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1.1 root 1: /*
1.1.1.2 root 2: * linux/kernel/fork.c
3: *
1.1.1.10! root 4: * Copyright (C) 1991, 1992 Linus Torvalds
1.1.1.2 root 5: */
6:
7: /*
1.1 root 8: * 'fork.c' contains the help-routines for the 'fork' system call
9: * (see also system_call.s), and some misc functions ('verify_area').
10: * Fork is rather simple, once you get the hang of it, but the memory
11: * management can be a bitch. See 'mm/mm.c': 'copy_page_tables()'
12: */
13:
1.1.1.10! root 14: #include <linux/errno.h>
1.1 root 15: #include <linux/sched.h>
16: #include <linux/kernel.h>
1.1.1.9 root 17: #include <linux/mm.h>
1.1.1.10! root 18: #include <linux/stddef.h>
! 19:
1.1 root 20: #include <asm/segment.h>
21: #include <asm/system.h>
22:
1.1.1.10! root 23: #define MAX_TASKS_PER_USER ((NR_TASKS/4)*3)
! 24:
1.1 root 25: long last_pid=0;
26:
27: void verify_area(void * addr,int size)
28: {
29: unsigned long start;
30:
31: start = (unsigned long) addr;
32: size += start & 0xfff;
33: start &= 0xfffff000;
34: start += get_base(current->ldt[2]);
35: while (size>0) {
36: size -= 4096;
37: write_verify(start);
38: start += 4096;
39: }
40: }
41:
42: int copy_mem(int nr,struct task_struct * p)
43: {
44: unsigned long old_data_base,new_data_base,data_limit;
45: unsigned long old_code_base,new_code_base,code_limit;
46:
1.1.1.10! root 47: code_limit = get_limit(0x0f);
! 48: data_limit = get_limit(0x17);
1.1 root 49: old_code_base = get_base(current->ldt[1]);
50: old_data_base = get_base(current->ldt[2]);
1.1.1.5 root 51: if (old_data_base != old_code_base) {
52: printk("ldt[0]: %08x %08x\n",current->ldt[0].a,current->ldt[0].b);
53: printk("ldt[1]: %08x %08x\n",current->ldt[1].a,current->ldt[1].b);
54: printk("ldt[2]: %08x %08x\n",current->ldt[2].a,current->ldt[2].b);
1.1 root 55: panic("We don't support separate I&D");
1.1.1.5 root 56: }
1.1 root 57: if (data_limit < code_limit)
58: panic("Bad data_limit");
1.1.1.4 root 59: new_data_base = new_code_base = nr * TASK_SIZE;
1.1.1.3 root 60: p->start_code = new_code_base;
1.1 root 61: set_base(p->ldt[1],new_code_base);
62: set_base(p->ldt[2],new_data_base);
63: if (copy_page_tables(old_data_base,new_data_base,data_limit)) {
64: free_page_tables(new_data_base,data_limit);
65: return -ENOMEM;
66: }
67: return 0;
68: }
69:
1.1.1.5 root 70: static int find_empty_process(void)
71: {
1.1.1.10! root 72: int i, task_nr;
! 73: int this_user_tasks = 0;
1.1.1.5 root 74:
1.1.1.10! root 75: repeat:
! 76: if ((++last_pid) & 0xffff0000)
! 77: last_pid=1;
! 78: for(i=0 ; i < NR_TASKS ; i++) {
! 79: if (!task[i])
! 80: continue;
! 81: if (task[i]->uid == current->uid)
! 82: this_user_tasks++;
! 83: if (task[i]->pid == last_pid || task[i]->pgrp == last_pid)
! 84: goto repeat;
! 85: }
! 86: if (this_user_tasks > MAX_TASKS_PER_USER && !suser())
! 87: return -EAGAIN;
! 88: /* Only the super-user can fill the last available slot */
! 89: task_nr = 0;
1.1.1.5 root 90: for(i=1 ; i<NR_TASKS ; i++)
91: if (!task[i])
1.1.1.10! root 92: if (task_nr)
! 93: return task_nr;
! 94: else
! 95: task_nr = i;
! 96: if (task_nr && suser())
! 97: return task_nr;
1.1.1.5 root 98: return -EAGAIN;
99: }
100:
1.1 root 101: /*
102: * Ok, this is the main fork-routine. It copies the system process
103: * information (task[nr]) and sets up the necessary registers. It
104: * also copies the data segment in it's entirety.
105: */
1.1.1.5 root 106: int sys_fork(long ebx,long ecx,long edx,
107: long esi, long edi, long ebp, long eax, long ds,
108: long es, long fs, long gs, long orig_eax,
1.1 root 109: long eip,long cs,long eflags,long esp,long ss)
110: {
111: struct task_struct *p;
1.1.1.5 root 112: int i,nr;
1.1 root 113: struct file *f;
114:
1.1.1.10! root 115: p = (struct task_struct *) get_free_page(GFP_KERNEL);
1.1 root 116: if (!p)
117: return -EAGAIN;
1.1.1.5 root 118: nr = find_empty_process();
119: if (nr < 0) {
120: free_page((unsigned long) p);
121: return nr;
122: }
1.1.1.3 root 123: task[nr] = p;
1.1 root 124: *p = *current; /* NOTE! this doesn't copy the supervisor stack */
1.1.1.10! root 125: p->wait.task = p;
! 126: p->wait.next = NULL;
1.1.1.3 root 127: p->state = TASK_UNINTERRUPTIBLE;
1.1.1.8 root 128: p->flags &= ~PF_PTRACED;
1.1 root 129: p->pid = last_pid;
1.1.1.10! root 130: if (p->pid > 1)
! 131: p->swappable = 1;
1.1.1.8 root 132: p->p_pptr = p->p_opptr = current;
1.1.1.7 root 133: p->p_cptr = NULL;
1.1.1.8 root 134: SET_LINKS(p);
1.1 root 135: p->counter = p->priority;
136: p->signal = 0;
1.1.1.8 root 137: p->it_real_value = p->it_virt_value = p->it_prof_value = 0;
138: p->it_real_incr = p->it_virt_incr = p->it_prof_incr = 0;
1.1 root 139: p->leader = 0; /* process leadership doesn't inherit */
140: p->utime = p->stime = 0;
141: p->cutime = p->cstime = 0;
1.1.1.6 root 142: p->min_flt = p->maj_flt = 0;
143: p->cmin_flt = p->cmaj_flt = 0;
1.1 root 144: p->start_time = jiffies;
145: p->tss.back_link = 0;
146: p->tss.esp0 = PAGE_SIZE + (long) p;
147: p->tss.ss0 = 0x10;
148: p->tss.eip = eip;
1.1.1.10! root 149: p->tss.eflags = eflags & 0xffffcfff; /* iopl is always 0 for a new process */
1.1 root 150: p->tss.eax = 0;
151: p->tss.ecx = ecx;
152: p->tss.edx = edx;
153: p->tss.ebx = ebx;
154: p->tss.esp = esp;
155: p->tss.ebp = ebp;
156: p->tss.esi = esi;
157: p->tss.edi = edi;
158: p->tss.es = es & 0xffff;
159: p->tss.cs = cs & 0xffff;
160: p->tss.ss = ss & 0xffff;
161: p->tss.ds = ds & 0xffff;
162: p->tss.fs = fs & 0xffff;
163: p->tss.gs = gs & 0xffff;
164: p->tss.ldt = _LDT(nr);
1.1.1.7 root 165: p->tss.trace_bitmap = offsetof(struct tss_struct,io_bitmap) << 16;
166: for (i = 0; i<IO_BITMAP_SIZE ; i++)
167: p->tss.io_bitmap[i] = ~0;
1.1 root 168: if (last_task_used_math == current)
1.1.1.4 root 169: __asm__("clts ; fnsave %0 ; frstor %0"::"m" (p->tss.i387));
1.1 root 170: if (copy_mem(nr,p)) {
1.1.1.3 root 171: task[nr] = NULL;
1.1.1.8 root 172: REMOVE_LINKS(p);
1.1 root 173: free_page((long) p);
174: return -EAGAIN;
175: }
176: for (i=0; i<NR_OPEN;i++)
177: if (f=p->filp[i])
178: f->f_count++;
179: if (current->pwd)
180: current->pwd->i_count++;
181: if (current->root)
182: current->root->i_count++;
1.1.1.3 root 183: if (current->executable)
184: current->executable->i_count++;
1.1.1.7 root 185: for (i=0; i < current->numlibraries ; i++)
186: if (current->libraries[i].library)
187: current->libraries[i].library->i_count++;
1.1 root 188: set_tss_desc(gdt+(nr<<1)+FIRST_TSS_ENTRY,&(p->tss));
189: set_ldt_desc(gdt+(nr<<1)+FIRST_LDT_ENTRY,&(p->ldt));
1.1.1.3 root 190: p->state = TASK_RUNNING; /* do this last, just in case */
1.1.1.5 root 191: return p->pid;
1.1 root 192: }
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