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1/*
2 * Flexible mmap layout support
3 *
4 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
5 * as follows:
6 *
7 * Copyright 2003-2009 Red Hat Inc.
8 * All Rights Reserved.
9 * Copyright 2005 Andi Kleen, SUSE Labs.
10 * Copyright 2007 Jiri Kosina, SUSE Labs.
11 *
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.
16 *
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.
21 *
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
25 */
26
27#include <linux/personality.h>
28#include <linux/mm.h>
29#include <linux/random.h>
30#include <linux/limits.h>
31#include <linux/sched.h>
32#include <asm/elf.h>
33
34struct va_alignment __read_mostly va_align = {
35 .flags = -1,
36};
37
38static unsigned long stack_maxrandom_size(void)
39{
40 unsigned long max = 0;
41 if ((current->flags & PF_RANDOMIZE) &&
42 !(current->personality & ADDR_NO_RANDOMIZE)) {
43 max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;
44 }
45
46 return max;
47}
48
49/*
50 * Top of mmap area (just below the process stack).
51 *
52 * Leave an at least ~128 MB hole with possible stack randomization.
53 */
54#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
55#define MAX_GAP (TASK_SIZE/6*5)
56
57static int mmap_is_legacy(void)
58{
59 if (current->personality & ADDR_COMPAT_LAYOUT)
60 return 1;
61
62 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
63 return 1;
64
65 return sysctl_legacy_va_layout;
66}
67
68unsigned long arch_mmap_rnd(void)
69{
70 unsigned long rnd;
71
72 if (mmap_is_ia32())
73#ifdef CONFIG_COMPAT
74 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
75#else
76 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
77#endif
78 else
79 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
80
81 return rnd << PAGE_SHIFT;
82}
83
84static unsigned long mmap_base(unsigned long rnd)
85{
86 unsigned long gap = rlimit(RLIMIT_STACK);
87
88 if (gap < MIN_GAP)
89 gap = MIN_GAP;
90 else if (gap > MAX_GAP)
91 gap = MAX_GAP;
92
93 return PAGE_ALIGN(TASK_SIZE - gap - rnd);
94}
95
96/*
97 * This function, called very early during the creation of a new
98 * process VM image, sets up which VM layout function to use:
99 */
100void arch_pick_mmap_layout(struct mm_struct *mm)
101{
102 unsigned long random_factor = 0UL;
103
104 if (current->flags & PF_RANDOMIZE)
105 random_factor = arch_mmap_rnd();
106
107 mm->mmap_legacy_base = TASK_UNMAPPED_BASE + random_factor;
108
109 if (mmap_is_legacy()) {
110 mm->mmap_base = mm->mmap_legacy_base;
111 mm->get_unmapped_area = arch_get_unmapped_area;
112 } else {
113 mm->mmap_base = mmap_base(random_factor);
114 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
115 }
116}
117
118const char *arch_vma_name(struct vm_area_struct *vma)
119{
120 if (vma->vm_flags & VM_MPX)
121 return "[mpx]";
122 return NULL;
123}
1/*
2 * Flexible mmap layout support
3 *
4 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
5 * as follows:
6 *
7 * Copyright 2003-2009 Red Hat Inc.
8 * All Rights Reserved.
9 * Copyright 2005 Andi Kleen, SUSE Labs.
10 * Copyright 2007 Jiri Kosina, SUSE Labs.
11 *
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.
16 *
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.
21 *
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
25 */
26
27#include <linux/personality.h>
28#include <linux/mm.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>
34#include <asm/elf.h>
35
36#include "physaddr.h"
37
38struct va_alignment __read_mostly va_align = {
39 .flags = -1,
40};
41
42unsigned long task_size_32bit(void)
43{
44 return IA32_PAGE_OFFSET;
45}
46
47unsigned long task_size_64bit(int full_addr_space)
48{
49 return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
50}
51
52static unsigned long stack_maxrandom_size(unsigned long task_size)
53{
54 unsigned long max = 0;
55 if (current->flags & PF_RANDOMIZE) {
56 max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit());
57 max <<= PAGE_SHIFT;
58 }
59
60 return max;
61}
62
63#ifdef CONFIG_COMPAT
64# define mmap32_rnd_bits mmap_rnd_compat_bits
65# define mmap64_rnd_bits mmap_rnd_bits
66#else
67# define mmap32_rnd_bits mmap_rnd_bits
68# define mmap64_rnd_bits mmap_rnd_bits
69#endif
70
71#define SIZE_128M (128 * 1024 * 1024UL)
72
73static int mmap_is_legacy(void)
74{
75 if (current->personality & ADDR_COMPAT_LAYOUT)
76 return 1;
77
78 return sysctl_legacy_va_layout;
79}
80
81static unsigned long arch_rnd(unsigned int rndbits)
82{
83 if (!(current->flags & PF_RANDOMIZE))
84 return 0;
85 return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
86}
87
88unsigned long arch_mmap_rnd(void)
89{
90 return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
91}
92
93static unsigned long mmap_base(unsigned long rnd, unsigned long task_size,
94 struct rlimit *rlim_stack)
95{
96 unsigned long gap = rlim_stack->rlim_cur;
97 unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
98 unsigned long gap_min, gap_max;
99
100 /* Values close to RLIM_INFINITY can overflow. */
101 if (gap + pad > gap)
102 gap += pad;
103
104 /*
105 * Top of mmap area (just below the process stack).
106 * Leave an at least ~128 MB hole with possible stack randomization.
107 */
108 gap_min = SIZE_128M;
109 gap_max = (task_size / 6) * 5;
110
111 if (gap < gap_min)
112 gap = gap_min;
113 else if (gap > gap_max)
114 gap = gap_max;
115
116 return PAGE_ALIGN(task_size - gap - rnd);
117}
118
119static unsigned long mmap_legacy_base(unsigned long rnd,
120 unsigned long task_size)
121{
122 return __TASK_UNMAPPED_BASE(task_size) + rnd;
123}
124
125/*
126 * This function, called very early during the creation of a new
127 * process VM image, sets up which VM layout function to use:
128 */
129static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
130 unsigned long random_factor, unsigned long task_size,
131 struct rlimit *rlim_stack)
132{
133 *legacy_base = mmap_legacy_base(random_factor, task_size);
134 if (mmap_is_legacy())
135 *base = *legacy_base;
136 else
137 *base = mmap_base(random_factor, task_size, rlim_stack);
138}
139
140void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
141{
142 if (mmap_is_legacy())
143 mm->get_unmapped_area = arch_get_unmapped_area;
144 else
145 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
146
147 arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
148 arch_rnd(mmap64_rnd_bits), task_size_64bit(0),
149 rlim_stack);
150
151#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
152 /*
153 * The mmap syscall mapping base decision depends solely on the
154 * syscall type (64-bit or compat). This applies for 64bit
155 * applications and 32bit applications. The 64bit syscall uses
156 * mmap_base, the compat syscall uses mmap_compat_base.
157 */
158 arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
159 arch_rnd(mmap32_rnd_bits), task_size_32bit(),
160 rlim_stack);
161#endif
162}
163
164unsigned long get_mmap_base(int is_legacy)
165{
166 struct mm_struct *mm = current->mm;
167
168#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
169 if (in_compat_syscall()) {
170 return is_legacy ? mm->mmap_compat_legacy_base
171 : mm->mmap_compat_base;
172 }
173#endif
174 return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
175}
176
177const char *arch_vma_name(struct vm_area_struct *vma)
178{
179 if (vma->vm_flags & VM_MPX)
180 return "[mpx]";
181 return NULL;
182}
183
184/**
185 * mmap_address_hint_valid - Validate the address hint of mmap
186 * @addr: Address hint
187 * @len: Mapping length
188 *
189 * Check whether @addr and @addr + @len result in a valid mapping.
190 *
191 * On 32bit this only checks whether @addr + @len is <= TASK_SIZE.
192 *
193 * On 64bit with 5-level page tables another sanity check is required
194 * because mappings requested by mmap(@addr, 0) which cross the 47-bit
195 * virtual address boundary can cause the following theoretical issue:
196 *
197 * An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr
198 * is below the border of the 47-bit address space and @addr + @len is
199 * above the border.
200 *
201 * With 4-level paging this request succeeds, but the resulting mapping
202 * address will always be within the 47-bit virtual address space, because
203 * the hint address does not result in a valid mapping and is
204 * ignored. Hence applications which are not prepared to handle virtual
205 * addresses above 47-bit work correctly.
206 *
207 * With 5-level paging this request would be granted and result in a
208 * mapping which crosses the border of the 47-bit virtual address
209 * space. If the application cannot handle addresses above 47-bit this
210 * will lead to misbehaviour and hard to diagnose failures.
211 *
212 * Therefore ignore address hints which would result in a mapping crossing
213 * the 47-bit virtual address boundary.
214 *
215 * Note, that in the same scenario with MAP_FIXED the behaviour is
216 * different. The request with @addr < 47-bit and @addr + @len > 47-bit
217 * fails on a 4-level paging machine but succeeds on a 5-level paging
218 * machine. It is reasonable to expect that an application does not rely on
219 * the failure of such a fixed mapping request, so the restriction is not
220 * applied.
221 */
222bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
223{
224 if (TASK_SIZE - len < addr)
225 return false;
226
227 return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW);
228}
229
230/* Can we access it for direct reading/writing? Must be RAM: */
231int valid_phys_addr_range(phys_addr_t addr, size_t count)
232{
233 return addr + count <= __pa(high_memory);
234}
235
236/* Can we access it through mmap? Must be a valid physical address: */
237int valid_mmap_phys_addr_range(unsigned long pfn, size_t count)
238{
239 phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT;
240
241 return phys_addr_valid(addr + count - 1);
242}