xref: /linux/arch/x86/kernel/sys_x86_64.c (revision 905e46acd3272d04566fec49afbd7ad9e2ed9ae3)
1 #include <linux/errno.h>
2 #include <linux/sched.h>
3 #include <linux/sched/mm.h>
4 #include <linux/syscalls.h>
5 #include <linux/mm.h>
6 #include <linux/fs.h>
7 #include <linux/smp.h>
8 #include <linux/sem.h>
9 #include <linux/msg.h>
10 #include <linux/shm.h>
11 #include <linux/stat.h>
12 #include <linux/mman.h>
13 #include <linux/file.h>
14 #include <linux/utsname.h>
15 #include <linux/personality.h>
16 #include <linux/random.h>
17 #include <linux/uaccess.h>
18 #include <linux/elf.h>
19 
20 #include <asm/elf.h>
21 #include <asm/compat.h>
22 #include <asm/ia32.h>
23 #include <asm/syscalls.h>
24 
25 /*
26  * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
27  */
28 static 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  */
50 static unsigned long get_align_bits(void)
51 {
52 	return va_align.bits & get_align_mask();
53 }
54 
55 unsigned 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 
62 static 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 (*str == '=')
72 		str++;
73 
74 	if (!strcmp(str, "32"))
75 		va_align.flags = ALIGN_VA_32;
76 	else if (!strcmp(str, "64"))
77 		va_align.flags = ALIGN_VA_64;
78 	else if (!strcmp(str, "off"))
79 		va_align.flags = 0;
80 	else if (!strcmp(str, "on"))
81 		va_align.flags = ALIGN_VA_32 | ALIGN_VA_64;
82 	else
83 		return 0;
84 
85 	return 1;
86 }
87 __setup("align_va_addr", control_va_addr_alignment);
88 
89 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
90 		unsigned long, prot, unsigned long, flags,
91 		unsigned long, fd, unsigned long, off)
92 {
93 	long error;
94 	error = -EINVAL;
95 	if (off & ~PAGE_MASK)
96 		goto out;
97 
98 	error = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
99 out:
100 	return error;
101 }
102 
103 static void find_start_end(unsigned long flags, unsigned long *begin,
104 			   unsigned long *end)
105 {
106 	if (!in_compat_syscall() && (flags & MAP_32BIT)) {
107 		/* This is usually used needed to map code in small
108 		   model, so it needs to be in the first 31bit. Limit
109 		   it to that.  This means we need to move the
110 		   unmapped base down for this case. This can give
111 		   conflicts with the heap, but we assume that glibc
112 		   malloc knows how to fall back to mmap. Give it 1GB
113 		   of playground for now. -AK */
114 		*begin = 0x40000000;
115 		*end = 0x80000000;
116 		if (current->flags & PF_RANDOMIZE) {
117 			*begin = randomize_page(*begin, 0x02000000);
118 		}
119 		return;
120 	}
121 
122 	*begin	= get_mmap_base(1);
123 	*end	= in_compat_syscall() ? tasksize_32bit() : tasksize_64bit();
124 }
125 
126 unsigned long
127 arch_get_unmapped_area(struct file *filp, unsigned long addr,
128 		unsigned long len, unsigned long pgoff, unsigned long flags)
129 {
130 	struct mm_struct *mm = current->mm;
131 	struct vm_area_struct *vma;
132 	struct vm_unmapped_area_info info;
133 	unsigned long begin, end;
134 
135 	if (flags & MAP_FIXED)
136 		return addr;
137 
138 	find_start_end(flags, &begin, &end);
139 
140 	if (len > end)
141 		return -ENOMEM;
142 
143 	if (addr) {
144 		addr = PAGE_ALIGN(addr);
145 		vma = find_vma(mm, addr);
146 		if (end - len >= addr &&
147 		    (!vma || addr + len <= vma->vm_start))
148 			return addr;
149 	}
150 
151 	info.flags = 0;
152 	info.length = len;
153 	info.low_limit = begin;
154 	info.high_limit = end;
155 	info.align_mask = 0;
156 	info.align_offset = pgoff << PAGE_SHIFT;
157 	if (filp) {
158 		info.align_mask = get_align_mask();
159 		info.align_offset += get_align_bits();
160 	}
161 	return vm_unmapped_area(&info);
162 }
163 
164 unsigned long
165 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
166 			  const unsigned long len, const unsigned long pgoff,
167 			  const unsigned long flags)
168 {
169 	struct vm_area_struct *vma;
170 	struct mm_struct *mm = current->mm;
171 	unsigned long addr = addr0;
172 	struct vm_unmapped_area_info info;
173 
174 	/* requested length too big for entire address space */
175 	if (len > TASK_SIZE)
176 		return -ENOMEM;
177 
178 	if (flags & MAP_FIXED)
179 		return addr;
180 
181 	/* for MAP_32BIT mappings we force the legacy mmap base */
182 	if (!in_compat_syscall() && (flags & MAP_32BIT))
183 		goto bottomup;
184 
185 	/* requesting a specific address */
186 	if (addr) {
187 		addr = PAGE_ALIGN(addr);
188 		vma = find_vma(mm, addr);
189 		if (TASK_SIZE - len >= addr &&
190 				(!vma || addr + len <= vma->vm_start))
191 			return addr;
192 	}
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 	info.align_mask = 0;
199 	info.align_offset = pgoff << PAGE_SHIFT;
200 	if (filp) {
201 		info.align_mask = get_align_mask();
202 		info.align_offset += get_align_bits();
203 	}
204 	addr = vm_unmapped_area(&info);
205 	if (!(addr & ~PAGE_MASK))
206 		return addr;
207 	VM_BUG_ON(addr != -ENOMEM);
208 
209 bottomup:
210 	/*
211 	 * A failed mmap() very likely causes application failure,
212 	 * so fall back to the bottom-up function here. This scenario
213 	 * can happen with large stack limits and large mmap()
214 	 * allocations.
215 	 */
216 	return arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
217 }
218