• Cyrill Gorcunov's avatar
    syscalls, x86: add __NR_kcmp syscall · d97b46a6
    Cyrill Gorcunov authored
    While doing the checkpoint-restore in the user space one need to determine
    whether various kernel objects (like mm_struct-s of file_struct-s) are
    shared between tasks and restore this state.
    The 2nd step can be solved by using appropriate CLONE_ flags and the
    unshare syscall, while there's currently no ways for solving the 1st one.
    One of the ways for checking whether two tasks share e.g.  mm_struct is to
    provide some mm_struct ID of a task to its proc file, but showing such
    info considered to be not that good for security reasons.
    Thus after some debates we end up in conclusion that using that named
    'comparison' syscall might be the best candidate.  So here is it --
    It takes up to 5 arguments - the pids of the two tasks (which
    characteristics should be compared), the comparison type and (in case of
    comparison of files) two file descriptors.
    Lookups for pids are done in the caller's PID namespace only.
    At moment only x86 is supported and tested.
    [akpm@linux-foundation.org: fix up selftests, warnings]
    [akpm@linux-foundation.org: include errno.h]
    [akpm@linux-foundation.org: tweak comment text]
    Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
    Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Pavel Emelyanov <xemul@parallels.com>
    Cc: Andrey Vagin <avagin@openvz.org>
    Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Glauber Costa <glommer@parallels.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Matt Helsley <matthltc@us.ibm.com>
    Cc: Pekka Enberg <penberg@kernel.org>
    Cc: Eric Dumazet <eric.dumazet@gmail.com>
    Cc: Vasiliy Kulikov <segoon@openwall.com>
    Cc: Alexey Dobriyan <adobriyan@gmail.com>
    Cc: Valdis.Kletnieks@vt.edu
    Cc: Michal Marek <mmarek@suse.cz>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
kcmp.h 214 Bytes