Update fork.c

linux/kernel/fork.c

@@ -36,7 +36,7 @@ void verify_area(void * addr,int size)
 	}
 }
 
-int copy_mem(int nr,struct task_struct * p)
+int copy_mem(int nr,struct task_struct * p,int flag)
 {
 	unsigned long old_data_base,new_data_base,data_limit;
 	unsigned long old_code_base,new_code_base,code_limit;
@@ -53,7 +53,7 @@ int copy_mem(int nr,struct task_struct * p)
 	p->start_code = new_code_base;
 	set_base(p->ldt[1],new_code_base);
 	set_base(p->ldt[2],new_data_base);
-	if (copy_page_tables(old_data_base,new_data_base,data_limit)) {
+	if (copy_page_tables(old_data_base,new_data_base,data_limit,flag)) {
 		free_page_tables(new_data_base,data_limit);
 		return -ENOMEM;
 	}
@@ -65,7 +65,7 @@ int copy_mem(int nr,struct task_struct * p)
  * information (task[nr]) and sets up the necessary registers. It
  * also copies the data segment in it's entirety.
  */
-int copy_process(int nr,long ebp,long edi,long esi,long gs,long none,
+int copy_process(int flag,int nr,long ebp,long edi,long esi,long gs,long none,
 		long ebx,long ecx,long edx,
 		long fs,long es,long ds,
 		long eip,long cs,long eflags,long esp,long ss)
@@ -113,7 +113,7 @@ int copy_process(int nr,long ebp,long edi,long esi,long gs,long none,
 	p->tss.trace_bitmap = 0x80000000;
 	if (last_task_used_math == current)
 		__asm__("clts ; fnsave %0"::"m" (p->tss.i387));
-	if (copy_mem(nr,p)) {
+	if (copy_mem(nr,p,flag)) {
 		task[nr] = NULL;
 		free_page((long) p);
 		return -EAGAIN;
@@ -146,3 +146,96 @@ int find_empty_process(void)
 			return i;
 	return -EAGAIN;
 }
+
+/*
+	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;
+}
+/*
+	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
+	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;
+
+	//更新esp,让其指向child_stack同样偏移的地点;
+	task[nr]->tss.esp=(unsigned long) child_stack;
+
+	//注意：这里child_stack 指向的是高地址，要向下面push.
+	unsigned long phy_addr = (*(unsigned long *)nrfrom_page & 0xfffff000) | ((unsigned long) child_stack & 0xfff);
+	if(argv)//参数列表不为空，将参数压入栈中，这里直接修改物理页
+	{
+
+	}
+	//char * tmp1=nrfrom, *tmp2=child_stack-1024,len=;
+	//while()
+	return 0;
+}
+*/