1/*
2 *  linux/arch/s390/mm/mmap.c
3 *
4 *  flexible mmap layout support
5 *
6 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
7 * All Rights Reserved.
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17 * GNU General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
22 *
23 *
24 * Started by Ingo Molnar <mingo@elte.hu>
25 */
26
27#include <linux/personality.h>
28#include <linux/mm.h>
29#include <linux/module.h>
30
31/*
32 * Top of mmap area (just below the process stack).
33 *
34 * Leave an at least ~128 MB hole.
35 */
36#define MIN_GAP (128*1024*1024)
37#define MAX_GAP (TASK_SIZE/6*5)
38
39static inline unsigned long mmap_base(void)
40{
41	unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
42
43	if (gap < MIN_GAP)
44		gap = MIN_GAP;
45	else if (gap > MAX_GAP)
46		gap = MAX_GAP;
47
48	return TASK_SIZE - (gap & PAGE_MASK);
49}
50
51static inline int mmap_is_legacy(void)
52{
53#ifdef CONFIG_64BIT
54	/*
55	 * Force standard allocation for 64 bit programs.
56	 */
57	if (!test_thread_flag(TIF_31BIT))
58		return 1;
59#endif
60	return sysctl_legacy_va_layout ||
61	    (current->personality & ADDR_COMPAT_LAYOUT) ||
62	    current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY;
63}
64
65/*
66 * This function, called very early during the creation of a new
67 * process VM image, sets up which VM layout function to use:
68 */
69void arch_pick_mmap_layout(struct mm_struct *mm)
70{
71	/*
72	 * Fall back to the standard layout if the personality
73	 * bit is set, or if the expected stack growth is unlimited:
74	 */
75	if (mmap_is_legacy()) {
76		mm->mmap_base = TASK_UNMAPPED_BASE;
77		mm->get_unmapped_area = arch_get_unmapped_area;
78		mm->unmap_area = arch_unmap_area;
79	} else {
80		mm->mmap_base = mmap_base();
81		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
82		mm->unmap_area = arch_unmap_area_topdown;
83	}
84}
85EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
86