The function do_trap_no_signal embodies almost all of the work of the
function do_trap.  The exceptions are setting of thread.error_code and
thread.trap_nr in the case when the signal will be sent, and reporting
which signal will be sent with show_signal.

Filling in struct siginfo and then calling do_trap is problematic as
filling in struct siginfo is an fiddly process that can through
inattention has resulted in fields not initialized and the wrong
fields being filled in.

To avoid this error prone situation I am replacing force_sig_info with
a set of functions that take as arguments the information needed to
send a specific kind of signal.

The function do_trap is called in the context of several different
kinds of signals today.  Having a solid do_trap_no_signal that
can be reused allows call sites that send different kinds of
signals to reuse all of the code in do_trap_no_signal.

Modify do_trap_no_signal to have a single exit there signals
where be sent (aka returning -1) to allow more of the signal
sending path to be moved to from do_trap to do_trap_no_signal.

Move setting thread.trap_nr and thread.error_code into do_trap_no_signal
so the code does not need to be duplicated.

Make the type of the string that is passed into do_trap_no_signal to
const.  The only user of that str is die and it already takes a const
string, so this just makes it explicit that the string won't change.

All of this prepares the way for using do_trap_no_signal outside
of do_trap.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The code for conditionally printing unhanded signals is duplicated twice
in arch/x86/kernel/traps.c.  Factor it out into it's own subroutine
called show_signal to make the code clearer and easier to maintain.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

This separates the logic of generating the signal from the logic of
gathering the information about the bounds violation.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The value passed in to addr_referenced is of type void __user *, so update
the addr_referenced parameter in trace_mpx_bounds_register_exception to match.

Also update the addr_referenced paramater in TP_STRUCT__entry as it again
holdes the same value.

I don't know why this was missed earlier but sparse was complaining when
testing test branch so fix this now.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

This simplifies the code making it clearer what is going on.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Only the call from do_sigbus will send SIGBUS due to a memory machine
check error.  Consolidate all of the machine check signal generation
code in do_sigbus and remove the now unnecessary fault parameter from
force_sig_info_fault.

Explicitly use the now constant si_code BUS_ADRERR in the call
to force_sig_info_fault from do_sigbus.

This makes the code in arch/x86/mm/fault.c easier to follower and
simpler to maintain.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The function fill_sigtrap_info now only has one caller so remove
it and put it's contents in it's caller.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Replace user_single_step_siginfo with user_single_step_report
that allocates siginfo structure on the stack and sends it.

This allows tracehook_report_syscall_exit to become a simple
if statement that calls user_single_step_report or ptrace_report_syscall
depending on the value of step.

Update the default helper function now called user_single_step_report
to explicitly set si_code to SI_USER and to set si_uid and si_pid to 0.
The default helper has always been doing this (using memset) but it
was far from obvious.

The powerpc helper can now just call force_sig_fault.
The x86 helper can now just call send_sigtrap.

Unfortunately the default implementation of user_single_step_report
can not use force_sig_fault as it does not use a SIGTRAP si_code.
So it has to carefully setup the siginfo and use use force_sig_info.

The net result is code that is easier to understand and simpler
to maintain.

Ref: 85ec7fd9 ("ptrace: introduce user_single_step_siginfo() helper")
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

For readability and consistency with the other exports in
kernel/signal.c pair the exports of signal sending functions with
their functions, instead of having the exports in one big clump.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

This function is static and it only has two callers.  As
specific_send_sig_info is only called twice remembering what
specific_send_sig_info does when reading the code is difficutl and it
makes it hard to see which sending sending functions are equivalent to
which others.

So remove specific_send_sig_info to make the code easier to read.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Replace send_sig_info in zap_pid_ns_processes with
group_send_sig_info.  This makes more sense as the entire process
group is being killed.  More importantly this allows the kill of those
processes with PIDTYPE_MAX to indicate all of the process in the pid
namespace are being signaled.  This is needed for fork to detect when
signals are sent to a group of processes.

Admittedly fork has another case to catch SIGKILL but the principle remains
that it is desirable to know when a group of processes is being signaled.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Replace send_sig and force_sig in __do_SAK with group_send_sig_info
the general helper for sending a signal to a process group.  This is
wordier but it allows specifying PIDTYPE_SID so that the signal code
knows the signal went to a session.

Both force_sig() and send_sig(..., 1) specify SEND_SIG_PRIV and the
new call of group_send_sig_info does that explicitly.  This is enough
to ensure even a pid namespace init is killed.

The global init remains unkillable.  The guarantee that __do_SAK tries
to provide is a clean path to login to a machine.  As the global init is
unkillable, if it chooses to hold open a tty it can violate this
guarantee.  A technique other than killing processes would be needed
to provide this guarantee to userspace.

The only difference between force_sig and send_sig when sending
SIGKILL is that SIGNAL_UNKILLABLE is cleared.  This has no affect on
the processing of a signal sent with SEND_SIG_PRIV by any process, making
it unnecessary, and not behavior that needs to be preserved.

force_sig was used originally because it did not take as many locks as
send_sig.  Today send_sig, force_sig and group_send_sig_info take the
same locks when delivering a signal.

group_send_sig_info also contains a permission check that force_sig
and send_sig do not.  However the presence of SEND_SIG_PRIV makes the
permission check a noop.  So the permission check does not result
in any behavioral differences.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The genweq_add_file and genwqe_del_file by caching current without
using reference counting embed the assumption that a file descriptor
will never be passed from one process to another.  It even embeds the
assumption that the the thread that opened the file will be in
existence when the process terminates.   Neither of which are
guaranteed to be true.

Therefore replace caching the task_struct of the opener with
pid of the openers thread group id.  All the knowledge of the
opener is used for is as the target of SIGKILL and a SIGKILL
will kill the entire process group.

Rename genwqe_force_sig to genwqe_terminate, remove it's unncessary
signal argument, update it's ownly caller, and use kill_pid
instead of force_sig.

The work force_sig does in changing signal handling state is not
relevant to SIGKILL sent as SEND_SIG_PRIV.  The exact same processess
will be killed just with less work, and less confusion.  The work done
by force_sig is really only needed for handling syncrhonous
exceptions.

It will still be possible to cause genwqe_device_remove to wait
8 seconds by passing a file descriptor to another process but
the possible user after free is fixed.

Fixes: eaf4722d ("GenWQE Character device and DDCB queue")
Cc: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Frank Haverkamp <haver@linux.vnet.ibm.com>
Cc: Joerg-Stephan Vogt <jsvogt@de.ibm.com>
Cc: Michael Jung <mijung@gmx.net>
Cc: Michael Ruettger <michael@ibmra.de>
Cc: Kleber Sacilotto de Souza <klebers@linux.vnet.ibm.com>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Eberhard S. Amann <esa@linux.vnet.ibm.com>
Cc: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Cc: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

There are no more users of SEND_SIG_FORCED so it may be safely removed.

Remove the definition of SEND_SIG_FORCED, it's use in is_si_special,
it's use in TP_STORE_SIGINFO, and it's use in __send_signal as without
any users the uses of SEND_SIG_FORCED are now unncessary.

This makes the code simpler, easier to understand and use.  Users of
signal sending functions now no longer need to ask themselves do I
need to use SEND_SIG_FORCED.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Now that siginfo is never allocated for SIGKILL and SIGSTOP there is
no difference between SEND_SIG_PRIV and SEND_SIG_FORCED for SIGKILL
and SIGSTOP.  This makes SEND_SIG_FORCED unnecessary and redundant in
the presence of SIGKILL and SIGSTOP.  Therefore change users of
SEND_SIG_FORCED that are sending SIGKILL or SIGSTOP to use
SEND_SIG_PRIV instead.

This removes the last users of SEND_SIG_FORCED.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

The SIGKILL and SIGSTOP signals are never delivered to userspace so
queued siginfo for these signals can never be observed.  Therefore
remove the chance of failure by never even attempting to allocate
siginfo in those cases.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Today kernel threads never dequeue siginfo so it is pointless to
enqueue siginfo for them.  The usb gadget mass storage driver goes
one farther and uses SEND_SIG_FORCED to guarantee that no siginfo is
even enqueued.

Generalize the optimization of the usb mass storage driver and never
perform an unnecessary allocation when delivering signals to kthreads.

Switch the mass storage driver from sending signals with
SEND_SIG_FORCED to SEND_SIG_PRIV.  As using SEND_SIG_FORCED is now
unnecessary.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

None of the callers use the it so remove it.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Now that send_signal always delivers SEND_SIG_PRIV signals to a pid
namespace init it is no longer necessary to use SEND_SIG_FORCED when
calling do_send_sig_info to ensure that pid namespace inits are
signaled and possibly killed.  Using SEND_SIG_PRIV is sufficient.

So use SEND_SIG_PRIV so that userspace when it receives a SIGTERM can
tell that the kernel sent the signal and not some random userspace
application.

Fixes: b82c3287 ("sysrq: use SEND_SIG_FORCED instead of force_sig()")
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Instead of playing whack-a-mole and changing SEND_SIG_PRIV to
SEND_SIG_FORCED throughout the kernel to ensure a pid namespace init
gets signals sent by the kernel, stop allowing a pid namespace init to
ignore SIGKILL or SIGSTOP sent by the kernel.  A pid namespace init is
only supposed to be able to ignore signals sent from itself and
children with SIG_DFL.

Fixes: 921cf9f6 ("signals: protect cinit from unblocked SIG_DFL signals")
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

For userspace to tell the difference between an random signal
and an exception, the exception must include siginfo information.

Using SEND_SIG_FORCED for SIGSEGV is thus wrong, and it will result in
userspace seeing si_code == SI_USER (like a random signal) instead of
si_code == SI_KERNEL or a more specific si_code as all exceptions
deliver.

Therefore replace force_sig_info(SIGSEGV, SEND_SIG_FORCE, current)
with force_sig(SIG_SEGV, current) which gets this right and is shorter
and easier to type.

Fixes: 791eca10 ("uretprobes/x86: Hijack return address")
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

For userspace to tell the difference between a random signal and an
exception, the exception must include siginfo information.

Using SEND_SIG_FORCED for SIGILL is thus wrong, and it will result
in userspace seeing si_code == SI_USER (like a random signal) instead
of si_code == SI_KERNEL or a more specific si_code as all exceptions
deliver.

Therefore replace force_sig_info(SIGILL, SEND_SIG_FORCE, current)
with force_sig(SIG_ILL, current) which gets this right and is
shorter and easier to type.

Fixes: 014940ba ("uprobes/x86: Send SIGILL if arch_uprobe_post_xol() fails")
Fixes: 0b5256c7 ("uprobes: Send SIGILL if handle_trampoline() fails")
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

If the first process started (aka /sbin/init) receives a SIGKILL it
will panic the system if it is delivered.  Making the system unusable
and undebugable.  It isn't much better if the first process started
receives SIGSTOP.

So always ignore SIGSTOP and SIGKILL sent to init.

This is done in a separate clause in sig_task_ignored as force_sig_info
can clear SIG_UNKILLABLE and this protection should work even then.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Pull timer update from Thomas Gleixner:
 "New defines for the compat time* types so they can be shared between
  32bit and 64bit builds. Not used yet, but merging them now allows the
  actual conversions to be merged through different maintainer trees
  without dependencies

  We still have compat interfaces for 32bit on 64bit even with the new
  2038 safe timespec/val variants because pointer size is different. And
  for the old style timespec/val interfaces we need yet another 'compat'
  interface for both 32bit native and 32bit on 64bit"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  y2038: Provide aliases for compat helpers

Pull IDA updates from Matthew Wilcox:
 "A better IDA API:

      id = ida_alloc(ida, GFP_xxx);
      ida_free(ida, id);

  rather than the cumbersome ida_simple_get(), ida_simple_remove().

  The new IDA API is similar to ida_simple_get() but better named.  The
  internal restructuring of the IDA code removes the bitmap
  preallocation nonsense.

  I hope the net -200 lines of code is convincing"

* 'ida-4.19' of git://git.infradead.org/users/willy/linux-dax: (29 commits)
  ida: Change ida_get_new_above to return the id
  ida: Remove old API
  test_ida: check_ida_destroy and check_ida_alloc
  test_ida: Convert check_ida_conv to new API
  test_ida: Move ida_check_max
  test_ida: Move ida_check_leaf
  idr-test: Convert ida_check_nomem to new API
  ida: Start new test_ida module
  target/iscsi: Allocate session IDs from an IDA
  iscsi target: fix session creation failure handling
  drm/vmwgfx: Convert to new IDA API
  dmaengine: Convert to new IDA API
  ppc: Convert vas ID allocation to new IDA API
  media: Convert entity ID allocation to new IDA API
  ppc: Convert mmu context allocation to new IDA API
  Convert net_namespace to new IDA API
  cb710: Convert to new IDA API
  rsxx: Convert to new IDA API
  osd: Convert to new IDA API
  sd: Convert to new IDA API
  ...

Pull gcc plugin fix from Kees Cook:
 "Lift gcc test into Kconfig. This is for better behavior when the
  kernel is built with Clang, reported by Stefan Agner"

* tag 'gcc-plugins-v4.19-rc1-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: Disable when building under Clang

Pull perf updates from Thomas Gleixner:
 "Kernel:
   - Improve kallsyms coverage
   - Add x86 entry trampolines to kcore
   - Fix ARM SPE handling
   - Correct PPC event post processing

  Tools:
   - Make the build system more robust
   - Small fixes and enhancements all over the place
   - Update kernel ABI header copies
   - Preparatory work for converting libtraceevnt to a shared library
   - License cleanups"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (100 commits)
  tools arch: Update arch/x86/lib/memcpy_64.S copy used in 'perf bench mem memcpy'
  tools arch x86: Update tools's copy of cpufeatures.h
  perf python: Fix pyrf_evlist__read_on_cpu() interface
  perf mmap: Store real cpu number in 'struct perf_mmap'
  perf tools: Remove ext from struct kmod_path
  perf tools: Add gzip_is_compressed function
  perf tools: Add lzma_is_compressed function
  perf tools: Add is_compressed callback to compressions array
  perf tools: Move the temp file processing into decompress_kmodule
  perf tools: Use compression id in decompress_kmodule()
  perf tools: Store compression id into struct dso
  perf tools: Add compression id into 'struct kmod_path'
  perf tools: Make is_supported_compression() static
  perf tools: Make decompress_to_file() function static
  perf tools: Get rid of dso__needs_decompress() call in __open_dso()
  perf tools: Get rid of dso__needs_decompress() call in symbol__disassemble()
  perf tools: Get rid of dso__needs_decompress() call in read_object_code()
  tools lib traceevent: Change to SPDX License format
  perf llvm: Allow passing options to llc in addition to clang
  perf parser: Improve error message for PMU address filters
  ...

Pull x86 fixes from Thomas Gleixner:

 - Correct the L1TF fallout on 32bit and the off by one in the 'too much
   RAM for protection' calculation.

 - Add a helpful kernel message for the 'too much RAM' case

 - Unbreak the VDSO in case that the compiler desides to use indirect
   jumps/calls and emits retpolines which cannot be resolved because the
   kernel uses its own thunks, which does not work for the VDSO. Make it
   use the builtin thunks.

 - Re-export start_thread() which was unexported when the 32/64bit
   implementation was unified. start_thread() is required by modular
   binfmt handlers.

 - Trivial cleanups

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/speculation/l1tf: Suggest what to do on systems with too much RAM
  x86/speculation/l1tf: Fix off-by-one error when warning that system has too much RAM
  x86/kvm/vmx: Remove duplicate l1d flush definitions
  x86/speculation/l1tf: Fix overflow in l1tf_pfn_limit() on 32bit
  x86/process: Re-export start_thread()
  x86/mce: Add notifier_block forward declaration
  x86/vdso: Fix vDSO build if a retpoline is emitted

Pull irq update from Thomas Gleixner:
 "A small set of updats/fixes for the irq subsystem:

   - Allow GICv3 interrupts to be configured as wake-up sources to
     enable wakeup from suspend

   - Make the error handling of the STM32 irqchip init function work

   - A set of small cleanups and improvements"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/gic-v3: Allow interrupt to be configured as wake-up sources
  irqchip/tango: Set irq handler and data in one go
  dt-bindings: irqchip: renesas-irqc: Document r8a774a1 support
  irqchip/s3c24xx: Remove unneeded comparison of unsigned long to 0
  irqchip/stm32: Fix init error handling
  irqchip/bcm7038-l1: Hide cpu offline callback when building for !SMP

Pull licking update from Thomas Gleixner:
 "Mark the switch cases which fall through to the next case with the
  proper comment so the fallthrough compiler checks can be enabled"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Mark expected switch fall-throughs

Merge tag 'libnvdimm-for-4.19_dax-memory-failure' of gitolite.kernel.org:pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull libnvdimm memory-failure update from Dave Jiang:
 "As it stands, memory_failure() gets thoroughly confused by dev_pagemap
  backed mappings. The recovery code has specific enabling for several
  possible page states and needs new enabling to handle poison in dax
  mappings.

  In order to support reliable reverse mapping of user space addresses:

   1/ Add new locking in the memory_failure() rmap path to prevent races
      that would typically be handled by the page lock.

   2/ Since dev_pagemap pages are hidden from the page allocator and the
      "compound page" accounting machinery, add a mechanism to determine
      the size of the mapping that encompasses a given poisoned pfn.

   3/ Given pmem errors can be repaired, change the speculatively
      accessed poison protection, mce_unmap_kpfn(), to be reversible and
      otherwise allow ongoing access from the kernel.

  A side effect of this enabling is that MADV_HWPOISON becomes usable
  for dax mappings, however the primary motivation is to allow the
  system to survive userspace consumption of hardware-poison via dax.
  Specifically the current behavior is:

     mce: Uncorrected hardware memory error in user-access at af34214200
     {1}[Hardware Error]: It has been corrected by h/w and requires no further action
     mce: [Hardware Error]: Machine check events logged
     {1}[Hardware Error]: event severity: corrected
     Memory failure: 0xaf34214: reserved kernel page still referenced by 1 users
     [..]
     Memory failure: 0xaf34214: recovery action for reserved kernel page: Failed
     mce: Memory error not recovered
     <reboot>

  ...and with these changes:

     Injecting memory failure for pfn 0x20cb00 at process virtual address 0x7f763dd00000
     Memory failure: 0x20cb00: Killing dax-pmd:5421 due to hardware memory corruption
     Memory failure: 0x20cb00: recovery action for dax page: Recovered

  Given all the cross dependencies I propose taking this through
  nvdimm.git with acks from Naoya, x86/core, x86/RAS, and of course dax
  folks"

* tag 'libnvdimm-for-4.19_dax-memory-failure' of gitolite.kernel.org:pub/scm/linux/kernel/git/nvdimm/nvdimm:
  libnvdimm, pmem: Restore page attributes when clearing errors
  x86/memory_failure: Introduce {set, clear}_mce_nospec()
  x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses
  mm, memory_failure: Teach memory_failure() about dev_pagemap pages
  filesystem-dax: Introduce dax_lock_mapping_entry()
  mm, memory_failure: Collect mapping size in collect_procs()
  mm, madvise_inject_error: Let memory_failure() optionally take a page reference
  mm, dev_pagemap: Do not clear ->mapping on final put
  mm, madvise_inject_error: Disable MADV_SOFT_OFFLINE for ZONE_DEVICE pages
  filesystem-dax: Set page->index
  device-dax: Set page->index
  device-dax: Enable page_mapping()
  device-dax: Convert to vmf_insert_mixed and vm_fault_t

Pull libnvdimm updates from Dave Jiang:
 "Collection of misc libnvdimm patches for 4.19 submission:

   - Adding support to read locked nvdimm capacity.

   - Change test code to make DSM failure code injection an override.

   - Add support for calculate maximum contiguous area for namespace.

   - Add support for queueing a short ARS when there is on going ARS for
     nvdimm.

   - Allow NULL to be passed in to ->direct_access() for kaddr and pfn
     params.

   - Improve smart injection support for nvdimm emulation testing.

   - Fix test code that supports for emulating controller temperature.

   - Fix hang on error before devm_memremap_pages()

   - Fix a bug that causes user memory corruption when data returned to
     user for ars_status.

   - Maintainer updates for Ross Zwisler emails and adding Jan Kara to
     fsdax"

* tag 'libnvdimm-for-4.19_misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/nvdimm/nvdimm:
  libnvdimm: fix ars_status output length calculation
  device-dax: avoid hang on error before devm_memremap_pages()
  tools/testing/nvdimm: improve emulation of smart injection
  filesystem-dax: Do not request kaddr and pfn when not required
  md/dm-writecache: Don't request pointer dummy_addr when not required
  dax/super: Do not request a pointer kaddr when not required
  tools/testing/nvdimm: kaddr and pfn can be NULL to ->direct_access()
  s390, dcssblk: kaddr and pfn can be NULL to ->direct_access()
  libnvdimm, pmem: kaddr and pfn can be NULL to ->direct_access()
  acpi/nfit: queue issuing of ars when an uc error notification comes in
  libnvdimm: Export max available extent
  libnvdimm: Use max contiguous area for namespace size
  MAINTAINERS: Add Jan Kara for filesystem DAX
  MAINTAINERS: update Ross Zwisler's email address
  tools/testing/nvdimm: Fix support for emulating controller temperature
  tools/testing/nvdimm: Make DSM failure code injection an override
  acpi, nfit: Prefer _DSM over _LSR for namespace label reads
  libnvdimm: Introduce locked DIMM capacity support

Pull ARM SoC late updates from Olof Johansson:
 "A couple of late-merged changes that would be useful to get in this
  merge window:

   - Driver support for reset of audio complex on Meson platforms. The
     audio driver went in this merge window, and these changes have been
     in -next for a while (just not in our tree).

   - Power management fixes for IOMMU on Rockchip platforms, getting
     closer to kexec working on them, including Chromebooks.

   - Another pass updating "arm,psci" -> "psci" for some properties that
     have snuck in since last time it was done"

* tag 'armsoc-late' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  iommu/rockchip: Move irq request past pm_runtime_enable
  iommu/rockchip: Handle errors returned from PM framework
  arm64: rockchip: Force CONFIG_PM on Rockchip systems
  ARM: rockchip: Force CONFIG_PM on Rockchip systems
  arm64: dts: Fix various entry-method properties to reflect documentation
  reset: imx7: Fix always writing bits as 0
  reset: meson: add meson audio arb driver
  reset: meson: add dt-bindings for meson-axg audio arb

Pull more Kbuild updates from Masahiro Yamada:

 - add build_{menu,n,g,x}config targets for compile-testing Kconfig

 - fix and improve recursive dependency detection in Kconfig

 - fix parallel building of menuconfig/nconfig

 - fix syntax error in clang-version.sh

 - suppress distracting log from syncconfig

 - remove obsolete "rpm" target

 - remove VMLINUX_SYMBOL(_STR) macro entirely

 - fix microblaze build with CONFIG_DYNAMIC_FTRACE

 - move compiler test for dead code/data elimination to Kconfig

 - rename well-known LDFLAGS variable to KBUILD_LDFLAGS

 - misc fixes and cleanups

* tag 'kbuild-v4.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: rename LDFLAGS to KBUILD_LDFLAGS
  kbuild: pass LDFLAGS to recordmcount.pl
  kbuild: test dead code/data elimination support in Kconfig
  initramfs: move gen_initramfs_list.sh from scripts/ to usr/
  vmlinux.lds.h: remove stale <linux/export.h> include
  export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR()
  Coccinelle: remove pci_alloc_consistent semantic to detect in zalloc-simple.cocci
  kbuild: make sorting initramfs contents independent of locale
  kbuild: remove "rpm" target, which is alias of "rpm-pkg"
  kbuild: Fix LOADLIBES rename in Documentation/kbuild/makefiles.txt
  kconfig: suppress "configuration written to .config" for syncconfig
  kconfig: fix "Can't open ..." in parallel build
  kbuild: Add a space after `!` to prevent parsing as file pattern
  scripts: modpost: check memory allocation results
  kconfig: improve the recursive dependency report
  kconfig: report recursive dependency involving 'imply'
  kconfig: error out when seeing recursive dependency
  kconfig: add build-only configurator targets
  scripts/dtc: consolidate include path options in Makefile

Pull block fixes from Jens Axboe:
 "A few small fixes for this merge window:

   - Locking imbalance fix for bcache (Shan Hai)

   - A few small fixes for wbt. One is a cleanup/prep, one is a fix for
     an existing issue, and the last two are fixes for changes that went
     into this merge window (me)"

* tag 'for-linus-20180825' of git://git.kernel.dk/linux-block:
  blk-wbt: don't maintain inflight counts if disabled
  blk-wbt: fix has-sleeper queueing check
  blk-wbt: use wq_has_sleeper() for wq active check
  blk-wbt: move disable check into get_limit()
  bcache: release dc->writeback_lock properly in bch_writeback_thread()

Pull UBIFS fix from Richard Weinberger:
 "Remove an empty file from UBIFS source"

* tag 'upstream-4.19-rc1-fix' of git://git.infradead.org/linux-ubifs:
  ubifs: Remove empty file.h

Pull cifs fixes from Steve French:
 "Three small SMB3 fixes, one for stable"

* tag '4.19-rc-smb3' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: update internal module version number for cifs.ko to 2.12
  cifs: check kmalloc before use
  cifs: check if SMB2 PDU size has been padded and suppress the warning
  cifs: create a define for how many iovs we need for an SMB2_open()

This is not normally noticeable, but repeated forks are unnecessarily
expensive because they repeatedly dirty the parent page tables during
the page table copy operation.

It's trivial to just avoid write protecting the page table entry if it
was already not writable.

This patch was inspired by

    https://bugzilla.kernel.org/show_bug.cgi?id=200447

which points to an ancient "waste time re-doing fork" issue in the
presence of lots of signals.

That bug was fixed by Eric Biederman's signal handling series
culminating in commit c3ad2c3b ("signal: Don't restart fork when
signals come in"), but the unnecessary work for repeated forks is still
work just fixing, particularly since the fix is trivial.

Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

At the point where r is being checked for different values, r is always
going to be equal to 2 as the previous if statements jump to end or end1
if r is not 2.  Hence the assignment to err can be simplified to just
err an assignment without any checks on the value or r.

Detected by CoverityScan, CID#1226737 ("Logically dead code")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NMikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>