How to get XNU kernel vm address and its size

kext_get_kern_vm_addr.c

#include <mach/mach_types.h>
#include <mach/mach_vm.h>
#include <libkern/libkern.h>

extern vm_map_t kernel_map; /* exported com.apple.kpi.unsupported */

#define UNUSED(arg0, ...) (void) ((void) arg0, ##__VA_ARGS__)

/*
 * see:
 *  keywords: image
 *  xnu/osfmk/vm/vm_user.c#mach_vm_region
 *  xnu/bsd/kern/kern_core.c#coredump
 *  xnu/bsd/kern/mach_loader.c#parse_machfile
 */
kern_return_t kext_start(kmod_info_t *ki, void *d)
{
    kern_return_t e;
    mach_vm_address_t addr;
    mach_vm_size_t size;
    vm_region_top_info_data_t idata;
    mach_msg_type_number_t cnt = VM_REGION_BASIC_INFO_COUNT_64;

    UNUSED(ki, d);

    e = mach_vm_region(kernel_map, &addr, &size,
                        VM_REGION_TOP_INFO, (vm_region_info_t) &idata,
                        &cnt, NULL);

    UNUSED(idata, cnt);

    if (e == 0) {
        printf("@ kernel_map  addr: %#018llx size: %#018llx\n", addr, size);
    } else {
        printf("@ mach_vm_region() failure  errno: %d\n", e);
    }

    return KERN_SUCCESS;
}

Sample output:
@ kernel_map addr: 0xffffff803cc78000 size: 0x0000000180000000