On Mon, Jun 29, 2026 at 08:25:25PM +0100, Lorenzo Stoakes wrote: >The core do_mmap() function accepts a vm_flags_t parameter which it then >manipulates before passing to mmap_region() to do the heavy lifting of the >memory mapping. > >Update do_mmap() to instead accept a vma_flags_t parameter, and adjust all >the logic within do_mmap() to manipulate this instead. > >This is as part of the ongoing effort to convert VMA flags from a system >word size to a bitmap type which allows us to unrestrict the number of VMA >flags, as well as gain control over how VMA flag manipulation occurs. > >We do not cascade these changes to all functions which accept vm_flags_t, >but rather use vma_flags_to_legacy() where necessary, specifically >deferring converting calc_vm_prot_bits(), calc_vm_flag_bits() and >__get_unmapped_area() to vma_flags_t. > >Also utilise the new vma_flags_can_grow() predicate which correctly handles >the case of architectures without upward growing stacks. > >As part of this change, introduce VMA_SHADOW_STACK so we can correctly >handle the case of the shadow stack not being defined. > >No functional change intended. > >Signed-off-by: Lorenzo Stoakes <[email protected]> >---
Not exactly a small one :) I stared at this patch for a while, hopefully don't miss anythig ... Just one tiny nit below. Overall, LGTM, feel free to add: Reviewed-by: Lance Yang <[email protected]> [...] >diff --git a/mm/mmap.c b/mm/mmap.c >index 46174e706bbe..547352183214 100644 >--- a/mm/mmap.c >+++ b/mm/mmap.c [...] >@@ -488,23 +496,27 @@ unsigned long do_mmap(struct file *file, unsigned long >addr, > * Check to see if we are violating any seals and update VMA > * flags if necessary to avoid future seal violations. > */ >- err = memfd_check_seals_mmap(file, &vm_flags); >+ err = memfd_check_seals_mmap(file, &vma_flags); > if (err) > return (unsigned long)err; > } else { > switch (flags & MAP_TYPE) { > case MAP_SHARED: >- if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) >+ if (vma_flags_can_grow(&vma_flags)) > return -EINVAL; > /* > * Ignore pgoff. > */ > pgoff = 0; >- vm_flags |= VM_SHARED | VM_MAYSHARE; >+ vma_flags_set(&vma_flags, VMA_SHARED_BIT, >VMA_MAYSHARE_BIT); > break; >- case MAP_DROPPABLE: >- if (VM_DROPPABLE == VM_NONE) >+ case MAP_DROPPABLE: { >+ vma_flags_t droppable = VMA_DROPPABLE; >+ >+ if (vma_flags_empty(&droppable)) > return -EOPNOTSUPP; >+ vma_flags_set_mask(&vma_flags, droppable); >+ > /* > * A locked or stack area makes no sense to be > droppable. > * >@@ -515,23 +527,24 @@ unsigned long do_mmap(struct file *file, unsigned long >addr, > */ > if (flags & (MAP_LOCKED | MAP_HUGETLB)) > return -EINVAL; >- if (vm_flags & (VM_GROWSDOWN | VM_GROWSUP)) >+ if (vma_flags_can_grow(&vma_flags)) > return -EINVAL; > >- vm_flags |= VM_DROPPABLE; Old code checked VM_GROWSDOWN|VM_GROWSUP before seting VM_DROPPABLE. New code flips that around. Hmm, shouldn't master, just made me look twice ;) Maybe keep old order? Cheers, Lance >- > /* > * If the pages can be dropped, then it doesn't make > * sense to reserve them. > */ >- vm_flags |= VM_NORESERVE; >+ vma_flags_set(&vma_flags, VMA_NORESERVE_BIT); > > /* > * Likewise, they're volatile enough that they > * shouldn't survive forks or coredumps. > */ >- vm_flags |= VM_WIPEONFORK | VM_DONTDUMP; >+ vma_flags_set(&vma_flags, VMA_WIPEONFORK_BIT, >+ VMA_DONTDUMP_BIT); >+ > fallthrough; >+ } > case MAP_PRIVATE: > /* > * Set pgoff according to addr for anon_vma. [...]
