Update memory.c

linux/mm/memory.c

@@ -147,7 +147,7 @@ int free_page_tables(unsigned long from,unsigned long size)
  * 1 Mb-range, so the pages can be shared with the kernel. Thus the
  * special case for nr=xxxx.
  */
-int copy_page_tables(unsigned long from,unsigned long to,long size)
+int copy_page_tables(unsigned long from,unsigned long to,long size )
 {
 	unsigned long * from_page_table;
 	unsigned long * to_page_table;
@@ -809,3 +809,160 @@ mytag:
 
 
 
+/*
+	直接让esp（子进程）指向另一个进程（当前进程）的地址；
+	修改eip对应的指令，改为ret 0xec8353c3  ps:应该只有0xc3有用
+	由于eip只执行一条指令，我们将eip指向栈，将ret压入栈即可；
+	在这里我们只实现了int (*fn)(void *) 一种函数类型，并且要求fn内以exit结尾
+	于是我们只需修改八字节即可；
+	下面写的不对，不能指向另一个进程的地址，只能修改物理页了。
+*/
+/* int do_clone(int nr,long tmp,int (*fn)(void *), void *child_stack, int flag) 
+{
+	//设置压栈表，方便操作；
+	long stack[1024];
+	unsigned long len=0;
+	task[nr]->tss.esp=(unsigned long) child_stack - 8;
+	stack[0] = (unsigned long) fn;
+	task[nr]->tss.eip = (unsigned long) child_stack - 4;
+	stack[1]= 0xec8353c3;
+	//栈区赋值；
+	len = 8;
+	char *p1=stack ,*p2=(char *)((unsigned long)child_stack-len);
+	while(len--)
+		put_fs_byte(*(p1++),p2++);
+	return 0;
+} */
+/*  child_stack-4 00 00 00 00 */																
+	/*  child_stack-8 00 00 00 00 */
+	/*  child_stack-12 arg */
+	/*  child_stack-16 fn */		//esp
+	/*  child_stack-20 00 00 00 00 */
+	/*  child_stack-24 00 00 00 00 */
+	/*  child_stack-28 00 00 00 00 */
+	/*  child_stack-32 0x000000c3 */
+/*
+int do_clone(int nr,long tmp,int (*fn)(void *), void *child_stack, int flag) 
+{
+	void * argv =NULL;
+	//共享物理页：写法有缺陷，可能child——stack跨页
+	//子进程task[nr]的页表项获取，目的是更新成child——stacK的物理页
+	unsigned long nrfrom_page,nrfrom,from_page,from,tpage,address;
+	address = task[nr]->tss.esp;
+	nrfrom_page =  ((address>>20) & 0xffc);
+	nrfrom_page += ((task[nr]->start_code>>20) & 0xffc);//页目录
+	nrfrom=*(unsigned long *)nrfrom_page;	//页表项
+	if(!(nrfrom&1)) //无页表项分配一个
+	{
+		if(!(tpage=get_free_page()))
+		{
+			printk("out of memory.\n");
+			return -1;
+		}
+		else
+			{
+				*(unsigned long *)nrfrom_page= tpage | 7;
+				mem_map[(tpage-LOW_MEM)>>12]++;
+			}
+	}	
+	nrfrom &= 0xfffff000;
+	nrfrom_page = nrfrom + ((address>>10) & 0xffc);
+
+	//获取child_stack的物理页,并将其复制给task[nr];
+	address=(unsigned long) child_stack;
+	from_page =  ((address>>20) & 0xffc);
+	from_page += ((current->start_code>>20) & 0xffc);//页目录
+	if(!(*(unsigned long *)from_page&1))  //页表项不存在，申请页面
+		if(!(tpage=get_free_page()))
+		{
+			printk("out of memory.\n");
+			return -1;
+		}
+		else
+			{
+				*(unsigned long *)from_page= tpage | 7;
+				mem_map[(tpage-LOW_MEM)>>12]++;
+			}
+	from=*(unsigned long *)from_page;	//页表项
+	from &= 0xfffff000;
+	from_page = from + ((address>>10) & 0xffc);
+	if(!(*(unsigned long *)from_page & 1))	//物理页不存在
+		if(!(tpage=get_free_page()))
+		{
+			printk("out of memory.\n");
+			return -1;
+		}
+		else
+		{
+			*(unsigned long *)from_page= tpage | 7; 
+			mem_map[(tpage-LOW_MEM)>>12]++;
+		}
+	//复制给nr
+	*(unsigned long *)nrfrom_page = *(unsigned long *)from_page;
+	unsigned long stack[128];
+	unsigned long off=(unsigned long)child_stack & 0xfff;
+	if(off < 32) 
+	{
+		printk("地址跨页,我也没办法.\n");
+		return -1;
+	}
+		
+ 	//更新esp,让其指向child_stack同样偏移的地点;					
+	//注意：这里child_stack 指向的是高地址，要向下面push.	
+	task[nr]->tss.esp &=0xfffff000;		
+	task[nr]->tss.esp |=off - 16;			
+	//eip 只有一条ret  //所以传进来的fn必须以exit结尾，不能return ,	
+	//因为我不会return这个玩意push ebp 又pop 啥的		
+	task[nr]->tss.eip &=0xfffff000;	
+	task[nr]->tss.eip |=off - 32;	
+	 //ret	eip
+
+	stack[0]=0x000000c3;
+	stack[4]=(unsigned long)fn;
+	stack[5]=(unsigned long)argv;									
+	char * p1=stack, *p2=(unsigned long) child_stack - 32,len=32;
+	while(len--)
+		put_fs_byte(*(p1++),p2++);
+	printk("nr:%d::fn:%x\n",nr,(unsigned long )fn);
+	return 0;
+}
+*/
+int copy_page_tables_clone(unsigned long from,unsigned long to,long size )
+{
+	unsigned long * from_page_table;
+	unsigned long * to_page_table;
+	unsigned long this_page;
+	unsigned long * from_dir, * to_dir;
+	unsigned long nr;
+
+	if ((from&0x3fffff) || (to&0x3fffff))
+		panic("copy_page_tables called with wrong alignment");
+	from_dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
+	to_dir = (unsigned long *) ((to>>20) & 0xffc);
+	size = ((unsigned) (size+0x3fffff)) >> 22;
+	for( ; size-->0 ; from_dir++,to_dir++) {
+		if (1 & *to_dir)
+			panic("copy_page_tables: already exist");
+		if (!(1 & *from_dir))
+			continue;
+		from_page_table = (unsigned long *) (0xfffff000 & *from_dir);
+		if (!(to_page_table = (unsigned long *) get_free_page()))
+			return -1;	/* Out of memory, see freeing */
+		*to_dir = ((unsigned long) to_page_table) | 7;
+		nr = (from==0)?0xA0:1024;
+		for ( ; nr-- > 0 ; from_page_table++,to_page_table++) {
+			this_page = *from_page_table;
+			if (!(1 & this_page))
+				continue;
+			*to_page_table = this_page;
+			if (this_page > LOW_MEM) {
+				*from_page_table = this_page;
+				this_page -= LOW_MEM;
+				this_page >>= 12;
+				mem_map[this_page]++;
+			}
+		}
+	}
+	invalidate();
+	return 0;
+}