//拷贝父进程本身所占资源给子进程
static int32_t copy_process(struct task_struct* child_thread,struct task_struct* parent_thread){
//内核缓冲区，作为父进程用户空间的数据复制到子进程用户空间的中转
void* buf_page = get_kernel_pages(1);
if(buf_page == NULL){
return -1;
}
//a 复制父进程的pcb、虚拟地址位图、内核栈到子进程
if(copy_pcb_vaddrbitmap_stack0(child_thread,parent_thread) == -1){
return -1;
}
//b 为子进程创建页表，此页表仅包括内核空间
child_thread->pgdir = create_page_dir();
if(child_thread->pgdir == NULL){
return -1;
}
//c 复制父进程进程体及用户栈给子进程
copy_body_stack3(child_thread,parent_thread,buf_page);
//d 构建子进程thread_stack和修改返回值pid
build_child_stack(child_thread);
//e 更新文件inode的打开数
update_inode_open_cnts(child_thread);
mfree_page(PF_KERNEL,buf_page,1);
return 0;
}
//fork子进程，内核线程不可直接调用
pid_t sys_fork(void){
struct task_struct* parent_thread = running_thread();
struct task_struct* child_thread = get_kernel_pages(1); //为子进程创建pcb(task_struct结构)
if(child_thread == NULL){
return -1;
}
ASSERT(INTR_OFF == intr_get_status() && parent_thread->pgdir != NULL);
if(copy_process(child_thread,parent_thread) == -1){
return -1;
}
//添加到就绪线程队列和所有线程队列，子进程由调度器安排运行
ASSERT(!elem_find(&thread_ready_list,&child_thread->general_tag));
list_append(&thread_ready_list,&child_thread->general_tag);
ASSERT(!elem_find(&thread_all_list,&child_thread->all_list_tag));
list_append(&thread_all_list,&child_thread->all_list_tag);
return child_thread->pid;
}
/*
* get_kernel_page() - pin a kernel page in memory
* @start: starting kernel address
* @write: pinning for read/write, currently ignored
* @pages: array that receives pointer to the page pinned.
* Must be at least nr_segs long.
*
* Returns 1 if page is pinned. If the page was not pinned, returns
* -errno. The page returned must be released with a put_page() call
* when it is finished with.
*/
int get_kernel_page(unsigned long start, int write, struct page **pages)
{
const struct kvec kiov = {
.iov_base = (void *)start,
.iov_len = PAGE_SIZE
};
return get_kernel_pages(&kiov, 1, write, pages);
}
EXPORT_SYMBOL_GPL(get_kernel_page);
static void pagevec_lru_move_fn(struct pagevec *pvec,
void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
void *arg)
{
int i;
struct zone *zone = NULL;
struct lruvec *lruvec;
unsigned long flags = 0;
for (i = 0; i < pagevec_count(pvec); i++) {
struct page *page = pvec->pages[i];
struct zone *pagezone = page_zone(page);
if (pagezone != zone) {
if (zone)
spin_unlock_irqrestore(&zone->lru_lock, flags);
zone = pagezone;
spin_lock_irqsave(&zone->lru_lock, flags);
}
lruvec = mem_cgroup_page_lruvec(page, zone);
(*move_fn)(page, lruvec, arg);
}
if (zone)
spin_unlock_irqrestore(&zone->lru_lock, flags);
release_pages(pvec->pages, pvec->nr, pvec->cold);
pagevec_reinit(pvec);
}
//将父进程的pcb、虚拟地址位图拷贝给子进程
static int32_t copy_pcb_vaddrbitmap_stack0(struct task_struct* child_thread,struct task_struct* parent_thread){
//a 复制pcb所在的整个页，里面包含了进程pcb信息及特权0级栈，里面包含了返回地址，然后再单独修改个别部分
memcpy(child_thread,parent_thread,PG_SIZE);
child_thread->pid = fork_pid();
child_thread->elapsed_ticks = 0;
child_thread->status = TASK_READY;
child_thread->ticks = child_thread->priority; //为新进程把时间片充满
child_thread->parent_pid = parent_thread->pid;
child_thread->general_tag.prev = child_thread->general_tag.next = NULL;
child_thread->all_list_tag.prev = child_thread->all_list_tag.next = NULL;
block_desc_init(child_thread->u_block_desc);
//b 复制父进程的虚拟地址池的位图
uint32_t bitmap_pg_cnt = DIV_ROUND_UP((0xc0000000 - USER_VADDR_START) / PG_SIZE / 8,PG_SIZE);
void* vaddr_btmp = get_kernel_pages(bitmap_pg_cnt);
if(vaddr_btmp == NULL) return -1;
//此时child_thread->userprog_vaddr.vaddr_bitmap.bits还是指向父进程虚拟地址的位图地址
//下面将child_thread->userprog_vaddr.vaddr_bitmap.bits指向自己的位图vaddr_btmp
memcpy(vaddr_btmp,child_thread->userprog_vaddr.vaddr_bitmap.bits,bitmap_pg_cnt * PG_SIZE);
child_thread->userprog_vaddr.vaddr_bitmap.bits = vaddr_btmp;
//调试用
ASSERT(strlen(child_thread->name) < 11); //pcb.name的长度是16,为了避免下面strcat越界
strcat(child_thread->name,"_fork");
return 0;
}