From 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Mon, 6 Apr 2020 20:06:12 -0700 Subject: userfaultfd: wp: add the writeprotect API to userfaultfd ioctl Introduce the new uffd-wp APIs for userspace. Firstly, we'll allow to do UFFDIO_REGISTER with write protection tracking using the new UFFDIO_REGISTER_MODE_WP flag. Note that this flag can co-exist with the existing UFFDIO_REGISTER_MODE_MISSING, in which case the userspace program can not only resolve missing page faults, and at the same time tracking page data changes along the way. Secondly, we introduced the new UFFDIO_WRITEPROTECT API to do page level write protection tracking. Note that we will need to register the memory region with UFFDIO_REGISTER_MODE_WP before that. [peterx@redhat.com: write up the commit message] [peterx@redhat.com: remove useless block, write commit message, check against VM_MAYWRITE rather than VM_WRITE when register] Signed-off-by: Andrea Arcangeli Signed-off-by: Peter Xu Signed-off-by: Andrew Morton Reviewed-by: Jerome Glisse Cc: Bobby Powers Cc: Brian Geffon Cc: David Hildenbrand Cc: Denis Plotnikov Cc: "Dr . David Alan Gilbert" Cc: Hugh Dickins Cc: Johannes Weiner Cc: "Kirill A . Shutemov" Cc: Martin Cracauer Cc: Marty McFadden Cc: Maya Gokhale Cc: Mel Gorman Cc: Mike Kravetz Cc: Mike Rapoport Cc: Pavel Emelyanov Cc: Rik van Riel Cc: Shaohua Li Link: http://lkml.kernel.org/r/20200220163112.11409-14-peterx@redhat.com Signed-off-by: Linus Torvalds --- include/uapi/linux/userfaultfd.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'include/uapi') diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 340f23bc251d..95c4a160e5f8 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -52,6 +52,7 @@ #define _UFFDIO_WAKE (0x02) #define _UFFDIO_COPY (0x03) #define _UFFDIO_ZEROPAGE (0x04) +#define _UFFDIO_WRITEPROTECT (0x06) #define _UFFDIO_API (0x3F) /* userfaultfd ioctl ids */ @@ -68,6 +69,8 @@ struct uffdio_copy) #define UFFDIO_ZEROPAGE _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \ struct uffdio_zeropage) +#define UFFDIO_WRITEPROTECT _IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \ + struct uffdio_writeprotect) /* read() structure */ struct uffd_msg { @@ -232,4 +235,24 @@ struct uffdio_zeropage { __s64 zeropage; }; +struct uffdio_writeprotect { + struct uffdio_range range; +/* + * UFFDIO_WRITEPROTECT_MODE_WP: set the flag to write protect a range, + * unset the flag to undo protection of a range which was previously + * write protected. + * + * UFFDIO_WRITEPROTECT_MODE_DONTWAKE: set the flag to avoid waking up + * any wait thread after the operation succeeds. + * + * NOTE: Write protecting a region (WP=1) is unrelated to page faults, + * therefore DONTWAKE flag is meaningless with WP=1. Removing write + * protection (WP=0) in response to a page fault wakes the faulting + * task unless DONTWAKE is set. + */ +#define UFFDIO_WRITEPROTECT_MODE_WP ((__u64)1<<0) +#define UFFDIO_WRITEPROTECT_MODE_DONTWAKE ((__u64)1<<1) + __u64 mode; +}; + #endif /* _LINUX_USERFAULTFD_H */ -- cgit v1.2.3