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/*
* 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;
}
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;
int ret;
struct page_change_data data;
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;
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, end);
return ret;
}
int set_memory_ro(unsigned long addr, int numpages)
{
return change_memory_common(addr, numpages,
__pgprot(PTE_RDONLY),
__pgprot(PTE_WRITE));
}
int set_memory_rw(unsigned long addr, int numpages)
{
return change_memory_common(addr, numpages,
__pgprot(PTE_WRITE),
__pgprot(PTE_RDONLY));
}
int set_memory_nx(unsigned long addr, int numpages)
{
return change_memory_common(addr, numpages,
__pgprot(PTE_PXN),
__pgprot(0));
}
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));
}
EXPORT_SYMBOL_GPL(set_memory_x);
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