arch/arm64/mm/pageattr.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2014, The Linux Foundation. All rights reserved.
   4  */
   5 #include <linux/kernel.h>
   6 #include <linux/mm.h>
   7 #include <linux/module.h>
   8 #include <linux/sched.h>
   9 #include <linux/vmalloc.h>
  10
  11 #include <asm/cacheflush.h>
  12 #include <asm/set_memory.h>
  13 #include <asm/tlbflush.h>
  14 #include <asm/kfence.h>
  15
  16 struct page_change_data {
  17         pgprot_t set_mask;
  18         pgprot_t clear_mask;
  19 };
  20
  21 bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
  22
  23 bool can_set_direct_map(void)
  24 {
  25         /*
  26          * rodata_full and DEBUG_PAGEALLOC require linear map to be
  27          * mapped at page granularity, so that it is possible to
  28          * protect/unprotect single pages.
  29          *
  30          * KFENCE pool requires page-granular mapping if initialized late.
  31          */
  32         return rodata_full || debug_pagealloc_enabled() ||
  33                arm64_kfence_can_set_direct_map();
  34 }
  35
  36 static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
  37 {
  38         struct page_change_data *cdata = data;
  39         pte_t pte = READ_ONCE(*ptep);
  40
  41         pte = clear_pte_bit(pte, cdata->clear_mask);
  42         pte = set_pte_bit(pte, cdata->set_mask);
  43
  44         set_pte(ptep, pte);
  45         return 0;
  46 }
  47
  48 /*
  49  * This function assumes that the range is mapped with PAGE_SIZE pages.
  50  */
  51 static int __change_memory_common(unsigned long start, unsigned long size,
  52                                 pgprot_t set_mask, pgprot_t clear_mask)
  53 {
  54         struct page_change_data data;
  55         int ret;
  56
  57         data.set_mask = set_mask;
  58         data.clear_mask = clear_mask;
  59
  60         ret = apply_to_page_range(&init_mm, start, size, change_page_range,
  61                                         &data);
  62
  63         flush_tlb_kernel_range(start, start + size);
  64         return ret;
  65 }
  66
  67 static int change_memory_common(unsigned long addr, int numpages,
  68                                 pgprot_t set_mask, pgprot_t clear_mask)
  69 {
  70         unsigned long start = addr;
  71         unsigned long size = PAGE_SIZE * numpages;
  72         unsigned long end = start + size;
  73         struct vm_struct *area;
  74         int i;
  75
  76         if (!PAGE_ALIGNED(addr)) {
  77                 start &= PAGE_MASK;
  78                 end = start + size;
  79                 WARN_ON_ONCE(1);
  80         }
  81
  82         /*
  83          * Kernel VA mappings are always live, and splitting live section
  84          * mappings into page mappings may cause TLB conflicts. This means
  85          * we have to ensure that changing the permission bits of the range
  86          * we are operating on does not result in such splitting.
  87          *
  88          * Let's restrict ourselves to mappings created by vmalloc (or vmap).
  89          * Those are guaranteed to consist entirely of page mappings, and
  90          * splitting is never needed.
  91          *
  92          * So check whether the [addr, addr + size) interval is entirely
  93          * covered by precisely one VM area that has the VM_ALLOC flag set.
  94          */
  95         area = find_vm_area((void *)addr);
  96         if (!area ||
  97             end > (unsigned long)kasan_reset_tag(area->addr) + area->size ||
  98             !(area->flags & VM_ALLOC))
  99                 return -EINVAL;
 100
 101         if (!numpages)
 102                 return 0;
 103
 104         /*
 105          * If we are manipulating read-only permissions, apply the same
 106          * change to the linear mapping of the pages that back this VM area.
 107          */
 108         if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
 109                             pgprot_val(clear_mask) == PTE_RDONLY)) {
 110                 for (i = 0; i < area->nr_pages; i++) {
 111                         __change_memory_common((u64)page_address(area->pages[i]),
 112                                                PAGE_SIZE, set_mask, clear_mask);
 113                 }
 114         }
 115
 116         /*
 117          * Get rid of potentially aliasing lazily unmapped vm areas that may
 118          * have permissions set that deviate from the ones we are setting here.
 119          */
 120         vm_unmap_aliases();
 121
 122         return __change_memory_common(start, size, set_mask, clear_mask);
 123 }
 124
 125 int set_memory_ro(unsigned long addr, int numpages)
 126 {
 127         return change_memory_common(addr, numpages,
 128                                         __pgprot(PTE_RDONLY),
 129                                         __pgprot(PTE_WRITE));
 130 }
 131
 132 int set_memory_rw(unsigned long addr, int numpages)
 133 {
 134         return change_memory_common(addr, numpages,
 135                                         __pgprot(PTE_WRITE),
 136                                         __pgprot(PTE_RDONLY));
 137 }
 138
 139 int set_memory_nx(unsigned long addr, int numpages)
 140 {
 141         return change_memory_common(addr, numpages,
 142                                         __pgprot(PTE_PXN),
 143                                         __pgprot(PTE_MAYBE_GP));
 144 }
 145
 146 int set_memory_x(unsigned long addr, int numpages)
 147 {
 148         return change_memory_common(addr, numpages,
 149                                         __pgprot(PTE_MAYBE_GP),
 150                                         __pgprot(PTE_PXN));
 151 }
 152
 153 int set_memory_valid(unsigned long addr, int numpages, int enable)
 154 {
 155         if (enable)
 156                 return __change_memory_common(addr, PAGE_SIZE * numpages,
 157                                         __pgprot(PTE_VALID),
 158                                         __pgprot(0));
 159         else
 160                 return __change_memory_common(addr, PAGE_SIZE * numpages,
 161                                         __pgprot(0),
 162                                         __pgprot(PTE_VALID));
 163 }
 164
 165 int set_direct_map_invalid_noflush(struct page *page)
 166 {
 167         struct page_change_data data = {
 168                 .set_mask = __pgprot(0),
 169                 .clear_mask = __pgprot(PTE_VALID),
 170         };
 171
 172         if (!can_set_direct_map())
 173                 return 0;
 174
 175         return apply_to_page_range(&init_mm,
 176                                    (unsigned long)page_address(page),
 177                                    PAGE_SIZE, change_page_range, &data);
 178 }
 179
 180 int set_direct_map_default_noflush(struct page *page)
 181 {
 182         struct page_change_data data = {
 183                 .set_mask = __pgprot(PTE_VALID | PTE_WRITE),
 184                 .clear_mask = __pgprot(PTE_RDONLY),
 185         };
 186
 187         if (!can_set_direct_map())
 188                 return 0;
 189
 190         return apply_to_page_range(&init_mm,
 191                                    (unsigned long)page_address(page),
 192                                    PAGE_SIZE, change_page_range, &data);
 193 }
 194
 195 #ifdef CONFIG_DEBUG_PAGEALLOC
 196 void __kernel_map_pages(struct page *page, int numpages, int enable)
 197 {
 198         if (!can_set_direct_map())
 199                 return;
 200
 201         set_memory_valid((unsigned long)page_address(page), numpages, enable);
 202 }
 203 #endif /* CONFIG_DEBUG_PAGEALLOC */
 204
 205 /*
 206  * This function is used to determine if a linear map page has been marked as
 207  * not-valid. Walk the page table and check the PTE_VALID bit.
 208  *
 209  * Because this is only called on the kernel linear map,  p?d_sect() implies
 210  * p?d_present(). When debug_pagealloc is enabled, sections mappings are
 211  * disabled.
 212  */
 213 bool kernel_page_present(struct page *page)
 214 {
 215         pgd_t *pgdp;
 216         p4d_t *p4dp;
 217         pud_t *pudp, pud;
 218         pmd_t *pmdp, pmd;
 219         pte_t *ptep;
 220         unsigned long addr = (unsigned long)page_address(page);
 221
 222         if (!can_set_direct_map())
 223                 return true;
 224
 225         pgdp = pgd_offset_k(addr);
 226         if (pgd_none(READ_ONCE(*pgdp)))
 227                 return false;
 228
 229         p4dp = p4d_offset(pgdp, addr);
 230         if (p4d_none(READ_ONCE(*p4dp)))
 231                 return false;
 232
 233         pudp = pud_offset(p4dp, addr);
 234         pud = READ_ONCE(*pudp);
 235         if (pud_none(pud))
 236                 return false;
 237         if (pud_sect(pud))
 238                 return true;
 239
 240         pmdp = pmd_offset(pudp, addr);
 241         pmd = READ_ONCE(*pmdp);
 242         if (pmd_none(pmd))
 243                 return false;
 244         if (pmd_sect(pmd))
 245                 return true;
 246
 247         ptep = pte_offset_kernel(pmdp, addr);
 248         return pte_valid(READ_ONCE(*ptep));
 249 }