Create a virtual machine with a C interpreter - retrotruestory/M1DEV GitHub Wiki

Yes, it's possible to modify the Magic-1 bootloader to create a virtual machine with a C interpreter instead of loading Minix. Here's a high-level approach:

        .cseg
        .global _init_virtual_machine
        .global _setup_interpreter

_init_virtual_machine:
        enter   8
        push    a
        push    b
        
        // Setup VM memory space
        ld.16   b,#VM_BASE    ; Load VM base address
        ld.16   c,#VM_SIZE    ; Load VM size
        
        // Map VM pages
        call    _map_vm_pages
        
        // Initialize interpreter space
        ld.16   a,#INTERP_BASE
        st.16   (b),a         ; Store interpreter base
        
        pop     b
        pop     a
        leave
        ret

Create a C interface for the VM and interpreter:

#ifndef VM_H
#define VM_H

#define VM_BASE     0x10000
#define VM_SIZE     0x8000
#define INTERP_BASE 0x18000

typedef struct {
    uint16_t pc;          // Program counter
    uint16_t sp;          // Stack pointer
    uint16_t bp;          // Base pointer
    uint8_t *memory;      // VM memory
    uint16_t mem_size;    // Memory size
} vm_context;

// VM initialization and control
extern void init_virtual_machine(void);
extern int run_interpreter(char *source);
extern void execute_vm_instruction(vm_context *ctx);

#endif

Basic interpreter implementation:

#include "vm.h"

#define MAX_CODE_SIZE 4096

static vm_context vm;
static uint8_t code_buffer[MAX_CODE_SIZE];

int run_interpreter(char *source) {
    // Parse source code
    if (!parse_source(source, code_buffer)) {
        return -1;
    }
    
    // Initialize VM context
    vm.pc = 0;
    vm.sp = VM_SIZE - 1;
    vm.bp = vm.sp;
    vm.memory = (uint8_t*)VM_BASE;
    vm.mem_size = VM_SIZE;
    
    // Copy code to VM memory
    fast_memcpy(vm.memory, code_buffer, MAX_CODE_SIZE);
    
    // Main interpretation loop
    while (vm.pc < vm.mem_size) {
        execute_vm_instruction(&vm);
    }
    
    return 0;
}

Modify bootloader main to support VM option:

void main() {
    // ...existing initialization code...
    
    if (check_vm_flag()) {
        // Initialize VM environment
        init_virtual_machine();
        
        // Load interpreter source
        char *interp_source = load_interpreter_source();
        
        // Run interpreter instead of Minix
        run_interpreter(interp_source);
    } else {
        // Normal Minix boot process
        boot_minix();
    }
}

Key features this implementation would provide:

Considerations:

  1. Memory management would need careful planning
  2. Performance would be slower than native code
  3. Would need to implement system calls for VM
  4. Hardware access would need to be controlled

The VM could be extended to support: