Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 1 | /* |
Harvey Harrison | 675a081 | 2008-01-30 13:31:10 +0100 | [diff] [blame] | 2 | * Flexible mmap layout support |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 3 | * |
| 4 | * Based on code by Ingo Molnar and Andi Kleen, copyrighted |
| 5 | * as follows: |
| 6 | * |
Ingo Molnar | 8f47e16 | 2009-01-31 02:03:42 +0100 | [diff] [blame] | 7 | * Copyright 2003-2009 Red Hat Inc. |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 8 | * All Rights Reserved. |
| 9 | * Copyright 2005 Andi Kleen, SUSE Labs. |
| 10 | * Copyright 2007 Jiri Kosina, SUSE Labs. |
| 11 | * |
| 12 | * This program is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU General Public License as published by |
| 14 | * the Free Software Foundation; either version 2 of the License, or |
| 15 | * (at your option) any later version. |
| 16 | * |
| 17 | * This program is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License |
| 23 | * along with this program; if not, write to the Free Software |
| 24 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 25 | */ |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 26 | |
| 27 | #include <linux/personality.h> |
Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 28 | #include <linux/mm.h> |
Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 29 | #include <linux/random.h> |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 30 | #include <linux/limits.h> |
| 31 | #include <linux/sched.h> |
Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 32 | |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 33 | /* |
| 34 | * Top of mmap area (just below the process stack). |
| 35 | * |
| 36 | * Leave an at least ~128 MB hole. |
| 37 | */ |
| 38 | #define MIN_GAP (128*1024*1024) |
| 39 | #define MAX_GAP (TASK_SIZE/6*5) |
Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 40 | |
Harvey Harrison | 675a081 | 2008-01-30 13:31:10 +0100 | [diff] [blame] | 41 | /* |
| 42 | * True on X86_32 or when emulating IA32 on X86_64 |
| 43 | */ |
| 44 | static int mmap_is_ia32(void) |
Andi Kleen | 8817210 | 2006-01-17 07:03:38 +0100 | [diff] [blame] | 45 | { |
Harvey Harrison | 675a081 | 2008-01-30 13:31:10 +0100 | [diff] [blame] | 46 | #ifdef CONFIG_X86_32 |
| 47 | return 1; |
| 48 | #endif |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 49 | #ifdef CONFIG_IA32_EMULATION |
| 50 | if (test_thread_flag(TIF_IA32)) |
| 51 | return 1; |
| 52 | #endif |
| 53 | return 0; |
| 54 | } |
| 55 | |
Andrew Morton | 954683a | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 56 | static int mmap_is_legacy(void) |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 57 | { |
| 58 | if (current->personality & ADDR_COMPAT_LAYOUT) |
| 59 | return 1; |
| 60 | |
| 61 | if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) |
| 62 | return 1; |
| 63 | |
| 64 | return sysctl_legacy_va_layout; |
| 65 | } |
| 66 | |
Harvey Harrison | 675a081 | 2008-01-30 13:31:10 +0100 | [diff] [blame] | 67 | static unsigned long mmap_rnd(void) |
| 68 | { |
| 69 | unsigned long rnd = 0; |
| 70 | |
| 71 | /* |
| 72 | * 8 bits of randomness in 32bit mmaps, 20 address space bits |
| 73 | * 28 bits of randomness in 64bit mmaps, 40 address space bits |
| 74 | */ |
| 75 | if (current->flags & PF_RANDOMIZE) { |
| 76 | if (mmap_is_ia32()) |
| 77 | rnd = (long)get_random_int() % (1<<8); |
| 78 | else |
| 79 | rnd = (long)(get_random_int() % (1<<28)); |
| 80 | } |
| 81 | return rnd << PAGE_SHIFT; |
| 82 | } |
| 83 | |
| 84 | static unsigned long mmap_base(void) |
| 85 | { |
| 86 | unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur; |
| 87 | |
| 88 | if (gap < MIN_GAP) |
| 89 | gap = MIN_GAP; |
| 90 | else if (gap > MAX_GAP) |
| 91 | gap = MAX_GAP; |
| 92 | |
| 93 | return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd()); |
| 94 | } |
| 95 | |
| 96 | /* |
| 97 | * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64 |
| 98 | * does, but not when emulating X86_32 |
| 99 | */ |
| 100 | static unsigned long mmap_legacy_base(void) |
| 101 | { |
| 102 | if (mmap_is_ia32()) |
| 103 | return TASK_UNMAPPED_BASE; |
| 104 | else |
| 105 | return TASK_UNMAPPED_BASE + mmap_rnd(); |
| 106 | } |
| 107 | |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 108 | /* |
| 109 | * This function, called very early during the creation of a new |
| 110 | * process VM image, sets up which VM layout function to use: |
| 111 | */ |
| 112 | void arch_pick_mmap_layout(struct mm_struct *mm) |
| 113 | { |
Harvey Harrison | 675a081 | 2008-01-30 13:31:10 +0100 | [diff] [blame] | 114 | if (mmap_is_legacy()) { |
| 115 | mm->mmap_base = mmap_legacy_base(); |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 116 | mm->get_unmapped_area = arch_get_unmapped_area; |
| 117 | mm->unmap_area = arch_unmap_area; |
| 118 | } else { |
| 119 | mm->mmap_base = mmap_base(); |
| 120 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
| 121 | mm->unmap_area = arch_unmap_area_topdown; |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 122 | } |
Jiri Kosina | cc503c1 | 2008-01-30 13:31:07 +0100 | [diff] [blame] | 123 | } |