// SPDX-License-Identifier: GPL-2.0
#include <linux/pagewalk.h>
#include <linux/highmem.h>
#include <linux/sched.h>
#include <linux/hugetlb.h>
/*
* We want to know the real level where a entry is located ignoring any
* folding of levels which may be happening. For example if p4d is folded then
* a missing entry found at level 1 (p4d) is actually at level 0 (pgd).
*/
static int real_depth(int depth)
{
if (depth == 3 && PTRS_PER_PMD == 1)
depth = 2;
if (depth == 2 && PTRS_PER_PUD == 1)
depth = 1;
if (depth == 1 && PTRS_PER_P4D == 1)
depth = 0;
return depth;
}
static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
for (;;) {
err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
if (err)
break;
if (addr >= end - PAGE_SIZE)
break;
addr += PAGE_SIZE;
pte++;
}
return err;
}
static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pte_t *pte;
int err = 0;
spinlock_t *ptl;
if (walk->no_vma) {
pte = pte_offset_map(pmd, addr);
err = walk_pte_range_inner(pte, addr, end, walk);
pte_unmap(pte);
} else {
pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
err = walk_pte_range_inner(pte, addr, end, walk);
pte_unmap_unlock(pte, ptl);
}
return err;
}
#ifdef CONFIG_ARCH_HAS_HUGEPD
static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
unsigned long end, struct mm_walk *walk, int pdshift)
{
int err = 0;
const struct mm_walk_ops *ops = walk->ops;
int shift = hugepd_shift(*phpd);
int page_size = 1 << shift;
if (!ops->pte_entry)
return 0;
if (addr & (page_size - 1))
return 0;
for (;;) {
pte_t *pte;
spin_lock(&walk->mm->page_table_lock);
pte = hugepte_offset(*phpd, addr, pdshift);
err = ops->pte_entry(pte, addr, addr + page_size, walk);
spin_unlock(&walk->mm->page_table_lock);
if (err)
break;
if (addr >= end - page_size)
break;
addr += page_size;
}
return err;
}
#else
static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
unsigned long end, struct mm_walk *walk, int pdshift)
{
return 0;
}
#endif
static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pmd_t *pmd;
unsigned long next;
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
int depth = real_depth(3);
pmd = pmd_offset(pud, addr);
do {
again:
next = pmd_addr_end(addr, end);
if (pmd_none(*pmd) || (!walk->vma && !walk->no_vma)) {
if (ops->pte_hole)
err = ops->pte_hole(addr, next, depth, walk);
if (err)
break;
continue;
}
walk->action = ACTION_SUBTREE;
/*
* This implies that each ->pmd_entry() handler
* needs to know about pmd_trans_huge() pmds
*/
if (ops->pmd_entry)
err = ops->pmd_entry(pmd, addr, next, walk);
if (err)
break;
if (walk->action == ACTION_AGAIN)
goto again;
/*
* Check this here so we only break down trans_huge
* pages when we _need_ to
*/
if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) ||
walk->action == ACTION_CONTINUE ||
!(ops->pte_entry))
continue;
if (walk->vma) {
split_huge_pmd(walk->vma, pmd, addr);
if (pmd_trans_unstable(pmd))
goto again;
}
if (is_hugepd(__hugepd(pmd_val(*pmd))))
err = walk_hugepd_range((hugepd_t *)pmd, addr, next, walk, PMD_SHIFT);
else
err = walk_pte_range(pmd, addr, next, walk);
if (err)
break;
} while (pmd++, addr = next, addr != end);
return err;
}
static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pud_t *pud;
unsigned long next;
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
int depth = real_depth(2);
pud = pud_offset(p4d, addr);
do {
again:
next = pud_addr_end(addr, end);
if (pud_none(*pud) || (!walk->vma && !walk->no_vma)) {
if (ops->pte_hole)
err = ops->pte_hole(addr, next, depth, walk);
if (err)
break;
continue;
}
walk->action = ACTION_SUBTREE;
if (ops->pud_entry)
err = ops->pud_entry(pud, addr, next, walk);
if (err)
break;
if (walk->action == ACTION_AGAIN)
goto again;
if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) ||
walk->action == ACTION_CONTINUE ||
!(ops->pmd_entry || ops->pte_entry))
continue;
if (walk->vma)
split_huge_pud(walk->vma, pud, addr);
if (pud_none(*pud))
goto again;
if (is_hugepd(__hugepd(pud_val(*pud))))
err = walk_hugepd_range((hugepd_t *)pud, addr, next, walk, PUD_SHIFT);
else
err = walk_pmd_range(pud, addr, next, walk);
if (err)
break;
} while (pud++, addr = next, addr != end);
return err;
}
static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
p4d_t *p4d;
unsigned long next;
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
int depth = real_depth(1);
p4d = p4d_offset(pgd, addr);
do {
next = p4d_addr_end(addr, end);
if (p4d_none_or_clear_bad(p4d)) {
if (ops->pte_hole)
err = ops->pte_hole(addr, next, depth, walk);
if (err)
break;
continue;
}
if (ops->p4d_entry) {
err = ops->p4d_entry(p4d, addr, next, walk);
if (err)
break;
}
if (is_hugepd(__hugepd(p4d_val(*p4d))))
err = walk_hugepd_range((hugepd_t *)p4d, addr, next, walk, P4D_SHIFT);
else if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
err = walk_pud_range(p4d, addr, next, walk);
if (err)
break;
} while (p4d++, addr = next, addr != end);
return err;
}
static int walk_pgd_range(unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pgd_t *pgd;
unsigned long next;
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
if (walk->pgd)
pgd = walk->pgd + pgd_index(addr);
else
pgd = pgd_offset(walk->mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd)) {
if (ops->pte_hole)
err = ops->pte_hole(addr, next, 0, walk);
if (err)
break;
continue;
}
if (ops->pgd_entry) {
err = ops->pgd_entry(pgd, addr, next, walk);
if (err)
break;
}
if (is_hugepd(__hugepd(pgd_val(*pgd))))
err = walk_hugepd_range((hugepd_t *)pgd, addr, next, walk, PGDIR_SHIFT);
else if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry)
err = walk_p4d_range(pgd, addr, next, walk);
if (err)
break;
} while (pgd++, addr = next, addr != end);
return err;
}
#ifdef CONFIG_HUGETLB_PAGE
static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
unsigned long end)
{
unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
return boundary < end ? boundary : end;
}
static int walk_hugetlb_range(unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct vm_area_struct *vma = walk->vma;
struct hstate *h = hstate_vma(vma);
unsigned long next;
unsigned long hmask = huge_page_mask(h);
unsigned long sz = huge_page_size(h);
pte_t *pte;
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
do {
next = hugetlb_entry_end(h, addr, end);
pte = huge_pte_offset(walk->mm, addr & hmask, sz);
if (pte)
err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
else if (ops->pte_hole)
err = ops->pte_hole(addr, next, -1, walk);
if (err)
break;
} while (addr = next, addr != end);
return err;
}
#else /* CONFIG_HUGETLB_PAGE */
static int walk_hugetlb_range(unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
return 0;
}
#endif /* CONFIG_HUGETLB_PAGE */
/*
* Decide whether we really walk over the current vma on [@start, @end)
* or skip it via the returned value. Return 0 if we do walk over the
* current vma, and return 1 if we skip the vma. Negative values means
* error, where we abort the current walk.
*/
static int walk_page_test(unsigned long start, unsigned long end,
struct mm_walk *walk)
{
struct vm_area_struct *vma = walk->vma;
const struct mm_walk_ops *ops = walk->ops;
if (ops->test_walk)
return ops->test_walk(start, end, walk);
/*
* vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
* range, so we don't walk over it as we do for normal vmas. However,
* Some callers are interested in handling hole range and they don't
* want to just ignore any single address range. Such users certainly
* define their ->pte_hole() callbacks, so let's delegate them to handle
* vma(VM_PFNMAP).
*/
if (vma->vm_flags & VM_PFNMAP) {
int err = 1;
if (ops->pte_hole)
err = ops->pte_hole(start, end, -1, walk);
return err ? err : 1;
}
return 0;
}
static int __walk_page_range(unsigned long start, unsigned long end,
struct mm_walk *walk)
{
int err = 0;
struct vm_area_struct *vma = walk->vma;
const struct mm_walk_ops *ops = walk->ops;
if (vma && ops->pre_vma) {
err = ops->pre_vma(start, end, walk);
if (err)
return err;
}
if (vma && is_vm_hugetlb_page(vma)) {
if (ops->hugetlb_entry)
err = walk_hugetlb_range(start, end, walk);
} else
err = walk_pgd_range(start, end, walk);
if (vma && ops->post_vma)
ops->post_vma(walk);
return err;
}
/**
* walk_page_range - walk page table with caller specific callbacks
* @mm: mm_struct representing the target process of page table walk
* @start: start address of the virtual address range
* @end: end address of the virtual address range
* @ops: operation to call during the walk
* @private: private data for callbacks' usage
*
* Recursively walk the page table tree of the process represented by @mm
* within the virtual address range [@start, @end). During walking, we can do
* some caller-specific works for each entry, by setting up pmd_entry(),
* pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
* callbacks, the associated entries/pages are just ignored.
* The return values of these callbacks are commonly defined like below:
*
* - 0 : succeeded to handle the current entry, and if you don't reach the
* end address yet, continue to walk.
* - >0 : succeeded to handle the current entry, and return to the caller
* with caller specific value.
* - <0 : failed to handle the current entry, and return to the caller
* with error code.
*
* Before starting to walk page table, some callers want to check whether
* they really want to walk over the current vma, typically by checking
* its vm_flags. walk_page_test() and @ops->test_walk() are used for this
* purpose.
*
* If operations need to be staged before and committed after a vma is walked,
* there are two callbacks, pre_vma() and post_vma(). Note that post_vma(),
* since it is intended to handle commit-type operations, can't return any
* errors.
*
* struct mm_walk keeps current values of some common data like vma and pmd,
* which are useful for the access from callbacks. If you want to pass some
* caller-specific data to callbacks, @private should be helpful.
*
* Locking:
* Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock,
* because these function traverse vma list and/or access to vma's data.
*/
int walk_page_range(struct mm_struct *mm, unsigned long start,
unsigned long end, const struct mm_walk_ops *ops,
void *private)
{
int err = 0;
unsigned long next;
struct vm_area_struct *vma;
struct mm_walk walk = {
.ops = ops,
.mm = mm,
.private = private,
};
if (start >= end)
return -EINVAL;
if (!walk.mm)
return -EINVAL;
mmap_assert_locked(walk.mm);
vma = find_vma(walk.mm, start);
do {
if (!vma) { /* after the last vma */
walk.vma = NULL;
next = end;
} else if (start < vma->vm_start) { /* outside vma */
walk.vma = NULL;
next = min(end, vma->vm_start);
} else { /* inside vma */
walk.vma = vma;
next = min(end, vma->vm_end);
vma = vma->vm_next;
err = walk_page_test(start, next, &walk);
if (err > 0) {
/*
* positive return values are purely for
* controlling the pagewalk, so should never
* be passed to the callers.
*/
err = 0;
continue;
}
if (err < 0)
break;
}
if (walk.vma || walk.ops->pte_hole)
err = __walk_page_range(start, next, &walk);
if (err)
break;
} while (start = next, start < end);
return err;
}
/**
* walk_page_range_novma - walk a range of pagetables not backed by a vma
* @mm: mm_struct representing the target process of page table walk
* @start: start address of the virtual address range
* @end: end address of the virtual address range
* @ops: operation to call during the walk
* @pgd: pgd to walk if different from mm->pgd
* @private: private data for callbacks' usage
*
* Similar to walk_page_range() but can walk any page tables even if they are
* not backed by VMAs. Because 'unusual' entries may be walked this function
* will also not lock the PTEs for the pte_entry() callback. This is useful for
* walking the kernel pages tables or page tables for firmware.
*/
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)
{
struct mm_walk walk = {
.ops = ops,
.mm = mm,
.pgd = pgd,
.private = private,
.no_vma = true
};
if (start >= end || !walk.mm)
return -EINVAL;
mmap_assert_locked(walk.mm);
return __walk_page_range(start, end, &walk);
}
int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
void *private)
{
struct mm_walk walk = {
.ops = ops,
.mm = vma->vm_mm,
.vma = vma,
.private = private,
};
int err;
if (!walk.mm)
return -EINVAL;
mmap_assert_locked(walk.mm);
err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
if (err > 0)
return 0;
if (err < 0)
return err;
return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
}
/**
* walk_page_mapping - walk all memory areas mapped into a struct address_space.
* @mapping: Pointer to the struct address_space
* @first_index: First page offset in the address_space
* @nr: Number of incremental page offsets to cover
* @ops: operation to call during the walk
* @private: private data for callbacks' usage
*
* This function walks all memory areas mapped into a struct address_space.
* The walk is limited to only the given page-size index range, but if
* the index boundaries cross a huge page-table entry, that entry will be
* included.
*
* Also see walk_page_range() for additional information.
*
* Locking:
* This function can't require that the struct mm_struct::mmap_lock is held,
* since @mapping may be mapped by multiple processes. Instead
* @mapping->i_mmap_rwsem must be held. This might have implications in the
* callbacks, and it's up tho the caller to ensure that the
* struct mm_struct::mmap_lock is not needed.
*
* Also this means that a caller can't rely on the struct
* vm_area_struct::vm_flags to be constant across a call,
* except for immutable flags. Callers requiring this shouldn't use
* this function.
*
* Return: 0 on success, negative error code on failure, positive number on
* caller defined premature termination.
*/
int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
pgoff_t nr, const struct mm_walk_ops *ops,
void *private)
{
struct mm_walk walk = {
.ops = ops,
.private = private,
};
struct vm_area_struct *vma;
pgoff_t vba, vea, cba, cea;
unsigned long start_addr, end_addr;
int err = 0;
lockdep_assert_held(&mapping->i_mmap_rwsem);
vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
first_index + nr - 1) {
/* Clip to the vma */
vba = vma->vm_pgoff;
vea = vba + vma_pages(vma);
cba = first_index;
cba = max(cba, vba);
cea = first_index + nr;
cea = min(cea, vea);
start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
if (start_addr >= end_addr)
continue;
walk.vma = vma;
walk.mm = vma->vm_mm;
err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
if (err > 0) {
err = 0;
break;
} else if (err < 0)
break;
err = __walk_page_range(start_addr, end_addr, &walk);
if (err)
break;
}
return err;
}
