1# SPDX-License-Identifier: GPL-2.0
  2
  3config EARLY_PRINTK_USB
  4	bool
  5
  6config X86_VERBOSE_BOOTUP
  7	bool "Enable verbose x86 bootup info messages"
  8	default y
  9	help
 10	  Enables the informational output from the decompression stage
 11	  (e.g. bzImage) of the boot. If you disable this you will still
 12	  see errors. Disable this if you want silent bootup.
 13
 14config EARLY_PRINTK
 15	bool "Early printk" if EXPERT
 16	default y
 17	help
 18	  Write kernel log output directly into the VGA buffer or to a serial
 19	  port.
 20
 21	  This is useful for kernel debugging when your machine crashes very
 22	  early before the console code is initialized. For normal operation
 23	  it is not recommended because it looks ugly and doesn't cooperate
 24	  with klogd/syslogd or the X server. You should normally say N here,
 25	  unless you want to debug such a crash.
 26
 27config EARLY_PRINTK_DBGP
 28	bool "Early printk via EHCI debug port"
 29	depends on EARLY_PRINTK && PCI
 30	select EARLY_PRINTK_USB
 31	help
 32	  Write kernel log output directly into the EHCI debug port.
 33
 34	  This is useful for kernel debugging when your machine crashes very
 35	  early before the console code is initialized. For normal operation
 36	  it is not recommended because it looks ugly and doesn't cooperate
 37	  with klogd/syslogd or the X server. You should normally say N here,
 38	  unless you want to debug such a crash. You need usb debug device.
 39
 40config EARLY_PRINTK_USB_XDBC
 41	bool "Early printk via the xHCI debug port"
 42	depends on EARLY_PRINTK && PCI
 43	select EARLY_PRINTK_USB
 44	help
 45	  Write kernel log output directly into the xHCI debug port.
 46
 47	  One use for this feature is kernel debugging, for example when your
 48	  machine crashes very early before the regular console code is
 49	  initialized. Other uses include simpler, lockless logging instead of
 50	  a full-blown printk console driver + klogd.
 51
 52	  For normal production environments this is normally not recommended,
 53	  because it doesn't feed events into klogd/syslogd and doesn't try to
 54	  print anything on the screen.
 55
 56	  You should normally say N here, unless you want to debug early
 57	  crashes or need a very simple printk logging facility.
 58
 59config EFI_PGT_DUMP
 60	bool "Dump the EFI pagetable"
 61	depends on EFI
 62	select PTDUMP_CORE
 63	help
 64	  Enable this if you want to dump the EFI page table before
 65	  enabling virtual mode. This can be used to debug miscellaneous
 66	  issues with the mapping of the EFI runtime regions into that
 67	  table.
 68
 69config DEBUG_TLBFLUSH
 70	bool "Set upper limit of TLB entries to flush one-by-one"
 71	depends on DEBUG_KERNEL
 72	help
 73	  X86-only for now.
 74
 75	  This option allows the user to tune the amount of TLB entries the
 76	  kernel flushes one-by-one instead of doing a full TLB flush. In
 77	  certain situations, the former is cheaper. This is controlled by the
 78	  tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 79	  to -1, the code flushes the whole TLB unconditionally. Otherwise,
 80	  for positive values of it, the kernel will use single TLB entry
 81	  invalidating instructions according to the following formula:
 82
 83	  flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 84
 85	  If in doubt, say "N".
 86
 87config IOMMU_DEBUG
 88	bool "Enable IOMMU debugging"
 89	depends on GART_IOMMU && DEBUG_KERNEL
 90	depends on X86_64
 91	help
 92	  Force the IOMMU to on even when you have less than 4GB of
 93	  memory and add debugging code. On overflow always panic. And
 94	  allow to enable IOMMU leak tracing. Can be disabled at boot
 95	  time with iommu=noforce. This will also enable scatter gather
 96	  list merging.  Currently not recommended for production
 97	  code. When you use it make sure you have a big enough
 98	  IOMMU/AGP aperture.  Most of the options enabled by this can
 99	  be set more finegrained using the iommu= command line
100	  options. See Documentation/arch/x86/x86_64/boot-options.rst for more
101	  details.
102
103config IOMMU_LEAK
104	bool "IOMMU leak tracing"
105	depends on IOMMU_DEBUG && DMA_API_DEBUG
106	help
107	  Add a simple leak tracer to the IOMMU code. This is useful when you
108	  are debugging a buggy device driver that leaks IOMMU mappings.
109
110config HAVE_MMIOTRACE_SUPPORT
111	def_bool y
112
113config X86_DECODER_SELFTEST
114	bool "x86 instruction decoder selftest"
115	depends on DEBUG_KERNEL && INSTRUCTION_DECODER
116	depends on !COMPILE_TEST
117	help
118	  Perform x86 instruction decoder selftests at build time.
119	  This option is useful for checking the sanity of x86 instruction
120	  decoder code.
121	  If unsure, say "N".
122
123choice
124	prompt "IO delay type"
125	default IO_DELAY_0X80
126
127config IO_DELAY_0X80
128	bool "port 0x80 based port-IO delay [recommended]"
129	help
130	  This is the traditional Linux IO delay used for in/out_p.
131	  It is the most tested hence safest selection here.
132
133config IO_DELAY_0XED
134	bool "port 0xed based port-IO delay"
135	help
136	  Use port 0xed as the IO delay. This frees up port 0x80 which is
137	  often used as a hardware-debug port.
138
139config IO_DELAY_UDELAY
140	bool "udelay based port-IO delay"
141	help
142	  Use udelay(2) as the IO delay method. This provides the delay
143	  while not having any side-effect on the IO port space.
144
145config IO_DELAY_NONE
146	bool "no port-IO delay"
147	help
148	  No port-IO delay. Will break on old boxes that require port-IO
149	  delay for certain operations. Should work on most new machines.
150
151endchoice
152
153config DEBUG_BOOT_PARAMS
154	bool "Debug boot parameters"
155	depends on DEBUG_KERNEL
156	depends on DEBUG_FS
157	help
158	  This option will cause struct boot_params to be exported via debugfs.
159
160config CPA_DEBUG
161	bool "CPA self-test code"
162	depends on DEBUG_KERNEL
163	help
164	  Do change_page_attr() self-tests every 30 seconds.
165
166config DEBUG_ENTRY
167	bool "Debug low-level entry code"
168	depends on DEBUG_KERNEL
169	help
170	  This option enables sanity checks in x86's low-level entry code.
171	  Some of these sanity checks may slow down kernel entries and
172	  exits or otherwise impact performance.
173
174	  If unsure, say N.
175
176config DEBUG_NMI_SELFTEST
177	bool "NMI Selftest"
178	depends on DEBUG_KERNEL && X86_LOCAL_APIC
179	help
180	  Enabling this option turns on a quick NMI selftest to verify
181	  that the NMI behaves correctly.
182
183	  This might help diagnose strange hangs that rely on NMI to
184	  function properly.
185
186	  If unsure, say N.
187
188config DEBUG_IMR_SELFTEST
189	bool "Isolated Memory Region self test"
190	depends on INTEL_IMR
191	help
192	  This option enables automated sanity testing of the IMR code.
193	  Some simple tests are run to verify IMR bounds checking, alignment
194	  and overlapping. This option is really only useful if you are
195	  debugging an IMR memory map or are modifying the IMR code and want to
196	  test your changes.
197
198	  If unsure say N here.
199
200config X86_DEBUG_FPU
201	bool "Debug the x86 FPU code"
202	depends on DEBUG_KERNEL
203	default y
204	help
205	  If this option is enabled then there will be extra sanity
206	  checks and (boot time) debug printouts added to the kernel.
207	  This debugging adds some small amount of runtime overhead
208	  to the kernel.
209
210	  If unsure, say N.
211
212config PUNIT_ATOM_DEBUG
213	tristate "ATOM Punit debug driver"
214	depends on PCI
215	select DEBUG_FS
216	select IOSF_MBI
217	help
218	  This is a debug driver, which gets the power states
219	  of all Punit North Complex devices. The power states of
220	  each device is exposed as part of the debugfs interface.
221	  The current power state can be read from
222	  /sys/kernel/debug/punit_atom/dev_power_state
223
224choice
225	prompt "Choose kernel unwinder"
226	default UNWINDER_ORC if X86_64
227	default UNWINDER_FRAME_POINTER if X86_32
228	help
229	  This determines which method will be used for unwinding kernel stack
230	  traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
231	  livepatch, lockdep, and more.
232
233config UNWINDER_ORC
234	bool "ORC unwinder"
235	depends on X86_64
236	select OBJTOOL
237	help
238	  This option enables the ORC (Oops Rewind Capability) unwinder for
239	  unwinding kernel stack traces.  It uses a custom data format which is
240	  a simplified version of the DWARF Call Frame Information standard.
241
242	  This unwinder is more accurate across interrupt entry frames than the
243	  frame pointer unwinder.  It also enables a 5-10% performance
244	  improvement across the entire kernel compared to frame pointers.
245
246	  Enabling this option will increase the kernel's runtime memory usage
247	  by roughly 2-4MB, depending on your kernel config.
248
249config UNWINDER_FRAME_POINTER
250	bool "Frame pointer unwinder"
251	select ARCH_WANT_FRAME_POINTERS
252	select FRAME_POINTER
253	help
254	  This option enables the frame pointer unwinder for unwinding kernel
255	  stack traces.
256
257	  The unwinder itself is fast and it uses less RAM than the ORC
258	  unwinder, but the kernel text size will grow by ~3% and the kernel's
259	  overall performance will degrade by roughly 5-10%.
260
261config UNWINDER_GUESS
262	bool "Guess unwinder"
263	depends on EXPERT
264	depends on !STACKDEPOT
265	help
266	  This option enables the "guess" unwinder for unwinding kernel stack
267	  traces.  It scans the stack and reports every kernel text address it
268	  finds.  Some of the addresses it reports may be incorrect.
269
270	  While this option often produces false positives, it can still be
271	  useful in many cases.  Unlike the other unwinders, it has no runtime
272	  overhead.
273
274endchoice

  1menu "Kernel hacking"
  2
  3config TRACE_IRQFLAGS_SUPPORT
  4	def_bool y
  5
  6source "lib/Kconfig.debug"
  7
  8config STRICT_DEVMEM
  9	bool "Filter access to /dev/mem"
 10	---help---
 11	  If this option is disabled, you allow userspace (root) access to all
 12	  of memory, including kernel and userspace memory. Accidental
 13	  access to this is obviously disastrous, but specific access can
 14	  be used by people debugging the kernel. Note that with PAT support
 15	  enabled, even in this case there are restrictions on /dev/mem
 16	  use due to the cache aliasing requirements.
 17
 18	  If this option is switched on, the /dev/mem file only allows
 19	  userspace access to PCI space and the BIOS code and data regions.
 20	  This is sufficient for dosemu and X and all common users of
 21	  /dev/mem.
 22
 23	  If in doubt, say Y.
 24
 25config X86_VERBOSE_BOOTUP
 26	bool "Enable verbose x86 bootup info messages"
 27	default y
 28	---help---
 29	  Enables the informational output from the decompression stage
 30	  (e.g. bzImage) of the boot. If you disable this you will still
 31	  see errors. Disable this if you want silent bootup.
 32
 33config EARLY_PRINTK
 34	bool "Early printk" if EXPERT
 35	default y
 36	---help---
 37	  Write kernel log output directly into the VGA buffer or to a serial
 38	  port.
 39
 40	  This is useful for kernel debugging when your machine crashes very
 41	  early before the console code is initialized. For normal operation
 42	  it is not recommended because it looks ugly and doesn't cooperate
 43	  with klogd/syslogd or the X server. You should normally N here,
 44	  unless you want to debug such a crash.
 45
 46config EARLY_PRINTK_MRST
 47	bool "Early printk for MRST platform support"
 48	depends on EARLY_PRINTK && X86_MRST
 49
 50config EARLY_PRINTK_DBGP
 51	bool "Early printk via EHCI debug port"
 52	depends on EARLY_PRINTK && PCI
 53	---help---
 54	  Write kernel log output directly into the EHCI debug port.
 55
 56	  This is useful for kernel debugging when your machine crashes very
 57	  early before the console code is initialized. For normal operation
 58	  it is not recommended because it looks ugly and doesn't cooperate
 59	  with klogd/syslogd or the X server. You should normally N here,
 60	  unless you want to debug such a crash. You need usb debug device.
 61
 62config DEBUG_STACKOVERFLOW
 63	bool "Check for stack overflows"
 64	depends on DEBUG_KERNEL
 65	---help---
 66	  This option will cause messages to be printed if free stack space
 67	  drops below a certain limit.
 68
 69config X86_PTDUMP
 70	bool "Export kernel pagetable layout to userspace via debugfs"
 71	depends on DEBUG_KERNEL
 72	select DEBUG_FS
 73	---help---
 74	  Say Y here if you want to show the kernel pagetable layout in a
 75	  debugfs file. This information is only useful for kernel developers
 76	  who are working in architecture specific areas of the kernel.
 77	  It is probably not a good idea to enable this feature in a production
 78	  kernel.
 79	  If in doubt, say "N"
 80
 81config DEBUG_RODATA
 82	bool "Write protect kernel read-only data structures"
 83	default y
 84	depends on DEBUG_KERNEL
 85	---help---
 86	  Mark the kernel read-only data as write-protected in the pagetables,
 87	  in order to catch accidental (and incorrect) writes to such const
 88	  data. This is recommended so that we can catch kernel bugs sooner.
 89	  If in doubt, say "Y".
 90
 91config DEBUG_RODATA_TEST
 92	bool "Testcase for the DEBUG_RODATA feature"
 93	depends on DEBUG_RODATA
 94	default y
 95	---help---
 96	  This option enables a testcase for the DEBUG_RODATA
 97	  feature as well as for the change_page_attr() infrastructure.
 98	  If in doubt, say "N"
 99
100config DEBUG_SET_MODULE_RONX
101	bool "Set loadable kernel module data as NX and text as RO"
102	depends on MODULES
103	---help---
104	  This option helps catch unintended modifications to loadable
105	  kernel module's text and read-only data. It also prevents execution
106	  of module data. Such protection may interfere with run-time code
107	  patching and dynamic kernel tracing - and they might also protect
108	  against certain classes of kernel exploits.
109	  If in doubt, say "N".
110
111config DEBUG_NX_TEST
112	tristate "Testcase for the NX non-executable stack feature"
113	depends on DEBUG_KERNEL && m
114	---help---
115	  This option enables a testcase for the CPU NX capability
116	  and the software setup of this feature.
117	  If in doubt, say "N"
118
119config DOUBLEFAULT
120	default y
121	bool "Enable doublefault exception handler" if EXPERT
122	depends on X86_32
123	---help---
124	  This option allows trapping of rare doublefault exceptions that
125	  would otherwise cause a system to silently reboot. Disabling this
126	  option saves about 4k and might cause you much additional grey
127	  hair.
128
129config IOMMU_DEBUG
130	bool "Enable IOMMU debugging"
131	depends on GART_IOMMU && DEBUG_KERNEL
132	depends on X86_64
133	---help---
134	  Force the IOMMU to on even when you have less than 4GB of
135	  memory and add debugging code. On overflow always panic. And
136	  allow to enable IOMMU leak tracing. Can be disabled at boot
137	  time with iommu=noforce. This will also enable scatter gather
138	  list merging.  Currently not recommended for production
139	  code. When you use it make sure you have a big enough
140	  IOMMU/AGP aperture.  Most of the options enabled by this can
141	  be set more finegrained using the iommu= command line
142	  options. See Documentation/x86_64/boot-options.txt for more
143	  details.
144
145config IOMMU_STRESS
146	bool "Enable IOMMU stress-test mode"
147	---help---
148	  This option disables various optimizations in IOMMU related
149	  code to do real stress testing of the IOMMU code. This option
150	  will cause a performance drop and should only be enabled for
151	  testing.
152
153config IOMMU_LEAK
154	bool "IOMMU leak tracing"
155	depends on IOMMU_DEBUG && DMA_API_DEBUG
156	---help---
157	  Add a simple leak tracer to the IOMMU code. This is useful when you
158	  are debugging a buggy device driver that leaks IOMMU mappings.
159
160config HAVE_MMIOTRACE_SUPPORT
161	def_bool y
162
163config X86_DECODER_SELFTEST
164	bool "x86 instruction decoder selftest"
165	depends on DEBUG_KERNEL && KPROBES
166	---help---
167	 Perform x86 instruction decoder selftests at build time.
168	 This option is useful for checking the sanity of x86 instruction
169	 decoder code.
170	 If unsure, say "N".
171
172#
173# IO delay types:
174#
175
176config IO_DELAY_TYPE_0X80
177	int
178	default "0"
179
180config IO_DELAY_TYPE_0XED
181	int
182	default "1"
183
184config IO_DELAY_TYPE_UDELAY
185	int
186	default "2"
187
188config IO_DELAY_TYPE_NONE
189	int
190	default "3"
191
192choice
193	prompt "IO delay type"
194	default IO_DELAY_0X80
195
196config IO_DELAY_0X80
197	bool "port 0x80 based port-IO delay [recommended]"
198	---help---
199	  This is the traditional Linux IO delay used for in/out_p.
200	  It is the most tested hence safest selection here.
201
202config IO_DELAY_0XED
203	bool "port 0xed based port-IO delay"
204	---help---
205	  Use port 0xed as the IO delay. This frees up port 0x80 which is
206	  often used as a hardware-debug port.
207
208config IO_DELAY_UDELAY
209	bool "udelay based port-IO delay"
210	---help---
211	  Use udelay(2) as the IO delay method. This provides the delay
212	  while not having any side-effect on the IO port space.
213
214config IO_DELAY_NONE
215	bool "no port-IO delay"
216	---help---
217	  No port-IO delay. Will break on old boxes that require port-IO
218	  delay for certain operations. Should work on most new machines.
219
220endchoice
221
222if IO_DELAY_0X80
223config DEFAULT_IO_DELAY_TYPE
224	int
225	default IO_DELAY_TYPE_0X80
226endif
227
228if IO_DELAY_0XED
229config DEFAULT_IO_DELAY_TYPE
230	int
231	default IO_DELAY_TYPE_0XED
232endif
233
234if IO_DELAY_UDELAY
235config DEFAULT_IO_DELAY_TYPE
236	int
237	default IO_DELAY_TYPE_UDELAY
238endif
239
240if IO_DELAY_NONE
241config DEFAULT_IO_DELAY_TYPE
242	int
243	default IO_DELAY_TYPE_NONE
244endif
245
246config DEBUG_BOOT_PARAMS
247	bool "Debug boot parameters"
248	depends on DEBUG_KERNEL
249	depends on DEBUG_FS
250	---help---
251	  This option will cause struct boot_params to be exported via debugfs.
252
253config CPA_DEBUG
254	bool "CPA self-test code"
255	depends on DEBUG_KERNEL
256	---help---
257	  Do change_page_attr() self-tests every 30 seconds.
258
259config OPTIMIZE_INLINING
260	bool "Allow gcc to uninline functions marked 'inline'"
261	---help---
262	  This option determines if the kernel forces gcc to inline the functions
263	  developers have marked 'inline'. Doing so takes away freedom from gcc to
264	  do what it thinks is best, which is desirable for the gcc 3.x series of
265	  compilers. The gcc 4.x series have a rewritten inlining algorithm and
266	  enabling this option will generate a smaller kernel there. Hopefully
267	  this algorithm is so good that allowing gcc 4.x and above to make the
268	  decision will become the default in the future. Until then this option
269	  is there to test gcc for this.
270
271	  If unsure, say N.
272
273config DEBUG_STRICT_USER_COPY_CHECKS
274	bool "Strict copy size checks"
275	depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
276	---help---
277	  Enabling this option turns a certain set of sanity checks for user
278	  copy operations into compile time failures.
279
280	  The copy_from_user() etc checks are there to help test if there
281	  are sufficient security checks on the length argument of
282	  the copy operation, by having gcc prove that the argument is
283	  within bounds.
284
285	  If unsure, or if you run an older (pre 4.4) gcc, say N.
286
287endmenu