1/*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License.  See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (C) 2011 Wind River Systems,
7 *   written by Ralf Baechle <ralf@linux-mips.org>
8 */
9#include <linux/compiler.h>
10#include <linux/errno.h>
11#include <linux/mm.h>
12#include <linux/mman.h>
13#include <linux/module.h>
14#include <linux/personality.h>
15#include <linux/random.h>
16#include <linux/sched.h>
17
18unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
19EXPORT_SYMBOL(shm_align_mask);
20
21/* gap between mmap and stack */
22#define MIN_GAP (128*1024*1024UL)
23#define MAX_GAP ((TASK_SIZE)/6*5)
24
25static int mmap_is_legacy(void)
26{
27	if (current->personality & ADDR_COMPAT_LAYOUT)
28		return 1;
29
30	if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
31		return 1;
32
33	return sysctl_legacy_va_layout;
34}
35
36static unsigned long mmap_base(unsigned long rnd)
37{
38	unsigned long gap = rlimit(RLIMIT_STACK);
39
40	if (gap < MIN_GAP)
41		gap = MIN_GAP;
42	else if (gap > MAX_GAP)
43		gap = MAX_GAP;
44
45	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
46}
47
48#define COLOUR_ALIGN(addr, pgoff)				\
49	((((addr) + shm_align_mask) & ~shm_align_mask) +	\
50	 (((pgoff) << PAGE_SHIFT) & shm_align_mask))
51
52enum mmap_allocation_direction {UP, DOWN};
53
54static unsigned long arch_get_unmapped_area_common(struct file *filp,
55	unsigned long addr0, unsigned long len, unsigned long pgoff,
56	unsigned long flags, enum mmap_allocation_direction dir)
57{
58	struct mm_struct *mm = current->mm;
59	struct vm_area_struct *vma;
60	unsigned long addr = addr0;
61	int do_color_align;
62	struct vm_unmapped_area_info info;
63
64	if (unlikely(len > TASK_SIZE))
65		return -ENOMEM;
66
67	if (flags & MAP_FIXED) {
68		/* Even MAP_FIXED mappings must reside within TASK_SIZE */
69		if (TASK_SIZE - len < addr)
70			return -EINVAL;
71
72		/*
73		 * We do not accept a shared mapping if it would violate
74		 * cache aliasing constraints.
75		 */
76		if ((flags & MAP_SHARED) &&
77		    ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
78			return -EINVAL;
79		return addr;
80	}
81
82	do_color_align = 0;
83	if (filp || (flags & MAP_SHARED))
84		do_color_align = 1;
85
86	/* requesting a specific address */
87	if (addr) {
88		if (do_color_align)
89			addr = COLOUR_ALIGN(addr, pgoff);
90		else
91			addr = PAGE_ALIGN(addr);
92
93		vma = find_vma(mm, addr);
94		if (TASK_SIZE - len >= addr &&
95		    (!vma || addr + len <= vma->vm_start))
96			return addr;
97	}
98
99	info.length = len;
100	info.align_mask = do_color_align ? (PAGE_MASK & shm_align_mask) : 0;
101	info.align_offset = pgoff << PAGE_SHIFT;
102
103	if (dir == DOWN) {
104		info.flags = VM_UNMAPPED_AREA_TOPDOWN;
105		info.low_limit = PAGE_SIZE;
106		info.high_limit = mm->mmap_base;
107		addr = vm_unmapped_area(&info);
108
109		if (!(addr & ~PAGE_MASK))
110			return addr;
111
112		/*
113		 * A failed mmap() very likely causes application failure,
114		 * so fall back to the bottom-up function here. This scenario
115		 * can happen with large stack limits and large mmap()
116		 * allocations.
117		 */
118	}
119
120	info.flags = 0;
121	info.low_limit = mm->mmap_base;
122	info.high_limit = TASK_SIZE;
123	return vm_unmapped_area(&info);
124}
125
126unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0,
127	unsigned long len, unsigned long pgoff, unsigned long flags)
128{
129	return arch_get_unmapped_area_common(filp,
130			addr0, len, pgoff, flags, UP);
131}
132
133/*
134 * There is no need to export this but sched.h declares the function as
135 * extern so making it static here results in an error.
136 */
137unsigned long arch_get_unmapped_area_topdown(struct file *filp,
138	unsigned long addr0, unsigned long len, unsigned long pgoff,
139	unsigned long flags)
140{
141	return arch_get_unmapped_area_common(filp,
142			addr0, len, pgoff, flags, DOWN);
143}
144
145unsigned long arch_mmap_rnd(void)
146{
147	unsigned long rnd;
148
149	rnd = (unsigned long)get_random_int();
150	rnd <<= PAGE_SHIFT;
151	if (TASK_IS_32BIT_ADDR)
152		rnd &= 0xfffffful;
153	else
154		rnd &= 0xffffffful;
155
156	return rnd;
157}
158
159void arch_pick_mmap_layout(struct mm_struct *mm)
160{
161	unsigned long random_factor = 0UL;
162
163	if (current->flags & PF_RANDOMIZE)
164		random_factor = arch_mmap_rnd();
165
166	if (mmap_is_legacy()) {
167		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
168		mm->get_unmapped_area = arch_get_unmapped_area;
169	} else {
170		mm->mmap_base = mmap_base(random_factor);
171		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
172	}
173}
174
175static inline unsigned long brk_rnd(void)
176{
177	unsigned long rnd = get_random_int();
178
179	rnd = rnd << PAGE_SHIFT;
180	/* 8MB for 32bit, 256MB for 64bit */
181	if (TASK_IS_32BIT_ADDR)
182		rnd = rnd & 0x7ffffful;
183	else
184		rnd = rnd & 0xffffffful;
185
186	return rnd;
187}
188
189unsigned long arch_randomize_brk(struct mm_struct *mm)
190{
191	unsigned long base = mm->brk;
192	unsigned long ret;
193
194	ret = PAGE_ALIGN(base + brk_rnd());
195
196	if (ret < mm->brk)
197		return mm->brk;
198
199	return ret;
200}
201
202int __virt_addr_valid(const volatile void *kaddr)
203{
204	return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
205}
206EXPORT_SYMBOL_GPL(__virt_addr_valid);
207