syscall.c

#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "riscv.h"
#include "spinlock.h"
#include "proc.h"
#include "syscall.h"
#include "defs.h"

// Fetch the uint64 at addr from the current process.
int
fetchaddr(uint64 addr, uint64 *ip)
{
  struct proc *p = myproc();
  if(addr >= p->sz || addr+sizeof(uint64) > p->sz) // both tests needed, in case of overflow
    return -1;
  if(copyin(p->pagetable, (char *)ip, addr, sizeof(*ip)) != 0)
    return -1;
  return 0;
}

// Fetch the nul-terminated string at addr from the current process.
// Returns length of string, not including nul, or -1 for error.
int
fetchstr(uint64 addr, char *buf, int max)
{
  struct proc *p = myproc();
  if(copyinstr(p->pagetable, buf, addr, max) < 0)
    return -1;
  return strlen(buf);
}

static uint64
argraw(int n)
{
  struct proc *p = myproc();
  switch (n) {
  case 0:
    return p->trapframe->a0;
  case 1:
    return p->trapframe->a1;
  case 2:
    return p->trapframe->a2;
  case 3:
    return p->trapframe->a3;
  case 4:
    return p->trapframe->a4;
  case 5:
    return p->trapframe->a5;
  }
  panic("argraw");
  return -1;
}

// Fetch the nth 32-bit system call argument.
void
argint(int n, int *ip)
{
  *ip = argraw(n);
}

// Retrieve an argument as a pointer.
// Doesn't check for legality, since
// copyin/copyout will do that.
void
argaddr(int n, uint64 *ip)
{
  *ip = argraw(n);
}