1// SPDX-License-Identifier: GPL-2.0
2#include <linux/compat.h>
3#include <linux/errno.h>
4#include <linux/sched.h>
5#include <linux/sched/mm.h>
6#include <linux/syscalls.h>
7#include <linux/mm.h>
8#include <linux/fs.h>
9#include <linux/smp.h>
10#include <linux/sem.h>
11#include <linux/msg.h>
12#include <linux/shm.h>
13#include <linux/stat.h>
14#include <linux/mman.h>
15#include <linux/file.h>
16#include <linux/utsname.h>
17#include <linux/personality.h>
18#include <linux/random.h>
19#include <linux/uaccess.h>
20#include <linux/elf.h>
21
22#include <asm/elf.h>
23#include <asm/ia32.h>
24
25/*
26 * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
27 */
28static unsigned long get_align_mask(void)
29{
30 /* handle 32- and 64-bit case with a single conditional */
31 if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32())))
32 return 0;
33
34 if (!(current->flags & PF_RANDOMIZE))
35 return 0;
36
37 return va_align.mask;
38}
39
40/*
41 * To avoid aliasing in the I$ on AMD F15h, the bits defined by the
42 * va_align.bits, [12:upper_bit), are set to a random value instead of
43 * zeroing them. This random value is computed once per boot. This form
44 * of ASLR is known as "per-boot ASLR".
45 *
46 * To achieve this, the random value is added to the info.align_offset
47 * value before calling vm_unmapped_area() or ORed directly to the
48 * address.
49 */
50static unsigned long get_align_bits(void)
51{
52 return va_align.bits & get_align_mask();
53}
54
55unsigned long align_vdso_addr(unsigned long addr)
56{
57 unsigned long align_mask = get_align_mask();
58 addr = (addr + align_mask) & ~align_mask;
59 return addr | get_align_bits();
60}
61
62static int __init control_va_addr_alignment(char *str)
63{
64 /* guard against enabling this on other CPU families */
65 if (va_align.flags < 0)
66 return 1;
67
68 if (*str == 0)
69 return 1;
70
71 if (!strcmp(str, "32"))
72 va_align.flags = ALIGN_VA_32;
73 else if (!strcmp(str, "64"))
74 va_align.flags = ALIGN_VA_64;
75 else if (!strcmp(str, "off"))
76 va_align.flags = 0;
77 else if (!strcmp(str, "on"))
78 va_align.flags = ALIGN_VA_32 | ALIGN_VA_64;
79 else
80 pr_warn("invalid option value: 'align_va_addr=%s'\n", str);
81
82 return 1;
83}
84__setup("align_va_addr=", control_va_addr_alignment);
85
86SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
87 unsigned long, prot, unsigned long, flags,
88 unsigned long, fd, unsigned long, off)
89{
90 if (off & ~PAGE_MASK)
91 return -EINVAL;
92
93 return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
94}
95
96static void find_start_end(unsigned long addr, unsigned long flags,
97 unsigned long *begin, unsigned long *end)
98{
99 if (!in_32bit_syscall() && (flags & MAP_32BIT)) {
100 /* This is usually used needed to map code in small
101 model, so it needs to be in the first 31bit. Limit
102 it to that. This means we need to move the
103 unmapped base down for this case. This can give
104 conflicts with the heap, but we assume that glibc
105 malloc knows how to fall back to mmap. Give it 1GB
106 of playground for now. -AK */
107 *begin = 0x40000000;
108 *end = 0x80000000;
109 if (current->flags & PF_RANDOMIZE) {
110 *begin = randomize_page(*begin, 0x02000000);
111 }
112 return;
113 }
114
115 *begin = get_mmap_base(1);
116 if (in_32bit_syscall())
117 *end = task_size_32bit();
118 else
119 *end = task_size_64bit(addr > DEFAULT_MAP_WINDOW);
120}
121
122unsigned long
123arch_get_unmapped_area(struct file *filp, unsigned long addr,
124 unsigned long len, unsigned long pgoff, unsigned long flags)
125{
126 struct mm_struct *mm = current->mm;
127 struct vm_area_struct *vma;
128 struct vm_unmapped_area_info info;
129 unsigned long begin, end;
130
131 if (flags & MAP_FIXED)
132 return addr;
133
134 find_start_end(addr, flags, &begin, &end);
135
136 if (len > end)
137 return -ENOMEM;
138
139 if (addr) {
140 addr = PAGE_ALIGN(addr);
141 vma = find_vma(mm, addr);
142 if (end - len >= addr &&
143 (!vma || addr + len <= vm_start_gap(vma)))
144 return addr;
145 }
146
147 info.flags = 0;
148 info.length = len;
149 info.low_limit = begin;
150 info.high_limit = end;
151 info.align_mask = 0;
152 info.align_offset = pgoff << PAGE_SHIFT;
153 if (filp) {
154 info.align_mask = get_align_mask();
155 info.align_offset += get_align_bits();
156 }
157 return vm_unmapped_area(&info);
158}
159
160unsigned long
161arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
162 const unsigned long len, const unsigned long pgoff,
163 const unsigned long flags)
164{
165 struct vm_area_struct *vma;
166 struct mm_struct *mm = current->mm;
167 unsigned long addr = addr0;
168 struct vm_unmapped_area_info info;
169
170 /* requested length too big for entire address space */
171 if (len > TASK_SIZE)
172 return -ENOMEM;
173
174 /* No address checking. See comment at mmap_address_hint_valid() */
175 if (flags & MAP_FIXED)
176 return addr;
177
178 /* for MAP_32BIT mappings we force the legacy mmap base */
179 if (!in_32bit_syscall() && (flags & MAP_32BIT))
180 goto bottomup;
181
182 /* requesting a specific address */
183 if (addr) {
184 addr &= PAGE_MASK;
185 if (!mmap_address_hint_valid(addr, len))
186 goto get_unmapped_area;
187
188 vma = find_vma(mm, addr);
189 if (!vma || addr + len <= vm_start_gap(vma))
190 return addr;
191 }
192get_unmapped_area:
193
194 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
195 info.length = len;
196 info.low_limit = PAGE_SIZE;
197 info.high_limit = get_mmap_base(0);
198
199 /*
200 * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area
201 * in the full address space.
202 *
203 * !in_32bit_syscall() check to avoid high addresses for x32
204 * (and make it no op on native i386).
205 */
206 if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall())
207 info.high_limit += TASK_SIZE_MAX - DEFAULT_MAP_WINDOW;
208
209 info.align_mask = 0;
210 info.align_offset = pgoff << PAGE_SHIFT;
211 if (filp) {
212 info.align_mask = get_align_mask();
213 info.align_offset += get_align_bits();
214 }
215 addr = vm_unmapped_area(&info);
216 if (!(addr & ~PAGE_MASK))
217 return addr;
218 VM_BUG_ON(addr != -ENOMEM);
219
220bottomup:
221 /*
222 * A failed mmap() very likely causes application failure,
223 * so fall back to the bottom-up function here. This scenario
224 * can happen with large stack limits and large mmap()
225 * allocations.
226 */
227 return arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
228}
229

source code of linux/arch/x86/kernel/sys_x86_64.c