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    Subject[PATCH 12/12] mm/debug_vm_pgtable: Fix corrupted page flag
    Date
    In page table entry modifying tests, set_{pud, pmd, pte}_at() are
    used to populate the page table entries. On ARM64, PG_arch_1 is
    set to the target page flag if execution permission is given. The
    page flag is kept when the page is free'd to buddy's free area
    list. However, it will trigger page checking failure when it's
    pulled from the buddy's free area list, as the following warning
    messages indicate.

    BUG: Bad page state in process memhog pfn:08000
    page:0000000015c0a628 refcount:0 mapcount:0 \
    mapping:0000000000000000 index:0x1 pfn:0x8000
    flags: 0x7ffff8000000800(arch_1|node=0|zone=0|lastcpupid=0xfffff)
    raw: 07ffff8000000800 dead000000000100 dead000000000122 0000000000000000
    raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
    page dumped because: PAGE_FLAGS_CHECK_AT_PREP flag(s) set

    This fixes the issue by clearing PG_arch_1 through flush_dcache_page(),
    right after set_{pud, pmd, pte}_at() is called.

    Signed-off-by: Gavin Shan <gshan@redhat.com>
    ---
    mm/debug_vm_pgtable.c | 36 ++++++++++++++++++++++++++++++++----
    1 file changed, 32 insertions(+), 4 deletions(-)

    diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
    index 1fd6d73d2152..de6f99382b4b 100644
    --- a/mm/debug_vm_pgtable.c
    +++ b/mm/debug_vm_pgtable.c
    @@ -29,6 +29,8 @@
    #include <linux/start_kernel.h>
    #include <linux/sched/mm.h>
    #include <linux/io.h>
    +
    +#include <asm/cacheflush.h>
    #include <asm/pgalloc.h>
    #include <asm/tlbflush.h>

    @@ -110,6 +112,7 @@ static void __init pte_basic_tests(struct vm_pgtable_debug *debug, int idx)

    static void __init pte_advanced_tests(struct vm_pgtable_debug *debug)
    {
    + struct page *page;
    pte_t pte;

    /*
    @@ -119,13 +122,17 @@ static void __init pte_advanced_tests(struct vm_pgtable_debug *debug)
    */

    pr_debug("Validating PTE advanced\n");
    - if (debug->pte_pfn == ULONG_MAX) {
    +
    + page = (debug->pte_pfn != ULONG_MAX) ?
    + pfn_to_page(debug->pte_pfn) : NULL;
    + if (!page) {
    pr_debug("%s: Skipped\n", __func__);
    return;
    }

    pte = pfn_pte(debug->pte_pfn, debug->page_prot);
    set_pte_at(debug->mm, debug->vaddr, debug->ptep, pte);
    + flush_dcache_page(page);
    ptep_set_wrprotect(debug->mm, debug->vaddr, debug->ptep);
    pte = ptep_get(debug->ptep);
    WARN_ON(pte_write(pte));
    @@ -137,6 +144,7 @@ static void __init pte_advanced_tests(struct vm_pgtable_debug *debug)
    pte = pte_wrprotect(pte);
    pte = pte_mkclean(pte);
    set_pte_at(debug->mm, debug->vaddr, debug->ptep, pte);
    + flush_dcache_page(page);
    pte = pte_mkwrite(pte);
    pte = pte_mkdirty(pte);
    ptep_set_access_flags(debug->vma, debug->vaddr, debug->ptep, pte, 1);
    @@ -149,6 +157,7 @@ static void __init pte_advanced_tests(struct vm_pgtable_debug *debug)
    pte = pfn_pte(debug->pte_pfn, debug->page_prot);
    pte = pte_mkyoung(pte);
    set_pte_at(debug->mm, debug->vaddr, debug->ptep, pte);
    + flush_dcache_page(page);
    ptep_test_and_clear_young(debug->vma, debug->vaddr, debug->ptep);
    pte = ptep_get(debug->ptep);
    WARN_ON(pte_young(pte));
    @@ -207,6 +216,7 @@ static void __init pmd_basic_tests(struct vm_pgtable_debug *debug, int idx)

    static void __init pmd_advanced_tests(struct vm_pgtable_debug *debug)
    {
    + struct page *page;
    pmd_t pmd;
    unsigned long vaddr = (debug->vaddr & HPAGE_PMD_MASK);

    @@ -214,7 +224,10 @@ static void __init pmd_advanced_tests(struct vm_pgtable_debug *debug)
    return;

    pr_debug("Validating PMD advanced\n");
    - if (debug->pmd_pfn == ULONG_MAX) {
    +
    + page = (debug->pmd_pfn != ULONG_MAX) ?
    + pfn_to_page(debug->pmd_pfn) : NULL;
    + if (!page) {
    pr_debug("%s: Skipped\n", __func__);
    return;
    }
    @@ -223,6 +236,7 @@ static void __init pmd_advanced_tests(struct vm_pgtable_debug *debug)

    pmd = pfn_pmd(debug->pmd_pfn, debug->page_prot);
    set_pmd_at(debug->mm, vaddr, debug->pmdp, pmd);
    + flush_dcache_page(page);
    pmdp_set_wrprotect(debug->mm, vaddr, debug->pmdp);
    pmd = READ_ONCE(*(debug->pmdp));
    WARN_ON(pmd_write(pmd));
    @@ -234,6 +248,7 @@ static void __init pmd_advanced_tests(struct vm_pgtable_debug *debug)
    pmd = pmd_wrprotect(pmd);
    pmd = pmd_mkclean(pmd);
    set_pmd_at(debug->mm, vaddr, debug->pmdp, pmd);
    + flush_dcache_page(page);
    pmd = pmd_mkwrite(pmd);
    pmd = pmd_mkdirty(pmd);
    pmdp_set_access_flags(debug->vma, vaddr, debug->pmdp, pmd, 1);
    @@ -246,6 +261,7 @@ static void __init pmd_advanced_tests(struct vm_pgtable_debug *debug)
    pmd = pmd_mkhuge(pfn_pmd(debug->pmd_pfn, debug->page_prot));
    pmd = pmd_mkyoung(pmd);
    set_pmd_at(debug->mm, vaddr, debug->pmdp, pmd);
    + flush_dcache_page(page);
    pmdp_test_and_clear_young(debug->vma, vaddr, debug->pmdp);
    pmd = READ_ONCE(*(debug->pmdp));
    WARN_ON(pmd_young(pmd));
    @@ -332,6 +348,7 @@ static void __init pud_basic_tests(struct vm_pgtable_debug *debug, int idx)

    static void __init pud_advanced_tests(struct vm_pgtable_debug *debug)
    {
    + struct page *page;
    unsigned long vaddr = (debug->vaddr & HPAGE_PUD_MASK);
    pud_t pud;

    @@ -339,13 +356,17 @@ static void __init pud_advanced_tests(struct vm_pgtable_debug *debug)
    return;

    pr_debug("Validating PUD advanced\n");
    - if (debug->pud_pfn == ULONG_MAX) {
    +
    + page = (debug->pud_pfn != ULONG_MAX) ?
    + pfn_to_page(debug->pud_pfn) : NULL;
    + if (!page) {
    pr_debug("%s: Skipped\n", __func__);
    return;
    }

    pud = pfn_pud(debug->pud_pfn, debug->page_prot);
    set_pud_at(debug->mm, vaddr, debug->pudp, pud);
    + flush_dcache_page(page);
    pudp_set_wrprotect(debug->mm, vaddr, debug->pudp);
    pud = READ_ONCE(*(debug->pudp));
    WARN_ON(pud_write(pud));
    @@ -359,6 +380,7 @@ static void __init pud_advanced_tests(struct vm_pgtable_debug *debug)
    pud = pud_wrprotect(pud);
    pud = pud_mkclean(pud);
    set_pud_at(debug->mm, vaddr, debug->pudp, pud);
    + flush_dcache_page(page);
    pud = pud_mkwrite(pud);
    pud = pud_mkdirty(pud);
    pudp_set_access_flags(debug->vma, vaddr, debug->pudp, pud, 1);
    @@ -374,6 +396,7 @@ static void __init pud_advanced_tests(struct vm_pgtable_debug *debug)
    pud = pfn_pud(debug->pud_pfn, debug->page_prot);
    pud = pud_mkyoung(pud);
    set_pud_at(debug->mm, vaddr, debug->pudp, pud);
    + flush_dcache_page(page);
    pudp_test_and_clear_young(debug->vma, vaddr, debug->pudp);
    pud = READ_ONCE(*(debug->pudp));
    WARN_ON(pud_young(pud));
    @@ -588,10 +611,14 @@ static void __init pgd_populate_tests(struct vm_pgtable_debug *debug) { }

    static void __init pte_clear_tests(struct vm_pgtable_debug *debug)
    {
    + struct page *page;
    pte_t pte;

    pr_debug("Validating PTE clear\n");
    - if (debug->pte_pfn == ULONG_MAX) {
    +
    + page = (debug->pte_pfn != ULONG_MAX) ?
    + pfn_to_page(debug->pte_pfn) : NULL;
    + if (!page) {
    pr_debug("%s: Skipped\n", __func__);
    return;
    }
    @@ -601,6 +628,7 @@ static void __init pte_clear_tests(struct vm_pgtable_debug *debug)
    pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
    #endif
    set_pte_at(debug->mm, debug->vaddr, debug->ptep, pte);
    + flush_dcache_page(page);
    barrier();
    pte_clear(debug->mm, debug->vaddr, debug->ptep);
    pte = ptep_get(debug->ptep);
    --
    2.23.0
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