|  | # 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 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 | 
|  |  | 
|  | # 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_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 | 
|  |  | 
|  | # 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 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_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_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 | 
|  | # 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_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 | 
|  |  | 
|  | # 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 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 !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_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_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_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. | 
|  |  | 
|  | 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 | 
|  |  | 
|  | endmenu |