2 * Flexible mmap layout support
4 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
7 * Copyright 2003-2009 Red Hat Inc.
9 * Copyright 2005 Andi Kleen, SUSE Labs.
10 * Copyright 2007 Jiri Kosina, SUSE Labs.
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
27 #include <linux/personality.h>
29 #include <linux/random.h>
30 #include <linux/limits.h>
31 #include <linux/sched/signal.h>
32 #include <linux/sched/mm.h>
33 #include <linux/compat.h>
36 struct va_alignment __read_mostly va_align = {
40 unsigned long task_size_32bit(void)
42 return IA32_PAGE_OFFSET;
45 unsigned long task_size_64bit(int full_addr_space)
47 return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
50 static unsigned long stack_maxrandom_size(unsigned long task_size)
52 unsigned long max = 0;
53 if (current->flags & PF_RANDOMIZE) {
54 max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit());
62 # define mmap32_rnd_bits mmap_rnd_compat_bits
63 # define mmap64_rnd_bits mmap_rnd_bits
65 # define mmap32_rnd_bits mmap_rnd_bits
66 # define mmap64_rnd_bits mmap_rnd_bits
69 #define SIZE_128M (128 * 1024 * 1024UL)
71 static int mmap_is_legacy(void)
73 if (current->personality & ADDR_COMPAT_LAYOUT)
76 return sysctl_legacy_va_layout;
79 static unsigned long arch_rnd(unsigned int rndbits)
81 if (!(current->flags & PF_RANDOMIZE))
83 return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
86 unsigned long arch_mmap_rnd(void)
88 return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
91 static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)
93 unsigned long gap = rlimit(RLIMIT_STACK);
94 unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
95 unsigned long gap_min, gap_max;
97 /* Values close to RLIM_INFINITY can overflow. */
102 * Top of mmap area (just below the process stack).
103 * Leave an at least ~128 MB hole with possible stack randomization.
106 gap_max = (task_size / 6) * 5;
110 else if (gap > gap_max)
113 return PAGE_ALIGN(task_size - gap - rnd);
116 static unsigned long mmap_legacy_base(unsigned long rnd,
117 unsigned long task_size)
119 return __TASK_UNMAPPED_BASE(task_size) + rnd;
123 * This function, called very early during the creation of a new
124 * process VM image, sets up which VM layout function to use:
126 static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
127 unsigned long random_factor, unsigned long task_size)
129 *legacy_base = mmap_legacy_base(random_factor, task_size);
130 if (mmap_is_legacy())
131 *base = *legacy_base;
133 *base = mmap_base(random_factor, task_size);
136 void arch_pick_mmap_layout(struct mm_struct *mm)
138 if (mmap_is_legacy())
139 mm->get_unmapped_area = arch_get_unmapped_area;
141 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
143 arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
144 arch_rnd(mmap64_rnd_bits), task_size_64bit(0));
146 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
148 * The mmap syscall mapping base decision depends solely on the
149 * syscall type (64-bit or compat). This applies for 64bit
150 * applications and 32bit applications. The 64bit syscall uses
151 * mmap_base, the compat syscall uses mmap_compat_base.
153 arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
154 arch_rnd(mmap32_rnd_bits), task_size_32bit());
158 unsigned long get_mmap_base(int is_legacy)
160 struct mm_struct *mm = current->mm;
162 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
163 if (in_compat_syscall()) {
164 return is_legacy ? mm->mmap_compat_legacy_base
165 : mm->mmap_compat_base;
168 return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
171 const char *arch_vma_name(struct vm_area_struct *vma)
173 if (vma->vm_flags & VM_MPX)
179 * Only allow root to set high MMIO mappings to PROT_NONE.
180 * This prevents an unpriv. user to set them to PROT_NONE and invert
181 * them, then pointing to valid memory for L1TF speculation.
183 * Note: for locked down kernels may want to disable the root override.
185 bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot)
187 if (!boot_cpu_has_bug(X86_BUG_L1TF))
189 if (!__pte_needs_invert(pgprot_val(prot)))
191 /* If it's real memory always allow */
194 if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN))