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/sched/signal.h>
30 #include <linux/random.h>
31 #include <linux/compat.h>
32 #include <linux/security.h>
33 #include <asm/pgalloc.h>
36 static unsigned long stack_maxrandom_size(void)
38 if (!(current->flags & PF_RANDOMIZE))
40 if (current->personality & ADDR_NO_RANDOMIZE)
42 return STACK_RND_MASK << PAGE_SHIFT;
46 * Top of mmap area (just below the process stack).
48 * Leave at least a ~32 MB hole.
50 #define MIN_GAP (32*1024*1024)
51 #define MAX_GAP (STACK_TOP/6*5)
53 static inline int mmap_is_legacy(void)
55 if (current->personality & ADDR_COMPAT_LAYOUT)
57 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
59 return sysctl_legacy_va_layout;
62 unsigned long arch_mmap_rnd(void)
64 return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
67 static unsigned long mmap_base_legacy(unsigned long rnd)
69 return TASK_UNMAPPED_BASE + rnd;
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 STACK_TOP - stack_maxrandom_size() - rnd - gap;
85 arch_get_unmapped_area(struct file *filp, unsigned long addr,
86 unsigned long len, unsigned long pgoff, unsigned long flags)
88 struct mm_struct *mm = current->mm;
89 struct vm_area_struct *vma;
90 struct vm_unmapped_area_info info;
92 if (len > TASK_SIZE - mmap_min_addr)
95 if (flags & MAP_FIXED)
99 addr = PAGE_ALIGN(addr);
100 vma = find_vma(mm, addr);
101 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
102 (!vma || addr + len <= vma->vm_start))
108 info.low_limit = mm->mmap_base;
109 info.high_limit = TASK_SIZE;
110 if (filp || (flags & MAP_SHARED))
111 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
114 info.align_offset = pgoff << PAGE_SHIFT;
115 return vm_unmapped_area(&info);
119 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
120 const unsigned long len, const unsigned long pgoff,
121 const unsigned long flags)
123 struct vm_area_struct *vma;
124 struct mm_struct *mm = current->mm;
125 unsigned long addr = addr0;
126 struct vm_unmapped_area_info info;
128 /* requested length too big for entire address space */
129 if (len > TASK_SIZE - mmap_min_addr)
132 if (flags & MAP_FIXED)
135 /* requesting a specific address */
137 addr = PAGE_ALIGN(addr);
138 vma = find_vma(mm, addr);
139 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
140 (!vma || addr + len <= vma->vm_start))
144 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
146 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
147 info.high_limit = mm->mmap_base;
148 if (filp || (flags & MAP_SHARED))
149 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
152 info.align_offset = pgoff << PAGE_SHIFT;
153 addr = vm_unmapped_area(&info);
156 * A failed mmap() very likely causes application failure,
157 * so fall back to the bottom-up function here. This scenario
158 * can happen with large stack limits and large mmap()
161 if (addr & ~PAGE_MASK) {
162 VM_BUG_ON(addr != -ENOMEM);
164 info.low_limit = TASK_UNMAPPED_BASE;
165 info.high_limit = TASK_SIZE;
166 addr = vm_unmapped_area(&info);
172 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
174 if (is_compat_task() || TASK_SIZE >= TASK_MAX_SIZE)
176 if (!(flags & MAP_FIXED))
178 if ((addr + len) >= TASK_SIZE)
179 return crst_table_upgrade(current->mm);
184 s390_get_unmapped_area(struct file *filp, unsigned long addr,
185 unsigned long len, unsigned long pgoff, unsigned long flags)
187 struct mm_struct *mm = current->mm;
191 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
192 if (!(area & ~PAGE_MASK))
194 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
195 /* Upgrade the page table to 4 levels and retry. */
196 rc = crst_table_upgrade(mm);
198 return (unsigned long) rc;
199 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
205 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
206 const unsigned long len, const unsigned long pgoff,
207 const unsigned long flags)
209 struct mm_struct *mm = current->mm;
213 area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
214 if (!(area & ~PAGE_MASK))
216 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
217 /* Upgrade the page table to 4 levels and retry. */
218 rc = crst_table_upgrade(mm);
220 return (unsigned long) rc;
221 area = arch_get_unmapped_area_topdown(filp, addr, len,
227 * This function, called very early during the creation of a new
228 * process VM image, sets up which VM layout function to use:
230 void arch_pick_mmap_layout(struct mm_struct *mm)
232 unsigned long random_factor = 0UL;
234 if (current->flags & PF_RANDOMIZE)
235 random_factor = arch_mmap_rnd();
238 * Fall back to the standard layout if the personality
239 * bit is set, or if the expected stack growth is unlimited:
241 if (mmap_is_legacy()) {
242 mm->mmap_base = mmap_base_legacy(random_factor);
243 mm->get_unmapped_area = s390_get_unmapped_area;
245 mm->mmap_base = mmap_base(random_factor);
246 mm->get_unmapped_area = s390_get_unmapped_area_topdown;