#include <linux/linkage.h>
SYSCALL_DEFINE2(test_one, int, count, const char __user *, buf)
{
  char *p;
  printk("This is Syscall Test One.\n");  
  printk("buf addr is %p \n",buf);
  if(count > 1024)
  {
    printk("Your input str is too long.\n");
    return 1;
  }
  p = (char *)kmalloc(sizeof(char) * count, GFP_KERNEL);
  if(!copy_from_user(p, buf, count))
  {
    printk("input is %s \n", p);
  }
  kfree(p);
  return 1;
}
SYSCALL_DEFINE1(test_four, int, num)
{
  printk("This is Syscall Test Four.\n");
  printk("Four: Your input num is %d \n", num);
  return 1;
}

asmlinkage long sys_test_one(int count, const char __user *buf);
asmlinkage long sys_test_four(int num);

335 common  test_one    __x64_sys_test_one
338 common  test_four   __x64_sys_test_four

#include<stdio.h>
#include<unistd.h>
#include<string.h>
int main(int argc, char * argv[])
{
  long ret;
  char *buf = "335 syscall";
  printf("buf addr is %p \n", buf);
  ret = syscall(335, strlen(buf) + 1, buf);
  if (ret == 1) {
    printf("Syscall Succeed!\n");
  } else {
    printf("Syscall Failed!\n");
  }
  return 0;
}

#include<stdio.h>
#include<unistd.h>
int main(int argc, char * argv[])
{
  long ret;
  int num = 338;
  ret = syscall(338, num);
  if (ret == 1) {
    printf("Syscall Succeed!\n");
  } else {
    printf("Syscall Failed!\n");
  }
  return 0;
}