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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]);
48: if (old_data_base != old_code_base)
49: panic("We don't support separate I&D");
50: if (data_limit < code_limit)
51: panic("Bad data_limit");
52: new_data_base = new_code_base = nr * 0x4000000;
1.1.1.3 ! root 53: p->start_code = new_code_base;
1.1 root 54: set_base(p->ldt[1],new_code_base);
55: set_base(p->ldt[2],new_data_base);
56: if (copy_page_tables(old_data_base,new_data_base,data_limit)) {
57: free_page_tables(new_data_base,data_limit);
58: return -ENOMEM;
59: }
60: return 0;
61: }
62:
63: /*
64: * Ok, this is the main fork-routine. It copies the system process
65: * information (task[nr]) and sets up the necessary registers. It
66: * also copies the data segment in it's entirety.
67: */
68: int copy_process(int nr,long ebp,long edi,long esi,long gs,long none,
69: long ebx,long ecx,long edx,
70: long fs,long es,long ds,
71: long eip,long cs,long eflags,long esp,long ss)
72: {
73: struct task_struct *p;
74: int i;
75: struct file *f;
76:
77: p = (struct task_struct *) get_free_page();
78: if (!p)
79: return -EAGAIN;
1.1.1.3 ! root 80: task[nr] = p;
1.1 root 81: *p = *current; /* NOTE! this doesn't copy the supervisor stack */
1.1.1.3 ! root 82: p->state = TASK_UNINTERRUPTIBLE;
1.1 root 83: p->pid = last_pid;
84: p->father = current->pid;
85: p->counter = p->priority;
86: p->signal = 0;
87: p->alarm = 0;
88: p->leader = 0; /* process leadership doesn't inherit */
89: p->utime = p->stime = 0;
90: p->cutime = p->cstime = 0;
91: p->start_time = jiffies;
92: p->tss.back_link = 0;
93: p->tss.esp0 = PAGE_SIZE + (long) p;
94: p->tss.ss0 = 0x10;
95: p->tss.eip = eip;
96: p->tss.eflags = eflags;
97: p->tss.eax = 0;
98: p->tss.ecx = ecx;
99: p->tss.edx = edx;
100: p->tss.ebx = ebx;
101: p->tss.esp = esp;
102: p->tss.ebp = ebp;
103: p->tss.esi = esi;
104: p->tss.edi = edi;
105: p->tss.es = es & 0xffff;
106: p->tss.cs = cs & 0xffff;
107: p->tss.ss = ss & 0xffff;
108: p->tss.ds = ds & 0xffff;
109: p->tss.fs = fs & 0xffff;
110: p->tss.gs = gs & 0xffff;
111: p->tss.ldt = _LDT(nr);
112: p->tss.trace_bitmap = 0x80000000;
113: if (last_task_used_math == current)
1.1.1.3 ! root 114: __asm__("clts ; fnsave %0"::"m" (p->tss.i387));
1.1 root 115: if (copy_mem(nr,p)) {
1.1.1.3 ! root 116: task[nr] = NULL;
1.1 root 117: free_page((long) p);
118: return -EAGAIN;
119: }
120: for (i=0; i<NR_OPEN;i++)
121: if (f=p->filp[i])
122: f->f_count++;
123: if (current->pwd)
124: current->pwd->i_count++;
125: if (current->root)
126: current->root->i_count++;
1.1.1.3 ! root 127: if (current->executable)
! 128: current->executable->i_count++;
1.1 root 129: set_tss_desc(gdt+(nr<<1)+FIRST_TSS_ENTRY,&(p->tss));
130: set_ldt_desc(gdt+(nr<<1)+FIRST_LDT_ENTRY,&(p->ldt));
1.1.1.3 ! root 131: p->state = TASK_RUNNING; /* do this last, just in case */
1.1 root 132: return last_pid;
133: }
134:
135: int find_empty_process(void)
136: {
137: int i;
138:
139: repeat:
140: if ((++last_pid)<0) last_pid=1;
141: for(i=0 ; i<NR_TASKS ; i++)
142: if (task[i] && task[i]->pid == last_pid) goto repeat;
143: for(i=1 ; i<NR_TASKS ; i++)
144: if (!task[i])
145: return i;
146: return -EAGAIN;
147: }
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