Commit | Line | Data |
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1da177e4 | 1 | /* |
1da177e4 LT |
2 | * flexible mmap layout support |
3 | * | |
4 | * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. | |
5 | * All Rights Reserved. | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License as published by | |
9 | * the Free Software Foundation; either version 2 of the License, or | |
10 | * (at your option) any later version. | |
11 | * | |
12 | * This program is distributed in the hope that it will be useful, | |
13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | * GNU General Public License for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU General Public License | |
18 | * along with this program; if not, write to the Free Software | |
19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
20 | * | |
21 | * | |
22 | * Started by Ingo Molnar <mingo@elte.hu> | |
23 | */ | |
24 | ||
25 | #include <linux/personality.h> | |
26 | #include <linux/mm.h> | |
27 | ||
28 | /* | |
29 | * Top of mmap area (just below the process stack). | |
30 | * | |
31 | * Leave an at least ~128 MB hole. | |
32 | */ | |
33 | #define MIN_GAP (128*1024*1024) | |
34 | #define MAX_GAP (TASK_SIZE/6*5) | |
35 | ||
36 | static inline unsigned long mmap_base(void) | |
37 | { | |
38 | unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur; | |
39 | ||
40 | if (gap < MIN_GAP) | |
41 | gap = MIN_GAP; | |
42 | else if (gap > MAX_GAP) | |
43 | gap = MAX_GAP; | |
44 | ||
45 | return TASK_SIZE - (gap & PAGE_MASK); | |
46 | } | |
47 | ||
48 | static inline int mmap_is_legacy(void) | |
49 | { | |
50 | /* | |
51 | * Force standard allocation for 64 bit programs. | |
52 | */ | |
53 | if (!test_thread_flag(TIF_32BIT)) | |
54 | return 1; | |
55 | ||
56 | if (current->personality & ADDR_COMPAT_LAYOUT) | |
57 | return 1; | |
58 | ||
59 | if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) | |
60 | return 1; | |
61 | ||
62 | return sysctl_legacy_va_layout; | |
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 | */ | |
69 | void 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 | } |