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#include <string.h>
#include "filesys/file.h"
#include "userprog/process.h"
#include "threads/thread.h"
#include "threads/vaddr.h"
#include "threads/malloc.h"
#include "threads/palloc.h"
#include "vm/page.h"
static unsigned page_table_hash (const struct hash_elem *e, void *aux UNUSED);
static bool page_table_cmp_less (const struct hash_elem *a, const struct hash_elem *b,
void *aux UNUSED);
static void page_table_entry_free (struct hash_elem *e, void *aux UNUSED);
static bool page_table_insert (struct hash *ht, struct page_table_entry *pte);
/* initialize page table structure */
void
page_table_init (struct hash *ht)
{
hash_init (ht, page_table_hash, page_table_cmp_less, NULL);
}
/* calulcates and returns the hash used as key of the hash/page table */
static unsigned
page_table_hash (const struct hash_elem *e, void *aux UNUSED)
{
const struct page_table_entry *pte = hash_entry (e, struct page_table_entry, elem);
return hash_bytes (&pte->upage, sizeof pte->upage);
}
/* page table comperator needed by the hash table implementation.
returns true if A is less than B, or false if A is greater than
or equal to B */
static bool
page_table_cmp_less (const struct hash_elem *a, const struct hash_elem *b,
void *aux UNUSED)
{
const struct page_table_entry *pte1 = hash_entry (a, struct page_table_entry, elem);
const struct page_table_entry *pte2 = hash_entry (b, struct page_table_entry, elem);
return (pte1->upage < pte2->upage);
}
/* frees the content of page table */
void
page_table_free (struct hash *ht)
{
hash_destroy (ht, page_table_entry_free);
}
/* frees a single page table entry */
static void
page_table_entry_free (struct hash_elem *e, void *aux UNUSED)
{
struct page_table_entry *pte = hash_entry (e, struct page_table_entry, elem);
free (pte);
}
/* inserts a new entry into the page table.
returns false if entry is invalid or already in the table */
static bool
page_table_insert (struct hash *ht, struct page_table_entry *pte)
{
if (pte == NULL)
return false;
return (hash_insert (ht, &pte->elem) == NULL);
}
/* inserts a new entry of type segment into the page table.
returns false if entry is invalid or already in the table */
bool
page_table_insert_segment (struct hash *ht, struct file *file, off_t ofs,
void *upage, uint32_t read_bytes, bool writable)
{
struct page_table_entry *pte = malloc (sizeof *pte);
if (pte == NULL)
return false;
pte->upage = upage;
pte->loaded = false;
pte->segment.file = file;
pte->segment.ofs = ofs;
pte->segment.read_bytes = read_bytes;
pte->segment.writable = writable;
return page_table_insert (ht, pte);
}
/* fetch an entry from the page table. returns NULL if not found */
struct page_table_entry *
page_table_fetch (struct hash *ht, void *upage)
{
struct page_table_entry pte;
struct hash_elem *e;
pte.upage = upage;
e = hash_find (ht, &pte.elem);
return ((e != NULL) ? hash_entry (e, struct page_table_entry, elem) : NULL);
}
/* remove an entry from the page table. returns the element or NULL if not found.
the caller is responsible for freeing the element! */
struct page_table_entry *
page_table_remove (struct hash *ht, void *upage)
{
struct page_table_entry pte;
struct hash_elem *e;
pte.upage = upage;
e = hash_delete (ht, &pte.elem);
return ((e != NULL) ? hash_entry (e, struct page_table_entry, elem) : NULL);
}
/* load the page referenced by the page table entry.
returns true on success or already loaded, false otherwise */
bool
page_load (struct page_table_entry *pte)
{
struct segment *data;
if (pte->loaded)
return true;
data = &pte->segment;
file_seek (data->file, data->ofs);
/* Get a page of memory. */
uint8_t *kpage = palloc_get_page (PAL_USER);
if (kpage == NULL)
return false;
/* Load this page. */
if (file_read (data->file, kpage, data->read_bytes)
!= (int) data->read_bytes)
{
palloc_free_page (kpage);
return false;
}
memset (kpage + data->read_bytes, 0, PGSIZE - data->read_bytes);
/* Add the page to the process's address space. */
if (!process_install_page (pte->upage, kpage, data->writable))
{
palloc_free_page (kpage);
return false;
}
pte->loaded = true;
return true;
}
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