On Fri, Sep 27, 2024 at 2:51 PM Lorenzo Stoakes lorenzo.stoakes@oracle.com wrote:
Add a new PTE marker that results in any access causing the accessing process to segfault.
[...]
static inline int is_poisoned_swp_entry(swp_entry_t entry) +{
/** We treat guard pages as poisoned too as these have the same semantics* as poisoned ranges, only with different fault handling.*/return is_pte_marker_entry(entry) &&(pte_marker_get(entry) &(PTE_MARKER_POISONED | PTE_MARKER_GUARD));+}
This means MADV_FREE will also clear guard PTEs, right?
diff --git a/mm/memory.c b/mm/memory.c index 5c6486e33e63..6c413c3d72fd 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1457,7 +1457,7 @@ static inline bool should_zap_folio(struct zap_details *details, return !folio_test_anon(folio); }
-static inline bool zap_drop_file_uffd_wp(struct zap_details *details) +static inline bool zap_drop_markers(struct zap_details *details) { if (!details) return false; @@ -1478,7 +1478,7 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma, if (vma_is_anonymous(vma)) return;
if (zap_drop_file_uffd_wp(details))
if (zap_drop_markers(details)) return; for (;;) {@@ -1673,7 +1673,15 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, * drop the marker if explicitly requested. */ if (!vma_is_anonymous(vma) &&
!zap_drop_file_uffd_wp(details))
!zap_drop_markers(details))continue;} else if (is_guard_swp_entry(entry)) {/** Ordinary zapping should not remove guard PTE* markers. Only do so if we should remove PTE markers* in general.*/if (!zap_drop_markers(details)) continue;
Just a comment: It's nice that the feature is restricted to anonymous VMAs, otherwise we'd have to figure out here what to do about unmap_mapping_folio() (which sets ZAP_FLAG_DROP_MARKER together with details.single_folio)...
} else if (is_hwpoison_entry(entry) || is_poisoned_swp_entry(entry)) {@@ -4005,6 +4013,10 @@ static vm_fault_t handle_pte_marker(struct vm_fault *vmf) if (marker & PTE_MARKER_POISONED) return VM_FAULT_HWPOISON;
/* Hitting a guard page is always a fatal condition. */if (marker & PTE_MARKER_GUARD)return VM_FAULT_SIGSEGV;if (pte_marker_entry_uffd_wp(entry)) return pte_marker_handle_uffd_wp(vmf);-- 2.46.2