ucore-lab5

/* LAB5:EXERCISE1 YOUR CODE
 * should set tf_cs,tf_ds,tf_es,tf_ss,tf_esp,tf_eip,tf_eflags
 * NOTICE: If we set trapframe correctly, then the user level process can return to USER MODE from kernel. So
 *          tf_cs should be USER_CS segment (see memlayout.h)
 *          tf_ds=tf_es=tf_ss should be USER_DS segment
 *          tf_esp should be the top addr of user stack (USTACKTOP)
 *          tf_eip should be the entry point of this binary program (elf->e_entry)
 *          tf_eflags should be set to enable computer to produce Interrupt
 */
tf->tf_cs = USER_CS;
tf->tf_ds = tf->tf_es = tf->tf_ss = USER_DS;
tf->tf_esp = USTACKTOP;
tf->tf_eip = elf->e_entry;
tf->tf_eflags = FL_IF;
ret = 0;

related syscall for process:
SYS_exit        : process exit,                           -->do_exit
SYS_fork        : create child process, dup mm            -->do_fork-->wakeup_proc
SYS_wait        : wait process                            -->do_wait
SYS_exec        : after fork, process execute a program   -->load a program and refresh the mm
SYS_clone       : create child thread                     -->do_fork-->wakeup_proc
SYS_yield       : process flag itself need resecheduling, -- proc->need_sched=1, then scheduler will rescheule this process
SYS_sleep       : process sleep                           -->do_sleep 
SYS_kill        : kill process                            -->do_kill-->proc->flags |= PF_EXITING
                                                                 -->wakeup_proc-->do_wait-->do_exit   
SYS_getpid      : get the process's pid

/* LAB5:EXERCISE2 YOUR CODE
       * replicate content of page to npage, build the map of phy addr of nage with the linear addr start
       *
       * Some Useful MACROs and DEFINEs, you can use them in below implementation.
       * MACROs or Functions:
       *    page2kva(struct Page *page): return the kernel vritual addr of memory which page managed (SEE pmm.h)
       *    page_insert: build the map of phy addr of an Page with the linear addr la
       *    memcpy: typical memory copy function
       *
       * (1) find src_kvaddr: the kernel virtual address of page
       * (2) find dst_kvaddr: the kernel virtual address of npage
       * (3) memory copy from src_kvaddr to dst_kvaddr, size is PGSIZE
       * (4) build the map of phy addr of  nage with the linear addr start
       */
      void * kva_src = page2kva(page);
//找到src页面所在地址
      void * kva_dst = page2kva(npage);
		//找到dst页面所在地址
      memcpy(kva_dst, kva_src, PGSIZE);
//复制
      ret = page_insert(to, npage, start, perm);
//按照链表方式加入pte
      assert(ret == 0);
      }
      start += PGSIZE;

static int
init_main(void *arg) {
    //注意此句
    size_t nr_free_pages_store = nr_free_pages();
    size_t kernel_allocated_store = kallocated();

    int pid = kernel_thread(user_main, NULL, 0);
    if (pid <= 0) {
        panic("create user_main failed.\n");
    }
    //然而这里调用了do_wait,schedule,这两个函数调用了过多内存操作函数
    //具体我没有细看，但应该是这里出了问题
    while (do_wait(0, NULL) == 0) {
        schedule();
    }

    cprintf("all user-mode processes have quit.\n");
    assert(initproc->cptr == NULL && initproc->yptr == NULL && initproc->optr == NULL);
    assert(nr_process == 2);
    assert(list_next(&proc_list) == &(initproc->list_link));
    assert(list_prev(&proc_list) == &(initproc->list_link));
    //此时不再相等，故删去assert
    //assert(nr_free_pages_store == nr_free_pages());
    assert(kernel_allocated_store == kallocated());
    cprintf("init check memory pass.\n");
    return 0;
}

//nr_free_pages - call pmm->nr_free_pages to get the size (nr*PAGESIZE) 
//of current free memory
size_t
nr_free_pages(void) {
    size_t ret;
    bool intr_flag;
    local_intr_save(intr_flag);
    {
        ret = pmm_manager->nr_free_pages();
    }
    local_intr_restore(intr_flag);
    return ret;
}

//assert(nr_free_pages_store == nr_free_pages());

uint32_t perm = (*ptep & (PTE_U | PTE_P));
struct Page *page = pte2page(*ptep);
assert(page != NULL);
// 令新页面对父进程只读
page_insert(to, page, start, perm);
// 旧页面只读
page_insert(from, page, start, perm);

if (*ptep & PTE_P) {
	// Read-only possibly caused by COW.
    //确定可以写且可以更改
	if (vma->vm_flags & VM_WRITE) {
		// If ref of pages == 1, it is not shared, just make pte writable.
		// else, alloc a new page, copy content and reset pte.
		// also, remember to decrease ref of that page!
        //看佬的注释很容易明白
		struct Page* p = pte2page(*ptep);
		assert(p != NULL);
		assert(p->ref > 0);
		if (p->ref > 1) {
            //复制页面
			struct Page *npage = alloc_page();
			assert(npage != NULL);
			void * src_kvaddr = page2kva(p);
			void * dst_kvaddr = page2kva(npage);
			memcpy(dst_kvaddr, src_kvaddr, PGSIZE);
			// addr already ROUND down.
            //插入
			page_insert(mm->pgdir, npage, addr, ((*ptep) & PTE_USER) | PTE_W);
			// page_ref_dec(p);
            //
			cprintf("Handled one COW fault at %x: copied\n", addr);
		} else {
			page_insert(mm->pgdir, p, addr, ((*ptep) & PTE_USER) | PTE_W);
			cprintf("Handled one COW fault: reused\n");
		}
	} else {
		cprintf("Not a COW read-only fault.\n");
		goto failed;
	}
} else {
	// 处理缺页
}