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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
1/*
2 * linux/arch/i386/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/random.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(struct mm_struct *mm)
40{
41 unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
42 unsigned long random_factor = 0;
43
44 if (current->flags & PF_RANDOMIZE)
45 random_factor = get_random_int() % (1024*1024);
46
47 if (gap < MIN_GAP)
48 gap = MIN_GAP;
49 else if (gap > MAX_GAP)
50 gap = MAX_GAP;
51
52 return PAGE_ALIGN(TASK_SIZE - gap - random_factor);
53}
54
55/*
56 * This function, called very early during the creation of a new
57 * process VM image, sets up which VM layout function to use:
58 */
59void arch_pick_mmap_layout(struct mm_struct *mm)
60{
61 /*
62 * Fall back to the standard layout if the personality
63 * bit is set, or if the expected stack growth is unlimited:
64 */
65 if (sysctl_legacy_va_layout ||
66 (current->personality & ADDR_COMPAT_LAYOUT) ||
67 current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) {
68 mm->mmap_base = TASK_UNMAPPED_BASE;
69 mm->get_unmapped_area = arch_get_unmapped_area;
70 mm->unmap_area = arch_unmap_area;
71 } else {
72 mm->mmap_base = mmap_base(mm);
73 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
74 mm->unmap_area = arch_unmap_area_topdown;
75 }
76}