linux-imx/arch/arm/mm/Kconfig

SPDX-License-Identifier: GPL-2.0

comment "Processor Type"

Select CPU types depending on the architecture selected. This selects

which CPUs we support in the kernel image, and the compiler instruction

optimiser behaviour.

ARM7TDMI

config CPU_ARM7TDMI bool depends on !MMU select CPU_32v4T select CPU_ABRT_LV4T select CPU_CACHE_V4 select CPU_PABRT_LEGACY help A 32-bit RISC microprocessor based on the ARM7 processor core which has no memory control unit and cache.

  Say Y if you want support for the ARM7TDMI processor.
  Otherwise, say N.

ARM720T

config CPU_ARM720T bool select CPU_32v4T select CPU_ABRT_LV4T select CPU_CACHE_V4 select CPU_CACHE_VIVT select CPU_COPY_V4WT if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WT if MMU help A 32-bit RISC processor with 8kByte Cache, Write Buffer and MMU built around an ARM7TDMI core.

  Say Y if you want support for the ARM720T processor.
  Otherwise, say N.

ARM740T

config CPU_ARM740T bool depends on !MMU select CPU_32v4T select CPU_ABRT_LV4T select CPU_CACHE_V4 select CPU_CP15_MPU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE help A 32-bit RISC processor with 8KB cache or 4KB variants, write buffer and MPU(Protection Unit) built around an ARM7TDMI core.

  Say Y if you want support for the ARM740T processor.
  Otherwise, say N.

ARM9TDMI

config CPU_ARM9TDMI bool depends on !MMU select CPU_32v4T select CPU_ABRT_NOMMU select CPU_CACHE_V4 select CPU_PABRT_LEGACY help A 32-bit RISC microprocessor based on the ARM9 processor core which has no memory control unit and cache.

  Say Y if you want support for the ARM9TDMI processor.
  Otherwise, say N.

ARM920T

config CPU_ARM920T bool select CPU_32v4T select CPU_ABRT_EV4T select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU help The ARM920T is licensed to be produced by numerous vendors, and is used in the Cirrus EP93xx and the Samsung S3C2410.

  Say Y if you want support for the ARM920T processor.
  Otherwise, say N.

ARM922T

config CPU_ARM922T bool select CPU_32v4T select CPU_ABRT_EV4T select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU help The ARM922T is a version of the ARM920T, but with smaller instruction and data caches. It is used in Altera's Excalibur XA device family and the ARM Integrator.

  Say Y if you want support for the ARM922T processor.
  Otherwise, say N.

ARM925T

config CPU_ARM925T bool select CPU_32v4T select CPU_ABRT_EV4T select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU help The ARM925T is a mix between the ARM920T and ARM926T, but with different instruction and data caches. It is used in TI's OMAP device family.

  Say Y if you want support for the ARM925T processor.
  Otherwise, say N.

ARM926T

config CPU_ARM926T bool select CPU_32v5 select CPU_ABRT_EV5TJ select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU help This is a variant of the ARM920. It has slightly different instruction sequences for cache and TLB operations. Curiously, there is no documentation on it at the ARM corporate website.

  Say Y if you want support for the ARM926T processor.
  Otherwise, say N.

FA526

config CPU_FA526 bool select CPU_32v4 select CPU_ABRT_EV4 select CPU_CACHE_FA select CPU_CACHE_VIVT select CPU_COPY_FA if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_TLB_FA if MMU help The FA526 is a version of the ARMv4 compatible processor with Branch Target Buffer, Unified TLB and cache line size 16.

  Say Y if you want support for the FA526 processor.
  Otherwise, say N.

ARM940T

config CPU_ARM940T bool depends on !MMU select CPU_32v4T select CPU_ABRT_NOMMU select CPU_CACHE_VIVT select CPU_CP15_MPU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE help ARM940T is a member of the ARM9TDMI family of general- purpose microprocessors with MPU and separate 4KB instruction and 4KB data cases, each with a 4-word line length.

  Say Y if you want support for the ARM940T processor.
  Otherwise, say N.

ARM946E-S

config CPU_ARM946E bool depends on !MMU select CPU_32v5 select CPU_ABRT_NOMMU select CPU_CACHE_VIVT select CPU_CP15_MPU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE help ARM946E-S is a member of the ARM9E-S family of high- performance, 32-bit system-on-chip processor solutions. The TCM and ARMv5TE 32-bit instruction set is supported.

  Say Y if you want support for the ARM946E-S processor.
  Otherwise, say N.

ARM1020 - needs validating

config CPU_ARM1020 bool select CPU_32v5 select CPU_ABRT_EV4T select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU help The ARM1020 is the 32K cached version of the ARM10 processor, with an addition of a floating-point unit.

  Say Y if you want support for the ARM1020 processor.
  Otherwise, say N.

ARM1020E - needs validating

config CPU_ARM1020E bool depends on n select CPU_32v5 select CPU_ABRT_EV4T select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU

ARM1022E

config CPU_ARM1022 bool select CPU_32v5 select CPU_ABRT_EV4T select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU # can probably do better select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU help The ARM1022E is an implementation of the ARMv5TE architecture based upon the ARM10 integer core with a 16KiB L1 Harvard cache, embedded trace macrocell, and a floating-point unit.

  Say Y if you want support for the ARM1022E processor.
  Otherwise, say N.

ARM1026EJ-S

config CPU_ARM1026 bool select CPU_32v5 select CPU_ABRT_EV5T # But need Jazelle, but EV5TJ ignores bit 10 select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU # can probably do better select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU help The ARM1026EJ-S is an implementation of the ARMv5TEJ architecture based upon the ARM10 integer core.

  Say Y if you want support for the ARM1026EJ-S processor.
  Otherwise, say N.

SA110

config CPU_SA110 bool select CPU_32v3 if ARCH_RPC select CPU_32v4 if !ARCH_RPC select CPU_ABRT_EV4 select CPU_CACHE_V4WB select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_TLB_V4WB if MMU help The Intel StrongARM(R) SA-110 is a 32-bit microprocessor and is available at five speeds ranging from 100 MHz to 233 MHz. More information is available at http://developer.intel.com/design/strong/sa110.htm.

  Say Y if you want support for the SA-110 processor.
  Otherwise, say N.

SA1100

config CPU_SA1100 bool select CPU_32v4 select CPU_ABRT_EV4 select CPU_CACHE_V4WB select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_TLB_V4WB if MMU

XScale

config CPU_XSCALE bool select CPU_32v5 select CPU_ABRT_EV5T select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU

XScale Core Version 3

config CPU_XSC3 bool select CPU_32v5 select CPU_ABRT_EV5T select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU select IO_36

Marvell PJ1 (Mohawk)

config CPU_MOHAWK bool select CPU_32v5 select CPU_ABRT_EV5T select CPU_CACHE_VIVT select CPU_COPY_V4WB if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_V4WBI if MMU

Feroceon

config CPU_FEROCEON bool select CPU_32v5 select CPU_ABRT_EV5T select CPU_CACHE_VIVT select CPU_COPY_FEROCEON if MMU select CPU_CP15_MMU select CPU_PABRT_LEGACY select CPU_THUMB_CAPABLE select CPU_TLB_FEROCEON if MMU

config CPU_FEROCEON_OLD_ID bool "Accept early Feroceon cores with an ARM926 ID" depends on CPU_FEROCEON && !CPU_ARM926T default y help This enables the usage of some old Feroceon cores for which the CPU ID is equal to the ARM926 ID. Relevant for Feroceon-1850 and early Feroceon-2850.

Marvell PJ4

config CPU_PJ4 bool select ARM_THUMBEE select CPU_V7

config CPU_PJ4B bool select CPU_V7

ARMv6

config CPU_V6 bool select CPU_32v6 select CPU_ABRT_EV6 select CPU_CACHE_V6 select CPU_CACHE_VIPT select CPU_COPY_V6 if MMU select CPU_CP15_MMU select CPU_HAS_ASID if MMU select CPU_PABRT_V6 select CPU_THUMB_CAPABLE select CPU_TLB_V6 if MMU select SMP_ON_UP if SMP

ARMv6k

config CPU_V6K bool select CPU_32v6 select CPU_32v6K select CPU_ABRT_EV6 select CPU_CACHE_V6 select CPU_CACHE_VIPT select CPU_COPY_V6 if MMU select CPU_CP15_MMU select CPU_HAS_ASID if MMU select CPU_PABRT_V6 select CPU_THUMB_CAPABLE select CPU_TLB_V6 if MMU

ARMv7 and ARMv8 architectures

config CPU_V7 bool select CPU_32v6K select CPU_32v7 select CPU_ABRT_EV7 select CPU_CACHE_V7 select CPU_CACHE_VIPT select CPU_COPY_V6 if MMU select CPU_CP15_MMU if MMU select CPU_CP15_MPU if !MMU select CPU_HAS_ASID if MMU select CPU_PABRT_V7 select CPU_SPECTRE if MMU select CPU_THUMB_CAPABLE select CPU_TLB_V7 if MMU

ARMv7M

config CPU_V7M bool select CPU_32v7M select CPU_ABRT_NOMMU select CPU_CACHE_V7M select CPU_CACHE_NOP select CPU_PABRT_LEGACY select CPU_THUMBONLY

config CPU_THUMBONLY bool select CPU_THUMB_CAPABLE # There are no CPUs available with MMU that don't implement an ARM ISA: depends on !MMU help Select this if your CPU doesn't support the 32 bit ARM instructions.

config CPU_THUMB_CAPABLE bool help Select this if your CPU can support Thumb mode.

Figure out what processor architecture version we should be using.

This defines the compiler instruction set which depends on the machine type.

config CPU_32v3 bool select CPU_USE_DOMAINS if MMU select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU select CPU_NO_EFFICIENT_FFS

config CPU_32v4 bool select CPU_USE_DOMAINS if MMU select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU select CPU_NO_EFFICIENT_FFS

config CPU_32v4T bool select CPU_USE_DOMAINS if MMU select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU select CPU_NO_EFFICIENT_FFS

config CPU_32v5 bool select CPU_USE_DOMAINS if MMU select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU

config CPU_32v6 bool select TLS_REG_EMUL if !CPU_32v6K && !MMU

config CPU_32v6K bool

config CPU_32v7 bool

config CPU_32v7M bool

The abort model

config CPU_ABRT_NOMMU bool

config CPU_ABRT_EV4 bool

config CPU_ABRT_EV4T bool

config CPU_ABRT_LV4T bool

config CPU_ABRT_EV5T bool

config CPU_ABRT_EV5TJ bool

config CPU_ABRT_EV6 bool

config CPU_ABRT_EV7 bool

config CPU_PABRT_LEGACY bool

config CPU_PABRT_V6 bool

config CPU_PABRT_V7 bool

The cache model

config CPU_CACHE_V4 bool

config CPU_CACHE_V4WT bool

config CPU_CACHE_V4WB bool

config CPU_CACHE_V6 bool

config CPU_CACHE_V7 bool

config CPU_CACHE_NOP bool

config CPU_CACHE_VIVT bool

config CPU_CACHE_VIPT bool

config CPU_CACHE_FA bool

config CPU_CACHE_V7M bool

if MMU

The copy-page model

config CPU_COPY_V4WT bool

config CPU_COPY_V4WB bool

config CPU_COPY_FEROCEON bool

config CPU_COPY_FA bool

config CPU_COPY_V6 bool

This selects the TLB model

config CPU_TLB_V4WT bool help ARM Architecture Version 4 TLB with writethrough cache.

config CPU_TLB_V4WB bool help ARM Architecture Version 4 TLB with writeback cache.

config CPU_TLB_V4WBI bool help ARM Architecture Version 4 TLB with writeback cache and invalidate instruction cache entry.

config CPU_TLB_FEROCEON bool help Feroceon TLB (v4wbi with non-outer-cachable page table walks).

config CPU_TLB_FA bool help Faraday ARM FA526 architecture, unified TLB with writeback cache and invalidate instruction cache entry. Branch target buffer is also supported.

config CPU_TLB_V6 bool

config CPU_TLB_V7 bool

endif

config CPU_HAS_ASID bool help This indicates whether the CPU has the ASID register; used to tag TLB and possibly cache entries.

config CPU_CP15 bool help Processor has the CP15 register.

config CPU_CP15_MMU bool select CPU_CP15 help Processor has the CP15 register, which has MMU related registers.

config CPU_CP15_MPU bool select CPU_CP15 help Processor has the CP15 register, which has MPU related registers.

config CPU_USE_DOMAINS bool help This option enables or disables the use of domain switching using the DACR (domain access control register) to protect memory domains from each other. In Linux we use three domains: kernel, user and IO. The domains are used to protect userspace from kernelspace and to handle IO-space as a special type of memory by assigning manager or client roles to running code (such as a process).

config CPU_V7M_NUM_IRQ int "Number of external interrupts connected to the NVIC" depends on CPU_V7M default 90 if ARCH_STM32 default 112 if SOC_VF610 default 240 help This option indicates the number of interrupts connected to the NVIC. The value can be larger than the real number of interrupts supported by the system, but must not be lower. The default value is 240, corresponding to the maximum number of interrupts supported by the NVIC on Cortex-M family.

  If unsure, keep default value.

CPU supports 36-bit I/O

config IO_36 bool

comment "Processor Features"

config ARM_LPAE bool "Support for the Large Physical Address Extension" depends on MMU && CPU_32v7 && !CPU_32v6 && !CPU_32v5 &&
!CPU_32v4 && !CPU_32v3 select PHYS_ADDR_T_64BIT select SWIOTLB help Say Y if you have an ARMv7 processor supporting the LPAE page table format and you would like to access memory beyond the 4GB limit. The resulting kernel image will not run on processors without the LPA extension.

  If unsure, say N.

config ARM_PV_FIXUP def_bool y depends on ARM_LPAE && ARM_PATCH_PHYS_VIRT && ARCH_KEYSTONE

config ARM_THUMB bool "Support Thumb user binaries" if !CPU_THUMBONLY && EXPERT depends on CPU_THUMB_CAPABLE && !CPU_32v4 default y help Say Y if you want to include kernel support for running user space Thumb binaries.

  The Thumb instruction set is a compressed form of the standard ARM
  instruction set resulting in smaller binaries at the expense of
  slightly less efficient code.

  If this option is disabled, and you run userspace that switches to
  Thumb mode, signal handling will not work correctly, resulting in
  segmentation faults or illegal instruction aborts.

  If you don't know what this all is, saying Y is a safe choice.

config ARM_THUMBEE bool "Enable ThumbEE CPU extension" depends on CPU_V7 help Say Y here if you have a CPU with the ThumbEE extension and code to make use of it. Say N for code that can run on CPUs without ThumbEE.

config ARM_VIRT_EXT bool default y if CPU_V7 help Enable the kernel to make use of the ARM Virtualization Extensions to install hypervisors without run-time firmware assistance.

  A compliant bootloader is required in order to make maximum
  use of this feature.  Refer to Documentation/arch/arm/booting.rst for
  details.

config SWP_EMULATE bool "Emulate SWP/SWPB instructions" if !SMP depends on CPU_V7 default y if SMP select HAVE_PROC_CPU if PROC_FS help ARMv6 architecture deprecates use of the SWP/SWPB instructions. ARMv7 multiprocessing extensions introduce the ability to disable these instructions, triggering an undefined instruction exception when executed. Say Y here to enable software emulation of these instructions for userspace (not kernel) using LDREX/STREX. Also creates /proc/cpu/swp_emulation for statistics.

  In some older versions of glibc [<=2.8] SWP is used during futex
  trylock() operations with the assumption that the code will not
  be preempted. This invalid assumption may be more likely to fail
  with SWP emulation enabled, leading to deadlock of the user
  application.

  NOTE: when accessing uncached shared regions, LDREX/STREX rely
  on an external transaction monitoring block called a global
  monitor to maintain update atomicity. If your system does not
  implement a global monitor, this option can cause programs that
  perform SWP operations to uncached memory to deadlock.

  If unsure, say Y.

choice prompt "CPU Endianness" default CPU_LITTLE_ENDIAN

config CPU_LITTLE_ENDIAN bool "Built little-endian kernel" help Say Y if you plan on running a kernel in little-endian mode. This is the default and is used in practically all modern user space builds.

config CPU_BIG_ENDIAN bool "Build big-endian kernel" depends on !LD_IS_LLD help Say Y if you plan on running a kernel in big-endian mode. This works on many machines using ARMv6 or newer processors but requires big-endian user space.

  The only ARMv5 platform with big-endian support is
  Intel IXP4xx.

endchoice

config CPU_ENDIAN_BE8 bool depends on CPU_BIG_ENDIAN default CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M help Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.

config CPU_ENDIAN_BE32 bool depends on CPU_BIG_ENDIAN default !CPU_ENDIAN_BE8 help Support for the BE-32 (big-endian) mode on pre-ARMv6 processors.

config CPU_HIGH_VECTOR depends on !MMU && CPU_CP15 && !CPU_ARM740T bool "Select the High exception vector" help Say Y here to select high exception vector(0xFFFF0000~). The exception vector can vary depending on the platform design in nommu mode. If your platform needs to select high exception vector, say Y. Otherwise or if you are unsure, say N, and the low exception vector (0x00000000~) will be used.

config CPU_ICACHE_DISABLE bool "Disable I-Cache (I-bit)" depends on (CPU_CP15 && !(CPU_ARM720T || CPU_ARM740T || CPU_XSCALE || CPU_XSC3)) || CPU_V7M help Say Y here to disable the processor instruction cache. Unless you have a reason not to or are unsure, say N.

config CPU_ICACHE_MISMATCH_WORKAROUND bool "Workaround for I-Cache line size mismatch between CPU cores" depends on SMP && CPU_V7 help Some big.LITTLE systems have I-Cache line size mismatch between LITTLE and big cores. Say Y here to enable a workaround for proper I-Cache support on such systems. If unsure, say N.

config CPU_DCACHE_DISABLE bool "Disable D-Cache (C-bit)" depends on (CPU_CP15 && !SMP) || CPU_V7M help Say Y here to disable the processor data cache. Unless you have a reason not to or are unsure, say N.

config CPU_DCACHE_SIZE hex depends on CPU_ARM740T || CPU_ARM946E default 0x00001000 if CPU_ARM740T default 0x00002000 # default size for ARM946E-S help Some cores are synthesizable to have various sized cache. For ARM946E-S case, it can vary from 0KB to 1MB. To support such cache operations, it is efficient to know the size before compile time. If your SoC is configured to have a different size, define the value here with proper conditions.

config CPU_DCACHE_WRITETHROUGH bool "Force write through D-cache" depends on (CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || CPU_ARM1020 || CPU_FA526) && !CPU_DCACHE_DISABLE default y if CPU_ARM925T help Say Y here to use the data cache in writethrough mode. Unless you specifically require this or are unsure, say N.

config CPU_CACHE_ROUND_ROBIN bool "Round robin I and D cache replacement algorithm" depends on (CPU_ARM926T || CPU_ARM946E || CPU_ARM1020) && (!CPU_ICACHE_DISABLE || !CPU_DCACHE_DISABLE) help Say Y here to use the predictable round-robin cache replacement policy. Unless you specifically require this or are unsure, say N.

config CPU_BPREDICT_DISABLE bool "Disable branch prediction" depends on CPU_ARM1020 || CPU_V6 || CPU_V6K || CPU_MOHAWK || CPU_XSC3 || CPU_V7 || CPU_FA526 || CPU_V7M help Say Y here to disable branch prediction. If unsure, say N.

config CPU_SPECTRE bool select GENERIC_CPU_VULNERABILITIES

config HARDEN_BRANCH_PREDICTOR bool "Harden the branch predictor against aliasing attacks" if EXPERT depends on CPU_SPECTRE default y help Speculation attacks against some high-performance processors rely on being able to manipulate the branch predictor for a victim context by executing aliasing branches in the attacker context. Such attacks can be partially mitigated against by clearing internal branch predictor state and limiting the prediction logic in some situations.

   This config option will take CPU-specific actions to harden
   the branch predictor against aliasing attacks and may rely on
   specific instruction sequences or control bits being set by
   the system firmware.

   If unsure, say Y.

config HARDEN_BRANCH_HISTORY bool "Harden Spectre style attacks against branch history" if EXPERT depends on CPU_SPECTRE default y help Speculation attacks against some high-performance processors can make use of branch history to influence future speculation. When taking an exception, a sequence of branches overwrites the branch history, or branch history is invalidated.

config TLS_REG_EMUL bool select NEED_KUSER_HELPERS help An SMP system using a pre-ARMv6 processor (there are apparently a few prototypes like that in existence) and therefore access to that required register must be emulated.

config NEED_KUSER_HELPERS bool

config KUSER_HELPERS bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS depends on MMU default y help Warning: disabling this option may break user programs.

  Provide kuser helpers in the vector page.  The kernel provides
  helper code to userspace in read only form at a fixed location
  in the high vector page to allow userspace to be independent of
  the CPU type fitted to the system.  This permits binaries to be
  run on ARMv4 through to ARMv7 without modification.

  See Documentation/arch/arm/kernel_user_helpers.rst for details.

  However, the fixed address nature of these helpers can be used
  by ROP (return orientated programming) authors when creating
  exploits.

  If all of the binaries and libraries which run on your platform
  are built specifically for your platform, and make no use of
  these helpers, then you can turn this option off to hinder
  such exploits. However, in that case, if a binary or library
  relying on those helpers is run, it will receive a SIGILL signal,
  which will terminate the program.

  Say N here only if you are absolutely certain that you do not
  need these helpers; otherwise, the safe option is to say Y.

config VDSO bool "Enable VDSO for acceleration of some system calls" depends on AEABI && MMU && CPU_V7 default y if ARM_ARCH_TIMER select HAVE_GENERIC_VDSO select GENERIC_TIME_VSYSCALL select GENERIC_VDSO_32 select GENERIC_GETTIMEOFDAY help Place in the process address space an ELF shared object providing fast implementations of gettimeofday and clock_gettime. Systems that implement the ARM architected timer will receive maximum benefit.

  You must have glibc 2.22 or later for programs to seamlessly
  take advantage of this.

config OUTER_CACHE bool

config OUTER_CACHE_SYNC bool select ARM_HEAVY_MB help The outer cache has a outer_cache_fns.sync function pointer that can be used to drain the write buffer of the outer cache.

config CACHE_B15_RAC bool "Enable the Broadcom Brahma-B15 read-ahead cache controller" depends on ARCH_BRCMSTB default y help This option enables the Broadcom Brahma-B15 read-ahead cache controller. If disabled, the read-ahead cache remains off.

config CACHE_FEROCEON_L2 bool "Enable the Feroceon L2 cache controller" depends on ARCH_MV78XX0 || ARCH_MVEBU default y select OUTER_CACHE help This option enables the Feroceon L2 cache controller.

config CACHE_FEROCEON_L2_WRITETHROUGH bool "Force Feroceon L2 cache write through" depends on CACHE_FEROCEON_L2 help Say Y here to use the Feroceon L2 cache in writethrough mode. Unless you specifically require this, say N for writeback mode.

config MIGHT_HAVE_CACHE_L2X0 bool help This option should be selected by machines which have a L2x0 or PL310 cache controller, but where its use is optional.

  The only effect of this option is to make CACHE_L2X0 and
  related options available to the user for configuration.

  Boards or SoCs which always require the cache controller
  support to be present should select CACHE_L2X0 directly
  instead of this option, thus preventing the user from
  inadvertently configuring a broken kernel.

config CACHE_L2X0 bool "Enable the L2x0 outer cache controller" if MIGHT_HAVE_CACHE_L2X0 default MIGHT_HAVE_CACHE_L2X0 select OUTER_CACHE select OUTER_CACHE_SYNC help This option enables the L2x0 PrimeCell.

config CACHE_L2X0_PMU bool "L2x0 performance monitor support" if CACHE_L2X0 depends on PERF_EVENTS help This option enables support for the performance monitoring features of the L220 and PL310 outer cache controllers.

if CACHE_L2X0

config PL310_ERRATA_588369 bool "PL310 errata: Clean & Invalidate maintenance operations do not invalidate clean lines" help The PL310 L2 cache controller implements three types of Clean & Invalidate maintenance operations: by Physical Address (offset 0x7F0), by Index/Way (0x7F8) and by Way (0x7FC). They are architecturally defined to behave as the execution of a clean operation followed immediately by an invalidate operation, both performing to the same memory location. This functionality is not correctly implemented in PL310 prior to r2p0 (fixed in r2p0) as clean lines are not invalidated as a result of these operations.

config PL310_ERRATA_727915 bool "PL310 errata: Background Clean & Invalidate by Way operation can cause data corruption" help PL310 implements the Clean & Invalidate by Way L2 cache maintenance operation (offset 0x7FC). This operation runs in background so that PL310 can handle normal accesses while it is in progress. Under very rare circumstances, due to this erratum, write data can be lost when PL310 treats a cacheable write transaction during a Clean & Invalidate by Way operation. Revisions prior to r3p1 are affected by this errata (fixed in r3p1).

config PL310_ERRATA_753970 bool "PL310 errata: cache sync operation may be faulty" help This option enables the workaround for the 753970 PL310 (r3p0) erratum.

  Under some condition the effect of cache sync operation on
  the store buffer still remains when the operation completes.
  This means that the store buffer is always asked to drain and
  this prevents it from merging any further writes. The workaround
  is to replace the normal offset of cache sync operation (0x730)
  by another offset targeting an unmapped PL310 register 0x740.
  This has the same effect as the cache sync operation: store buffer
  drain and waiting for all buffers empty.

config PL310_ERRATA_769419 bool "PL310 errata: no automatic Store Buffer drain" help On revisions of the PL310 prior to r3p2, the Store Buffer does not automatically drain. This can cause normal, non-cacheable writes to be retained when the memory system is idle, leading to suboptimal I/O performance for drivers using coherent DMA. This option adds a write barrier to the cpu_idle loop so that, on systems with an outer cache, the store buffer is drained explicitly.

endif

config CACHE_TAUROS2 bool "Enable the Tauros2 L2 cache controller" depends on (CPU_MOHAWK || CPU_PJ4) default y select OUTER_CACHE help This option enables the Tauros2 L2 cache controller (as found on PJ1/PJ4).

config CACHE_UNIPHIER bool "Enable the UniPhier outer cache controller" depends on ARCH_UNIPHIER select ARM_L1_CACHE_SHIFT_7 select OUTER_CACHE select OUTER_CACHE_SYNC help This option enables the UniPhier outer cache (system cache) controller.

config CACHE_XSC3L2 bool "Enable the L2 cache on XScale3" depends on CPU_XSC3 default y select OUTER_CACHE help This option enables the L2 cache on XScale3.

config ARM_L1_CACHE_SHIFT_6 bool default y if CPU_V7 help Setting ARM L1 cache line size to 64 Bytes.

config ARM_L1_CACHE_SHIFT_7 bool help Setting ARM L1 cache line size to 128 Bytes.

config ARM_L1_CACHE_SHIFT int default 7 if ARM_L1_CACHE_SHIFT_7 default 6 if ARM_L1_CACHE_SHIFT_6 default 5

config ARM_DMA_MEM_BUFFERABLE bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K || CPU_V7M) && !CPU_V7 default y if CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M help Historically, the kernel has used strongly ordered mappings to provide DMA coherent memory. With the advent of ARMv7, mapping memory with differing types results in unpredictable behaviour, so on these CPUs, this option is forced on.

  Multiple mappings with differing attributes is also unpredictable
  on ARMv6 CPUs, but since they do not have aggressive speculative
  prefetch, no harm appears to occur.

  However, drivers may be missing the necessary barriers for ARMv6,
  and therefore turning this on may result in unpredictable driver
  behaviour.  Therefore, we offer this as an option.

  On some of the beefier ARMv7-M machines (with DMA and write
  buffers) you likely want this enabled, while those that
  didn't need it until now also won't need it in the future.

  You are recommended say 'Y' here and debug any affected drivers.

config ARM_HEAVY_MB bool

config DEBUG_ALIGN_RODATA bool "Make rodata strictly non-executable" depends on STRICT_KERNEL_RWX default y help If this is set, rodata will be made explicitly non-executable. This provides protection on the rare chance that attackers might find and use ROP gadgets that exist in the rodata section. This adds an additional section-aligned split of rodata from kernel text so it can be made explicitly non-executable. This padding may waste memory space to gain the additional protection.