#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <nvmm.h>

#define PAGE_SIZE 4096

/*
 * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! NOTE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 * ----------------------------------------------------------------------------
 * Below is an updated version of this example, because the libnvmm API has
 * changed since I posted the blog entry. See:
 *     https://mail-index.netbsd.org/tech-kern/2019/06/05/msg025101.html
 * The original version (using the previous API) is available here:
 *     https://www.netbsd.org/~maxv/nvmm/calc-vm-old-api.c
 * ----------------------------------------------------------------------------
 */

/*
 * A simple calculator. Creates a VM which performs the addition of the two
 * ints given as argument.
 *
 * The guest does EBX+=EAX, followed by HLT. We set EAX and EBX, and then
 * fetch the result in EBX. HLT is our shutdown point, we stop the VM there.
 *
 * We give one single page to the guest, and copy there the instructions it
 * must execute. The guest runs in 16bit real mode, and its initial state is
 * the x86 RESET state (default state). The instruction pointer uses CS.base
 * as base, and this base value is 0xFFFF0000. So we make it our GPA, and set
 * RIP=0, which means "RIP=0xFFFF0000+0". The guest therefore executes the
 * instructions at GPA 0xFFFF0000.
 *
 *     gcc -o calc-vm calc-vm.c -lnvmm
 *     ./calc-vm 3 5
 *     Result: 8
 *
 * Don't forget to modload the NVMM kernel module beforehand!
 */
int main(int argc, char *argv[])
{
	const uint8_t instr[] = {
		0x01, 0xc3,	/* add %eax,%ebx */
		0xf4		/* hlt */
	};
	struct nvmm_machine mach;
	struct nvmm_vcpu vcpu;
	uintptr_t hva;
	gpaddr_t gpa = 0xFFFF0000;
	int num1, num2, ret;

	if (argc != 3)
		errx(EXIT_FAILURE, "wrong arguments");
	num1 = atoi(argv[1]);
	num2 = atoi(argv[2]);

	/* Init NVMM. */
	if (nvmm_init() == -1)
		err(EXIT_FAILURE, "unable to init NVMM");

	/* Create the VM. */
	if (nvmm_machine_create(&mach) == -1)
		err(EXIT_FAILURE, "unable to create the VM");
	nvmm_vcpu_create(&mach, 0, &vcpu);

	/* Allocate a HVA. The HVA is writable. */
	hva = (uintptr_t)mmap(NULL, PAGE_SIZE, PROT_READ|PROT_WRITE,
	    MAP_ANON|MAP_PRIVATE, -1, 0);
	nvmm_hva_map(&mach, hva, PAGE_SIZE);

	/* Link the GPA towards the HVA. The GPA is executable. */
	nvmm_gpa_map(&mach, hva, gpa, PAGE_SIZE, PROT_READ|PROT_EXEC);

	/* Install the guest instructions there. */
	memcpy((void *)hva, instr, sizeof(instr));

	/* Reset the instruction pointer, and set EAX/EBX. */
	nvmm_vcpu_getstate(&mach, &vcpu, NVMM_X64_STATE_GPRS);
	vcpu.state->gprs[NVMM_X64_GPR_RIP] = 0;
	vcpu.state->gprs[NVMM_X64_GPR_RAX] = num1;
	vcpu.state->gprs[NVMM_X64_GPR_RBX] = num2;
	nvmm_vcpu_setstate(&mach, &vcpu, NVMM_X64_STATE_GPRS);

	while (1) {
		/* Run VCPU0. */
		nvmm_vcpu_run(&mach, &vcpu);

		/* Process the exit reasons. */
		switch (vcpu.exit->reason) {
		case NVMM_VCPU_EXIT_NONE:
			/* Nothing to do, keep rolling. */
			break;
		case NVMM_VCPU_EXIT_HALTED:
			/* Our shutdown point. Fetch the result. */
			nvmm_vcpu_getstate(&mach, &vcpu, NVMM_X64_STATE_GPRS);
			ret = vcpu.state->gprs[NVMM_X64_GPR_RBX];
			printf("Result: %d\n", ret);
			return 0;
			/* THE PROCESS EXITS, THE VM GETS DESTROYED. */
		default:
			errx(EXIT_FAILURE, "unknown exit reason");
		}
	}

	return 0;
}