diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/mm.h | 43 | ||||
| -rw-r--r-- | include/linux/userfaultfd_k.h | 45 |
2 files changed, 64 insertions, 24 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 3dca9497ae03..61bcd65cd029 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -354,6 +354,7 @@ enum { #endif DECLARE_VMA_BIT(UFFD_MINOR, 41), DECLARE_VMA_BIT(SEALED, 42), + DECLARE_VMA_BIT(UFFD_RWP, 43), /* Flags that reuse flags above. */ DECLARE_VMA_BIT_ALIAS(PKEY_BIT0, HIGH_ARCH_0), DECLARE_VMA_BIT_ALIAS(PKEY_BIT1, HIGH_ARCH_1), @@ -497,12 +498,17 @@ enum { #else #define VM_UFFD_MINOR VM_NONE #endif +#ifdef CONFIG_USERFAULTFD_RWP +#define VM_UFFD_RWP INIT_VM_FLAG(UFFD_RWP) +#else +#define VM_UFFD_RWP VM_NONE +#endif /* - * vma_flags_t masks for the userfaultfd VMA flags. VMA_UFFD_MINOR is gated on - * the same config as VM_UFFD_MINOR -- which implies 64BIT, where the bit fits - * -- so an out-of-range bit is never fed to mk_vma_flags() on a build whose - * bitmap cannot hold it. + * vma_flags_t masks for the userfaultfd VMA flags. The two high-bit modes are + * gated on the same configs as their VM_* flags above -- both of which imply + * 64BIT -- so an out-of-range bit is never fed to mk_vma_flags() on a build + * whose bitmap cannot hold it. */ #define VMA_UFFD_MISSING mk_vma_flags(VMA_UFFD_MISSING_BIT) #define VMA_UFFD_WP mk_vma_flags(VMA_UFFD_WP_BIT) @@ -511,6 +517,11 @@ enum { #else #define VMA_UFFD_MINOR EMPTY_VMA_FLAGS #endif +#ifdef CONFIG_USERFAULTFD_RWP +#define VMA_UFFD_RWP mk_vma_flags(VMA_UFFD_RWP_BIT) +#else +#define VMA_UFFD_RWP EMPTY_VMA_FLAGS +#endif #ifdef CONFIG_64BIT #define VM_ALLOW_ANY_UNCACHED INIT_VM_FLAG(ALLOW_ANY_UNCACHED) @@ -649,22 +660,24 @@ enum { * reconsistuted upon page fault, so necessitate page table copying upon fork. * * Note that these flags should be compared with the DESTINATION VMA not the - * source, as VM_UFFD_WP may not be propagated to destination, while all other - * flags will be. + * source: VM_UFFD_WP and VM_UFFD_RWP may be cleared on the destination + * (dup_userfaultfd() -> userfaultfd_reset_ctx() when the parent context did + * not negotiate UFFD_FEATURE_EVENT_FORK), while all other flags propagate. * * VM_PFNMAP / VM_MIXEDMAP - These contain kernel-mapped data which cannot be * reasonably reconstructed on page fault. * * VM_UFFD_WP - Encodes metadata about an installed uffd - * write protect handler, which cannot be - * reconstructed on page fault. - * - * We always copy pgtables when dst_vma has uffd-wp - * enabled even if it's file-backed - * (e.g. shmem). Because when uffd-wp is enabled, - * pgtable contains uffd-wp protection information, - * that's something we can't retrieve from page cache, - * and skip copying will lose those info. + * VM_UFFD_RWP write- or read-write-protect handler, which + * cannot be reconstructed on page fault. + * + * We always copy pgtables when dst_vma has the + * uffd PTE bit in use even if it's file-backed + * (e.g. shmem). Because when the uffd bit is + * in use, the pgtable contains the protection + * information, that's something we can't + * retrieve from page cache, and skip copying + * will lose those info. * * VM_MAYBE_GUARD - Could contain page guard region markers which * by design are a property of the page tables diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index c4f2cc6dfcf0..6dad14b9abb9 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -21,10 +21,11 @@ #include <linux/hugetlb_inline.h> /* The set of all possible UFFD-related VM flags. */ -#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR) +#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_MINOR | \ + VM_UFFD_WP | VM_UFFD_RWP) #define __VMA_UFFD_FLAGS mk_vma_flags_from_masks(VMA_UFFD_MISSING, VMA_UFFD_WP, \ - VMA_UFFD_MINOR) + VMA_UFFD_MINOR, VMA_UFFD_RWP) /* * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining @@ -168,7 +169,8 @@ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, /* * Never enable huge pmd sharing on some uffd registered vmas: * - * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry. + * - VM_UFFD_WP and VM_UFFD_RWP VMAs, because the write protect / access + * tracking information is per pgtable entry. * * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for * VMAs which share huge pmds. (If you have two mappings to the same @@ -179,20 +181,25 @@ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma) { return vma_test_any_mask(vma, - mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_MINOR)); + mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_RWP, + VMA_UFFD_MINOR)); } /* - * Don't do fault around for either WP or MINOR registered uffd range. For + * Don't do fault around for WP, RWP or MINOR registered uffd range. For * MINOR registered range, fault around will be a total disaster and ptes can * be installed without notifications; for WP it should mostly be fine as long * as the fault around checks for pte_none() before the installation, however - * to be super safe we just forbid it. + * to be super safe we just forbid it; for RWP, pre-faulted neighbours would + * be indistinguishable from accessed pages in PAGEMAP_SCAN (PAGE_IS_ACCESSED) + * and pollute the tracked working set, so each page must be populated by its + * own fault. */ static inline bool uffd_disable_fault_around(struct vm_area_struct *vma) { return vma_test_any_mask(vma, - mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_MINOR)); + mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_RWP, + VMA_UFFD_MINOR)); } static inline bool userfaultfd_missing(struct vm_area_struct *vma) @@ -210,6 +217,16 @@ static inline bool userfaultfd_minor(struct vm_area_struct *vma) return vma_test_any_mask(vma, VMA_UFFD_MINOR); } +static inline bool userfaultfd_rwp(struct vm_area_struct *vma) +{ + return vma_test_single_mask(vma, VMA_UFFD_RWP); +} + +static inline bool userfaultfd_protected(struct vm_area_struct *vma) +{ + return userfaultfd_wp(vma) || userfaultfd_rwp(vma); +} + static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma, pte_t pte) { @@ -330,6 +347,16 @@ static inline bool userfaultfd_minor(struct vm_area_struct *vma) return false; } +static inline bool userfaultfd_rwp(struct vm_area_struct *vma) +{ + return false; +} + +static inline bool userfaultfd_protected(struct vm_area_struct *vma) +{ + return false; +} + static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma, pte_t pte) { @@ -423,8 +450,8 @@ static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma) } /* - * Returns true if this is a swap pte and was uffd-wp wr-protected in either - * forms (pte marker or a normal swap pte), false otherwise. + * Returns true if this swap pte carries uffd-tracked state in either + * form (pte marker or a normal swap pte), false otherwise. */ static inline bool pte_swp_uffd_any(pte_t pte) { |