/* * 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 <errno.h> #include <stddef.h> #include <linux/sched.h> #include <linux/kernel.h> #include <linux/mm.h> #include <asm/segment.h> #include <asm/system.h> 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) { printk("ldt[0]: %08x %08x\n",current->ldt[0].a,current->ldt[0].b); printk("ldt[1]: %08x %08x\n",current->ldt[1].a,current->ldt[1].b); printk("ldt[2]: %08x %08x\n",current->ldt[2].a,current->ldt[2].b); panic("We don't support separate I&D"); } if (data_limit < code_limit) panic("Bad data_limit"); new_data_base = new_code_base = nr * TASK_SIZE; 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; } static int find_empty_process(void) { int i; repeat: if ((++last_pid) & 0xffff0000) last_pid=1; for(i=0 ; i<NR_TASKS ; i++) if (task[i] && ((task[i]->pid == last_pid) || (task[i]->pgrp == last_pid))) goto repeat; for(i=1 ; i<NR_TASKS ; i++) if (!task[i]) return i; return -EAGAIN; } /* * 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 sys_fork(long ebx,long ecx,long edx, long esi, long edi, long ebp, long eax, long ds, long es, long fs, long gs, long orig_eax, long eip,long cs,long eflags,long esp,long ss) { struct task_struct *p; int i,nr; struct file *f; p = (struct task_struct *) get_free_page(); if (!p) return -EAGAIN; nr = find_empty_process(); if (nr < 0) { free_page((unsigned long) p); return nr; } task[nr] = p; *p = *current; /* NOTE! this doesn't copy the supervisor stack */ p->state = TASK_UNINTERRUPTIBLE; p->flags &= ~PF_PTRACED; p->pid = last_pid; p->p_pptr = p->p_opptr = current; p->p_cptr = NULL; SET_LINKS(p); p->counter = p->priority; p->signal = 0; p->it_real_value = p->it_virt_value = p->it_prof_value = 0; p->it_real_incr = p->it_virt_incr = p->it_prof_incr = 0; p->leader = 0; /* process leadership doesn't inherit */ p->utime = p->stime = 0; p->cutime = p->cstime = 0; p->min_flt = p->maj_flt = 0; p->cmin_flt = p->cmaj_flt = 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 = offsetof(struct tss_struct,io_bitmap) << 16; for (i = 0; i<IO_BITMAP_SIZE ; i++) p->tss.io_bitmap[i] = ~0; if (last_task_used_math == current) __asm__("clts ; fnsave %0 ; frstor %0"::"m" (p->tss.i387)); if (copy_mem(nr,p)) { task[nr] = NULL; REMOVE_LINKS(p); 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++; for (i=0; i < current->numlibraries ; i++) if (current->libraries[i].library) current->libraries[i].library->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 p->pid; }