PAGEMAP_SCAN(2const) - Linux manual page (original) (raw)

PAGEMAPSCAN(2const) PAGEMAPSCAN(2const)

NAME top

   PAGEMAP_SCAN - get and/or clear page flags

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <linux/fs.h>** /* Definition of **PAGE*** and **PM_*** constants */
   **#include <sys/ioctl.h>**

   **int ioctl(int** _pagemapfd_**, PAGEMAP_SCAN, struct pm_scan_arg ***_arg_**);**

   **#include <linux/fs.h>**

   **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;**
   **};**

   **struct page_region {**
       **__u64  start;**
       **__u64  end;**
       **__u64  categories;**
   **};**

DESCRIPTION top

   This [ioctl(2)](../man2/ioctl.2.html) is used to get and optionally clear some specific
   flags from page table entries.  The information is returned with
   **PAGE_SIZE** granularity.

   To start tracking the written state (flag) of a page or range of
   memory, the **UFFD_FEATURE_WP_ASYNC** must be enabled by **UFFDIO_API**
   [ioctl(2)](../man2/ioctl.2.html) on **userfaultfd** and memory range must be registered with
   **UFFDIO_REGISTER ioctl**(2) in **UFFDIO_REGISTER_MODE_WP** mode.

Supported page flags The following page table entry flags are supported:

   **PAGE_IS_WPALLOWED**
          The page has asynchronous write-protection enabled.

   **PAGE_IS_WRITTEN**
          The page has been written to from the time it was write
          protected.

   **PAGE_IS_FILE**
          The page is file backed.

   **PAGE_IS_PRESENT**
          The page is present in the memory.

   **PAGE_IS_SWAPPED**
          The page is swapped.

   **PAGE_IS_PFNZERO**
          The page has zero PFN.

   **PAGE_IS_HUGE**
          The page is THP or Hugetlb backed.

Supported operations The get operation is always performed if the output buffer is specified. The other operations are as following:

   **PM_SCAN_WP_MATCHING**
          Write protect the matched pages.

   **PM_SCAN_CHECK_WPASYNC**
          Abort the scan when a page is found which doesn't have the
          Userfaultfd Asynchronous Write protection enabled.

The struct pmscanarg argument size This field should be set to the size of the structure in bytes, as in sizeof(struct pmscanarg).

   **flags** The operations to be performed are specified in it.

   **start** The starting address of the scan is specified in it.

   **end** The ending address of the scan is specified in it.

   **walk_end**
          The kernel returns the scan's ending address in it.  The
          _walkend_ equal to _end_ means that scan has completed on the
          entire range.

   **vec** The address of _pageregion_ array for output.

   **vec_len**
          The length of the _pageregion_ struct array.

   **max_pages**
          It is the optional limit for the number of output pages
          required.

   **category_inverted**
          **PAGE_IS_**_*_ categories which values match if 0 instead of 1.

   **category_mask**
          Skip pages for which any **PAGE_IS_**_*_ category doesn't match.

   **category_anyof_mask**
          Skip pages for which no **PAGE_IS_**_*_ category matches.

   **return_mask**
          **PAGE_IS_**_*_ categories that are to be reported in
          _pageregion_.

RETURN VALUE top

   On error, -1 is returned, and _[errno](../man3/errno.3.html)_ is set to indicate the error.

ERRORS top

   Error codes can be one of, but are not limited to, the following:

   **EINVAL** Invalid arguments i.e., invalid _size_ of the argument,
          invalid _flags_, invalid _categories_, the _start_ address isn't
          aligned with **PAGE_SIZE**, or _veclen_ is specified when _vec_ is
          NULL.

   **EFAULT** Invalid _arg_ pointer, invalid _vec_ pointer, or invalid
          address range specified by _start_ and _end_.

   **ENOMEM** No memory is available.

   **EINTR** Fetal signal is pending.

STANDARDS top

   Linux.

HISTORY top

   Linux 6.7.

SEE ALSO top

   [ioctl(2)](../man2/ioctl.2.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 PAGEMAPSCAN(2const)

Pages that refer to this page:ioctl_fs(2)