At Linux Plumbers, Andy Lutomirski approached me and pointed out that the
function call syscall_get_arguments() implemented in x86 was horribly
written and not optimized for the standard case of passing in 0 and 6 for
the starting index and the number of system calls to get. When looking at
all the users of this function, I discovered that all instances pass in only
0 and 6 for these arguments. Instead of having this function handle
different cases that are never used, simply rewrite it to return the first 6
arguments of a system call.

This should help out the performance of tracing system calls by ptrace,
ftrace and perf.

Link: http://lkml.kernel.org/r/20161107213233.754809394@goodmis.org

Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Dave Martin <dave.martin@arm.com>
Cc: "Dmitry V. Levin" <ldv@altlinux.org>
Cc: x86@kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-hexagon@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: nios2-dev@lists.rocketboards.org
Cc: openrisc@lists.librecores.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-um@lists.infradead.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-arch@vger.kernel.org
Acked-by: Paul Burton <paul.burton@mips.com> # MIPS parts
Acked-by: Max Filippov <jcmvbkbc@gmail.com> # For xtensa changes
Acked-by: Will Deacon <will.deacon@arm.com> # For the arm64 bits
Reviewed-by: Thomas Gleixner <tglx@linutronix.de> # for x86
Reviewed-by: Dmitry V. Levin <ldv@altlinux.org>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Pull MIPS fixes from Paul Burton:
 "A small batch of MIPS fixes for 5.1:

   - An interrupt masking fix for Loongson-based Lemote 2F systems
     (fixing a regression from v3.19)

   - A relocation fix for configurations in which the devicetree is
     stored in an ELF section (fixing a regression from v4.7)

   - Fix jump labels for MIPSr6 kernels where they previously could
     inadvertently place a control transfer instruction in a forbidden
     slot & take unexpected exceptions (fixing MIPSr6 support added in
     v4.0)

   - Extend an existing USB power workaround for the Netgear WNDR3400 to
     v2 boards in addition to the v3 ones that already used it

   - Remove the custom MIPS32 definition of __kernel_fsid_t to make it
     consistent with MIPS64 & every other architecture, in particular
     resolving issues for code which tries to print the val field whose
     type previously differed (though had identical memory layout)"

* tag 'mips_fixes_5.1_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  MIPS: Remove custom MIPS32 __kernel_fsid_t type
  mips: bcm47xx: Enable USB power on Netgear WNDR3400v2
  MIPS: Fix kernel crash for R6 in jump label branch function
  MIPS: Ensure ELF appended dtb is relocated
  mips: loongson64: lemote-2f: Add IRQF_NO_SUSPEND to "cascade" irqaction.

Pull KVM updates from Paolo Bonzini:
 "ARM:
   - some cleanups
   - direct physical timer assignment
   - cache sanitization for 32-bit guests

  s390:
   - interrupt cleanup
   - introduction of the Guest Information Block
   - preparation for processor subfunctions in cpu models

  PPC:
   - bug fixes and improvements, especially related to machine checks
     and protection keys

  x86:
   - many, many cleanups, including removing a bunch of MMU code for
     unnecessary optimizations
   - AVIC fixes

  Generic:
   - memcg accounting"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (147 commits)
  kvm: vmx: fix formatting of a comment
  KVM: doc: Document the life cycle of a VM and its resources
  MAINTAINERS: Add KVM selftests to existing KVM entry
  Revert "KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()"
  KVM: PPC: Book3S: Add count cache flush parameters to kvmppc_get_cpu_char()
  KVM: PPC: Fix compilation when KVM is not enabled
  KVM: Minor cleanups for kvm_main.c
  KVM: s390: add debug logging for cpu model subfunctions
  KVM: s390: implement subfunction processor calls
  arm64: KVM: Fix architecturally invalid reset value for FPEXC32_EL2
  KVM: arm/arm64: Remove unused timer variable
  KVM: PPC: Book3S: Improve KVM reference counting
  KVM: PPC: Book3S HV: Fix build failure without IOMMU support
  Revert "KVM: Eliminate extra function calls in kvm_get_dirty_log_protect()"
  x86: kvmguest: use TSC clocksource if invariant TSC is exposed
  KVM: Never start grow vCPU halt_poll_ns from value below halt_poll_ns_grow_start
  KVM: Expose the initial start value in grow_halt_poll_ns() as a module parameter
  KVM: grow_halt_poll_ns() should never shrink vCPU halt_poll_ns
  KVM: x86/mmu: Consolidate kvm_mmu_zap_all() and kvm_mmu_zap_mmio_sptes()
  KVM: x86/mmu: WARN if zapping a MMIO spte results in zapping children
  ...

Insert Branch instruction instead of NOP to make sure assembler don't
patch code in forbidden slot. In jump label function, it might
be possible to patch Control Transfer Instructions(CTIs) into
forbidden slot, which will generate Reserved Instruction exception
in MIPS release 6.

Signed-off-by: Archer Yan <ayan@wavecomp.com>
Reviewed-by: Paul Burton <paul.burton@mips.com>
[paul.burton@mips.com:
  - Add MIPS prefix to subject.
  - Mark for stable from v4.0, which introduced r6 support, onwards.]
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: stable@vger.kernel.org # v4.0+

Pull DMA mapping updates from Christoph Hellwig:

 - add debugfs support for dumping dma-debug information (Corentin
   Labbe)

 - Kconfig cleanups (Andy Shevchenko and me)

 - debugfs cleanups (Greg Kroah-Hartman)

 - improve dma_map_resource and use it in the media code

 - arch_setup_dma_ops / arch_teardown_dma_ops cleanups

 - various small cleanups and improvements for the per-device coherent
   allocator

 - make the DMA mask an upper bound and don't fail "too large" dma mask
   in the remaning two architectures - this will allow big driver
   cleanups in the following merge windows

* tag 'dma-mapping-5.1' of git://git.infradead.org/users/hch/dma-mapping: (21 commits)
  Documentation/DMA-API-HOWTO: update dma_mask sections
  sparc64/pci_sun4v: allow large DMA masks
  sparc64/iommu: allow large DMA masks
  sparc64: refactor the ali DMA quirk
  ccio: allow large DMA masks
  dma-mapping: remove the DMA_MEMORY_EXCLUSIVE flag
  dma-mapping: remove dma_mark_declared_memory_occupied
  dma-mapping: move CONFIG_DMA_CMA to kernel/dma/Kconfig
  dma-mapping: improve selection of dma_declare_coherent availability
  dma-mapping: remove an incorrect __iommem annotation
  of: select OF_RESERVED_MEM automatically
  device.h: dma_mem is only needed for HAVE_GENERIC_DMA_COHERENT
  mfd/sm501: depend on HAS_DMA
  dma-mapping: add a kconfig symbol for arch_teardown_dma_ops availability
  dma-mapping: add a kconfig symbol for arch_setup_dma_ops availability
  dma-mapping: move debug configuration options to kernel/dma
  dma-debug: add dumping facility via debugfs
  dma: debug: no need to check return value of debugfs_create functions
  videobuf2: replace a layering violation with dma_map_resource
  dma-mapping: don't BUG when calling dma_map_resource on RAM
  ...

Pull year 2038 updates from Thomas Gleixner:
 "Another round of changes to make the kernel ready for 2038. After lots
  of preparatory work this is the first set of syscalls which are 2038
  safe:

    403 clock_gettime64
    404 clock_settime64
    405 clock_adjtime64
    406 clock_getres_time64
    407 clock_nanosleep_time64
    408 timer_gettime64
    409 timer_settime64
    410 timerfd_gettime64
    411 timerfd_settime64
    412 utimensat_time64
    413 pselect6_time64
    414 ppoll_time64
    416 io_pgetevents_time64
    417 recvmmsg_time64
    418 mq_timedsend_time64
    419 mq_timedreceiv_time64
    420 semtimedop_time64
    421 rt_sigtimedwait_time64
    422 futex_time64
    423 sched_rr_get_interval_time64

  The syscall numbers are identical all over the architectures"

* 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
  riscv: Use latest system call ABI
  checksyscalls: fix up mq_timedreceive and stat exceptions
  unicore32: Fix __ARCH_WANT_STAT64 definition
  asm-generic: Make time32 syscall numbers optional
  asm-generic: Drop getrlimit and setrlimit syscalls from default list
  32-bit userspace ABI: introduce ARCH_32BIT_OFF_T config option
  compat ABI: use non-compat openat and open_by_handle_at variants
  y2038: add 64-bit time_t syscalls to all 32-bit architectures
  y2038: rename old time and utime syscalls
  y2038: remove struct definition redirects
  y2038: use time32 syscall names on 32-bit
  syscalls: remove obsolete __IGNORE_ macros
  y2038: syscalls: rename y2038 compat syscalls
  x86/x32: use time64 versions of sigtimedwait and recvmmsg
  timex: change syscalls to use struct __kernel_timex
  timex: use __kernel_timex internally
  sparc64: add custom adjtimex/clock_adjtime functions
  time: fix sys_timer_settime prototype
  time: Add struct __kernel_timex
  time: make adjtime compat handling available for 32 bit
  ...

Pull MIPS updates from Paul Burton:

 - Support for the MIPSr6 MemoryMapID register & Global INValidate TLB
   (GINVT) instructions, allowing for more efficient TLB maintenance
   when running on a CPU such as the I6500 that supports these.

 - Enable huge page support for MIPS64r6.

 - Optimize post-DMA cache sync by removing that code entirely for
   kernel configurations in which we know it won't be needed.

 - The number of pages allocated for interrupt stacks is now calculated
   correctly, where before we would wastefully allocate too much memory
   in some configurations.

 - The ath79 platform migrates to devicetree.

 - The bcm47xx platform sees fixes for the Buffalo WHR-G54S board.

 - The ingenic/jz4740 platform gains support for appended devicetrees.

 - The cavium_octeon, lantiq, loongson32 & sgi-ip27 platforms all see
   cleanups as do various pieces of core architecture code.

* tag 'mips_5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: (66 commits)
  MIPS: lantiq: Remove separate GPHY Firmware loader
  MIPS: ingenic: Add support for appended devicetree
  MIPS: SGI-IP27: rework HUB interrupts
  MIPS: SGI-IP27: do boot CPU init later
  MIPS: SGI-IP27: do xtalk scanning later
  MIPS: SGI-IP27: use pr_info/pr_emerg and pr_cont to fix output
  MIPS: SGI-IP27: clean up bridge access and header files
  MIPS: SGI-IP27: get rid of volatile and hubreg_t
  MIPS: irq: Allocate accurate order pages for irq stack
  MIPS: dma-noncoherent: Remove bogus condition in dma_sync_phys()
  MIPS: eBPF: Remove REG_32BIT_ZERO_EX
  MIPS: eBPF: Always return sign extended 32b values
  MIPS: CM: Fix indentation
  MIPS: BCM47XX: Fix/improve Buffalo WHR-G54S support
  MIPS: OCTEON: program rx/tx-delay always from DT
  MIPS: OCTEON: delete board-specific link status
  MIPS: OCTEON: don't lie about interface type of CN3005 board
  MIPS: OCTEON: warn if deprecated link status is being used
  MIPS: OCTEON: add fixed-link nodes to in-kernel device tree
  MIPS: Delete unused flush_cache_sigtramp()
  ...

Pull spi updates from Mark Brown:
 "A fairly quiet release for SPI, the biggest thing is the conversion to
  use GPIO descriptors which is now 90% done but still needs some
  stragglers converting.

  Summary:

   - Support for inter-word delays

   - Conversion of the core and most drivers to use GPIO descriptors for
     GPIO controlled chip selects

   - New drivers for NXP FlexSPI and QuadSPI, SiFive and Spreadtrum"

* tag 'spi-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi: (104 commits)
  spi: sh-msiof: Restrict bits per word to 8/16/24/32 on R-Car Gen2/3
  spi: sifive: Remove redundant dev_err call in sifive_spi_probe()
  spi: sifive: Remove spi_master_put in sifive_spi_remove()
  spi: spi-gpio: fix SPI_CS_HIGH capability
  spi: pxa2xx: Setup maximum supported DMA transfer length
  spi: sifive: Add driver for the SiFive SPI controller
  spi: sifive: Add DT documentation for SiFive SPI controller
  spi: sprd: Add a prefix for SPI DMA channel macros
  spi: sprd: spi: sprd: Add DMA mode support
  dt-bindings: spi: Add the DMA properties for the SPI dma mode
  spi: sprd: Add the SPI irq function for the SPI DMA mode
  dt-bindings: spi: imx: Add an entry for the i.MX8QM compatible
  spi: use gpio[d]_set_value_cansleep for setting chipselect GPIO
  spi: gpio: Advertise support for SPI_CS_HIGH
  spi: sh-msiof: Replace spi_master by spi_controller
  spi: sh-hspi: Replace spi_master by spi_controller
  spi: rspi: Replace spi_master by spi_controller
  spi: atmel-quadspi: add support for sam9x60 qspi controller
  dt-bindings: spi: atmel-quadspi: QuadSPI driver for Microchip SAM9X60
  spi: atmel-quadspi: add support for named peripheral clock
  ...

Every in-kernel use of this function defined it to KERNEL_DS (either as
an actual define, or as an inline function).  It's an entirely
historical artifact, and long long long ago used to actually read the
segment selector valueof '%ds' on x86.

Which in the kernel is always KERNEL_DS.

Inspired by a patch from Jann Horn that just did this for a very small
subset of users (the ones in fs/), along with Al who suggested a script.
I then just took it to the logical extreme and removed all the remaining
gunk.

Roughly scripted with

   git grep -l '(get_ds())' -- :^tools/ | xargs sed -i 's/(get_ds())/(KERNEL_DS)/'
   git grep -lw 'get_ds' -- :^tools/ | xargs sed -i '/^#define get_ds()/d'

plus manual fixups to remove a few unusual usage patterns, the couple of
inline function cases and to fix up a comment that had become stale.

The 'get_ds()' function remains in an x86 kvm selftest, since in user
space it actually does something relevant.

Inspired-by: Jann Horn <jannh@google.com>
Inspired-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>