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
;