PAGEMAP_SCAN(2const) PAGEMAP_SCAN(2const)
NAME
PAGEMAP_SCAN - get and/or clear page flags
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <linux/fs.h> /* Definition of PAGE* and PM_* constants */
#include <sys/ioctl.h>
int ioctl(int pagemap_fd, 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
This ioctl(2) 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) 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 pro-
tected.
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 User-
faultfd Asynchronous Write protection enabled.
The struct pm_scan_arg argument
size This field should be set to the size of the structure in bytes,
as in sizeof(struct pm_scan_arg).
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 walk_end
equal to end means that scan has completed on the entire range.
vec The address of page_region array for output.
vec_len
The length of the page_region 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 page_region.
RETURN VALUE
On error, -1 is returned, and errno is set to indicate the error.
ERRORS
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 vec_len 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
Linux.
HISTORY
Linux 6.7.
SEE ALSO
ioctl(2)
Linux man-pages 6.9.1 2024-06-17 PAGEMAP_SCAN(2const)
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