linux-yocto/arch/Kconfig

SPDX-License-Identifier: GPL-2.0

General architecture dependent options

config CRASH_CORE bool

config KEXEC_CORE select CRASH_CORE bool

config HAVE_IMA_KEXEC bool

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

  If unsure, say N.

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

  If unsure, say N.

config HAVE_OPROFILE bool

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

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

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

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

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

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

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

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

config OPTPROBES def_bool y depends on KPROBES && HAVE_OPTPROBES depends on !PREEMPT

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

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

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

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

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

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

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

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

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

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

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

config KRETPROBES def_bool y depends on KPROBES && HAVE_KRETPROBES

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

config HAVE_IOREMAP_PROT bool

config HAVE_KPROBES bool

config HAVE_KRETPROBES bool

config HAVE_OPTPROBES bool

config HAVE_KPROBES_ON_FTRACE bool

config HAVE_NMI bool

An arch should select this if it provides all these things:

task_pt_regs() in asm/processor.h or asm/ptrace.h

arch_has_single_step() if there is hardware single-step support

arch_has_block_step() if there is hardware block-step support

asm/syscall.h supplying asm-generic/syscall.h interface

linux/regset.h user_regset interfaces

CORE_DUMP_USE_REGSET #define'd in linux/elf.h

TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}

TIF_NOTIFY_RESUME calls tracehook_notify_resume()

signal delivery calls tracehook_signal_handler()

config HAVE_ARCH_TRACEHOOK bool

config HAVE_DMA_CONTIGUOUS bool

config GENERIC_SMP_IDLE_THREAD bool

config GENERIC_IDLE_POLL_SETUP bool

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

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

config ARCH_HAS_SET_MEMORY bool

Select if arch init_task initializer is different to init/init_task.c

config ARCH_INIT_TASK bool

Select if arch has its private alloc_task_struct() function

config ARCH_TASK_STRUCT_ALLOCATOR bool

Select if arch has its private alloc_thread_stack() function

config ARCH_THREAD_STACK_ALLOCATOR bool

Select if arch wants to size task_struct dynamically via arch_task_struct_size:

config ARCH_WANTS_DYNAMIC_TASK_STRUCT bool

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

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

config HAVE_DMA_API_DEBUG bool

config HAVE_HW_BREAKPOINT bool depends on PERF_EVENTS

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

config HAVE_USER_RETURN_NOTIFIER bool

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

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

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

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

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

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

config HAVE_ARCH_JUMP_LABEL bool

config HAVE_RCU_TABLE_FREE bool

config ARCH_HAVE_NMI_SAFE_CMPXCHG bool

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

config HAVE_CMPXCHG_LOCAL bool

config HAVE_CMPXCHG_DOUBLE bool

config ARCH_WEAK_RELEASE_ACQUIRE bool

config ARCH_WANT_IPC_PARSE_VERSION bool

config ARCH_WANT_COMPAT_IPC_PARSE_VERSION bool

config ARCH_WANT_OLD_COMPAT_IPC select ARCH_WANT_COMPAT_IPC_PARSE_VERSION bool

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

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

  See Documentation/prctl/seccomp_filter.txt for details.

config HAVE_GCC_PLUGINS bool help An arch should select this symbol if it supports building with GCC plugins.

menuconfig GCC_PLUGINS bool "GCC plugins" depends on HAVE_GCC_PLUGINS depends on !COMPILE_TEST help GCC plugins are loadable modules that provide extra features to the compiler. They are useful for runtime instrumentation and static analysis.

  See Documentation/gcc-plugins.txt for details.

config GCC_PLUGIN_CYC_COMPLEXITY bool "Compute the cyclomatic complexity of a function" if EXPERT depends on GCC_PLUGINS depends on !COMPILE_TEST help The complexity M of a function's control flow graph is defined as: M = E - N + 2P where

  E = the number of edges
  N = the number of nodes
  P = the number of connected components (exit nodes).

  Enabling this plugin reports the complexity to stderr during the
  build. It mainly serves as a simple example of how to create a
  gcc plugin for the kernel.

config GCC_PLUGIN_SANCOV bool depends on GCC_PLUGINS help This plugin inserts a __sanitizer_cov_trace_pc() call at the start of basic blocks. It supports all gcc versions with plugin support (from gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" by Dmitry Vyukov dvyukov@google.com.

config GCC_PLUGIN_LATENT_ENTROPY bool "Generate some entropy during boot and runtime" depends on GCC_PLUGINS help By saying Y here the kernel will instrument some kernel code to extract some entropy from both original and artificially created program state. This will help especially embedded systems where there is little 'natural' source of entropy normally. The cost is some slowdown of the boot process (about 0.5%) and fork and irq processing.

  Note that entropy extracted this way is not cryptographically
  secure!

  This plugin was ported from grsecurity/PaX. More information at:
   * https://grsecurity.net/
   * https://pax.grsecurity.net/

config GCC_PLUGIN_STRUCTLEAK bool "Force initialization of variables containing userspace addresses" depends on GCC_PLUGINS help This plugin zero-initializes any structures containing a __user attribute. This can prevent some classes of information exposures.

  This plugin was ported from grsecurity/PaX. More information at:
   * https://grsecurity.net/
   * https://pax.grsecurity.net/

config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL bool "Force initialize all struct type variables passed by reference" depends on GCC_PLUGIN_STRUCTLEAK help Zero initialize any struct type local variable that may be passed by reference without having been initialized.

config GCC_PLUGIN_STRUCTLEAK_VERBOSE bool "Report forcefully initialized variables" depends on GCC_PLUGIN_STRUCTLEAK depends on !COMPILE_TEST help This option will cause a warning to be printed each time the structleak plugin finds a variable it thinks needs to be initialized. Since not all existing initializers are detected by the plugin, this can produce false positive warnings.

config GCC_PLUGIN_RANDSTRUCT bool "Randomize layout of sensitive kernel structures" depends on GCC_PLUGINS select MODVERSIONS if MODULES help If you say Y here, the layouts of structures that are entirely function pointers (and have not been manually annotated with __no_randomize_layout), or structures that have been explicitly marked with __randomize_layout, will be randomized at compile-time. This can introduce the requirement of an additional information exposure vulnerability for exploits targeting these structure types.

  Enabling this feature will introduce some performance impact,
  slightly increase memory usage, and prevent the use of forensic
  tools like Volatility against the system (unless the kernel
  source tree isn't cleaned after kernel installation).

  The seed used for compilation is located at
  scripts/gcc-plgins/randomize_layout_seed.h.  It remains after
  a make clean to allow for external modules to be compiled with
  the existing seed and will be removed by a make mrproper or
  make distclean.

  Note that the implementation requires gcc 4.7 or newer.

  This plugin was ported from grsecurity/PaX. More information at:
   * https://grsecurity.net/
   * https://pax.grsecurity.net/

config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE bool "Use cacheline-aware structure randomization" depends on GCC_PLUGIN_RANDSTRUCT depends on !COMPILE_TEST help If you say Y here, the RANDSTRUCT randomization will make a best effort at restricting randomization to cacheline-sized groups of elements. It will further not randomize bitfields in structures. This reduces the performance hit of RANDSTRUCT at the cost of weakened randomization.

config HAVE_CC_STACKPROTECTOR bool help An arch should select this symbol if: - its compiler supports the -fstack-protector option - it has implemented a stack canary (e.g. __stack_chk_guard)

config CC_STACKPROTECTOR def_bool n help Set when a stack-protector mode is enabled, so that the build can enable kernel-side support for the GCC feature.

choice prompt "Stack Protector buffer overflow detection" depends on HAVE_CC_STACKPROTECTOR default CC_STACKPROTECTOR_NONE 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.

config CC_STACKPROTECTOR_NONE bool "None" help Disable "stack-protector" GCC feature.

config CC_STACKPROTECTOR_REGULAR bool "Regular" select CC_STACKPROTECTOR help 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 CC_STACKPROTECTOR_STRONG bool "Strong" select CC_STACKPROTECTOR 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%.

endchoice

config THIN_ARCHIVES def_bool y help Select this if the architecture wants to use thin archives instead of ld -r to create the built-in.o files.

config LD_DEAD_CODE_DATA_ELIMINATION bool help Select this if the architecture wants to do dead code and data elimination with the linker by compiling with -ffunction-sections -fdata-sections and linking with --gc-sections.

  This requires that the arch annotates or otherwise protects
  its external entry points from being discarded. Linker scripts
  must also merge .text.*, .data.*, and .bss.* correctly into
  output sections. Care must be taken not to pull in unrelated
  sections (e.g., '.text.init'). Typically '.' in section names
  is used to distinguish them from label names / C identifiers.

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

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

config HAVE_VIRT_CPU_ACCOUNTING bool

config ARCH_HAS_SCALED_CPUTIME bool

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

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

config HAVE_ARCH_TRANSPARENT_HUGEPAGE bool

config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD bool

config HAVE_ARCH_HUGE_VMAP bool

config HAVE_ARCH_SOFT_DIRTY bool

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

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

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

config HAVE_UNDERSCORE_SYMBOL_PREFIX bool help Some architectures generate an _ in front of C symbols; things like module loading and assembly files need to know about 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 PGTABLE_LEVELS int default 2

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

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

config HAVE_EXIT_THREAD bool help An architecture implements exit_thread.

config ARCH_MMAP_RND_BITS_MIN int

config ARCH_MMAP_RND_BITS_MAX int

config ARCH_MMAP_RND_BITS_DEFAULT int

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

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

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

config ARCH_MMAP_RND_COMPAT_BITS_MIN int

config ARCH_MMAP_RND_COMPAT_BITS_MAX int

config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT int

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

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

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

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

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

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

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

config 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 ARCH_NO_COHERENT_DMA_MMAP bool

config CPU_NO_EFFICIENT_FFS def_bool n

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

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

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

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

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

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

config ARCH_OPTIONAL_KERNEL_RWX def_bool n

config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT def_bool n

config ARCH_HAS_STRICT_KERNEL_RWX def_bool n

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

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

config ARCH_HAS_STRICT_MODULE_RWX def_bool n

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

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

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

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

source "kernel/gcov/Kconfig"