text: #include <vmm.h>
  #include <sync.h>
  #include <string.h>
  #include <assert.h>
  #include <stdio.h>
  #include <error.h>
  #include <pmm.h>
  #include <x86.h>
  #include <swap.h>
  #include <kmalloc.h>
  
  /* 
    vmm design include two parts: mm_struct (mm) & vma_struct (vma)
    mm is the memory manager for the set of continuous virtual memory  
    area which have the same PDT. vma is a continuous virtual memory area.
    There a linear link list for vma & a redblack link list for vma in mm.
  ---------------
    mm related functions:
     golbal functions
       struct mm_struct * mm_create(void)
       void mm_destroy(struct mm_struct *mm)
       int do_pgfault(struct mm_struct *mm, uint32_t error_code, uintptr_t addr)
  --------------
    vma related functions:
     global functions
       struct vma_struct * vma_create (uintptr_t vm_start, uintptr_t vm_end,...)
       void insert_vma_struct(struct mm_struct *mm, struct vma_struct *vma)
       struct vma_struct * find_vma(struct mm_struct *mm, uintptr_t addr)
     local functions
       inline void check_vma_overlap(struct vma_struct *prev, struct vma_struct *next)
  ---------------
     check correctness functions
       void check_vmm(void);
       void check_vma_struct(void);
       void check_pgfault(void);
  */
  
  static void check_vmm(void);
  static void check_vma_struct(void);
  static void check_pgfault(void);
  
  // mm_create -  alloc a mm_struct & initialize it.
  struct mm_struct *
  mm_create(void) {
      struct mm_struct *mm = kmalloc(sizeof(struct mm_struct));
  
      if (mm != NULL) {
          list_init(&(mm->mmap_list));
          mm->mmap_cache = NULL;
          mm->pgdir = NULL;
          mm->map_count = 0;
  
          if (swap_init_ok) swap_init_mm(mm);
          else mm->sm_priv = NULL;
          
          set_mm_count(mm, 0);
          lock_init(&(mm->mm_lock));
      }    
      return mm;
  }
  
  // vma_create - alloc a vma_struct & initialize it. (addr range: vm_start~vm_end)
  struct vma_struct *
  vma_create(uintptr_t vm_start, uintptr_t vm_end, uint32_t vm_flags) {
      struct vma_struct *vma = kmalloc(sizeof(struct vma_struct));
  
      if (vma != NULL) {
          vma->vm_start = vm_start;
          vma->vm_end = vm_end;
          vma->vm_flags = vm_flags;
      }
      return vma;
  }
  
  
  // find_vma - find a vma  (vma->vm_start <= addr <= vma_vm_end)
  struct vma_struct *
  find_vma(struct mm_struct *mm, uintptr_t addr) {
      struct vma_struct *vma = NULL;
      if (mm != NULL) {
          vma = mm->mmap_cache;
          if (!(vma != NULL && vma->vm_start <= addr && vma->vm_end > addr)) {
                  bool found = 0;
                  list_entry_t *list = &(mm->mmap_list), *le = list;
                  while ((le = list_next(le)) != list) {
                      vma = le2vma(le, list_link);
                      if (vma->vm_start<=addr && addr < vma->vm_end) {
                          found = 1;
                          break;
                      }
                  }
                  if (!found) {
                      vma = NULL;
                  }
          }
          if (vma != NULL) {
              mm->mmap_cache = vma;
          }
      }
      return vma;
  }
  
  
  // check_vma_overlap - check if vma1 overlaps vma2 ?
  static inline void
  check_vma_overlap(struct vma_struct *prev, struct vma_struct *next) {
      assert(prev->vm_start < prev->vm_end);
      assert(prev->vm_end <= next->vm_start);
      assert(next->vm_start < next->vm_end);
  }
  
  
  // insert_vma_struct -insert vma in mm's list link
  void
  insert_vma_struct(struct mm_struct *mm, struct vma_struct *vma) {
      assert(vma->vm_start < vma->vm_end);
      list_entry_t *list = &(mm->mmap_list);
      list_entry_t *le_prev = list, *le_next;
  
          list_entry_t *le = list;
          while ((le = list_next(le)) != list) {
              struct vma_struct *mmap_prev = le2vma(le, list_link);
              if (mmap_prev->vm_start > vma->vm_start) {
                  break;
              }
              le_prev = le;
          }
  
      le_next = list_next(le_prev);
  
      /* check overlap */
      if (le_prev != list) {
          check_vma_overlap(le2vma(le_prev, list_link), vma);
      }
      if (le_next != list) {
          check_vma_overlap(vma, le2vma(le_next, list_link));
      }
  
      vma->vm_mm = mm;
      list_add_after(le_prev, &(vma->list_link));
  
      mm->map_count ++;
  }
  
  // mm_destroy - free mm and mm internal fields
  void
  mm_destroy(struct mm_struct *mm) {
      assert(mm_count(mm) == 0);
  
      list_entry_t *list = &(mm->mmap_list), *le;
      while ((le = list_next(list)) != list) {
          list_del(le);
          kfree(le2vma(le, list_link));  //kfree vma        
      }
      kfree(mm); //kfree mm
      mm=NULL;
  }
  
  int
  mm_map(struct mm_struct *mm, uintptr_t addr, size_t len, uint32_t vm_flags,
         struct vma_struct **vma_store) {
      uintptr_t start = ROUNDDOWN(addr, PGSIZE), end = ROUNDUP(addr + len, PGSIZE);
      if (!USER_ACCESS(start, end)) {
          return -E_INVAL;
      }
  
      assert(mm != NULL);
  
      int ret = -E_INVAL;
  
      struct vma_struct *vma;
      if ((vma = find_vma(mm, start)) != NULL && end > vma->vm_start) {
          goto out;
      }
      ret = -E_NO_MEM;
  
      if ((vma = vma_create(start, end, vm_flags)) == NULL) {
          goto out;
      }
      insert_vma_struct(mm, vma);
      if (vma_store != NULL) {
          *vma_store = vma;
      }
      ret = 0;
  
  out:
      return ret;
  }
  
  int
  dup_mmap(struct mm_struct *to, struct mm_struct *from) {
      assert(to != NULL && from != NULL);
      list_entry_t *list = &(from->mmap_list), *le = list;
      while ((le = list_prev(le)) != list) {
          struct vma_struct *vma, *nvma;
          vma = le2vma(le, list_link);
          nvma = vma_create(vma->vm_start, vma->vm_end, vma->vm_flags);
          if (nvma == NULL) {
              return -E_NO_MEM;
          }
  
          insert_vma_struct(to, nvma);
  
          bool share = 0;
          if (copy_range(to->pgdir, from->pgdir, vma->vm_start, vma->vm_end, share) != 0) {
              return -E_NO_MEM;
          }
      }
      return 0;
  }
  
  void
  exit_mmap(struct mm_struct *mm) {
      assert(mm != NULL && mm_count(mm) == 0);
      pde_t *pgdir = mm->pgdir;
      list_entry_t *list = &(mm->mmap_list), *le = list;
      while ((le = list_next(le)) != list) {
          struct vma_struct *vma = le2vma(le, list_link);
          unmap_range(pgdir, vma->vm_start, vma->vm_end);
      }
      while ((le = list_next(le)) != list) {
          struct vma_struct *vma = le2vma(le, list_link);
          exit_range(pgdir, vma->vm_start, vma->vm_end);
      }
  }
  
  bool
  copy_from_user(struct mm_struct *mm, void *dst, const void *src, size_t len, bool writable) {
      if (!user_mem_check(mm, (uintptr_t)src, len, writable)) {
          return 0;
      }
      memcpy(dst, src, len);
      return 1;
  }
  
  bool
  copy_to_user(struct mm_struct *mm, void *dst, const void *src, size_t len) {
      if (!user_mem_check(mm, (uintptr_t)dst, len, 1)) {
          return 0;
      }
      memcpy(dst, src, len);
      return 1;
  }
  
  // vmm_init - initialize virtual memory management
  //          - now just call check_vmm to check correctness of vmm
  void
  vmm_init(void) {
      check_vmm();
  }
  
  // check_vmm - check correctness of vmm
  static void
  check_vmm(void) {
      size_t nr_free_pages_store = nr_free_pages();
      
      check_vma_struct();
      check_pgfault();
  
      cprintf("check_vmm() succeeded.\n");
  }
  
  static void
  check_vma_struct(void) {
      size_t nr_free_pages_store = nr_free_pages();
  
      struct mm_struct *mm = mm_create();
      assert(mm != NULL);
  
      int step1 = 10, step2 = step1 * 10;
  
      int i;
      for (i = step1; i >= 1; i --) {
          struct vma_struct *vma = vma_create(i * 5, i * 5 + 2, 0);
          assert(vma != NULL);
          insert_vma_struct(mm, vma);
      }
  
      for (i = step1 + 1; i <= step2; i ++) {
          struct vma_struct *vma = vma_create(i * 5, i * 5 + 2, 0);
          assert(vma != NULL);
          insert_vma_struct(mm, vma);
      }
  
      list_entry_t *le = list_next(&(mm->mmap_list));
  
      for (i = 1; i <= step2; i ++) {
          assert(le != &(mm->mmap_list));
          struct vma_struct *mmap = le2vma(le, list_link);
          assert(mmap->vm_start == i * 5 && mmap->vm_end == i * 5 + 2);
          le = list_next(le);
      }
  
      for (i = 5; i <= 5 * step2; i +=5) {
          struct vma_struct *vma1 = find_vma(mm, i);
          assert(vma1 != NULL);
          struct vma_struct *vma2 = find_vma(mm, i+1);
          assert(vma2 != NULL);
          struct vma_struct *vma3 = find_vma(mm, i+2);
          assert(vma3 == NULL);
          struct vma_struct *vma4 = find_vma(mm, i+3);
          assert(vma4 == NULL);
          struct vma_struct *vma5 = find_vma(mm, i+4);
          assert(vma5 == NULL);
  
          assert(vma1->vm_start == i  && vma1->vm_end == i  + 2);
          assert(vma2->vm_start == i  && vma2->vm_end == i  + 2);
      }
  
      for (i =4; i>=0; i--) {
          struct vma_struct *vma_below_5= find_vma(mm,i);
          if (vma_below_5 != NULL ) {
             cprintf("vma_below_5: i %x, start %x, end %x\n",i, vma_below_5->vm_start, vma_below_5->vm_end); 
          }
          assert(vma_below_5 == NULL);
      }
  
      mm_destroy(mm);
  
      cprintf("check_vma_struct() succeeded!\n");
  }
  
  struct mm_struct *check_mm_struct;
  
  // check_pgfault - check correctness of pgfault handler
  static void
  check_pgfault(void) {
      size_t nr_free_pages_store = nr_free_pages();
  
      check_mm_struct = mm_create();
      assert(check_mm_struct != NULL);
  
      struct mm_struct *mm = check_mm_struct;
      pde_t *pgdir = mm->pgdir = boot_pgdir;
      assert(pgdir[0] == 0);
  
      struct vma_struct *vma = vma_create(0, PTSIZE, VM_WRITE);
      assert(vma != NULL);
  
      insert_vma_struct(mm, vma);
  
      uintptr_t addr = 0x100;
      assert(find_vma(mm, addr) == vma);
  
      int i, sum = 0;
      for (i = 0; i < 100; i ++) {
          *(char *)(addr + i) = i;
          sum += i;
      }
      for (i = 0; i < 100; i ++) {
          sum -= *(char *)(addr + i);
      }
      assert(sum == 0);
  
      page_remove(pgdir, ROUNDDOWN(addr, PGSIZE));
      free_page(pde2page(pgdir[0]));
      pgdir[0] = 0;
  
      mm->pgdir = NULL;
      mm_destroy(mm);
      check_mm_struct = NULL;
  
      assert(nr_free_pages_store == nr_free_pages());
  
      cprintf("check_pgfault() succeeded!\n");
  }
  //page fault number
  volatile unsigned int pgfault_num=0;
  
  /* do_pgfault - interrupt handler to process the page fault execption
   * @mm         : the control struct for a set of vma using the same PDT
   * @error_code : the error code recorded in trapframe->tf_err which is setted by x86 hardware
   * @addr       : the addr which causes a memory access exception, (the contents of the CR2 register)
   *
   * CALL GRAPH: trap--> trap_dispatch-->pgfault_handler-->do_pgfault
   * The processor provides ucore's do_pgfault function with two items of information to aid in diagnosing
   * the exception and recovering from it.
   *   (1) The contents of the CR2 register. The processor loads the CR2 register with the
   *       32-bit linear address that generated the exception. The do_pgfault fun can
   *       use this address to locate the corresponding page directory and page-table
   *       entries.
   *   (2) An error code on the kernel stack. The error code for a page fault has a format different from
   *       that for other exceptions. The error code tells the exception handler three things:
   *         -- The P flag   (bit 0) indicates whether the exception was due to a not-present page (0)
   *            or to either an access rights violation or the use of a reserved bit (1).
   *         -- The W/R flag (bit 1) indicates whether the memory access that caused the exception
   *            was a read (0) or write (1).
   *         -- The U/S flag (bit 2) indicates whether the processor was executing at user mode (1)
   *            or supervisor mode (0) at the time of the exception.
   */
  int
  do_pgfault(struct mm_struct *mm, uint32_t error_code, uintptr_t addr) {
      int ret = -E_INVAL;
      //try to find a vma which include addr
      struct vma_struct *vma = find_vma(mm, addr);
  
      pgfault_num++;
      //If the addr is in the range of a mm's vma?
      if (vma == NULL || vma->vm_start > addr) {
          cprintf("not valid addr %x, and  can not find it in vma\n", addr);
          goto failed;
      }
      //check the error_code
      switch (error_code & 3) {
      default:
              /* error code flag : default is 3 ( W/R=1, P=1): write, present */
      case 2: /* error code flag : (W/R=1, P=0): write, not present */
          if (!(vma->vm_flags & VM_WRITE)) {
              cprintf("do_pgfault failed: error code flag = write AND not present, but the addr's vma cannot write\n");
              goto failed;
          }
          break;
      case 1: /* error code flag : (W/R=0, P=1): read, present */
          cprintf("do_pgfault failed: error code flag = read AND present\n");
          goto failed;
      case 0: /* error code flag : (W/R=0, P=0): read, not present */
          if (!(vma->vm_flags & (VM_READ | VM_EXEC))) {
              cprintf("do_pgfault failed: error code flag = read AND not present, but the addr's vma cannot read or exec\n");
              goto failed;
          }
      }
      /* IF (write an existed addr ) OR
       *    (write an non_existed addr && addr is writable) OR
       *    (read  an non_existed addr && addr is readable)
       * THEN
       *    continue process
       */
      uint32_t perm = PTE_U;
      if (vma->vm_flags & VM_WRITE) {
          perm |= PTE_W;
      }
      addr = ROUNDDOWN(addr, PGSIZE);
  
      ret = -E_NO_MEM;
  
      pte_t *ptep=NULL;
      /*LAB3 EXERCISE 1: YOUR CODE
      * Maybe you want help comment, BELOW comments can help you finish the code
      *
      * Some Useful MACROs and DEFINEs, you can use them in below implementation.
      * MACROs or Functions:
      *   get_pte : get an pte and return the kernel virtual address of this pte for la
      *             if the PT contians this pte didn't exist, alloc a page for PT (notice the 3th parameter '1')
      *   pgdir_alloc_page : call alloc_page & page_insert functions to allocate a page size memory & setup
      *             an addr map pa<--->la with linear address la and the PDT pgdir
      * DEFINES:
      *   VM_WRITE  : If vma->vm_flags & VM_WRITE == 1/0, then the vma is writable/non writable
      *   PTE_W           0x002                   // page table/directory entry flags bit : Writeable
      *   PTE_U           0x004                   // page table/directory entry flags bit : User can access
      * VARIABLES:
      *   mm->pgdir : the PDT of these vma
      *
      */
  #if 0
      /*LAB3 EXERCISE 1: YOUR CODE*/
      ptep = ???              //(1) try to find a pte, if pte's PT(Page Table) isn't existed, then create a PT.
      if (*ptep == 0) {
                              //(2) if the phy addr isn't exist, then alloc a page & map the phy addr with logical addr
  
      }
      else {
      /*LAB3 EXERCISE 2: YOUR CODE
      * Now we think this pte is a  swap entry, we should load data from disk to a page with phy addr,
      * and map the phy addr with logical addr, trigger swap manager to record the access situation of this page.
      *
      *  Some Useful MACROs and DEFINEs, you can use them in below implementation.
      *  MACROs or Functions:
      *    swap_in(mm, addr, &page) : alloc a memory page, then according to the swap entry in PTE for addr,
      *                               find the addr of disk page, read the content of disk page into this memroy page
      *    page_insert ： build the map of phy addr of an Page with the linear addr la
      *    swap_map_swappable ： set the page swappable
      */
      /*
       * LAB5 CHALLENGE ( the implmentation Copy on Write)
  		There are 2 situlations when code comes here.
  		  1) *ptep & PTE_P == 1, it means one process try to write a readonly page. 
  		     If the vma includes this addr is writable, then we can set the page writable by rewrite the *ptep.
  		     This method could be used to implement the Copy on Write (COW) thchnology(a fast fork process method).
  		  2) *ptep & PTE_P == 0 & but *ptep!=0, it means this pte is a  swap entry.
  		     We should add the LAB3's results here.
       */
          if(swap_init_ok) {
              struct Page *page=NULL;
                                      //(1）According to the mm AND addr, try to load the content of right disk page
                                      //    into the memory which page managed.
                                      //(2) According to the mm, addr AND page, setup the map of phy addr <---> logical addr
                                      //(3) make the page swappable.
                                      //(4) [NOTICE]: you myabe need to update your lab3's implementation for LAB5's normal execution.
          }
          else {
              cprintf("no swap_init_ok but ptep is %x, failed\n",*ptep);
              goto failed;
          }
     }
  #endif
      ptep = get_pte(mm->pgdir, addr, 1);
      if (ptep  == NULL) {
          cprintf("get_pte in do_pgfault failed\n");
          goto failed;
      }
      
      if (*ptep == 0) { 
          struct Page* page=pgdir_alloc_page(mm->pgdir, addr, perm) ;
          if (page == NULL) {
              cprintf("pgdir_alloc_page in do_pgfault failed\n");
              goto failed;
          }
      } else {
          if(swap_init_ok) {
              struct Page *page=NULL;
              if ((ret = swap_in(mm, addr, &page)) != 0) {    // (1）According to the mm AND addr, try to load the content of right disk page
                                                              //    into the memory which page managed.
                  goto failed;
              }
              page_insert(mm->pgdir, page, addr, perm);       // (2) According to the mm, addr AND page, setup the map of phy addr <---> logical addr
              swap_map_swappable(mm, addr, page, 1);          // (3) make the page swappable.
              page->pra_vaddr = addr;
          } else {
              cprintf("no swap_init_ok but ptep is %x, failed\n",*ptep);
              goto failed;
          }
      }
     ret = 0;
  failed:
      return ret;
  }
  
  bool
  user_mem_check(struct mm_struct *mm, uintptr_t addr, size_t len, bool write) {
      if (mm != NULL) {
          if (!USER_ACCESS(addr, addr + len)) {
              return 0;
          }
          struct vma_struct *vma;
          uintptr_t start = addr, end = addr + len;
          while (start < end) {
              if ((vma = find_vma(mm, start)) == NULL || start < vma->vm_start) {
                  return 0;
              }
              if (!(vma->vm_flags & ((write) ? VM_WRITE : VM_READ))) {
                  return 0;
              }
              if (write && (vma->vm_flags & VM_STACK)) {
                  if (start < vma->vm_start + PGSIZE) { //check stack start & size
                      return 0;
                  }
              }
              start = vma->vm_end;
          }
          return 1;
      }
      return KERN_ACCESS(addr, addr + len);
  }
  
  