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    Subject[PATCH 03/21] userfaultfd: uAPI
    Date
    Defines the uAPI of the userfaultfd, notably the ioctl numbers and protocol.

    Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
    ---
    Documentation/ioctl/ioctl-number.txt | 1 +
    include/uapi/linux/userfaultfd.h | 81 ++++++++++++++++++++++++++++++++++++
    2 files changed, 82 insertions(+)
    create mode 100644 include/uapi/linux/userfaultfd.h

    diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
    index 8136e1f..be2d4a2 100644
    --- a/Documentation/ioctl/ioctl-number.txt
    +++ b/Documentation/ioctl/ioctl-number.txt
    @@ -301,6 +301,7 @@ Code Seq#(hex) Include File Comments
    0xA3 80-8F Port ACL in development:
    <mailto:tlewis@mindspring.com>
    0xA3 90-9F linux/dtlk.h
    +0xAA 00-3F linux/uapi/linux/userfaultfd.h
    0xAB 00-1F linux/nbd.h
    0xAC 00-1F linux/raw.h
    0xAD 00 Netfilter device in development:
    diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
    new file mode 100644
    index 0000000..9a8cd56
    --- /dev/null
    +++ b/include/uapi/linux/userfaultfd.h
    @@ -0,0 +1,81 @@
    +/*
    + * include/linux/userfaultfd.h
    + *
    + * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
    + * Copyright (C) 2015 Red Hat, Inc.
    + *
    + */
    +
    +#ifndef _LINUX_USERFAULTFD_H
    +#define _LINUX_USERFAULTFD_H
    +
    +#define UFFD_API ((__u64)0xAA)
    +/* FIXME: add "|UFFD_BIT_WP" to UFFD_API_BITS after implementing it */
    +#define UFFD_API_BITS (UFFD_BIT_WRITE)
    +#define UFFD_API_IOCTLS \
    + ((__u64)1 << _UFFDIO_REGISTER | \
    + (__u64)1 << _UFFDIO_UNREGISTER | \
    + (__u64)1 << _UFFDIO_API)
    +#define UFFD_API_RANGE_IOCTLS \
    + ((__u64)1 << _UFFDIO_WAKE)
    +
    +/*
    + * Valid ioctl command number range with this API is from 0x00 to
    + * 0x3F. UFFDIO_API is the fixed number, everything else can be
    + * changed by implementing a different UFFD_API. If sticking to the
    + * same UFFD_API more ioctl can be added and userland will be aware of
    + * which ioctl the running kernel implements through the ioctl command
    + * bitmask written by the UFFDIO_API.
    + */
    +#define _UFFDIO_REGISTER (0x00)
    +#define _UFFDIO_UNREGISTER (0x01)
    +#define _UFFDIO_WAKE (0x02)
    +#define _UFFDIO_API (0x3F)
    +
    +/* userfaultfd ioctl ids */
    +#define UFFDIO 0xAA
    +#define UFFDIO_API _IOWR(UFFDIO, _UFFDIO_API, \
    + struct uffdio_api)
    +#define UFFDIO_REGISTER _IOWR(UFFDIO, _UFFDIO_REGISTER, \
    + struct uffdio_register)
    +#define UFFDIO_UNREGISTER _IOR(UFFDIO, _UFFDIO_UNREGISTER, \
    + struct uffdio_range)
    +#define UFFDIO_WAKE _IOR(UFFDIO, _UFFDIO_WAKE, \
    + struct uffdio_range)
    +
    +/*
    + * Valid bits below PAGE_SHIFT in the userfault address read through
    + * the read() syscall.
    + */
    +#define UFFD_BIT_WRITE (1<<0) /* this was a write fault, MISSING or WP */
    +#define UFFD_BIT_WP (1<<1) /* handle_userfault() reason VM_UFFD_WP */
    +#define UFFD_BITS 2 /* two above bits used for UFFD_BIT_* mask */
    +
    +struct uffdio_api {
    + /* userland asks for an API number */
    + __u64 api;
    +
    + /* kernel answers below with the available features for the API */
    + __u64 bits;
    + __u64 ioctls;
    +};
    +
    +struct uffdio_range {
    + __u64 start;
    + __u64 len;
    +};
    +
    +struct uffdio_register {
    + struct uffdio_range range;
    +#define UFFDIO_REGISTER_MODE_MISSING ((__u64)1<<0)
    +#define UFFDIO_REGISTER_MODE_WP ((__u64)1<<1)
    + __u64 mode;
    +
    + /*
    + * kernel answers which ioctl commands are available for the
    + * range, keep at the end as the last 8 bytes aren't read.
    + */
    + __u64 ioctls;
    +};
    +
    +#endif /* _LINUX_USERFAULTFD_H */

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