x86: uaccess hardening, easy part

This series hardens x86's uaccess code a bit.  It adds warnings for
some screwups, adds an OOPS for a major exploitable screwup, and it
improves debuggability a bit by indicating non-default fs in oopses.

It shouldn't cause any new OOPSes except in the particularly
dangerous case where the kernel faults on a kernel address under
USER_DS, which indicates that an access_ok is missing and is likely
to be easily exploitable -- OOPSing will make it harder to exploit.

I have some draft patches to force OOPSes on user address accesses
under KERNEL_DS (which is a big no-no), but I'd rather make those
warn instead of OOPSing, and I don't have a good implementation of
that yet.  Those patches aren't part of this series.

Andy Lutomirski (7):
  x86/xen: Simplify set_aliased_prot
  x86/extable: Pass error_code and an extra unsigned long to exhandlers
  x86/uaccess: Give uaccess faults their own handler
  x86/dumpstack: If addr_limit is non-default, display it
  x86/uaccess: Warn on uaccess faults other than #PF
  x86/uaccess: Don't fix up USER_DS uaccess faults to kernel addresses
  x86/uaccess: OOPS or warn on a fault with KERNEL_DS and
    !pagefault_disabled()

 arch/x86/include/asm/uaccess.h   |  19 ++++---
 arch/x86/kernel/cpu/mcheck/mce.c |   2 +-
 arch/x86/kernel/dumpstack_32.c   |   4 ++
 arch/x86/kernel/dumpstack_64.c   |   5 ++
 arch/x86/kernel/kprobes/core.c   |   6 +-
 arch/x86/kernel/traps.c          |   6 +-
 arch/x86/lib/getuser.S           |  12 ++--
 arch/x86/lib/putuser.S           |  10 ++--
 arch/x86/mm/extable.c            | 120 ++++++++++++++++++++++++++++++++++-----
 arch/x86/mm/fault.c              |   2 +-
 arch/x86/xen/enlighten.c         |   4 +-
 11 files changed, 145 insertions(+), 45 deletions(-)

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2.5.5