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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" config ARCH_CONFIGURES_CPU_MITIGATIONS bool if !ARCH_CONFIGURES_CPU_MITIGATIONS config CPU_MITIGATIONS def_bool y endif # # Selected by architectures that need custom DMA operations for e.g. legacy # IOMMUs not handled by dma-iommu. Drivers must never select this symbol. # config ARCH_HAS_DMA_OPS depends on HAS_DMA select DMA_OPS_HELPERS bool menu "General architecture-dependent options" 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 SMT_NUM_THREADS_DYNAMIC bool config ARCH_SUPPORTS_SCHED_SMT bool config ARCH_SUPPORTS_SCHED_CLUSTER bool config ARCH_SUPPORTS_SCHED_MC bool config SCHED_SMT bool "SMT (Hyperthreading) scheduler support" depends on ARCH_SUPPORTS_SCHED_SMT default y help Improves the CPU scheduler's decision making when dealing with MultiThreading at a cost of slightly increased overhead in some places. If unsure say N here. config SCHED_CLUSTER bool "Cluster scheduler support" depends on ARCH_SUPPORTS_SCHED_CLUSTER default y help Cluster scheduler support improves the CPU scheduler's decision making when dealing with machines that have clusters of CPUs. Cluster usually means a couple of CPUs which are placed closely by sharing mid-level caches, last-level cache tags or internal busses. config SCHED_MC bool "Multi-Core Cache (MC) scheduler support" depends on ARCH_SUPPORTS_SCHED_MC default y help Multi-core scheduler support improves the CPU scheduler's decision making when dealing with multi-core CPU chips at a cost of slightly increased overhead in some places. If unsure say N here. # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL config HOTPLUG_CORE_SYNC bool # Basic CPU dead synchronization selected by architecture config HOTPLUG_CORE_SYNC_DEAD bool select HOTPLUG_CORE_SYNC # Full CPU synchronization with alive state selected by architecture config HOTPLUG_CORE_SYNC_FULL bool select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU select HOTPLUG_CORE_SYNC config HOTPLUG_SPLIT_STARTUP bool select HOTPLUG_CORE_SYNC_FULL config HOTPLUG_PARALLEL bool select HOTPLUG_SPLIT_STARTUP config GENERIC_IRQ_ENTRY bool config GENERIC_SYSCALL bool depends on GENERIC_IRQ_ENTRY config GENERIC_ENTRY bool select GENERIC_IRQ_ENTRY select GENERIC_SYSCALL config KPROBES bool "Kprobes" depends on HAVE_KPROBES select KALLSYMS select EXECMEM select NEED_TASKS_RCU 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 NEED_TASKS_RCU 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 select TASKS_TRACE_RCU 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 GCC and Clang have builtin functions for handling byte-swapping. Using these 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 # The architecture has a per-task state that includes the mm's PASID config ARCH_HAS_CPU_PASID bool select IOMMU_MM_DATA config HAVE_ARCH_THREAD_STRUCT_WHITELIST bool 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 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_HARDLOCKUP_DETECTOR_ARCH bool help The arch provides its own hardlockup detector implementation instead of the generic ones. It uses the same command line parameters, and sysctl interface, as the generic hardlockup detectors. config UNWIND_USER bool config HAVE_UNWIND_USER_FP bool select UNWIND_USER 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. # Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. # MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching # to/from kernel threads when the same mm is running on a lot of CPUs (a large # multi-threaded application), by reducing contention on the mm refcount. # # This can be disabled if the architecture ensures no CPUs are using an mm as a # "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm # or its kernel page tables). This could be arranged by arch_exit_mmap(), or # final exit(2) TLB flush, for example. # # To implement this, an arch *must*: # Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating # the lazy tlb reference of a kthread's ->active_mm (non-arch code has been # converted already). config MMU_LAZY_TLB_REFCOUNT def_bool y depends on !MMU_LAZY_TLB_SHOOTDOWN # This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an # mm as a lazy tlb beyond its last reference count, by shooting down these # users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may # be using the mm as a lazy tlb, so that they may switch themselves to using # init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs # may be using mm as a lazy tlb mm. # # To implement this, an arch *must*: # - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains # at least all possible CPUs in which the mm is lazy. # - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). config MMU_LAZY_TLB_SHOOTDOWN bool config ARCH_HAVE_NMI_SAFE_CMPXCHG bool config ARCH_HAVE_EXTRA_ELF_NOTES bool help An architecture should select this in order to enable adding an arch-specific ELF note section to core files. It must provide two functions: elf_coredump_extra_notes_size() and elf_coredump_extra_notes_write() which are invoked by the ELF core dumper. config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 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_KSTACK_ERASE bool help An architecture should select this if it has the code which fills the used part of the kernel stack with the KSTACK_ERASE_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 depends on MMU 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 # https://github.com/ClangBuiltLinux/linux/issues/1721 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 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_AUTOFDO_CLANG bool config AUTOFDO_CLANG bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" depends on ARCH_SUPPORTS_AUTOFDO_CLANG depends on CC_IS_CLANG && CLANG_VERSION >= 170000 help This option enables Clang’s AutoFDO build. When an AutoFDO profile is specified in variable CLANG_AUTOFDO_PROFILE during the build process, Clang uses the profile to optimize the kernel. If no profile is specified, AutoFDO options are still passed to Clang to facilitate the collection of perf data for creating an AutoFDO profile in subsequent builds. If unsure, say N. config ARCH_SUPPORTS_PROPELLER_CLANG bool config PROPELLER_CLANG bool "Enable Clang's Propeller build" depends on ARCH_SUPPORTS_PROPELLER_CLANG depends on CC_IS_CLANG && CLANG_VERSION >= 190000 help This option enables Clang’s Propeller build. When the Propeller profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX during the build process, Clang uses the profiles to optimize the kernel. If no profile is specified, Propeller options are still passed to Clang to facilitate the collection of perf data for creating the Propeller profiles in subsequent builds. If unsure, say N. config ARCH_SUPPORTS_CFI bool help An architecture should select this option if it can support Kernel Control-Flow Integrity (CFI) checking (-fsanitize=kcfi). config ARCH_USES_CFI_TRAPS bool help An architecture should select this option if it requires the .kcfi_traps section for KCFI trap handling. config ARCH_USES_CFI_GENERIC_LLVM_PASS bool help An architecture should select this option if it uses the generic KCFIPass in LLVM to expand kCFI bundles instead of architecture-specific lowering. config CFI bool "Use Kernel Control Flow Integrity (kCFI)" default CFI_CLANG depends on ARCH_SUPPORTS_CFI depends on $(cc-option,-fsanitize=kcfi) help This option enables 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_CLANG bool transitional help Transitional config for CFI_CLANG to CFI migration. config CFI_ICALL_NORMALIZE_INTEGERS bool "Normalize CFI tags for integers" depends on CFI depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS help This option normalizes the CFI tags for integer types so that all integer types of the same size and signedness receive the same CFI tag. The option is separate from CONFIG_RUST because it affects the ABI. When working with build systems that care about the ABI, it is convenient to be able to turn on this flag first, before Rust is turned on. This option is necessary for using CFI with Rust. If unsure, say N. config HAVE_CFI_ICALL_NORMALIZE_INTEGERS def_bool y depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC def_bool y depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS depends on RUSTC_VERSION >= 107900 depends on ARM64 || X86_64 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \ (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) config CFI_PERMISSIVE bool "Use CFI in permissive mode" depends on CFI 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 CT_STATE_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_PV_STEAL_CLOCK_GEN bool 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 # Archs that want to use pmd_mkwrite on kernel memory need it defined even # if there are no userspace memory management features that use it config ARCH_WANT_KERNEL_PMD_MKWRITE bool config ARCH_WANT_PMD_MKWRITE def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 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 ARCH_WANTS_MODULES_TEXT_SECTIONS bool help For architectures like 32-bit parisc which require that functions in modules have to keep code in own text sections (-ffunction-sections) and to avoid merging all text into one big text section, config ARCH_WANTS_EXECMEM_LATE bool help For architectures that do not allocate executable memory early on boot, but rather require its initialization late when there is enough entropy for module space randomization, for instance arm64. config ARCH_HAS_EXECMEM_ROX bool depends on MMU && !HIGHMEM help For architectures that support allocations of executable memory with read-only execute permissions. Architecture must implement execmem_fill_trapping_insns() callback to enable this. 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 HAVE_PAGE_SIZE_4KB bool config HAVE_PAGE_SIZE_8KB bool config HAVE_PAGE_SIZE_16KB bool config HAVE_PAGE_SIZE_32KB bool config HAVE_PAGE_SIZE_64KB bool config HAVE_PAGE_SIZE_256KB bool choice prompt "MMU page size" config PAGE_SIZE_4KB bool "4KiB pages" depends on HAVE_PAGE_SIZE_4KB help This option select the standard 4KiB Linux page size and the only available option on many architectures. Using 4KiB page size will minimize memory consumption and is therefore recommended for low memory systems. Some software that is written for x86 systems makes incorrect assumptions about the page size and only runs on 4KiB pages. config PAGE_SIZE_8KB bool "8KiB pages" depends on HAVE_PAGE_SIZE_8KB help This option is the only supported page size on a few older processors, and can be slightly faster than 4KiB pages. config PAGE_SIZE_16KB bool "16KiB pages" depends on HAVE_PAGE_SIZE_16KB help This option is usually a good compromise between memory consumption and performance for typical desktop and server workloads, often saving a level of page table lookups compared to 4KB pages as well as reducing TLB pressure and overhead of per-page operations in the kernel at the expense of a larger page cache. config PAGE_SIZE_32KB bool "32KiB pages" depends on HAVE_PAGE_SIZE_32KB help Using 32KiB page size will result in slightly higher performance kernel at the price of higher memory consumption compared to 16KiB pages. This option is available only on cnMIPS cores. Note that you will need a suitable Linux distribution to support this. config PAGE_SIZE_64KB bool "64KiB pages" depends on HAVE_PAGE_SIZE_64KB help Using 64KiB page size will result in slightly higher performance kernel at the price of much higher memory consumption compared to 4KiB or 16KiB pages. This is not suitable for general-purpose workloads but the better performance may be worth the cost for certain types of supercomputing or database applications that work mostly with large in-memory data rather than small files. config PAGE_SIZE_256KB bool "256KiB pages" depends on HAVE_PAGE_SIZE_256KB help 256KiB pages have little practical value due to their extreme memory usage. The kernel will only be able to run applications that have been compiled with '-zmax-page-size' set to 256KiB (the default is 64KiB or 4KiB on most architectures). endchoice config PAGE_SIZE_LESS_THAN_64KB def_bool y depends on !PAGE_SIZE_64KB depends on PAGE_SIZE_LESS_THAN_256KB config PAGE_SIZE_LESS_THAN_256KB def_bool y depends on !PAGE_SIZE_256KB config PAGE_SHIFT int default 12 if PAGE_SIZE_4KB default 13 if PAGE_SIZE_8KB default 14 if PAGE_SIZE_16KB default 15 if PAGE_SIZE_32KB default 16 if PAGE_SIZE_64KB default 18 if 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_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 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 ARCH_HAS_CPU_RESCTRL bool help An architecture selects this option to indicate that the necessary hooks are provided to support the common memory system usage monitoring and control interfaces provided by the 'resctrl' filesystem (see RESCTRL_FS). 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_LIBGCC_H bool help An architecture can select this if it provides an asm/libgcc.h header that should be included after linux/libgcc.h in order to override macro definitions that header generally provides. 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_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_ARCH_DATA depends on HAVE_GENERIC_VDSO bool config ARCH_HAS_VDSO_TIME_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_HW_PTE_YOUNG bool help Architectures that select this option are capable of setting the accessed bit in PTE entries when using them as part of linear address translations. Architectures that require runtime check should select this option and override arch_has_hw_pte_young(). 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. config ARCH_HAS_KERNEL_FPU_SUPPORT bool help Architectures that select this option can run floating-point code in the kernel, as described in Documentation/core-api/floating-point.rst. config ARCH_VMLINUX_NEEDS_RELOCS bool help Whether the architecture needs vmlinux to be built with static relocations preserved. This is used by some architectures to construct bespoke relocation tables for KASLR. # Select if architecture uses the common generic TIF bits config HAVE_GENERIC_TIF_BITS bool source "kernel/gcov/Kconfig" source "scripts/gcc-plugins/Kconfig" config FUNCTION_ALIGNMENT_4B bool config FUNCTION_ALIGNMENT_8B bool config FUNCTION_ALIGNMENT_16B bool config FUNCTION_ALIGNMENT_32B bool config FUNCTION_ALIGNMENT_64B bool config FUNCTION_ALIGNMENT int default 64 if FUNCTION_ALIGNMENT_64B default 32 if FUNCTION_ALIGNMENT_32B default 16 if FUNCTION_ALIGNMENT_16B default 8 if FUNCTION_ALIGNMENT_8B default 4 if FUNCTION_ALIGNMENT_4B default 0 config CC_HAS_MIN_FUNCTION_ALIGNMENT # Detect availability of the GCC option -fmin-function-alignment which # guarantees minimal alignment for all functions, unlike # -falign-functions which the compiler ignores for cold functions. def_bool $(cc-option, -fmin-function-alignment=8) config CC_HAS_SANE_FUNCTION_ALIGNMENT # Set if the guaranteed alignment with -fmin-function-alignment is # available or extra care is required in the kernel. Clang provides # strict alignment always, even with -falign-functions. def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG config ARCH_NEED_CMPXCHG_1_EMU bool config ARCH_WANTS_PRE_LINK_VMLINUX bool help An architecture can select this if it provides arch/<arch>/tools/Makefile with .arch.vmlinux.o target to be linked into vmlinux. config ARCH_HAS_CPU_ATTACK_VECTORS bool endmenu