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userfaultfd: Rename uffd_api.bits into .features

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This is (seems to be) the minimal thing that is required to unblock
standard uffd usage from the non-cooperative one.  Now more bits can be
added to the features field indicating e.g.  UFFD_FEATURE_FORK and others
needed for the latter use-case.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
Cc: zhang.zhanghailiang@huawei.com
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pavel Emelyanov 2015-09-04 15:46:34 -07:00 committed by Linus Torvalds
parent 86039bd3b4
commit 3f602d2724
2 changed files with 11 additions and 5 deletions
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4
fs/userfaultfd.c
View File

@ -884,7 +884,7 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
goto out;
}
/* careful not to leak info, we only read the first 8 bytes */
uffdio_api.bits = UFFD_API_BITS;
uffdio_api.features = UFFD_API_FEATURES;
uffdio_api.ioctls = UFFD_API_IOCTLS;
ret = -EFAULT;
if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
@ -941,7 +941,7 @@ static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
* protocols: aa:... bb:...
*/
seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
pending, total, UFFD_API, UFFD_API_BITS,
pending, total, UFFD_API, UFFD_API_FEATURES,
UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
}
#endif

12
include/uapi/linux/userfaultfd.h
View File

@ -12,8 +12,8 @@
#include <linux/types.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)
/* FIXME: add "|UFFD_FEATURE_WP" to UFFD_API_FEATURES after implementing it */
#define UFFD_API_FEATURES (UFFD_FEATURE_WRITE_BIT)
#define UFFD_API_IOCTLS \
((__u64)1 << _UFFDIO_REGISTER | \
(__u64)1 << _UFFDIO_UNREGISTER | \
@ -53,12 +53,18 @@
#define UFFD_BIT_WP (1<<1) /* handle_userfault() reason VM_UFFD_WP */
#define UFFD_BITS 2 /* two above bits used for UFFD_BIT_* mask */
/*
* Features reported in uffdio_api.features field
*/
#define UFFD_FEATURE_WRITE_BIT (1<<0) /* Corresponds to UFFD_BIT_WRITE */
#define UFFD_FEATURE_WP_BIT (1<<1) /* Corresponds to UFFD_BIT_WP */
struct uffdio_api {
/* userland asks for an API number */
__u64 api;
/* kernel answers below with the available features for the API */
__u64 bits;
__u64 features;
__u64 ioctls;
};