Commit | Line | Data |
---|---|---|
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 | |
b2eca427 TL |
61 | unsigned long random_factor = 0UL; |
62 | ||
63 | /* | |
64 | * 8 bits of randomness in 32bit mmaps, 24 address space bits | |
65 | * 12 bits of randomness in 64bit mmaps, 28 address space bits | |
66 | */ | |
67 | if (current->flags & PF_RANDOMIZE) { | |
68 | if (is_32bit) | |
69 | random_factor = get_random_int() % (1<<8); | |
70 | else | |
71 | random_factor = get_random_int() % (1<<12); | |
72 | ||
73 | random_factor <<= PAGE_SHIFT; | |
74 | } | |
867e359b CM |
75 | |
76 | /* | |
77 | * Use standard layout if the expected stack growth is unlimited | |
78 | * or we are running native 64 bits. | |
79 | */ | |
b2eca427 TL |
80 | if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) { |
81 | mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; | |
867e359b | 82 | mm->get_unmapped_area = arch_get_unmapped_area; |
867e359b CM |
83 | } else { |
84 | mm->mmap_base = mmap_base(mm); | |
85 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; | |
867e359b CM |
86 | } |
87 | } | |
b2eca427 TL |
88 | |
89 | unsigned long arch_randomize_brk(struct mm_struct *mm) | |
90 | { | |
91 | unsigned long range_end = mm->brk + 0x02000000; | |
92 | return randomize_range(mm->brk, range_end, 0) ? : mm->brk; | |
93 | } |