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/elf-randomize.h>
26 #include <linux/personality.h>
28 #include <linux/mman.h>
29 #include <linux/module.h>
30 #include <linux/random.h>
31 #include <linux/compat.h>
32 #include <linux/security.h>
33 #include <asm/pgalloc.h>
35 static unsigned long stack_maxrandom_size(void)
37 if (!(current->flags & PF_RANDOMIZE))
39 if (current->personality & ADDR_NO_RANDOMIZE)
41 return STACK_RND_MASK << PAGE_SHIFT;
45 * Top of mmap area (just below the process stack).
47 * Leave at least a ~32 MB hole.
49 #define MIN_GAP (32*1024*1024)
50 #define MAX_GAP (STACK_TOP/6*5)
52 static inline int mmap_is_legacy(void)
54 if (current->personality & ADDR_COMPAT_LAYOUT)
56 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
58 return sysctl_legacy_va_layout;
61 unsigned long arch_mmap_rnd(void)
63 return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
66 static unsigned long mmap_base_legacy(unsigned long rnd)
68 return TASK_UNMAPPED_BASE + rnd;
71 static inline unsigned long mmap_base(unsigned long rnd)
73 unsigned long gap = rlimit(RLIMIT_STACK);
77 else if (gap > MAX_GAP)
80 return STACK_TOP - stack_maxrandom_size() - rnd - gap;
84 arch_get_unmapped_area(struct file *filp, unsigned long addr,
85 unsigned long len, unsigned long pgoff, unsigned long flags)
87 struct mm_struct *mm = current->mm;
88 struct vm_area_struct *vma;
89 struct vm_unmapped_area_info info;
91 if (len > TASK_SIZE - mmap_min_addr)
94 if (flags & MAP_FIXED)
98 addr = PAGE_ALIGN(addr);
99 vma = find_vma(mm, addr);
100 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
101 (!vma || addr + len <= vma->vm_start))
107 info.low_limit = mm->mmap_base;
108 info.high_limit = TASK_SIZE;
109 if (filp || (flags & MAP_SHARED))
110 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
113 info.align_offset = pgoff << PAGE_SHIFT;
114 return vm_unmapped_area(&info);
118 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
119 const unsigned long len, const unsigned long pgoff,
120 const unsigned long flags)
122 struct vm_area_struct *vma;
123 struct mm_struct *mm = current->mm;
124 unsigned long addr = addr0;
125 struct vm_unmapped_area_info info;
127 /* requested length too big for entire address space */
128 if (len > TASK_SIZE - mmap_min_addr)
131 if (flags & MAP_FIXED)
134 /* requesting a specific address */
136 addr = PAGE_ALIGN(addr);
137 vma = find_vma(mm, addr);
138 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
139 (!vma || addr + len <= vma->vm_start))
143 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
145 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
146 info.high_limit = mm->mmap_base;
147 if (filp || (flags & MAP_SHARED))
148 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
151 info.align_offset = pgoff << PAGE_SHIFT;
152 addr = vm_unmapped_area(&info);
155 * A failed mmap() very likely causes application failure,
156 * so fall back to the bottom-up function here. This scenario
157 * can happen with large stack limits and large mmap()
160 if (addr & ~PAGE_MASK) {
161 VM_BUG_ON(addr != -ENOMEM);
163 info.low_limit = TASK_UNMAPPED_BASE;
164 info.high_limit = TASK_SIZE;
165 addr = vm_unmapped_area(&info);
171 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
173 if (is_compat_task() || TASK_SIZE >= TASK_MAX_SIZE)
175 if (!(flags & MAP_FIXED))
177 if ((addr + len) >= TASK_SIZE)
178 return crst_table_upgrade(current->mm);
183 s390_get_unmapped_area(struct file *filp, unsigned long addr,
184 unsigned long len, unsigned long pgoff, unsigned long flags)
186 struct mm_struct *mm = current->mm;
190 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
191 if (!(area & ~PAGE_MASK))
193 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
194 /* Upgrade the page table to 4 levels and retry. */
195 rc = crst_table_upgrade(mm);
197 return (unsigned long) rc;
198 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
204 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
205 const unsigned long len, const unsigned long pgoff,
206 const unsigned long flags)
208 struct mm_struct *mm = current->mm;
212 area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
213 if (!(area & ~PAGE_MASK))
215 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
216 /* Upgrade the page table to 4 levels and retry. */
217 rc = crst_table_upgrade(mm);
219 return (unsigned long) rc;
220 area = arch_get_unmapped_area_topdown(filp, addr, len,
226 * This function, called very early during the creation of a new
227 * process VM image, sets up which VM layout function to use:
229 void arch_pick_mmap_layout(struct mm_struct *mm)
231 unsigned long random_factor = 0UL;
233 if (current->flags & PF_RANDOMIZE)
234 random_factor = arch_mmap_rnd();
237 * Fall back to the standard layout if the personality
238 * bit is set, or if the expected stack growth is unlimited:
240 if (mmap_is_legacy()) {
241 mm->mmap_base = mmap_base_legacy(random_factor);
242 mm->get_unmapped_area = s390_get_unmapped_area;
244 mm->mmap_base = mmap_base(random_factor);
245 mm->get_unmapped_area = s390_get_unmapped_area_topdown;