# SPDX-License-Identifier: GPL-2.0
#
# General architecture dependent options
#

#
# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
# override the default values in this file.
#
source "arch/$(SRCARCH)/Kconfig"

menu "General architecture-dependent options"

config CRASH_CORE
        bool

config KEXEC_CORE
        select CRASH_CORE
        bool

config HAVE_IMA_KEXEC
        bool

config HOTPLUG_SMT
        bool

config OPROFILE
        tristate "OProfile system profiling"
        depends on PROFILING
        depends on HAVE_OPROFILE
        select RING_BUFFER
        select RING_BUFFER_ALLOW_SWAP
        help
          OProfile is a profiling system capable of profiling the
          whole system, include the kernel, kernel modules, libraries,
          and applications.

          If unsure, say N.

config OPROFILE_EVENT_MULTIPLEX
        bool "OProfile multiplexing support (EXPERIMENTAL)"
        default n
        depends on OPROFILE && X86
        help
          The number of hardware counters is limited. The multiplexing
          feature enables OProfile to gather more events than counters
          are provided by the hardware. This is realized by switching
          between events at a user specified time interval.

          If unsure, say N.

config HAVE_OPROFILE
        bool

config OPROFILE_NMI_TIMER
        def_bool y
        depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64

config KPROBES
        bool "Kprobes"
        depends on MODULES
        depends on HAVE_KPROBES
        select KALLSYMS
        help
          Kprobes allows you to trap at almost any kernel address and
          execute a callback function.  register_kprobe() establishes
          a probepoint and specifies the callback.  Kprobes is useful
          for kernel debugging, non-intrusive instrumentation and testing.
          If in doubt, say "N".

config JUMP_LABEL
       bool "Optimize very unlikely/likely branches"
       depends on HAVE_ARCH_JUMP_LABEL
       depends on CC_HAS_ASM_GOTO
       help
         This option enables a transparent branch optimization that
         makes certain almost-always-true or almost-always-false branch
         conditions even cheaper to execute within the kernel.

         Certain performance-sensitive kernel code, such as trace points,
         scheduler functionality, networking code and KVM have such
         branches and include support for this optimization technique.

         If it is detected that the compiler has support for "asm goto",
         the kernel will compile such branches with just a nop
         instruction. When the condition flag is toggled to true, the
         nop will be converted to a jump instruction to execute the
         conditional block of instructions.

         This technique lowers overhead and stress on the branch prediction
         of the processor and generally makes the kernel faster. The update
         of the condition is slower, but those are always very rare.

         ( On 32-bit x86, the necessary options added to the compiler
           flags may increase the size of the kernel slightly. )

config STATIC_KEYS_SELFTEST
        bool "Static key selftest"
        depends on JUMP_LABEL
        help
          Boot time self-test of the branch patching code.

config OPTPROBES
        def_bool y
        depends on KPROBES && HAVE_OPTPROBES
        select TASKS_RCU if PREEMPT

config KPROBES_ON_FTRACE
        def_bool y
        depends on KPROBES && HAVE_KPROBES_ON_FTRACE
        depends on DYNAMIC_FTRACE_WITH_REGS
        help
         If function tracer is enabled and the arch supports full
         passing of pt_regs to function tracing, then kprobes can
         optimize on top of function tracing.

config UPROBES
        def_bool n
        depends on ARCH_SUPPORTS_UPROBES
        help
          Uprobes is the user-space counterpart to kprobes: they
          enable instrumentation applications (such as 'perf probe')
          to establish unintrusive probes in user-space binaries and
          libraries, by executing handler functions when the probes
          are hit by user-space applications.

          ( These probes come in the form of single-byte breakpoints,
            managed by the kernel and kept transparent to the probed
            application. )

config HAVE_64BIT_ALIGNED_ACCESS
        def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
        help
          Some architectures require 64 bit accesses to be 64 bit
          aligned, which also requires structs containing 64 bit values
          to be 64 bit aligned too. This includes some 32 bit
          architectures which can do 64 bit accesses, as well as 64 bit
          architectures without unaligned access.

          This symbol should be selected by an architecture if 64 bit
          accesses are required to be 64 bit aligned in this way even
          though it is not a 64 bit architecture.

          See Documentation/unaligned-memory-access.txt for more
          information on the topic of unaligned memory accesses.

config HAVE_EFFICIENT_UNALIGNED_ACCESS
        bool
        help
          Some architectures are unable to perform unaligned accesses
          without the use of get_unaligned/put_unaligned. Others are
          unable to perform such accesses efficiently (e.g. trap on
          unaligned access and require fixing it up in the exception
          handler.)

          This symbol should be selected by an architecture if it can
          perform unaligned accesses efficiently to allow different
          code paths to be selected for these cases. Some network
          drivers, for example, could opt to not fix up alignment
          problems with received packets if doing so would not help
          much.

          See Documentation/unaligned-memory-access.txt for more
          information on the topic of unaligned memory accesses.

config ARCH_USE_BUILTIN_BSWAP
       bool
       help
         Modern versions of GCC (since 4.4) have builtin functions
         for handling byte-swapping. Using these, instead of the old
         inline assembler that the architecture code provides in the
         __arch_bswapXX() macros, allows the compiler to see what's
         happening and offers more opportunity for optimisation. In
         particular, the compiler will be able to combine the byteswap
         with a nearby load or store and use load-and-swap or
         store-and-swap instructions if the architecture has them. It
         should almost *never* result in code which is worse than the
         hand-coded assembler in <asm/swab.h>.  But just in case it
         does, the use of the builtins is optional.

         Any architecture with load-and-swap or store-and-swap
         instructions should set this. And it shouldn't hurt to set it
         on architectures that don't have such instructions.

config KRETPROBES
        def_bool y
        depends on KPROBES && HAVE_KRETPROBES

config USER_RETURN_NOTIFIER
        bool
        depends on HAVE_USER_RETURN_NOTIFIER
        help
          Provide a kernel-internal notification when a cpu is about to
          switch to user mode.

config HAVE_IOREMAP_PROT
        bool

config HAVE_KPROBES
        bool

config HAVE_KRETPROBES
        bool

config HAVE_OPTPROBES
        bool

config HAVE_KPROBES_ON_FTRACE
        bool

config HAVE_FUNCTION_ERROR_INJECTION
        bool

config HAVE_NMI
        bool

#
# An arch should select this if it provides all these things:
#
#       task_pt_regs()          in asm/processor.h or asm/ptrace.h
#       arch_has_single_step()  if there is hardware single-step support
#       arch_has_block_step()   if there is hardware block-step support
#       asm/syscall.h           supplying asm-generic/syscall.h interface
#       linux/regset.h          user_regset interfaces
#       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
#       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
#       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
#       signal delivery         calls tracehook_signal_handler()
#
config HAVE_ARCH_TRACEHOOK
        bool

config HAVE_DMA_CONTIGUOUS
        bool

config GENERIC_SMP_IDLE_THREAD
       bool

config GENERIC_IDLE_POLL_SETUP
       bool

config ARCH_HAS_FORTIFY_SOURCE
        bool
        help
          An architecture should select this when it can successfully
          build and run with CONFIG_FORTIFY_SOURCE.

#
# Select if the arch provides a historic keepinit alias for the retain_initrd
# command line option
#
config ARCH_HAS_KEEPINITRD
        bool

# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
config ARCH_HAS_SET_MEMORY
        bool

# Select if arch has all set_direct_map_invalid/default() functions
config ARCH_HAS_SET_DIRECT_MAP
        bool

# Select if arch init_task must go in the __init_task_data section
config ARCH_TASK_STRUCT_ON_STACK
       bool

# Select if arch has its private alloc_task_struct() function
config ARCH_TASK_STRUCT_ALLOCATOR
        bool

config HAVE_ARCH_THREAD_STRUCT_WHITELIST
        bool
        depends on !ARCH_TASK_STRUCT_ALLOCATOR
        help
          An architecture should select this to provide hardened usercopy
          knowledge about what region of the thread_struct should be
          whitelisted for copying to userspace. Normally this is only the
          FPU registers. Specifically, arch_thread_struct_whitelist()
          should be implemented. Without this, the entire thread_struct
          field in task_struct will be left whitelisted.

# Select if arch has its private alloc_thread_stack() function
config ARCH_THREAD_STACK_ALLOCATOR
        bool

# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
config ARCH_WANTS_DYNAMIC_TASK_STRUCT
        bool

config ARCH_32BIT_OFF_T
        bool
        depends on !64BIT
        help
          All new 32-bit architectures should have 64-bit off_t type on
          userspace side which corresponds to the loff_t kernel type. This
          is the requirement for modern ABIs. Some existing architectures
          still support 32-bit off_t. This option is enabled for all such
          architectures explicitly.

config HAVE_REGS_AND_STACK_ACCESS_API
        bool
        help
          This symbol should be selected by an architecure if it supports
          the API needed to access registers and stack entries from pt_regs,
          declared in asm/ptrace.h
          For example the kprobes-based event tracer needs this API.

config HAVE_RSEQ
        bool
        depends on HAVE_REGS_AND_STACK_ACCESS_API
        help
          This symbol should be selected by an architecture if it
          supports an implementation of restartable sequences.

config HAVE_FUNCTION_ARG_ACCESS_API
        bool
        help
          This symbol should be selected by an architecure if it supports
          the API needed to access function arguments from pt_regs,
          declared in asm/ptrace.h

config HAVE_CLK
        bool
        help
          The <linux/clk.h> calls support software clock gating and
          thus are a key power management tool on many systems.

config HAVE_HW_BREAKPOINT
        bool
        depends on PERF_EVENTS

config HAVE_MIXED_BREAKPOINTS_REGS
        bool
        depends on HAVE_HW_BREAKPOINT
        help
          Depending on the arch implementation of hardware breakpoints,
          some of them have separate registers for data and instruction
          breakpoints addresses, others have mixed registers to store
          them but define the access type in a control register.
          Select this option if your arch implements breakpoints under the
          latter fashion.

config HAVE_USER_RETURN_NOTIFIER
        bool

config HAVE_PERF_EVENTS_NMI
        bool
        help
          System hardware can generate an NMI using the perf event
          subsystem.  Also has support for calculating CPU cycle events
          to determine how many clock cycles in a given period.

config HAVE_HARDLOCKUP_DETECTOR_PERF
        bool
        depends on HAVE_PERF_EVENTS_NMI
        help
          The arch chooses to use the generic perf-NMI-based hardlockup
          detector. Must define HAVE_PERF_EVENTS_NMI.

config HAVE_NMI_WATCHDOG
        depends on HAVE_NMI
        bool
        help
          The arch provides a low level NMI watchdog. It provides
          asm/nmi.h, and defines its own arch_touch_nmi_watchdog().

config HAVE_HARDLOCKUP_DETECTOR_ARCH
        bool
        select HAVE_NMI_WATCHDOG
        help
          The arch chooses to provide its own hardlockup detector, which is
          a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
          interfaces and parameters provided by hardlockup detector subsystem.

config HAVE_PERF_REGS
        bool
        help
          Support selective register dumps for perf events. This includes
          bit-mapping of each registers and a unique architecture id.

config HAVE_PERF_USER_STACK_DUMP
        bool
        help
          Support user stack dumps for perf event samples. This needs
          access to the user stack pointer which is not unified across
          architectures.

config HAVE_ARCH_JUMP_LABEL
        bool

config HAVE_ARCH_JUMP_LABEL_RELATIVE
        bool

config HAVE_RCU_TABLE_FREE
        bool

config HAVE_RCU_TABLE_NO_INVALIDATE
        bool

config HAVE_MMU_GATHER_PAGE_SIZE
        bool

config HAVE_MMU_GATHER_NO_GATHER
        bool

config ARCH_HAVE_NMI_SAFE_CMPXCHG
        bool

config HAVE_ALIGNED_STRUCT_PAGE
        bool
        help
          This makes sure that struct pages are double word aligned and that
          e.g. the SLUB allocator can perform double word atomic operations
          on a struct page for better performance. However selecting this
          might increase the size of a struct page by a word.

config HAVE_CMPXCHG_LOCAL
        bool

config HAVE_CMPXCHG_DOUBLE
        bool

config ARCH_WEAK_RELEASE_ACQUIRE
        bool

config ARCH_WANT_IPC_PARSE_VERSION
        bool

config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
        bool

config ARCH_WANT_OLD_COMPAT_IPC
        select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
        bool

config HAVE_ARCH_SECCOMP_FILTER
        bool
        help
          An arch should select this symbol if it provides all of these things:
          - syscall_get_arch()
          - syscall_get_arguments()
          - syscall_rollback()
          - syscall_set_return_value()
          - SIGSYS siginfo_t support
          - secure_computing is called from a ptrace_event()-safe context
          - secure_computing return value is checked and a return value of -1
            results in the system call being skipped immediately.
          - seccomp syscall wired up

config SECCOMP_FILTER
        def_bool y
        depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
        help
          Enable tasks to build secure computing environments defined
          in terms of Berkeley Packet Filter programs which implement
          task-defined system call filtering polices.

          See Documentation/userspace-api/seccomp_filter.rst for details.

config HAVE_ARCH_STACKLEAK
        bool
        help
          An architecture should select this if it has the code which
          fills the used part of the kernel stack with the STACKLEAK_POISON
          value before returning from system calls.

config HAVE_STACKPROTECTOR
        bool
        help
          An arch should select this symbol if:
          - it has implemented a stack canary (e.g. __stack_chk_guard)

config CC_HAS_STACKPROTECTOR_NONE
        def_bool $(cc-option,-fno-stack-protector)

config STACKPROTECTOR
        bool "Stack Protector buffer overflow detection"
        depends on HAVE_STACKPROTECTOR
        depends on $(cc-option,-fstack-protector)
        default y
        help
          This option turns on the "stack-protector" GCC feature. This
          feature puts, at the beginning of functions, a canary value on
          the stack just before the return address, and validates
          the value just before actually returning.  Stack based buffer
          overflows (that need to overwrite this return address) now also
          overwrite the canary, which gets detected and the attack is then
          neutralized via a kernel panic.

          Functions will have the stack-protector canary logic added if they
          have an 8-byte or larger character array on the stack.

          This feature requires gcc version 4.2 or above, or a distribution
          gcc with the feature backported ("-fstack-protector").

          On an x86 "defconfig" build, this feature adds canary checks to
          about 3% of all kernel functions, which increases kernel code size
          by about 0.3%.

config STACKPROTECTOR_STRONG
        bool "Strong Stack Protector"
        depends on STACKPROTECTOR
        depends on $(cc-option,-fstack-protector-strong)
        default y
        help
          Functions will have the stack-protector canary logic added in any
          of the following conditions:

          - local variable's address used as part of the right hand side of an
            assignment or function argument
          - local variable is an array (or union containing an array),
            regardless of array type or length
          - uses register local variables

          This feature requires gcc version 4.9 or above, or a distribution
          gcc with the feature backported ("-fstack-protector-strong").

          On an x86 "defconfig" build, this feature adds canary checks to
          about 20% of all kernel functions, which increases the kernel code
          size by about 2%.

config HAVE_ARCH_WITHIN_STACK_FRAMES
        bool
        help
          An architecture should select this if it can walk the kernel stack
          frames to determine if an object is part of either the arguments
          or local variables (i.e. that it excludes saved return addresses,
          and similar) by implementing an inline arch_within_stack_frames(),
          which is used by CONFIG_HARDENED_USERCOPY.

config HAVE_CONTEXT_TRACKING
        bool
        help
          Provide kernel/user boundaries probes necessary for subsystems
          that need it, such as userspace RCU extended quiescent state.
          Syscalls need to be wrapped inside user_exit()-user_enter() through
          the slow path using TIF_NOHZ flag. Exceptions handlers must be
          wrapped as well. Irqs are already protected inside
          rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
          irq exit still need to be protected.

config HAVE_VIRT_CPU_ACCOUNTING
        bool

config ARCH_HAS_SCALED_CPUTIME
        bool

config HAVE_VIRT_CPU_ACCOUNTING_GEN
        bool
        default y if 64BIT
        help
          With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
          Before enabling this option, arch code must be audited
          to ensure there are no races in concurrent read/write of
          cputime_t. For example, reading/writing 64-bit cputime_t on
          some 32-bit arches may require multiple accesses, so proper
          locking is needed to protect against concurrent accesses.


config HAVE_IRQ_TIME_ACCOUNTING
        bool
        help
          Archs need to ensure they use a high enough resolution clock to
          support irq time accounting and then call enable_sched_clock_irqtime().

config HAVE_MOVE_PMD
        bool
        help
          Archs that select this are able to move page tables at the PMD level.

config HAVE_ARCH_TRANSPARENT_HUGEPAGE
        bool

config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
        bool

config HAVE_ARCH_HUGE_VMAP
        bool

config HAVE_ARCH_SOFT_DIRTY
        bool

config HAVE_MOD_ARCH_SPECIFIC
        bool
        help
          The arch uses struct mod_arch_specific to store data.  Many arches
          just need a simple module loader without arch specific data - those
          should not enable this.

config MODULES_USE_ELF_RELA
        bool
        help
          Modules only use ELF RELA relocations.  Modules with ELF REL
          relocations will give an error.

config MODULES_USE_ELF_REL
        bool
        help
          Modules only use ELF REL relocations.  Modules with ELF RELA
          relocations will give an error.

config HAVE_IRQ_EXIT_ON_IRQ_STACK
        bool
        help
          Architecture doesn't only execute the irq handler on the irq stack
          but also irq_exit(). This way we can process softirqs on this irq
          stack instead of switching to a new one when we call __do_softirq()
          in the end of an hardirq.
          This spares a stack switch and improves cache usage on softirq
          processing.

config PGTABLE_LEVELS
        int
        default 2

config ARCH_HAS_ELF_RANDOMIZE
        bool
        help
          An architecture supports choosing randomized locations for
          stack, mmap, brk, and ET_DYN. Defined functions:
          - arch_mmap_rnd()
          - arch_randomize_brk()

config HAVE_ARCH_MMAP_RND_BITS
        bool
        help
          An arch should select this symbol if it supports setting a variable
          number of bits for use in establishing the base address for mmap
          allocations, has MMU enabled and provides values for both:
          - ARCH_MMAP_RND_BITS_MIN
          - ARCH_MMAP_RND_BITS_MAX

config HAVE_EXIT_THREAD
        bool
        help
          An architecture implements exit_thread.

config ARCH_MMAP_RND_BITS_MIN
        int

config ARCH_MMAP_RND_BITS_MAX
        int

config ARCH_MMAP_RND_BITS_DEFAULT
        int

config ARCH_MMAP_RND_BITS
        int "Number of bits to use for ASLR of mmap base address" if EXPERT
        range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
        default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
        default ARCH_MMAP_RND_BITS_MIN
        depends on HAVE_ARCH_MMAP_RND_BITS
        help
          This value can be used to select the number of bits to use to
          determine the random offset to the base address of vma regions
          resulting from mmap allocations. This value will be bounded
          by the architecture's minimum and maximum supported values.

          This value can be changed after boot using the
          /proc/sys/vm/mmap_rnd_bits tunable

config HAVE_ARCH_MMAP_RND_COMPAT_BITS
        bool
        help
          An arch should select this symbol if it supports running applications
          in compatibility mode, supports setting a variable number of bits for
          use in establishing the base address for mmap allocations, has MMU
          enabled and provides values for both:
          - ARCH_MMAP_RND_COMPAT_BITS_MIN
          - ARCH_MMAP_RND_COMPAT_BITS_MAX

config ARCH_MMAP_RND_COMPAT_BITS_MIN
        int

config ARCH_MMAP_RND_COMPAT_BITS_MAX
        int

config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
        int

config ARCH_MMAP_RND_COMPAT_BITS
        int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
        range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
        default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
        default ARCH_MMAP_RND_COMPAT_BITS_MIN
        depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
        help
          This value can be used to select the number of bits to use to
          determine the random offset to the base address of vma regions
          resulting from mmap allocations for compatible applications This
          value will be bounded by the architecture's minimum and maximum
          supported values.

          This value can be changed after boot using the
          /proc/sys/vm/mmap_rnd_compat_bits tunable

config HAVE_ARCH_COMPAT_MMAP_BASES
        bool
        help
          This allows 64bit applications to invoke 32-bit mmap() syscall
          and vice-versa 32-bit applications to call 64-bit mmap().
          Required for applications doing different bitness syscalls.

config HAVE_COPY_THREAD_TLS
        bool
        help
          Architecture provides copy_thread_tls to accept tls argument via
          normal C parameter passing, rather than extracting the syscall
          argument from pt_regs.

config HAVE_STACK_VALIDATION
        bool
        help
          Architecture supports the 'objtool check' host tool command, which
          performs compile-time stack metadata validation.

config HAVE_RELIABLE_STACKTRACE
        bool
        help
          Architecture has a save_stack_trace_tsk_reliable() function which
          only returns a stack trace if it can guarantee the trace is reliable.

config HAVE_ARCH_HASH
        bool
        default n
        help
          If this is set, the architecture provides an <asm/hash.h>
          file which provides platform-specific implementations of some
          functions in <linux/hash.h> or fs/namei.c.

config HAVE_ARCH_NVRAM_OPS
        bool

config ISA_BUS_API
        def_bool ISA

#
# ABI hall of shame
#
config CLONE_BACKWARDS
        bool
        help
          Architecture has tls passed as the 4th argument of clone(2),
          not the 5th one.

config CLONE_BACKWARDS2
        bool
        help
          Architecture has the first two arguments of clone(2) swapped.

config CLONE_BACKWARDS3
        bool
        help
          Architecture has tls passed as the 3rd argument of clone(2),
          not the 5th one.

config ODD_RT_SIGACTION
        bool
        help
          Architecture has unusual rt_sigaction(2) arguments

config OLD_SIGSUSPEND
        bool
        help
          Architecture has old sigsuspend(2) syscall, of one-argument variety

config OLD_SIGSUSPEND3
        bool
        help
          Even weirder antique ABI - three-argument sigsuspend(2)

config OLD_SIGACTION
        bool
        help
          Architecture has old sigaction(2) syscall.  Nope, not the same
          as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
          but fairly different variant of sigaction(2), thanks to OSF/1
          compatibility...

config COMPAT_OLD_SIGACTION
        bool

config 64BIT_TIME
        def_bool y
        help
          This should be selected by all architectures that need to support
          new system calls with a 64-bit time_t. This is relevant on all 32-bit
          architectures, and 64-bit architectures as part of compat syscall
          handling.

config COMPAT_32BIT_TIME
        def_bool !64BIT || COMPAT
        help
          This enables 32 bit time_t support in addition to 64 bit time_t support.
          This is relevant on all 32-bit architectures, and 64-bit architectures
          as part of compat syscall handling.

config ARCH_NO_COHERENT_DMA_MMAP
        bool

config ARCH_NO_PREEMPT
        bool

config CPU_NO_EFFICIENT_FFS
        def_bool n

config HAVE_ARCH_VMAP_STACK
        def_bool n
        help
          An arch should select this symbol if it can support kernel stacks
          in vmalloc space.  This means:

          - vmalloc space must be large enough to hold many kernel stacks.
            This may rule out many 32-bit architectures.

          - Stacks in vmalloc space need to work reliably.  For example, if
            vmap page tables are created on demand, either this mechanism
            needs to work while the stack points to a virtual address with
            unpopulated page tables or arch code (switch_to() and switch_mm(),
            most likely) needs to ensure that the stack's page table entries
            are populated before running on a possibly unpopulated stack.

          - If the stack overflows into a guard page, something reasonable
            should happen.  The definition of "reasonable" is flexible, but
            instantly rebooting without logging anything would be unfriendly.

config VMAP_STACK
        default y
        bool "Use a virtually-mapped stack"
        depends on HAVE_ARCH_VMAP_STACK && !KASAN
        ---help---
          Enable this if you want the use virtually-mapped kernel stacks
          with guard pages.  This causes kernel stack overflows to be
          caught immediately rather than causing difficult-to-diagnose
          corruption.

          This is presently incompatible with KASAN because KASAN expects
          the stack to map directly to the KASAN shadow map using a formula
          that is incorrect if the stack is in vmalloc space.

config ARCH_OPTIONAL_KERNEL_RWX
        def_bool n

config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
        def_bool n

config ARCH_HAS_STRICT_KERNEL_RWX
        def_bool n

config STRICT_KERNEL_RWX
        bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
        depends on ARCH_HAS_STRICT_KERNEL_RWX
        default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
        help
          If this is set, kernel text and rodata memory will be made read-only,
          and non-text memory will be made non-executable. This provides
          protection against certain security exploits (e.g. executing the heap
          or modifying text)

          These features are considered standard security practice these days.
          You should say Y here in almost all cases.

config ARCH_HAS_STRICT_MODULE_RWX
        def_bool n

config STRICT_MODULE_RWX
        bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
        depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
        default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
        help
          If this is set, module text and rodata memory will be made read-only,
          and non-text memory will be made non-executable. This provides
          protection against certain security exploits (e.g. writing to text)

# select if the architecture provides an asm/dma-direct.h header
config ARCH_HAS_PHYS_TO_DMA
        bool

config ARCH_HAS_REFCOUNT
        bool
        help
          An architecture selects this when it has implemented refcount_t
          using open coded assembly primitives that provide an optimized
          refcount_t implementation, possibly at the expense of some full
          refcount state checks of CONFIG_REFCOUNT_FULL=y.

          The refcount overflow check behavior, however, must be retained.
          Catching overflows is the primary security concern for protecting
          against bugs in reference counts.

config REFCOUNT_FULL
        bool "Perform full reference count validation at the expense of speed"
        help
          Enabling this switches the refcounting infrastructure from a fast
          unchecked atomic_t implementation to a fully state checked
          implementation, which can be (slightly) slower but provides protections
          against various use-after-free conditions that can be used in
          security flaw exploits.

config HAVE_ARCH_COMPILER_H
        bool
        help
          An architecture can select this if it provides an
          asm/compiler.h header that should be included after
          linux/compiler-*.h in order to override macro definitions that those
          headers generally provide.

config HAVE_ARCH_PREL32_RELOCATIONS
        bool
        help
          May be selected by an architecture if it supports place-relative
          32-bit relocations, both in the toolchain and in the module loader,
          in which case relative references can be used in special sections
          for PCI fixup, initcalls etc which are only half the size on 64 bit
          architectures, and don't require runtime relocation on relocatable
          kernels.

config ARCH_USE_MEMREMAP_PROT
        bool

config LOCK_EVENT_COUNTS
        bool "Locking event counts collection"
        depends on DEBUG_FS
        ---help---
          Enable light-weight counting of various locking related events
          in the system with minimal performance impact. This reduces
          the chance of application behavior change because of timing
          differences. The counts are reported via debugfs.

source "kernel/gcov/Kconfig"

source "scripts/gcc-plugins/Kconfig"

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