UFFDIO_RWPROTECT2const

Usage

#include <linux/userfaultfd.h>  /* Definition of UFFD* constants */
#include <sys/ioctl.h>

struct uffdio_rwprotect {
    struct uffdio_range  range;  /* Range to change RWP on */
    __u64                mode;   /* Mode flags */
};

Library

Standard C library (libc, -lc)

Overview

Read-write-protect or un-protect a userfaultfd-registered memory range registered with mode UFFDIO_REGISTER_MODE_RWP.

The following mode bits are supported:

UFFDIO_RWPROTECT_MODE_RWP

When this mode bit is set, the ioctl installs read-write protection on every page present in the range specified by .range. Otherwise the ioctl removes read-write protection from the range, which is also how a fault handler resolves an UFFD_PAGEFAULT_FLAG_RWP notification.

UFFDIO_RWPROTECT_MODE_DONTWAKE

When this mode bit is set, do not wake up any thread that waits for page-fault resolution after the operation. This can be specified only if UFFDIO_RWPROTECT_MODE_RWP is not specified.

Read-write protection only affects pages that are currently populated in the range; unmapped addresses are left untouched. For anonymous mappings, protection is preserved across page reclaim (the marker rides on the swap entry) and migration. For shmem and file-backed mappings, protection is dropped when the backing page is reclaimed. Callers must also re-arm a range with UFFDIO_RWPROTECT after any operation that explicitly drops the underlying page: MADV_DONTNEED on anonymous memory, hole-punch on shmem, truncation of a file mapping.

Return value

On success, 0 is returned. On error, -1 is returned and errno is set to indicate the error.

Errors

EINVAL

The start or the len field of the uffdio_range structure was not a multiple of the system page size, or len was zero, or the specified range was otherwise invalid, or an invalid mode bit was specified, or UFFDIO_RWPROTECT_MODE_DONTWAKE was specified together with UFFDIO_RWPROTECT_MODE_RWP.

EAGAIN

The process was interrupted; retry this call.

ENOENT

The range specified in .range is not valid; for example, the virtual address does not exist, or part of the range is not registered with UFFDIO_REGISTER_MODE_RWP.

EFAULT

Encountered a generic fault during processing.

Examples

See userfaultfd(2).