summaryrefslogtreecommitdiff
path: root/arch/x86/mm/mmap.c
blob: 155ecbac9e28f10c2f83cdbf48037a2f8f6a44fe (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
/*
 * Flexible mmap layout support
 *
 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
 * as follows:
 *
 * Copyright 2003-2009 Red Hat Inc.
 * All Rights Reserved.
 * Copyright 2005 Andi Kleen, SUSE Labs.
 * Copyright 2007 Jiri Kosina, SUSE Labs.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/personality.h>
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/limits.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/compat.h>
#include <asm/elf.h>

#include "physaddr.h"

struct va_alignment __read_mostly va_align = {
	.flags = -1,
};

unsigned long task_size_32bit(void)
{
	return IA32_PAGE_OFFSET;
}

unsigned long task_size_64bit(int full_addr_space)
{
	return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
}

static unsigned long stack_maxrandom_size(unsigned long task_size)
{
	unsigned long max = 0;
	if (current->flags & PF_RANDOMIZE) {
		max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit());
		max <<= PAGE_SHIFT;
	}

	return max;
}

#ifdef CONFIG_COMPAT
# define mmap32_rnd_bits  mmap_rnd_compat_bits
# define mmap64_rnd_bits  mmap_rnd_bits
#else
# define mmap32_rnd_bits  mmap_rnd_bits
# define mmap64_rnd_bits  mmap_rnd_bits
#endif

#define SIZE_128M    (128 * 1024 * 1024UL)

static int mmap_is_legacy(void)
{
	if (current->personality & ADDR_COMPAT_LAYOUT)
		return 1;

	return sysctl_legacy_va_layout;
}

static unsigned long arch_rnd(unsigned int rndbits)
{
	if (!(current->flags & PF_RANDOMIZE))
		return 0;
	return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
}

unsigned long arch_mmap_rnd(void)
{
	return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
}

static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)
{
	unsigned long gap = rlimit(RLIMIT_STACK);
	unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
	unsigned long gap_min, gap_max;

	/* Values close to RLIM_INFINITY can overflow. */
	if (gap + pad > gap)
		gap += pad;

	/*
	 * Top of mmap area (just below the process stack).
	 * Leave an at least ~128 MB hole with possible stack randomization.
	 */
	gap_min = SIZE_128M;
	gap_max = (task_size / 6) * 5;

	if (gap < gap_min)
		gap = gap_min;
	else if (gap > gap_max)
		gap = gap_max;

	return PAGE_ALIGN(task_size - gap - rnd);
}

static unsigned long mmap_legacy_base(unsigned long rnd,
				      unsigned long task_size)
{
	return __TASK_UNMAPPED_BASE(task_size) + rnd;
}

/*
 * This function, called very early during the creation of a new
 * process VM image, sets up which VM layout function to use:
 */
static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
		unsigned long random_factor, unsigned long task_size)
{
	*legacy_base = mmap_legacy_base(random_factor, task_size);
	if (mmap_is_legacy())
		*base = *legacy_base;
	else
		*base = mmap_base(random_factor, task_size);
}

void arch_pick_mmap_layout(struct mm_struct *mm)
{
	if (mmap_is_legacy())
		mm->get_unmapped_area = arch_get_unmapped_area;
	else
		mm->get_unmapped_area = arch_get_unmapped_area_topdown;

	arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
			arch_rnd(mmap64_rnd_bits), task_size_64bit(0));

#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
	/*
	 * The mmap syscall mapping base decision depends solely on the
	 * syscall type (64-bit or compat). This applies for 64bit
	 * applications and 32bit applications. The 64bit syscall uses
	 * mmap_base, the compat syscall uses mmap_compat_base.
	 */
	arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
			arch_rnd(mmap32_rnd_bits), task_size_32bit());
#endif
}

unsigned long get_mmap_base(int is_legacy)
{
	struct mm_struct *mm = current->mm;

#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
	if (in_compat_syscall()) {
		return is_legacy ? mm->mmap_compat_legacy_base
				 : mm->mmap_compat_base;
	}
#endif
	return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
}

const char *arch_vma_name(struct vm_area_struct *vma)
{
	if (vma->vm_flags & VM_MPX)
		return "[mpx]";
	return NULL;
}

/**
 * mmap_address_hint_valid - Validate the address hint of mmap
 * @addr:	Address hint
 * @len:	Mapping length
 *
 * Check whether @addr and @addr + @len result in a valid mapping.
 *
 * On 32bit this only checks whether @addr + @len is <= TASK_SIZE.
 *
 * On 64bit with 5-level page tables another sanity check is required
 * because mappings requested by mmap(@addr, 0) which cross the 47-bit
 * virtual address boundary can cause the following theoretical issue:
 *
 *  An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr
 *  is below the border of the 47-bit address space and @addr + @len is
 *  above the border.
 *
 *  With 4-level paging this request succeeds, but the resulting mapping
 *  address will always be within the 47-bit virtual address space, because
 *  the hint address does not result in a valid mapping and is
 *  ignored. Hence applications which are not prepared to handle virtual
 *  addresses above 47-bit work correctly.
 *
 *  With 5-level paging this request would be granted and result in a
 *  mapping which crosses the border of the 47-bit virtual address
 *  space. If the application cannot handle addresses above 47-bit this
 *  will lead to misbehaviour and hard to diagnose failures.
 *
 * Therefore ignore address hints which would result in a mapping crossing
 * the 47-bit virtual address boundary.
 *
 * Note, that in the same scenario with MAP_FIXED the behaviour is
 * different. The request with @addr < 47-bit and @addr + @len > 47-bit
 * fails on a 4-level paging machine but succeeds on a 5-level paging
 * machine. It is reasonable to expect that an application does not rely on
 * the failure of such a fixed mapping request, so the restriction is not
 * applied.
 */
bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
{
	if (TASK_SIZE - len < addr)
		return false;

	return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW);
}

/* Can we access it for direct reading/writing? Must be RAM: */
int valid_phys_addr_range(phys_addr_t addr, size_t count)
{
	return addr + count <= __pa(high_memory);
}

/* Can we access it through mmap? Must be a valid physical address: */
int valid_mmap_phys_addr_range(unsigned long pfn, size_t count)
{
	phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT;

	return phys_addr_valid(addr + count - 1);
}