177 lines
4.6 KiB
C
177 lines
4.6 KiB
C
/*
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* Flexible mmap layout support
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*
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* Based on code by Ingo Molnar and Andi Kleen, copyrighted
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* as follows:
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*
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* Copyright 2003-2009 Red Hat Inc.
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* All Rights Reserved.
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* Copyright 2005 Andi Kleen, SUSE Labs.
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* Copyright 2007 Jiri Kosina, SUSE Labs.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/personality.h>
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#include <linux/mm.h>
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#include <linux/random.h>
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#include <linux/limits.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/mm.h>
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#include <linux/compat.h>
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#include <asm/elf.h>
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struct va_alignment __read_mostly va_align = {
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.flags = -1,
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};
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unsigned long task_size_32bit(void)
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{
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return IA32_PAGE_OFFSET;
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}
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unsigned long task_size_64bit(int full_addr_space)
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{
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return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
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}
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static unsigned long stack_maxrandom_size(unsigned long task_size)
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{
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unsigned long max = 0;
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if (current->flags & PF_RANDOMIZE) {
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max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit());
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max <<= PAGE_SHIFT;
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}
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return max;
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}
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#ifdef CONFIG_COMPAT
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# define mmap32_rnd_bits mmap_rnd_compat_bits
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# define mmap64_rnd_bits mmap_rnd_bits
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#else
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# define mmap32_rnd_bits mmap_rnd_bits
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# define mmap64_rnd_bits mmap_rnd_bits
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#endif
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#define SIZE_128M (128 * 1024 * 1024UL)
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static int mmap_is_legacy(void)
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{
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if (current->personality & ADDR_COMPAT_LAYOUT)
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return 1;
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return sysctl_legacy_va_layout;
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}
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static unsigned long arch_rnd(unsigned int rndbits)
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{
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if (!(current->flags & PF_RANDOMIZE))
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return 0;
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return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
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}
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unsigned long arch_mmap_rnd(void)
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{
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return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
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}
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static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)
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{
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unsigned long gap = rlimit(RLIMIT_STACK);
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unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
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unsigned long gap_min, gap_max;
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/* Values close to RLIM_INFINITY can overflow. */
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if (gap + pad > gap)
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gap += pad;
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/*
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* Top of mmap area (just below the process stack).
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* Leave an at least ~128 MB hole with possible stack randomization.
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*/
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gap_min = SIZE_128M;
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gap_max = (task_size / 6) * 5;
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if (gap < gap_min)
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gap = gap_min;
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else if (gap > gap_max)
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gap = gap_max;
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return PAGE_ALIGN(task_size - gap - rnd);
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}
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static unsigned long mmap_legacy_base(unsigned long rnd,
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unsigned long task_size)
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{
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return __TASK_UNMAPPED_BASE(task_size) + rnd;
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}
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/*
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* This function, called very early during the creation of a new
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* process VM image, sets up which VM layout function to use:
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*/
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static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
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unsigned long random_factor, unsigned long task_size)
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{
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*legacy_base = mmap_legacy_base(random_factor, task_size);
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if (mmap_is_legacy())
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*base = *legacy_base;
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else
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*base = mmap_base(random_factor, task_size);
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}
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void arch_pick_mmap_layout(struct mm_struct *mm)
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{
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if (mmap_is_legacy())
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mm->get_unmapped_area = arch_get_unmapped_area;
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else
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mm->get_unmapped_area = arch_get_unmapped_area_topdown;
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arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
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arch_rnd(mmap64_rnd_bits), task_size_64bit(0));
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#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
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/*
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* The mmap syscall mapping base decision depends solely on the
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* syscall type (64-bit or compat). This applies for 64bit
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* applications and 32bit applications. The 64bit syscall uses
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* mmap_base, the compat syscall uses mmap_compat_base.
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*/
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arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
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arch_rnd(mmap32_rnd_bits), task_size_32bit());
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#endif
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}
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unsigned long get_mmap_base(int is_legacy)
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{
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struct mm_struct *mm = current->mm;
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#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
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if (in_compat_syscall()) {
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return is_legacy ? mm->mmap_compat_legacy_base
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: mm->mmap_compat_base;
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}
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#endif
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return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
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}
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const char *arch_vma_name(struct vm_area_struct *vma)
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{
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if (vma->vm_flags & VM_MPX)
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return "[mpx]";
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return NULL;
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}
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