// SPDX-License-Identifier: GPL-2.0-only /* * This kernel test validates architecture page table helpers and * accessors and helps in verifying their continued compliance with * expected generic MM semantics. * * Copyright (C) 2019 ARM Ltd. * * Author: Anshuman Khandual */ #define pr_fmt(fmt) "debug_vm_pgtable: [%-25s]: " fmt, __func__ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Please refer Documentation/mm/arch_pgtable_helpers.rst for the semantics * expectations that are being validated here. All future changes in here * or the documentation need to be in sync. * * On s390 platform, the lower 4 bits are used to identify given page table * entry type. But these bits might affect the ability to clear entries with * pxx_clear() because of how dynamic page table folding works on s390. So * while loading up the entries do not change the lower 4 bits. It does not * have affect any other platform. Also avoid the 62nd bit on ppc64 that is * used to mark a pte entry. */ #define S390_SKIP_MASK GENMASK(3, 0) #if __BITS_PER_LONG == 64 #define PPC64_SKIP_MASK GENMASK(62, 62) #else #define PPC64_SKIP_MASK 0x0 #endif #define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK) #define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK) #define RANDOM_NZVALUE GENMASK(7, 0) struct pgtable_debug_args { struct mm_struct *mm; struct vm_area_struct *vma; pgd_t *pgdp; p4d_t *p4dp; pud_t *pudp; pmd_t *pmdp; pte_t *ptep; p4d_t *start_p4dp; pud_t *start_pudp; pmd_t *start_pmdp; pgtable_t start_ptep; unsigned long vaddr; pgprot_t page_prot; pgprot_t page_prot_none; bool is_contiguous_page; unsigned long pud_pfn; unsigned long pmd_pfn; unsigned long pte_pfn; unsigned long fixed_alignment; unsigned long fixed_pgd_pfn; unsigned long fixed_p4d_pfn; unsigned long fixed_pud_pfn; unsigned long fixed_pmd_pfn; unsigned long fixed_pte_pfn; }; static void __init pte_basic_tests(struct pgtable_debug_args *args, int idx) { pgprot_t prot = vm_get_page_prot(idx); pte_t pte = pfn_pte(args->fixed_pte_pfn, prot); unsigned long val = idx, *ptr = &val; pr_debug("Validating PTE basic (%pGv)\n", ptr); /* * This test needs to be executed after the given page table entry * is created with pfn_pte() to make sure that vm_get_page_prot(idx) * does not have the dirty bit enabled from the beginning. This is * important for platforms like arm64 where (!PTE_RDONLY) indicate * dirty bit being set. */ WARN_ON(pte_dirty(pte_wrprotect(pte))); WARN_ON(!pte_same(pte, pte)); WARN_ON(!pte_young(pte_mkyoung(pte_mkold(pte)))); WARN_ON(!pte_dirty(pte_mkdirty(pte_mkclean(pte)))); WARN_ON(!pte_write(pte_mkwrite(pte_wrprotect(pte)))); WARN_ON(pte_young(pte_mkold(pte_mkyoung(pte)))); WARN_ON(pte_dirty(pte_mkclean(pte_mkdirty(pte)))); WARN_ON(pte_write(pte_wrprotect(pte_mkwrite(pte)))); WARN_ON(pte_dirty(pte_wrprotect(pte_mkclean(pte)))); WARN_ON(!pte_dirty(pte_wrprotect(pte_mkdirty(pte)))); } static void __init pte_advanced_tests(struct pgtable_debug_args *args) { struct page *page; pte_t pte; /* * Architectures optimize set_pte_at by avoiding TLB flush. * This requires set_pte_at to be not used to update an * existing pte entry. Clear pte before we do set_pte_at * * flush_dcache_page() is called after set_pte_at() to clear * PG_arch_1 for the page on ARM64. The page flag isn't cleared * when it's released and page allocation check will fail when * the page is allocated again. For architectures other than ARM64, * the unexpected overhead of cache flushing is acceptable. */ page = (args->pte_pfn != ULONG_MAX) ? pfn_to_page(args->pte_pfn) : NULL; if (!page) return; pr_debug("Validating PTE advanced\n"); if (WARN_ON(!args->ptep)) return; pte = pfn_pte(args->pte_pfn, args->page_prot); set_pte_at(args->mm, args->vaddr, args->ptep, pte); flush_dcache_page(page); ptep_set_wrprotect(args->mm, args->vaddr, args->ptep); pte = ptep_get(args->ptep); WARN_ON(pte_write(pte)); ptep_get_and_clear(args->mm, args->vaddr, args->ptep); pte = ptep_get(args->ptep); WARN_ON(!pte_none(pte)); pte = pfn_pte(args->pte_pfn, args->page_prot); pte = pte_wrprotect(pte); pte = pte_mkclean(pte); set_pte_at(args->mm, args->vaddr, args->ptep, pte); flush_dcache_page(page); pte = pte_mkwrite(pte); pte = pte_mkdirty(pte); ptep_set_access_flags(args->vma, args->vaddr, args->ptep, pte, 1); pte = ptep_get(args->ptep); WARN_ON(!(pte_write(pte) && pte_dirty(pte))); ptep_get_and_clear_full(args->mm, args->vaddr, args->ptep, 1); pte = ptep_get(args->ptep); WARN_ON(!pte_none(pte)); pte = pfn_pte(args->pte_pfn, args->page_prot); pte = pte_mkyoung(pte); set_pte_at(args->mm, args->vaddr, args->ptep, pte); flush_dcache_page(page); ptep_test_and_clear_young(args->vma, args->vaddr, args->ptep); pte = ptep_get(args->ptep); WARN_ON(pte_young(pte)); ptep_get_and_clear_full(args->mm, args->vaddr, args->ptep, 1); } #ifdef CONFIG_TRANSPARENT_HUGEPAGE static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx) { pgprot_t prot = vm_get_page_prot(idx); unsigned long val = idx, *ptr = &val; pmd_t pmd; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD basic (%pGv)\n", ptr); pmd = pfn_pmd(args->fixed_pmd_pfn, prot); /* * This test needs to be executed after the given page table entry * is created with pfn_pmd() to make sure that vm_get_page_prot(idx) * does not have the dirty bit enabled from the beginning. This is * important for platforms like arm64 where (!PTE_RDONLY) indicate * dirty bit being set. */ WARN_ON(pmd_dirty(pmd_wrprotect(pmd))); WARN_ON(!pmd_same(pmd, pmd)); WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd)))); WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd)))); WARN_ON(!pmd_write(pmd_mkwrite(pmd_wrprotect(pmd)))); WARN_ON(pmd_young(pmd_mkold(pmd_mkyoung(pmd)))); WARN_ON(pmd_dirty(pmd_mkclean(pmd_mkdirty(pmd)))); WARN_ON(pmd_write(pmd_wrprotect(pmd_mkwrite(pmd)))); WARN_ON(pmd_dirty(pmd_wrprotect(pmd_mkclean(pmd)))); WARN_ON(!pmd_dirty(pmd_wrprotect(pmd_mkdirty(pmd)))); /* * A huge page does not point to next level page table * entry. Hence this must qualify as pmd_bad(). */ WARN_ON(!pmd_bad(pmd_mkhuge(pmd))); } static void __init pmd_advanced_tests(struct pgtable_debug_args *args) { struct page *page; pmd_t pmd; unsigned long vaddr = args->vaddr; if (!has_transparent_hugepage()) return; page = (args->pmd_pfn != ULONG_MAX) ? pfn_to_page(args->pmd_pfn) : NULL; if (!page) return; /* * flush_dcache_page() is called after set_pmd_at() to clear * PG_arch_1 for the page on ARM64. The page flag isn't cleared * when it's released and page allocation check will fail when * the page is allocated again. For architectures other than ARM64, * the unexpected overhead of cache flushing is acceptable. */ pr_debug("Validating PMD advanced\n"); /* Align the address wrt HPAGE_PMD_SIZE */ vaddr &= HPAGE_PMD_MASK; pgtable_trans_huge_deposit(args->mm, args->pmdp, args->start_ptep); pmd = pfn_pmd(args->pmd_pfn, args->page_prot); set_pmd_at(args->mm, vaddr, args->pmdp, pmd); flush_dcache_page(page); pmdp_set_wrprotect(args->mm, vaddr, args->pmdp); pmd = READ_ONCE(*args->pmdp); WARN_ON(pmd_write(pmd)); pmdp_huge_get_and_clear(args->mm, vaddr, args->pmdp); pmd = READ_ONCE(*args->pmdp); WARN_ON(!pmd_none(pmd)); pmd = pfn_pmd(args->pmd_pfn, args->page_prot); pmd = pmd_wrprotect(pmd); pmd = pmd_mkclean(pmd); set_pmd_at(args->mm, vaddr, args->pmdp, pmd); flush_dcache_page(page); pmd = pmd_mkwrite(pmd); pmd = pmd_mkdirty(pmd); pmdp_set_access_flags(args->vma, vaddr, args->pmdp, pmd, 1); pmd = READ_ONCE(*args->pmdp); WARN_ON(!(pmd_write(pmd) && pmd_dirty(pmd))); pmdp_huge_get_and_clear_full(args->vma, vaddr, args->pmdp, 1); pmd = READ_ONCE(*args->pmdp); WARN_ON(!pmd_none(pmd)); pmd = pmd_mkhuge(pfn_pmd(args->pmd_pfn, args->page_prot)); pmd = pmd_mkyoung(pmd); set_pmd_at(args->mm, vaddr, args->pmdp, pmd); flush_dcache_page(page); pmdp_test_and_clear_young(args->vma, vaddr, args->pmdp); pmd = READ_ONCE(*args->pmdp); WARN_ON(pmd_young(pmd)); /* Clear the pte entries */ pmdp_huge_get_and_clear(args->mm, vaddr, args->pmdp); pgtable_trans_huge_withdraw(args->mm, args->pmdp); } static void __init pmd_leaf_tests(struct pgtable_debug_args *args) { pmd_t pmd; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD leaf\n"); pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot); /* * PMD based THP is a leaf entry. */ pmd = pmd_mkhuge(pmd); WARN_ON(!pmd_leaf(pmd)); } #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { pgprot_t prot = vm_get_page_prot(idx); unsigned long val = idx, *ptr = &val; pud_t pud; if (!has_transparent_hugepage()) return; pr_debug("Validating PUD basic (%pGv)\n", ptr); pud = pfn_pud(args->fixed_pud_pfn, prot); /* * This test needs to be executed after the given page table entry * is created with pfn_pud() to make sure that vm_get_page_prot(idx) * does not have the dirty bit enabled from the beginning. This is * important for platforms like arm64 where (!PTE_RDONLY) indicate * dirty bit being set. */ WARN_ON(pud_dirty(pud_wrprotect(pud))); WARN_ON(!pud_same(pud, pud)); WARN_ON(!pud_young(pud_mkyoung(pud_mkold(pud)))); WARN_ON(!pud_dirty(pud_mkdirty(pud_mkclean(pud)))); WARN_ON(pud_dirty(pud_mkclean(pud_mkdirty(pud)))); WARN_ON(!pud_write(pud_mkwrite(pud_wrprotect(pud)))); WARN_ON(pud_write(pud_wrprotect(pud_mkwrite(pud)))); WARN_ON(pud_young(pud_mkold(pud_mkyoung(pud)))); WARN_ON(pud_dirty(pud_wrprotect(pud_mkclean(pud)))); WARN_ON(!pud_dirty(pud_wrprotect(pud_mkdirty(pud)))); if (mm_pmd_folded(args->mm)) return; /* * A huge page does not point to next level page table * entry. Hence this must qualify as pud_bad(). */ WARN_ON(!pud_bad(pud_mkhuge(pud))); } static void __init pud_advanced_tests(struct pgtable_debug_args *args) { struct page *page; unsigned long vaddr = args->vaddr; pud_t pud; if (!has_transparent_hugepage()) return; page = (args->pud_pfn != ULONG_MAX) ? pfn_to_page(args->pud_pfn) : NULL; if (!page) return; /* * flush_dcache_page() is called after set_pud_at() to clear * PG_arch_1 for the page on ARM64. The page flag isn't cleared * when it's released and page allocation check will fail when * the page is allocated again. For architectures other than ARM64, * the unexpected overhead of cache flushing is acceptable. */ pr_debug("Validating PUD advanced\n"); /* Align the address wrt HPAGE_PUD_SIZE */ vaddr &= HPAGE_PUD_MASK; pud = pfn_pud(args->pud_pfn, args->page_prot); set_pud_at(args->mm, vaddr, args->pudp, pud); flush_dcache_page(page); pudp_set_wrprotect(args->mm, vaddr, args->pudp); pud = READ_ONCE(*args->pudp); WARN_ON(pud_write(pud)); #ifndef __PAGETABLE_PMD_FOLDED pudp_huge_get_and_clear(args->mm, vaddr, args->pudp); pud = READ_ONCE(*args->pudp); WARN_ON(!pud_none(pud)); #endif /* __PAGETABLE_PMD_FOLDED */ pud = pfn_pud(args->pud_pfn, args->page_prot); pud = pud_wrprotect(pud); pud = pud_mkclean(pud); set_pud_at(args->mm, vaddr, args->pudp, pud); flush_dcache_page(page); pud = pud_mkwrite(pud); pud = pud_mkdirty(pud); pudp_set_access_flags(args->vma, vaddr, args->pudp, pud, 1); pud = READ_ONCE(*args->pudp); WARN_ON(!(pud_write(pud) && pud_dirty(pud))); #ifndef __PAGETABLE_PMD_FOLDED pudp_huge_get_and_clear_full(args->mm, vaddr, args->pudp, 1); pud = READ_ONCE(*args->pudp); WARN_ON(!pud_none(pud)); #endif /* __PAGETABLE_PMD_FOLDED */ pud = pfn_pud(args->pud_pfn, args->page_prot); pud = pud_mkyoung(pud); set_pud_at(args->mm, vaddr, args->pudp, pud); flush_dcache_page(page); pudp_test_and_clear_young(args->vma, vaddr, args->pudp); pud = READ_ONCE(*args->pudp); WARN_ON(pud_young(pud)); pudp_huge_get_and_clear(args->mm, vaddr, args->pudp); } static void __init pud_leaf_tests(struct pgtable_debug_args *args) { pud_t pud; if (!has_transparent_hugepage()) return; pr_debug("Validating PUD leaf\n"); pud = pfn_pud(args->fixed_pud_pfn, args->page_prot); /* * PUD based THP is a leaf entry. */ pud = pud_mkhuge(pud); WARN_ON(!pud_leaf(pud)); } #else /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { } static void __init pud_advanced_tests(struct pgtable_debug_args *args) { } static void __init pud_leaf_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx) { } static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { } static void __init pmd_advanced_tests(struct pgtable_debug_args *args) { } static void __init pud_advanced_tests(struct pgtable_debug_args *args) { } static void __init pmd_leaf_tests(struct pgtable_debug_args *args) { } static void __init pud_leaf_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP static void __init pmd_huge_tests(struct pgtable_debug_args *args) { pmd_t pmd; if (!arch_vmap_pmd_supported(args->page_prot) || args->fixed_alignment < PMD_SIZE) return; pr_debug("Validating PMD huge\n"); /* * X86 defined pmd_set_huge() verifies that the given * PMD is not a populated non-leaf entry. */ WRITE_ONCE(*args->pmdp, __pmd(0)); WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot)); WARN_ON(!pmd_clear_huge(args->pmdp)); pmd = READ_ONCE(*args->pmdp); WARN_ON(!pmd_none(pmd)); } static void __init pud_huge_tests(struct pgtable_debug_args *args) { pud_t pud; if (!arch_vmap_pud_supported(args->page_prot) || args->fixed_alignment < PUD_SIZE) return; pr_debug("Validating PUD huge\n"); /* * X86 defined pud_set_huge() verifies that the given * PUD is not a populated non-leaf entry. */ WRITE_ONCE(*args->pudp, __pud(0)); WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot)); WARN_ON(!pud_clear_huge(args->pudp)); pud = READ_ONCE(*args->pudp); WARN_ON(!pud_none(pud)); } #else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */ static void __init pmd_huge_tests(struct pgtable_debug_args *args) { } static void __init pud_huge_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */ static void __init p4d_basic_tests(struct pgtable_debug_args *args) { p4d_t p4d; pr_debug("Validating P4D basic\n"); memset(&p4d, RANDOM_NZVALUE, sizeof(p4d_t)); WARN_ON(!p4d_same(p4d, p4d)); } static void __init pgd_basic_tests(struct pgtable_debug_args *args) { pgd_t pgd; pr_debug("Validating PGD basic\n"); memset(&pgd, RANDOM_NZVALUE, sizeof(pgd_t)); WARN_ON(!pgd_same(pgd, pgd)); } #ifndef __PAGETABLE_PUD_FOLDED static void __init pud_clear_tests(struct pgtable_debug_args *args) { pud_t pud = READ_ONCE(*args->pudp); if (mm_pmd_folded(args->mm)) return; pr_debug("Validating PUD clear\n"); pud = __pud(pud_val(pud) | RANDOM_ORVALUE); WRITE_ONCE(*args->pudp, pud); pud_clear(args->pudp); pud = READ_ONCE(*args->pudp); WARN_ON(!pud_none(pud)); } static void __init pud_populate_tests(struct pgtable_debug_args *args) { pud_t pud; if (mm_pmd_folded(args->mm)) return; pr_debug("Validating PUD populate\n"); /* * This entry points to next level page table page. * Hence this must not qualify as pud_bad(). */ pud_populate(args->mm, args->pudp, args->start_pmdp); pud = READ_ONCE(*args->pudp); WARN_ON(pud_bad(pud)); } #else /* !__PAGETABLE_PUD_FOLDED */ static void __init pud_clear_tests(struct pgtable_debug_args *args) { } static void __init pud_populate_tests(struct pgtable_debug_args *args) { } #endif /* PAGETABLE_PUD_FOLDED */ #ifndef __PAGETABLE_P4D_FOLDED static void __init p4d_clear_tests(struct pgtable_debug_args *args) { p4d_t p4d = READ_ONCE(*args->p4dp); if (mm_pud_folded(args->mm)) return; pr_debug("Validating P4D clear\n"); p4d = __p4d(p4d_val(p4d) | RANDOM_ORVALUE); WRITE_ONCE(*args->p4dp, p4d); p4d_clear(args->p4dp); p4d = READ_ONCE(*args->p4dp); WARN_ON(!p4d_none(p4d)); } static void __init p4d_populate_tests(struct pgtable_debug_args *args) { p4d_t p4d; if (mm_pud_folded(args->mm)) return; pr_debug("Validating P4D populate\n"); /* * This entry points to next level page table page. * Hence this must not qualify as p4d_bad(). */ pud_clear(args->pudp); p4d_clear(args->p4dp); p4d_populate(args->mm, args->p4dp, args->start_pudp); p4d = READ_ONCE(*args->p4dp); WARN_ON(p4d_bad(p4d)); } static void __init pgd_clear_tests(struct pgtable_debug_args *args) { pgd_t pgd = READ_ONCE(*(args->pgdp)); if (mm_p4d_folded(args->mm)) return; pr_debug("Validating PGD clear\n"); pgd = __pgd(pgd_val(pgd) | RANDOM_ORVALUE); WRITE_ONCE(*args->pgdp, pgd); pgd_clear(args->pgdp); pgd = READ_ONCE(*args->pgdp); WARN_ON(!pgd_none(pgd)); } static void __init pgd_populate_tests(struct pgtable_debug_args *args) { pgd_t pgd; if (mm_p4d_folded(args->mm)) return; pr_debug("Validating PGD populate\n"); /* * This entry points to next level page table page. * Hence this must not qualify as pgd_bad(). */ p4d_clear(args->p4dp); pgd_clear(args->pgdp); pgd_populate(args->mm, args->pgdp, args->start_p4dp); pgd = READ_ONCE(*args->pgdp); WARN_ON(pgd_bad(pgd)); } #else /* !__PAGETABLE_P4D_FOLDED */ static void __init p4d_clear_tests(struct pgtable_debug_args *args) { } static void __init pgd_clear_tests(struct pgtable_debug_args *args) { } static void __init p4d_populate_tests(struct pgtable_debug_args *args) { } static void __init pgd_populate_tests(struct pgtable_debug_args *args) { } #endif /* PAGETABLE_P4D_FOLDED */ static void __init pte_clear_tests(struct pgtable_debug_args *args) { struct page *page; pte_t pte = pfn_pte(args->pte_pfn, args->page_prot); page = (args->pte_pfn != ULONG_MAX) ? pfn_to_page(args->pte_pfn) : NULL; if (!page) return; /* * flush_dcache_page() is called after set_pte_at() to clear * PG_arch_1 for the page on ARM64. The page flag isn't cleared * when it's released and page allocation check will fail when * the page is allocated again. For architectures other than ARM64, * the unexpected overhead of cache flushing is acceptable. */ pr_debug("Validating PTE clear\n"); if (WARN_ON(!args->ptep)) return; #ifndef CONFIG_RISCV pte = __pte(pte_val(pte) | RANDOM_ORVALUE); #endif set_pte_at(args->mm, args->vaddr, args->ptep, pte); flush_dcache_page(page); barrier(); ptep_clear(args->mm, args->vaddr, args->ptep); pte = ptep_get(args->ptep); WARN_ON(!pte_none(pte)); } static void __init pmd_clear_tests(struct pgtable_debug_args *args) { pmd_t pmd = READ_ONCE(*args->pmdp); pr_debug("Validating PMD clear\n"); pmd = __pmd(pmd_val(pmd) | RANDOM_ORVALUE); WRITE_ONCE(*args->pmdp, pmd); pmd_clear(args->pmdp); pmd = READ_ONCE(*args->pmdp); WARN_ON(!pmd_none(pmd)); } static void __init pmd_populate_tests(struct pgtable_debug_args *args) { pmd_t pmd; pr_debug("Validating PMD populate\n"); /* * This entry points to next level page table page. * Hence this must not qualify as pmd_bad(). */ pmd_populate(args->mm, args->pmdp, args->start_ptep); pmd = READ_ONCE(*args->pmdp); WARN_ON(pmd_bad(pmd)); } static void __init pte_special_tests(struct pgtable_debug_args *args) { pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot); if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) return; pr_debug("Validating PTE special\n"); WARN_ON(!pte_special(pte_mkspecial(pte))); } static void __init pte_protnone_tests(struct pgtable_debug_args *args) { pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot_none); if (!IS_ENABLED(CONFIG_NUMA_BALANCING)) return; pr_debug("Validating PTE protnone\n"); WARN_ON(!pte_protnone(pte)); WARN_ON(!pte_present(pte)); } #ifdef CONFIG_TRANSPARENT_HUGEPAGE static void __init pmd_protnone_tests(struct pgtable_debug_args *args) { pmd_t pmd; if (!IS_ENABLED(CONFIG_NUMA_BALANCING)) return; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD protnone\n"); pmd = pmd_mkhuge(pfn_pmd(args->fixed_pmd_pfn, args->page_prot_none)); WARN_ON(!pmd_protnone(pmd)); WARN_ON(!pmd_present(pmd)); } #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ static void __init pmd_protnone_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #ifdef CONFIG_ARCH_HAS_PTE_DEVMAP static void __init pte_devmap_tests(struct pgtable_debug_args *args) { pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot); pr_debug("Validating PTE devmap\n"); WARN_ON(!pte_devmap(pte_mkdevmap(pte))); } #ifdef CONFIG_TRANSPARENT_HUGEPAGE static void __init pmd_devmap_tests(struct pgtable_debug_args *args) { pmd_t pmd; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD devmap\n"); pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot); WARN_ON(!pmd_devmap(pmd_mkdevmap(pmd))); } #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD static void __init pud_devmap_tests(struct pgtable_debug_args *args) { pud_t pud; if (!has_transparent_hugepage()) return; pr_debug("Validating PUD devmap\n"); pud = pfn_pud(args->fixed_pud_pfn, args->page_prot); WARN_ON(!pud_devmap(pud_mkdevmap(pud))); } #else /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ static void __init pud_devmap_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ #else /* CONFIG_TRANSPARENT_HUGEPAGE */ static void __init pmd_devmap_tests(struct pgtable_debug_args *args) { } static void __init pud_devmap_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #else static void __init pte_devmap_tests(struct pgtable_debug_args *args) { } static void __init pmd_devmap_tests(struct pgtable_debug_args *args) { } static void __init pud_devmap_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_ARCH_HAS_PTE_DEVMAP */ static void __init pte_soft_dirty_tests(struct pgtable_debug_args *args) { pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot); if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) return; pr_debug("Validating PTE soft dirty\n"); WARN_ON(!pte_soft_dirty(pte_mksoft_dirty(pte))); WARN_ON(pte_soft_dirty(pte_clear_soft_dirty(pte))); } static void __init pte_swap_soft_dirty_tests(struct pgtable_debug_args *args) { pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot); if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) return; pr_debug("Validating PTE swap soft dirty\n"); WARN_ON(!pte_swp_soft_dirty(pte_swp_mksoft_dirty(pte))); WARN_ON(pte_swp_soft_dirty(pte_swp_clear_soft_dirty(pte))); } #ifdef CONFIG_TRANSPARENT_HUGEPAGE static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args) { pmd_t pmd; if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) return; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD soft dirty\n"); pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot); WARN_ON(!pmd_soft_dirty(pmd_mksoft_dirty(pmd))); WARN_ON(pmd_soft_dirty(pmd_clear_soft_dirty(pmd))); } static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) { pmd_t pmd; if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) || !IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION)) return; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD swap soft dirty\n"); pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot); WARN_ON(!pmd_swp_soft_dirty(pmd_swp_mksoft_dirty(pmd))); WARN_ON(pmd_swp_soft_dirty(pmd_swp_clear_soft_dirty(pmd))); } #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args) { } static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args) { unsigned long max_swap_offset; swp_entry_t entry, entry2; pte_t pte; pr_debug("Validating PTE swap exclusive\n"); /* See generic_max_swapfile_size(): probe the maximum offset */ max_swap_offset = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0, ~0UL)))); /* Create a swp entry with all possible bits set */ entry = swp_entry((1 << MAX_SWAPFILES_SHIFT) - 1, max_swap_offset); pte = swp_entry_to_pte(entry); WARN_ON(pte_swp_exclusive(pte)); WARN_ON(!is_swap_pte(pte)); entry2 = pte_to_swp_entry(pte); WARN_ON(memcmp(&entry, &entry2, sizeof(entry))); pte = pte_swp_mkexclusive(pte); WARN_ON(!pte_swp_exclusive(pte)); WARN_ON(!is_swap_pte(pte)); WARN_ON(pte_swp_soft_dirty(pte)); entry2 = pte_to_swp_entry(pte); WARN_ON(memcmp(&entry, &entry2, sizeof(entry))); pte = pte_swp_clear_exclusive(pte); WARN_ON(pte_swp_exclusive(pte)); WARN_ON(!is_swap_pte(pte)); entry2 = pte_to_swp_entry(pte); WARN_ON(memcmp(&entry, &entry2, sizeof(entry))); } static void __init pte_swap_tests(struct pgtable_debug_args *args) { swp_entry_t swp; pte_t pte; pr_debug("Validating PTE swap\n"); pte = pfn_pte(args->fixed_pte_pfn, args->page_prot); swp = __pte_to_swp_entry(pte); pte = __swp_entry_to_pte(swp); WARN_ON(args->fixed_pte_pfn != pte_pfn(pte)); } #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION static void __init pmd_swap_tests(struct pgtable_debug_args *args) { swp_entry_t swp; pmd_t pmd; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD swap\n"); pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot); swp = __pmd_to_swp_entry(pmd); pmd = __swp_entry_to_pmd(swp); WARN_ON(args->fixed_pmd_pfn != pmd_pfn(pmd)); } #else /* !CONFIG_ARCH_ENABLE_THP_MIGRATION */ static void __init pmd_swap_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */ static void __init swap_migration_tests(struct pgtable_debug_args *args) { struct page *page; swp_entry_t swp; if (!IS_ENABLED(CONFIG_MIGRATION)) return; /* * swap_migration_tests() requires a dedicated page as it needs to * be locked before creating a migration entry from it. Locking the * page that actually maps kernel text ('start_kernel') can be real * problematic. Lets use the allocated page explicitly for this * purpose. */ page = (args->pte_pfn != ULONG_MAX) ? pfn_to_page(args->pte_pfn) : NULL; if (!page) return; pr_debug("Validating swap migration\n"); /* * make_[readable|writable]_migration_entry() expects given page to * be locked, otherwise it stumbles upon a BUG_ON(). */ __SetPageLocked(page); swp = make_writable_migration_entry(page_to_pfn(page)); WARN_ON(!is_migration_entry(swp)); WARN_ON(!is_writable_migration_entry(swp)); swp = make_readable_migration_entry(swp_offset(swp)); WARN_ON(!is_migration_entry(swp)); WARN_ON(is_writable_migration_entry(swp)); swp = make_readable_migration_entry(page_to_pfn(page)); WARN_ON(!is_migration_entry(swp)); WARN_ON(is_writable_migration_entry(swp)); __ClearPageLocked(page); } #ifdef CONFIG_HUGETLB_PAGE static void __init hugetlb_basic_tests(struct pgtable_debug_args *args) { struct page *page; pte_t pte; pr_debug("Validating HugeTLB basic\n"); /* * Accessing the page associated with the pfn is safe here, * as it was previously derived from a real kernel symbol. */ page = pfn_to_page(args->fixed_pmd_pfn); pte = mk_huge_pte(page, args->page_prot); WARN_ON(!huge_pte_dirty(huge_pte_mkdirty(pte))); WARN_ON(!huge_pte_write(huge_pte_mkwrite(huge_pte_wrprotect(pte)))); WARN_ON(huge_pte_write(huge_pte_wrprotect(huge_pte_mkwrite(pte)))); #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB pte = pfn_pte(args->fixed_pmd_pfn, args->page_prot); WARN_ON(!pte_huge(arch_make_huge_pte(pte, PMD_SHIFT, VM_ACCESS_FLAGS))); #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */ } #else /* !CONFIG_HUGETLB_PAGE */ static void __init hugetlb_basic_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_HUGETLB_PAGE */ #ifdef CONFIG_TRANSPARENT_HUGEPAGE static void __init pmd_thp_tests(struct pgtable_debug_args *args) { pmd_t pmd; if (!has_transparent_hugepage()) return; pr_debug("Validating PMD based THP\n"); /* * pmd_trans_huge() and pmd_present() must return positive after * MMU invalidation with pmd_mkinvalid(). This behavior is an * optimization for transparent huge page. pmd_trans_huge() must * be true if pmd_page() returns a valid THP to avoid taking the * pmd_lock when others walk over non transhuge pmds (i.e. there * are no THP allocated). Especially when splitting a THP and * removing the present bit from the pmd, pmd_trans_huge() still * needs to return true. pmd_present() should be true whenever * pmd_trans_huge() returns true. */ pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot); WARN_ON(!pmd_trans_huge(pmd_mkhuge(pmd))); #ifndef __HAVE_ARCH_PMDP_INVALIDATE WARN_ON(!pmd_trans_huge(pmd_mkinvalid(pmd_mkhuge(pmd)))); WARN_ON(!pmd_present(pmd_mkinvalid(pmd_mkhuge(pmd)))); #endif /* __HAVE_ARCH_PMDP_INVALIDATE */ } #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD static void __init pud_thp_tests(struct pgtable_debug_args *args) { pud_t pud; if (!has_transparent_hugepage()) return; pr_debug("Validating PUD based THP\n"); pud = pfn_pud(args->fixed_pud_pfn, args->page_prot); WARN_ON(!pud_trans_huge(pud_mkhuge(pud))); /* * pud_mkinvalid() has been dropped for now. Enable back * these tests when it comes back with a modified pud_present(). * * WARN_ON(!pud_trans_huge(pud_mkinvalid(pud_mkhuge(pud)))); * WARN_ON(!pud_present(pud_mkinvalid(pud_mkhuge(pud)))); */ } #else /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ static void __init pud_thp_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ static void __init pmd_thp_tests(struct pgtable_debug_args *args) { } static void __init pud_thp_tests(struct pgtable_debug_args *args) { } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ static unsigned long __init get_random_vaddr(void) { unsigned long random_vaddr, random_pages, total_user_pages; total_user_pages = (TASK_SIZE - FIRST_USER_ADDRESS) / PAGE_SIZE; random_pages = get_random_long() % total_user_pages; random_vaddr = FIRST_USER_ADDRESS + random_pages * PAGE_SIZE; return random_vaddr; } static void __init destroy_args(struct pgtable_debug_args *args) { struct page *page = NULL; /* Free (huge) page */ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) && has_transparent_hugepage() && args->pud_pfn != ULONG_MAX) { if (args->is_contiguous_page) { free_contig_range(args->pud_pfn, (1 << (HPAGE_PUD_SHIFT - PAGE_SHIFT))); } else { page = pfn_to_page(args->pud_pfn); __free_pages(page, HPAGE_PUD_SHIFT - PAGE_SHIFT); } args->pud_pfn = ULONG_MAX; args->pmd_pfn = ULONG_MAX; args->pte_pfn = ULONG_MAX; } if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && has_transparent_hugepage() && args->pmd_pfn != ULONG_MAX) { if (args->is_contiguous_page) { free_contig_range(args->pmd_pfn, (1 << HPAGE_PMD_ORDER)); } else { page = pfn_to_page(args->pmd_pfn); __free_pages(page, HPAGE_PMD_ORDER); } args->pmd_pfn = ULONG_MAX; args->pte_pfn = ULONG_MAX; } if (args->pte_pfn != ULONG_MAX) { page = pfn_to_page(args->pte_pfn); __free_page(page); args->pte_pfn = ULONG_MAX; } /* Free page table entries */ if (args->start_ptep) { pte_free(args->mm, args->start_ptep); mm_dec_nr_ptes(args->mm); } if (args->start_pmdp) { pmd_free(args->mm, args->start_pmdp); mm_dec_nr_pmds(args->mm); } if (args->start_pudp) { pud_free(args->mm, args->start_pudp); mm_dec_nr_puds(args->mm); } if (args->start_p4dp) p4d_free(args->mm, args->start_p4dp); /* Free vma and mm struct */ if (args->vma) vm_area_free(args->vma); if (args->mm) mmdrop(args->mm); } static struct page * __init debug_vm_pgtable_alloc_huge_page(struct pgtable_debug_args *args, int order) { struct page *page = NULL; #ifdef CONFIG_CONTIG_ALLOC if (order > MAX_ORDER) { page = alloc_contig_pages((1 << order), GFP_KERNEL, first_online_node, NULL); if (page) { args->is_contiguous_page = true; return page; } } #endif if (order <= MAX_ORDER) page = alloc_pages(GFP_KERNEL, order); return page; } /* * Check if a physical memory range described by contains * an area that is of size psize, and aligned to psize. * * Don't use address 0, an all-zeroes physical address might mask bugs, and * it's not used on x86. */ static void __init phys_align_check(phys_addr_t pstart, phys_addr_t pend, unsigned long psize, phys_addr_t *physp, unsigned long *alignp) { phys_addr_t aligned_start, aligned_end; if (pstart == 0) pstart = PAGE_SIZE; aligned_start = ALIGN(pstart, psize); aligned_end = aligned_start + psize; if (aligned_end > aligned_start && aligned_end <= pend) { *alignp = psize; *physp = aligned_start; } } static void __init init_fixed_pfns(struct pgtable_debug_args *args) { u64 idx; phys_addr_t phys, pstart, pend; /* * Initialize the fixed pfns. To do this, try to find a * valid physical range, preferably aligned to PUD_SIZE, * but settling for aligned to PMD_SIZE as a fallback. If * neither of those is found, use the physical address of * the start_kernel symbol. * * The memory doesn't need to be allocated, it just needs to exist * as usable memory. It won't be touched. * * The alignment is recorded, and can be checked to see if we * can run the tests that require an actual valid physical * address range on some architectures ({pmd,pud}_huge_test * on x86). */ phys = __pa_symbol(&start_kernel); args->fixed_alignment = PAGE_SIZE; for_each_mem_range(idx, &pstart, &pend) { /* First check for a PUD-aligned area */ phys_align_check(pstart, pend, PUD_SIZE, &phys, &args->fixed_alignment); /* If a PUD-aligned area is found, we're done */ if (args->fixed_alignment == PUD_SIZE) break; /* * If no PMD-aligned area found yet, check for one, * but continue the loop to look for a PUD-aligned area. */ if (args->fixed_alignment < PMD_SIZE) phys_align_check(pstart, pend, PMD_SIZE, &phys, &args->fixed_alignment); } args->fixed_pgd_pfn = __phys_to_pfn(phys & PGDIR_MASK); args->fixed_p4d_pfn = __phys_to_pfn(phys & P4D_MASK); args->fixed_pud_pfn = __phys_to_pfn(phys & PUD_MASK); args->fixed_pmd_pfn = __phys_to_pfn(phys & PMD_MASK); args->fixed_pte_pfn = __phys_to_pfn(phys & PAGE_MASK); WARN_ON(!pfn_valid(args->fixed_pte_pfn)); } static int __init init_args(struct pgtable_debug_args *args) { struct page *page = NULL; int ret = 0; /* * Initialize the debugging data. * * vm_get_page_prot(VM_NONE) or vm_get_page_prot(VM_SHARED|VM_NONE) * will help create page table entries with PROT_NONE permission as * required for pxx_protnone_tests(). */ memset(args, 0, sizeof(*args)); args->vaddr = get_random_vaddr(); args->page_prot = vm_get_page_prot(VM_ACCESS_FLAGS); args->page_prot_none = vm_get_page_prot(VM_NONE); args->is_contiguous_page = false; args->pud_pfn = ULONG_MAX; args->pmd_pfn = ULONG_MAX; args->pte_pfn = ULONG_MAX; args->fixed_pgd_pfn = ULONG_MAX; args->fixed_p4d_pfn = ULONG_MAX; args->fixed_pud_pfn = ULONG_MAX; args->fixed_pmd_pfn = ULONG_MAX; args->fixed_pte_pfn = ULONG_MAX; /* Allocate mm and vma */ args->mm = mm_alloc(); if (!args->mm) { pr_err("Failed to allocate mm struct\n"); ret = -ENOMEM; goto error; } args->vma = vm_area_alloc(args->mm); if (!args->vma) { pr_err("Failed to allocate vma\n"); ret = -ENOMEM; goto error; } /* * Allocate page table entries. They will be modified in the tests. * Lets save the page table entries so that they can be released * when the tests are completed. */ args->pgdp = pgd_offset(args->mm, args->vaddr); args->p4dp = p4d_alloc(args->mm, args->pgdp, args->vaddr); if (!args->p4dp) { pr_err("Failed to allocate p4d entries\n"); ret = -ENOMEM; goto error; } args->start_p4dp = p4d_offset(args->pgdp, 0UL); WARN_ON(!args->start_p4dp); args->pudp = pud_alloc(args->mm, args->p4dp, args->vaddr); if (!args->pudp) { pr_err("Failed to allocate pud entries\n"); ret = -ENOMEM; goto error; } args->start_pudp = pud_offset(args->p4dp, 0UL); WARN_ON(!args->start_pudp); args->pmdp = pmd_alloc(args->mm, args->pudp, args->vaddr); if (!args->pmdp) { pr_err("Failed to allocate pmd entries\n"); ret = -ENOMEM; goto error; } args->start_pmdp = pmd_offset(args->pudp, 0UL); WARN_ON(!args->start_pmdp); if (pte_alloc(args->mm, args->pmdp)) { pr_err("Failed to allocate pte entries\n"); ret = -ENOMEM; goto error; } args->start_ptep = pmd_pgtable(READ_ONCE(*args->pmdp)); WARN_ON(!args->start_ptep); init_fixed_pfns(args); /* * Allocate (huge) pages because some of the tests need to access * the data in the pages. The corresponding tests will be skipped * if we fail to allocate (huge) pages. */ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) && has_transparent_hugepage()) { page = debug_vm_pgtable_alloc_huge_page(args, HPAGE_PUD_SHIFT - PAGE_SHIFT); if (page) { args->pud_pfn = page_to_pfn(page); args->pmd_pfn = args->pud_pfn; args->pte_pfn = args->pud_pfn; return 0; } } if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && has_transparent_hugepage()) { page = debug_vm_pgtable_alloc_huge_page(args, HPAGE_PMD_ORDER); if (page) { args->pmd_pfn = page_to_pfn(page); args->pte_pfn = args->pmd_pfn; return 0; } } page = alloc_page(GFP_KERNEL); if (page) args->pte_pfn = page_to_pfn(page); return 0; error: destroy_args(args); return ret; } static int __init debug_vm_pgtable(void) { struct pgtable_debug_args args; spinlock_t *ptl = NULL; int idx, ret; pr_info("Validating architecture page table helpers\n"); ret = init_args(&args); if (ret) return ret; /* * Iterate over each possible vm_flags to make sure that all * the basic page table transformation validations just hold * true irrespective of the starting protection value for a * given page table entry. * * Protection based vm_flags combinatins are always linear * and increasing i.e starting from VM_NONE and going upto * (VM_SHARED | READ | WRITE | EXEC). */ #define VM_FLAGS_START (VM_NONE) #define VM_FLAGS_END (VM_SHARED | VM_EXEC | VM_WRITE | VM_READ) for (idx = VM_FLAGS_START; idx <= VM_FLAGS_END; idx++) { pte_basic_tests(&args, idx); pmd_basic_tests(&args, idx); pud_basic_tests(&args, idx); } /* * Both P4D and PGD level tests are very basic which do not * involve creating page table entries from the protection * value and the given pfn. Hence just keep them out from * the above iteration for now to save some test execution * time. */ p4d_basic_tests(&args); pgd_basic_tests(&args); pmd_leaf_tests(&args); pud_leaf_tests(&args); pte_special_tests(&args); pte_protnone_tests(&args); pmd_protnone_tests(&args); pte_devmap_tests(&args); pmd_devmap_tests(&args); pud_devmap_tests(&args); pte_soft_dirty_tests(&args); pmd_soft_dirty_tests(&args); pte_swap_soft_dirty_tests(&args); pmd_swap_soft_dirty_tests(&args); pte_swap_exclusive_tests(&args); pte_swap_tests(&args); pmd_swap_tests(&args); swap_migration_tests(&args); pmd_thp_tests(&args); pud_thp_tests(&args); hugetlb_basic_tests(&args); /* * Page table modifying tests. They need to hold * proper page table lock. */ args.ptep = pte_offset_map_lock(args.mm, args.pmdp, args.vaddr, &ptl); pte_clear_tests(&args); pte_advanced_tests(&args); if (args.ptep) pte_unmap_unlock(args.ptep, ptl); ptl = pmd_lock(args.mm, args.pmdp); pmd_clear_tests(&args); pmd_advanced_tests(&args); pmd_huge_tests(&args); pmd_populate_tests(&args); spin_unlock(ptl); ptl = pud_lock(args.mm, args.pudp); pud_clear_tests(&args); pud_advanced_tests(&args); pud_huge_tests(&args); pud_populate_tests(&args); spin_unlock(ptl); spin_lock(&(args.mm->page_table_lock)); p4d_clear_tests(&args); pgd_clear_tests(&args); p4d_populate_tests(&args); pgd_populate_tests(&args); spin_unlock(&(args.mm->page_table_lock)); destroy_args(&args); return 0; } late_initcall(debug_vm_pgtable);