143 lines
3.5 KiB
C
143 lines
3.5 KiB
C
/*
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* Based on arch/arm/mm/mmap.c
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*
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* Copyright (C) 2012 ARM Ltd.
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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 version 2 as
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* published by the Free Software Foundation.
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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, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/elf.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/export.h>
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#include <linux/shm.h>
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#include <linux/sched.h>
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#include <linux/io.h>
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#include <linux/personality.h>
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#include <linux/random.h>
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#include <asm/cputype.h>
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/*
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* Leave enough space between the mmap area and the stack to honour ulimit in
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* the face of randomisation.
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*/
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#define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1))
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#define MAX_GAP (STACK_TOP/6*5)
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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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if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
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return 1;
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return sysctl_legacy_va_layout;
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}
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/*
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* Since get_random_int() returns the same value within a 1 jiffy window, we
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* will almost always get the same randomisation for the stack and mmap
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* region. This will mean the relative distance between stack and mmap will be
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* the same.
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*
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* To avoid this we can shift the randomness by 1 bit.
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*/
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static unsigned long mmap_rnd(void)
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{
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unsigned long rnd = 0;
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if (current->flags & PF_RANDOMIZE)
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rnd = (long)get_random_int() & (STACK_RND_MASK >> 1);
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return rnd << (PAGE_SHIFT + 1);
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}
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static unsigned long mmap_base(void)
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{
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unsigned long gap = rlimit(RLIMIT_STACK);
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if (gap < MIN_GAP)
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gap = MIN_GAP;
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else if (gap > MAX_GAP)
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gap = MAX_GAP;
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return PAGE_ALIGN(STACK_TOP - gap - mmap_rnd());
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}
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/*
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* This function, called very early during the creation of a new process VM
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* image, sets up which VM layout function to use:
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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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/*
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* Fall back to the standard layout if the personality bit is set, or
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* if the expected stack growth is unlimited:
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*/
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if (mmap_is_legacy()) {
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mm->mmap_base = TASK_UNMAPPED_BASE;
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mm->get_unmapped_area = arch_get_unmapped_area;
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} else {
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mm->mmap_base = mmap_base();
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mm->get_unmapped_area = arch_get_unmapped_area_topdown;
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}
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}
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EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
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/*
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* You really shouldn't be using read() or write() on /dev/mem. This might go
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* away in the future.
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*/
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int valid_phys_addr_range(unsigned long addr, size_t size)
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{
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if (addr < PHYS_OFFSET)
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return 0;
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if (addr + size > __pa(high_memory - 1) + 1)
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return 0;
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return 1;
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}
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/*
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* Do not allow /dev/mem mappings beyond the supported physical range.
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*/
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int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
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{
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return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
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}
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#ifdef CONFIG_STRICT_DEVMEM
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#include <linux/ioport.h>
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/*
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* devmem_is_allowed() checks to see if /dev/mem access to a certain address
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* is valid. The argument is a physical page number. We mimic x86 here by
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* disallowing access to system RAM as well as device-exclusive MMIO regions.
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* This effectively disable read()/write() on /dev/mem.
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*/
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int devmem_is_allowed(unsigned long pfn)
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{
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if (iomem_is_exclusive(pfn << PAGE_SHIFT))
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return 0;
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if (!page_is_ram(pfn))
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return 1;
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return 0;
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}
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#endif
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