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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * flexible mmap layout support
4 *
5 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
6 * All Rights Reserved.
7 *
8 * Started by Ingo Molnar <mingo@elte.hu>
9 */
10
11#include <linux/elf-randomize.h>
12#include <linux/personality.h>
13#include <linux/mm.h>
14#include <linux/mman.h>
15#include <linux/sched/signal.h>
16#include <linux/sched/mm.h>
17#include <linux/random.h>
18#include <linux/compat.h>
19#include <linux/security.h>
20#include <asm/elf.h>
21
22static unsigned long stack_maxrandom_size(void)
23{
24 if (!(current->flags & PF_RANDOMIZE))
25 return 0;
26 return STACK_RND_MASK << PAGE_SHIFT;
27}
28
29static inline int mmap_is_legacy(struct rlimit *rlim_stack)
30{
31 if (current->personality & ADDR_COMPAT_LAYOUT)
32 return 1;
33 if (rlim_stack->rlim_cur == RLIM_INFINITY)
34 return 1;
35 return sysctl_legacy_va_layout;
36}
37
38unsigned long arch_mmap_rnd(void)
39{
40 return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
41}
42
43static unsigned long mmap_base_legacy(unsigned long rnd)
44{
45 return TASK_UNMAPPED_BASE + rnd;
46}
47
48static inline unsigned long mmap_base(unsigned long rnd,
49 struct rlimit *rlim_stack)
50{
51 unsigned long gap = rlim_stack->rlim_cur;
52 unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
53 unsigned long gap_min, gap_max;
54
55 /* Values close to RLIM_INFINITY can overflow. */
56 if (gap + pad > gap)
57 gap += pad;
58
59 /*
60 * Top of mmap area (just below the process stack).
61 * Leave at least a ~32 MB hole.
62 */
63 gap_min = 32 * 1024 * 1024UL;
64 gap_max = (STACK_TOP / 6) * 5;
65
66 if (gap < gap_min)
67 gap = gap_min;
68 else if (gap > gap_max)
69 gap = gap_max;
70
71 return PAGE_ALIGN(STACK_TOP - gap - rnd);
72}
73
74unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
75 unsigned long len, unsigned long pgoff,
76 unsigned long flags)
77{
78 struct mm_struct *mm = current->mm;
79 struct vm_area_struct *vma;
80 struct vm_unmapped_area_info info;
81
82 if (len > TASK_SIZE - mmap_min_addr)
83 return -ENOMEM;
84
85 if (flags & MAP_FIXED)
86 goto check_asce_limit;
87
88 if (addr) {
89 addr = PAGE_ALIGN(addr);
90 vma = find_vma(mm, addr);
91 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
92 (!vma || addr + len <= vm_start_gap(vma)))
93 goto check_asce_limit;
94 }
95
96 info.flags = 0;
97 info.length = len;
98 info.low_limit = mm->mmap_base;
99 info.high_limit = TASK_SIZE;
100 if (filp || (flags & MAP_SHARED))
101 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
102 else
103 info.align_mask = 0;
104 info.align_offset = pgoff << PAGE_SHIFT;
105 addr = vm_unmapped_area(&info);
106 if (offset_in_page(addr))
107 return addr;
108
109check_asce_limit:
110 return check_asce_limit(mm, addr, len);
111}
112
113unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
114 unsigned long len, unsigned long pgoff,
115 unsigned long flags)
116{
117 struct vm_area_struct *vma;
118 struct mm_struct *mm = current->mm;
119 struct vm_unmapped_area_info info;
120
121 /* requested length too big for entire address space */
122 if (len > TASK_SIZE - mmap_min_addr)
123 return -ENOMEM;
124
125 if (flags & MAP_FIXED)
126 goto check_asce_limit;
127
128 /* requesting a specific address */
129 if (addr) {
130 addr = PAGE_ALIGN(addr);
131 vma = find_vma(mm, addr);
132 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
133 (!vma || addr + len <= vm_start_gap(vma)))
134 goto check_asce_limit;
135 }
136
137 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
138 info.length = len;
139 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
140 info.high_limit = mm->mmap_base;
141 if (filp || (flags & MAP_SHARED))
142 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
143 else
144 info.align_mask = 0;
145 info.align_offset = pgoff << PAGE_SHIFT;
146 addr = vm_unmapped_area(&info);
147
148 /*
149 * A failed mmap() very likely causes application failure,
150 * so fall back to the bottom-up function here. This scenario
151 * can happen with large stack limits and large mmap()
152 * allocations.
153 */
154 if (offset_in_page(addr)) {
155 VM_BUG_ON(addr != -ENOMEM);
156 info.flags = 0;
157 info.low_limit = TASK_UNMAPPED_BASE;
158 info.high_limit = TASK_SIZE;
159 addr = vm_unmapped_area(&info);
160 if (offset_in_page(addr))
161 return addr;
162 }
163
164check_asce_limit:
165 return check_asce_limit(mm, addr, len);
166}
167
168/*
169 * This function, called very early during the creation of a new
170 * process VM image, sets up which VM layout function to use:
171 */
172void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
173{
174 unsigned long random_factor = 0UL;
175
176 if (current->flags & PF_RANDOMIZE)
177 random_factor = arch_mmap_rnd();
178
179 /*
180 * Fall back to the standard layout if the personality
181 * bit is set, or if the expected stack growth is unlimited:
182 */
183 if (mmap_is_legacy(rlim_stack)) {
184 mm->mmap_base = mmap_base_legacy(random_factor);
185 mm->get_unmapped_area = arch_get_unmapped_area;
186 } else {
187 mm->mmap_base = mmap_base(random_factor, rlim_stack);
188 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
189 }
190}
1/*
2 * flexible mmap layout support
3 *
4 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
5 * All Rights Reserved.
6 *
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.
11 *
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.
16 *
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
20 *
21 *
22 * Started by Ingo Molnar <mingo@elte.hu>
23 */
24
25#include <linux/personality.h>
26#include <linux/mm.h>
27#include <linux/mman.h>
28#include <linux/module.h>
29#include <linux/random.h>
30#include <linux/compat.h>
31#include <linux/security.h>
32#include <asm/pgalloc.h>
33
34static unsigned long stack_maxrandom_size(void)
35{
36 if (!(current->flags & PF_RANDOMIZE))
37 return 0;
38 if (current->personality & ADDR_NO_RANDOMIZE)
39 return 0;
40 return STACK_RND_MASK << PAGE_SHIFT;
41}
42
43/*
44 * Top of mmap area (just below the process stack).
45 *
46 * Leave at least a ~32 MB hole.
47 */
48#define MIN_GAP (32*1024*1024)
49#define MAX_GAP (STACK_TOP/6*5)
50
51static inline int mmap_is_legacy(void)
52{
53 if (current->personality & ADDR_COMPAT_LAYOUT)
54 return 1;
55 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
56 return 1;
57 return sysctl_legacy_va_layout;
58}
59
60unsigned long arch_mmap_rnd(void)
61{
62 return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
63}
64
65static unsigned long mmap_base_legacy(unsigned long rnd)
66{
67 return TASK_UNMAPPED_BASE + rnd;
68}
69
70static inline unsigned long mmap_base(unsigned long rnd)
71{
72 unsigned long gap = rlimit(RLIMIT_STACK);
73
74 if (gap < MIN_GAP)
75 gap = MIN_GAP;
76 else if (gap > MAX_GAP)
77 gap = MAX_GAP;
78 gap &= PAGE_MASK;
79 return STACK_TOP - stack_maxrandom_size() - rnd - gap;
80}
81
82unsigned long
83arch_get_unmapped_area(struct file *filp, unsigned long addr,
84 unsigned long len, unsigned long pgoff, unsigned long flags)
85{
86 struct mm_struct *mm = current->mm;
87 struct vm_area_struct *vma;
88 struct vm_unmapped_area_info info;
89
90 if (len > TASK_SIZE - mmap_min_addr)
91 return -ENOMEM;
92
93 if (flags & MAP_FIXED)
94 return addr;
95
96 if (addr) {
97 addr = PAGE_ALIGN(addr);
98 vma = find_vma(mm, addr);
99 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
100 (!vma || addr + len <= vma->vm_start))
101 return addr;
102 }
103
104 info.flags = 0;
105 info.length = len;
106 info.low_limit = mm->mmap_base;
107 info.high_limit = TASK_SIZE;
108 if (filp || (flags & MAP_SHARED))
109 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
110 else
111 info.align_mask = 0;
112 info.align_offset = pgoff << PAGE_SHIFT;
113 return vm_unmapped_area(&info);
114}
115
116unsigned long
117arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
118 const unsigned long len, const unsigned long pgoff,
119 const unsigned long flags)
120{
121 struct vm_area_struct *vma;
122 struct mm_struct *mm = current->mm;
123 unsigned long addr = addr0;
124 struct vm_unmapped_area_info info;
125
126 /* requested length too big for entire address space */
127 if (len > TASK_SIZE - mmap_min_addr)
128 return -ENOMEM;
129
130 if (flags & MAP_FIXED)
131 return addr;
132
133 /* requesting a specific address */
134 if (addr) {
135 addr = PAGE_ALIGN(addr);
136 vma = find_vma(mm, addr);
137 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
138 (!vma || addr + len <= vma->vm_start))
139 return addr;
140 }
141
142 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
143 info.length = len;
144 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
145 info.high_limit = mm->mmap_base;
146 if (filp || (flags & MAP_SHARED))
147 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
148 else
149 info.align_mask = 0;
150 info.align_offset = pgoff << PAGE_SHIFT;
151 addr = vm_unmapped_area(&info);
152
153 /*
154 * A failed mmap() very likely causes application failure,
155 * so fall back to the bottom-up function here. This scenario
156 * can happen with large stack limits and large mmap()
157 * allocations.
158 */
159 if (addr & ~PAGE_MASK) {
160 VM_BUG_ON(addr != -ENOMEM);
161 info.flags = 0;
162 info.low_limit = TASK_UNMAPPED_BASE;
163 info.high_limit = TASK_SIZE;
164 addr = vm_unmapped_area(&info);
165 }
166
167 return addr;
168}
169
170int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
171{
172 if (is_compat_task() || TASK_SIZE >= TASK_MAX_SIZE)
173 return 0;
174 if (!(flags & MAP_FIXED))
175 addr = 0;
176 if ((addr + len) >= TASK_SIZE)
177 return crst_table_upgrade(current->mm);
178 return 0;
179}
180
181static unsigned long
182s390_get_unmapped_area(struct file *filp, unsigned long addr,
183 unsigned long len, unsigned long pgoff, unsigned long flags)
184{
185 struct mm_struct *mm = current->mm;
186 unsigned long area;
187 int rc;
188
189 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
190 if (!(area & ~PAGE_MASK))
191 return area;
192 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
193 /* Upgrade the page table to 4 levels and retry. */
194 rc = crst_table_upgrade(mm);
195 if (rc)
196 return (unsigned long) rc;
197 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
198 }
199 return area;
200}
201
202static unsigned long
203s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
204 const unsigned long len, const unsigned long pgoff,
205 const unsigned long flags)
206{
207 struct mm_struct *mm = current->mm;
208 unsigned long area;
209 int rc;
210
211 area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
212 if (!(area & ~PAGE_MASK))
213 return area;
214 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
215 /* Upgrade the page table to 4 levels and retry. */
216 rc = crst_table_upgrade(mm);
217 if (rc)
218 return (unsigned long) rc;
219 area = arch_get_unmapped_area_topdown(filp, addr, len,
220 pgoff, flags);
221 }
222 return area;
223}
224/*
225 * This function, called very early during the creation of a new
226 * process VM image, sets up which VM layout function to use:
227 */
228void arch_pick_mmap_layout(struct mm_struct *mm)
229{
230 unsigned long random_factor = 0UL;
231
232 if (current->flags & PF_RANDOMIZE)
233 random_factor = arch_mmap_rnd();
234
235 /*
236 * Fall back to the standard layout if the personality
237 * bit is set, or if the expected stack growth is unlimited:
238 */
239 if (mmap_is_legacy()) {
240 mm->mmap_base = mmap_base_legacy(random_factor);
241 mm->get_unmapped_area = s390_get_unmapped_area;
242 } else {
243 mm->mmap_base = mmap_base(random_factor);
244 mm->get_unmapped_area = s390_get_unmapped_area_topdown;
245 }
246}