// Physical memory allocator, for user processes,
// kernel stacks, page-table pages,
// and pipe buffers. Allocates whole 4096-byte pages.

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

void freerange(void *pa_start, void *pa_end);

extern char end[]; // first address after kernel.
                   // defined by kernel.ld.

struct run {
  struct run *next;
};

struct {
  struct spinlock lock;
  struct run *freelist;
} kmem;

struct super_run {
  struct super_run *next;
};

struct {
  struct spinlock lock;
  struct super_run *freelist;
} skmem;

void superfree(void *pa) {
  struct super_run *r;

  if(((uint64)pa % SUPERPGSIZE) != 0 || (char*)pa < end || (uint64)pa >= PHYSTOP)
    panic("superfree");

  // Fill with junk to catch dangling refs.
  memset(pa, 1, SUPERPGSIZE);

  r = (struct super_run *)pa;
  acquire(&skmem.lock);
  r->next = skmem.freelist;
  skmem.freelist = r;
  release(&skmem.lock);
}

void* superalloc() {
  struct super_run *r;
  acquire(&skmem.lock);
  r = skmem.freelist;
  if(r) skmem.freelist = r->next;
  release(&skmem.lock);
  if(r) memset((void*)r, 0, SUPERPGSIZE);
  return (void*)r;
}

void
kinit()
{
  initlock(&kmem.lock, "kmem");
  initlock(&skmem.lock, "skmem");
  freerange(end, (void*)PHYSTOP);
}

void
freerange(void *pa_start, void *pa_end)
{
  char *p;
  p = (char*)PGROUNDUP((uint64)pa_start);
  for(; p + PGSIZE <= (char*)pa_end - 12 * 1024 * 1024; p += PGSIZE) //留5个巨页
    kfree(p);
  
  p = (char*)SUPERPGROUNDUP((uint64)p);
  for (; p + SUPERPGSIZE <= (char *)pa_end; p += SUPERPGSIZE) {
    superfree(p);
  }
}
// void
// freerange(void *pa_start, void *pa_end)
// {
//   char *p;
//   p = (char*)PGROUNDUP((uint64)pa_start);
//   for(; p + PGSIZE <= (char*)pa_end; p += PGSIZE)
//     kfree(p);
// }

// Free the page of physical memory pointed at by pa,
// which normally should have been returned by a
// call to kalloc().  (The exception is when
// initializing the allocator; see kinit above.)
void
kfree(void *pa)
{
  struct run *r;

  if(((uint64)pa % PGSIZE) != 0 || (char*)pa < end || (uint64)pa >= PHYSTOP)
    panic("kfree");

  // Fill with junk to catch dangling refs.
  memset(pa, 1, PGSIZE);

  r = (struct run*)pa;

  acquire(&kmem.lock);
  r->next = kmem.freelist;
  kmem.freelist = r;
  release(&kmem.lock);
}

// Allocate one 4096-byte page of physical memory.
// Returns a pointer that the kernel can use.
// Returns 0 if the memory cannot be allocated.
void *
kalloc(void)
{
  struct run *r;

  acquire(&kmem.lock);
  r = kmem.freelist;
  if(r)
    kmem.freelist = r->next;
  release(&kmem.lock);

  if(r)
    memset((char*)r, 5, PGSIZE); // fill with junk
  return (void*)r;
}