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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");
1.1.1.11! root 59: new_data_base = old_data_base;
! 60: new_code_base = old_code_base;
1.1.1.3 root 61: p->start_code = new_code_base;
1.1 root 62: set_base(p->ldt[1],new_code_base);
63: set_base(p->ldt[2],new_data_base);
1.1.1.11! root 64: return copy_page_tables(p);
1.1 root 65: }
66:
1.1.1.5 root 67: static int find_empty_process(void)
68: {
1.1.1.10 root 69: int i, task_nr;
70: int this_user_tasks = 0;
1.1.1.5 root 71:
1.1.1.10 root 72: repeat:
73: if ((++last_pid) & 0xffff0000)
74: last_pid=1;
75: for(i=0 ; i < NR_TASKS ; i++) {
76: if (!task[i])
77: continue;
78: if (task[i]->uid == current->uid)
79: this_user_tasks++;
80: if (task[i]->pid == last_pid || task[i]->pgrp == last_pid)
81: goto repeat;
82: }
83: if (this_user_tasks > MAX_TASKS_PER_USER && !suser())
84: return -EAGAIN;
85: /* Only the super-user can fill the last available slot */
86: task_nr = 0;
1.1.1.5 root 87: for(i=1 ; i<NR_TASKS ; i++)
88: if (!task[i])
1.1.1.10 root 89: if (task_nr)
90: return task_nr;
91: else
92: task_nr = i;
93: if (task_nr && suser())
94: return task_nr;
1.1.1.5 root 95: return -EAGAIN;
96: }
97:
1.1 root 98: /*
99: * Ok, this is the main fork-routine. It copies the system process
100: * information (task[nr]) and sets up the necessary registers. It
101: * also copies the data segment in it's entirety.
102: */
1.1.1.5 root 103: int sys_fork(long ebx,long ecx,long edx,
104: long esi, long edi, long ebp, long eax, long ds,
105: long es, long fs, long gs, long orig_eax,
1.1 root 106: long eip,long cs,long eflags,long esp,long ss)
107: {
108: struct task_struct *p;
1.1.1.5 root 109: int i,nr;
1.1 root 110: struct file *f;
111:
1.1.1.10 root 112: p = (struct task_struct *) get_free_page(GFP_KERNEL);
1.1 root 113: if (!p)
114: return -EAGAIN;
1.1.1.5 root 115: nr = find_empty_process();
116: if (nr < 0) {
117: free_page((unsigned long) p);
118: return nr;
119: }
1.1.1.3 root 120: task[nr] = p;
1.1 root 121: *p = *current; /* NOTE! this doesn't copy the supervisor stack */
1.1.1.10 root 122: p->wait.task = p;
123: p->wait.next = NULL;
1.1.1.3 root 124: p->state = TASK_UNINTERRUPTIBLE;
1.1.1.8 root 125: p->flags &= ~PF_PTRACED;
1.1 root 126: p->pid = last_pid;
1.1.1.10 root 127: if (p->pid > 1)
128: p->swappable = 1;
1.1.1.8 root 129: p->p_pptr = p->p_opptr = current;
1.1.1.7 root 130: p->p_cptr = NULL;
1.1.1.8 root 131: SET_LINKS(p);
1.1 root 132: p->counter = p->priority;
133: p->signal = 0;
1.1.1.8 root 134: p->it_real_value = p->it_virt_value = p->it_prof_value = 0;
135: p->it_real_incr = p->it_virt_incr = p->it_prof_incr = 0;
1.1 root 136: p->leader = 0; /* process leadership doesn't inherit */
137: p->utime = p->stime = 0;
138: p->cutime = p->cstime = 0;
1.1.1.6 root 139: p->min_flt = p->maj_flt = 0;
140: p->cmin_flt = p->cmaj_flt = 0;
1.1 root 141: p->start_time = jiffies;
142: p->tss.back_link = 0;
143: p->tss.esp0 = PAGE_SIZE + (long) p;
144: p->tss.ss0 = 0x10;
145: p->tss.eip = eip;
1.1.1.10 root 146: p->tss.eflags = eflags & 0xffffcfff; /* iopl is always 0 for a new process */
1.1 root 147: p->tss.eax = 0;
148: p->tss.ecx = ecx;
149: p->tss.edx = edx;
150: p->tss.ebx = ebx;
151: p->tss.esp = esp;
152: p->tss.ebp = ebp;
153: p->tss.esi = esi;
154: p->tss.edi = edi;
155: p->tss.es = es & 0xffff;
156: p->tss.cs = cs & 0xffff;
157: p->tss.ss = ss & 0xffff;
158: p->tss.ds = ds & 0xffff;
159: p->tss.fs = fs & 0xffff;
160: p->tss.gs = gs & 0xffff;
161: p->tss.ldt = _LDT(nr);
1.1.1.7 root 162: p->tss.trace_bitmap = offsetof(struct tss_struct,io_bitmap) << 16;
163: for (i = 0; i<IO_BITMAP_SIZE ; i++)
164: p->tss.io_bitmap[i] = ~0;
1.1 root 165: if (last_task_used_math == current)
1.1.1.4 root 166: __asm__("clts ; fnsave %0 ; frstor %0"::"m" (p->tss.i387));
1.1 root 167: if (copy_mem(nr,p)) {
1.1.1.3 root 168: task[nr] = NULL;
1.1.1.8 root 169: REMOVE_LINKS(p);
1.1 root 170: free_page((long) p);
171: return -EAGAIN;
172: }
173: for (i=0; i<NR_OPEN;i++)
174: if (f=p->filp[i])
175: f->f_count++;
176: if (current->pwd)
177: current->pwd->i_count++;
178: if (current->root)
179: current->root->i_count++;
1.1.1.3 root 180: if (current->executable)
181: current->executable->i_count++;
1.1.1.7 root 182: for (i=0; i < current->numlibraries ; i++)
183: if (current->libraries[i].library)
184: current->libraries[i].library->i_count++;
1.1 root 185: set_tss_desc(gdt+(nr<<1)+FIRST_TSS_ENTRY,&(p->tss));
186: set_ldt_desc(gdt+(nr<<1)+FIRST_LDT_ENTRY,&(p->ldt));
1.1.1.3 root 187: p->state = TASK_RUNNING; /* do this last, just in case */
1.1.1.5 root 188: return p->pid;
1.1 root 189: }
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