diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/mm.h | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index fea113d1d723..af2904aeb163 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -556,6 +556,32 @@ extern unsigned int kobjsize(const void *objp); #define VM_IGNORE_MERGE (VM_SOFTDIRTY | VM_STICKY) /* + * Flags which should result in page tables being copied on fork. These are + * flags which indicate that the VMA maps page tables which cannot be + * reconsistuted upon page fault, so necessitate page table copying upon + * + * 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_MAYBE_GUARD - Could contain page guard region markers which + * by design are a property of the page tables + * only and thus cannot be reconstructed on page + * fault. + */ +#define VM_COPY_ON_FORK (VM_PFNMAP | VM_MIXEDMAP | VM_UFFD_WP | VM_MAYBE_GUARD) + +/* * mapping from the currently active vm_flags protection bits (the * low four bits) to a page protection mask.. */ |