Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 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> |
Alexey Dobriyan | e8edc6e | 2007-05-21 01:22:52 +0400 | [diff] [blame] | 32 | #include <linux/sched.h> |
Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 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 | } |