arch/Kconfig

#
# General architecture dependent options
#

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 an 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

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

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 HAVE_SYSCALL_WRAPPERS
	bool

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_NMI_WATCHDOG
	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_ATTRS
	bool

config HAVE_DMA_CONTIGUOUS
	bool

config USE_GENERIC_SMP_HELPERS
	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_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_MUTEX_CPU_RELAX
	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_WANT_OLD_COMPAT_IPC
	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_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 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_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


source "kernel/gcov/Kconfig"