/*
 * This is based on the x86 code accompanying "Using the KVM API"
 * (https://lwn.net/Articles/658511/).
 *
 * Original x86 code in the file kvmtest.c and https://lwn.net/Articles/658512/.
 *
 * Copyright (C) 2022 Google LLC
 * Author: Fuad Tabba <tabba@google.com>
 */

/* Sample code for /dev/kvm API
 *
 * Copyright (c) 2015 Intel Corporation
 * Author: Josh Triplett <josh@joshtriplett.org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */
#define _GNU_SOURCE

#include <err.h>
#include <fcntl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>

#define MFD_INACCESSIBLE  0x0008U
#define F_SEAL_AUTO_ALLOCATE	0x0020  /* prevent allocation for writes */

#define F_SET_INACCESSIBLE	(F_SET_FILE_RW_HINT + 1)
#define F_SET_UNMOVABLE	        (F_SET_FILE_RW_HINT + 2)
#define F_SET_UNRECLAIMABLE	(F_SET_FILE_RW_HINT + 3)

#define KVM_EXIT_MEMORY_FAULT     36

struct kvm_userspace_memory_region_ext {
        struct kvm_userspace_memory_region region;
        __u64 private_offset;
        __u32 private_fd;
        __u32 pad1;
        __u64 pad2[14];
};

#define KVM_MEM_PRIVATE		(1UL << 2)


int main(void)
{
	int kvm, vmfd, vcpufd, code_fd, ret, i;

	/* Add x0 to x1 and outputs the result to MMIO at address in x2. */
	const uint8_t code[] = {
		0x20, 0x00, 0x00, 0x8b, /* add x0, x1, x0 */
		0x40, 0x00, 0x00, 0xf9, /* str x0, [x2]*/
		0x00, 0x00, 0x20, 0xd4, /* brk */
	};
	const uint64_t code_address = 0x1000;
	const uint64_t mmio_address = 0x2000;
	uint8_t *mem_code = NULL;
	const size_t code_size = 0x1000;
	size_t mmap_size;
	struct kvm_run *run = NULL;
	struct kvm_enc_region range;

	printf("kvmtest-fd\n");

	kvm = open("/dev/kvm", O_RDWR | O_CLOEXEC);
	if (kvm < 0)
		err(1, "/dev/kvm");

	/* Ensure this is the stable version of the KVM API (defined as 12) */
	ret = ioctl(kvm, KVM_GET_API_VERSION, NULL);
	if (ret < 0)
		err(1, "KVM_GET_API_VERSION");
	if (ret != 12)
		errx(1, "KVM_GET_API_VERSION %d, expected 12", ret);

	vmfd = ioctl(kvm, KVM_CREATE_VM, (unsigned long)0);
	if (vmfd < 0)
		err(1, "KVM_CREATE_VM");

	code_fd = memfd_create("memfd.txt", 0 /* MFD_INACCESSABLE IN THE FUTURE */);
	if (!code_fd)
		err(1, "memfd_create");

	/* Ensure that guest memory won't be migrated or paged out. */
        ret = fcntl(code_fd, F_SET_UNMOVABLE);
	if (ret)
		err(ret, "F_SET_UNMOVABLE");

	ret = fcntl(code_fd, F_SET_UNRECLAIMABLE);
	if (ret)
		err(ret, "F_SET_UNRECLAIMABLE");

	/* Allocate one aligned page of guest memory to hold the code. */
	ret = fallocate(code_fd, 0, 0, code_size);
	if (ret)
		err(1, "fallocate");

	/* Map the page temporarily to initialize it. */
	mem_code = mmap(NULL, code_size, PROT_READ | PROT_WRITE, MAP_SHARED, code_fd, 0);
	if (!mem_code)
		err(1, "mmap");

	memcpy(mem_code, code, sizeof(code));

	/* Unmap the page and then ensure that it is no longer mapable. */
	ret = munmap(mem_code, code_size);
	if (ret)
		err(ret, "munmap");

	mem_code = 0;

	ret = fcntl(code_fd, F_SET_INACCESSIBLE);
	if (ret)
		err(ret, "F_SET_INACCESSIBLE");

	/* Map code memory to the second page frame. */
	struct kvm_userspace_memory_region_ext region = {
		.region = {
			.slot = 0,
			.guest_phys_addr = code_address,
			.memory_size = code_size,
			.userspace_addr = (uint64_t)mem_code,
			.flags = KVM_MEM_PRIVATE,
		},
		.private_fd = code_fd,
		.private_offset = 0,
	};
	ret = ioctl(vmfd, KVM_SET_USER_MEMORY_REGION, &region);
	if (ret < 0)
		err(1, "KVM_SET_USER_MEMORY_REGION code");

	/* Inform KVM that the region is protected. */
	range.addr = (__u64) code_address;
	range.size = code_size;
	ret = ioctl(vmfd, KVM_MEMORY_ENCRYPT_REG_REGION, &range);
	if (ret)
		err(ret, "KVM_MEMORY_ENCRYPT_REG_REGION");

	/* Use third page frame of guest memory to simulate MMIO. */
	region.region.flags = KVM_MEM_READONLY; /* triggers KVM_EXIT_MEMIO on write */
	region.region.slot = 1;
	region.region.guest_phys_addr = mmio_address;
	region.region.userspace_addr = 0ULL;
	region.private_fd = 0;
	ret = ioctl(vmfd, KVM_SET_USER_MEMORY_REGION, &region);
	if (ret < 0)
		err(1, "KVM_SET_USER_MEMORY_REGION mmio");

	/* Create one CPU to run in the VM. */
	vcpufd = ioctl(vmfd, KVM_CREATE_VCPU, (unsigned long)0);
	if (vcpufd < 0)
		err(1, "KVM_CREATE_VCPU");

	/* Map the shared kvm_run structure and following data. */
	ret = ioctl(kvm, KVM_GET_VCPU_MMAP_SIZE, NULL);
	if (ret < 0)
		err(1, "KVM_GET_VCPU_MMAP_SIZE");
	mmap_size = ret;
	if (mmap_size < sizeof(*run))
		errx(1, "KVM_GET_VCPU_MMAP_SIZE unexpectedly small");
	run = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, vcpufd, 0);
	if (!run)
		err(1, "mmap vcpu");

	/* Query KVM for preferred CPU target type that can be emulated. */
	struct kvm_vcpu_init vcpu_init;
	ret = ioctl(vmfd, KVM_ARM_PREFERRED_TARGET, &vcpu_init);
	if (ret < 0)
		err(1, "KVM_PREFERRED_TARGET");

	/* Initialize VCPU with the preferred type obtained above. */
	ret = ioctl(vcpufd, KVM_ARM_VCPU_INIT, &vcpu_init);
	if (ret < 0)
		err(1, "KVM_ARM_VCPU_INIT");

	/* Prepare the kvm_one_reg structure to use for populating registers. */
	uint64_t reg_data;
	struct kvm_one_reg reg;
	reg.addr = (__u64)&reg_data;

	// Initialize input registers (x0 and x1) to 2.
	reg_data = 2;
	reg.id = 0x6030000000100000; // x0 id
	ret = ioctl(vcpufd, KVM_SET_ONE_REG, &reg);
	if (ret != 0)
		err(1, "KVM_SET_ONE_REG");
	reg.id = 0x6030000000100002; // x1 id
	ret = ioctl(vcpufd, KVM_SET_ONE_REG, &reg);
	if (ret != 0)
		err(1, "KVM_SET_ONE_REG");

	// Initialize x3 to point to the simulated MMIO region.
	reg.id = 0x6030000000100004; // x3 id
	reg_data = mmio_address;
	ret = ioctl(vcpufd, KVM_SET_ONE_REG, &reg);
	if (ret != 0)
		err(1, "KVM_SET_ONE_REG");

	// Initialize the PC to point to the start of the code.
	reg.id = 0x6030000000100040; // pc id
	reg_data = code_address;
	ret = ioctl(vcpufd, KVM_SET_ONE_REG, &reg);
	if (ret != 0)
		err(1, "KVM_SET_ONE_REG");

	// Enable debug so that brk instruction would exit KVM_RUN (KVM_EXIT_DEBUG).
	struct kvm_guest_debug debug = {
		.control = KVM_GUESTDBG_ENABLE,
	};
	ret = ioctl(vcpufd, KVM_SET_GUEST_DEBUG, &debug);
	if (ret < 0)
		err(1, "KVM_SET_GUEST_DEBUG");

	/* Repeatedly run code and handle VM exits. */
	for (i = 0;; i++)
	{
		printf("KVM_RUN %d\n", i);

		ret = ioctl(vcpufd, KVM_RUN, NULL);
		if (ret < 0)
			err(1, "KVM_RUN");
		switch (run->exit_reason)
		{
		case KVM_EXIT_DEBUG:
			puts("KVM_EXIT_DEBUG");
			return 0;
		case KVM_EXIT_MMIO:
		{
			uint64_t payload = *(uint64_t *)(run->mmio.data); /* sorry */
			printf("KVM_EXIT_MMIO: addr = 0x%llx, len = %u, is_write = %u, data = 0x%08llx\n",
				   run->mmio.phys_addr, run->mmio.len, run->mmio.is_write,
				   payload);
			break;
		}
		case KVM_EXIT_FAIL_ENTRY:
			errx(1, "KVM_EXIT_FAIL_ENTRY: hardware_entry_failure_reason = 0x%llx",
				 (unsigned long long)run->fail_entry.hardware_entry_failure_reason);
		case KVM_EXIT_INTERNAL_ERROR:
			errx(1, "KVM_EXIT_INTERNAL_ERROR: suberror = 0x%x",
				 run->internal.suberror);
		case KVM_EXIT_MEMORY_FAULT:
			err(1, "KVM_EXIT_MEMORY_FAULT");
		default:
			errx(1, "exit_reason = 0x%x", run->exit_reason);
		}
	}
}