
• SWAP_NO: Swap the top two stack values.
• SWAP <index>: Swap the top value with the value at index.

Arithmetic Operations

• ADD <type>: Add top two values. type: 0 (int), 1 (float), 2 (uint).
• MUL <type>, DIV <type>, DEC <type>, MOD: Multiply, divide, decrement, modulo.
• INC <value>: Increment the top value by value.

Bitwise Operations

• SHR, SHL: Shift right/left.
• OR, AND, BNOT: Bitwise OR, AND, NOT.

Control Flow

• IF <cond>: Compare top two values. cond: '>' (0), '<' (1), '==' (2). Push 1/0.
• JMP <address>: Jump to address.
• JMPT <address>: Jump if top value is non-zero.
• JMPF <address>: Jump if top value is zero.
• SETSP <index>: Set stack pointer to index.
• RESTORE <new_sp>: Restore SP to <new_sp> and IP from the stack..

Memory Operations

• COPY <index>: Copy value at index to the top.
• MEM <index>: Store top value at index.
• COPYSTACK <memaddres>: Copy value from memaddres to a SP-1
• MEMSTACK <memaddres, value>: Copy value to a mem addres

I/O Operations

• PRINT <type>: Print top value. type: 0 (int), 1 (float), 2 (char).
• PRINTSTRING: Print null-terminated string from the stack.
• PRINTSTACK: Dump the entire stack.

System Calls (Require SYSCALLS define)

• WRITE: Write to a file descriptor (args: fd, data, size).
• READ: Read from a file descriptor.
• EXIT: Terminate the VM with a status code.
• SYSTEM: Execute a shell command (requires SYSTEM define).

FFI

• DRIVER: Calls a device driver function specified by the driver number.

Miscellaneous

• NOP: No operation.
• HALT: Pause execution (debugging).
• END: Terminate the VM gracefully.

Example Program

PUSH 10
PUSH 20
ADD 0
PRINT 0
PUSH 65
PRINT 2    # Prints 'A'
PUSH 0
PUSH 1
IF >
JMPT 7     # Jump to HALT if 1 > 0
PRINT 0
HALT
END

License

MIT License. See LICENSE for details.