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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>
14:
15: #include <linux/sched.h>
16: #include <linux/kernel.h>
17: #include <asm/segment.h>
18: #include <asm/system.h>
19:
20: extern void write_verify(unsigned long address);
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:
! 72: if ((++last_pid)<0) last_pid=1;
! 73: for(i=0 ; i<NR_TASKS ; i++)
! 74: if (task[i] && ((task[i]->pid == last_pid) ||
! 75: (task[i]->pgrp == last_pid)))
! 76: goto repeat;
! 77: for(i=1 ; i<NR_TASKS ; i++)
! 78: if (!task[i])
! 79: return i;
! 80: return -EAGAIN;
! 81: }
! 82:
1.1 root 83: /*
84: * Ok, this is the main fork-routine. It copies the system process
85: * information (task[nr]) and sets up the necessary registers. It
86: * also copies the data segment in it's entirety.
87: */
1.1.1.5 ! root 88: int sys_fork(long ebx,long ecx,long edx,
! 89: long esi, long edi, long ebp, long eax, long ds,
! 90: long es, long fs, long gs, long orig_eax,
1.1 root 91: long eip,long cs,long eflags,long esp,long ss)
92: {
93: struct task_struct *p;
1.1.1.5 ! root 94: int i,nr;
1.1 root 95: struct file *f;
96:
97: p = (struct task_struct *) get_free_page();
98: if (!p)
99: return -EAGAIN;
1.1.1.5 ! root 100: nr = find_empty_process();
! 101: if (nr < 0) {
! 102: free_page((unsigned long) p);
! 103: return nr;
! 104: }
1.1.1.3 root 105: task[nr] = p;
1.1 root 106: *p = *current; /* NOTE! this doesn't copy the supervisor stack */
1.1.1.3 root 107: p->state = TASK_UNINTERRUPTIBLE;
1.1 root 108: p->pid = last_pid;
109: p->counter = p->priority;
110: p->signal = 0;
111: p->alarm = 0;
112: p->leader = 0; /* process leadership doesn't inherit */
113: p->utime = p->stime = 0;
114: p->cutime = p->cstime = 0;
115: p->start_time = jiffies;
116: p->tss.back_link = 0;
117: p->tss.esp0 = PAGE_SIZE + (long) p;
118: p->tss.ss0 = 0x10;
119: p->tss.eip = eip;
120: p->tss.eflags = eflags;
121: p->tss.eax = 0;
122: p->tss.ecx = ecx;
123: p->tss.edx = edx;
124: p->tss.ebx = ebx;
125: p->tss.esp = esp;
126: p->tss.ebp = ebp;
127: p->tss.esi = esi;
128: p->tss.edi = edi;
129: p->tss.es = es & 0xffff;
130: p->tss.cs = cs & 0xffff;
131: p->tss.ss = ss & 0xffff;
132: p->tss.ds = ds & 0xffff;
133: p->tss.fs = fs & 0xffff;
134: p->tss.gs = gs & 0xffff;
135: p->tss.ldt = _LDT(nr);
136: p->tss.trace_bitmap = 0x80000000;
137: if (last_task_used_math == current)
1.1.1.4 root 138: __asm__("clts ; fnsave %0 ; frstor %0"::"m" (p->tss.i387));
1.1 root 139: if (copy_mem(nr,p)) {
1.1.1.3 root 140: task[nr] = NULL;
1.1 root 141: free_page((long) p);
142: return -EAGAIN;
143: }
144: for (i=0; i<NR_OPEN;i++)
145: if (f=p->filp[i])
146: f->f_count++;
147: if (current->pwd)
148: current->pwd->i_count++;
149: if (current->root)
150: current->root->i_count++;
1.1.1.3 root 151: if (current->executable)
152: current->executable->i_count++;
1.1.1.4 root 153: if (current->library)
154: current->library->i_count++;
1.1 root 155: set_tss_desc(gdt+(nr<<1)+FIRST_TSS_ENTRY,&(p->tss));
156: set_ldt_desc(gdt+(nr<<1)+FIRST_LDT_ENTRY,&(p->ldt));
1.1.1.4 root 157: p->p_pptr = current;
158: p->p_cptr = 0;
159: p->p_ysptr = 0;
160: p->p_osptr = current->p_cptr;
161: if (p->p_osptr)
162: p->p_osptr->p_ysptr = p;
163: current->p_cptr = p;
1.1.1.3 root 164: p->state = TASK_RUNNING; /* do this last, just in case */
1.1.1.5 ! root 165: return p->pid;
1.1 root 166: }
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