userfaultfd: buildsystem activation

This allows to select the userfaultfd during configuration to build it.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Pavel Emelyanov <xemul@parallels.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>

2 files changed, 12 insertions, 0 deletions

diff --git a/fs/Makefile b/fs/Makefile
index 09e051fefc5b..f79cf4043e60 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_ANON_INODES)	+= anon_inodes.o
 obj-$(CONFIG_SIGNALFD)          += signalfd.o
 obj-$(CONFIG_TIMERFD)           += timerfd.o
 obj-$(CONFIG_EVENTFD)           += eventfd.o
+obj-$(CONFIG_USERFAULTFD)       += userfaultfd.o
 obj-$(CONFIG_AIO)               += aio.o
 obj-$(CONFIG_FS_DAX)            += dax.o
 obj-$(CONFIG_FILE_LOCKING)      += locks.o
diff --git a/init/Kconfig b/init/Kconfig
index bb9b4dd55889..161acd8bc56f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1576,6 +1576,17 @@ config ADVISE_SYSCALLS
           applications use these syscalls, you can disable this option to save
           space.
 
+config USERFAULTFD
+        bool "Enable userfaultfd() system call"
+        select ANON_INODES
+        default y
+        depends on MMU
+        help
+          Enable the userfaultfd() system call that allows to intercept and
+          handle page faults in userland.
+
+          If unsure, say Y.
+
 config PCI_QUIRKS
         default y
         bool "Enable PCI quirk workarounds" if EXPERT