menu "Kernel hacking"

  config TRACE_IRQFLAGS_SUPPORT

  	def_bool y

  source "lib/Kconfig.debug"

  config STRICT_DEVMEM

  	bool "Filter access to /dev/mem"

  	---help---

  	  If this option is disabled, you allow userspace (root) access to all

  	  of memory, including kernel and userspace memory. Accidental
  	  access to this is obviously disastrous, but specific access can

  	  be used by people debugging the kernel. Note that with PAT support
  	  enabled, even in this case there are restrictions on /dev/mem
  	  use due to the cache aliasing requirements.

  
  	  If this option is switched on, the /dev/mem file only allows
  	  userspace access to PCI space and the BIOS code and data regions.
  	  This is sufficient for dosemu and X and all common users of
  	  /dev/mem.
  
  	  If in doubt, say Y.

  config X86_VERBOSE_BOOTUP
  	bool "Enable verbose x86 bootup info messages"
  	default y

  	---help---

  	  Enables the informational output from the decompression stage
  	  (e.g. bzImage) of the boot. If you disable this you will still
  	  see errors. Disable this if you want silent bootup.

  config EARLY_PRINTK

  	bool "Early printk" if EXPERT

  	default y

  	---help---

  	  Write kernel log output directly into the VGA buffer or to a serial
  	  port.
  
  	  This is useful for kernel debugging when your machine crashes very
  	  early before the console code is initialized. For normal operation
  	  it is not recommended because it looks ugly and doesn't cooperate
  	  with klogd/syslogd or the X server. You should normally N here,
  	  unless you want to debug such a crash.

  config EARLY_PRINTK_INTEL_MID
  	bool "Early printk for Intel MID platform support"
  	depends on EARLY_PRINTK && X86_INTEL_MID

  config EARLY_PRINTK_DBGP
  	bool "Early printk via EHCI debug port"

  	depends on EARLY_PRINTK && PCI

  	---help---

  	  Write kernel log output directly into the EHCI debug port.
  
  	  This is useful for kernel debugging when your machine crashes very
  	  early before the console code is initialized. For normal operation
  	  it is not recommended because it looks ugly and doesn't cooperate
  	  with klogd/syslogd or the X server. You should normally N here,
  	  unless you want to debug such a crash. You need usb debug device.

  config DEBUG_STACKOVERFLOW
  	bool "Check for stack overflows"
  	depends on DEBUG_KERNEL

  	---help---

  	  Say Y here if you want to check the overflows of kernel, IRQ
  	  and exception stacks. This option will cause messages of the
  	  stacks in detail when free stack space drops below a certain
  	  limit.
  	  If in doubt, say "N".

  config X86_PTDUMP
  	bool "Export kernel pagetable layout to userspace via debugfs"

  	depends on DEBUG_KERNEL

  	select DEBUG_FS

  	---help---

  	  Say Y here if you want to show the kernel pagetable layout in a
  	  debugfs file. This information is only useful for kernel developers
  	  who are working in architecture specific areas of the kernel.
  	  It is probably not a good idea to enable this feature in a production
  	  kernel.
  	  If in doubt, say "N"

  config DEBUG_RODATA
  	bool "Write protect kernel read-only data structures"

  	default y

  	depends on DEBUG_KERNEL

  	---help---

  	  Mark the kernel read-only data as write-protected in the pagetables,
  	  in order to catch accidental (and incorrect) writes to such const

  	  data. This is recommended so that we can catch kernel bugs sooner.
  	  If in doubt, say "Y".

  config DEBUG_RODATA_TEST
  	bool "Testcase for the DEBUG_RODATA feature"
  	depends on DEBUG_RODATA

  	default y

  	---help---

  	  This option enables a testcase for the DEBUG_RODATA
  	  feature as well as for the change_page_attr() infrastructure.
  	  If in doubt, say "N"

  config DEBUG_SET_MODULE_RONX
  	bool "Set loadable kernel module data as NX and text as RO"
  	depends on MODULES
  	---help---
  	  This option helps catch unintended modifications to loadable
  	  kernel module's text and read-only data. It also prevents execution
  	  of module data. Such protection may interfere with run-time code
  	  patching and dynamic kernel tracing - and they might also protect
  	  against certain classes of kernel exploits.
  	  If in doubt, say "N".

  config DEBUG_NX_TEST
  	tristate "Testcase for the NX non-executable stack feature"
  	depends on DEBUG_KERNEL && m

  	---help---

  	  This option enables a testcase for the CPU NX capability
  	  and the software setup of this feature.
  	  If in doubt, say "N"

  config DOUBLEFAULT
  	default y

  	bool "Enable doublefault exception handler" if EXPERT

  	depends on X86_32

  	---help---

  	  This option allows trapping of rare doublefault exceptions that
  	  would otherwise cause a system to silently reboot. Disabling this
  	  option saves about 4k and might cause you much additional grey
  	  hair.
  
  config IOMMU_DEBUG
  	bool "Enable IOMMU debugging"

  	depends on GART_IOMMU && DEBUG_KERNEL

  	depends on X86_64

  	---help---

  	  Force the IOMMU to on even when you have less than 4GB of
  	  memory and add debugging code. On overflow always panic. And
  	  allow to enable IOMMU leak tracing. Can be disabled at boot
  	  time with iommu=noforce. This will also enable scatter gather
  	  list merging.  Currently not recommended for production
  	  code. When you use it make sure you have a big enough
  	  IOMMU/AGP aperture.  Most of the options enabled by this can
  	  be set more finegrained using the iommu= command line

  	  options. See Documentation/x86/x86_64/boot-options.txt for more

  	  details.

  config IOMMU_STRESS
  	bool "Enable IOMMU stress-test mode"
  	---help---
  	  This option disables various optimizations in IOMMU related
  	  code to do real stress testing of the IOMMU code. This option
  	  will cause a performance drop and should only be enabled for
  	  testing.

  config IOMMU_LEAK
  	bool "IOMMU leak tracing"

  	depends on IOMMU_DEBUG && DMA_API_DEBUG

  	---help---

  	  Add a simple leak tracer to the IOMMU code. This is useful when you
  	  are debugging a buggy device driver that leaks IOMMU mappings.

  config HAVE_MMIOTRACE_SUPPORT
  	def_bool y

  config X86_DECODER_SELFTEST

  	bool "x86 instruction decoder selftest"
  	depends on DEBUG_KERNEL && KPROBES

  	---help---
  	 Perform x86 instruction decoder selftests at build time.
  	 This option is useful for checking the sanity of x86 instruction
  	 decoder code.
  	 If unsure, say "N".

  #
  # IO delay types:
  #
  
  config IO_DELAY_TYPE_0X80
  	int
  	default "0"
  
  config IO_DELAY_TYPE_0XED
  	int
  	default "1"
  
  config IO_DELAY_TYPE_UDELAY
  	int
  	default "2"
  
  config IO_DELAY_TYPE_NONE
  	int
  	default "3"
  
  choice
  	prompt "IO delay type"

  	default IO_DELAY_0X80

  
  config IO_DELAY_0X80
  	bool "port 0x80 based port-IO delay [recommended]"

  	---help---

  	  This is the traditional Linux IO delay used for in/out_p.
  	  It is the most tested hence safest selection here.
  
  config IO_DELAY_0XED
  	bool "port 0xed based port-IO delay"

  	---help---

  	  Use port 0xed as the IO delay. This frees up port 0x80 which is
  	  often used as a hardware-debug port.
  
  config IO_DELAY_UDELAY
  	bool "udelay based port-IO delay"

  	---help---

  	  Use udelay(2) as the IO delay method. This provides the delay
  	  while not having any side-effect on the IO port space.
  
  config IO_DELAY_NONE
  	bool "no port-IO delay"

  	---help---

  	  No port-IO delay. Will break on old boxes that require port-IO
  	  delay for certain operations. Should work on most new machines.
  
  endchoice
  
  if IO_DELAY_0X80
  config DEFAULT_IO_DELAY_TYPE
  	int
  	default IO_DELAY_TYPE_0X80
  endif
  
  if IO_DELAY_0XED
  config DEFAULT_IO_DELAY_TYPE
  	int
  	default IO_DELAY_TYPE_0XED
  endif
  
  if IO_DELAY_UDELAY
  config DEFAULT_IO_DELAY_TYPE
  	int
  	default IO_DELAY_TYPE_UDELAY
  endif
  
  if IO_DELAY_NONE
  config DEFAULT_IO_DELAY_TYPE
  	int
  	default IO_DELAY_TYPE_NONE
  endif

  config DEBUG_BOOT_PARAMS
  	bool "Debug boot parameters"
  	depends on DEBUG_KERNEL
  	depends on DEBUG_FS

  	---help---

  	  This option will cause struct boot_params to be exported via debugfs.

  config CPA_DEBUG

  	bool "CPA self-test code"

  	depends on DEBUG_KERNEL

  	---help---

  	  Do change_page_attr() self-tests every 30 seconds.

  config OPTIMIZE_INLINING
  	bool "Allow gcc to uninline functions marked 'inline'"

  	---help---

  	  This option determines if the kernel forces gcc to inline the functions
  	  developers have marked 'inline'. Doing so takes away freedom from gcc to
  	  do what it thinks is best, which is desirable for the gcc 3.x series of
  	  compilers. The gcc 4.x series have a rewritten inlining algorithm and

  	  enabling this option will generate a smaller kernel there. Hopefully
  	  this algorithm is so good that allowing gcc 4.x and above to make the
  	  decision will become the default in the future. Until then this option
  	  is there to test gcc for this.

  	  If unsure, say N.

  config DEBUG_STRICT_USER_COPY_CHECKS
  	bool "Strict copy size checks"

  	depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING

  	---help---
  	  Enabling this option turns a certain set of sanity checks for user
  	  copy operations into compile time failures.
  
  	  The copy_from_user() etc checks are there to help test if there
  	  are sufficient security checks on the length argument of
  	  the copy operation, by having gcc prove that the argument is
  	  within bounds.
  
  	  If unsure, or if you run an older (pre 4.4) gcc, say N.

  config DEBUG_NMI_SELFTEST
  	bool "NMI Selftest"

  	depends on DEBUG_KERNEL && X86_LOCAL_APIC

  	---help---
  	  Enabling this option turns on a quick NMI selftest to verify
  	  that the NMI behaves correctly.
  
  	  This might help diagnose strange hangs that rely on NMI to
  	  function properly.
  
  	  If unsure, say N.

  endmenu