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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/pgalloc.h>
21#include <asm/elf.h>
22
23static unsigned long stack_maxrandom_size(void)
24{
25 if (!(current->flags & PF_RANDOMIZE))
26 return 0;
27 return STACK_RND_MASK << PAGE_SHIFT;
28}
29
30static inline int mmap_is_legacy(struct rlimit *rlim_stack)
31{
32 if (current->personality & ADDR_COMPAT_LAYOUT)
33 return 1;
34 if (rlim_stack->rlim_cur == RLIM_INFINITY)
35 return 1;
36 return sysctl_legacy_va_layout;
37}
38
39unsigned long arch_mmap_rnd(void)
40{
41 return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
42}
43
44static unsigned long mmap_base_legacy(unsigned long rnd)
45{
46 return TASK_UNMAPPED_BASE + rnd;
47}
48
49static inline unsigned long mmap_base(unsigned long rnd,
50 struct rlimit *rlim_stack)
51{
52 unsigned long gap = rlim_stack->rlim_cur;
53 unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
54 unsigned long gap_min, gap_max;
55
56 /* Values close to RLIM_INFINITY can overflow. */
57 if (gap + pad > gap)
58 gap += pad;
59
60 /*
61 * Top of mmap area (just below the process stack).
62 * Leave at least a ~32 MB hole.
63 */
64 gap_min = 32 * 1024 * 1024UL;
65 gap_max = (STACK_TOP / 6) * 5;
66
67 if (gap < gap_min)
68 gap = gap_min;
69 else if (gap > gap_max)
70 gap = gap_max;
71
72 return PAGE_ALIGN(STACK_TOP - gap - rnd);
73}
74
75unsigned long
76arch_get_unmapped_area(struct file *filp, unsigned long addr,
77 unsigned long len, unsigned long pgoff, unsigned long flags)
78{
79 struct mm_struct *mm = current->mm;
80 struct vm_area_struct *vma;
81 struct vm_unmapped_area_info info;
82 int rc;
83
84 if (len > TASK_SIZE - mmap_min_addr)
85 return -ENOMEM;
86
87 if (flags & MAP_FIXED)
88 goto check_asce_limit;
89
90 if (addr) {
91 addr = PAGE_ALIGN(addr);
92 vma = find_vma(mm, addr);
93 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
94 (!vma || addr + len <= vm_start_gap(vma)))
95 goto check_asce_limit;
96 }
97
98 info.flags = 0;
99 info.length = len;
100 info.low_limit = mm->mmap_base;
101 info.high_limit = TASK_SIZE;
102 if (filp || (flags & MAP_SHARED))
103 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
104 else
105 info.align_mask = 0;
106 info.align_offset = pgoff << PAGE_SHIFT;
107 addr = vm_unmapped_area(&info);
108 if (addr & ~PAGE_MASK)
109 return addr;
110
111check_asce_limit:
112 if (addr + len > current->mm->context.asce_limit &&
113 addr + len <= TASK_SIZE) {
114 rc = crst_table_upgrade(mm, addr + len);
115 if (rc)
116 return (unsigned long) rc;
117 }
118
119 return addr;
120}
121
122unsigned long
123arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
124 const unsigned long len, const unsigned long pgoff,
125 const unsigned long flags)
126{
127 struct vm_area_struct *vma;
128 struct mm_struct *mm = current->mm;
129 unsigned long addr = addr0;
130 struct vm_unmapped_area_info info;
131 int rc;
132
133 /* requested length too big for entire address space */
134 if (len > TASK_SIZE - mmap_min_addr)
135 return -ENOMEM;
136
137 if (flags & MAP_FIXED)
138 goto check_asce_limit;
139
140 /* requesting a specific address */
141 if (addr) {
142 addr = PAGE_ALIGN(addr);
143 vma = find_vma(mm, addr);
144 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
145 (!vma || addr + len <= vm_start_gap(vma)))
146 goto check_asce_limit;
147 }
148
149 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
150 info.length = len;
151 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
152 info.high_limit = mm->mmap_base;
153 if (filp || (flags & MAP_SHARED))
154 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
155 else
156 info.align_mask = 0;
157 info.align_offset = pgoff << PAGE_SHIFT;
158 addr = vm_unmapped_area(&info);
159
160 /*
161 * A failed mmap() very likely causes application failure,
162 * so fall back to the bottom-up function here. This scenario
163 * can happen with large stack limits and large mmap()
164 * allocations.
165 */
166 if (addr & ~PAGE_MASK) {
167 VM_BUG_ON(addr != -ENOMEM);
168 info.flags = 0;
169 info.low_limit = TASK_UNMAPPED_BASE;
170 info.high_limit = TASK_SIZE;
171 addr = vm_unmapped_area(&info);
172 if (addr & ~PAGE_MASK)
173 return addr;
174 }
175
176check_asce_limit:
177 if (addr + len > current->mm->context.asce_limit &&
178 addr + len <= TASK_SIZE) {
179 rc = crst_table_upgrade(mm, addr + len);
180 if (rc)
181 return (unsigned long) rc;
182 }
183
184 return addr;
185}
186
187/*
188 * This function, called very early during the creation of a new
189 * process VM image, sets up which VM layout function to use:
190 */
191void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
192{
193 unsigned long random_factor = 0UL;
194
195 if (current->flags & PF_RANDOMIZE)
196 random_factor = arch_mmap_rnd();
197
198 /*
199 * Fall back to the standard layout if the personality
200 * bit is set, or if the expected stack growth is unlimited:
201 */
202 if (mmap_is_legacy(rlim_stack)) {
203 mm->mmap_base = mmap_base_legacy(random_factor);
204 mm->get_unmapped_area = arch_get_unmapped_area;
205 } else {
206 mm->mmap_base = mmap_base(random_factor, rlim_stack);
207 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
208 }
209}
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 <asm/pgalloc.h>
32
33static unsigned long stack_maxrandom_size(void)
34{
35 if (!(current->flags & PF_RANDOMIZE))
36 return 0;
37 if (current->personality & ADDR_NO_RANDOMIZE)
38 return 0;
39 return STACK_RND_MASK << PAGE_SHIFT;
40}
41
42/*
43 * Top of mmap area (just below the process stack).
44 *
45 * Leave at least a ~32 MB hole.
46 */
47#define MIN_GAP (32*1024*1024)
48#define MAX_GAP (STACK_TOP/6*5)
49
50static inline int mmap_is_legacy(void)
51{
52 if (current->personality & ADDR_COMPAT_LAYOUT)
53 return 1;
54 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
55 return 1;
56 return sysctl_legacy_va_layout;
57}
58
59static unsigned long mmap_rnd(void)
60{
61 if (!(current->flags & PF_RANDOMIZE))
62 return 0;
63 /* 8MB randomization for mmap_base */
64 return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
65}
66
67static unsigned long mmap_base_legacy(void)
68{
69 return TASK_UNMAPPED_BASE + mmap_rnd();
70}
71
72static inline unsigned long mmap_base(void)
73{
74 unsigned long gap = rlimit(RLIMIT_STACK);
75
76 if (gap < MIN_GAP)
77 gap = MIN_GAP;
78 else if (gap > MAX_GAP)
79 gap = MAX_GAP;
80 gap &= PAGE_MASK;
81 return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
82}
83
84#ifndef CONFIG_64BIT
85
86/*
87 * This function, called very early during the creation of a new
88 * process VM image, sets up which VM layout function to use:
89 */
90void arch_pick_mmap_layout(struct mm_struct *mm)
91{
92 /*
93 * Fall back to the standard layout if the personality
94 * bit is set, or if the expected stack growth is unlimited:
95 */
96 if (mmap_is_legacy()) {
97 mm->mmap_base = mmap_base_legacy();
98 mm->get_unmapped_area = arch_get_unmapped_area;
99 } else {
100 mm->mmap_base = mmap_base();
101 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
102 }
103}
104
105#else
106
107int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
108{
109 if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
110 return 0;
111 if (!(flags & MAP_FIXED))
112 addr = 0;
113 if ((addr + len) >= TASK_SIZE)
114 return crst_table_upgrade(current->mm, 1UL << 53);
115 return 0;
116}
117
118static unsigned long
119s390_get_unmapped_area(struct file *filp, unsigned long addr,
120 unsigned long len, unsigned long pgoff, unsigned long flags)
121{
122 struct mm_struct *mm = current->mm;
123 unsigned long area;
124 int rc;
125
126 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
127 if (!(area & ~PAGE_MASK))
128 return area;
129 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
130 /* Upgrade the page table to 4 levels and retry. */
131 rc = crst_table_upgrade(mm, 1UL << 53);
132 if (rc)
133 return (unsigned long) rc;
134 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
135 }
136 return area;
137}
138
139static unsigned long
140s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
141 const unsigned long len, const unsigned long pgoff,
142 const unsigned long flags)
143{
144 struct mm_struct *mm = current->mm;
145 unsigned long area;
146 int rc;
147
148 area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
149 if (!(area & ~PAGE_MASK))
150 return area;
151 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
152 /* Upgrade the page table to 4 levels and retry. */
153 rc = crst_table_upgrade(mm, 1UL << 53);
154 if (rc)
155 return (unsigned long) rc;
156 area = arch_get_unmapped_area_topdown(filp, addr, len,
157 pgoff, flags);
158 }
159 return area;
160}
161/*
162 * This function, called very early during the creation of a new
163 * process VM image, sets up which VM layout function to use:
164 */
165void arch_pick_mmap_layout(struct mm_struct *mm)
166{
167 /*
168 * Fall back to the standard layout if the personality
169 * bit is set, or if the expected stack growth is unlimited:
170 */
171 if (mmap_is_legacy()) {
172 mm->mmap_base = mmap_base_legacy();
173 mm->get_unmapped_area = s390_get_unmapped_area;
174 } else {
175 mm->mmap_base = mmap_base();
176 mm->get_unmapped_area = s390_get_unmapped_area_topdown;
177 }
178}
179
180#endif