linux.git/arch/mips/include/asm, branch v4.8-rc2

Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus

2016-08-06T13:13:11+00:00

Pull MIPS updates from Ralf Baechle:
 "This is the main pull request for MIPS for 4.8.  Also includes is a
  minor SSB cleanup as SSB code traditionally is merged through the MIPS
  tree:

  ATH25:
    - MIPS: Add default configuration for ath25

  Boot:
    - For zboot, copy appended dtb to the end of the kernel
    - store the appended dtb address in a variable

  BPF:
    - Fix off by one error in offset allocation

  Cobalt code:
    - Fix typos

  Core code:
    - debugfs_create_file returns NULL on error, so don't use IS_ERR for
      testing for errors.
    - Fix double locking issue in RM7000 S-cache code.  This would only
      affect RM7000 ARC systems on reboot.
    - Fix page table corruption on THP permission changes.
    - Use compat_sys_keyctl for 32 bit userspace on 64 bit kernels.
      David says, there are no compatibility issues raised by this fix.
    - Move some signal code around.
    - Rewrite r4k count/compare clockevent device registration such that
      min_delta_ticks/max_delta_ticks files are guaranteed to be
      initialized.
    - Only register r4k count/compare as clockevent device if we can
      assume the clock to be constant.
    - Fix MSA asm warnings in control reg accessors
    - uasm and tlbex fixes and tweaking.
    - Print segment physical address when EU=1.
    - Define AT_VECTOR_SIZE_ARCH for ARCH_DLINFO.
    - CP: Allow booting by VP other than VP 0
    - Cache handling fixes and optimizations for r4k class caches
    - Add hotplug support for R6 processors
    - Cleanup hotplug bits in kconfig
    - traps: return correct si code for accessing nonmapped addresses
    - Remove cpu_has_safe_index_cacheops

  Lantiq:
    - Register IRQ handler for virtual IRQ number
    - Fix EIU interrupt loading code
    - Use the real EXIN count
    - Fix build error.

  Loongson 3:
    - Increase HPET_MIN_PROG_DELTA and decrease HPET_MIN_CYCLES

  Octeon:
    - Delete built-in DTB pruning code for D-Link DSR-1000N.
    - Clean up GPIO definitions in dlink_dsr-1000n.dts.
    - Add more LEDs to the DSR-100n DTS
    - Fix off by one in octeon_irq_gpio_map()
    - Typo fixes
    - Enable SATA by default in cavium_octeon_defconfig
    - Support readq/writeq()
    - Remove forced mappings of USB interrupts.
    - Ensure DMA descriptors are always in the low 4GB
    - Improve USB reset code for OCTEON II.

  Pistachio:
    - Add maintainers entry for pistachio SoC Support
    - Remove plat_setup_iocoherency

  Ralink:
    - Fix pwm UART in spis group pinmux.

  SSB:
    - Change bare unsigned to unsigned int to suit coding style

  Tools:
    - Fix reloc tool compiler warnings.

  Other:
    - Delete use of ARCH_WANT_OPTIONAL_GPIOLIB"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (61 commits)
  MIPS: mm: Fix definition of R6 cache instruction
  MIPS: tools: Fix relocs tool compiler warnings
  MIPS: Cobalt: Fix typo
  MIPS: Octeon: Fix typo
  MIPS: Lantiq: Fix build failure
  MIPS: Use CPHYSADDR to implement mips32 __pa
  MIPS: Octeon: Dlink_dsr-1000n.dts: add more leds.
  MIPS: Octeon: Clean up GPIO definitions in dlink_dsr-1000n.dts.
  MIPS: Octeon: Delete built-in DTB pruning code for D-Link DSR-1000N.
  MIPS: store the appended dtb address in a variable
  MIPS: ZBOOT: copy appended dtb to the end of the kernel
  MIPS: ralink: fix spis group pinmux
  MIPS: Factor o32 specific code into signal_o32.c
  MIPS: non-exec stack & heap when non-exec PT_GNU_STACK is present
  MIPS: Use per-mm page to execute branch delay slot instructions
  MIPS: Modify error handling
  MIPS: c-r4k: Use SMP calls for CM indexed cache ops
  MIPS: c-r4k: Avoid small flush_icache_range SMP calls
  MIPS: c-r4k: Local flush_icache_range cache op override
  MIPS: c-r4k: Split r4k_flush_kernel_vmap_range()
  ...

tree-wide: replace config_enabled() with IS_ENABLED()

2016-08-04T12:50:07+00:00

The use of config_enabled() against config options is ambiguous.  In
practical terms, config_enabled() is equivalent to IS_BUILTIN(), but the
author might have used it for the meaning of IS_ENABLED().  Using
IS_ENABLED(), IS_BUILTIN(), IS_MODULE() etc.  makes the intention
clearer.

This commit replaces config_enabled() with IS_ENABLED() where possible.
This commit is only touching bool config options.

I noticed two cases where config_enabled() is used against a tristate
option:

 - config_enabled(CONFIG_HWMON)
  [ drivers/net/wireless/ath/ath10k/thermal.c ]

 - config_enabled(CONFIG_BACKLIGHT_CLASS_DEVICE)
  [ drivers/gpu/drm/gma500/opregion.c ]

I did not touch them because they should be converted to IS_BUILTIN()
in order to keep the logic, but I was not sure it was the authors'
intention.

Link: http://lkml.kernel.org/r/1465215656-20569-1-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada 
Acked-by: Kees Cook 
Cc: Stas Sergeev 
Cc: Matt Redfearn 
Cc: Joshua Kinard 
Cc: Jiri Slaby 
Cc: Bjorn Helgaas 
Cc: Borislav Petkov 
Cc: Markos Chandras 
Cc: "Dmitry V. Levin" 
Cc: yu-cheng yu 
Cc: James Hogan 
Cc: Brian Gerst 
Cc: Johannes Berg 
Cc: Peter Zijlstra 
Cc: Al Viro 
Cc: Will Drewry 
Cc: Nikolay Martynov 
Cc: Huacai Chen 
Cc: "H. Peter Anvin" 
Cc: Thomas Gleixner 
Cc: Daniel Borkmann 
Cc: Leonid Yegoshin 
Cc: Rafal Milecki 
Cc: James Cowgill 
Cc: Greg Kroah-Hartman 
Cc: Ralf Baechle 
Cc: Alex Smith 
Cc: Adam Buchbinder 
Cc: Qais Yousef 
Cc: Jiang Liu 
Cc: Mikko Rapeli 
Cc: Paul Gortmaker 
Cc: Denys Vlasenko 
Cc: Brian Norris 
Cc: Hidehiro Kawai 
Cc: "Luis R. Rodriguez" 
Cc: Andy Lutomirski 
Cc: Ingo Molnar 
Cc: Dave Hansen 
Cc: "Kirill A. Shutemov" 
Cc: Roland McGrath 
Cc: Paul Burton 
Cc: Kalle Valo 
Cc: Viresh Kumar 
Cc: Tony Wu 
Cc: Huaitong Han 
Cc: Sumit Semwal 
Cc: Alexei Starovoitov 
Cc: Juergen Gross 
Cc: Jason Cooper 
Cc: "David S. Miller" 
Cc: Oleg Nesterov 
Cc: Andrea Gelmini 
Cc: David Woodhouse 
Cc: Marc Zyngier 
Cc: Rabin Vincent 
Cc: "Maciej W. Rozycki" 
Cc: David Daney 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch '4.7-fixes' into mips-for-linux-next

2016-08-03T10:55:49+00:00

Merge tag 'pci-v4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci

2016-08-02T21:12:29+00:00

Pull PCI updates from Bjorn Helgaas:
 "Highlights:

   - ARM64 support for ACPI host bridges

   - new drivers for Axis ARTPEC-6 and Marvell Aardvark

   - new pci_alloc_irq_vectors() interface for MSI-X, MSI, legacy INTx

   - pci_resource_to_user() cleanup (more to come)

  Detailed summary:

  Enumeration:
   - Move ecam.h to linux/include/pci-ecam.h (Jayachandran C)
   - Add parent device field to ECAM struct pci_config_window (Jayachandran C)
   - Add generic MCFG table handling (Tomasz Nowicki)
   - Refactor pci_bus_assign_domain_nr() for CONFIG_PCI_DOMAINS_GENERIC (Tomasz Nowicki)
   - Factor DT-specific pci_bus_find_domain_nr() code out (Tomasz Nowicki)

  Resource management:
   - Add devm_request_pci_bus_resources() (Bjorn Helgaas)
   - Unify pci_resource_to_user() declarations (Bjorn Helgaas)
   - Implement pci_resource_to_user() with pcibios_resource_to_bus() (microblaze, powerpc, sparc) (Bjorn Helgaas)
   - Request host bridge window resources (designware, iproc, rcar, xgene, xilinx, xilinx-nwl) (Bjorn Helgaas)
   - Make PCI I/O space optional on ARM32 (Bjorn Helgaas)
   - Ignore write combining when mapping I/O port space (Bjorn Helgaas)
   - Claim bus resources on MIPS PCI_PROBE_ONLY set-ups (Bjorn Helgaas)
   - Remove unicore32 pci=firmware command line parameter handling (Bjorn Helgaas)
   - Support I/O resources when parsing host bridge resources (Jayachandran C)
   - Add helpers to request/release memory and I/O regions (Johannes Thumshirn)
   - Use pci_(request|release)_mem_regions (NVMe, lpfc, GenWQE, ethernet/intel, alx) (Johannes Thumshirn)
   - Extend pci=resource_alignment to specify device/vendor IDs (Koehrer Mathias (ETAS/ESW5))
   - Add generic pci_bus_claim_resources() (Lorenzo Pieralisi)
   - Claim bus resources on ARM32 PCI_PROBE_ONLY set-ups (Lorenzo Pieralisi)
   - Remove ARM32 and ARM64 arch-specific pcibios_enable_device() (Lorenzo Pieralisi)
   - Add pci_unmap_iospace() to unmap I/O resources (Sinan Kaya)
   - Remove powerpc __pci_mmap_set_pgprot() (Yinghai Lu)

  PCI device hotplug:
   - Allow additional bus numbers for hotplug bridges (Keith Busch)
   - Ignore interrupts during D3cold (Lukas Wunner)

  Power management:
   - Enforce type casting for pci_power_t (Andy Shevchenko)
   - Don't clear d3cold_allowed for PCIe ports (Mika Westerberg)
   - Put PCIe ports into D3 during suspend (Mika Westerberg)
   - Power on bridges before scanning new devices (Mika Westerberg)
   - Runtime resume bridge before rescan (Mika Westerberg)
   - Add runtime PM support for PCIe ports (Mika Westerberg)
   - Remove redundant check of pcie_set_clkpm (Shawn Lin)

  Virtualization:
   - Add function 1 DMA alias quirk for Marvell 88SE9182 (Aaron Sierra)
   - Add DMA alias quirk for Adaptec 3805 (Alex Williamson)
   - Mark Atheros AR9485 and QCA9882 to avoid bus reset (Chris Blake)
   - Add ACS quirk for Solarflare SFC9220 (Edward Cree)

  MSI:
   - Fix PCI_MSI dependencies (Arnd Bergmann)
   - Add pci_msix_desc_addr() helper (Christoph Hellwig)
   - Switch msix_program_entries() to use pci_msix_desc_addr() (Christoph Hellwig)
   - Make the "entries" argument to pci_enable_msix() optional (Christoph Hellwig)
   - Provide sensible IRQ vector alloc/free routines (Christoph Hellwig)
   - Spread interrupt vectors in pci_alloc_irq_vectors() (Christoph Hellwig)

  Error Handling:
   - Bind DPC to Root Ports as well as Downstream Ports (Keith Busch)
   - Remove DPC tristate module option (Keith Busch)
   - Convert Downstream Port Containment driver to use devm_* functions (Mika Westerberg)

  Generic host bridge driver:
   - Select IRQ_DOMAIN (Arnd Bergmann)
   - Claim bus resources on PCI_PROBE_ONLY set-ups (Lorenzo Pieralisi)

  ACPI host bridge driver:
   - Add ARM64 acpi_pci_bus_find_domain_nr() (Tomasz Nowicki)
   - Add ARM64 ACPI support for legacy IRQs parsing and consolidation with DT code (Tomasz Nowicki)
   - Implement ARM64 AML accessors for PCI_Config region (Tomasz Nowicki)
   - Support ARM64 ACPI-based PCI host controller (Tomasz Nowicki)

  Altera host bridge driver:
   - Check link status before retrain link (Ley Foon Tan)
   - Poll for link up status after retraining the link (Ley Foon Tan)

  Axis ARTPEC-6 host bridge driver:
   - Add PCI_MSI_IRQ_DOMAIN dependency (Arnd Bergmann)
   - Add DT binding for Axis ARTPEC-6 PCIe controller (Niklas Cassel)
   - Add Axis ARTPEC-6 PCIe controller driver (Niklas Cassel)

  Intel VMD host bridge driver:
   - Use lock save/restore in interrupt enable path (Jon Derrick)
   - Select device dma ops to override (Keith Busch)
   - Initialize list item in IRQ disable (Keith Busch)
   - Use x86_vector_domain as parent domain (Keith Busch)
   - Separate MSI and MSI-X vector sharing (Keith Busch)

  Marvell Aardvark host bridge driver:
   - Add DT binding for the Aardvark PCIe controller (Thomas Petazzoni)
   - Add Aardvark PCI host controller driver (Thomas Petazzoni)
   - Add Aardvark PCIe support for Armada 3700 (Thomas Petazzoni)

  Microsoft Hyper-V host bridge driver:
   - Fix interrupt cleanup path (Cathy Avery)
   - Don't leak buffer in hv_pci_onchannelcallback() (Vitaly Kuznetsov)
   - Handle all pending messages in hv_pci_onchannelcallback() (Vitaly Kuznetsov)

  NVIDIA Tegra host bridge driver:
   - Program PADS_REFCLK_CFG* always, not just on legacy SoCs (Stephen Warren)
   - Program PADS_REFCLK_CFG* registers with per-SoC values (Stephen Warren)
   - Use lower-case hex consistently for register definitions (Thierry Reding)
   - Use generic pci_remap_iospace() rather than ARM32-specific one (Thierry Reding)
   - Stop setting pcibios_min_mem (Thierry Reding)

  Renesas R-Car host bridge driver:
   - Drop gen2 dummy I/O port region (Bjorn Helgaas)

  TI DRA7xx host bridge driver:
   - Fix return value in case of error (Christophe JAILLET)

  Xilinx AXI host bridge driver:
   - Fix return value in case of error (Christophe JAILLET)

  Miscellaneous:
   - Make bus_attr_resource_alignment static (Ben Dooks)
   - Include  for isa_dma_bridge_buggy (Ben Dooks)
   - MAINTAINERS: Add file patterns for PCI device tree bindings (Geert Uytterhoeven)
   - Make host bridge drivers explicitly non-modular (Paul Gortmaker)"

* tag 'pci-v4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci: (125 commits)
  PCI: xgene: Make explicitly non-modular
  PCI: thunder-pem: Make explicitly non-modular
  PCI: thunder-ecam: Make explicitly non-modular
  PCI: tegra: Make explicitly non-modular
  PCI: rcar-gen2: Make explicitly non-modular
  PCI: rcar: Make explicitly non-modular
  PCI: mvebu: Make explicitly non-modular
  PCI: layerscape: Make explicitly non-modular
  PCI: keystone: Make explicitly non-modular
  PCI: hisi: Make explicitly non-modular
  PCI: generic: Make explicitly non-modular
  PCI: designware-plat: Make it explicitly non-modular
  PCI: artpec6: Make explicitly non-modular
  PCI: armada8k: Make explicitly non-modular
  PCI: artpec: Add PCI_MSI_IRQ_DOMAIN dependency
  PCI: Add ACS quirk for Solarflare SFC9220
  arm64: dts: marvell: Add Aardvark PCIe support for Armada 3700
  PCI: aardvark: Add Aardvark PCI host controller driver
  dt-bindings: add DT binding for the Aardvark PCIe controller
  PCI: tegra: Program PADS_REFCLK_CFG* registers with per-SoC values
  ...

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2016-08-02T20:11:27+00:00

Pull KVM updates from Paolo Bonzini:

 - ARM: GICv3 ITS emulation and various fixes.  Removal of the
   old VGIC implementation.

 - s390: support for trapping software breakpoints, nested
   virtualization (vSIE), the STHYI opcode, initial extensions
   for CPU model support.

 - MIPS: support for MIPS64 hosts (32-bit guests only) and lots
   of cleanups, preliminary to this and the upcoming support for
   hardware virtualization extensions.

 - x86: support for execute-only mappings in nested EPT; reduced
   vmexit latency for TSC deadline timer (by about 30%) on Intel
   hosts; support for more than 255 vCPUs.

 - PPC: bugfixes.

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (302 commits)
  KVM: PPC: Introduce KVM_CAP_PPC_HTM
  MIPS: Select HAVE_KVM for MIPS64_R{2,6}
  MIPS: KVM: Reset CP0_PageMask during host TLB flush
  MIPS: KVM: Fix ptr->int cast via KVM_GUEST_KSEGX()
  MIPS: KVM: Sign extend MFC0/RDHWR results
  MIPS: KVM: Fix 64-bit big endian dynamic translation
  MIPS: KVM: Fail if ebase doesn't fit in CP0_EBase
  MIPS: KVM: Use 64-bit CP0_EBase when appropriate
  MIPS: KVM: Set CP0_Status.KX on MIPS64
  MIPS: KVM: Make entry code MIPS64 friendly
  MIPS: KVM: Use kmap instead of CKSEG0ADDR()
  MIPS: KVM: Use virt_to_phys() to get commpage PFN
  MIPS: Fix definition of KSEGX() for 64-bit
  KVM: VMX: Add VMCS to CPU's loaded VMCSs before VMPTRLD
  kvm: x86: nVMX: maintain internal copy of current VMCS
  KVM: PPC: Book3S HV: Save/restore TM state in H_CEDE
  KVM: PPC: Book3S HV: Pull out TM state save/restore into separate procedures
  KVM: arm64: vgic-its: Simplify MAPI error handling
  KVM: arm64: vgic-its: Make vgic_its_cmd_handle_mapi similar to other handlers
  KVM: arm64: vgic-its: Turn device_id validation into generic ID validation
  ...

MIPS: Use CPHYSADDR to implement mips32 __pa

2016-08-02T12:01:02+00:00

Use CPHYSADDR to implement the __pa macro converting from a virtual to a
physical address for MIPS32, much as is already done for MIPS64 (though
without the complication of having both compatibility & XKPHYS
segments).

This allows for __pa to work regardless of whether the address being
translated is in kseg0 or kseg1, unlike the previous subtraction based
approach which only worked for addresses in kseg0. Working for kseg1
addresses is important if __pa is used on addresses allocated by
dma_alloc_coherent, where on systems with non-coherent I/O we provide
addresses in kseg1. If this address is then used with
dma_map_single_attrs then it is provided to virt_to_page, which in turn
calls virt_to_phys which is a wrapper around __pa. The result is that we
end up with a physical address 0x20000000 bytes (ie. the size of kseg0)
too high.

In addition to providing consistency with MIPS64 & fixing the kseg1 case
above this has the added bonus of generating smaller code for systems
implementing MIPS32r2 & beyond, where a single ext instruction can
extract the physical address rather than needing to load an immediate
into a temp register & subtract it. This results in ~1.3KB savings for a
boston_defconfig kernel adjusted to set CONFIG_32BIT=y.

This patch does not change the EVA case, which may or may not have
similar issues around handling both cached & uncached addresses but is
beyond the scope of this patch.

Signed-off-by: Paul Burton 
Cc: Dan Williams 
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13836/
Signed-off-by: Ralf Baechle

MIPS: store the appended dtb address in a variable

2016-08-02T12:00:16+00:00

Instead of rewriting the arguments to match the UHI spec, store the
address of a appended or UHI supplied dtb in fw_supplied_dtb.

That way the original bootloader arugments are kept intact while still
making the use of an appended dtb invisible for mach code.

Mach code can still find out if it is an appended dtb by comparing
fw_arg1 with fw_supplied_dtb.

Signed-off-by: Jonas Gorski 
Cc: Kevin Cernekee 
Cc: Florian Fainelli 
Cc: John Crispin 
Cc: Paul Burton 
Cc: James Hogan 
Cc: Alban Bedel 
Cc: Daniel Gimpelevich 
Cc: Antony Pavlov 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13699/
Signed-off-by: Ralf Baechle

MIPS: Factor o32 specific code into signal_o32.c

2016-08-02T09:02:35+00:00

The commit ebb5e78cc634 ("MIPS: Initial implementation of a VDSO")
caused building a 64 bit kernel with support for n32 and not o32
to produce a build error:

arch/mips/kernel/signal32.c:415:11: error: ‘vdso_image_o32’ undeclared here (not in a function)
  .vdso  = &vdso_image_o32,

Fix this by moving the o32 specific code into signal_o32.c and
updating the Makefile accordingly.

Signed-off-by: Harvey Hunt 
Cc: Leonid Yegoshin 
Cc: Alex Smith 
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13690/
Signed-off-by: Ralf Baechle

MIPS: non-exec stack & heap when non-exec PT_GNU_STACK is present

2016-08-02T07:29:27+00:00

The stack and heap have both been executable by default on MIPS until
now. This patch changes the default to be non-executable, but only for
ELF binaries with a non-executable PT_GNU_STACK header present. This
does apply to both the heap & the stack, despite the name PT_GNU_STACK,
and this matches the behaviour of other architectures like ARM & x86.

Current MIPS toolchains do not produce the PT_GNU_STACK header, which
means that we can rely upon this patch not changing the behaviour of
existing binaries. The new default will only take effect for newly
compiled binaries once toolchains are updated to support PT_GNU_STACK,
and since those binaries are newly compiled they can be compiled
expecting the change in default behaviour. Again this matches the way in
which the ARM & x86 architectures handled their implementations of
non-executable memory.

Signed-off-by: Paul Burton 
Cc: Leonid Yegoshin 
Cc: Maciej Rozycki 
Cc: Faraz Shahbazker 
Cc: Raghu Gandham 
Cc: Matthew Fortune 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13765/
Signed-off-by: Ralf Baechle

MIPS: Use per-mm page to execute branch delay slot instructions

2016-08-02T07:28:53+00:00

In some cases the kernel needs to execute an instruction from the delay
slot of an emulated branch instruction. These cases include:

  - Emulated floating point branch instructions (bc1[ft]l?) for systems
    which don't include an FPU, or upon which the kernel is run with the
    "nofpu" parameter.

  - MIPSr6 systems running binaries targeting older revisions of the
    architecture, which may include branch instructions whose encodings
    are no longer valid in MIPSr6.

Executing instructions from such delay slots is done by writing the
instruction to memory followed by a trap, as part of an "emuframe", and
executing it. This avoids the requirement of an emulator for the entire
MIPS instruction set. Prior to this patch such emuframes are written to
the user stack and executed from there.

This patch moves FP branch delay emuframes off of the user stack and
into a per-mm page. Allocating a page per-mm leaves userland with access
to only what it had access to previously, and compared to other
solutions is relatively simple.

When a thread requires a delay slot emulation, it is allocated a frame.
A thread may only have one frame allocated at any one time, since it may
only ever be executing one instruction at any one time. In order to
ensure that we can free up allocated frame later, its index is recorded
in struct thread_struct. In the typical case, after executing the delay
slot instruction we'll execute a break instruction with the BRK_MEMU
code. This traps back to the kernel & leads to a call to do_dsemulret
which frees the allocated frame & moves the user PC back to the
instruction that would have executed following the emulated branch.
In some cases the delay slot instruction may be invalid, such as a
branch, or may trigger an exception. In these cases the BRK_MEMU break
instruction will not be hit. In order to ensure that frames are freed
this patch introduces dsemul_thread_cleanup() and calls it to free any
allocated frame upon thread exit. If the instruction generated an
exception & leads to a signal being delivered to the thread, or indeed
if a signal simply happens to be delivered to the thread whilst it is
executing from the struct emuframe, then we need to take care to exit
the frame appropriately. This is done by either rolling back the user PC
to the branch or advancing it to the continuation PC prior to signal
delivery, using dsemul_thread_rollback(). If this were not done then a
sigreturn would return to the struct emuframe, and if that frame had
meanwhile been used in response to an emulated branch instruction within
the signal handler then we would execute the wrong user code.

Whilst a user could theoretically place something like a compact branch
to self in a delay slot and cause their thread to become stuck in an
infinite loop with the frame never being deallocated, this would:

  - Only affect the users single process.

  - Be architecturally invalid since there would be a branch in the
    delay slot, which is forbidden.

  - Be extremely unlikely to happen by mistake, and provide a program
    with no more ability to harm the system than a simple infinite loop
    would.

If a thread requires a delay slot emulation & no frame is available to
it (ie. the process has enough other threads that all frames are
currently in use) then the thread joins a waitqueue. It will sleep until
a frame is freed by another thread in the process.

Since we now know whether a thread has an allocated frame due to our
tracking of its index, the cookie field of struct emuframe is removed as
we can be more certain whether we have a valid frame. Since a thread may
only ever have a single frame at any given time, the epc field of struct
emuframe is also removed & the PC to continue from is instead stored in
struct thread_struct. Together these changes simplify & shrink struct
emuframe somewhat, allowing twice as many frames to fit into the page
allocated for them.

The primary benefit of this patch is that we are now free to mark the
user stack non-executable where that is possible.

Signed-off-by: Paul Burton 
Cc: Leonid Yegoshin 
Cc: Maciej Rozycki 
Cc: Faraz Shahbazker 
Cc: Raghu Gandham 
Cc: Matthew Fortune 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13764/
Signed-off-by: Ralf Baechle