2 * flexible mmap layout support
4 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
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.
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.
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
22 * Started by Ingo Molnar <mingo@elte.hu>
25 #include <linux/personality.h>
27 #include <linux/random.h>
28 #include <linux/sched/signal.h>
29 #include <linux/sched/mm.h>
30 #include <linux/elf-randomize.h>
31 #include <linux/security.h>
32 #include <linux/mman.h>
35 * Top of mmap area (just below the process stack).
37 * Leave at least a ~128 MB hole on 32bit applications.
39 * On 64bit applications we randomise the stack by 1GB so we need to
40 * space our mmap start address by a further 1GB, otherwise there is a
41 * chance the mmap area will end up closer to the stack than our ulimit
44 #define MIN_GAP32 (128*1024*1024)
45 #define MIN_GAP64 ((128 + 1024)*1024*1024UL)
46 #define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
47 #define MAX_GAP (TASK_SIZE/6*5)
49 static inline int mmap_is_legacy(void)
51 if (current->personality & ADDR_COMPAT_LAYOUT)
54 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
57 return sysctl_legacy_va_layout;
60 unsigned long arch_mmap_rnd(void)
64 /* 8MB for 32bit, 1GB for 64bit */
66 rnd = get_random_long() % (1<<(23-PAGE_SHIFT));
68 rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT));
70 return rnd << PAGE_SHIFT;
73 static inline unsigned long mmap_base(unsigned long rnd)
75 unsigned long gap = rlimit(RLIMIT_STACK);
79 else if (gap > MAX_GAP)
82 return PAGE_ALIGN(TASK_SIZE - gap - rnd);
85 #ifdef CONFIG_PPC_RADIX_MMU
87 * Same function as generic code used only for radix, because we don't need to overload
88 * the generic one. But we will have to duplicate, because hash select
89 * HAVE_ARCH_UNMAPPED_AREA
92 radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
93 unsigned long len, unsigned long pgoff,
96 struct mm_struct *mm = current->mm;
97 struct vm_area_struct *vma;
98 struct vm_unmapped_area_info info;
100 if (len > TASK_SIZE - mmap_min_addr)
103 if (flags & MAP_FIXED)
107 addr = PAGE_ALIGN(addr);
108 vma = find_vma(mm, addr);
109 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
110 (!vma || addr + len <= vma->vm_start))
116 info.low_limit = mm->mmap_base;
117 info.high_limit = TASK_SIZE;
119 return vm_unmapped_area(&info);
123 radix__arch_get_unmapped_area_topdown(struct file *filp,
124 const unsigned long addr0,
125 const unsigned long len,
126 const unsigned long pgoff,
127 const unsigned long flags)
129 struct vm_area_struct *vma;
130 struct mm_struct *mm = current->mm;
131 unsigned long addr = addr0;
132 struct vm_unmapped_area_info info;
134 /* requested length too big for entire address space */
135 if (len > TASK_SIZE - mmap_min_addr)
138 if (flags & MAP_FIXED)
141 /* requesting a specific address */
143 addr = PAGE_ALIGN(addr);
144 vma = find_vma(mm, addr);
145 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
146 (!vma || addr + len <= vma->vm_start))
150 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
152 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
153 info.high_limit = mm->mmap_base;
155 addr = vm_unmapped_area(&info);
158 * A failed mmap() very likely causes application failure,
159 * so fall back to the bottom-up function here. This scenario
160 * can happen with large stack limits and large mmap()
163 if (addr & ~PAGE_MASK) {
164 VM_BUG_ON(addr != -ENOMEM);
166 info.low_limit = TASK_UNMAPPED_BASE;
167 info.high_limit = TASK_SIZE;
168 addr = vm_unmapped_area(&info);
174 static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
175 unsigned long random_factor)
177 if (mmap_is_legacy()) {
178 mm->mmap_base = TASK_UNMAPPED_BASE;
179 mm->get_unmapped_area = radix__arch_get_unmapped_area;
181 mm->mmap_base = mmap_base(random_factor);
182 mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
187 extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,
188 unsigned long random_factor);
191 * This function, called very early during the creation of a new
192 * process VM image, sets up which VM layout function to use:
194 void arch_pick_mmap_layout(struct mm_struct *mm)
196 unsigned long random_factor = 0UL;
198 if (current->flags & PF_RANDOMIZE)
199 random_factor = arch_mmap_rnd();
202 return radix__arch_pick_mmap_layout(mm, random_factor);
204 * Fall back to the standard layout if the personality
205 * bit is set, or if the expected stack growth is unlimited:
207 if (mmap_is_legacy()) {
208 mm->mmap_base = TASK_UNMAPPED_BASE;
209 mm->get_unmapped_area = arch_get_unmapped_area;
211 mm->mmap_base = mmap_base(random_factor);
212 mm->get_unmapped_area = arch_get_unmapped_area_topdown;