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8817210d AK |
1 | /* |
2 | * linux/arch/x86_64/ia32/mm/mmap.c | |
3 | * | |
4 | * flexible mmap layout support | |
5 | * | |
6 | * Based on the i386 version which was | |
7 | * | |
8 | * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. | |
9 | * All Rights Reserved. | |
10 | * | |
11 | * This program is free software; you can redistribute it and/or modify | |
12 | * it under the terms of the GNU General Public License as published by | |
13 | * the Free Software Foundation; either version 2 of the License, or | |
14 | * (at your option) any later version. | |
15 | * | |
16 | * This program is distributed in the hope that it will be useful, | |
17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
19 | * GNU General Public License for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU General Public License | |
22 | * along with this program; if not, write to the Free Software | |
23 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
24 | * | |
25 | * | |
26 | * Started by Ingo Molnar <mingo@elte.hu> | |
27 | */ | |
28 | ||
29 | #include <linux/personality.h> | |
30 | #include <linux/mm.h> | |
31 | #include <linux/random.h> | |
e8edc6e0 | 32 | #include <linux/sched.h> |
8817210d AK |
33 | |
34 | /* | |
35 | * Top of mmap area (just below the process stack). | |
36 | * | |
37 | * Leave an at least ~128 MB hole. | |
38 | */ | |
39 | #define MIN_GAP (128*1024*1024) | |
40 | #define MAX_GAP (TASK_SIZE/6*5) | |
41 | ||
42 | static inline unsigned long mmap_base(struct mm_struct *mm) | |
43 | { | |
44 | unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur; | |
45 | unsigned long random_factor = 0; | |
46 | ||
47 | if (current->flags & PF_RANDOMIZE) | |
48 | random_factor = get_random_int() % (1024*1024); | |
49 | ||
50 | if (gap < MIN_GAP) | |
51 | gap = MIN_GAP; | |
52 | else if (gap > MAX_GAP) | |
53 | gap = MAX_GAP; | |
54 | ||
55 | return PAGE_ALIGN(TASK_SIZE - gap - random_factor); | |
56 | } | |
57 | ||
58 | /* | |
59 | * This function, called very early during the creation of a new | |
60 | * process VM image, sets up which VM layout function to use: | |
61 | */ | |
62 | void ia32_pick_mmap_layout(struct mm_struct *mm) | |
63 | { | |
64 | /* | |
65 | * Fall back to the standard layout if the personality | |
66 | * bit is set, or if the expected stack growth is unlimited: | |
67 | */ | |
68 | if (sysctl_legacy_va_layout || | |
69 | (current->personality & ADDR_COMPAT_LAYOUT) || | |
70 | current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) { | |
71 | mm->mmap_base = TASK_UNMAPPED_BASE; | |
72 | mm->get_unmapped_area = arch_get_unmapped_area; | |
73 | mm->unmap_area = arch_unmap_area; | |
74 | } else { | |
75 | mm->mmap_base = mmap_base(mm); | |
76 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; | |
77 | mm->unmap_area = arch_unmap_area_topdown; | |
78 | } | |
79 | } |