linux/arch/x86/Kconfig.debug

# SPDX-License-Identifier: GPL-2.0

config EARLY_PRINTK_USB
	bool

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 say N here,
	  unless you want to debug such a crash.

config EARLY_PRINTK_DBGP
	bool "Early printk via EHCI debug port"
	depends on EARLY_PRINTK && PCI
	select EARLY_PRINTK_USB
	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 say N here,
	  unless you want to debug such a crash. You need usb debug device.

config EARLY_PRINTK_USB_XDBC
	bool "Early printk via the xHCI debug port"
	depends on EARLY_PRINTK && PCI
	select EARLY_PRINTK_USB
	help
	  Write kernel log output directly into the xHCI debug port.

	  One use for this feature is kernel debugging, for example when your
	  machine crashes very early before the regular console code is
	  initialized. Other uses include simpler, lockless logging instead of
	  a full-blown printk console driver + klogd.

	  For normal production environments this is normally not recommended,
	  because it doesn't feed events into klogd/syslogd and doesn't try to
	  print anything on the screen.

	  You should normally say N here, unless you want to debug early
	  crashes or need a very simple printk logging facility.

config EFI_PGT_DUMP
	bool "Dump the EFI pagetable"
	depends on EFI
	select PTDUMP_CORE
	help
	  Enable this if you want to dump the EFI page table before
	  enabling virtual mode. This can be used to debug miscellaneous
	  issues with the mapping of the EFI runtime regions into that
	  table.

config DEBUG_TLBFLUSH
	bool "Set upper limit of TLB entries to flush one-by-one"
	depends on DEBUG_KERNEL
	help
	  X86-only for now.

	  This option allows the user to tune the amount of TLB entries the
	  kernel flushes one-by-one instead of doing a full TLB flush. In
	  certain situations, the former is cheaper. This is controlled by the
	  tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
	  to -1, the code flushes the whole TLB unconditionally. Otherwise,
	  for positive values of it, the kernel will use single TLB entry
	  invalidating instructions according to the following formula:

	  flush_entries <= active_tlb_entries / 2^tlb_flushall_shift

	  If in doubt, say "N".

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/arch/x86/x86_64/boot-options.rst for more
	  details.

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 && INSTRUCTION_DECODER
	depends on !COMPILE_TEST
	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".

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

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 DEBUG_ENTRY
	bool "Debug low-level entry code"
	depends on DEBUG_KERNEL
	help
	  This option enables sanity checks in x86's low-level entry code.
	  Some of these sanity checks may slow down kernel entries and
	  exits or otherwise impact performance.

	  If unsure, 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.

config DEBUG_IMR_SELFTEST
	bool "Isolated Memory Region self test"
	depends on INTEL_IMR
	help
	  This option enables automated sanity testing of the IMR code.
	  Some simple tests are run to verify IMR bounds checking, alignment
	  and overlapping. This option is really only useful if you are
	  debugging an IMR memory map or are modifying the IMR code and want to
	  test your changes.

	  If unsure say N here.

config X86_DEBUG_FPU
	bool "Debug the x86 FPU code"
	depends on DEBUG_KERNEL
	default y
	help
	  If this option is enabled then there will be extra sanity
	  checks and (boot time) debug printouts added to the kernel.
	  This debugging adds some small amount of runtime overhead
	  to the kernel.

	  If unsure, say N.

config PUNIT_ATOM_DEBUG
	tristate "ATOM Punit debug driver"
	depends on PCI
	select DEBUG_FS
	select IOSF_MBI
	help
	  This is a debug driver, which gets the power states
	  of all Punit North Complex devices. The power states of
	  each device is exposed as part of the debugfs interface.
	  The current power state can be read from
	  /sys/kernel/debug/punit_atom/dev_power_state

choice
	prompt "Choose kernel unwinder"
	default UNWINDER_ORC if X86_64
	default UNWINDER_FRAME_POINTER if X86_32
	help
	  This determines which method will be used for unwinding kernel stack
	  traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
	  livepatch, lockdep, and more.

config UNWINDER_ORC
	bool "ORC unwinder"
	depends on X86_64
	select OBJTOOL
	help
	  This option enables the ORC (Oops Rewind Capability) unwinder for
	  unwinding kernel stack traces.  It uses a custom data format which is
	  a simplified version of the DWARF Call Frame Information standard.

	  This unwinder is more accurate across interrupt entry frames than the
	  frame pointer unwinder.  It also enables a 5-10% performance
	  improvement across the entire kernel compared to frame pointers.

	  Enabling this option will increase the kernel's runtime memory usage
	  by roughly 2-4MB, depending on your kernel config.

config UNWINDER_FRAME_POINTER
	bool "Frame pointer unwinder"
	select ARCH_WANT_FRAME_POINTERS
	select FRAME_POINTER
	help
	  This option enables the frame pointer unwinder for unwinding kernel
	  stack traces.

	  The unwinder itself is fast and it uses less RAM than the ORC
	  unwinder, but the kernel text size will grow by ~3% and the kernel's
	  overall performance will degrade by roughly 5-10%.

config UNWINDER_GUESS
	bool "Guess unwinder"
	depends on EXPERT
	depends on !STACKDEPOT
	help
	  This option enables the "guess" unwinder for unwinding kernel stack
	  traces.  It scans the stack and reports every kernel text address it
	  finds.  Some of the addresses it reports may be incorrect.

	  While this option often produces false positives, it can still be
	  useful in many cases.  Unlike the other unwinders, it has no runtime
	  overhead.

endchoice