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

struct proc proc[NPROC];
struct proc *initproc;

// helps ensure that wakeups of wait()ing
// parents are not lost. helps obey the
// memory model when using p->parent.
// must be acquired before any p->lock.
struct spinlock wait_lock;

struct proc *allocproc(void);

// a user program that calls exec("/init")
// assembled from ../user/initcode.S
// od -t xC ../user/initcode
uchar initcode[] = {
  0x17, 0x05, 0x00, 0x00, 0x13, 0x05, 0x45, 0x02,
  0x97, 0x05, 0x00, 0x00, 0x93, 0x85, 0x35, 0x02,
  0x93, 0x08, 0x70, 0x00, 0x73, 0x00, 0x00, 0x00,
  0x93, 0x08, 0x20, 0x00, 0x73, 0x00, 0x00, 0x00,
  0xef, 0xf0, 0x9f, 0xff, 0x2f, 0x69, 0x6e, 0x69,
  0x74, 0x00, 0x00, 0x24, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00
};

// Set up first user process.
void
userinit(void)
{
  struct proc *p;

  p = allocproc();
  initproc = p;
  
  // allocate one user page and copy initcode's instructions
  // and data into it.
  uvmfirst(p->pagetable, initcode, sizeof(initcode));
  p->sz = PGSIZE;

  // prepare for the very first "return" from kernel to user.
  p->trapframe->epc = 0;      // user program counter
  p->trapframe->sp = PGSIZE;  // user stack pointer

  p->cwd = namei("/");

  p->state = RUNNABLE;

  release(&p->lock);
}

// A fork child's very first scheduling by scheduler()
// will swtch to forkret.
void
forkret(void)
{
  static int first = 1;

  // Still holding p->lock from scheduler.
  release(&myproc()->lock);

  if (first) {
    // File system initialization must be run in the context of a
    // regular process (e.g., because it calls sleep), and thus cannot
    // be run from main().
    first = 0;
    fsinit(ROOTDEV);
  }

  usertrapret();
}