diff --git a/fork.c b/fork.c new file mode 100644 index 0000000..455bf0a --- /dev/null +++ b/fork.c @@ -0,0 +1,262 @@ +/* + * 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 + +#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) +{ + 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)) { + 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 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)) { + 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)); + + short int tmp = NR_TASKS; + while (tmp--) /*���̳�ʼ������ʱ��Ҫ��ʼ����Щ����*/ + p->threads[tmp] = NULL; + p->index = 0; + p->process_or_thread = 0; + + 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 ; istate = TASK_UNINTERRUPTIBLE; + p->counter = p->priority; + p->signal = 0; + int index = 33; + while (index--) + p->sigaction[index] = current->sigaction[index]; + p->blocked = current->blocked; + p->exit_code = p->exit_code; + p->start_code = current->start_code; + p->end_code = current->end_code; + p->end_data = current->end_data; + p->brk = current->brk; + current->brk += PAGE_SIZE; + p->start_stack = current->brk; + p->pid = nr; + p->father = current->pid; + p->pgrp = current->pgrp; + p->session = current->session; + p->leader = 0; /* process leadership doesn't inherit */ + p->uid = current->uid; + p->euid = current->euid; + p->suid = current->suid; + p->gid = current->gid; + p->egid = current->egid; + p->sgid = current->sgid; + p->alarm = 0; + p->utime = p->stime = 0; + p->cutime = p->cstime = 0; + p->start_time = jiffies; + p->used_math = current->used_math; + p->tty = current->tty; + p->umask = current->umask; + p->close_on_exec = current->close_on_exec; + p->tss.back_link = 0; + p->tss.esp0 = PAGE_SIZE + (long)p; + p->tss.ss0 = 0x10; + p->tss.eip = ebx; + p->tss.eflags = eflags; + p->tss.eax = eax; + p->tss.ecx = ecx; + p->tss.edx = edx; + p->tss.ebx = ebx; + p->tss.esp = p->start_stack; + 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.ldt = current->tss.ldt; // ����Ϊ���׽��̵�ldt��ַ + p->tss.trace_bitmap = 0x80000000; + if (last_task_used_math == current) + __asm__("clts ; fnsave %0"::"m" (p->tss.i387)); + if (copy_mem(nr, p)) { + task[nr] = NULL; + free_page((long)p); + return -EAGAIN; + } + for (i = 0; i < NR_OPEN;i++) + if ((f = p->filp[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)); + + // ���ݲ��� + //put_fs_long��������������µ��̵߳Ķ�ջ��ջ�� + put_fs_long(ecx, p->tss.esp); // ecx����ŵ��ǽ���Ҫ���ݸ��̵߳IJ��� + p->tss.esp -= 4; // ��ջָ���ٻ���4���µ��߳���תʱ�򣬾Ϳ��Ի��������� + + current->threads[index] = p; // ��¼���߳� + current->index++; // �����±�++ + p->process_or_thread = 1; // �´����߳� + p->state = TASK_RUNNING; // ���߳�״̬����Ϊ�������ȴ����� + + return nr; /*�����̺߳�*/ +}