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- # 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 KEXEC_ELF
- bool
- config HAVE_IMA_KEXEC
- bool
- config ARCH_HAS_SUBPAGE_FAULTS
- bool
- help
- Select if the architecture can check permissions at sub-page
- granularity (e.g. arm64 MTE). The probe_user_*() functions
- must be implemented.
- config HOTPLUG_SMT
- bool
- config GENERIC_ENTRY
- bool
- config KPROBES
- bool "Kprobes"
- depends on MODULES
- depends on HAVE_KPROBES
- select KALLSYMS
- select TASKS_RCU if PREEMPTION
- 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
- select OBJTOOL if HAVE_JUMP_LABEL_HACK
- 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 STATIC_CALL_SELFTEST
- bool "Static call selftest"
- depends on HAVE_STATIC_CALL
- help
- Boot time self-test of the call patching code.
- config OPTPROBES
- def_bool y
- depends on KPROBES && HAVE_OPTPROBES
- select TASKS_RCU if PREEMPTION
- 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/core-api/unaligned-memory-access.rst 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/core-api/unaligned-memory-access.rst 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 || HAVE_RETHOOK)
- config KRETPROBE_ON_RETHOOK
- def_bool y
- depends on HAVE_RETHOOK
- depends on KRETPROBES
- select RETHOOK
- 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 ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
- bool
- help
- Since kretprobes modifies return address on the stack, the
- stacktrace may see the kretprobe trampoline address instead
- of correct one. If the architecture stacktrace code and
- unwinder can adjust such entries, select this configuration.
- config HAVE_FUNCTION_ERROR_INJECTION
- bool
- config HAVE_NMI
- bool
- config HAVE_FUNCTION_DESCRIPTORS
- bool
- config TRACE_IRQFLAGS_SUPPORT
- bool
- config TRACE_IRQFLAGS_NMI_SUPPORT
- 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 ptrace_report_syscall_{entry,exit}
- # TIF_NOTIFY_RESUME calls resume_user_mode_work()
- #
- 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 the architecture provides the arch_dma_set_uncached symbol to
- # either provide an uncached segment alias for a DMA allocation, or
- # to remap the page tables in place.
- #
- config ARCH_HAS_DMA_SET_UNCACHED
- bool
- #
- # Select if the architectures provides the arch_dma_clear_uncached symbol
- # to undo an in-place page table remap for uncached access.
- #
- config ARCH_HAS_DMA_CLEAR_UNCACHED
- bool
- config ARCH_HAS_CPU_FINALIZE_INIT
- 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_WANTS_NO_INSTR
- bool
- help
- An architecture should select this if the noinstr macro is being used on
- functions to denote that the toolchain should avoid instrumenting such
- functions and is required for correctness.
- 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.
- # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
- config ARCH_32BIT_USTAT_F_TINODE
- bool
- config HAVE_ASM_MODVERSIONS
- bool
- help
- This symbol should be selected by an architecture if it provides
- <asm/asm-prototypes.h> to support the module versioning for symbols
- exported from assembly code.
- config HAVE_REGS_AND_STACK_ACCESS_API
- bool
- help
- This symbol should be selected by an architecture 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_RUST
- bool
- help
- This symbol should be selected by an architecture if it
- supports Rust.
- config HAVE_FUNCTION_ARG_ACCESS_API
- bool
- help
- This symbol should be selected by an architecture if it supports
- the API needed to access function arguments from pt_regs,
- declared in asm/ptrace.h
- 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 MMU_GATHER_TABLE_FREE
- bool
- config MMU_GATHER_RCU_TABLE_FREE
- bool
- select MMU_GATHER_TABLE_FREE
- config MMU_GATHER_PAGE_SIZE
- bool
- config MMU_GATHER_NO_RANGE
- bool
- select MMU_GATHER_MERGE_VMAS
- config MMU_GATHER_NO_FLUSH_CACHE
- bool
- config MMU_GATHER_MERGE_VMAS
- bool
- config MMU_GATHER_NO_GATHER
- bool
- depends on MMU_GATHER_TABLE_FREE
- config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
- bool
- help
- Temporary select until all architectures can be converted to have
- irqs disabled over activate_mm. Architectures that do IPI based TLB
- shootdowns should enable this.
- 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
- bool
- help
- An arch should select this symbol to support seccomp mode 1 (the fixed
- syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
- and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
- - __NR_seccomp_read_32
- - __NR_seccomp_write_32
- - __NR_seccomp_exit_32
- - __NR_seccomp_sigreturn_32
- config HAVE_ARCH_SECCOMP_FILTER
- bool
- select HAVE_ARCH_SECCOMP
- help
- An arch should select this symbol if it provides all of these things:
- - all the requirements for HAVE_ARCH_SECCOMP
- - 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
- - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
- SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
- COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
- config SECCOMP
- prompt "Enable seccomp to safely execute untrusted bytecode"
- def_bool y
- depends on HAVE_ARCH_SECCOMP
- help
- This kernel feature is useful for number crunching applications
- that may need to handle untrusted bytecode during their
- execution. By using pipes or other transports made available
- to the process as file descriptors supporting the read/write
- syscalls, it's possible to isolate those applications in their
- own address space using seccomp. Once seccomp is enabled via
- prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
- disabled and the task is only allowed to execute a few safe
- syscalls defined by each seccomp mode.
- If unsure, say Y.
- 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 SECCOMP_CACHE_DEBUG
- bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
- depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
- depends on PROC_FS
- help
- This enables the /proc/pid/seccomp_cache interface to monitor
- seccomp cache data. The file format is subject to change. Reading
- the file requires CAP_SYS_ADMIN.
- This option is for debugging only. Enabling presents the risk that
- an adversary may be able to infer the seccomp filter logic.
- If unsure, say N.
- 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 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 ARCH_SUPPORTS_SHADOW_CALL_STACK
- bool
- help
- An architecture should select this if it supports the compiler's
- Shadow Call Stack and implements runtime support for shadow stack
- switching.
- config SHADOW_CALL_STACK
- bool "Shadow Call Stack"
- depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
- depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
- help
- This option enables the compiler's Shadow Call Stack, which
- uses a shadow stack to protect function return addresses from
- being overwritten by an attacker. More information can be found
- in the compiler's documentation:
- - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
- - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
- Note that security guarantees in the kernel differ from the
- ones documented for user space. The kernel must store addresses
- of shadow stacks in memory, which means an attacker capable of
- reading and writing arbitrary memory may be able to locate them
- and hijack control flow by modifying the stacks.
- config DYNAMIC_SCS
- bool
- help
- Set by the arch code if it relies on code patching to insert the
- shadow call stack push and pop instructions rather than on the
- compiler.
- config LTO
- bool
- help
- Selected if the kernel will be built using the compiler's LTO feature.
- config LTO_CLANG
- bool
- select LTO
- help
- Selected if the kernel will be built using Clang's LTO feature.
- config ARCH_SUPPORTS_LTO_CLANG
- bool
- help
- An architecture should select this option if it supports:
- - compiling with Clang,
- - compiling inline assembly with Clang's integrated assembler,
- - and linking with LLD.
- config ARCH_SUPPORTS_LTO_CLANG_THIN
- bool
- help
- An architecture should select this option if it can support Clang's
- ThinLTO mode.
- config HAS_LTO_CLANG
- def_bool y
- depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
- depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
- depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
- depends on ARCH_SUPPORTS_LTO_CLANG
- depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
- depends on !KASAN || KASAN_HW_TAGS
- depends on !GCOV_KERNEL
- help
- The compiler and Kconfig options support building with Clang's
- LTO.
- choice
- prompt "Link Time Optimization (LTO)"
- default LTO_NONE
- help
- This option enables Link Time Optimization (LTO), which allows the
- compiler to optimize binaries globally.
- If unsure, select LTO_NONE. Note that LTO is very resource-intensive
- so it's disabled by default.
- config LTO_NONE
- bool "None"
- help
- Build the kernel normally, without Link Time Optimization (LTO).
- config LTO_CLANG_FULL
- bool "Clang Full LTO (EXPERIMENTAL)"
- depends on HAS_LTO_CLANG
- depends on !COMPILE_TEST
- select LTO_CLANG
- help
- This option enables Clang's full Link Time Optimization (LTO), which
- allows the compiler to optimize the kernel globally. If you enable
- this option, the compiler generates LLVM bitcode instead of ELF
- object files, and the actual compilation from bitcode happens at
- the LTO link step, which may take several minutes depending on the
- kernel configuration. More information can be found from LLVM's
- documentation:
- https://llvm.org/docs/LinkTimeOptimization.html
- During link time, this option can use a large amount of RAM, and
- may take much longer than the ThinLTO option.
- config LTO_CLANG_THIN
- bool "Clang ThinLTO (EXPERIMENTAL)"
- depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
- select LTO_CLANG
- help
- This option enables Clang's ThinLTO, which allows for parallel
- optimization and faster incremental compiles compared to the
- CONFIG_LTO_CLANG_FULL option. More information can be found
- from Clang's documentation:
- https://clang.llvm.org/docs/ThinLTO.html
- If unsure, say Y.
- endchoice
- config ARCH_SUPPORTS_CFI_CLANG
- bool
- help
- An architecture should select this option if it can support Clang's
- Control-Flow Integrity (CFI) checking.
- config ARCH_USES_CFI_TRAPS
- bool
- config CFI_CLANG
- bool "Use Clang's Control Flow Integrity (CFI)"
- depends on ARCH_SUPPORTS_CFI_CLANG
- depends on $(cc-option,-fsanitize=kcfi)
- help
- This option enables Clang’s forward-edge Control Flow Integrity
- (CFI) checking, where the compiler injects a runtime check to each
- indirect function call to ensure the target is a valid function with
- the correct static type. This restricts possible call targets and
- makes it more difficult for an attacker to exploit bugs that allow
- the modification of stored function pointers. More information can be
- found from Clang's documentation:
- https://clang.llvm.org/docs/ControlFlowIntegrity.html
- config CFI_PERMISSIVE
- bool "Use CFI in permissive mode"
- depends on CFI_CLANG
- help
- When selected, Control Flow Integrity (CFI) violations result in a
- warning instead of a kernel panic. This option should only be used
- for finding indirect call type mismatches during development.
- If unsure, say N.
- 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_USER
- 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(), either
- optimized behind static key or through the slow path using TIF_NOHZ
- flag. Exceptions handlers must be wrapped as well. Irqs are already
- protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
- handling on irq exit still need to be protected.
- config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
- bool
- help
- Architecture neither relies on exception_enter()/exception_exit()
- nor on schedule_user(). Also preempt_schedule_notrace() and
- preempt_schedule_irq() can't be called in a preemptible section
- while context tracking is CONTEXT_USER. This feature reflects a sane
- entry implementation where the following requirements are met on
- critical entry code, ie: before user_exit() or after user_enter():
- - Critical entry code isn't preemptible (or better yet:
- not interruptible).
- - No use of RCU read side critical sections, unless ct_nmi_enter()
- got called.
- - No use of instrumentation, unless instrumentation_begin() got
- called.
- config HAVE_TIF_NOHZ
- bool
- help
- Arch relies on TIF_NOHZ and syscall slow path to implement context
- tracking calls to user_enter()/user_exit().
- config HAVE_VIRT_CPU_ACCOUNTING
- bool
- config HAVE_VIRT_CPU_ACCOUNTING_IDLE
- bool
- help
- Architecture has its own way to account idle CPU time and therefore
- doesn't implement vtime_account_idle().
- 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_PUD
- bool
- help
- Architectures that select this are able to move page tables at the
- PUD level. If there are only 3 page table levels, the move effectively
- happens at the PGD level.
- 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
- #
- # Archs that select this would be capable of PMD-sized vmaps (i.e.,
- # arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
- # must be used to enable allocations to use hugepages.
- #
- config HAVE_ARCH_HUGE_VMALLOC
- depends on HAVE_ARCH_HUGE_VMAP
- bool
- config ARCH_WANT_HUGE_PMD_SHARE
- 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 ARCH_WANTS_MODULES_DATA_IN_VMALLOC
- bool
- help
- For architectures like powerpc/32 which have constraints on module
- allocation and need to allocate module data outside of module area.
- 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 HAVE_SOFTIRQ_ON_OWN_STACK
- bool
- help
- Architecture provides a function to run __do_softirq() on a
- separate stack.
- config SOFTIRQ_ON_OWN_STACK
- def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
- config ALTERNATE_USER_ADDRESS_SPACE
- bool
- help
- Architectures set this when the CPU uses separate address
- spaces for kernel and user space pointers. In this case, the
- access_ok() check on a __user pointer is skipped.
- 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 PAGE_SIZE_LESS_THAN_64KB
- def_bool y
- depends on !ARM64_64K_PAGES
- depends on !IA64_PAGE_SIZE_64KB
- depends on !PAGE_SIZE_64KB
- depends on !PARISC_PAGE_SIZE_64KB
- depends on PAGE_SIZE_LESS_THAN_256KB
- config PAGE_SIZE_LESS_THAN_256KB
- def_bool y
- depends on !PAGE_SIZE_256KB
- # This allows to use a set of generic functions to determine mmap base
- # address by giving priority to top-down scheme only if the process
- # is not in legacy mode (compat task, unlimited stack size or
- # sysctl_legacy_va_layout).
- # Architecture that selects this option can provide its own version of:
- # - STACK_RND_MASK
- config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
- bool
- depends on MMU
- select ARCH_HAS_ELF_RANDOMIZE
- config HAVE_OBJTOOL
- bool
- config HAVE_JUMP_LABEL_HACK
- bool
- config HAVE_NOINSTR_HACK
- bool
- config HAVE_NOINSTR_VALIDATION
- bool
- config HAVE_UACCESS_VALIDATION
- bool
- select OBJTOOL
- config HAVE_STACK_VALIDATION
- bool
- help
- Architecture supports objtool compile-time frame pointer rule
- validation.
- config HAVE_RELIABLE_STACKTRACE
- bool
- help
- Architecture has either save_stack_trace_tsk_reliable() or
- arch_stack_walk_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 COMPAT_32BIT_TIME
- bool "Provide system calls for 32-bit time_t"
- default !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_PREEMPT
- bool
- config ARCH_EPHEMERAL_INODES
- def_bool n
- help
- An arch should select this symbol if it doesn't keep track of inode
- instances on its own, but instead relies on something else (e.g. the
- host kernel for an UML kernel).
- config ARCH_SUPPORTS_RT
- 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
- depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
- 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.
- To use this with software KASAN modes, the architecture must support
- backing virtual mappings with real shadow memory, and KASAN_VMALLOC
- must be enabled.
- config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
- def_bool n
- help
- An arch should select this symbol if it can support kernel stack
- offset randomization with calls to add_random_kstack_offset()
- during syscall entry and choose_random_kstack_offset() during
- syscall exit. Careful removal of -fstack-protector-strong and
- -fstack-protector should also be applied to the entry code and
- closely examined, as the artificial stack bump looks like an array
- to the compiler, so it will attempt to add canary checks regardless
- of the static branch state.
- config RANDOMIZE_KSTACK_OFFSET
- bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
- default y
- depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
- depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
- help
- The kernel stack offset can be randomized (after pt_regs) by
- roughly 5 bits of entropy, frustrating memory corruption
- attacks that depend on stack address determinism or
- cross-syscall address exposures.
- The feature is controlled via the "randomize_kstack_offset=on/off"
- kernel boot param, and if turned off has zero overhead due to its use
- of static branches (see JUMP_LABEL).
- If unsure, say Y.
- config RANDOMIZE_KSTACK_OFFSET_DEFAULT
- bool "Default state of kernel stack offset randomization"
- depends on RANDOMIZE_KSTACK_OFFSET
- help
- Kernel stack offset randomization is controlled by kernel boot param
- "randomize_kstack_offset=on/off", and this config chooses the default
- boot state.
- 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 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.
- # Select if the architecture has support for applying RELR relocations.
- config ARCH_HAS_RELR
- bool
- config RELR
- bool "Use RELR relocation packing"
- depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
- default y
- help
- Store the kernel's dynamic relocations in the RELR relocation packing
- format. Requires a compatible linker (LLD supports this feature), as
- well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
- are compatible).
- config ARCH_HAS_MEM_ENCRYPT
- bool
- config ARCH_HAS_MEM_RELINQUISH
- bool
- config ARCH_HAS_CC_PLATFORM
- bool
- config HAVE_SPARSE_SYSCALL_NR
- bool
- help
- An architecture should select this if its syscall numbering is sparse
- to save space. For example, MIPS architecture has a syscall array with
- entries at 4000, 5000 and 6000 locations. This option turns on syscall
- related optimizations for a given architecture.
- config ARCH_HAS_VDSO_DATA
- bool
- config HAVE_STATIC_CALL
- bool
- config HAVE_STATIC_CALL_INLINE
- bool
- depends on HAVE_STATIC_CALL
- select OBJTOOL
- config HAVE_PREEMPT_DYNAMIC
- bool
- config HAVE_PREEMPT_DYNAMIC_CALL
- bool
- depends on HAVE_STATIC_CALL
- select HAVE_PREEMPT_DYNAMIC
- help
- An architecture should select this if it can handle the preemption
- model being selected at boot time using static calls.
- Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
- preemption function will be patched directly.
- Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
- call to a preemption function will go through a trampoline, and the
- trampoline will be patched.
- It is strongly advised to support inline static call to avoid any
- overhead.
- config HAVE_PREEMPT_DYNAMIC_KEY
- bool
- depends on HAVE_ARCH_JUMP_LABEL
- select HAVE_PREEMPT_DYNAMIC
- help
- An architecture should select this if it can handle the preemption
- model being selected at boot time using static keys.
- Each preemption function will be given an early return based on a
- static key. This should have slightly lower overhead than non-inline
- static calls, as this effectively inlines each trampoline into the
- start of its callee. This may avoid redundant work, and may
- integrate better with CFI schemes.
- This will have greater overhead than using inline static calls as
- the call to the preemption function cannot be entirely elided.
- config ARCH_WANT_LD_ORPHAN_WARN
- bool
- help
- An arch should select this symbol once all linker sections are explicitly
- included, size-asserted, or discarded in the linker scripts. This is
- important because we never want expected sections to be placed heuristically
- by the linker, since the locations of such sections can change between linker
- versions.
- config HAVE_ARCH_PFN_VALID
- bool
- config ARCH_SUPPORTS_DEBUG_PAGEALLOC
- bool
- config ARCH_SUPPORTS_PAGE_TABLE_CHECK
- bool
- config ARCH_SPLIT_ARG64
- bool
- help
- If a 32-bit architecture requires 64-bit arguments to be split into
- pairs of 32-bit arguments, select this option.
- config ARCH_HAS_ELFCORE_COMPAT
- bool
- config ARCH_HAS_PARANOID_L1D_FLUSH
- bool
- config ARCH_HAVE_TRACE_MMIO_ACCESS
- bool
- config DYNAMIC_SIGFRAME
- bool
- # Select, if arch has a named attribute group bound to NUMA device nodes.
- config HAVE_ARCH_NODE_DEV_GROUP
- bool
- config ARCH_HAS_NONLEAF_PMD_YOUNG
- bool
- help
- Architectures that select this option are capable of setting the
- accessed bit in non-leaf PMD entries when using them as part of linear
- address translations. Page table walkers that clear the accessed bit
- may use this capability to reduce their search space.
- source "kernel/gcov/Kconfig"
- source "scripts/gcc-plugins/Kconfig"
- endmenu
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