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    Subject[PATCH v8 16/27] mm: Handle THP/HugeTLB shadow stack page fault
    Date
    This patch implements THP shadow stack (SHSTK) copying in the same
    way as in the previous patch for regular PTE.

    In copy_huge_pmd(), clear the dirty bit from the PMD to cause a page
    fault upon the next SHSTK access to the PMD. At that time, fix the
    PMD and copy/re-use the page.

    Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
    ---
    arch/x86/mm/pgtable.c | 8 ++++++++
    include/asm-generic/pgtable.h | 6 ++++++
    mm/huge_memory.c | 4 ++++
    3 files changed, 18 insertions(+)

    diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
    index 0c10d0c5e329..6f3959ca2a08 100644
    --- a/arch/x86/mm/pgtable.c
    +++ b/arch/x86/mm/pgtable.c
    @@ -886,6 +886,14 @@ inline pte_t pte_set_vma_features(pte_t pte, struct vm_area_struct *vma)
    return pte;
    }

    +inline pmd_t pmd_set_vma_features(pmd_t pmd, struct vm_area_struct *vma)
    +{
    + if (vma->vm_flags & VM_SHSTK)
    + return pmd_mkdirty_shstk(pmd);
    + else
    + return pmd;
    +}
    +
    inline bool arch_copy_pte_mapping(vm_flags_t vm_flags)
    {
    return (vm_flags & VM_SHSTK);
    diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
    index 89b0fa132f1f..438ce73b57ea 100644
    --- a/include/asm-generic/pgtable.h
    +++ b/include/asm-generic/pgtable.h
    @@ -1194,12 +1194,18 @@ static inline pte_t pte_set_vma_features(pte_t pte, struct vm_area_struct *vma)
    return pte;
    }

    +static inline pmd_t pmd_set_vma_features(pmd_t pmd, struct vm_area_struct *vma)
    +{
    + return pmd;
    +}
    +
    static inline bool arch_copy_pte_mapping(vm_flags_t vm_flags)
    {
    return false;
    }
    #else
    pte_t pte_set_vma_features(pte_t pte, struct vm_area_struct *vma);
    +pmd_t pmd_set_vma_features(pmd_t pmd, struct vm_area_struct *vma);
    bool arch_copy_pte_mapping(vm_flags_t vm_flags);
    #endif

    diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    index 1334ede667a8..39d66c628121 100644
    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -611,6 +611,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,

    entry = mk_huge_pmd(page, vma->vm_page_prot);
    entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
    + entry = pmd_set_vma_features(entry, vma);
    page_add_new_anon_rmap(page, vma, haddr, true);
    mem_cgroup_commit_charge(page, memcg, false, true);
    lru_cache_add_active_or_unevictable(page, vma);
    @@ -1253,6 +1254,7 @@ static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
    pte_t entry;
    entry = mk_pte(pages[i], vma->vm_page_prot);
    entry = maybe_mkwrite(pte_mkdirty(entry), vma);
    + entry = pte_set_vma_features(entry, vma);
    memcg = (void *)page_private(pages[i]);
    set_page_private(pages[i], 0);
    page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
    @@ -1335,6 +1337,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
    pmd_t entry;
    entry = pmd_mkyoung(orig_pmd);
    entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
    + entry = pmd_set_vma_features(entry, vma);
    if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
    update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
    ret |= VM_FAULT_WRITE;
    @@ -1407,6 +1410,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
    pmd_t entry;
    entry = mk_huge_pmd(new_page, vma->vm_page_prot);
    entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
    + entry = pmd_set_vma_features(entry, vma);
    pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
    page_add_new_anon_rmap(new_page, vma, haddr, true);
    mem_cgroup_commit_charge(new_page, memcg, false, true);
    --
    2.17.1
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