On Fri, May 08, 2026 at 04:55:16PM +0100, Kiryl Shutsemau (Meta) wrote: > Preparatory patch for userfaultfd read-write protection (RWP). RWP > extends userfaultfd protection from plain write-protection (WP) to > full read-write protection: accesses to an RWP-protected range -- > reads as well as writes -- trap through userfaultfd. > > RWP marks ranges by combining PAGE_NONE with the uffd PTE bit, so > the flag is only meaningful when both primitives exist. A new > CONFIG_USERFAULTFD_RWP Kconfig symbol auto-selects when CONFIG_64BIT, > CONFIG_ARCH_HAS_PTE_PROTNONE, and CONFIG_HAVE_ARCH_USERFAULTFD_WP > are all set; call sites that gate on the flag depend on the symbol. > Elsewhere VM_UFFD_RWP aliases VM_NONE and every downstream check > folds to dead code. > > Nothing sets the flag yet.
And nothing check for it as well, am I right? Worth noting here, IMHO. > Signed-off-by: Kiryl Shutsemau <[email protected]> > Assisted-by: Claude:claude-opus-4-6 > --- > Documentation/filesystems/proc.rst | 1 + > fs/proc/task_mmu.c | 3 +++ > include/linux/mm.h | 28 +++++++++++++++++---------- > include/linux/userfaultfd_k.h | 31 +++++++++++++++++++++++++----- > include/trace/events/mmflags.h | 7 +++++++ > mm/Kconfig | 9 +++++++++ > 6 files changed, 64 insertions(+), 15 deletions(-) > > diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h > index 98f546e83cd2..fcf308dba311 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_WP | VM_UFFD_MINOR | \ > + VM_UFFD_RWP) Nit: can we keep mode bits together and protection bits together here and in the below changes? Otherwise looks good to me Reviewed-by: Mike Rapoport (Microsoft) <[email protected]> > #define __VMA_UFFD_FLAGS mk_vma_flags(VMA_UFFD_MISSING_BIT, VMA_UFFD_WP_BIT, > \ > - VMA_UFFD_MINOR_BIT) > + VMA_UFFD_MINOR_BIT, VMA_UFFD_RWP_BIT) > > /* > * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining > @@ -192,7 +193,7 @@ 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->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR); > + return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR | VM_UFFD_RWP); > } > > /* > @@ -222,6 +223,16 @@ static inline bool userfaultfd_minor(struct > vm_area_struct *vma) > return vma->vm_flags & VM_UFFD_MINOR; > } > > +static inline bool userfaultfd_rwp(struct vm_area_struct *vma) > +{ > + return vma->vm_flags & VM_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) > { -- Sincerely yours, Mike.
