From ad4b18f25b117b7dba529aca939bc77e9d338289 Mon Sep 17 00:00:00 2001 From: mp6sgfx3h <1610531619@qq.com> Date: Sat, 2 Jul 2022 00:19:52 +0800 Subject: [PATCH] ADD file via upload --- fork.c | 241 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 241 insertions(+) create mode 100644 fork.c diff --git a/fork.c b/fork.c new file mode 100644 index 0000000..effc165 --- /dev/null +++ b/fork.c @@ -0,0 +1,241 @@ +/* + * linux/kernel/fork.c + * + * (C) 1991 Linus Torvalds + */ + +/* + * 'fork.c' contains the help-routines for the 'fork' system call + * (see also system_call.s), and some misc functions ('verify_area'). + * Fork is rather simple, once you get the hang of it, but the memory + * management can be a bitch. See 'mm/mm.c': 'copy_page_tables()' + */ +#include + +#include +#include +#include +#include + +extern void write_verify(unsigned long address); + +long last_pid=0; + +void verify_area(void * addr,int size) +{ + unsigned long start; + + start = (unsigned long) addr; + size += start & 0xfff; + start &= 0xfffff000; + start += get_base(current->ldt[2]); + while (size>0) { + size -= 4096; + write_verify(start); + start += 4096; + } +} + +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; + + code_limit=get_limit(0x0f); + data_limit=get_limit(0x17); + old_code_base = get_base(current->ldt[1]); + old_data_base = get_base(current->ldt[2]); + if (old_data_base != old_code_base) + panic("We don't support separate I&D"); + if (data_limit < code_limit) + panic("Bad data_limit"); + new_data_base = new_code_base = nr * 0x4000000; + 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,flag)) { + free_page_tables(new_data_base,data_limit); + return -ENOMEM; + } + return 0; +} + +/* + * Ok, this is the main fork-routine. It copies the system process + * information (task[nr]) and sets up the necessary registers. It + * also copies the data segment in it's entirety. + */ +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) +{ + struct task_struct *p; + int i; + struct file *f; + + p = (struct task_struct *) get_free_page(); + if (!p) + return -EAGAIN; + task[nr] = p; + __asm__ volatile ("cld"); /* by wyj */ + *p = *current; /* NOTE! this doesn't copy the supervisor stack */ + p->state = TASK_UNINTERRUPTIBLE; + p->pid = last_pid; + p->father = current->pid; + p->counter = p->priority; + p->signal = 0; + p->alarm = 0; + p->leader = 0; /* process leadership doesn't inherit */ + p->utime = p->stime = 0; + p->cutime = p->cstime = 0; + p->start_time = jiffies; + p->tss.back_link = 0; + p->tss.esp0 = PAGE_SIZE + (long) p; + p->tss.ss0 = 0x10; + p->tss.eip = eip; + p->tss.eflags = eflags; + p->tss.eax = 0; + p->tss.ecx = ecx; + p->tss.edx = edx; + p->tss.ebx = ebx; + p->tss.esp = esp; + p->tss.ebp = ebp; + p->tss.esi = esi; + p->tss.edi = edi; + p->tss.es = es & 0xffff; + p->tss.cs = cs & 0xffff; + p->tss.ss = ss & 0xffff; + p->tss.ds = ds & 0xffff; + p->tss.fs = fs & 0xffff; + p->tss.gs = gs & 0xffff; + p->tss.ldt = _LDT(nr); + p->tss.trace_bitmap = 0x80000000; + if (last_task_used_math == current) + __asm__("clts ; fnsave %0"::"m" (p->tss.i387)); + if (copy_mem(nr,p,flag)) { + task[nr] = NULL; + free_page((long) p); + return -EAGAIN; + } + for (i=0; ifilp[i]) + f->f_count++; + if (current->pwd) + current->pwd->i_count++; + if (current->root) + current->root->i_count++; + if (current->executable) + current->executable->i_count++; + set_tss_desc(gdt+(nr<<1)+FIRST_TSS_ENTRY,&(p->tss)); + set_ldt_desc(gdt+(nr<<1)+FIRST_LDT_ENTRY,&(p->ldt)); + p->state = TASK_RUNNING; /* do this last, just in case */ + return last_pid; +} + +int find_empty_process(void) +{ + int i; + + repeat: + if ((++last_pid)<0) last_pid=1; + for(i=0 ; ipid == last_pid) goto repeat; + for(i=1 ; itss.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; +} +*/ \ No newline at end of file