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