The PAGEMAP_SCAN IOCTL on the pagemap file can be used to get or optionally
clear the info about page table entries. The following operations are
supported in this IOCTL:
- Scan the address range and get the memory ranges matching the provided
criteria. This is performed when the output buffer is specified.
- Write-protect the pages. The PM_SCAN_WP_MATCHING is used to write-protect
the pages of interest. The PM_SCAN_CHECK_WPASYNC aborts the operation if
non-Async Write Protected pages are found. The ``PM_SCAN_WP_MATCHING``
can be used with or without PM_SCAN_CHECK_WPASYNC.
- Both of those operations can be combined into one atomic operation where
we can get and write protect the pages as well.
Following flags about pages are currently supported:
- PAGE_IS_WPALLOWED - Page has async-write-protection enabled
- PAGE_IS_WRITTEN - Page has been written to from the time it was write protected
- PAGE_IS_FILE - Page is file backed
- PAGE_IS_PRESENT - Page is present in the memory
- PAGE_IS_SWAPPED - Page is in swapped
- PAGE_IS_PFNZERO - Page has zero PFN
- PAGE_IS_HUGE - Page is THP or Hugetlb backed
This IOCTL can be extended to get information about more PTE bits. The
entire address range passed by user [start, end) is scanned until either
the user provided buffer is full or max_pages have been found.
Reviewed-by: Andrei Vagin <avagin@xxxxxxxxx>
Reviewed-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
---
Changes in v33:
- Add PAGE_IS_FILE support for THPs
Chagnes in v32:
- Remove un-needed if condition to set walk_end address
Changes in v31:
- Remove walk_end_addr
- Fix build warning by typecasting u64 variables to long first before
casting them to void *
Changes in v30:
- Minor nitpicks
Changes in v29:
- Cosmetic changes
- Add and improve comments
- Remove cur_buf as merging members issue has been removed
Changes in v28:
- Fix walk_end one last time after doing through testing
Changes in v27:
- Add PAGE_IS_HUGE
- Iterate until temporary buffer is full to do less iterations
- Don't check if PAGE_IS_FILE if no mask needs it as it is very
expensive to check per pte
- bring is_interesting_page() outside pagemap_scan_output() to remove
the horrible return value check
- Replace memcpy() with direct copy
- rename end_addr to walk_end_addr in pagemap_scan_private
- Abort walk if fatal_signal_pending()
Changes in v26:
Changes made by Usama:
- Fix the wrong breaking of loop if page isn't interesting, skip intsead
- Untag the address and save them into struct
- Round off the end address to next page
- Correct the partial hugetlb page handling and returning the error
- Rename PAGE_IS_WPASYNC to PAGE_IS_WPALLOWED
- Return walk ending address in walk_end instead of returning in start
as there is potential of replacing the memory tag
Changes by Michał:
1. the API:
a. return ranges as {begin, end} instead of {begin + len};
b. rename match "flags" to 'page categories' everywhere - this makes
it easier to differentiate the ioctl()s categorisation of pages
from struct page flags;
c. change {required + excluded} to {inverted + required}. This was
rejected before, but I'd like to illustrate the difference.
Old interface can be translated to the new by:
categories_inverted = excluded_mask
categories_mask = required_mask | excluded_mask
categories_anyof_mask = anyof_mask
The new way allows filtering by: A & (B | !C)
categories_inverted = C
categories_mask = A
categories_anyof_mask = B | C
e. allow no-op calls
2. the implementation:
a. gather the page-categorising and write-protecting code in one place;
b. optimization: add whole-vma skipping for WP usecase;
c. extracted output limiting code to pagemap_scan_output();
d. extracted range coalescing to pagemap_scan_push_range();
e. extracted THP entry handling to pagemap_scan_thp_entry();
f. added a shortcut for non-WP hugetlb scan; avoids conditional
locking;
g. extracted scan buffer handling code out of do_pagemap_scan();
h. rework output code to always try to write pending ranges; if EFAULT
is generated it always overwrites the original error code;
(the case of SIGKILL is needlessly trying to write the output
now, but this should be rare case and ignoring it makes the code
not needing a goto)
3.Change no-GET operation condition from `arg.return_mask == 0` to
`arg.vec == NULL`. This will allow issuing the ioctl with
return_mask == 0 to gather matching ranges when the exact category
is not interesting. (Anticipated for CRIU scanning a large sparse
anonymous mapping).
Changes in v25:
- Do proper filtering on hole as well (hole got missed earlier)
Changes in v24:
- Place WP markers in case of hole as well
Changes in v23:
- Set vec_buf_index to 0 only when vec_buf_index is set
- Return -EFAULT instead of -EINVAL if vec is NULL
- Correctly return the walk ending address to the page granularity
Changes in v22:
- Interface change to return walk ending address to user:
- Replace [start start + len) with [start, end)
- Return the ending address of the address walk in start
Changes in v21:
- Abort walk instead of returning error if WP is to be performed on
partial hugetlb
- Changed the data types of some variables in pagemap_scan_private to
long
Changes in v20:
- Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
Changes in v19:
- Interface changes such as renaming, return mask and WP can be used
with any flags specified in masks
- Internal code changes
Changes in v18:
- Rebased on top of next-20230613
- ptep_get() updates
- remove pmd_trans_unstable() and add ACTION_AGAIN
- Review updates (Micheal)
Changes in v17:
- Rebased on next-20230606
- Made make_uffd_wp_*_pte() better and minor changes
Changes in v16:
- Fixed a corner case where kernel writes beyond user buffer by one
element
- Bring back exclusive PM_SCAN_OP_WP
- Cosmetic changes
Changes in v15:
- Build fix:
- Use generic tlb flush function in pagemap_scan_pmd_entry() instead of
using x86 specific flush function in do_pagemap_scan()
- Remove #ifdef from pagemap_scan_hugetlb_entry()
- Use mm instead of undefined vma->vm_mm
Changes in v14:
- Fix build error caused by #ifdef added at last minute in some configs
Changes in v13:
- Review updates
- mmap_read_lock_killable() instead of mmap_read_lock()
- Replace uffd_wp_range() with helpers which increases performance
drastically for OP_WP operations by reducing the number of tlb
flushing etc
- Add MMU_NOTIFY_PROTECTION_VMA notification for the memory range
Changes in v12:
- Add hugetlb support to cover all memory types
- Merge "userfaultfd: Define dummy uffd_wp_range()" with this patch
- Review updates to the code
Changes in v11:
- Find written pages in a better way
- Fix a corner case (thanks Paul)
- Improve the code/comments
- remove ENGAGE_WP + ! GET operation
- shorten the commit message in favour of moving documentation to
pagemap.rst
Changes in v10:
- move changes in tools/include/uapi/linux/fs.h to separate patch
- update commit message
Change in v8:
- Correct is_pte_uffd_wp()
- Improve readability and error checks
- Remove some un-needed code
Changes in v7:
- Rebase on top of latest next
- Fix some corner cases
- Base soft-dirty on the uffd wp async
- Update the terminologies
- Optimize the memory usage inside the ioctl
---
fs/proc/task_mmu.c | 686 ++++++++++++++++++++++++++++++++++
include/linux/hugetlb.h | 1 +
include/linux/userfaultfd_k.h | 7 +
include/uapi/linux/fs.h | 59 +++
mm/hugetlb.c | 2 +-
5 files changed, 754 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4fba49bf09447..6e6261e8b91b1 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -19,6 +19,8 @@
#include <linux/shmem_fs.h>
#include <linux/uaccess.h>
#include <linux/pkeys.h>
+#include <linux/minmax.h>
+#include <linux/overflow.h>
#include <asm/elf.h>
#include <asm/tlb.h>
@@ -1760,11 +1762,695 @@ static int pagemap_release(struct inode *inode, struct file *file)
return 0;
}
+#define PM_SCAN_CATEGORIES (PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | \
+ PAGE_IS_FILE | PAGE_IS_PRESENT | \
+ PAGE_IS_SWAPPED | PAGE_IS_PFNZERO | \
+ PAGE_IS_HUGE)
+#define PM_SCAN_FLAGS (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC)
+
+struct pagemap_scan_private {
+ struct pm_scan_arg arg;
+ unsigned long masks_of_interest, cur_vma_category;
+ struct page_region *vec_buf;
+ unsigned long vec_buf_len, vec_buf_index, found_pages;
+ struct page_region __user *vec_out;
+};
+
+static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
+ struct vm_area_struct *vma,
+ unsigned long addr, pte_t pte)
+{
+ unsigned long categories = 0;
+
+ if (pte_present(pte)) {
+ struct page *page;
+
+ categories |= PAGE_IS_PRESENT;
+ if (!pte_uffd_wp(pte))
+ categories |= PAGE_IS_WRITTEN;
+
+ if (p->masks_of_interest & PAGE_IS_FILE) {
+ page = vm_normal_page(vma, addr, pte);
+ if (page && !PageAnon(page))
+ categories |= PAGE_IS_FILE;
+ }
+
+ if (is_zero_pfn(pte_pfn(pte)))
+ categories |= PAGE_IS_PFNZERO;
+ } else if (is_swap_pte(pte)) {
+ swp_entry_t swp;
+
+ categories |= PAGE_IS_SWAPPED;
+ if (!pte_swp_uffd_wp_any(pte))
+ categories |= PAGE_IS_WRITTEN;
+
+ if (p->masks_of_interest & PAGE_IS_FILE) {
+ swp = pte_to_swp_entry(pte);
+ if (is_pfn_swap_entry(swp) &&
+ !PageAnon(pfn_swap_entry_to_page(swp)))
+ categories |= PAGE_IS_FILE;
+ }
+ }
+
+ return categories;
+}
+
+static void make_uffd_wp_pte(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *pte)
+{
+ pte_t ptent = ptep_get(pte);
+
+ if (pte_present(ptent)) {
+ pte_t old_pte;
+
+ old_pte = ptep_modify_prot_start(vma, addr, pte);
+ ptent = pte_mkuffd_wp(ptent);
+ ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);
+ } else if (is_swap_pte(ptent)) {
+ ptent = pte_swp_mkuffd_wp(ptent);
+ set_pte_at(vma->vm_mm, addr, pte, ptent);
+ } else {
+ set_pte_at(vma->vm_mm, addr, pte,
+ make_pte_marker(PTE_MARKER_UFFD_WP));
+ }
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static unsigned long pagemap_thp_category(struct pagemap_scan_private *p,
+ struct vm_area_struct *vma,
+ unsigned long addr, pmd_t pmd)
+{
+ unsigned long categories = PAGE_IS_HUGE;
+
+ if (pmd_present(pmd)) {
+ struct page *page;
+
+ categories |= PAGE_IS_PRESENT;
+ if (!pmd_uffd_wp(pmd))
+ categories |= PAGE_IS_WRITTEN;
+
+ if (p->masks_of_interest & PAGE_IS_FILE) {
+ page = vm_normal_page_pmd(vma, addr, pmd);
+ if (page && !PageAnon(page))
+ categories |= PAGE_IS_FILE;
+ }
+
+ if (is_zero_pfn(pmd_pfn(pmd)))
+ categories |= PAGE_IS_PFNZERO;
+ } else if (is_swap_pmd(pmd)) {
+ swp_entry_t swp;
+
+ categories |= PAGE_IS_SWAPPED;
+ if (!pmd_swp_uffd_wp(pmd))
+ categories |= PAGE_IS_WRITTEN;
+
+ if (p->masks_of_interest & PAGE_IS_FILE) {
+ swp = pmd_to_swp_entry(pmd);
+ if (is_pfn_swap_entry(swp) &&
+ !PageAnon(pfn_swap_entry_to_page(swp)))
+ categories |= PAGE_IS_FILE;
+ }
+ }
+
+ return categories;
+}
+
+static void make_uffd_wp_pmd(struct vm_area_struct *vma,
+ unsigned long addr, pmd_t *pmdp)
+{
+ pmd_t old, pmd = *pmdp;
+
+ if (pmd_present(pmd)) {
+ old = pmdp_invalidate_ad(vma, addr, pmdp);
+ pmd = pmd_mkuffd_wp(old);
+ set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+ } else if (is_migration_entry(pmd_to_swp_entry(pmd))) {
+ pmd = pmd_swp_mkuffd_wp(pmd);
+ set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+ }
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+#ifdef CONFIG_HUGETLB_PAGE
+static unsigned long pagemap_hugetlb_category(pte_t pte)
+{
+ unsigned long categories = PAGE_IS_HUGE;
+
+ /*
+ * According to pagemap_hugetlb_range(), file-backed HugeTLB
+ * page cannot be swapped. So PAGE_IS_FILE is not checked for
+ * swapped pages.
+ */
+ if (pte_present(pte)) {
+ categories |= PAGE_IS_PRESENT;
+ if (!huge_pte_uffd_wp(pte))
+ categories |= PAGE_IS_WRITTEN;
+ if (!PageAnon(pte_page(pte)))
+ categories |= PAGE_IS_FILE;
+ if (is_zero_pfn(pte_pfn(pte)))
+ categories |= PAGE_IS_PFNZERO;
+ } else if (is_swap_pte(pte)) {
+ categories |= PAGE_IS_SWAPPED;
+ if (!pte_swp_uffd_wp_any(pte))
+ categories |= PAGE_IS_WRITTEN;
+ }
+
+ return categories;
+}
+
+static void make_uffd_wp_huge_pte(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ pte_t ptent)
+{
+ if (is_hugetlb_entry_hwpoisoned(ptent) || is_pte_marker(ptent))
+ return;
+
+ if (is_hugetlb_entry_migration(ptent))
+ set_huge_pte_at(vma->vm_mm, addr, ptep,
+ pte_swp_mkuffd_wp(ptent));
+ else if (!huge_pte_none(ptent))
+ huge_ptep_modify_prot_commit(vma, addr, ptep, ptent,
+ huge_pte_mkuffd_wp(ptent));
+ else
+ set_huge_pte_at(vma->vm_mm, addr, ptep,
+ make_pte_marker(PTE_MARKER_UFFD_WP));
+}
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static bool pagemap_scan_is_interesting_page(unsigned long categories,
+ const struct pagemap_scan_private *p)
+{
+ categories ^= p->arg.category_inverted;
+ if ((categories & p->arg.category_mask) != p->arg.category_mask)
+ return false;
+ if (p->arg.category_anyof_mask && !(categories & p->arg.category_anyof_mask))
+ return false;
+
+ return true;
+}
+
+static bool pagemap_scan_is_interesting_vma(unsigned long categories,
+ const struct pagemap_scan_private *p)
+{
+ unsigned long required = p->arg.category_mask & PAGE_IS_WPALLOWED;
+
+ categories ^= p->arg.category_inverted;
+ if ((categories & required) != required)
+ return false;
+
+ return true;
+}
+
+static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
+ struct mm_walk *walk)
+{
+ struct pagemap_scan_private *p = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ unsigned long vma_category = 0;
+
+ if (userfaultfd_wp_async(vma) && userfaultfd_wp_use_markers(vma))
+ vma_category |= PAGE_IS_WPALLOWED;
+ else if (p->arg.flags & PM_SCAN_CHECK_WPASYNC)
+ return -EPERM;
+
+ if (vma->vm_flags & VM_PFNMAP)
+ return 1;
+
+ if (!pagemap_scan_is_interesting_vma(vma_category, p))
+ return 1;
+
+ p->cur_vma_category = vma_category;
+
+ return 0;
+}
+
+static bool pagemap_scan_push_range(unsigned long categories,
+ struct pagemap_scan_private *p,
+ unsigned long addr, unsigned long end)
+{
+ struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index];
+
+ /*
+ * When there is no output buffer provided at all, the sentinel values
+ * won't match here. There is no other way for `cur_buf->end` to be
+ * non-zero other than it being non-empty.
+ */
+ if (addr == cur_buf->end && categories == cur_buf->categories) {
+ cur_buf->end = end;
+ return true;
+ }
+
+ if (cur_buf->end) {
+ if (p->vec_buf_index >= p->vec_buf_len - 1)
+ return false;
+
+ cur_buf = &p->vec_buf[++p->vec_buf_index];
+ }
+
+ cur_buf->start = addr;
+ cur_buf->end = end;
+ cur_buf->categories = categories;
+
+ return true;
+}
+
+static void pagemap_scan_backout_range(struct pagemap_scan_private *p,
+ unsigned long addr, unsigned long end)
+{
+ struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index];
+
+ if (cur_buf->start != addr)
+ cur_buf->end = addr;
+ else
+ cur_buf->start = cur_buf->end = 0;
+
+ p->found_pages -= (end - addr) / PAGE_SIZE;
+}
+
+static int pagemap_scan_output(unsigned long categories,
+ struct pagemap_scan_private *p,
+ unsigned long addr, unsigned long *end)
+{
+ unsigned long n_pages, total_pages;
+ int ret = 0;
+
+ if (!p->vec_buf)
+ return 0;
+
+ categories &= p->arg.return_mask;
+
+ n_pages = (*end - addr) / PAGE_SIZE;
+ if (check_add_overflow(p->found_pages, n_pages, &total_pages) ||
+ total_pages > p->arg.max_pages) {
+ size_t n_too_much = total_pages - p->arg.max_pages;
+ *end -= n_too_much * PAGE_SIZE;
+ n_pages -= n_too_much;
+ ret = -ENOSPC;
+ }
+
+ if (!pagemap_scan_push_range(categories, p, addr, *end)) {
+ *end = addr;
+ n_pages = 0;
+ ret = -ENOSPC;
+ }
+
+ p->found_pages += n_pages;
+ if (ret)
+ p->arg.walk_end = *end;
+
+ return ret;
+}
+
+static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start,
+ unsigned long end, struct mm_walk *walk)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ struct pagemap_scan_private *p = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ unsigned long categories;
+ spinlock_t *ptl;
+ int ret = 0;
+
+ ptl = pmd_trans_huge_lock(pmd, vma);
+ if (!ptl)
+ return -ENOENT;
+
+ categories = p->cur_vma_category |
+ pagemap_thp_category(p, vma, start, *pmd);
+
+ if (!pagemap_scan_is_interesting_page(categories, p))
+ goto out_unlock;
+
+ ret = pagemap_scan_output(categories, p, start, &end);
+ if (start == end)
+ goto out_unlock;
+
+ if (~p->arg.flags & PM_SCAN_WP_MATCHING)
+ goto out_unlock;
+ if (~categories & PAGE_IS_WRITTEN)
+ goto out_unlock;
+
+ /*
+ * Break huge page into small pages if the WP operation
+ * needs to be performed on a portion of the huge page.
+ */
+ if (end != start + HPAGE_SIZE) {
+ spin_unlock(ptl);
+ split_huge_pmd(vma, pmd, start);
+ pagemap_scan_backout_range(p, start, end);
+ /* Report as if there was no THP */
+ return -ENOENT;
+ }
+
+ make_uffd_wp_pmd(vma, start, pmd);
+ flush_tlb_range(vma, start, end);
+out_unlock:
+ spin_unlock(ptl);
+ return ret;
+#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
+ return -ENOENT;
+#endif
+}
+
+static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
+ unsigned long end, struct mm_walk *walk)
+{
+ struct pagemap_scan_private *p = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ unsigned long addr, flush_end = 0;
+ pte_t *pte, *start_pte;
+ spinlock_t *ptl;
+ int ret;
+
+ arch_enter_lazy_mmu_mode();
+
+ ret = pagemap_scan_thp_entry(pmd, start, end, walk);
+ if (ret != -ENOENT) {
+ arch_leave_lazy_mmu_mode();
+ return ret;
+ }
+
+ ret = 0;
+ start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
+ if (!pte) {
+ arch_leave_lazy_mmu_mode();
+ walk->action = ACTION_AGAIN;
+ return 0;
+ }
+
+ for (addr = start; addr != end; pte++, addr += PAGE_SIZE) {
+ unsigned long categories = p->cur_vma_category |
+ pagemap_page_category(p, vma, addr, ptep_get(pte));
+ unsigned long next = addr + PAGE_SIZE;
+
+ if (!pagemap_scan_is_interesting_page(categories, p))
+ continue;
+
+ ret = pagemap_scan_output(categories, p, addr, &next);
+ if (next == addr)
+ break;
+
+ if (~p->arg.flags & PM_SCAN_WP_MATCHING)
+ continue;
+ if (~categories & PAGE_IS_WRITTEN)
+ continue;
+
+ make_uffd_wp_pte(vma, addr, pte);
+ if (!flush_end)
+ start = addr;
+ flush_end = next;
+ }
+
+ if (flush_end)
+ flush_tlb_range(vma, start, addr);
+
+ pte_unmap_unlock(start_pte, ptl);
+ arch_leave_lazy_mmu_mode();
+
+ cond_resched();
+ return ret;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask,
+ unsigned long start, unsigned long end,
+ struct mm_walk *walk)
+{
+ struct pagemap_scan_private *p = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ unsigned long categories;
+ spinlock_t *ptl;
+ int ret = 0;
+ pte_t pte;
+
+ if (~p->arg.flags & PM_SCAN_WP_MATCHING) {
+ /* Go the short route when not write-protecting pages. */
+
+ pte = huge_ptep_get(ptep);
+ categories = p->cur_vma_category | pagemap_hugetlb_category(pte);
+
+ if (!pagemap_scan_is_interesting_page(categories, p))
+ return 0;
+
+ return pagemap_scan_output(categories, p, start, &end);
+ }
+
+ i_mmap_lock_write(vma->vm_file->f_mapping);
+ ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, ptep);
+
+ pte = huge_ptep_get(ptep);
+ categories = p->cur_vma_category | pagemap_hugetlb_category(pte);
+
+ if (!pagemap_scan_is_interesting_page(categories, p))
+ goto out_unlock;
+
+ ret = pagemap_scan_output(categories, p, start, &end);
+ if (start == end)
+ goto out_unlock;
+
+ if (~categories & PAGE_IS_WRITTEN)
+ goto out_unlock;
+
+ if (end != start + HPAGE_SIZE) {
+ /* Partial HugeTLB page WP isn't possible. */
+ pagemap_scan_backout_range(p, start, end);
+ p->arg.walk_end = start;
+ ret = 0;
+ goto out_unlock;
+ }
+
+ make_uffd_wp_huge_pte(vma, start, ptep, pte);
+ flush_hugetlb_tlb_range(vma, start, end);
+
+out_unlock:
+ spin_unlock(ptl);
+ i_mmap_unlock_write(vma->vm_file->f_mapping);
+
+ return ret;
+}
+#else
+#define pagemap_scan_hugetlb_entry NULL
+#endif
+
+static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
+ int depth, struct mm_walk *walk)
+{
+ struct pagemap_scan_private *p = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ int ret, err;
+
+ if (!vma || !pagemap_scan_is_interesting_page(p->cur_vma_category, p))
+ return 0;
+
+ ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end);
+ if (addr == end)
+ return ret;
+
+ if (~p->arg.flags & PM_SCAN_WP_MATCHING)
+ return ret;
+
+ err = uffd_wp_range(vma, addr, end - addr, true);
+ if (err < 0)
+ ret = err;
+
+ return ret;
+}
+
+static const struct mm_walk_ops pagemap_scan_ops = {
+ .test_walk = pagemap_scan_test_walk,
+ .pmd_entry = pagemap_scan_pmd_entry,
+ .pte_hole = pagemap_scan_pte_hole,
+ .hugetlb_entry = pagemap_scan_hugetlb_entry,
+};
+
+static int pagemap_scan_get_args(struct pm_scan_arg *arg,
+ unsigned long uarg)
+{
+ if (copy_from_user(arg, (void __user *)uarg, sizeof(*arg)))
+ return -EFAULT;
+
+ if (arg->size != sizeof(struct pm_scan_arg))
+ return -EINVAL;
+
+ /* Validate requested features */
+ if (arg->flags & ~PM_SCAN_FLAGS)
+ return -EINVAL;
+ if ((arg->category_inverted | arg->category_mask |
+ arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES)
+ return -EINVAL;
+
+ arg->start = untagged_addr((unsigned long)arg->start);
+ arg->end = untagged_addr((unsigned long)arg->end);
+ arg->vec = untagged_addr((unsigned long)arg->vec);
+
+ /* Validate memory pointers */
+ if (!IS_ALIGNED(arg->start, PAGE_SIZE))
+ return -EINVAL;
+ if (!access_ok((void __user *)(long)arg->start, arg->end - arg->start))
+ return -EFAULT;
+ if (!arg->vec && arg->vec_len)
+ return -EINVAL;
+ if (arg->vec && !access_ok((void __user *)(long)arg->vec,
+ arg->vec_len * sizeof(struct page_region)))
+ return -EFAULT;
+
+ /* Fixup default values */
+ arg->end = ALIGN(arg->end, PAGE_SIZE);
+ arg->walk_end = 0;
+ if (!arg->max_pages)
+ arg->max_pages = ULONG_MAX;
+
+ return 0;
+}
+
+static int pagemap_scan_writeback_args(struct pm_scan_arg *arg,
+ unsigned long uargl)
+{
+ struct pm_scan_arg __user *uarg = (void __user *)uargl;
+
+ if (copy_to_user(&uarg->walk_end, &arg->walk_end, sizeof(arg->walk_end)))
+ return -EFAULT;
+
+ return 0;
+}
+
+static int pagemap_scan_init_bounce_buffer(struct pagemap_scan_private *p)
+{
+ if (!p->arg.vec_len)
+ return 0;
+
+ p->vec_buf_len = min_t(size_t, PAGEMAP_WALK_SIZE >> PAGE_SHIFT,
+ p->arg.vec_len);
+ p->vec_buf = kmalloc_array(p->vec_buf_len, sizeof(*p->vec_buf),
+ GFP_KERNEL);
+ if (!p->vec_buf)
+ return -ENOMEM;
+
+ p->vec_buf->start = p->vec_buf->end = 0;
+ p->vec_out = (struct page_region __user *)(long)p->arg.vec;
+
+ return 0;
+}
+
+static long pagemap_scan_flush_buffer(struct pagemap_scan_private *p)
+{
+ const struct page_region *buf = p->vec_buf;
+ long n = p->vec_buf_index;
+
+ if (!p->vec_buf)
+ return 0;
+
+ if (buf[n].end != buf[n].start)
+ n++;
+
+ if (!n)
+ return 0;
+
+ if (copy_to_user(p->vec_out, buf, n * sizeof(*buf)))
+ return -EFAULT;
+
+ p->arg.vec_len -= n;
+ p->vec_out += n;
+
+ p->vec_buf_index = 0;
+ p->vec_buf_len = min_t(size_t, p->vec_buf_len, p->arg.vec_len);
+ p->vec_buf->start = p->vec_buf->end = 0;
+
+ return n;
+}
+
+static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg)
+{
+ struct mmu_notifier_range range;
+ struct pagemap_scan_private p = {0};
+ unsigned long walk_start;
+ size_t n_ranges_out = 0;
+ int ret;
+
+ ret = pagemap_scan_get_args(&p.arg, uarg);
+ if (ret)
+ return ret;
+
+ p.masks_of_interest = p.arg.category_mask | p.arg.category_anyof_mask |
+ p.arg.return_mask;
+ ret = pagemap_scan_init_bounce_buffer(&p);
+ if (ret)
+ return ret;
+
+ /* Protection change for the range is going to happen. */
+ if (p.arg.flags & PM_SCAN_WP_MATCHING) {
+ mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
+ mm, p.arg.start, p.arg.end);
+ mmu_notifier_invalidate_range_start(&range);
+ }
+
+ for (walk_start = p.arg.start; walk_start < p.arg.end;
+ walk_start = p.arg.walk_end) {
+ long n_out;
+
+ if (fatal_signal_pending(current)) {
+ ret = -EINTR;
+ break;
+ }
+
+ ret = mmap_read_lock_killable(mm);
+ if (ret)
+ break;
+ ret = walk_page_range(mm, walk_start, p.arg.end,
+ &pagemap_scan_ops, &p);
+ mmap_read_unlock(mm);
+
+ n_out = pagemap_scan_flush_buffer(&p);
+ if (n_out < 0)
+ ret = n_out;
+ else
+ n_ranges_out += n_out;
+
+ if (ret != -ENOSPC)
+ break;
+
+ if (p.arg.vec_len == 0 || p.found_pages == p.arg.max_pages)
+ break;
+ }
+
+ /* ENOSPC signifies early stop (buffer full) from the walk. */
+ if (!ret || ret == -ENOSPC)
+ ret = n_ranges_out;
+
+ /* The walk_end isn't set when ret is zero */
+ if (!p.arg.walk_end)
+ p.arg.walk_end = p.arg.end;
+ if (pagemap_scan_writeback_args(&p.arg, uarg))
+ ret = -EFAULT;
+
+ if (p.arg.flags & PM_SCAN_WP_MATCHING)
+ mmu_notifier_invalidate_range_end(&range);
+
+ kfree(p.vec_buf);
+ return ret;
+}
+
+static long do_pagemap_cmd(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ struct mm_struct *mm = file->private_data;
+
+ switch (cmd) {
+ case PAGEMAP_SCAN:
+ return do_pagemap_scan(mm, arg);
+
+ default:
+ return -EINVAL;
+ }
+}
+
const struct file_operations proc_pagemap_operations = {
.llseek = mem_lseek, /* borrow this */
.read = pagemap_read,
.open = pagemap_open,
.release = pagemap_release,
+ .unlocked_ioctl = do_pagemap_cmd,
+ .compat_ioctl = do_pagemap_cmd,
};
#endif /* CONFIG_PROC_PAGE_MONITOR */
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 0a393bc02f25b..8f8ff07453f22 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
unsigned long cp_flags);
bool is_hugetlb_entry_migration(pte_t pte);
+bool is_hugetlb_entry_hwpoisoned(pte_t pte);
void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
#else /* !CONFIG_HUGETLB_PAGE */
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index c98df391bfd8f..f2dc19f40d059 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -221,6 +221,13 @@ static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
return VM_FAULT_SIGBUS;
}
+static inline long uffd_wp_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long len,
+ bool enable_wp)
+{
+ return false;
+}
+
static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
struct vm_userfaultfd_ctx vm_ctx)
{
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index b7b56871029c5..da43810b74856 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -305,4 +305,63 @@ typedef int __bitwise __kernel_rwf_t;
#define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\
RWF_APPEND)
+/* Pagemap ioctl */
+#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg)
+
+/* Bitmasks provided in pm_scan_args masks and reported in page_region.categories. */
+#define PAGE_IS_WPALLOWED (1 << 0)
+#define PAGE_IS_WRITTEN (1 << 1)
+#define PAGE_IS_FILE (1 << 2)
+#define PAGE_IS_PRESENT (1 << 3)
+#define PAGE_IS_SWAPPED (1 << 4)
+#define PAGE_IS_PFNZERO (1 << 5)
+#define PAGE_IS_HUGE (1 << 6)
+
+/*
+ * struct page_region - Page region with flags
+ * @start: Start of the region
+ * @end: End of the region (exclusive)
+ * @categories: PAGE_IS_* category bitmask for the region
+ */
+struct page_region {
+ __u64 start;
+ __u64 end;
+ __u64 categories;
+};
+
+/* Flags for PAGEMAP_SCAN ioctl */
+#define PM_SCAN_WP_MATCHING (1 << 0) /* Write protect the pages matched. */
+#define PM_SCAN_CHECK_WPASYNC (1 << 1) /* Abort the scan when a non-WP-enabled page is found. */
+
+/*
+ * struct pm_scan_arg - Pagemap ioctl argument
+ * @size: Size of the structure
+ * @flags: Flags for the IOCTL
+ * @start: Starting address of the region
+ * @end: Ending address of the region
+ * @walk_end Address where the scan stopped (written by kernel).
+ * walk_end == end (address tags cleared) informs that the scan completed on entire range.
+ * @vec: Address of page_region struct array for output
+ * @vec_len: Length of the page_region struct array
+ * @max_pages: Optional limit for number of returned pages (0 = disabled)
+ * @category_inverted: PAGE_IS_* categories which values match if 0 instead of 1
+ * @category_mask: Skip pages for which any category doesn't match
+ * @category_anyof_mask: Skip pages for which no category matches
+ * @return_mask: PAGE_IS_* categories that are to be reported in `page_region`s returned
+ */
+struct pm_scan_arg {
+ __u64 size;
+ __u64 flags;
+ __u64 start;
+ __u64 end;
+ __u64 walk_end;
+ __u64 vec;
+ __u64 vec_len;
+ __u64 max_pages;
+ __u64 category_inverted;
+ __u64 category_mask;
+ __u64 category_anyof_mask;
+ __u64 return_mask;
+};
+
#endif /* _UAPI_LINUX_FS_H */
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7ed95353c46a7..a24eb6352d6a5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5008,7 +5008,7 @@ bool is_hugetlb_entry_migration(pte_t pte)
return false;
}
-static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
+bool is_hugetlb_entry_hwpoisoned(pte_t pte)
{
swp_entry_t swp;
--
2.40.1
