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.h>
29 #include <linux/elf-randomize.h>
30 #include <linux/security.h>
31 #include <linux/mman.h>
34 * Top of mmap area (just below the process stack).
36 * Leave at least a ~128 MB hole on 32bit applications.
38 * On 64bit applications we randomise the stack by 1GB so we need to
39 * space our mmap start address by a further 1GB, otherwise there is a
40 * chance the mmap area will end up closer to the stack than our ulimit
43 #define MIN_GAP32 (128*1024*1024)
44 #define MIN_GAP64 ((128 + 1024)*1024*1024UL)
45 #define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
46 #define MAX_GAP (TASK_SIZE/6*5)
48 static inline int mmap_is_legacy(void)
50 if (current->personality & ADDR_COMPAT_LAYOUT)
53 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
56 return sysctl_legacy_va_layout;
59 unsigned long arch_mmap_rnd(void)
63 /* 8MB for 32bit, 1GB for 64bit */
65 rnd = get_random_long() % (1<<(23-PAGE_SHIFT));
67 rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT));
69 return rnd << PAGE_SHIFT;
72 static inline unsigned long mmap_base(unsigned long rnd)
74 unsigned long gap = rlimit(RLIMIT_STACK);
78 else if (gap > MAX_GAP)
81 return PAGE_ALIGN(TASK_SIZE - gap - rnd);
84 #ifdef CONFIG_PPC_RADIX_MMU
86 * Same function as generic code used only for radix, because we don't need to overload
87 * the generic one. But we will have to duplicate, because hash select
88 * HAVE_ARCH_UNMAPPED_AREA
91 radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
92 unsigned long len, unsigned long pgoff,
95 struct mm_struct *mm = current->mm;
96 struct vm_area_struct *vma;
97 struct vm_unmapped_area_info info;
99 if (len > TASK_SIZE - mmap_min_addr)
102 if (flags & MAP_FIXED)
106 addr = PAGE_ALIGN(addr);
107 vma = find_vma(mm, addr);
108 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
109 (!vma || addr + len <= vma->vm_start))
115 info.low_limit = mm->mmap_base;
116 info.high_limit = TASK_SIZE;
118 return vm_unmapped_area(&info);
122 radix__arch_get_unmapped_area_topdown(struct file *filp,
123 const unsigned long addr0,
124 const unsigned long len,
125 const unsigned long pgoff,
126 const unsigned long flags)
128 struct vm_area_struct *vma;
129 struct mm_struct *mm = current->mm;
130 unsigned long addr = addr0;
131 struct vm_unmapped_area_info info;
133 /* requested length too big for entire address space */
134 if (len > TASK_SIZE - mmap_min_addr)
137 if (flags & MAP_FIXED)
140 /* requesting a specific address */
142 addr = PAGE_ALIGN(addr);
143 vma = find_vma(mm, addr);
144 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
145 (!vma || addr + len <= vma->vm_start))
149 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
151 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
152 info.high_limit = mm->mmap_base;
154 addr = vm_unmapped_area(&info);
157 * A failed mmap() very likely causes application failure,
158 * so fall back to the bottom-up function here. This scenario
159 * can happen with large stack limits and large mmap()
162 if (addr & ~PAGE_MASK) {
163 VM_BUG_ON(addr != -ENOMEM);
165 info.low_limit = TASK_UNMAPPED_BASE;
166 info.high_limit = TASK_SIZE;
167 addr = vm_unmapped_area(&info);
173 static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
174 unsigned long random_factor)
176 if (mmap_is_legacy()) {
177 mm->mmap_base = TASK_UNMAPPED_BASE;
178 mm->get_unmapped_area = radix__arch_get_unmapped_area;
180 mm->mmap_base = mmap_base(random_factor);
181 mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
186 extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,
187 unsigned long random_factor);
190 * This function, called very early during the creation of a new
191 * process VM image, sets up which VM layout function to use:
193 void arch_pick_mmap_layout(struct mm_struct *mm)
195 unsigned long random_factor = 0UL;
197 if (current->flags & PF_RANDOMIZE)
198 random_factor = arch_mmap_rnd();
201 return radix__arch_pick_mmap_layout(mm, random_factor);
203 * Fall back to the standard layout if the personality
204 * bit is set, or if the expected stack growth is unlimited:
206 if (mmap_is_legacy()) {
207 mm->mmap_base = TASK_UNMAPPED_BASE;
208 mm->get_unmapped_area = arch_get_unmapped_area;
210 mm->mmap_base = mmap_base(random_factor);
211 mm->get_unmapped_area = arch_get_unmapped_area_topdown;