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Linux/arch/arm64/mm/pageattr.c

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  1 /*
  2  * Copyright (c) 2014, The Linux Foundation. All rights reserved.
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License version 2 and
  6  * only version 2 as published by the Free Software Foundation.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11  * GNU General Public License for more details.
 12  */
 13 #include <linux/kernel.h>
 14 #include <linux/mm.h>
 15 #include <linux/module.h>
 16 #include <linux/sched.h>
 17 #include <linux/vmalloc.h>
 18 
 19 #include <asm/pgtable.h>
 20 #include <asm/set_memory.h>
 21 #include <asm/tlbflush.h>
 22 
 23 struct page_change_data {
 24         pgprot_t set_mask;
 25         pgprot_t clear_mask;
 26 };
 27 
 28 bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
 29 
 30 static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
 31                         void *data)
 32 {
 33         struct page_change_data *cdata = data;
 34         pte_t pte = READ_ONCE(*ptep);
 35 
 36         pte = clear_pte_bit(pte, cdata->clear_mask);
 37         pte = set_pte_bit(pte, cdata->set_mask);
 38 
 39         set_pte(ptep, pte);
 40         return 0;
 41 }
 42 
 43 /*
 44  * This function assumes that the range is mapped with PAGE_SIZE pages.
 45  */
 46 static int __change_memory_common(unsigned long start, unsigned long size,
 47                                 pgprot_t set_mask, pgprot_t clear_mask)
 48 {
 49         struct page_change_data data;
 50         int ret;
 51 
 52         data.set_mask = set_mask;
 53         data.clear_mask = clear_mask;
 54 
 55         ret = apply_to_page_range(&init_mm, start, size, change_page_range,
 56                                         &data);
 57 
 58         flush_tlb_kernel_range(start, start + size);
 59         return ret;
 60 }
 61 
 62 static int change_memory_common(unsigned long addr, int numpages,
 63                                 pgprot_t set_mask, pgprot_t clear_mask)
 64 {
 65         unsigned long start = addr;
 66         unsigned long size = PAGE_SIZE*numpages;
 67         unsigned long end = start + size;
 68         struct vm_struct *area;
 69         int i;
 70 
 71         if (!PAGE_ALIGNED(addr)) {
 72                 start &= PAGE_MASK;
 73                 end = start + size;
 74                 WARN_ON_ONCE(1);
 75         }
 76 
 77         /*
 78          * Kernel VA mappings are always live, and splitting live section
 79          * mappings into page mappings may cause TLB conflicts. This means
 80          * we have to ensure that changing the permission bits of the range
 81          * we are operating on does not result in such splitting.
 82          *
 83          * Let's restrict ourselves to mappings created by vmalloc (or vmap).
 84          * Those are guaranteed to consist entirely of page mappings, and
 85          * splitting is never needed.
 86          *
 87          * So check whether the [addr, addr + size) interval is entirely
 88          * covered by precisely one VM area that has the VM_ALLOC flag set.
 89          */
 90         area = find_vm_area((void *)addr);
 91         if (!area ||
 92             end > (unsigned long)area->addr + area->size ||
 93             !(area->flags & VM_ALLOC))
 94                 return -EINVAL;
 95 
 96         if (!numpages)
 97                 return 0;
 98 
 99         /*
100          * If we are manipulating read-only permissions, apply the same
101          * change to the linear mapping of the pages that back this VM area.
102          */
103         if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
104                             pgprot_val(clear_mask) == PTE_RDONLY)) {
105                 for (i = 0; i < area->nr_pages; i++) {
106                         __change_memory_common((u64)page_address(area->pages[i]),
107                                                PAGE_SIZE, set_mask, clear_mask);
108                 }
109         }
110 
111         /*
112          * Get rid of potentially aliasing lazily unmapped vm areas that may
113          * have permissions set that deviate from the ones we are setting here.
114          */
115         vm_unmap_aliases();
116 
117         return __change_memory_common(start, size, set_mask, clear_mask);
118 }
119 
120 int set_memory_ro(unsigned long addr, int numpages)
121 {
122         return change_memory_common(addr, numpages,
123                                         __pgprot(PTE_RDONLY),
124                                         __pgprot(PTE_WRITE));
125 }
126 
127 int set_memory_rw(unsigned long addr, int numpages)
128 {
129         return change_memory_common(addr, numpages,
130                                         __pgprot(PTE_WRITE),
131                                         __pgprot(PTE_RDONLY));
132 }
133 
134 int set_memory_nx(unsigned long addr, int numpages)
135 {
136         return change_memory_common(addr, numpages,
137                                         __pgprot(PTE_PXN),
138                                         __pgprot(0));
139 }
140 EXPORT_SYMBOL_GPL(set_memory_nx);
141 
142 int set_memory_x(unsigned long addr, int numpages)
143 {
144         return change_memory_common(addr, numpages,
145                                         __pgprot(0),
146                                         __pgprot(PTE_PXN));
147 }
148 EXPORT_SYMBOL_GPL(set_memory_x);
149 
150 int set_memory_valid(unsigned long addr, int numpages, int enable)
151 {
152         if (enable)
153                 return __change_memory_common(addr, PAGE_SIZE * numpages,
154                                         __pgprot(PTE_VALID),
155                                         __pgprot(0));
156         else
157                 return __change_memory_common(addr, PAGE_SIZE * numpages,
158                                         __pgprot(0),
159                                         __pgprot(PTE_VALID));
160 }
161 
162 #ifdef CONFIG_DEBUG_PAGEALLOC
163 void __kernel_map_pages(struct page *page, int numpages, int enable)
164 {
165         set_memory_valid((unsigned long)page_address(page), numpages, enable);
166 }
167 #ifdef CONFIG_HIBERNATION
168 /*
169  * When built with CONFIG_DEBUG_PAGEALLOC and CONFIG_HIBERNATION, this function
170  * is used to determine if a linear map page has been marked as not-valid by
171  * CONFIG_DEBUG_PAGEALLOC. Walk the page table and check the PTE_VALID bit.
172  * This is based on kern_addr_valid(), which almost does what we need.
173  *
174  * Because this is only called on the kernel linear map,  p?d_sect() implies
175  * p?d_present(). When debug_pagealloc is enabled, sections mappings are
176  * disabled.
177  */
178 bool kernel_page_present(struct page *page)
179 {
180         pgd_t *pgdp;
181         pud_t *pudp, pud;
182         pmd_t *pmdp, pmd;
183         pte_t *ptep;
184         unsigned long addr = (unsigned long)page_address(page);
185 
186         pgdp = pgd_offset_k(addr);
187         if (pgd_none(READ_ONCE(*pgdp)))
188                 return false;
189 
190         pudp = pud_offset(pgdp, addr);
191         pud = READ_ONCE(*pudp);
192         if (pud_none(pud))
193                 return false;
194         if (pud_sect(pud))
195                 return true;
196 
197         pmdp = pmd_offset(pudp, addr);
198         pmd = READ_ONCE(*pmdp);
199         if (pmd_none(pmd))
200                 return false;
201         if (pmd_sect(pmd))
202                 return true;
203 
204         ptep = pte_offset_kernel(pmdp, addr);
205         return pte_valid(READ_ONCE(*ptep));
206 }
207 #endif /* CONFIG_HIBERNATION */
208 #endif /* CONFIG_DEBUG_PAGEALLOC */
209 

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