• Dave Hansen's avatar
    signals, pkeys: Notify userspace about protection key faults · cd0ea35f
    Dave Hansen authored
    A protection key fault is very similar to any other access error.
    There must be a VMA, etc...  We even want to take the same action
    (SIGSEGV) that we do with a normal access fault.
    
    However, we do need to let userspace know that something is
    different.  We do this the same way what we did with SEGV_BNDERR
    with Memory Protection eXtensions (MPX): define a new SEGV code:
    SEGV_PKUERR.
    
    We add a siginfo field: si_pkey that reveals to userspace which
    protection key was set on the PTE that we faulted on.  There is
    no other easy way for userspace to figure this out.  They could
    parse smaps but that would be a bit cruel.
    
    We share space with in siginfo with _addr_bnd.  #BR faults from
    MPX are completely separate from page faults (#PF) that trigger
    from protection key violations, so we never need both at the same
    time.
    
    Note that _pkey is a 64-bit value.  The current hardware only
    supports 4-bit protection keys.  We do this because there is
    _plenty_ of space in _sigfault and it is possible that future
    processors would support more than 4 bits of protection keys.
    
    The x86 code to actually fill in the siginfo is in the next
    patch.
    Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
    Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Amanieu d'Antras <amanieu@gmail.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Dave Hansen <dave@sr71.net>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Palmer Dabbelt <palmer@dabbelt.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Richard Weinberger <richard@nod.at>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Sasha Levin <sasha.levin@oracle.com>
    Cc: Vegard Nossum <vegard.nossum@oracle.com>
    Cc: Vladimir Davydov <vdavydov@parallels.com>
    Cc: linux-arch@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    Cc: linux-mm@kvack.org
    Link: http://lkml.kernel.org/r/20160212210212.3A9B83AC@viggo.jf.intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    cd0ea35f
signal.c 94.1 KB