2 * Flexible mmap layout support
4 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
7 * Copyright 2003-2009 Red Hat Inc.
9 * Copyright 2005 Andi Kleen, SUSE Labs.
10 * Copyright 2007 Jiri Kosina, SUSE Labs.
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
27 #include <linux/personality.h>
29 #include <linux/random.h>
30 #include <linux/limits.h>
31 #include <linux/sched/signal.h>
32 #include <linux/sched/mm.h>
33 #include <linux/compat.h>
36 struct va_alignment __read_mostly va_align
= {
40 unsigned long task_size_32bit(void)
42 return IA32_PAGE_OFFSET
;
45 unsigned long task_size_64bit(int full_addr_space
)
47 return full_addr_space
? TASK_SIZE_MAX
: DEFAULT_MAP_WINDOW
;
50 static unsigned long stack_maxrandom_size(unsigned long task_size
)
52 unsigned long max
= 0;
53 if (current
->flags
& PF_RANDOMIZE
) {
54 max
= (-1UL) & __STACK_RND_MASK(task_size
== task_size_32bit());
62 # define mmap32_rnd_bits mmap_rnd_compat_bits
63 # define mmap64_rnd_bits mmap_rnd_bits
65 # define mmap32_rnd_bits mmap_rnd_bits
66 # define mmap64_rnd_bits mmap_rnd_bits
69 #define SIZE_128M (128 * 1024 * 1024UL)
71 static int mmap_is_legacy(void)
73 if (current
->personality
& ADDR_COMPAT_LAYOUT
)
76 return sysctl_legacy_va_layout
;
79 static unsigned long arch_rnd(unsigned int rndbits
)
81 if (!(current
->flags
& PF_RANDOMIZE
))
83 return (get_random_long() & ((1UL << rndbits
) - 1)) << PAGE_SHIFT
;
86 unsigned long arch_mmap_rnd(void)
88 return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits
: mmap64_rnd_bits
);
91 static unsigned long mmap_base(unsigned long rnd
, unsigned long task_size
)
93 unsigned long gap
= rlimit(RLIMIT_STACK
);
94 unsigned long pad
= stack_maxrandom_size(task_size
) + stack_guard_gap
;
95 unsigned long gap_min
, gap_max
;
97 /* Values close to RLIM_INFINITY can overflow. */
102 * Top of mmap area (just below the process stack).
103 * Leave an at least ~128 MB hole with possible stack randomization.
106 gap_max
= (task_size
/ 6) * 5;
110 else if (gap
> gap_max
)
113 return PAGE_ALIGN(task_size
- gap
- rnd
);
116 static unsigned long mmap_legacy_base(unsigned long rnd
,
117 unsigned long task_size
)
119 return __TASK_UNMAPPED_BASE(task_size
) + rnd
;
123 * This function, called very early during the creation of a new
124 * process VM image, sets up which VM layout function to use:
126 static void arch_pick_mmap_base(unsigned long *base
, unsigned long *legacy_base
,
127 unsigned long random_factor
, unsigned long task_size
)
129 *legacy_base
= mmap_legacy_base(random_factor
, task_size
);
130 if (mmap_is_legacy())
131 *base
= *legacy_base
;
133 *base
= mmap_base(random_factor
, task_size
);
136 void arch_pick_mmap_layout(struct mm_struct
*mm
)
138 if (mmap_is_legacy())
139 mm
->get_unmapped_area
= arch_get_unmapped_area
;
141 mm
->get_unmapped_area
= arch_get_unmapped_area_topdown
;
143 arch_pick_mmap_base(&mm
->mmap_base
, &mm
->mmap_legacy_base
,
144 arch_rnd(mmap64_rnd_bits
), task_size_64bit(0));
146 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
148 * The mmap syscall mapping base decision depends solely on the
149 * syscall type (64-bit or compat). This applies for 64bit
150 * applications and 32bit applications. The 64bit syscall uses
151 * mmap_base, the compat syscall uses mmap_compat_base.
153 arch_pick_mmap_base(&mm
->mmap_compat_base
, &mm
->mmap_compat_legacy_base
,
154 arch_rnd(mmap32_rnd_bits
), task_size_32bit());
158 unsigned long get_mmap_base(int is_legacy
)
160 struct mm_struct
*mm
= current
->mm
;
162 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
163 if (in_compat_syscall()) {
164 return is_legacy
? mm
->mmap_compat_legacy_base
165 : mm
->mmap_compat_base
;
168 return is_legacy
? mm
->mmap_legacy_base
: mm
->mmap_base
;
171 const char *arch_vma_name(struct vm_area_struct
*vma
)
173 if (vma
->vm_flags
& VM_MPX
)