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The x86 Shadow stack feature includes a new type of memory called shadow stack. This shadow stack memory has some unusual properties, which requires some core mm changes to function properly. One of these unusual properties is that shadow stack memory is writable, but only in limited ways. These limits are applied via a specific PTE bit combination. Nevertheless, the memory is writable, and core mm code will need to apply the writable permissions in the typical paths that call pte_mkwrite(). Future patches will make pte_mkwrite() take a VMA, so that the x86 implementation of it can know whether to create regular writable or shadow stack mappings. But there are a couple of challenges to this. Modifying the signatures of each arch pte_mkwrite() implementation would be error prone because some are generated with macros and would need to be re-implemented. Also, some pte_mkwrite() callers operate on kernel memory without a VMA. So this can be done in a three step process. First pte_mkwrite() can be renamed to pte_mkwrite_novma() in each arch, with a generic pte_mkwrite() added that just calls pte_mkwrite_novma(). Next callers without a VMA can be moved to pte_mkwrite_novma(). And lastly, pte_mkwrite() and all callers can be changed to take/pass a VMA. Previous work pte_mkwrite() renamed pte_mkwrite_novma() and converted callers that don't have a VMA were to use pte_mkwrite_novma(). So now change pte_mkwrite() to take a VMA and change the remaining callers to pass a VMA. Apply the same changes for pmd_mkwrite(). No functional change. Suggested-by: David Hildenbrand <david@redhat.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/all/20230613001108.3040476-4-rick.p.edgecombe%40intel.com
266 lines
19 KiB
ReStructuredText
266 lines
19 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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===============================
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Architecture Page Table Helpers
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===============================
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Generic MM expects architectures (with MMU) to provide helpers to create, access
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and modify page table entries at various level for different memory functions.
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These page table helpers need to conform to a common semantics across platforms.
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Following tables describe the expected semantics which can also be tested during
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boot via CONFIG_DEBUG_VM_PGTABLE option. All future changes in here or the debug
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test need to be in sync.
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PTE Page Table Helpers
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======================
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+---------------------------+--------------------------------------------------+
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| pte_same | Tests whether both PTE entries are the same |
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+---------------------------+--------------------------------------------------+
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| pte_bad | Tests a non-table mapped PTE |
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+---------------------------+--------------------------------------------------+
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| pte_present | Tests a valid mapped PTE |
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+---------------------------+--------------------------------------------------+
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| pte_young | Tests a young PTE |
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+---------------------------+--------------------------------------------------+
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| pte_dirty | Tests a dirty PTE |
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+---------------------------+--------------------------------------------------+
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| pte_write | Tests a writable PTE |
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+---------------------------+--------------------------------------------------+
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| pte_special | Tests a special PTE |
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+---------------------------+--------------------------------------------------+
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| pte_protnone | Tests a PROT_NONE PTE |
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+---------------------------+--------------------------------------------------+
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| pte_devmap | Tests a ZONE_DEVICE mapped PTE |
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+---------------------------+--------------------------------------------------+
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| pte_soft_dirty | Tests a soft dirty PTE |
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+---------------------------+--------------------------------------------------+
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| pte_swp_soft_dirty | Tests a soft dirty swapped PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mkyoung | Creates a young PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mkold | Creates an old PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mkdirty | Creates a dirty PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mkclean | Creates a clean PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mkwrite | Creates a writable PTE of the type specified by |
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| | the VMA. |
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+---------------------------+--------------------------------------------------+
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| pte_mkwrite_novma | Creates a writable PTE, of the conventional type |
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| | of writable. |
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+---------------------------+--------------------------------------------------+
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| pte_wrprotect | Creates a write protected PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mkspecial | Creates a special PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mkdevmap | Creates a ZONE_DEVICE mapped PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mksoft_dirty | Creates a soft dirty PTE |
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+---------------------------+--------------------------------------------------+
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| pte_clear_soft_dirty | Clears a soft dirty PTE |
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+---------------------------+--------------------------------------------------+
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| pte_swp_mksoft_dirty | Creates a soft dirty swapped PTE |
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+---------------------------+--------------------------------------------------+
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| pte_swp_clear_soft_dirty | Clears a soft dirty swapped PTE |
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+---------------------------+--------------------------------------------------+
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| pte_mknotpresent | Invalidates a mapped PTE |
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+---------------------------+--------------------------------------------------+
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| ptep_clear | Clears a PTE |
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+---------------------------+--------------------------------------------------+
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| ptep_get_and_clear | Clears and returns PTE |
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+---------------------------+--------------------------------------------------+
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| ptep_get_and_clear_full | Clears and returns PTE (batched PTE unmap) |
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+---------------------------+--------------------------------------------------+
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| ptep_test_and_clear_young | Clears young from a PTE |
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+---------------------------+--------------------------------------------------+
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| ptep_set_wrprotect | Converts into a write protected PTE |
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+---------------------------+--------------------------------------------------+
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| ptep_set_access_flags | Converts into a more permissive PTE |
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+---------------------------+--------------------------------------------------+
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PMD Page Table Helpers
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======================
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+---------------------------+--------------------------------------------------+
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| pmd_same | Tests whether both PMD entries are the same |
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+---------------------------+--------------------------------------------------+
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| pmd_bad | Tests a non-table mapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_leaf | Tests a leaf mapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_huge | Tests a HugeTLB mapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_trans_huge | Tests a Transparent Huge Page (THP) at PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_present | Tests whether pmd_page() points to valid memory |
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+---------------------------+--------------------------------------------------+
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| pmd_young | Tests a young PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_dirty | Tests a dirty PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_write | Tests a writable PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_special | Tests a special PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_protnone | Tests a PROT_NONE PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_devmap | Tests a ZONE_DEVICE mapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_soft_dirty | Tests a soft dirty PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_swp_soft_dirty | Tests a soft dirty swapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkyoung | Creates a young PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkold | Creates an old PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkdirty | Creates a dirty PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkclean | Creates a clean PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkwrite | Creates a writable PMD of the type specified by |
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| | the VMA. |
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+---------------------------+--------------------------------------------------+
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| pmd_mkwrite_novma | Creates a writable PMD, of the conventional type |
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| | of writable. |
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+---------------------------+--------------------------------------------------+
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| pmd_wrprotect | Creates a write protected PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkspecial | Creates a special PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkdevmap | Creates a ZONE_DEVICE mapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mksoft_dirty | Creates a soft dirty PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_clear_soft_dirty | Clears a soft dirty PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_swp_mksoft_dirty | Creates a soft dirty swapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_swp_clear_soft_dirty | Clears a soft dirty swapped PMD |
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+---------------------------+--------------------------------------------------+
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| pmd_mkinvalid | Invalidates a mapped PMD [1] |
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+---------------------------+--------------------------------------------------+
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| pmd_set_huge | Creates a PMD huge mapping |
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+---------------------------+--------------------------------------------------+
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| pmd_clear_huge | Clears a PMD huge mapping |
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+---------------------------+--------------------------------------------------+
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| pmdp_get_and_clear | Clears a PMD |
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+---------------------------+--------------------------------------------------+
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| pmdp_get_and_clear_full | Clears a PMD |
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+---------------------------+--------------------------------------------------+
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| pmdp_test_and_clear_young | Clears young from a PMD |
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+---------------------------+--------------------------------------------------+
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| pmdp_set_wrprotect | Converts into a write protected PMD |
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+---------------------------+--------------------------------------------------+
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| pmdp_set_access_flags | Converts into a more permissive PMD |
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+---------------------------+--------------------------------------------------+
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PUD Page Table Helpers
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======================
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+---------------------------+--------------------------------------------------+
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| pud_same | Tests whether both PUD entries are the same |
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+---------------------------+--------------------------------------------------+
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| pud_bad | Tests a non-table mapped PUD |
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+---------------------------+--------------------------------------------------+
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| pud_leaf | Tests a leaf mapped PUD |
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+---------------------------+--------------------------------------------------+
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| pud_huge | Tests a HugeTLB mapped PUD |
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+---------------------------+--------------------------------------------------+
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| pud_trans_huge | Tests a Transparent Huge Page (THP) at PUD |
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+---------------------------+--------------------------------------------------+
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| pud_present | Tests a valid mapped PUD |
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+---------------------------+--------------------------------------------------+
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| pud_young | Tests a young PUD |
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+---------------------------+--------------------------------------------------+
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| pud_dirty | Tests a dirty PUD |
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+---------------------------+--------------------------------------------------+
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| pud_write | Tests a writable PUD |
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+---------------------------+--------------------------------------------------+
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| pud_devmap | Tests a ZONE_DEVICE mapped PUD |
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+---------------------------+--------------------------------------------------+
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| pud_mkyoung | Creates a young PUD |
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+---------------------------+--------------------------------------------------+
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| pud_mkold | Creates an old PUD |
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+---------------------------+--------------------------------------------------+
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| pud_mkdirty | Creates a dirty PUD |
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+---------------------------+--------------------------------------------------+
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| pud_mkclean | Creates a clean PUD |
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+---------------------------+--------------------------------------------------+
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| pud_mkwrite | Creates a writable PUD |
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+---------------------------+--------------------------------------------------+
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| pud_wrprotect | Creates a write protected PUD |
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+---------------------------+--------------------------------------------------+
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| pud_mkdevmap | Creates a ZONE_DEVICE mapped PUD |
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+---------------------------+--------------------------------------------------+
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| pud_mkinvalid | Invalidates a mapped PUD [1] |
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+---------------------------+--------------------------------------------------+
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| pud_set_huge | Creates a PUD huge mapping |
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+---------------------------+--------------------------------------------------+
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| pud_clear_huge | Clears a PUD huge mapping |
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+---------------------------+--------------------------------------------------+
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| pudp_get_and_clear | Clears a PUD |
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+---------------------------+--------------------------------------------------+
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| pudp_get_and_clear_full | Clears a PUD |
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+---------------------------+--------------------------------------------------+
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| pudp_test_and_clear_young | Clears young from a PUD |
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+---------------------------+--------------------------------------------------+
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| pudp_set_wrprotect | Converts into a write protected PUD |
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+---------------------------+--------------------------------------------------+
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| pudp_set_access_flags | Converts into a more permissive PUD |
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+---------------------------+--------------------------------------------------+
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HugeTLB Page Table Helpers
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==========================
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+---------------------------+--------------------------------------------------+
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| pte_huge | Tests a HugeTLB |
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+---------------------------+--------------------------------------------------+
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| arch_make_huge_pte | Creates a HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_pte_dirty | Tests a dirty HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_pte_write | Tests a writable HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_pte_mkdirty | Creates a dirty HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_pte_mkwrite | Creates a writable HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_pte_wrprotect | Creates a write protected HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_ptep_get_and_clear | Clears a HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_ptep_set_wrprotect | Converts into a write protected HugeTLB |
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+---------------------------+--------------------------------------------------+
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| huge_ptep_set_access_flags | Converts into a more permissive HugeTLB |
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+---------------------------+--------------------------------------------------+
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SWAP Page Table Helpers
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========================
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+---------------------------+--------------------------------------------------+
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| __pte_to_swp_entry | Creates a swapped entry (arch) from a mapped PTE |
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+---------------------------+--------------------------------------------------+
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| __swp_to_pte_entry | Creates a mapped PTE from a swapped entry (arch) |
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+---------------------------+--------------------------------------------------+
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| __pmd_to_swp_entry | Creates a swapped entry (arch) from a mapped PMD |
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+---------------------------+--------------------------------------------------+
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| __swp_to_pmd_entry | Creates a mapped PMD from a swapped entry (arch) |
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+---------------------------+--------------------------------------------------+
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| is_migration_entry | Tests a migration (read or write) swapped entry |
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+-------------------------------+----------------------------------------------+
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| is_writable_migration_entry | Tests a write migration swapped entry |
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+-------------------------------+----------------------------------------------+
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| make_readable_migration_entry | Creates a read migration swapped entry |
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+-------------------------------+----------------------------------------------+
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| make_writable_migration_entry | Creates a write migration swapped entry |
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+-------------------------------+----------------------------------------------+
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[1] https://lore.kernel.org/linux-mm/20181017020930.GN30832@redhat.com/
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