Mark switch cases where we are expecting to fall through.

This patch fixes the following warnings (Building: allmodconfig nds32):

include/math-emu/soft-fp.h:124:8: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/nds32/kernel/signal.c:362:20: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/nds32/kernel/signal.c:315:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:417:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:430:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:310:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:320:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:310:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:320:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/soft-fp.h:124:8: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:417:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:430:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:310:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:320:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:310:11: warning: this statement may fall through [-Wimplicit-fallthrough=]
include/math-emu/op-common.h:320:11: warning: this statement may fall through [-Wimplicit-fallthrough=]

Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Pull dma-mapping updates from Christoph Hellwig:

 - move the USB special case that bounced DMA through a device bar into
   the USB code instead of handling it in the common DMA code (Laurentiu
   Tudor and Fredrik Noring)

 - don't dip into the global CMA pool for single page allocations
   (Nicolin Chen)

 - fix a crash when allocating memory for the atomic pool failed during
   boot (Florian Fainelli)

 - move support for MIPS-style uncached segments to the common code and
   use that for MIPS and nios2 (me)

 - make support for DMA_ATTR_NON_CONSISTENT and
   DMA_ATTR_NO_KERNEL_MAPPING generic (me)

 - convert nds32 to the generic remapping allocator (me)

* tag 'dma-mapping-5.3' of git://git.infradead.org/users/hch/dma-mapping: (29 commits)
  dma-mapping: mark dma_alloc_need_uncached as __always_inline
  MIPS: only select ARCH_HAS_UNCACHED_SEGMENT for non-coherent platforms
  usb: host: Fix excessive alignment restriction for local memory allocations
  lib/genalloc.c: Add algorithm, align and zeroed family of DMA allocators
  nios2: use the generic uncached segment support in dma-direct
  nds32: use the generic remapping allocator for coherent DMA allocations
  arc: use the generic remapping allocator for coherent DMA allocations
  dma-direct: handle DMA_ATTR_NO_KERNEL_MAPPING in common code
  dma-direct: handle DMA_ATTR_NON_CONSISTENT in common code
  dma-mapping: add a dma_alloc_need_uncached helper
  openrisc: remove the partial DMA_ATTR_NON_CONSISTENT support
  arc: remove the partial DMA_ATTR_NON_CONSISTENT support
  arm-nommu: remove the partial DMA_ATTR_NON_CONSISTENT support
  ARM: dma-mapping: allow larger DMA mask than supported
  dma-mapping: truncate dma masks to what dma_addr_t can hold
  iommu/dma: Apply dma_{alloc,free}_contiguous functions
  dma-remap: Avoid de-referencing NULL atomic_pool
  MIPS: use the generic uncached segment support in dma-direct
  dma-direct: provide generic support for uncached kernel segments
  au1100fb: fix DMA API abuse
  ...

Pull force_sig() argument change from Eric Biederman:
 "A source of error over the years has been that force_sig has taken a
  task parameter when it is only safe to use force_sig with the current
  task.

  The force_sig function is built for delivering synchronous signals
  such as SIGSEGV where the userspace application caused a synchronous
  fault (such as a page fault) and the kernel responded with a signal.

  Because the name force_sig does not make this clear, and because the
  force_sig takes a task parameter the function force_sig has been
  abused for sending other kinds of signals over the years. Slowly those
  have been fixed when the oopses have been tracked down.

  This set of changes fixes the remaining abusers of force_sig and
  carefully rips out the task parameter from force_sig and friends
  making this kind of error almost impossible in the future"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (27 commits)
  signal/x86: Move tsk inside of CONFIG_MEMORY_FAILURE in do_sigbus
  signal: Remove the signal number and task parameters from force_sig_info
  signal: Factor force_sig_info_to_task out of force_sig_info
  signal: Generate the siginfo in force_sig
  signal: Move the computation of force into send_signal and correct it.
  signal: Properly set TRACE_SIGNAL_LOSE_INFO in __send_signal
  signal: Remove the task parameter from force_sig_fault
  signal: Use force_sig_fault_to_task for the two calls that don't deliver to current
  signal: Explicitly call force_sig_fault on current
  signal/unicore32: Remove tsk parameter from __do_user_fault
  signal/arm: Remove tsk parameter from __do_user_fault
  signal/arm: Remove tsk parameter from ptrace_break
  signal/nds32: Remove tsk parameter from send_sigtrap
  signal/riscv: Remove tsk parameter from do_trap
  signal/sh: Remove tsk parameter from force_sig_info_fault
  signal/um: Remove task parameter from send_sigtrap
  signal/x86: Remove task parameter from send_sigtrap
  signal: Remove task parameter from force_sig_mceerr
  signal: Remove task parameter from force_sig
  signal: Remove task parameter from force_sigsegv
  ...

Replace the code that sets up uncached PTEs with the generic vmap based
remapping code.  It also provides an atomic pool for allocations from
non-blocking context, which we not properly supported by the existing
nds32 code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Greentime Hu <greentime@andestech.com>
Reviewed-by: Greentime Hu <greentime@andestech.com>

Pull nds32 fixes from Greentime Hu:

 - fix warning for math-emu

 - fix nds32 fpu exception handling

 - fix nds32 fpu emulation implementation

* tag 'nds32-for-linux-5.2-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/greentime/linux:
  nds32: add new emulations for floating point instruction
  nds32: Avoid IEX status being incorrectly modified
  math-emu: Use statement expressions to fix Wshift-count-overflow warning

In order for kernel to capture each denormalized output, the UDF
trapping enable bit is always raised in $fpcsr. Because underflow case will
issue not an underflow exception but also an inexact exception, it causes
that the IEX, IEX cumulative exception, flag in $fpcsr to be raised in each
denormalized output handling. To make the emulation transparent to the
user, the emulator needs to clear the IEX flag in $fpcsr if the result is a
denormalized number. However, if the IEX flag has been raised before this
floating point emulation, this cleanup may be incorrect. To avoid the IEX
flags in $fpcsr be raised in each denormalized output handling, the IEX
trap shall be always enabled.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

As synchronous exceptions really only make sense against the current
task (otherwise how are you synchronous) remove the task parameter
from from force_sig_fault to make it explicit that is what is going
on.

The two known exceptions that deliver a synchronous exception to a
stopped ptraced task have already been changed to
force_sig_fault_to_task.

The callers have been changed with the following emacs regular expression
(with obvious variations on the architectures that take more arguments)
to avoid typos:

force_sig_fault[(]\([^,]+\)[,]\([^,]+\)[,]\([^,]+\)[,]\W+current[)]
->
force_sig_fault(\1,\2,\3)

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Update the calls of force_sig_fault that pass in a variable that is
set to current earlier to explicitly use current.

This is to make the next change that removes the task parameter
from force_sig_fault easier to verify.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

The send_sigtrap function is always called with tsk == current.
Make that obvious by removing the tsk parameter.

This also makes it clear that send_sigtrap always calls
force_sig_fault on the current task.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

All of the remaining callers pass current into force_sig so
remove the task parameter to make this obvious and to make
misuse more difficult in the future.

This also makes it clear force_sig passes current into force_sig_info.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>