text: #include "types.h"
  #include "riscv.h"
  #include "defs.h"
  #include "date.h"
  #include "param.h"
  #include "memlayout.h"
  #include "spinlock.h"
  #include "sysinfo.h"
  #include "proc.h"
  
  uint64
  sys_exit(void)
  {
    int n;
    if(argint(0, &n) < 0)
      return -1;
    exit(n);
    return 0;  // not reached
  }
  
  uint64
  sys_getpid(void)
  {
    return myproc()->pid;
  }
  
  uint64
  sys_fork(void)
  {
    return fork();
  }
  
  uint64
  sys_wait(void)
  {
    uint64 p;
    if(argaddr(0, &p) < 0)
      return -1;
    return wait(p);
  }
  
  uint64
  sys_sbrk(void)
  {
    int addr;
    int n;
  
    if(argint(0, &n) < 0)
      return -1;
    addr = myproc()->sz;
    if(growproc(n) < 0)
      return -1;
    return addr;
  }
  
  uint64
  sys_sleep(void)
  {
    int n;
    uint ticks0;
  
    if(argint(0, &n) < 0)
      return -1;
    acquire(&tickslock);
    ticks0 = ticks;
    while(ticks - ticks0 < n){
      if(myproc()->killed){
        release(&tickslock);
        return -1;
      }
      sleep(&ticks, &tickslock);
    }
    release(&tickslock);
    return 0;
  }
  
  uint64
  sys_kill(void)
  {
    int pid;
  
    if(argint(0, &pid) < 0)
      return -1;
    return kill(pid);
  }
  
  // return how many clock tick interrupts have occurred
  // since start.
  uint64
  sys_uptime(void)
  {
    uint xticks;
  
    acquire(&tickslock);
    xticks = ticks;
    release(&tickslock);
    return xticks;
  }
  
  uint64 sys_trace(void) {
    int mask;
    if (argint(0, &mask) < 0) {
      return -1;
    }
  
    myproc()->trace_mask = mask;
  
    return 0;
  }
  
  uint64 sys_sysinfo(void) {
    uint64 addr;
    if (argaddr(0, &addr) < 0) {
      return -1;
    }
    struct sysinfo info;
    info.freemem = cnt_free_memory();
    info.nproc = cnt_free_procs();
    if(copyout(myproc()->pagetable, addr, (char *)&info, sizeof(info)) < 0) {
      return -1;
    }
    return 0;
  }
  