kvm-host-simple.py

#!/usr/bin/python3

from fcntl import ioctl
import sys
import time
from mmap import mmap, PROT_READ, PROT_WRITE, MAP_SHARED, MAP_PRIVATE, MAP_ANONYMOUS
from structs import *

RAM_SIZE = 0x10000


def load_guestbin(path):
    with open(path, 'rb') as guest:
        return guest.read()


def main():
    with open('/dev/kvm', 'wb+') as kvm_fd:
        # KVM layer
        version = ioctl(kvm_fd, KVM_GET_API_VERSION, 0)
        if version != 12:
            print(f'Unsupported version: {version}')
            sys.exit(1)

        # Create VM
        vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0)

        # Create VM Memory
        mem = mmap(-1, RAM_SIZE, MAP_PRIVATE | MAP_ANONYMOUS, PROT_READ | PROT_WRITE)
        pmem = ctypes.c_uint.from_buffer(mem)
        mem_region = UserspaceMemoryRegion(slot=0, flags=0,
                                           guest_phys_addr=0, memory_size=RAM_SIZE,
                                           userspace_addr=ctypes.addressof(pmem))
        ioctl(vm_fd, KVM_SET_USER_MEMORY_REGION, mem_region)

        # Create VCPU
        vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);

        # Read guest.bin
        guest_bin = load_guestbin('guest.bin')
        mem[:len(guest_bin)] = guest_bin

        sregs = Sregs()
        ioctl(vcpu_fd, KVM_GET_SREGS, sregs)
        # Initialize selector and base with zeros
        sregs.cs.selector = sregs.cs.base = sregs.ss.selector = sregs.ss.base = sregs.ds.selector = sregs.ds.base = sregs.es.selector = sregs.es.base = sregs.fs.selector = sregs.fs.base = sregs.gs.selector = 0
        # Save special registers
        ioctl(vcpu_fd, KVM_SET_SREGS, sregs)

        # Initialize and save normal registers
        regs = Regs()
        regs.rflags = 2  # bit 1 must always be set to 1 in EFLAGS and RFLAGS
        regs.rip = 0  # our code runs from address 0
        ioctl(vcpu_fd, KVM_SET_REGS, regs)

        runsz = ioctl(kvm_fd, KVM_GET_VCPU_MMAP_SIZE, 0)
        run_buf = mmap(vcpu_fd, runsz, MAP_SHARED, PROT_READ | PROT_WRITE)
        run = Run.from_buffer(run_buf)

        try:
            while True:
                ret = ioctl(vcpu_fd, KVM_RUN, 0)
                if ret < 0:
                    print('KVM_RUN failed')
                    return
                if run.exit_reason == KVM_EXIT_IO:
                    print(f'IO port: {run.io.port}, data: {run_buf[run.io.data_offset]}')
                elif run.exit_reason == KVM_EXIT_SHUTDOWN:
                    return
                time.sleep(1)
        except KeyboardInterrupt:
            pass


if __name__ == '__main__':
    main()