/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_PAGEWALK_H
#define _LINUX_PAGEWALK_H
#include <linux/mm.h>
struct mm_walk;
/* Locking requirement during a page walk. */
enum page_walk_lock {
/* mmap_lock should be locked for read to stabilize the vma tree */
PGWALK_RDLOCK = 0,
/* vma will be write-locked during the walk */
PGWALK_WRLOCK = 1,
/* vma is expected to be already write-locked during the walk */
PGWALK_WRLOCK_VERIFY = 2,
};
/**
* struct mm_walk_ops - callbacks for walk_page_range
* @pgd_entry: if set, called for each non-empty PGD (top-level) entry
* @p4d_entry: if set, called for each non-empty P4D entry
* @pud_entry: if set, called for each non-empty PUD entry
* @pmd_entry: if set, called for each non-empty PMD entry
* this handler is required to be able to handle
* pmd_trans_huge() pmds. They may simply choose to
* split_huge_page() instead of handling it explicitly.
* @pte_entry: if set, called for each PTE (lowest-level) entry,
* including empty ones
* @pte_hole: if set, called for each hole at all levels,
* depth is -1 if not known, 0:PGD, 1:P4D, 2:PUD, 3:PMD.
* Any folded depths (where PTRS_PER_P?D is equal to 1)
* are skipped.
* @hugetlb_entry: if set, called for each hugetlb entry. This hook
* function is called with the vma lock held, in order to
* protect against a concurrent freeing of the pte_t* or
* the ptl. In some cases, the hook function needs to drop
* and retake the vma lock in order to avoid deadlocks
* while calling other functions. In such cases the hook
* function must either refrain from accessing the pte or
* ptl after dropping the vma lock, or else revalidate
* those items after re-acquiring the vma lock and before
* accessing them.
* @test_walk: caller specific callback function to determine whether
* we walk over the current vma or not. Returning 0 means
* "do page table walk over the current vma", returning
* a negative value means "abort current page table walk
* right now" and returning 1 means "skip the current vma"
* Note that this callback is not called when the caller
* passes in a single VMA as for walk_page_vma().
* @pre_vma: if set, called before starting walk on a non-null vma.
* @post_vma: if set, called after a walk on a non-null vma, provided
* that @pre_vma and the vma walk succeeded.
*
* p?d_entry callbacks are called even if those levels are folded on a
* particular architecture/configuration.
*/
struct mm_walk_ops {
int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
unsigned long next, struct mm_walk *walk);
int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
unsigned long next, struct mm_walk *walk);
int (*pud_entry)(pud_t *pud, unsigned long addr,
unsigned long next, struct mm_walk *walk);
int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
unsigned long next, struct mm_walk *walk);
int (*pte_entry)(pte_t *pte, unsigned long addr,
unsigned long next, struct mm_walk *walk);
int (*pte_hole)(unsigned long addr, unsigned long next,
int depth, struct mm_walk *walk);
int (*hugetlb_entry)(pte_t *pte, unsigned long hmask,
unsigned long addr, unsigned long next,
struct mm_walk *walk);
int (*test_walk)(unsigned long addr, unsigned long next,
struct mm_walk *walk);
int (*pre_vma)(unsigned long start, unsigned long end,
struct mm_walk *walk);
void (*post_vma)(struct mm_walk *walk);
enum page_walk_lock walk_lock;
};
/*
* Action for pud_entry / pmd_entry callbacks.
* ACTION_SUBTREE is the default
*/
enum page_walk_action {
/* Descend to next level, splitting huge pages if needed and possible */
ACTION_SUBTREE = 0,
/* Continue to next entry at this level (ignoring any subtree) */
ACTION_CONTINUE = 1,
/* Call again for this entry */
ACTION_AGAIN = 2
};
/**
* struct mm_walk - walk_page_range data
* @ops: operation to call during the walk
* @mm: mm_struct representing the target process of page table walk
* @pgd: pointer to PGD; only valid with no_vma (otherwise set to NULL)
* @vma: vma currently walked (NULL if walking outside vmas)
* @action: next action to perform (see enum page_walk_action)
* @no_vma: walk ignoring vmas (vma will always be NULL)
* @private: private data for callbacks' usage
*
* (see the comment on walk_page_range() for more details)
*/
struct mm_walk {
const struct mm_walk_ops *ops;
struct mm_struct *mm;
pgd_t *pgd;
struct vm_area_struct *vma;
enum page_walk_action action;
bool no_vma;
void *private;
};
int walk_page_range(struct mm_struct *mm, unsigned long start,
unsigned long end, const struct mm_walk_ops *ops,
void *private);
int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
unsigned long end, const struct mm_walk_ops *ops,
pgd_t *pgd,
void *private);
int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
unsigned long end, const struct mm_walk_ops *ops,
void *private);
int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
void *private);
int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
pgoff_t nr, const struct mm_walk_ops *ops,
void *private);
typedef int __bitwise folio_walk_flags_t;
/*
* Walk migration entries as well. Careful: a large folio might get split
* concurrently.
*/
#define FW_MIGRATION ((__force folio_walk_flags_t)BIT(0))
/* Walk shared zeropages (small + huge) as well. */
#define FW_ZEROPAGE ((__force folio_walk_flags_t)BIT(1))
enum folio_walk_level {
FW_LEVEL_PTE,
FW_LEVEL_PMD,
FW_LEVEL_PUD,
};
/**
* struct folio_walk - folio_walk_start() / folio_walk_end() data
* @page: exact folio page referenced (if applicable)
* @level: page table level identifying the entry type
* @pte: pointer to the page table entry (FW_LEVEL_PTE).
* @pmd: pointer to the page table entry (FW_LEVEL_PMD).
* @pud: pointer to the page table entry (FW_LEVEL_PUD).
* @ptl: pointer to the page table lock.
*
* (see folio_walk_start() documentation for more details)
*/
struct folio_walk {
/* public */
struct page *page;
enum folio_walk_level level;
union {
pte_t *ptep;
pud_t *pudp;
pmd_t *pmdp;
};
union {
pte_t pte;
pud_t pud;
pmd_t pmd;
};
/* private */
struct vm_area_struct *vma;
spinlock_t *ptl;
};
struct folio *folio_walk_start(struct folio_walk *fw,
struct vm_area_struct *vma, unsigned long addr,
folio_walk_flags_t flags);
#define folio_walk_end(__fw, __vma) do { \
spin_unlock((__fw)->ptl); \
if (likely((__fw)->level == FW_LEVEL_PTE)) \
pte_unmap((__fw)->ptep); \
vma_pgtable_walk_end(__vma); \
} while (0)
#endif /* _LINUX_PAGEWALK_H */
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