mm/debug_vm_pgtable.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * This kernel test validates architecture page table helpers and
   4  * accessors and helps in verifying their continued compliance with
   5  * expected generic MM semantics.
   6  *
   7  * Copyright (C) 2019 ARM Ltd.
   8  *
   9  * Author: Anshuman Khandual <anshuman.khandual@arm.com>
  10  */
  11 #define pr_fmt(fmt) "debug_vm_pgtable: %s: " fmt, __func__
  12
  13 #include <linux/gfp.h>
  14 #include <linux/highmem.h>
  15 #include <linux/hugetlb.h>
  16 #include <linux/kernel.h>
  17 #include <linux/kconfig.h>
  18 #include <linux/mm.h>
  19 #include <linux/mman.h>
  20 #include <linux/mm_types.h>
  21 #include <linux/module.h>
  22 #include <linux/pfn_t.h>
  23 #include <linux/printk.h>
  24 #include <linux/random.h>
  25 #include <linux/spinlock.h>
  26 #include <linux/swap.h>
  27 #include <linux/swapops.h>
  28 #include <linux/start_kernel.h>
  29 #include <linux/sched/mm.h>
  30 #include <asm/pgalloc.h>
  31
  32 #define VMFLAGS (VM_READ|VM_WRITE|VM_EXEC)
  33
  34 /*
  35  * On s390 platform, the lower 4 bits are used to identify given page table
  36  * entry type. But these bits might affect the ability to clear entries with
  37  * pxx_clear() because of how dynamic page table folding works on s390. So
  38  * while loading up the entries do not change the lower 4 bits. It does not
  39  * have affect any other platform.
  40  */
  41 #define S390_MASK_BITS  4
  42 #define RANDOM_ORVALUE  GENMASK(BITS_PER_LONG - 1, S390_MASK_BITS)
  43 #define RANDOM_NZVALUE  GENMASK(7, 0)
  44
  45 static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot)
  46 {
  47         pte_t pte = pfn_pte(pfn, prot);
  48
  49         WARN_ON(!pte_same(pte, pte));
  50         WARN_ON(!pte_young(pte_mkyoung(pte_mkold(pte))));
  51         WARN_ON(!pte_dirty(pte_mkdirty(pte_mkclean(pte))));
  52         WARN_ON(!pte_write(pte_mkwrite(pte_wrprotect(pte))));
  53         WARN_ON(pte_young(pte_mkold(pte_mkyoung(pte))));
  54         WARN_ON(pte_dirty(pte_mkclean(pte_mkdirty(pte))));
  55         WARN_ON(pte_write(pte_wrprotect(pte_mkwrite(pte))));
  56 }
  57
  58 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  59 static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
  60 {
  61         pmd_t pmd = pfn_pmd(pfn, prot);
  62
  63         if (!has_transparent_hugepage())
  64                 return;
  65
  66         WARN_ON(!pmd_same(pmd, pmd));
  67         WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
  68         WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
  69         WARN_ON(!pmd_write(pmd_mkwrite(pmd_wrprotect(pmd))));
  70         WARN_ON(pmd_young(pmd_mkold(pmd_mkyoung(pmd))));
  71         WARN_ON(pmd_dirty(pmd_mkclean(pmd_mkdirty(pmd))));
  72         WARN_ON(pmd_write(pmd_wrprotect(pmd_mkwrite(pmd))));
  73         /*
  74          * A huge page does not point to next level page table
  75          * entry. Hence this must qualify as pmd_bad().
  76          */
  77         WARN_ON(!pmd_bad(pmd_mkhuge(pmd)));
  78 }
  79
  80 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
  81 static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot)
  82 {
  83         pud_t pud = pfn_pud(pfn, prot);
  84
  85         if (!has_transparent_hugepage())
  86                 return;
  87
  88         WARN_ON(!pud_same(pud, pud));
  89         WARN_ON(!pud_young(pud_mkyoung(pud_mkold(pud))));
  90         WARN_ON(!pud_write(pud_mkwrite(pud_wrprotect(pud))));
  91         WARN_ON(pud_write(pud_wrprotect(pud_mkwrite(pud))));
  92         WARN_ON(pud_young(pud_mkold(pud_mkyoung(pud))));
  93
  94         if (mm_pmd_folded(mm))
  95                 return;
  96
  97         /*
  98          * A huge page does not point to next level page table
  99          * entry. Hence this must qualify as pud_bad().
 100          */
 101         WARN_ON(!pud_bad(pud_mkhuge(pud)));
 102 }
 103 #else  /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 104 static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) { }
 105 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 106 #else  /* !CONFIG_TRANSPARENT_HUGEPAGE */
 107 static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) { }
 108 static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) { }
 109 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 110
 111 static void __init p4d_basic_tests(unsigned long pfn, pgprot_t prot)
 112 {
 113         p4d_t p4d;
 114
 115         memset(&p4d, RANDOM_NZVALUE, sizeof(p4d_t));
 116         WARN_ON(!p4d_same(p4d, p4d));
 117 }
 118
 119 static void __init pgd_basic_tests(unsigned long pfn, pgprot_t prot)
 120 {
 121         pgd_t pgd;
 122
 123         memset(&pgd, RANDOM_NZVALUE, sizeof(pgd_t));
 124         WARN_ON(!pgd_same(pgd, pgd));
 125 }
 126
 127 #ifndef __PAGETABLE_PUD_FOLDED
 128 static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp)
 129 {
 130         pud_t pud = READ_ONCE(*pudp);
 131
 132         if (mm_pmd_folded(mm))
 133                 return;
 134
 135         pud = __pud(pud_val(pud) | RANDOM_ORVALUE);
 136         WRITE_ONCE(*pudp, pud);
 137         pud_clear(pudp);
 138         pud = READ_ONCE(*pudp);
 139         WARN_ON(!pud_none(pud));
 140 }
 141
 142 static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
 143                                       pmd_t *pmdp)
 144 {
 145         pud_t pud;
 146
 147         if (mm_pmd_folded(mm))
 148                 return;
 149         /*
 150          * This entry points to next level page table page.
 151          * Hence this must not qualify as pud_bad().
 152          */
 153         pmd_clear(pmdp);
 154         pud_clear(pudp);
 155         pud_populate(mm, pudp, pmdp);
 156         pud = READ_ONCE(*pudp);
 157         WARN_ON(pud_bad(pud));
 158 }
 159 #else  /* !__PAGETABLE_PUD_FOLDED */
 160 static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp) { }
 161 static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
 162                                       pmd_t *pmdp)
 163 {
 164 }
 165 #endif /* PAGETABLE_PUD_FOLDED */
 166
 167 #ifndef __PAGETABLE_P4D_FOLDED
 168 static void __init p4d_clear_tests(struct mm_struct *mm, p4d_t *p4dp)
 169 {
 170         p4d_t p4d = READ_ONCE(*p4dp);
 171
 172         if (mm_pud_folded(mm))
 173                 return;
 174
 175         p4d = __p4d(p4d_val(p4d) | RANDOM_ORVALUE);
 176         WRITE_ONCE(*p4dp, p4d);
 177         p4d_clear(p4dp);
 178         p4d = READ_ONCE(*p4dp);
 179         WARN_ON(!p4d_none(p4d));
 180 }
 181
 182 static void __init p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp,
 183                                       pud_t *pudp)
 184 {
 185         p4d_t p4d;
 186
 187         if (mm_pud_folded(mm))
 188                 return;
 189
 190         /*
 191          * This entry points to next level page table page.
 192          * Hence this must not qualify as p4d_bad().
 193          */
 194         pud_clear(pudp);
 195         p4d_clear(p4dp);
 196         p4d_populate(mm, p4dp, pudp);
 197         p4d = READ_ONCE(*p4dp);
 198         WARN_ON(p4d_bad(p4d));
 199 }
 200
 201 static void __init pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp)
 202 {
 203         pgd_t pgd = READ_ONCE(*pgdp);
 204
 205         if (mm_p4d_folded(mm))
 206                 return;
 207
 208         pgd = __pgd(pgd_val(pgd) | RANDOM_ORVALUE);
 209         WRITE_ONCE(*pgdp, pgd);
 210         pgd_clear(pgdp);
 211         pgd = READ_ONCE(*pgdp);
 212         WARN_ON(!pgd_none(pgd));
 213 }
 214
 215 static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
 216                                       p4d_t *p4dp)
 217 {
 218         pgd_t pgd;
 219
 220         if (mm_p4d_folded(mm))
 221                 return;
 222
 223         /*
 224          * This entry points to next level page table page.
 225          * Hence this must not qualify as pgd_bad().
 226          */
 227         p4d_clear(p4dp);
 228         pgd_clear(pgdp);
 229         pgd_populate(mm, pgdp, p4dp);
 230         pgd = READ_ONCE(*pgdp);
 231         WARN_ON(pgd_bad(pgd));
 232 }
 233 #else  /* !__PAGETABLE_P4D_FOLDED */
 234 static void __init p4d_clear_tests(struct mm_struct *mm, p4d_t *p4dp) { }
 235 static void __init pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp) { }
 236 static void __init p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp,
 237                                       pud_t *pudp)
 238 {
 239 }
 240 static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
 241                                       p4d_t *p4dp)
 242 {
 243 }
 244 #endif /* PAGETABLE_P4D_FOLDED */
 245
 246 static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,
 247                                    unsigned long vaddr)
 248 {
 249         pte_t pte = ptep_get(ptep);
 250
 251         pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
 252         set_pte_at(mm, vaddr, ptep, pte);
 253         barrier();
 254         pte_clear(mm, vaddr, ptep);
 255         pte = ptep_get(ptep);
 256         WARN_ON(!pte_none(pte));
 257 }
 258
 259 static void __init pmd_clear_tests(struct mm_struct *mm, pmd_t *pmdp)
 260 {
 261         pmd_t pmd = READ_ONCE(*pmdp);
 262
 263         pmd = __pmd(pmd_val(pmd) | RANDOM_ORVALUE);
 264         WRITE_ONCE(*pmdp, pmd);
 265         pmd_clear(pmdp);
 266         pmd = READ_ONCE(*pmdp);
 267         WARN_ON(!pmd_none(pmd));
 268 }
 269
 270 static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp,
 271                                       pgtable_t pgtable)
 272 {
 273         pmd_t pmd;
 274
 275         /*
 276          * This entry points to next level page table page.
 277          * Hence this must not qualify as pmd_bad().
 278          */
 279         pmd_clear(pmdp);
 280         pmd_populate(mm, pmdp, pgtable);
 281         pmd = READ_ONCE(*pmdp);
 282         WARN_ON(pmd_bad(pmd));
 283 }
 284
 285 static unsigned long __init get_random_vaddr(void)
 286 {
 287         unsigned long random_vaddr, random_pages, total_user_pages;
 288
 289         total_user_pages = (TASK_SIZE - FIRST_USER_ADDRESS) / PAGE_SIZE;
 290
 291         random_pages = get_random_long() % total_user_pages;
 292         random_vaddr = FIRST_USER_ADDRESS + random_pages * PAGE_SIZE;
 293
 294         return random_vaddr;
 295 }
 296
 297 static int __init debug_vm_pgtable(void)
 298 {
 299         struct mm_struct *mm;
 300         pgd_t *pgdp;
 301         p4d_t *p4dp, *saved_p4dp;
 302         pud_t *pudp, *saved_pudp;
 303         pmd_t *pmdp, *saved_pmdp, pmd;
 304         pte_t *ptep;
 305         pgtable_t saved_ptep;
 306         pgprot_t prot;
 307         phys_addr_t paddr;
 308         unsigned long vaddr, pte_aligned, pmd_aligned;
 309         unsigned long pud_aligned, p4d_aligned, pgd_aligned;
 310         spinlock_t *uninitialized_var(ptl);
 311
 312         pr_info("Validating architecture page table helpers\n");
 313         prot = vm_get_page_prot(VMFLAGS);
 314         vaddr = get_random_vaddr();
 315         mm = mm_alloc();
 316         if (!mm) {
 317                 pr_err("mm_struct allocation failed\n");
 318                 return 1;
 319         }
 320
 321         /*
 322          * PFN for mapping at PTE level is determined from a standard kernel
 323          * text symbol. But pfns for higher page table levels are derived by
 324          * masking lower bits of this real pfn. These derived pfns might not
 325          * exist on the platform but that does not really matter as pfn_pxx()
 326          * helpers will still create appropriate entries for the test. This
 327          * helps avoid large memory block allocations to be used for mapping
 328          * at higher page table levels.
 329          */
 330         paddr = __pa_symbol(&start_kernel);
 331
 332         pte_aligned = (paddr & PAGE_MASK) >> PAGE_SHIFT;
 333         pmd_aligned = (paddr & PMD_MASK) >> PAGE_SHIFT;
 334         pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT;
 335         p4d_aligned = (paddr & P4D_MASK) >> PAGE_SHIFT;
 336         pgd_aligned = (paddr & PGDIR_MASK) >> PAGE_SHIFT;
 337         WARN_ON(!pfn_valid(pte_aligned));
 338
 339         pgdp = pgd_offset(mm, vaddr);
 340         p4dp = p4d_alloc(mm, pgdp, vaddr);
 341         pudp = pud_alloc(mm, p4dp, vaddr);
 342         pmdp = pmd_alloc(mm, pudp, vaddr);
 343         ptep = pte_alloc_map_lock(mm, pmdp, vaddr, &ptl);
 344
 345         /*
 346          * Save all the page table page addresses as the page table
 347          * entries will be used for testing with random or garbage
 348          * values. These saved addresses will be used for freeing
 349          * page table pages.
 350          */
 351         pmd = READ_ONCE(*pmdp);
 352         saved_p4dp = p4d_offset(pgdp, 0UL);
 353         saved_pudp = pud_offset(p4dp, 0UL);
 354         saved_pmdp = pmd_offset(pudp, 0UL);
 355         saved_ptep = pmd_pgtable(pmd);
 356
 357         pte_basic_tests(pte_aligned, prot);
 358         pmd_basic_tests(pmd_aligned, prot);
 359         pud_basic_tests(pud_aligned, prot);
 360         p4d_basic_tests(p4d_aligned, prot);
 361         pgd_basic_tests(pgd_aligned, prot);
 362
 363         pte_clear_tests(mm, ptep, vaddr);
 364         pmd_clear_tests(mm, pmdp);
 365         pud_clear_tests(mm, pudp);
 366         p4d_clear_tests(mm, p4dp);
 367         pgd_clear_tests(mm, pgdp);
 368
 369         pte_unmap_unlock(ptep, ptl);
 370
 371         pmd_populate_tests(mm, pmdp, saved_ptep);
 372         pud_populate_tests(mm, pudp, saved_pmdp);
 373         p4d_populate_tests(mm, p4dp, saved_pudp);
 374         pgd_populate_tests(mm, pgdp, saved_p4dp);
 375
 376         p4d_free(mm, saved_p4dp);
 377         pud_free(mm, saved_pudp);
 378         pmd_free(mm, saved_pmdp);
 379         pte_free(mm, saved_ptep);
 380
 381         mm_dec_nr_puds(mm);
 382         mm_dec_nr_pmds(mm);
 383         mm_dec_nr_ptes(mm);
 384         mmdrop(mm);
 385         return 0;
 386 }
 387 late_initcall(debug_vm_pgtable);