cregit-Linux how code gets into the kernel

Release 4.8 arch/arm64/mm/pageattr.c

Directory: arch/arm64/mm
/*
 * Copyright (c) 2014, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/vmalloc.h>

#include <asm/pgtable.h>
#include <asm/tlbflush.h>


struct page_change_data {
	
pgprot_t set_mask;
	
pgprot_t clear_mask;
};


static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr, void *data) { struct page_change_data *cdata = data; pte_t pte = *ptep; pte = clear_pte_bit(pte, cdata->clear_mask); pte = set_pte_bit(pte, cdata->set_mask); set_pte(ptep, pte); return 0; }

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/* * This function assumes that the range is mapped with PAGE_SIZE pages. */
static int __change_memory_common(unsigned long start, unsigned long size, pgprot_t set_mask, pgprot_t clear_mask) { struct page_change_data data; int ret; data.set_mask = set_mask; data.clear_mask = clear_mask; ret = apply_to_page_range(&init_mm, start, size, change_page_range, &data); flush_tlb_kernel_range(start, start + size); return ret; }

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static int change_memory_common(unsigned long addr, int numpages, pgprot_t set_mask, pgprot_t clear_mask) { unsigned long start = addr; unsigned long size = PAGE_SIZE*numpages; unsigned long end = start + size; struct vm_struct *area; if (!PAGE_ALIGNED(addr)) { start &= PAGE_MASK; end = start + size; WARN_ON_ONCE(1); } /* * Kernel VA mappings are always live, and splitting live section * mappings into page mappings may cause TLB conflicts. This means * we have to ensure that changing the permission bits of the range * we are operating on does not result in such splitting. * * Let's restrict ourselves to mappings created by vmalloc (or vmap). * Those are guaranteed to consist entirely of page mappings, and * splitting is never needed. * * So check whether the [addr, addr + size) interval is entirely * covered by precisely one VM area that has the VM_ALLOC flag set. */ area = find_vm_area((void *)addr); if (!area || end > (unsigned long)area->addr + area->size || !(area->flags & VM_ALLOC)) return -EINVAL; if (!numpages) return 0; return __change_memory_common(start, size, set_mask, clear_mask); }

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int set_memory_ro(unsigned long addr, int numpages) { return change_memory_common(addr, numpages, __pgprot(PTE_RDONLY), __pgprot(PTE_WRITE)); }

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int set_memory_rw(unsigned long addr, int numpages) { return change_memory_common(addr, numpages, __pgprot(PTE_WRITE), __pgprot(PTE_RDONLY)); }

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int set_memory_nx(unsigned long addr, int numpages) { return change_memory_common(addr, numpages, __pgprot(PTE_PXN), __pgprot(0)); }

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EXPORT_SYMBOL_GPL(set_memory_nx);
int set_memory_x(unsigned long addr, int numpages) { return change_memory_common(addr, numpages, __pgprot(0), __pgprot(PTE_PXN)); }

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EXPORT_SYMBOL_GPL(set_memory_x); #ifdef CONFIG_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable) { unsigned long addr = (unsigned long) page_address(page); if (enable) __change_memory_common(addr, PAGE_SIZE * numpages, __pgprot(PTE_VALID), __pgprot(0)); else __change_memory_common(addr, PAGE_SIZE * numpages, __pgprot(0), __pgprot(PTE_VALID)); }

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#endif

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Directory: arch/arm64/mm
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