// 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);
}
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