diff options
Diffstat (limited to 'mm/vma.c')
| -rw-r--r-- | mm/vma.c | 2068 |
1 files changed, 2068 insertions, 0 deletions
diff --git a/mm/vma.c b/mm/vma.c new file mode 100644 index 000000000000..4737afcb064c --- /dev/null +++ b/mm/vma.c @@ -0,0 +1,2068 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +/* + * VMA-specific functions. + */ + +#include "vma_internal.h" +#include "vma.h" + +static inline bool is_mergeable_vma(struct vma_merge_struct *vmg, bool merge_next) +{ + struct vm_area_struct *vma = merge_next ? vmg->next : vmg->prev; + + if (!mpol_equal(vmg->policy, vma_policy(vma))) + return false; + /* + * VM_SOFTDIRTY should not prevent from VMA merging, if we + * match the flags but dirty bit -- the caller should mark + * merged VMA as dirty. If dirty bit won't be excluded from + * comparison, we increase pressure on the memory system forcing + * the kernel to generate new VMAs when old one could be + * extended instead. + */ + if ((vma->vm_flags ^ vmg->flags) & ~VM_SOFTDIRTY) + return false; + if (vma->vm_file != vmg->file) + return false; + if (!is_mergeable_vm_userfaultfd_ctx(vma, vmg->uffd_ctx)) + return false; + if (!anon_vma_name_eq(anon_vma_name(vma), vmg->anon_name)) + return false; + return true; +} + +static inline bool is_mergeable_anon_vma(struct anon_vma *anon_vma1, + struct anon_vma *anon_vma2, struct vm_area_struct *vma) +{ + /* + * The list_is_singular() test is to avoid merging VMA cloned from + * parents. This can improve scalability caused by anon_vma lock. + */ + if ((!anon_vma1 || !anon_vma2) && (!vma || + list_is_singular(&vma->anon_vma_chain))) + return true; + return anon_vma1 == anon_vma2; +} + +/* Are the anon_vma's belonging to each VMA compatible with one another? */ +static inline bool are_anon_vmas_compatible(struct vm_area_struct *vma1, + struct vm_area_struct *vma2) +{ + return is_mergeable_anon_vma(vma1->anon_vma, vma2->anon_vma, NULL); +} + +/* + * init_multi_vma_prep() - Initializer for struct vma_prepare + * @vp: The vma_prepare struct + * @vma: The vma that will be altered once locked + * @next: The next vma if it is to be adjusted + * @remove: The first vma to be removed + * @remove2: The second vma to be removed + */ +static void init_multi_vma_prep(struct vma_prepare *vp, + struct vm_area_struct *vma, + struct vm_area_struct *next, + struct vm_area_struct *remove, + struct vm_area_struct *remove2) +{ + memset(vp, 0, sizeof(struct vma_prepare)); + vp->vma = vma; + vp->anon_vma = vma->anon_vma; + vp->remove = remove; + vp->remove2 = remove2; + vp->adj_next = next; + if (!vp->anon_vma && next) + vp->anon_vma = next->anon_vma; + + vp->file = vma->vm_file; + if (vp->file) + vp->mapping = vma->vm_file->f_mapping; + +} + +/* + * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff) + * in front of (at a lower virtual address and file offset than) the vma. + * + * We cannot merge two vmas if they have differently assigned (non-NULL) + * anon_vmas, nor if same anon_vma is assigned but offsets incompatible. + * + * We don't check here for the merged mmap wrapping around the end of pagecache + * indices (16TB on ia32) because do_mmap() does not permit mmap's which + * wrap, nor mmaps which cover the final page at index -1UL. + * + * We assume the vma may be removed as part of the merge. + */ +static bool can_vma_merge_before(struct vma_merge_struct *vmg) +{ + pgoff_t pglen = PHYS_PFN(vmg->end - vmg->start); + + if (is_mergeable_vma(vmg, /* merge_next = */ true) && + is_mergeable_anon_vma(vmg->anon_vma, vmg->next->anon_vma, vmg->next)) { + if (vmg->next->vm_pgoff == vmg->pgoff + pglen) + return true; + } + + return false; +} + +/* + * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff) + * beyond (at a higher virtual address and file offset than) the vma. + * + * We cannot merge two vmas if they have differently assigned (non-NULL) + * anon_vmas, nor if same anon_vma is assigned but offsets incompatible. + * + * We assume that vma is not removed as part of the merge. + */ +static bool can_vma_merge_after(struct vma_merge_struct *vmg) +{ + if (is_mergeable_vma(vmg, /* merge_next = */ false) && + is_mergeable_anon_vma(vmg->anon_vma, vmg->prev->anon_vma, vmg->prev)) { + if (vmg->prev->vm_pgoff + vma_pages(vmg->prev) == vmg->pgoff) + return true; + } + return false; +} + +static void __vma_link_file(struct vm_area_struct *vma, + struct address_space *mapping) +{ + if (vma_is_shared_maywrite(vma)) + mapping_allow_writable(mapping); + + flush_dcache_mmap_lock(mapping); + vma_interval_tree_insert(vma, &mapping->i_mmap); + flush_dcache_mmap_unlock(mapping); +} + +/* + * Requires inode->i_mapping->i_mmap_rwsem + */ +static void __remove_shared_vm_struct(struct vm_area_struct *vma, + struct address_space *mapping) +{ + if (vma_is_shared_maywrite(vma)) + mapping_unmap_writable(mapping); + + flush_dcache_mmap_lock(mapping); + vma_interval_tree_remove(vma, &mapping->i_mmap); + flush_dcache_mmap_unlock(mapping); +} + +/* + * vma_prepare() - Helper function for handling locking VMAs prior to altering + * @vp: The initialized vma_prepare struct + */ +static void vma_prepare(struct vma_prepare *vp) +{ + if (vp->file) { + uprobe_munmap(vp->vma, vp->vma->vm_start, vp->vma->vm_end); + + if (vp->adj_next) + uprobe_munmap(vp->adj_next, vp->adj_next->vm_start, + vp->adj_next->vm_end); + + i_mmap_lock_write(vp->mapping); + if (vp->insert && vp->insert->vm_file) { + /* + * Put into interval tree now, so instantiated pages + * are visible to arm/parisc __flush_dcache_page + * throughout; but we cannot insert into address + * space until vma start or end is updated. + */ + __vma_link_file(vp->insert, + vp->insert->vm_file->f_mapping); + } + } + + if (vp->anon_vma) { + anon_vma_lock_write(vp->anon_vma); + anon_vma_interval_tree_pre_update_vma(vp->vma); + if (vp->adj_next) + anon_vma_interval_tree_pre_update_vma(vp->adj_next); + } + + if (vp->file) { + flush_dcache_mmap_lock(vp->mapping); + vma_interval_tree_remove(vp->vma, &vp->mapping->i_mmap); + if (vp->adj_next) + vma_interval_tree_remove(vp->adj_next, + &vp->mapping->i_mmap); + } + +} + +/* + * vma_complete- Helper function for handling the unlocking after altering VMAs, + * or for inserting a VMA. + * + * @vp: The vma_prepare struct + * @vmi: The vma iterator + * @mm: The mm_struct + */ +static void vma_complete(struct vma_prepare *vp, struct vma_iterator *vmi, + struct mm_struct *mm) +{ + if (vp->file) { + if (vp->adj_next) + vma_interval_tree_insert(vp->adj_next, + &vp->mapping->i_mmap); + vma_interval_tree_insert(vp->vma, &vp->mapping->i_mmap); + flush_dcache_mmap_unlock(vp->mapping); + } + + if (vp->remove && vp->file) { + __remove_shared_vm_struct(vp->remove, vp->mapping); + if (vp->remove2) + __remove_shared_vm_struct(vp->remove2, vp->mapping); + } else if (vp->insert) { + /* + * split_vma has split insert from vma, and needs + * us to insert it before dropping the locks + * (it may either follow vma or precede it). + */ + vma_iter_store(vmi, vp->insert); + mm->map_count++; + } + + if (vp->anon_vma) { + anon_vma_interval_tree_post_update_vma(vp->vma); + if (vp->adj_next) + anon_vma_interval_tree_post_update_vma(vp->adj_next); + anon_vma_unlock_write(vp->anon_vma); + } + + if (vp->file) { + i_mmap_unlock_write(vp->mapping); + uprobe_mmap(vp->vma); + + if (vp->adj_next) + uprobe_mmap(vp->adj_next); + } + + if (vp->remove) { +again: + vma_mark_detached(vp->remove, true); + if (vp->file) { + uprobe_munmap(vp->remove, vp->remove->vm_start, + vp->remove->vm_end); + fput(vp->file); + } + if (vp->remove->anon_vma) + anon_vma_merge(vp->vma, vp->remove); + mm->map_count--; + mpol_put(vma_policy(vp->remove)); + if (!vp->remove2) + WARN_ON_ONCE(vp->vma->vm_end < vp->remove->vm_end); + vm_area_free(vp->remove); + + /* + * In mprotect's case 6 (see comments on vma_merge), + * we are removing both mid and next vmas + */ + if (vp->remove2) { + vp->remove = vp->remove2; + vp->remove2 = NULL; + goto again; + } + } + if (vp->insert && vp->file) + uprobe_mmap(vp->insert); +} + +/* + * init_vma_prep() - Initializer wrapper for vma_prepare struct + * @vp: The vma_prepare struct + * @vma: The vma that will be altered once locked + */ +static void init_vma_prep(struct vma_prepare *vp, struct vm_area_struct *vma) +{ + init_multi_vma_prep(vp, vma, NULL, NULL, NULL); +} + +/* + * Can the proposed VMA be merged with the left (previous) VMA taking into + * account the start position of the proposed range. + */ +static bool can_vma_merge_left(struct vma_merge_struct *vmg) + +{ + return vmg->prev && vmg->prev->vm_end == vmg->start && + can_vma_merge_after(vmg); +} + +/* + * Can the proposed VMA be merged with the right (next) VMA taking into + * account the end position of the proposed range. + * + * In addition, if we can merge with the left VMA, ensure that left and right + * anon_vma's are also compatible. + */ +static bool can_vma_merge_right(struct vma_merge_struct *vmg, + bool can_merge_left) +{ + if (!vmg->next || vmg->end != vmg->next->vm_start || + !can_vma_merge_before(vmg)) + return false; + + if (!can_merge_left) + return true; + + /* + * If we can merge with prev (left) and next (right), indicating that + * each VMA's anon_vma is compatible with the proposed anon_vma, this + * does not mean prev and next are compatible with EACH OTHER. + * + * We therefore check this in addition to mergeability to either side. + */ + return are_anon_vmas_compatible(vmg->prev, vmg->next); +} + +/* + * Close a vm structure and free it. + */ +void remove_vma(struct vm_area_struct *vma, bool unreachable, bool closed) +{ + might_sleep(); + if (!closed && vma->vm_ops && vma->vm_ops->close) + vma->vm_ops->close(vma); + if (vma->vm_file) + fput(vma->vm_file); + mpol_put(vma_policy(vma)); + if (unreachable) + __vm_area_free(vma); + else + vm_area_free(vma); +} + +/* + * Get rid of page table information in the indicated region. + * + * Called with the mm semaphore held. + */ +void unmap_region(struct ma_state *mas, struct vm_area_struct *vma, + struct vm_area_struct *prev, struct vm_area_struct *next) +{ + struct mm_struct *mm = vma->vm_mm; + struct mmu_gather tlb; + + lru_add_drain(); + tlb_gather_mmu(&tlb, mm); + update_hiwater_rss(mm); + unmap_vmas(&tlb, mas, vma, vma->vm_start, vma->vm_end, vma->vm_end, + /* mm_wr_locked = */ true); + mas_set(mas, vma->vm_end); + free_pgtables(&tlb, mas, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS, + next ? next->vm_start : USER_PGTABLES_CEILING, + /* mm_wr_locked = */ true); + tlb_finish_mmu(&tlb); +} + +/* + * __split_vma() bypasses sysctl_max_map_count checking. We use this where it + * has already been checked or doesn't make sense to fail. + * VMA Iterator will point to the original VMA. + */ +static int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, + unsigned long addr, int new_below) +{ + struct vma_prepare vp; + struct vm_area_struct *new; + int err; + + WARN_ON(vma->vm_start >= addr); + WARN_ON(vma->vm_end <= addr); + + if (vma->vm_ops && vma->vm_ops->may_split) { + err = vma->vm_ops->may_split(vma, addr); + if (err) + return err; + } + + new = vm_area_dup(vma); + if (!new) + return -ENOMEM; + + if (new_below) { + new->vm_end = addr; + } else { + new->vm_start = addr; + new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT); + } + + err = -ENOMEM; + vma_iter_config(vmi, new->vm_start, new->vm_end); + if (vma_iter_prealloc(vmi, new)) + goto out_free_vma; + + err = vma_dup_policy(vma, new); + if (err) + goto out_free_vmi; + + err = anon_vma_clone(new, vma); + if (err) + goto out_free_mpol; + + if (new->vm_file) + get_file(new->vm_file); + + if (new->vm_ops && new->vm_ops->open) + new->vm_ops->open(new); + + vma_start_write(vma); + vma_start_write(new); + + init_vma_prep(&vp, vma); + vp.insert = new; + vma_prepare(&vp); + vma_adjust_trans_huge(vma, vma->vm_start, addr, 0); + + if (new_below) { + vma->vm_start = addr; + vma->vm_pgoff += (addr - new->vm_start) >> PAGE_SHIFT; + } else { + vma->vm_end = addr; + } + + /* vma_complete stores the new vma */ + vma_complete(&vp, vmi, vma->vm_mm); + validate_mm(vma->vm_mm); + + /* Success. */ + if (new_below) + vma_next(vmi); + else + vma_prev(vmi); + + return 0; + +out_free_mpol: + mpol_put(vma_policy(new)); +out_free_vmi: + vma_iter_free(vmi); +out_free_vma: + vm_area_free(new); + return err; +} + +/* + * Split a vma into two pieces at address 'addr', a new vma is allocated + * either for the first part or the tail. + */ +static int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, + unsigned long addr, int new_below) +{ + if (vma->vm_mm->map_count >= sysctl_max_map_count) + return -ENOMEM; + + return __split_vma(vmi, vma, addr, new_below); +} + +/* + * vma has some anon_vma assigned, and is already inserted on that + * anon_vma's interval trees. + * + * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the + * vma must be removed from the anon_vma's interval trees using + * anon_vma_interval_tree_pre_update_vma(). + * + * After the update, the vma will be reinserted using + * anon_vma_interval_tree_post_update_vma(). + * + * The entire update must be protected by exclusive mmap_lock and by + * the root anon_vma's mutex. + */ +void +anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma) +{ + struct anon_vma_chain *avc; + + list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) + anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root); +} + +void +anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma) +{ + struct anon_vma_chain *avc; + + list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) + anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root); +} + +/* + * dup_anon_vma() - Helper function to duplicate anon_vma + * @dst: The destination VMA + * @src: The source VMA + * @dup: Pointer to the destination VMA when successful. + * + * Returns: 0 on success. + */ +static int dup_anon_vma(struct vm_area_struct *dst, + struct vm_area_struct *src, struct vm_area_struct **dup) +{ + /* + * Easily overlooked: when mprotect shifts the boundary, make sure the + * expanding vma has anon_vma set if the shrinking vma had, to cover any + * anon pages imported. + */ + if (src->anon_vma && !dst->anon_vma) { + int ret; + + vma_assert_write_locked(dst); + dst->anon_vma = src->anon_vma; + ret = anon_vma_clone(dst, src); + if (ret) + return ret; + + *dup = dst; + } + + return 0; +} + +#ifdef CONFIG_DEBUG_VM_MAPLE_TREE +void validate_mm(struct mm_struct *mm) +{ + int bug = 0; + int i = 0; + struct vm_area_struct *vma; + VMA_ITERATOR(vmi, mm, 0); + + mt_validate(&mm->mm_mt); + for_each_vma(vmi, vma) { +#ifdef CONFIG_DEBUG_VM_RB + struct anon_vma *anon_vma = vma->anon_vma; + struct anon_vma_chain *avc; +#endif + unsigned long vmi_start, vmi_end; + bool warn = 0; + + vmi_start = vma_iter_addr(&vmi); + vmi_end = vma_iter_end(&vmi); + if (VM_WARN_ON_ONCE_MM(vma->vm_end != vmi_end, mm)) + warn = 1; + + if (VM_WARN_ON_ONCE_MM(vma->vm_start != vmi_start, mm)) + warn = 1; + + if (warn) { + pr_emerg("issue in %s\n", current->comm); + dump_stack(); + dump_vma(vma); + pr_emerg("tree range: %px start %lx end %lx\n", vma, + vmi_start, vmi_end - 1); + vma_iter_dump_tree(&vmi); + } + +#ifdef CONFIG_DEBUG_VM_RB + if (anon_vma) { + anon_vma_lock_read(anon_vma); + list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) + anon_vma_interval_tree_verify(avc); + anon_vma_unlock_read(anon_vma); + } +#endif + i++; + } + if (i != mm->map_count) { + pr_emerg("map_count %d vma iterator %d\n", mm->map_count, i); + bug = 1; + } + VM_BUG_ON_MM(bug, mm); +} +#endif /* CONFIG_DEBUG_VM_MAPLE_TREE */ + +/* Actually perform the VMA merge operation. */ +static int commit_merge(struct vma_merge_struct *vmg, + struct vm_area_struct *adjust, + struct vm_area_struct *remove, + struct vm_area_struct *remove2, + long adj_start, + bool expanded) +{ + struct vma_prepare vp; + + init_multi_vma_prep(&vp, vmg->vma, adjust, remove, remove2); + + VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma && + vp.anon_vma != adjust->anon_vma); + + if (expanded) { + /* Note: vma iterator must be pointing to 'start'. */ + vma_iter_config(vmg->vmi, vmg->start, vmg->end); + } else { + vma_iter_config(vmg->vmi, adjust->vm_start + adj_start, + adjust->vm_end); + } + + if (vma_iter_prealloc(vmg->vmi, vmg->vma)) + return -ENOMEM; + + vma_prepare(&vp); + vma_adjust_trans_huge(vmg->vma, vmg->start, vmg->end, adj_start); + vma_set_range(vmg->vma, vmg->start, vmg->end, vmg->pgoff); + + if (expanded) + vma_iter_store(vmg->vmi, vmg->vma); + + if (adj_start) { + adjust->vm_start += adj_start; + adjust->vm_pgoff += PHYS_PFN(adj_start); + if (adj_start < 0) { + WARN_ON(expanded); + vma_iter_store(vmg->vmi, adjust); + } + } + + vma_complete(&vp, vmg->vmi, vmg->vma->vm_mm); + + return 0; +} + +/* We can only remove VMAs when merging if they do not have a close hook. */ +static bool can_merge_remove_vma(struct vm_area_struct *vma) +{ + return !vma->vm_ops || !vma->vm_ops->close; +} + +/* + * vma_merge_existing_range - Attempt to merge VMAs based on a VMA having its + * attributes modified. + * + * @vmg: Describes the modifications being made to a VMA and associated + * metadata. + * + * When the attributes of a range within a VMA change, then it might be possible + * for immediately adjacent VMAs to be merged into that VMA due to having + * identical properties. + * + * This function checks for the existence of any such mergeable VMAs and updates + * the maple tree describing the @vmg->vma->vm_mm address space to account for + * this, as well as any VMAs shrunk/expanded/deleted as a result of this merge. + * + * As part of this operation, if a merge occurs, the @vmg object will have its + * vma, start, end, and pgoff fields modified to execute the merge. Subsequent + * calls to this function should reset these fields. + * + * Returns: The merged VMA if merge succeeds, or NULL otherwise. + * + * ASSUMPTIONS: + * - The caller must assign the VMA to be modifed to @vmg->vma. + * - The caller must have set @vmg->prev to the previous VMA, if there is one. + * - The caller must not set @vmg->next, as we determine this. + * - The caller must hold a WRITE lock on the mm_struct->mmap_lock. + * - vmi must be positioned within [@vmg->vma->vm_start, @vmg->vma->vm_end). + */ +static struct vm_area_struct *vma_merge_existing_range(struct vma_merge_struct *vmg) +{ + struct vm_area_struct *vma = vmg->vma; + struct vm_area_struct *prev = vmg->prev; + struct vm_area_struct *next, *res; + struct vm_area_struct *anon_dup = NULL; + struct vm_area_struct *adjust = NULL; + unsigned long start = vmg->start; + unsigned long end = vmg->end; + bool left_side = vma && start == vma->vm_start; + bool right_side = vma && end == vma->vm_end; + int err = 0; + long adj_start = 0; + bool merge_will_delete_vma, merge_will_delete_next; + bool merge_left, merge_right, merge_both; + bool expanded; + + mmap_assert_write_locked(vmg->mm); + VM_WARN_ON(!vma); /* We are modifying a VMA, so caller must specify. */ + VM_WARN_ON(vmg->next); /* We set this. */ + VM_WARN_ON(prev && start <= prev->vm_start); + VM_WARN_ON(start >= end); + /* + * If vma == prev, then we are offset into a VMA. Otherwise, if we are + * not, we must span a portion of the VMA. + */ + VM_WARN_ON(vma && ((vma != prev && vmg->start != vma->vm_start) || + vmg->end > vma->vm_end)); + /* The vmi must be positioned within vmg->vma. */ + VM_WARN_ON(vma && !(vma_iter_addr(vmg->vmi) >= vma->vm_start && + vma_iter_addr(vmg->vmi) < vma->vm_end)); + + vmg->state = VMA_MERGE_NOMERGE; + + /* + * If a special mapping or if the range being modified is neither at the + * furthermost left or right side of the VMA, then we have no chance of + * merging and should abort. + */ + if (vmg->flags & VM_SPECIAL || (!left_side && !right_side)) + return NULL; + + if (left_side) + merge_left = can_vma_merge_left(vmg); + else + merge_left = false; + + if (right_side) { + next = vmg->next = vma_iter_next_range(vmg->vmi); + vma_iter_prev_range(vmg->vmi); + + merge_right = can_vma_merge_right(vmg, merge_left); + } else { + merge_right = false; + next = NULL; + } + + if (merge_left) /* If merging prev, position iterator there. */ + vma_prev(vmg->vmi); + else if (!merge_right) /* If we have nothing to merge, abort. */ + return NULL; + + merge_both = merge_left && merge_right; + /* If we span the entire VMA, a merge implies it will be deleted. */ + merge_will_delete_vma = left_side && right_side; + + /* + * If we need to remove vma in its entirety but are unable to do so, + * we have no sensible recourse but to abort the merge. + */ + if (merge_will_delete_vma && !can_merge_remove_vma(vma)) + return NULL; + + /* + * If we merge both VMAs, then next is also deleted. This implies + * merge_will_delete_vma also. + */ + merge_will_delete_next = merge_both; + + /* + * If we cannot delete next, then we can reduce the operation to merging + * prev and vma (thereby deleting vma). + */ + if (merge_will_delete_next && !can_merge_remove_vma(next)) { + merge_will_delete_next = false; + merge_right = false; + merge_both = false; + } + + /* No matter what happens, we will be adjusting vma. */ + vma_start_write(vma); + + if (merge_left) + vma_start_write(prev); + + if (merge_right) + vma_start_write(next); + + if (merge_both) { + /* + * |<----->| + * |-------*********-------| + * prev vma next + * extend delete delete + */ + + vmg->vma = prev; + vmg->start = prev->vm_start; + vmg->end = next->vm_end; + vmg->pgoff = prev->vm_pgoff; + + /* + * We already ensured anon_vma compatibility above, so now it's + * simply a case of, if prev has no anon_vma object, which of + * next or vma contains the anon_vma we must duplicate. + */ + err = dup_anon_vma(prev, next->anon_vma ? next : vma, &anon_dup); + } else if (merge_left) { + /* + * |<----->| OR + * |<--------->| + * |-------************* + * prev vma + * extend shrink/delete + */ + + vmg->vma = prev; + vmg->start = prev->vm_start; + vmg->pgoff = prev->vm_pgoff; + + if (!merge_will_delete_vma) { + adjust = vma; + adj_start = vmg->end - vma->vm_start; + } + + err = dup_anon_vma(prev, vma, &anon_dup); + } else { /* merge_right */ + /* + * |<----->| OR + * |<--------->| + * *************-------| + * vma next + * shrink/delete extend + */ + + pgoff_t pglen = PHYS_PFN(vmg->end - vmg->start); + + VM_WARN_ON(!merge_right); + /* If we are offset into a VMA, then prev must be vma. */ + VM_WARN_ON(vmg->start > vma->vm_start && prev && vma != prev); + + if (merge_will_delete_vma) { + vmg->vma = next; + vmg->end = next->vm_end; + vmg->pgoff = next->vm_pgoff - pglen; + } else { + /* + * We shrink vma and expand next. + * + * IMPORTANT: This is the ONLY case where the final + * merged VMA is NOT vmg->vma, but rather vmg->next. + */ + + vmg->start = vma->vm_start; + vmg->end = start; + vmg->pgoff = vma->vm_pgoff; + + adjust = next; + adj_start = -(vma->vm_end - start); + } + + err = dup_anon_vma(next, vma, &anon_dup); + } + + if (err) + goto abort; + + /* + * In nearly all cases, we expand vmg->vma. There is one exception - + * merge_right where we partially span the VMA. In this case we shrink + * the end of vmg->vma and adjust the start of vmg->next accordingly. + */ + expanded = !merge_right || merge_will_delete_vma; + + if (commit_merge(vmg, adjust, + merge_will_delete_vma ? vma : NULL, + merge_will_delete_next ? next : NULL, + adj_start, expanded)) { + if (anon_dup) + unlink_anon_vmas(anon_dup); + + vmg->state = VMA_MERGE_ERROR_NOMEM; + return NULL; + } + + res = merge_left ? prev : next; + khugepaged_enter_vma(res, vmg->flags); + + vmg->state = VMA_MERGE_SUCCESS; + return res; + +abort: + vma_iter_set(vmg->vmi, start); + vma_iter_load(vmg->vmi); + vmg->state = VMA_MERGE_ERROR_NOMEM; + return NULL; +} + +/* + * vma_merge_new_range - Attempt to merge a new VMA into address space + * + * @vmg: Describes the VMA we are adding, in the range @vmg->start to @vmg->end + * (exclusive), which we try to merge with any adjacent VMAs if possible. + * + * We are about to add a VMA to the address space starting at @vmg->start and + * ending at @vmg->end. There are three different possible scenarios: + * + * 1. There is a VMA with identical properties immediately adjacent to the + * proposed new VMA [@vmg->start, @vmg->end) either before or after it - + * EXPAND that VMA: + * + * Proposed: |-----| or |-----| + * Existing: |----| |----| + * + * 2. There are VMAs with identical properties immediately adjacent to the + * proposed new VMA [@vmg->start, @vmg->end) both before AND after it - + * EXPAND the former and REMOVE the latter: + * + * Proposed: |-----| + * Existing: |----| |----| + * + * 3. There are no VMAs immediately adjacent to the proposed new VMA or those + * VMAs do not have identical attributes - NO MERGE POSSIBLE. + * + * In instances where we can merge, this function returns the expanded VMA which + * will have its range adjusted accordingly and the underlying maple tree also + * adjusted. + * + * Returns: In instances where no merge was possible, NULL. Otherwise, a pointer + * to the VMA we expanded. + * + * This function adjusts @vmg to provide @vmg->next if not already specified, + * and adjusts [@vmg->start, @vmg->end) to span the expanded range. + * + * ASSUMPTIONS: + * - The caller must hold a WRITE lock on the mm_struct->mmap_lock. + * - The caller must have determined that [@vmg->start, @vmg->end) is empty, + other than VMAs that will be unmapped should the operation succeed. + * - The caller must have specified the previous vma in @vmg->prev. + * - The caller must have specified the next vma in @vmg->next. + * - The caller must have positioned the vmi at or before the gap. + */ +struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg) +{ + struct vm_area_struct *prev = vmg->prev; + struct vm_area_struct *next = vmg->next; + unsigned long start = vmg->start; + unsigned long end = vmg->end; + pgoff_t pgoff = vmg->pgoff; + pgoff_t pglen = PHYS_PFN(end - start); + bool can_merge_left, can_merge_right; + + mmap_assert_write_locked(vmg->mm); + VM_WARN_ON(vmg->vma); + /* vmi must point at or before the gap. */ + VM_WARN_ON(vma_iter_addr(vmg->vmi) > end); + + vmg->state = VMA_MERGE_NOMERGE; + + /* Special VMAs are unmergeable, also if no prev/next. */ + if ((vmg->flags & VM_SPECIAL) || (!prev && !next)) + return NULL; + + can_merge_left = can_vma_merge_left(vmg); + can_merge_right = can_vma_merge_right(vmg, can_merge_left); + + /* If we can merge with the next VMA, adjust vmg accordingly. */ + if (can_merge_right) { + vmg->end = next->vm_end; + vmg->vma = next; + vmg->pgoff = next->vm_pgoff - pglen; + } + + /* If we can merge with the previous VMA, adjust vmg accordingly. */ + if (can_merge_left) { + vmg->start = prev->vm_start; + vmg->vma = prev; + vmg->pgoff = prev->vm_pgoff; + + /* + * If this merge would result in removal of the next VMA but we + * are not permitted to do so, reduce the operation to merging + * prev and vma. + */ + if (can_merge_right && !can_merge_remove_vma(next)) + vmg->end = end; + + vma_prev(vmg->vmi); /* Equivalent to going to the previous range */ + } + + /* + * Now try to expand adjacent VMA(s). This takes care of removing the + * following VMA if we have VMAs on both sides. + */ + if (vmg->vma && !vma_expand(vmg)) { + khugepaged_enter_vma(vmg->vma, vmg->flags); + vmg->state = VMA_MERGE_SUCCESS; + return vmg->vma; + } + + /* If expansion failed, reset state. Allows us to retry merge later. */ + vmg->vma = NULL; + vmg->start = start; + vmg->end = end; + vmg->pgoff = pgoff; + if (vmg->vma == prev) + vma_iter_set(vmg->vmi, start); + + return NULL; +} + +/* + * vma_expand - Expand an existing VMA + * + * @vmg: Describes a VMA expansion operation. + * + * Expand @vma to vmg->start and vmg->end. Can expand off the start and end. + * Will expand over vmg->next if it's different from vmg->vma and vmg->end == + * vmg->next->vm_end. Checking if the vmg->vma can expand and merge with + * vmg->next needs to be handled by the caller. + * + * Returns: 0 on success. + * + * ASSUMPTIONS: + * - The caller must hold a WRITE lock on vmg->vma->mm->mmap_lock. + * - The caller must have set @vmg->vma and @vmg->next. + */ +int vma_expand(struct vma_merge_struct *vmg) +{ + struct vm_area_struct *anon_dup = NULL; + bool remove_next = false; + struct vm_area_struct *vma = vmg->vma; + struct vm_area_struct *next = vmg->next; + + mmap_assert_write_locked(vmg->mm); + + vma_start_write(vma); + if (next && (vma != next) && (vmg->end == next->vm_end)) { + int ret; + + remove_next = true; + /* This should already have been checked by this point. */ + VM_WARN_ON(!can_merge_remove_vma(next)); + vma_start_write(next); + ret = dup_anon_vma(vma, next, &anon_dup); + if (ret) + return ret; + } + + /* Not merging but overwriting any part of next is not handled. */ + VM_WARN_ON(next && !remove_next && + next != vma && vmg->end > next->vm_start); + /* Only handles expanding */ + VM_WARN_ON(vma->vm_start < vmg->start || vma->vm_end > vmg->end); + + if (commit_merge(vmg, NULL, remove_next ? next : NULL, NULL, 0, true)) + goto nomem; + + return 0; + +nomem: + vmg->state = VMA_MERGE_ERROR_NOMEM; + if (anon_dup) + unlink_anon_vmas(anon_dup); + return -ENOMEM; +} + +/* + * vma_shrink() - Reduce an existing VMAs memory area + * @vmi: The vma iterator + * @vma: The VMA to modify + * @start: The new start + * @end: The new end + * + * Returns: 0 on success, -ENOMEM otherwise + */ +int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma, + unsigned long start, unsigned long end, pgoff_t pgoff) +{ + struct vma_prepare vp; + + WARN_ON((vma->vm_start != start) && (vma->vm_end != end)); + + if (vma->vm_start < start) + vma_iter_config(vmi, vma->vm_start, start); + else + vma_iter_config(vmi, end, vma->vm_end); + + if (vma_iter_prealloc(vmi, NULL)) + return -ENOMEM; + + vma_start_write(vma); + + init_vma_prep(&vp, vma); + vma_prepare(&vp); + vma_adjust_trans_huge(vma, start, end, 0); + + vma_iter_clear(vmi); + vma_set_range(vma, start, end, pgoff); + vma_complete(&vp, vmi, vma->vm_mm); + validate_mm(vma->vm_mm); + return 0; +} + +static inline void vms_clear_ptes(struct vma_munmap_struct *vms, + struct ma_state *mas_detach, bool mm_wr_locked) +{ + struct mmu_gather tlb; + + if (!vms->clear_ptes) /* Nothing to do */ + return; + + /* + * We can free page tables without write-locking mmap_lock because VMAs + * were isolated before we downgraded mmap_lock. + */ + mas_set(mas_detach, 1); + lru_add_drain(); + tlb_gather_mmu(&tlb, vms->vma->vm_mm); + update_hiwater_rss(vms->vma->vm_mm); + unmap_vmas(&tlb, mas_detach, vms->vma, vms->start, vms->end, + vms->vma_count, mm_wr_locked); + + mas_set(mas_detach, 1); + /* start and end may be different if there is no prev or next vma. */ + free_pgtables(&tlb, mas_detach, vms->vma, vms->unmap_start, + vms->unmap_end, mm_wr_locked); + tlb_finish_mmu(&tlb); + vms->clear_ptes = false; +} + +void vms_clean_up_area(struct vma_munmap_struct *vms, + struct ma_state *mas_detach) +{ + struct vm_area_struct *vma; + + if (!vms->nr_pages) + return; + + vms_clear_ptes(vms, mas_detach, true); + mas_set(mas_detach, 0); + mas_for_each(mas_detach, vma, ULONG_MAX) + if (vma->vm_ops && vma->vm_ops->close) + vma->vm_ops->close(vma); + vms->closed_vm_ops = true; +} + +/* + * vms_complete_munmap_vmas() - Finish the munmap() operation + * @vms: The vma munmap struct + * @mas_detach: The maple state of the detached vmas + * + * This updates the mm_struct, unmaps the region, frees the resources + * used for the munmap() and may downgrade the lock - if requested. Everything + * needed to be done once the vma maple tree is updated. + */ +void vms_complete_munmap_vmas(struct vma_munmap_struct *vms, + struct ma_state *mas_detach) +{ + struct vm_area_struct *vma; + struct mm_struct *mm; + + mm = current->mm; + mm->map_count -= vms->vma_count; + mm->locked_vm -= vms->locked_vm; + if (vms->unlock) + mmap_write_downgrade(mm); + + if (!vms->nr_pages) + return; + + vms_clear_ptes(vms, mas_detach, !vms->unlock); + /* Update high watermark before we lower total_vm */ + update_hiwater_vm(mm); + /* Stat accounting */ + WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm) - vms->nr_pages); + /* Paranoid bookkeeping */ + VM_WARN_ON(vms->exec_vm > mm->exec_vm); + VM_WARN_ON(vms->stack_vm > mm->stack_vm); + VM_WARN_ON(vms->data_vm > mm->data_vm); + mm->exec_vm -= vms->exec_vm; + mm->stack_vm -= vms->stack_vm; + mm->data_vm -= vms->data_vm; + + /* Remove and clean up vmas */ + mas_set(mas_detach, 0); + mas_for_each(mas_detach, vma, ULONG_MAX) + remove_vma(vma, /* = */ false, vms->closed_vm_ops); + + vm_unacct_memory(vms->nr_accounted); + validate_mm(mm); + if (vms->unlock) + mmap_read_unlock(mm); + + __mt_destroy(mas_detach->tree); +} + +/* + * vms_gather_munmap_vmas() - Put all VMAs within a range into a maple tree + * for removal at a later date. Handles splitting first and last if necessary + * and marking the vmas as isolated. + * + * @vms: The vma munmap struct + * @mas_detach: The maple state tracking the detached tree + * + * Return: 0 on success, error otherwise + */ +int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, + struct ma_state *mas_detach) +{ + struct vm_area_struct *next = NULL; + int error; + + /* + * If we need to split any vma, do it now to save pain later. + * Does it split the first one? + */ + if (vms->start > vms->vma->vm_start) { + + /* + * Make sure that map_count on return from munmap() will + * not exceed its limit; but let map_count go just above + * its limit temporarily, to help free resources as expected. + */ + if (vms->end < vms->vma->vm_end && + vms->vma->vm_mm->map_count >= sysctl_max_map_count) { + error = -ENOMEM; + goto map_count_exceeded; + } + + /* Don't bother splitting the VMA if we can't unmap it anyway */ + if (!can_modify_vma(vms->vma)) { + error = -EPERM; + goto start_split_failed; + } + + error = __split_vma(vms->vmi, vms->vma, vms->start, 1); + if (error) + goto start_split_failed; + } + vms->prev = vma_prev(vms->vmi); + if (vms->prev) + vms->unmap_start = vms->prev->vm_end; + + /* + * Detach a range of VMAs from the mm. Using next as a temp variable as + * it is always overwritten. + */ + for_each_vma_range(*(vms->vmi), next, vms->end) { + long nrpages; + + if (!can_modify_vma(next)) { + error = -EPERM; + goto modify_vma_failed; + } + /* Does it split the end? */ + if (next->vm_end > vms->end) { + error = __split_vma(vms->vmi, next, vms->end, 0); + if (error) + goto end_split_failed; + } + vma_start_write(next); + mas_set(mas_detach, vms->vma_count++); + error = mas_store_gfp(mas_detach, next, GFP_KERNEL); + if (error) + goto munmap_gather_failed; + + vma_mark_detached(next, true); + nrpages = vma_pages(next); + + vms->nr_pages += nrpages; + if (next->vm_flags & VM_LOCKED) + vms->locked_vm += nrpages; + + if (next->vm_flags & VM_ACCOUNT) + vms->nr_accounted += nrpages; + + if (is_exec_mapping(next->vm_flags)) + vms->exec_vm += nrpages; + else if (is_stack_mapping(next->vm_flags)) + vms->stack_vm += nrpages; + else if (is_data_mapping(next->vm_flags)) + vms->data_vm += nrpages; + + if (unlikely(vms->uf)) { + /* + * If userfaultfd_unmap_prep returns an error the vmas + * will remain split, but userland will get a + * highly unexpected error anyway. This is no + * different than the case where the first of the two + * __split_vma fails, but we don't undo the first + * split, despite we could. This is unlikely enough + * failure that it's not worth optimizing it for. + */ + error = userfaultfd_unmap_prep(next, vms->start, + vms->end, vms->uf); + if (error) + goto userfaultfd_error; + } +#ifdef CONFIG_DEBUG_VM_MAPLE_TREE + BUG_ON(next->vm_start < vms->start); + BUG_ON(next->vm_start > vms->end); +#endif + } + + vms->next = vma_next(vms->vmi); + if (vms->next) + vms->unmap_end = vms->next->vm_start; + +#if defined(CONFIG_DEBUG_VM_MAPLE_TREE) + /* Make sure no VMAs are about to be lost. */ + { + MA_STATE(test, mas_detach->tree, 0, 0); + struct vm_area_struct *vma_mas, *vma_test; + int test_count = 0; + + vma_iter_set(vms->vmi, vms->start); + rcu_read_lock(); + vma_test = mas_find(&test, vms->vma_count - 1); + for_each_vma_range(*(vms->vmi), vma_mas, vms->end) { + BUG_ON(vma_mas != vma_test); + test_count++; + vma_test = mas_next(&test, vms->vma_count - 1); + } + rcu_read_unlock(); + BUG_ON(vms->vma_count != test_count); + } +#endif + + while (vma_iter_addr(vms->vmi) > vms->start) + vma_iter_prev_range(vms->vmi); + + vms->clear_ptes = true; + return 0; + +userfaultfd_error: +munmap_gather_failed: +end_split_failed: +modify_vma_failed: + reattach_vmas(mas_detach); +start_split_failed: +map_count_exceeded: + return error; +} + +/* + * do_vmi_align_munmap() - munmap the aligned region from @start to @end. + * @vmi: The vma iterator + * @vma: The starting vm_area_struct + * @mm: The mm_struct + * @start: The aligned start address to munmap. + * @end: The aligned end address to munmap. + * @uf: The userfaultfd list_head + * @unlock: Set to true to drop the mmap_lock. unlocking only happens on + * success. + * + * Return: 0 on success and drops the lock if so directed, error and leaves the + * lock held otherwise. + */ +int do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, + struct mm_struct *mm, unsigned long start, unsigned long end, + struct list_head *uf, bool unlock) +{ + struct maple_tree mt_detach; + MA_STATE(mas_detach, &mt_detach, 0, 0); + mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK); + mt_on_stack(mt_detach); + struct vma_munmap_struct vms; + int error; + + init_vma_munmap(&vms, vmi, vma, start, end, uf, unlock); + error = vms_gather_munmap_vmas(&vms, &mas_detach); + if (error) + goto gather_failed; + + error = vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL); + if (error) + goto clear_tree_failed; + + /* Point of no return */ + vms_complete_munmap_vmas(&vms, &mas_detach); + return 0; + +clear_tree_failed: + reattach_vmas(&mas_detach); +gather_failed: + validate_mm(mm); + return error; +} + +/* + * do_vmi_munmap() - munmap a given range. + * @vmi: The vma iterator + * @mm: The mm_struct + * @start: The start address to munmap + * @len: The length of the range to munmap + * @uf: The userfaultfd list_head + * @unlock: set to true if the user wants to drop the mmap_lock on success + * + * This function takes a @mas that is either pointing to the previous VMA or set + * to MA_START and sets it up to remove the mapping(s). The @len will be + * aligned. + * + * Return: 0 on success and drops the lock if so directed, error and leaves the + * lock held otherwise. + */ +int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm, + unsigned long start, size_t len, struct list_head *uf, + bool unlock) +{ + unsigned long end; + struct vm_area_struct *vma; + + if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start) + return -EINVAL; + + end = start + PAGE_ALIGN(len); + if (end == start) + return -EINVAL; + + /* Find the first overlapping VMA */ + vma = vma_find(vmi, end); + if (!vma) { + if (unlock) + mmap_write_unlock(mm); + return 0; + } + + return do_vmi_align_munmap(vmi, vma, mm, start, end, uf, unlock); +} + +/* + * We are about to modify one or multiple of a VMA's flags, policy, userfaultfd + * context and anonymous VMA name within the range [start, end). + * + * As a result, we might be able to merge the newly modified VMA range with an + * adjacent VMA with identical properties. + * + * If no merge is possible and the range does not span the entirety of the VMA, + * we then need to split the VMA to accommodate the change. + * + * The function returns either the merged VMA, the original VMA if a split was + * required instead, or an error if the split failed. + */ +static struct vm_area_struct *vma_modify(struct vma_merge_struct *vmg) +{ + struct vm_area_struct *vma = vmg->vma; + struct vm_area_struct *merged; + + /* First, try to merge. */ + merged = vma_merge_existing_range(vmg); + if (merged) + return merged; + + /* Split any preceding portion of the VMA. */ + if (vma->vm_start < vmg->start) { + int err = split_vma(vmg->vmi, vma, vmg->start, 1); + + if (err) + return ERR_PTR(err); + } + + /* Split any trailing portion of the VMA. */ + if (vma->vm_end > vmg->end) { + int err = split_vma(vmg->vmi, vma, vmg->end, 0); + + if (err) + return ERR_PTR(err); + } + + return vma; +} + +struct vm_area_struct *vma_modify_flags( + struct vma_iterator *vmi, struct vm_area_struct *prev, + struct vm_area_struct *vma, unsigned long start, unsigned long end, + unsigned long new_flags) +{ + VMG_VMA_STATE(vmg, vmi, prev, vma, start, end); + + vmg.flags = new_flags; + + return vma_modify(&vmg); +} + +struct vm_area_struct +*vma_modify_flags_name(struct vma_iterator *vmi, + struct vm_area_struct *prev, + struct vm_area_struct *vma, + unsigned long start, + unsigned long end, + unsigned long new_flags, + struct anon_vma_name *new_name) +{ + VMG_VMA_STATE(vmg, vmi, prev, vma, start, end); + + vmg.flags = new_flags; + vmg.anon_name = new_name; + + return vma_modify(&vmg); +} + +struct vm_area_struct +*vma_modify_policy(struct vma_iterator *vmi, + struct vm_area_struct *prev, + struct vm_area_struct *vma, + unsigned long start, unsigned long end, + struct mempolicy *new_pol) +{ + VMG_VMA_STATE(vmg, vmi, prev, vma, start, end); + + vmg.policy = new_pol; + + return vma_modify(&vmg); +} + +struct vm_area_struct +*vma_modify_flags_uffd(struct vma_iterator *vmi, + struct vm_area_struct *prev, + struct vm_area_struct *vma, + unsigned long start, unsigned long end, + unsigned long new_flags, + struct vm_userfaultfd_ctx new_ctx) +{ + VMG_VMA_STATE(vmg, vmi, prev, vma, start, end); + + vmg.flags = new_flags; + vmg.uffd_ctx = new_ctx; + + return vma_modify(&vmg); +} + +/* + * Expand vma by delta bytes, potentially merging with an immediately adjacent + * VMA with identical properties. + */ +struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi, + struct vm_area_struct *vma, + unsigned long delta) +{ + VMG_VMA_STATE(vmg, vmi, vma, vma, vma->vm_end, vma->vm_end + delta); + + vmg.next = vma_iter_next_rewind(vmi, NULL); + vmg.vma = NULL; /* We use the VMA to populate VMG fields only. */ + + return vma_merge_new_range(&vmg); +} + +void unlink_file_vma_batch_init(struct unlink_vma_file_batch *vb) +{ + vb->count = 0; +} + +static void unlink_file_vma_batch_process(struct unlink_vma_file_batch *vb) +{ + struct address_space *mapping; + int i; + + mapping = vb->vmas[0]->vm_file->f_mapping; + i_mmap_lock_write(mapping); + for (i = 0; i < vb->count; i++) { + VM_WARN_ON_ONCE(vb->vmas[i]->vm_file->f_mapping != mapping); + __remove_shared_vm_struct(vb->vmas[i], mapping); + } + i_mmap_unlock_write(mapping); + + unlink_file_vma_batch_init(vb); +} + +void unlink_file_vma_batch_add(struct unlink_vma_file_batch *vb, + struct vm_area_struct *vma) +{ + if (vma->vm_file == NULL) + return; + + if ((vb->count > 0 && vb->vmas[0]->vm_file != vma->vm_file) || + vb->count == ARRAY_SIZE(vb->vmas)) + unlink_file_vma_batch_process(vb); + + vb->vmas[vb->count] = vma; + vb->count++; +} + +void unlink_file_vma_batch_final(struct unlink_vma_file_batch *vb) +{ + if (vb->count > 0) + unlink_file_vma_batch_process(vb); +} + +/* + * Unlink a file-based vm structure from its interval tree, to hide + * vma from rmap and vmtruncate before freeing its page tables. + */ +void unlink_file_vma(struct vm_area_struct *vma) +{ + struct file *file = vma->vm_file; + + if (file) { + struct address_space *mapping = file->f_mapping; + + i_mmap_lock_write(mapping); + __remove_shared_vm_struct(vma, mapping); + i_mmap_unlock_write(mapping); + } +} + +void vma_link_file(struct vm_area_struct *vma) +{ + struct file *file = vma->vm_file; + struct address_space *mapping; + + if (file) { + mapping = file->f_mapping; + i_mmap_lock_write(mapping); + __vma_link_file(vma, mapping); + i_mmap_unlock_write(mapping); + } +} + +int vma_link(struct mm_struct *mm, struct vm_area_struct *vma) +{ + VMA_ITERATOR(vmi, mm, 0); + + vma_iter_config(&vmi, vma->vm_start, vma->vm_end); + if (vma_iter_prealloc(&vmi, vma)) + return -ENOMEM; + + vma_start_write(vma); + vma_iter_store(&vmi, vma); + vma_link_file(vma); + mm->map_count++; + validate_mm(mm); + return 0; +} + +/* + * Copy the vma structure to a new location in the same mm, + * prior to moving page table entries, to effect an mremap move. + */ +struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, + unsigned long addr, unsigned long len, pgoff_t pgoff, + bool *need_rmap_locks) +{ + struct vm_area_struct *vma = *vmap; + unsigned long vma_start = vma->vm_start; + struct mm_struct *mm = vma->vm_mm; + struct vm_area_struct *new_vma; + bool faulted_in_anon_vma = true; + VMA_ITERATOR(vmi, mm, addr); + VMG_VMA_STATE(vmg, &vmi, NULL, vma, addr, addr + len); + + /* + * If anonymous vma has not yet been faulted, update new pgoff + * to match new location, to increase its chance of merging. + */ + if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) { + pgoff = addr >> PAGE_SHIFT; + faulted_in_anon_vma = false; + } + + new_vma = find_vma_prev(mm, addr, &vmg.prev); + if (new_vma && new_vma->vm_start < addr + len) + return NULL; /* should never get here */ + + vmg.vma = NULL; /* New VMA range. */ + vmg.pgoff = pgoff; + vmg.next = vma_iter_next_rewind(&vmi, NULL); + new_vma = vma_merge_new_range(&vmg); + + if (new_vma) { + /* + * Source vma may have been merged into new_vma + */ + if (unlikely(vma_start >= new_vma->vm_start && + vma_start < new_vma->vm_end)) { + /* + * The only way we can get a vma_merge with + * self during an mremap is if the vma hasn't + * been faulted in yet and we were allowed to + * reset the dst vma->vm_pgoff to the + * destination address of the mremap to allow + * the merge to happen. mremap must change the + * vm_pgoff linearity between src and dst vmas + * (in turn preventing a vma_merge) to be + * safe. It is only safe to keep the vm_pgoff + * linear if there are no pages mapped yet. + */ + VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma); + *vmap = vma = new_vma; + } + *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff); + } else { + new_vma = vm_area_dup(vma); + if (!new_vma) + goto out; + vma_set_range(new_vma, addr, addr + len, pgoff); + if (vma_dup_policy(vma, new_vma)) + goto out_free_vma; + if (anon_vma_clone(new_vma, vma)) + goto out_free_mempol; + if (new_vma->vm_file) + get_file(new_vma->vm_file); + if (new_vma->vm_ops && new_vma->vm_ops->open) + new_vma->vm_ops->open(new_vma); + if (vma_link(mm, new_vma)) + goto out_vma_link; + *need_rmap_locks = false; + } + return new_vma; + +out_vma_link: + if (new_vma->vm_ops && new_vma->vm_ops->close) + new_vma->vm_ops->close(new_vma); + + if (new_vma->vm_file) + fput(new_vma->vm_file); + + unlink_anon_vmas(new_vma); +out_free_mempol: + mpol_put(vma_policy(new_vma)); +out_free_vma: + vm_area_free(new_vma); +out: + return NULL; +} + +/* + * Rough compatibility check to quickly see if it's even worth looking + * at sharing an anon_vma. + * + * They need to have the same vm_file, and the flags can only differ + * in things that mprotect may change. + * + * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that + * we can merge the two vma's. For example, we refuse to merge a vma if + * there is a vm_ops->close() function, because that indicates that the + * driver is doing some kind of reference counting. But that doesn't + * really matter for the anon_vma sharing case. + */ +static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b) +{ + return a->vm_end == b->vm_start && + mpol_equal(vma_policy(a), vma_policy(b)) && + a->vm_file == b->vm_file && + !((a->vm_flags ^ b->vm_flags) & ~(VM_ACCESS_FLAGS | VM_SOFTDIRTY)) && + b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT); +} + +/* + * Do some basic sanity checking to see if we can re-use the anon_vma + * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be + * the same as 'old', the other will be the new one that is trying + * to share the anon_vma. + * + * NOTE! This runs with mmap_lock held for reading, so it is possible that + * the anon_vma of 'old' is concurrently in the process of being set up + * by another page fault trying to merge _that_. But that's ok: if it + * is being set up, that automatically means that it will be a singleton + * acceptable for merging, so we can do all of this optimistically. But + * we do that READ_ONCE() to make sure that we never re-load the pointer. + * + * IOW: that the "list_is_singular()" test on the anon_vma_chain only + * matters for the 'stable anon_vma' case (ie the thing we want to avoid + * is to return an anon_vma that is "complex" due to having gone through + * a fork). + * + * We also make sure that the two vma's are compatible (adjacent, + * and with the same memory policies). That's all stable, even with just + * a read lock on the mmap_lock. + */ +static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, + struct vm_area_struct *a, + struct vm_area_struct *b) +{ + if (anon_vma_compatible(a, b)) { + struct anon_vma *anon_vma = READ_ONCE(old->anon_vma); + + if (anon_vma && list_is_singular(&old->anon_vma_chain)) + return anon_vma; + } + return NULL; +} + +/* + * find_mergeable_anon_vma is used by anon_vma_prepare, to check + * neighbouring vmas for a suitable anon_vma, before it goes off + * to allocate a new anon_vma. It checks because a repetitive + * sequence of mprotects and faults may otherwise lead to distinct + * anon_vmas being allocated, preventing vma merge in subsequent + * mprotect. + */ +struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma) +{ + struct anon_vma *anon_vma = NULL; + struct vm_area_struct *prev, *next; + VMA_ITERATOR(vmi, vma->vm_mm, vma->vm_end); + + /* Try next first. */ + next = vma_iter_load(&vmi); + if (next) { + anon_vma = reusable_anon_vma(next, vma, next); + if (anon_vma) + return anon_vma; + } + + prev = vma_prev(&vmi); + VM_BUG_ON_VMA(prev != vma, vma); + prev = vma_prev(&vmi); + /* Try prev next. */ + if (prev) + anon_vma = reusable_anon_vma(prev, prev, vma); + + /* + * We might reach here with anon_vma == NULL if we can't find + * any reusable anon_vma. + * There's no absolute need to look only at touching neighbours: + * we could search further afield for "compatible" anon_vmas. + * But it would probably just be a waste of time searching, + * or lead to too many vmas hanging off the same anon_vma. + * We're trying to allow mprotect remerging later on, + * not trying to minimize memory used for anon_vmas. + */ + return anon_vma; +} + +static bool vm_ops_needs_writenotify(const struct vm_operations_struct *vm_ops) +{ + return vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite); +} + +static bool vma_is_shared_writable(struct vm_area_struct *vma) +{ + return (vma->vm_flags & (VM_WRITE | VM_SHARED)) == + (VM_WRITE | VM_SHARED); +} + +static bool vma_fs_can_writeback(struct vm_area_struct *vma) +{ + /* No managed pages to writeback. */ + if (vma->vm_flags & VM_PFNMAP) + return false; + + return vma->vm_file && vma->vm_file->f_mapping && + mapping_can_writeback(vma->vm_file->f_mapping); +} + +/* + * Does this VMA require the underlying folios to have their dirty state + * tracked? + */ +bool vma_needs_dirty_tracking(struct vm_area_struct *vma) +{ + /* Only shared, writable VMAs require dirty tracking. */ + if (!vma_is_shared_writable(vma)) + return false; + + /* Does the filesystem need to be notified? */ + if (vm_ops_needs_writenotify(vma->vm_ops)) + return true; + + /* + * Even if the filesystem doesn't indicate a need for writenotify, if it + * can writeback, dirty tracking is still required. + */ + return vma_fs_can_writeback(vma); +} + +/* + * Some shared mappings will want the pages marked read-only + * to track write events. If so, we'll downgrade vm_page_prot + * to the private version (using protection_map[] without the + * VM_SHARED bit). + */ +bool vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot) +{ + /* If it was private or non-writable, the write bit is already clear */ + if (!vma_is_shared_writable(vma)) + return false; + + /* The backer wishes to know when pages are first written to? */ + if (vm_ops_needs_writenotify(vma->vm_ops)) + return true; + + /* The open routine did something to the protections that pgprot_modify + * won't preserve? */ + if (pgprot_val(vm_page_prot) != + pgprot_val(vm_pgprot_modify(vm_page_prot, vma->vm_flags))) + return false; + + /* + * Do we need to track softdirty? hugetlb does not support softdirty + * tracking yet. + */ + if (vma_soft_dirty_enabled(vma) && !is_vm_hugetlb_page(vma)) + return true; + + /* Do we need write faults for uffd-wp tracking? */ + if (userfaultfd_wp(vma)) + return true; + + /* Can the mapping track the dirty pages? */ + return vma_fs_can_writeback(vma); +} + +static DEFINE_MUTEX(mm_all_locks_mutex); + +static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma) +{ + if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) { + /* + * The LSB of head.next can't change from under us + * because we hold the mm_all_locks_mutex. + */ + down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_lock); + /* + * We can safely modify head.next after taking the + * anon_vma->root->rwsem. If some other vma in this mm shares + * the same anon_vma we won't take it again. + * + * No need of atomic instructions here, head.next + * can't change from under us thanks to the + * anon_vma->root->rwsem. + */ + if (__test_and_set_bit(0, (unsigned long *) + &anon_vma->root->rb_root.rb_root.rb_node)) + BUG(); + } +} + +static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping) +{ + if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) { + /* + * AS_MM_ALL_LOCKS can't change from under us because + * we hold the mm_all_locks_mutex. + * + * Operations on ->flags have to be atomic because + * even if AS_MM_ALL_LOCKS is stable thanks to the + * mm_all_locks_mutex, there may be other cpus + * changing other bitflags in parallel to us. + */ + if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags)) + BUG(); + down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock); + } +} + +/* + * This operation locks against the VM for all pte/vma/mm related + * operations that could ever happen on a certain mm. This includes + * vmtruncate, try_to_unmap, and all page faults. + * + * The caller must take the mmap_lock in write mode before calling + * mm_take_all_locks(). The caller isn't allowed to release the + * mmap_lock until mm_drop_all_locks() returns. + * + * mmap_lock in write mode is required in order to block all operations + * that could modify pagetables and free pages without need of + * altering the vma layout. It's also needed in write mode to avoid new + * anon_vmas to be associated with existing vmas. + * + * A single task can't take more than one mm_take_all_locks() in a row + * or it would deadlock. + * + * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in + * mapping->flags avoid to take the same lock twice, if more than one + * vma in this mm is backed by the same anon_vma or address_space. + * + * We take locks in following order, accordingly to comment at beginning + * of mm/rmap.c: + * - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for + * hugetlb mapping); + * - all vmas marked locked + * - all i_mmap_rwsem locks; + * - all anon_vma->rwseml + * + * We can take all locks within these types randomly because the VM code + * doesn't nest them and we protected from parallel mm_take_all_locks() by + * mm_all_locks_mutex. + * + * mm_take_all_locks() and mm_drop_all_locks are expensive operations + * that may have to take thousand of locks. + * + * mm_take_all_locks() can fail if it's interrupted by signals. + */ +int mm_take_all_locks(struct mm_struct *mm) +{ + struct vm_area_struct *vma; + struct anon_vma_chain *avc; + VMA_ITERATOR(vmi, mm, 0); + + mmap_assert_write_locked(mm); + + mutex_lock(&mm_all_locks_mutex); + + /* + * vma_start_write() does not have a complement in mm_drop_all_locks() + * because vma_start_write() is always asymmetrical; it marks a VMA as + * being written to until mmap_write_unlock() or mmap_write_downgrade() + * is reached. + */ + for_each_vma(vmi, vma) { + if (signal_pending(current)) + goto out_unlock; + vma_start_write(vma); + } + + vma_iter_init(&vmi, mm, 0); + for_each_vma(vmi, vma) { + if (signal_pending(current)) + goto out_unlock; + if (vma->vm_file && vma->vm_file->f_mapping && + is_vm_hugetlb_page(vma)) + vm_lock_mapping(mm, vma->vm_file->f_mapping); + } + + vma_iter_init(&vmi, mm, 0); + for_each_vma(vmi, vma) { + if (signal_pending(current)) + goto out_unlock; + if (vma->vm_file && vma->vm_file->f_mapping && + !is_vm_hugetlb_page(vma)) + vm_lock_mapping(mm, vma->vm_file->f_mapping); + } + + vma_iter_init(&vmi, mm, 0); + for_each_vma(vmi, vma) { + if (signal_pending(current)) + goto out_unlock; + if (vma->anon_vma) + list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) + vm_lock_anon_vma(mm, avc->anon_vma); + } + + return 0; + +out_unlock: + mm_drop_all_locks(mm); + return -EINTR; +} + +static void vm_unlock_anon_vma(struct anon_vma *anon_vma) +{ + if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) { + /* + * The LSB of head.next can't change to 0 from under + * us because we hold the mm_all_locks_mutex. + * + * We must however clear the bitflag before unlocking + * the vma so the users using the anon_vma->rb_root will + * never see our bitflag. + * + * No need of atomic instructions here, head.next + * can't change from under us until we release the + * anon_vma->root->rwsem. + */ + if (!__test_and_clear_bit(0, (unsigned long *) + &anon_vma->root->rb_root.rb_root.rb_node)) + BUG(); + anon_vma_unlock_write(anon_vma); + } +} + +static void vm_unlock_mapping(struct address_space *mapping) +{ + if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) { + /* + * AS_MM_ALL_LOCKS can't change to 0 from under us + * because we hold the mm_all_locks_mutex. + */ + i_mmap_unlock_write(mapping); + if (!test_and_clear_bit(AS_MM_ALL_LOCKS, + &mapping->flags)) + BUG(); + } +} + +/* + * The mmap_lock cannot be released by the caller until + * mm_drop_all_locks() returns. + */ +void mm_drop_all_locks(struct mm_struct *mm) +{ + struct vm_area_struct *vma; + struct anon_vma_chain *avc; + VMA_ITERATOR(vmi, mm, 0); + + mmap_assert_write_locked(mm); + BUG_ON(!mutex_is_locked(&mm_all_locks_mutex)); + + for_each_vma(vmi, vma) { + if (vma->anon_vma) + list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) + vm_unlock_anon_vma(avc->anon_vma); + if (vma->vm_file && vma->vm_file->f_mapping) + vm_unlock_mapping(vma->vm_file->f_mapping); + } + + mutex_unlock(&mm_all_locks_mutex); +} |