Re: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture page table helpers

Christophe Leroy
2019-09-12T15:36:31Z

Le 12/09/2019 à 17:00, Christophe Leroy a écrit :
>
>
> On 09/12/2019 06:02 AM, Anshuman Khandual wrote:
>> This adds a test module which will validate architecture page table
>> helpers
>> and accessors regarding compliance with generic MM semantics
>> expectations.
>> This will help various architectures in validating changes to the
>> existing
>> page table helpers or addition of new ones.
>>
>> Test page table and memory pages creating it's entries at various
>> level are
>> all allocated from system memory with required alignments. If memory
>> pages
>> with required size and alignment could not be allocated, then all
>> depending
>> individual tests are skipped.
>
> Build failure on powerpc book3s/32. This is because asm/highmem.h is
> missing. It can't be included from asm/book3s/32/pgtable.h because it
> creates circular dependency. So it has to be included from
> mm/arch_pgtable_test.c

In fact it is <linux/highmem.h> that needs to be added, adding
<asm/highmem.h> directly provokes build failure at link time.

Christophe

>
>
>
>   CC      mm/arch_pgtable_test.o
> In file included from ./arch/powerpc/include/asm/book3s/pgtable.h:8:0,
>                  from ./arch/powerpc/include/asm/pgtable.h:18,
>                  from ./include/linux/mm.h:99,
>                  from ./arch/powerpc/include/asm/io.h:29,
>                  from ./include/linux/io.h:13,
>                  from ./include/linux/irq.h:20,
>                  from ./arch/powerpc/include/asm/hardirq.h:6,
>                  from ./include/linux/hardirq.h:9,
>                  from ./include/linux/interrupt.h:11,
>                  from ./include/linux/kernel_stat.h:9,
>                  from ./include/linux/cgroup.h:26,
>                  from ./include/linux/hugetlb.h:9,
>                  from mm/arch_pgtable_test.c:14:
> mm/arch_pgtable_test.c: In function 'arch_pgtable_tests_init':
> ./arch/powerpc/include/asm/book3s/32/pgtable.h:365:13: error: implicit
> declaration of function 'kmap_atomic'
> [-Werror=implicit-function-declaration]
>   ((pte_t *)(kmap_atomic(pmd_page(*(dir))) + \
>              ^
> ./include/linux/mm.h:2008:31: note: in expansion of macro 'pte_offset_map'
>   (pte_alloc(mm, pmd) ? NULL : pte_offset_map(pmd, address))
>                                ^
> mm/arch_pgtable_test.c:377:9: note: in expansion of macro 'pte_alloc_map'
>   ptep = pte_alloc_map(mm, pmdp, vaddr);
>          ^
> cc1: some warnings being treated as errors
> make[2]: *** [mm/arch_pgtable_test.o] Error 1
>
>
> Christophe
>
>
>>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
>> Cc: Jason Gunthorpe <jgg@ziepe.ca>
>> Cc: Dan Williams <dan.j.williams@intel.com>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Mark Brown <broonie@kernel.org>
>> Cc: Steven Price <Steven.Price@arm.com>
>> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Sri Krishna chowdary <schowdary@nvidia.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: Paul Mackerras <paulus@samba.org>
>> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
>> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
>> Cc: "David S. Miller" <davem@davemloft.net>
>> Cc: Vineet Gupta <vgupta@synopsys.com>
>> Cc: James Hogan <jhogan@kernel.org>
>> Cc: Paul Burton <paul.burton@mips.com>
>> Cc: Ralf Baechle <ralf@linux-mips.org>
>> Cc: Kirill A. Shutemov <kirill@shutemov.name>
>> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
>> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
>> Cc: linux-snps-arc@lists.infradead.org
>> Cc: linux-mips@vger.kernel.org
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: linux-ia64@vger.kernel.org
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Cc: linux-s390@vger.kernel.org
>> Cc: linux-sh@vger.kernel.org
>> Cc: sparclinux@vger.kernel.org
>> Cc: x86@kernel.org
>> Cc: linux-kernel@vger.kernel.org
>>
>> Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>>   arch/x86/include/asm/pgtable_64_types.h |   2 +
>>   mm/Kconfig.debug                        |  14 +
>>   mm/Makefile                             |   1 +
>>   mm/arch_pgtable_test.c                  | 429 ++++++++++++++++++++++++
>>   4 files changed, 446 insertions(+)
>>   create mode 100644 mm/arch_pgtable_test.c
>>
>> diff --git a/arch/x86/include/asm/pgtable_64_types.h
>> b/arch/x86/include/asm/pgtable_64_types.h
>> index 52e5f5f2240d..b882792a3999 100644
>> --- a/arch/x86/include/asm/pgtable_64_types.h
>> +++ b/arch/x86/include/asm/pgtable_64_types.h
>> @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void)
>>   #define pgtable_l5_enabled() 0
>>   #endif /* CONFIG_X86_5LEVEL */
>> +#define mm_p4d_folded(mm) (!pgtable_l5_enabled())
>> +
>>   extern unsigned int pgdir_shift;
>>   extern unsigned int ptrs_per_p4d;
>> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
>> index 327b3ebf23bf..ce9c397f7b07 100644
>> --- a/mm/Kconfig.debug
>> +++ b/mm/Kconfig.debug
>> @@ -117,3 +117,17 @@ config DEBUG_RODATA_TEST
>>       depends on STRICT_KERNEL_RWX
>>       ---help---
>>         This option enables a testcase for the setting rodata read-only.
>> +
>> +config DEBUG_ARCH_PGTABLE_TEST
>> +    bool "Test arch page table helpers for semantics compliance"
>> +    depends on MMU
>> +    depends on DEBUG_KERNEL
>> +    help
>> +      This options provides a kernel module which can be used to test
>> +      architecture page table helper functions on various platform in
>> +      verifying if they comply with expected generic MM semantics. This
>> +      will help architectures code in making sure that any changes or
>> +      new additions of these helpers will still conform to generic MM
>> +      expected semantics.
>> +
>> +      If unsure, say N.
>> diff --git a/mm/Makefile b/mm/Makefile
>> index d996846697ef..bb572c5aa8c5 100644
>> --- a/mm/Makefile
>> +++ b/mm/Makefile
>> @@ -86,6 +86,7 @@ obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
>>   obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
>>   obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
>>   obj-$(CONFIG_DEBUG_RODATA_TEST) += rodata_test.o
>> +obj-$(CONFIG_DEBUG_ARCH_PGTABLE_TEST) += arch_pgtable_test.o
>>   obj-$(CONFIG_PAGE_OWNER) += page_owner.o
>>   obj-$(CONFIG_CLEANCACHE) += cleancache.o
>>   obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
>> new file mode 100644
>> index 000000000000..8b4a92756ad8
>> --- /dev/null
>> +++ b/mm/arch_pgtable_test.c
>> @@ -0,0 +1,429 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * This kernel module validates architecture page table helpers &
>> + * accessors and helps in verifying their continued compliance with
>> + * generic MM semantics.
>> + *
>> + * Copyright (C) 2019 ARM Ltd.
>> + *
>> + * Author: Anshuman Khandual <anshuman.khandual@arm.com>
>> + */
>> +#define pr_fmt(fmt) "arch_pgtable_test: %s " fmt, __func__
>> +
>> +#include <linux/gfp.h>
>> +#include <linux/hugetlb.h>
>> +#include <linux/kernel.h>
>> +#include <linux/mm.h>
>> +#include <linux/mman.h>
>> +#include <linux/mm_types.h>
>> +#include <linux/module.h>
>> +#include <linux/pfn_t.h>
>> +#include <linux/printk.h>
>> +#include <linux/random.h>
>> +#include <linux/spinlock.h>
>> +#include <linux/swap.h>
>> +#include <linux/swapops.h>
>> +#include <linux/sched/mm.h>
>> +#include <asm/pgalloc.h>
>> +#include <asm/pgtable.h>
>> +
>> +/*
>> + * Basic operations
>> + *
>> + * mkold(entry)            = An old and not a young entry
>> + * mkyoung(entry)        = A young and not an old entry
>> + * mkdirty(entry)        = A dirty and not a clean entry
>> + * mkclean(entry)        = A clean and not a dirty entry
>> + * mkwrite(entry)        = A write and not a write protected entry
>> + * wrprotect(entry)        = A write protected and not a write entry
>> + * pxx_bad(entry)        = A mapped and non-table entry
>> + * pxx_same(entry1, entry2)    = Both entries hold the exact same value
>> + */
>> +#define VMFLAGS    (VM_READ|VM_WRITE|VM_EXEC)
>> +
>> +/*
>> + * On s390 platform, the lower 12 bits are used to identify given
>> page table
>> + * entry type and for other arch specific requirements. But these
>> bits might
>> + * affect the ability to clear entries with pxx_clear(). So while
>> loading up
>> + * the entries skip all lower 12 bits in order to accommodate s390
>> platform.
>> + * It does not have affect any other platform.
>> + */
>> +#define RANDOM_ORVALUE    (0xfffffffffffff000UL)
>> +#define RANDOM_NZVALUE    (0xff)
>> +
>> +static bool pud_aligned;
>> +static bool pmd_aligned;
>> +
>> +static void pte_basic_tests(struct page *page, pgprot_t prot)
>> +{
>> +    pte_t pte = mk_pte(page, prot);
>> +
>> +    WARN_ON(!pte_same(pte, pte));
>> +    WARN_ON(!pte_young(pte_mkyoung(pte)));
>> +    WARN_ON(!pte_dirty(pte_mkdirty(pte)));
>> +    WARN_ON(!pte_write(pte_mkwrite(pte)));
>> +    WARN_ON(pte_young(pte_mkold(pte)));
>> +    WARN_ON(pte_dirty(pte_mkclean(pte)));
>> +    WARN_ON(pte_write(pte_wrprotect(pte)));
>> +}
>> +
>> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE
>> +static void pmd_basic_tests(struct page *page, pgprot_t prot)
>> +{
>> +    pmd_t pmd;
>> +
>> +    /*
>> +     * Memory block here must be PMD_SIZE aligned. Abort this
>> +     * test in case we could not allocate such a memory block.
>> +     */
>> +    if (!pmd_aligned) {
>> +        pr_warn("Could not proceed with PMD tests\n");
>> +        return;
>> +    }
>> +
>> +    pmd = mk_pmd(page, prot);
>> +    WARN_ON(!pmd_same(pmd, pmd));
>> +    WARN_ON(!pmd_young(pmd_mkyoung(pmd)));
>> +    WARN_ON(!pmd_dirty(pmd_mkdirty(pmd)));
>> +    WARN_ON(!pmd_write(pmd_mkwrite(pmd)));
>> +    WARN_ON(pmd_young(pmd_mkold(pmd)));
>> +    WARN_ON(pmd_dirty(pmd_mkclean(pmd)));
>> +    WARN_ON(pmd_write(pmd_wrprotect(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)));
>> +}
>> +#else
>> +static void pmd_basic_tests(struct page *page, pgprot_t prot) { }
>> +#endif
>> +
>> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
>> +static void pud_basic_tests(struct page *page, pgprot_t prot)
>> +{
>> +    pud_t pud;
>> +
>> +    /*
>> +     * Memory block here must be PUD_SIZE aligned. Abort this
>> +     * test in case we could not allocate such a memory block.
>> +     */
>> +    if (!pud_aligned) {
>> +        pr_warn("Could not proceed with PUD tests\n");
>> +        return;
>> +    }
>> +
>> +    pud = pfn_pud(page_to_pfn(page), prot);
>> +    WARN_ON(!pud_same(pud, pud));
>> +    WARN_ON(!pud_young(pud_mkyoung(pud)));
>> +    WARN_ON(!pud_write(pud_mkwrite(pud)));
>> +    WARN_ON(pud_write(pud_wrprotect(pud)));
>> +    WARN_ON(pud_young(pud_mkold(pud)));
>> +
>> +#if !defined(__PAGETABLE_PMD_FOLDED) && !defined(__ARCH_HAS_4LEVEL_HACK)
>> +    /*
>> +     * 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)));
>> +#endif
>> +}
>> +#else
>> +static void pud_basic_tests(struct page *page, pgprot_t prot) { }
>> +#endif
>> +
>> +static void p4d_basic_tests(struct page *page, pgprot_t prot)
>> +{
>> +    p4d_t p4d;
>> +
>> +    memset(&p4d, RANDOM_NZVALUE, sizeof(p4d_t));
>> +    WARN_ON(!p4d_same(p4d, p4d));
>> +}
>> +
>> +static void pgd_basic_tests(struct page *page, pgprot_t prot)
>> +{
>> +    pgd_t pgd;
>> +
>> +    memset(&pgd, RANDOM_NZVALUE, sizeof(pgd_t));
>> +    WARN_ON(!pgd_same(pgd, pgd));
>> +}
>> +
>> +#if !defined(__PAGETABLE_PMD_FOLDED) && !defined(__ARCH_HAS_4LEVEL_HACK)
>> +static void pud_clear_tests(pud_t *pudp)
>> +{
>> +    pud_t pud = READ_ONCE(*pudp);
>> +
>> +    pud = __pud(pud_val(pud) | RANDOM_ORVALUE);
>> +    WRITE_ONCE(*pudp, pud);
>> +    pud_clear(pudp);
>> +    pud = READ_ONCE(*pudp);
>> +    WARN_ON(!pud_none(pud));
>> +}
>> +
>> +static void pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
>> pmd_t *pmdp)
>> +{
>> +    pud_t pud;
>> +
>> +    /*
>> +     * This entry points to next level page table page.
>> +     * Hence this must not qualify as pud_bad().
>> +     */
>> +    pmd_clear(pmdp);
>> +    pud_clear(pudp);
>> +    pud_populate(mm, pudp, pmdp);
>> +    pud = READ_ONCE(*pudp);
>> +    WARN_ON(pud_bad(pud));
>> +}
>> +#else
>> +static void pud_clear_tests(pud_t *pudp) { }
>> +static void pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
>> pmd_t *pmdp)
>> +{
>> +}
>> +#endif
>> +
>> +#if !defined(__PAGETABLE_PUD_FOLDED) && !defined(__ARCH_HAS_5LEVEL_HACK)
>> +static void p4d_clear_tests(p4d_t *p4dp)
>> +{
>> +    p4d_t p4d = READ_ONCE(*p4dp);
>> +
>> +    p4d = __p4d(p4d_val(p4d) | RANDOM_ORVALUE);
>> +    WRITE_ONCE(*p4dp, p4d);
>> +    p4d_clear(p4dp);
>> +    p4d = READ_ONCE(*p4dp);
>> +    WARN_ON(!p4d_none(p4d));
>> +}
>> +
>> +static void p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp,
>> pud_t *pudp)
>> +{
>> +    p4d_t p4d;
>> +
>> +    /*
>> +     * This entry points to next level page table page.
>> +     * Hence this must not qualify as p4d_bad().
>> +     */
>> +    pud_clear(pudp);
>> +    p4d_clear(p4dp);
>> +    p4d_populate(mm, p4dp, pudp);
>> +    p4d = READ_ONCE(*p4dp);
>> +    WARN_ON(p4d_bad(p4d));
>> +}
>> +#else
>> +static void p4d_clear_tests(p4d_t *p4dp) { }
>> +static void p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp,
>> pud_t *pudp)
>> +{
>> +}
>> +#endif
>> +
>> +#ifndef __ARCH_HAS_5LEVEL_HACK
>> +static void pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp)
>> +{
>> +    pgd_t pgd = READ_ONCE(*pgdp);
>> +
>> +    if (mm_p4d_folded(mm))
>> +        return;
>> +
>> +    pgd = __pgd(pgd_val(pgd) | RANDOM_ORVALUE);
>> +    WRITE_ONCE(*pgdp, pgd);
>> +    pgd_clear(pgdp);
>> +    pgd = READ_ONCE(*pgdp);
>> +    WARN_ON(!pgd_none(pgd));
>> +}
>> +
>> +static void pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
>> p4d_t *p4dp)
>> +{
>> +    pgd_t pgd;
>> +
>> +    if (mm_p4d_folded(mm))
>> +        return;
>> +
>> +    /*
>> +     * This entry points to next level page table page.
>> +     * Hence this must not qualify as pgd_bad().
>> +     */
>> +    p4d_clear(p4dp);
>> +    pgd_clear(pgdp);
>> +    pgd_populate(mm, pgdp, p4dp);
>> +    pgd = READ_ONCE(*pgdp);
>> +    WARN_ON(pgd_bad(pgd));
>> +}
>> +#else
>> +static void pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp) { }
>> +static void pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
>> p4d_t *p4dp)
>> +{
>> +}
>> +#endif
>> +
>> +static void pte_clear_tests(struct mm_struct *mm, pte_t *ptep)
>> +{
>> +    pte_t pte = READ_ONCE(*ptep);
>> +
>> +    pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
>> +    WRITE_ONCE(*ptep, pte);
>> +    pte_clear(mm, 0, ptep);
>> +    pte = READ_ONCE(*ptep);
>> +    WARN_ON(!pte_none(pte));
>> +}
>> +
>> +static void pmd_clear_tests(pmd_t *pmdp)
>> +{
>> +    pmd_t pmd = READ_ONCE(*pmdp);
>> +
>> +    pmd = __pmd(pmd_val(pmd) | RANDOM_ORVALUE);
>> +    WRITE_ONCE(*pmdp, pmd);
>> +    pmd_clear(pmdp);
>> +    pmd = READ_ONCE(*pmdp);
>> +    WARN_ON(!pmd_none(pmd));
>> +}
>> +
>> +static void pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp,
>> +                   pgtable_t pgtable)
>> +{
>> +    pmd_t pmd;
>> +
>> +    /*
>> +     * This entry points to next level page table page.
>> +     * Hence this must not qualify as pmd_bad().
>> +     */
>> +    pmd_clear(pmdp);
>> +    pmd_populate(mm, pmdp, pgtable);
>> +    pmd = READ_ONCE(*pmdp);
>> +    WARN_ON(pmd_bad(pmd));
>> +}
>> +
>> +static struct page *alloc_mapped_page(void)
>> +{
>> +    struct page *page;
>> +    gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO;
>> +
>> +    page = alloc_gigantic_page_order(get_order(PUD_SIZE), gfp_mask,
>> +                first_memory_node, &node_states[N_MEMORY]);
>> +    if (page) {
>> +        pud_aligned = true;
>> +        pmd_aligned = true;
>> +        return page;
>> +    }
>> +
>> +    page = alloc_pages(gfp_mask, get_order(PMD_SIZE));
>> +    if (page) {
>> +        pmd_aligned = true;
>> +        return page;
>> +    }
>> +    return alloc_page(gfp_mask);
>> +}
>> +
>> +static void free_mapped_page(struct page *page)
>> +{
>> +    if (pud_aligned) {
>> +        unsigned long pfn = page_to_pfn(page);
>> +
>> +        free_contig_range(pfn, 1ULL << get_order(PUD_SIZE));
>> +        return;
>> +    }
>> +
>> +    if (pmd_aligned) {
>> +        int order = get_order(PMD_SIZE);
>> +
>> +        free_pages((unsigned long)page_address(page), order);
>> +        return;
>> +    }
>> +    free_page((unsigned long)page_address(page));
>> +}
>> +
>> +static unsigned long 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;
>> +
>> +    WARN_ON(random_vaddr > TASK_SIZE);
>> +    WARN_ON(random_vaddr < FIRST_USER_ADDRESS);
>> +    return random_vaddr;
>> +}
>> +
>> +static int __init arch_pgtable_tests_init(void)
>> +{
>> +    struct mm_struct *mm;
>> +    struct page *page;
>> +    pgd_t *pgdp;
>> +    p4d_t *p4dp, *saved_p4dp;
>> +    pud_t *pudp, *saved_pudp;
>> +    pmd_t *pmdp, *saved_pmdp, pmd;
>> +    pte_t *ptep;
>> +    pgtable_t saved_ptep;
>> +    pgprot_t prot;
>> +    unsigned long vaddr;
>> +
>> +    prot = vm_get_page_prot(VMFLAGS);
>> +    vaddr = get_random_vaddr();
>> +    mm = mm_alloc();
>> +    if (!mm) {
>> +        pr_err("mm_struct allocation failed\n");
>> +        return 1;
>> +    }
>> +
>> +    page = alloc_mapped_page();
>> +    if (!page) {
>> +        pr_err("memory allocation failed\n");
>> +        return 1;
>> +    }
>> +
>> +    pgdp = pgd_offset(mm, vaddr);
>> +    p4dp = p4d_alloc(mm, pgdp, vaddr);
>> +    pudp = pud_alloc(mm, p4dp, vaddr);
>> +    pmdp = pmd_alloc(mm, pudp, vaddr);
>> +    ptep = pte_alloc_map(mm, pmdp, vaddr);
>> +
>> +    /*
>> +     * Save all the page table page addresses as the page table
>> +     * entries will be used for testing with random or garbage
>> +     * values. These saved addresses will be used for freeing
>> +     * page table pages.
>> +     */
>> +    pmd = READ_ONCE(*pmdp);
>> +    saved_p4dp = p4d_offset(pgdp, 0UL);
>> +    saved_pudp = pud_offset(p4dp, 0UL);
>> +    saved_pmdp = pmd_offset(pudp, 0UL);
>> +    saved_ptep = pmd_pgtable(pmd);
>> +
>> +    pte_basic_tests(page, prot);
>> +    pmd_basic_tests(page, prot);
>> +    pud_basic_tests(page, prot);
>> +    p4d_basic_tests(page, prot);
>> +    pgd_basic_tests(page, prot);
>> +
>> +    pte_clear_tests(mm, ptep);
>> +    pmd_clear_tests(pmdp);
>> +    pud_clear_tests(pudp);
>> +    p4d_clear_tests(p4dp);
>> +    pgd_clear_tests(mm, pgdp);
>> +
>> +    pmd_populate_tests(mm, pmdp, saved_ptep);
>> +    pud_populate_tests(mm, pudp, saved_pmdp);
>> +    p4d_populate_tests(mm, p4dp, saved_pudp);
>> +    pgd_populate_tests(mm, pgdp, saved_p4dp);
>> +
>> +    p4d_free(mm, saved_p4dp);
>> +    pud_free(mm, saved_pudp);
>> +    pmd_free(mm, saved_pmdp);
>> +    pte_free(mm, saved_ptep);
>> +
>> +    mm_dec_nr_puds(mm);
>> +    mm_dec_nr_pmds(mm);
>> +    mm_dec_nr_ptes(mm);
>> +    __mmdrop(mm);
>> +
>> +    free_mapped_page(page);
>> +    return 0;
>> +}
>> +
>> +static void __exit arch_pgtable_tests_exit(void) { }
>> +
>> +module_init(arch_pgtable_tests_init);
>> +module_exit(arch_pgtable_tests_exit);
>> +
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_AUTHOR("Anshuman Khandual <anshuman.khandual@arm.com>");
>> +MODULE_DESCRIPTION("Test architecture page table helpers");
>>