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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_INTEL_MID
47 bool "Early printk for Intel MID platform support"
48 depends on EARLY_PRINTK && X86_INTEL_MID
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 Say Y here if you want to check the overflows of kernel, IRQ
67 and exception stacks. This option will cause messages of the
68 stacks in detail when free stack space drops below a certain
69 limit.
70 If in doubt, say "N".
71
72config X86_PTDUMP
73 bool "Export kernel pagetable layout to userspace via debugfs"
74 depends on DEBUG_KERNEL
75 select DEBUG_FS
76 ---help---
77 Say Y here if you want to show the kernel pagetable layout in a
78 debugfs file. This information is only useful for kernel developers
79 who are working in architecture specific areas of the kernel.
80 It is probably not a good idea to enable this feature in a production
81 kernel.
82 If in doubt, say "N"
83
84config DEBUG_RODATA
85 bool "Write protect kernel read-only data structures"
86 default y
87 depends on DEBUG_KERNEL
88 ---help---
89 Mark the kernel read-only data as write-protected in the pagetables,
90 in order to catch accidental (and incorrect) writes to such const
91 data. This is recommended so that we can catch kernel bugs sooner.
92 If in doubt, say "Y".
93
94config DEBUG_RODATA_TEST
95 bool "Testcase for the DEBUG_RODATA feature"
96 depends on DEBUG_RODATA
97 default y
98 ---help---
99 This option enables a testcase for the DEBUG_RODATA
100 feature as well as for the change_page_attr() infrastructure.
101 If in doubt, say "N"
102
103config DEBUG_SET_MODULE_RONX
104 bool "Set loadable kernel module data as NX and text as RO"
105 depends on MODULES
106 ---help---
107 This option helps catch unintended modifications to loadable
108 kernel module's text and read-only data. It also prevents execution
109 of module data. Such protection may interfere with run-time code
110 patching and dynamic kernel tracing - and they might also protect
111 against certain classes of kernel exploits.
112 If in doubt, say "N".
113
114config DEBUG_NX_TEST
115 tristate "Testcase for the NX non-executable stack feature"
116 depends on DEBUG_KERNEL && m
117 ---help---
118 This option enables a testcase for the CPU NX capability
119 and the software setup of this feature.
120 If in doubt, say "N"
121
122config DOUBLEFAULT
123 default y
124 bool "Enable doublefault exception handler" if EXPERT
125 depends on X86_32
126 ---help---
127 This option allows trapping of rare doublefault exceptions that
128 would otherwise cause a system to silently reboot. Disabling this
129 option saves about 4k and might cause you much additional grey
130 hair.
131
132config IOMMU_DEBUG
133 bool "Enable IOMMU debugging"
134 depends on GART_IOMMU && DEBUG_KERNEL
135 depends on X86_64
136 ---help---
137 Force the IOMMU to on even when you have less than 4GB of
138 memory and add debugging code. On overflow always panic. And
139 allow to enable IOMMU leak tracing. Can be disabled at boot
140 time with iommu=noforce. This will also enable scatter gather
141 list merging. Currently not recommended for production
142 code. When you use it make sure you have a big enough
143 IOMMU/AGP aperture. Most of the options enabled by this can
144 be set more finegrained using the iommu= command line
145 options. See Documentation/x86/x86_64/boot-options.txt for more
146 details.
147
148config IOMMU_STRESS
149 bool "Enable IOMMU stress-test mode"
150 ---help---
151 This option disables various optimizations in IOMMU related
152 code to do real stress testing of the IOMMU code. This option
153 will cause a performance drop and should only be enabled for
154 testing.
155
156config IOMMU_LEAK
157 bool "IOMMU leak tracing"
158 depends on IOMMU_DEBUG && DMA_API_DEBUG
159 ---help---
160 Add a simple leak tracer to the IOMMU code. This is useful when you
161 are debugging a buggy device driver that leaks IOMMU mappings.
162
163config HAVE_MMIOTRACE_SUPPORT
164 def_bool y
165
166config X86_DECODER_SELFTEST
167 bool "x86 instruction decoder selftest"
168 depends on DEBUG_KERNEL && KPROBES
169 ---help---
170 Perform x86 instruction decoder selftests at build time.
171 This option is useful for checking the sanity of x86 instruction
172 decoder code.
173 If unsure, say "N".
174
175#
176# IO delay types:
177#
178
179config IO_DELAY_TYPE_0X80
180 int
181 default "0"
182
183config IO_DELAY_TYPE_0XED
184 int
185 default "1"
186
187config IO_DELAY_TYPE_UDELAY
188 int
189 default "2"
190
191config IO_DELAY_TYPE_NONE
192 int
193 default "3"
194
195choice
196 prompt "IO delay type"
197 default IO_DELAY_0X80
198
199config IO_DELAY_0X80
200 bool "port 0x80 based port-IO delay [recommended]"
201 ---help---
202 This is the traditional Linux IO delay used for in/out_p.
203 It is the most tested hence safest selection here.
204
205config IO_DELAY_0XED
206 bool "port 0xed based port-IO delay"
207 ---help---
208 Use port 0xed as the IO delay. This frees up port 0x80 which is
209 often used as a hardware-debug port.
210
211config IO_DELAY_UDELAY
212 bool "udelay based port-IO delay"
213 ---help---
214 Use udelay(2) as the IO delay method. This provides the delay
215 while not having any side-effect on the IO port space.
216
217config IO_DELAY_NONE
218 bool "no port-IO delay"
219 ---help---
220 No port-IO delay. Will break on old boxes that require port-IO
221 delay for certain operations. Should work on most new machines.
222
223endchoice
224
225if IO_DELAY_0X80
226config DEFAULT_IO_DELAY_TYPE
227 int
228 default IO_DELAY_TYPE_0X80
229endif
230
231if IO_DELAY_0XED
232config DEFAULT_IO_DELAY_TYPE
233 int
234 default IO_DELAY_TYPE_0XED
235endif
236
237if IO_DELAY_UDELAY
238config DEFAULT_IO_DELAY_TYPE
239 int
240 default IO_DELAY_TYPE_UDELAY
241endif
242
243if IO_DELAY_NONE
244config DEFAULT_IO_DELAY_TYPE
245 int
246 default IO_DELAY_TYPE_NONE
247endif
248
249config DEBUG_BOOT_PARAMS
250 bool "Debug boot parameters"
251 depends on DEBUG_KERNEL
252 depends on DEBUG_FS
253 ---help---
254 This option will cause struct boot_params to be exported via debugfs.
255
256config CPA_DEBUG
257 bool "CPA self-test code"
258 depends on DEBUG_KERNEL
259 ---help---
260 Do change_page_attr() self-tests every 30 seconds.
261
262config OPTIMIZE_INLINING
263 bool "Allow gcc to uninline functions marked 'inline'"
264 ---help---
265 This option determines if the kernel forces gcc to inline the functions
266 developers have marked 'inline'. Doing so takes away freedom from gcc to
267 do what it thinks is best, which is desirable for the gcc 3.x series of
268 compilers. The gcc 4.x series have a rewritten inlining algorithm and
269 enabling this option will generate a smaller kernel there. Hopefully
270 this algorithm is so good that allowing gcc 4.x and above to make the
271 decision will become the default in the future. Until then this option
272 is there to test gcc for this.
273
274 If unsure, say N.
275
276config DEBUG_STRICT_USER_COPY_CHECKS
277 bool "Strict copy size checks"
278 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
279 ---help---
280 Enabling this option turns a certain set of sanity checks for user
281 copy operations into compile time failures.
282
283 The copy_from_user() etc checks are there to help test if there
284 are sufficient security checks on the length argument of
285 the copy operation, by having gcc prove that the argument is
286 within bounds.
287
288 If unsure, or if you run an older (pre 4.4) gcc, say N.
289
290config DEBUG_NMI_SELFTEST
291 bool "NMI Selftest"
292 depends on DEBUG_KERNEL && X86_LOCAL_APIC
293 ---help---
294 Enabling this option turns on a quick NMI selftest to verify
295 that the NMI behaves correctly.
296
297 This might help diagnose strange hangs that rely on NMI to
298 function properly.
299
300 If unsure, say N.
301
302endmenu