The current machine check code uses the registers stored by the machine
in the lowcore at __LC_GPREGS_SAVE_AREA as the registers of the interrupted
context. The registers 0-7 of a user process can get clobbered if a machine
checks interrupts the execution of a critical section in entry[64].S.

The reason is that the critical section cleanup code may need to modify
the PSW and the registers for the previous context to get to the end of a
critical section. If registers 0-7 have to be replaced the relevant copy
will be in the registers, which invalidates the copy in the lowcore. The
machine check handler needs to explicitly store registers 0-7 to the stack.

Cc: stable@vger.kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Pull s390 update from Martin Schwidefsky:
 "Add support to generate code for the latest machine zEC12, MOD and XOR
  instruction support for the BPF jit compiler, the dasd safe offline
  feature and the big one: the s390 architecture gets PCI support!!
  Right before the world ends on the 21st ;-)"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (41 commits)
  s390/qdio: rename the misleading PCI flag of qdio devices
  s390/pci: remove obsolete email addresses
  s390/pci: speed up __iowrite64_copy by using pci store block insn
  s390/pci: enable NEED_DMA_MAP_STATE
  s390/pci: no msleep in potential IRQ context
  s390/pci: fix potential NULL pointer dereference in dma_free_seg_table()
  s390/pci: use kmem_cache_zalloc instead of kmem_cache_alloc/memset
  s390/bpf,jit: add support for XOR instruction
  s390/bpf,jit: add support MOD instruction
  s390/cio: fix pgid reserved check
  vga: compile fix, disable vga for s390
  s390/pci: add PCI Kconfig options
  s390/pci: s390 specific PCI sysfs attributes
  s390/pci: PCI hotplug support via SCLP
  s390/pci: CHSC PCI support for error and availability events
  s390/pci: DMA support
  s390/pci: PCI adapter interrupts for MSI/MSI-X
  s390/bitops: find leftmost bit instruction support
  s390/pci: CLP interface
  s390/pci: base support
  ...

The current single step code is racy in regard to concurrent delivery
of signals. If a signal is delivered after a PER program check occurred
but before the TIF_PER_TRAP bit has been checked in entry[64].S the code
clears TIF_PER_TRAP and then calls do_signal. This is wrong, if the
instruction completed (or has been suppressed) a SIGTRAP should be
delivered to the debugger in any case. Only if the instruction has been
nullified the SIGTRAP may not be send.

The new logic always sets TIF_PER_TRAP if the program check indicates PER
tracing but removes it again for all program checks that are nullifying.
The effect is that for each change in the PSW address we now get a
single SIGTRAP.

Reported-by: Andreas Arnez <arnez@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

same situation as with alpha and arm - only massage needed

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

... and don't bother with syscall return path in case of kernel
threads.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

The current virtual timer interface is inherently per-cpu and hard to
use. The sole user of the interface is appldata which uses it to execute
a function after a specific amount of cputime has been used over all cpus.

Rework the virtual timer interface to hook into the cputime accounting.
This makes the interface independent from the CPU timer interrupts, and
makes the virtual timers global as opposed to per-cpu.
Overall the code is greatly simplified. The downside is that the accuracy
is not as good as the original implementation, but it is still good enough
for appldata.

Reviewed-by: Jan Glauber <jang@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Remove the file name from the comment at top of many files. In most
cases the file name was wrong anyway, so it's rather pointless.

Also unify the IBM copyright statement. We did have a lot of sightly
different statements and wanted to change them one after another
whenever a file gets touched. However that never happened. Instead
people start to take the old/"wrong" statements to use as a template
for new files.
So unify all of them in one go.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

Setting the cpu restart parameters is done in three different fashions:
- directly setting the four parameters individually
- copying the four parameters with memcpy (using 4 * sizeof(long))
- copying the four parameters using a private structure

In addition code in entry*.S relies on a certain order of the restart
members of struct _lowcore.

Make all of this more robust to future changes by adding a
mem_absolute_assign(dest, val) define, which assigns val to dest
using absolute addressing mode. Also the load multiple instructions
in entry*.S have been split into separate load instruction so the
order of the struct _lowcore members doesn't matter anymore.

In addition move the prototypes of memcpy_real/absolute from uaccess.h
to processor.h. These memcpy* variants are not related to uaccess at all.
string.h doesn't seem to match as well, so lets use processor.h.

Also replace the eight byte array in struct _lowcore which represents a
misaliged u64 with a u64. The compiler will always create code that
handles the misaligned u64 correctly.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>