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867e359b CM |
1 | /* |
2 | * Copyright 2010 Tilera Corporation. All Rights Reserved. | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation, version 2. | |
7 | * | |
8 | * This program is distributed in the hope that it will be useful, but | |
9 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
10 | * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or | |
11 | * NON INFRINGEMENT. See the GNU General Public License for | |
12 | * more details. | |
13 | * | |
14 | * Taken from the i386 architecture and simplified. | |
15 | */ | |
16 | ||
17 | #include <linux/mm.h> | |
18 | #include <linux/random.h> | |
19 | #include <linux/limits.h> | |
20 | #include <linux/sched.h> | |
21 | #include <linux/mman.h> | |
22 | #include <linux/compat.h> | |
23 | ||
24 | /* | |
25 | * Top of mmap area (just below the process stack). | |
26 | * | |
27 | * Leave an at least ~128 MB hole. | |
28 | */ | |
29 | #define MIN_GAP (128*1024*1024) | |
30 | #define MAX_GAP (TASK_SIZE/6*5) | |
31 | ||
32 | static inline unsigned long mmap_base(struct mm_struct *mm) | |
33 | { | |
34 | unsigned long gap = rlimit(RLIMIT_STACK); | |
35 | unsigned long random_factor = 0; | |
36 | ||
37 | if (current->flags & PF_RANDOMIZE) | |
38 | random_factor = get_random_int() % (1024*1024); | |
39 | ||
40 | if (gap < MIN_GAP) | |
41 | gap = MIN_GAP; | |
42 | else if (gap > MAX_GAP) | |
43 | gap = MAX_GAP; | |
44 | ||
45 | return PAGE_ALIGN(TASK_SIZE - gap - random_factor); | |
46 | } | |
47 | ||
48 | /* | |
49 | * This function, called very early during the creation of a new | |
50 | * process VM image, sets up which VM layout function to use: | |
51 | */ | |
52 | void arch_pick_mmap_layout(struct mm_struct *mm) | |
53 | { | |
54 | #if !defined(__tilegx__) | |
55 | int is_32bit = 1; | |
56 | #elif defined(CONFIG_COMPAT) | |
57 | int is_32bit = is_compat_task(); | |
58 | #else | |
59 | int is_32bit = 0; | |
60 | #endif | |
61 | ||
62 | /* | |
63 | * Use standard layout if the expected stack growth is unlimited | |
64 | * or we are running native 64 bits. | |
65 | */ | |
66 | if (!is_32bit || rlimit(RLIMIT_STACK) == RLIM_INFINITY) { | |
67 | mm->mmap_base = TASK_UNMAPPED_BASE; | |
68 | mm->get_unmapped_area = arch_get_unmapped_area; | |
867e359b CM |
69 | } else { |
70 | mm->mmap_base = mmap_base(mm); | |
71 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; | |
867e359b CM |
72 | } |
73 | } |