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Commit | Line | Data |
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b2441318 | 1 | # SPDX-License-Identifier: GPL-2.0 |
1da177e4 LT |
2 | menu "Kernel hacking" |
3 | ||
55f327fa | 4 | config TRACE_IRQFLAGS_SUPPORT |
d013a27c | 5 | def_bool y |
55f327fa | 6 | |
1da177e4 LT |
7 | source "lib/Kconfig.debug" |
8 | ||
aeb9dd1d LB |
9 | config EARLY_PRINTK_USB |
10 | bool | |
11 | ||
6bcb13b3 BC |
12 | config X86_VERBOSE_BOOTUP |
13 | bool "Enable verbose x86 bootup info messages" | |
14 | default y | |
8f9ca475 | 15 | ---help--- |
6bcb13b3 BC |
16 | Enables the informational output from the decompression stage |
17 | (e.g. bzImage) of the boot. If you disable this you will still | |
18 | see errors. Disable this if you want silent bootup. | |
19 | ||
1da177e4 | 20 | config EARLY_PRINTK |
6a108a14 | 21 | bool "Early printk" if EXPERT |
1da177e4 | 22 | default y |
8f9ca475 | 23 | ---help--- |
1da177e4 LT |
24 | Write kernel log output directly into the VGA buffer or to a serial |
25 | port. | |
26 | ||
27 | This is useful for kernel debugging when your machine crashes very | |
28 | early before the console code is initialized. For normal operation | |
29 | it is not recommended because it looks ugly and doesn't cooperate | |
aeb9dd1d | 30 | with klogd/syslogd or the X server. You should normally say N here, |
1da177e4 LT |
31 | unless you want to debug such a crash. |
32 | ||
5c05917e YL |
33 | config EARLY_PRINTK_DBGP |
34 | bool "Early printk via EHCI debug port" | |
9749986a | 35 | depends on EARLY_PRINTK && PCI |
aeb9dd1d | 36 | select EARLY_PRINTK_USB |
8f9ca475 | 37 | ---help--- |
5c05917e YL |
38 | Write kernel log output directly into the EHCI debug 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 | |
aeb9dd1d | 43 | with klogd/syslogd or the X server. You should normally say N here, |
5c05917e YL |
44 | unless you want to debug such a crash. You need usb debug device. |
45 | ||
72548e83 MF |
46 | config EARLY_PRINTK_EFI |
47 | bool "Early printk via the EFI framebuffer" | |
48 | depends on EFI && EARLY_PRINTK | |
49 | select FONT_SUPPORT | |
50 | ---help--- | |
51 | Write kernel log output directly into the EFI framebuffer. | |
52 | ||
53 | This is useful for kernel debugging when your machine crashes very | |
54 | early before the console code is initialized. | |
55 | ||
aeb9dd1d LB |
56 | config EARLY_PRINTK_USB_XDBC |
57 | bool "Early printk via the xHCI debug port" | |
58 | depends on EARLY_PRINTK && PCI | |
59 | select EARLY_PRINTK_USB | |
60 | ---help--- | |
61 | Write kernel log output directly into the xHCI debug port. | |
62 | ||
63 | One use for this feature is kernel debugging, for example when your | |
64 | machine crashes very early before the regular console code is | |
65 | initialized. Other uses include simpler, lockless logging instead of | |
66 | a full-blown printk console driver + klogd. | |
67 | ||
68 | For normal production environments this is normally not recommended, | |
69 | because it doesn't feed events into klogd/syslogd and doesn't try to | |
70 | print anything on the screen. | |
71 | ||
72 | You should normally say N here, unless you want to debug early | |
73 | crashes or need a very simple printk logging facility. | |
74 | ||
e1a58320 SS |
75 | config X86_PTDUMP_CORE |
76 | def_bool n | |
77 | ||
926e5392 | 78 | config X86_PTDUMP |
8609d1b5 | 79 | tristate "Export kernel pagetable layout to userspace via debugfs" |
fe770bf0 | 80 | depends on DEBUG_KERNEL |
926e5392 | 81 | select DEBUG_FS |
e1a58320 | 82 | select X86_PTDUMP_CORE |
8f9ca475 | 83 | ---help--- |
926e5392 AV |
84 | Say Y here if you want to show the kernel pagetable layout in a |
85 | debugfs file. This information is only useful for kernel developers | |
86 | who are working in architecture specific areas of the kernel. | |
87 | It is probably not a good idea to enable this feature in a production | |
88 | kernel. | |
89 | If in doubt, say "N" | |
90 | ||
11cc8512 BP |
91 | config EFI_PGT_DUMP |
92 | bool "Dump the EFI pagetable" | |
e1a58320 SS |
93 | depends on EFI |
94 | select X86_PTDUMP_CORE | |
11cc8512 BP |
95 | ---help--- |
96 | Enable this if you want to dump the EFI page table before | |
97 | enabling virtual mode. This can be used to debug miscellaneous | |
98 | issues with the mapping of the EFI runtime regions into that | |
99 | table. | |
100 | ||
e1a58320 SS |
101 | config DEBUG_WX |
102 | bool "Warn on W+X mappings at boot" | |
e1a58320 SS |
103 | select X86_PTDUMP_CORE |
104 | ---help--- | |
105 | Generate a warning if any W+X mappings are found at boot. | |
106 | ||
107 | This is useful for discovering cases where the kernel is leaving | |
108 | W+X mappings after applying NX, as such mappings are a security risk. | |
109 | ||
110 | Look for a message in dmesg output like this: | |
111 | ||
112 | x86/mm: Checked W+X mappings: passed, no W+X pages found. | |
113 | ||
114 | or like this, if the check failed: | |
115 | ||
116 | x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found. | |
117 | ||
118 | Note that even if the check fails, your kernel is possibly | |
119 | still fine, as W+X mappings are not a security hole in | |
120 | themselves, what they do is that they make the exploitation | |
121 | of other unfixed kernel bugs easier. | |
122 | ||
123 | There is no runtime or memory usage effect of this option | |
124 | once the kernel has booted up - it's a one time check. | |
125 | ||
126 | If in doubt, say "Y". | |
127 | ||
102e41fd AK |
128 | config DOUBLEFAULT |
129 | default y | |
6a108a14 | 130 | bool "Enable doublefault exception handler" if EXPERT |
8f9ca475 | 131 | ---help--- |
d013a27c RD |
132 | This option allows trapping of rare doublefault exceptions that |
133 | would otherwise cause a system to silently reboot. Disabling this | |
134 | option saves about 4k and might cause you much additional grey | |
135 | hair. | |
136 | ||
3df3212f AS |
137 | config DEBUG_TLBFLUSH |
138 | bool "Set upper limit of TLB entries to flush one-by-one" | |
cd69aa6b | 139 | depends on DEBUG_KERNEL |
3df3212f AS |
140 | ---help--- |
141 | ||
142 | X86-only for now. | |
143 | ||
144 | This option allows the user to tune the amount of TLB entries the | |
145 | kernel flushes one-by-one instead of doing a full TLB flush. In | |
146 | certain situations, the former is cheaper. This is controlled by the | |
147 | tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it | |
148 | to -1, the code flushes the whole TLB unconditionally. Otherwise, | |
149 | for positive values of it, the kernel will use single TLB entry | |
150 | invalidating instructions according to the following formula: | |
151 | ||
152 | flush_entries <= active_tlb_entries / 2^tlb_flushall_shift | |
153 | ||
154 | If in doubt, say "N". | |
155 | ||
d013a27c RD |
156 | config IOMMU_DEBUG |
157 | bool "Enable IOMMU debugging" | |
966396d3 | 158 | depends on GART_IOMMU && DEBUG_KERNEL |
d013a27c | 159 | depends on X86_64 |
8f9ca475 | 160 | ---help--- |
d013a27c RD |
161 | Force the IOMMU to on even when you have less than 4GB of |
162 | memory and add debugging code. On overflow always panic. And | |
163 | allow to enable IOMMU leak tracing. Can be disabled at boot | |
164 | time with iommu=noforce. This will also enable scatter gather | |
165 | list merging. Currently not recommended for production | |
166 | code. When you use it make sure you have a big enough | |
167 | IOMMU/AGP aperture. Most of the options enabled by this can | |
168 | be set more finegrained using the iommu= command line | |
395cf969 | 169 | options. See Documentation/x86/x86_64/boot-options.txt for more |
d013a27c RD |
170 | details. |
171 | ||
2be69c79 JR |
172 | config IOMMU_STRESS |
173 | bool "Enable IOMMU stress-test mode" | |
174 | ---help--- | |
175 | This option disables various optimizations in IOMMU related | |
176 | code to do real stress testing of the IOMMU code. This option | |
177 | will cause a performance drop and should only be enabled for | |
178 | testing. | |
179 | ||
d013a27c RD |
180 | config IOMMU_LEAK |
181 | bool "IOMMU leak tracing" | |
19c1a6f5 | 182 | depends on IOMMU_DEBUG && DMA_API_DEBUG |
8f9ca475 | 183 | ---help--- |
d013a27c RD |
184 | Add a simple leak tracer to the IOMMU code. This is useful when you |
185 | are debugging a buggy device driver that leaks IOMMU mappings. | |
186 | ||
6bc5c366 PP |
187 | config HAVE_MMIOTRACE_SUPPORT |
188 | def_bool y | |
8b7d89d0 | 189 | |
ca0e9bad | 190 | config X86_DECODER_SELFTEST |
cbe5c34c OH |
191 | bool "x86 instruction decoder selftest" |
192 | depends on DEBUG_KERNEL && KPROBES | |
f8f20234 | 193 | depends on !COMPILE_TEST |
ca0e9bad MH |
194 | ---help--- |
195 | Perform x86 instruction decoder selftests at build time. | |
196 | This option is useful for checking the sanity of x86 instruction | |
197 | decoder code. | |
198 | If unsure, say "N". | |
199 | ||
6e7c4025 IM |
200 | # |
201 | # IO delay types: | |
202 | # | |
203 | ||
204 | config IO_DELAY_TYPE_0X80 | |
205 | int | |
206 | default "0" | |
207 | ||
208 | config IO_DELAY_TYPE_0XED | |
209 | int | |
210 | default "1" | |
211 | ||
212 | config IO_DELAY_TYPE_UDELAY | |
213 | int | |
214 | default "2" | |
215 | ||
216 | config IO_DELAY_TYPE_NONE | |
217 | int | |
218 | default "3" | |
219 | ||
220 | choice | |
221 | prompt "IO delay type" | |
fd59e9e9 | 222 | default IO_DELAY_0X80 |
6e7c4025 IM |
223 | |
224 | config IO_DELAY_0X80 | |
225 | bool "port 0x80 based port-IO delay [recommended]" | |
8f9ca475 | 226 | ---help--- |
6e7c4025 IM |
227 | This is the traditional Linux IO delay used for in/out_p. |
228 | It is the most tested hence safest selection here. | |
229 | ||
230 | config IO_DELAY_0XED | |
231 | bool "port 0xed based port-IO delay" | |
8f9ca475 | 232 | ---help--- |
6e7c4025 IM |
233 | Use port 0xed as the IO delay. This frees up port 0x80 which is |
234 | often used as a hardware-debug port. | |
235 | ||
236 | config IO_DELAY_UDELAY | |
237 | bool "udelay based port-IO delay" | |
8f9ca475 | 238 | ---help--- |
6e7c4025 IM |
239 | Use udelay(2) as the IO delay method. This provides the delay |
240 | while not having any side-effect on the IO port space. | |
241 | ||
242 | config IO_DELAY_NONE | |
243 | bool "no port-IO delay" | |
8f9ca475 | 244 | ---help--- |
6e7c4025 IM |
245 | No port-IO delay. Will break on old boxes that require port-IO |
246 | delay for certain operations. Should work on most new machines. | |
247 | ||
248 | endchoice | |
249 | ||
250 | if IO_DELAY_0X80 | |
251 | config DEFAULT_IO_DELAY_TYPE | |
252 | int | |
253 | default IO_DELAY_TYPE_0X80 | |
254 | endif | |
255 | ||
256 | if IO_DELAY_0XED | |
257 | config DEFAULT_IO_DELAY_TYPE | |
258 | int | |
259 | default IO_DELAY_TYPE_0XED | |
260 | endif | |
261 | ||
262 | if IO_DELAY_UDELAY | |
263 | config DEFAULT_IO_DELAY_TYPE | |
264 | int | |
265 | default IO_DELAY_TYPE_UDELAY | |
266 | endif | |
267 | ||
268 | if IO_DELAY_NONE | |
269 | config DEFAULT_IO_DELAY_TYPE | |
270 | int | |
271 | default IO_DELAY_TYPE_NONE | |
272 | endif | |
b02aae9c | 273 | |
6d7d7433 HY |
274 | config DEBUG_BOOT_PARAMS |
275 | bool "Debug boot parameters" | |
276 | depends on DEBUG_KERNEL | |
277 | depends on DEBUG_FS | |
8f9ca475 | 278 | ---help--- |
6d7d7433 HY |
279 | This option will cause struct boot_params to be exported via debugfs. |
280 | ||
0c42f392 | 281 | config CPA_DEBUG |
971a52d6 | 282 | bool "CPA self-test code" |
f316fe68 | 283 | depends on DEBUG_KERNEL |
8f9ca475 | 284 | ---help--- |
971a52d6 | 285 | Do change_page_attr() self-tests every 30 seconds. |
0c42f392 | 286 | |
60a3cdd0 IM |
287 | config OPTIMIZE_INLINING |
288 | bool "Allow gcc to uninline functions marked 'inline'" | |
8f9ca475 | 289 | ---help--- |
60a3cdd0 IM |
290 | This option determines if the kernel forces gcc to inline the functions |
291 | developers have marked 'inline'. Doing so takes away freedom from gcc to | |
292 | do what it thinks is best, which is desirable for the gcc 3.x series of | |
293 | compilers. The gcc 4.x series have a rewritten inlining algorithm and | |
63fb7085 SW |
294 | enabling this option will generate a smaller kernel there. Hopefully |
295 | this algorithm is so good that allowing gcc 4.x and above to make the | |
296 | decision will become the default in the future. Until then this option | |
297 | is there to test gcc for this. | |
c9af1e33 | 298 | |
3f9b5cc0 IM |
299 | If unsure, say N. |
300 | ||
a97439aa AL |
301 | config DEBUG_ENTRY |
302 | bool "Debug low-level entry code" | |
303 | depends on DEBUG_KERNEL | |
304 | ---help--- | |
305 | This option enables sanity checks in x86's low-level entry code. | |
306 | Some of these sanity checks may slow down kernel entries and | |
307 | exits or otherwise impact performance. | |
308 | ||
a97439aa AL |
309 | If unsure, say N. |
310 | ||
99e8b9ca DZ |
311 | config DEBUG_NMI_SELFTEST |
312 | bool "NMI Selftest" | |
4f941c57 | 313 | depends on DEBUG_KERNEL && X86_LOCAL_APIC |
99e8b9ca DZ |
314 | ---help--- |
315 | Enabling this option turns on a quick NMI selftest to verify | |
316 | that the NMI behaves correctly. | |
317 | ||
318 | This might help diagnose strange hangs that rely on NMI to | |
319 | function properly. | |
320 | ||
321 | If unsure, say N. | |
322 | ||
28a375df BD |
323 | config DEBUG_IMR_SELFTEST |
324 | bool "Isolated Memory Region self test" | |
325 | default n | |
326 | depends on INTEL_IMR | |
327 | ---help--- | |
328 | This option enables automated sanity testing of the IMR code. | |
329 | Some simple tests are run to verify IMR bounds checking, alignment | |
330 | and overlapping. This option is really only useful if you are | |
331 | debugging an IMR memory map or are modifying the IMR code and want to | |
332 | test your changes. | |
333 | ||
334 | If unsure say N here. | |
335 | ||
e97131a8 IM |
336 | config X86_DEBUG_FPU |
337 | bool "Debug the x86 FPU code" | |
338 | depends on DEBUG_KERNEL | |
339 | default y | |
340 | ---help--- | |
341 | If this option is enabled then there will be extra sanity | |
342 | checks and (boot time) debug printouts added to the kernel. | |
343 | This debugging adds some small amount of runtime overhead | |
344 | to the kernel. | |
345 | ||
346 | If unsure, say N. | |
347 | ||
956079e0 SP |
348 | config PUNIT_ATOM_DEBUG |
349 | tristate "ATOM Punit debug driver" | |
d689c64d | 350 | depends on PCI |
956079e0 SP |
351 | select DEBUG_FS |
352 | select IOSF_MBI | |
353 | ---help--- | |
354 | This is a debug driver, which gets the power states | |
355 | of all Punit North Complex devices. The power states of | |
356 | each device is exposed as part of the debugfs interface. | |
357 | The current power state can be read from | |
358 | /sys/kernel/debug/punit_atom/dev_power_state | |
359 | ||
81d38719 JP |
360 | choice |
361 | prompt "Choose kernel unwinder" | |
fc72ae40 JP |
362 | default UNWINDER_ORC if X86_64 |
363 | default UNWINDER_FRAME_POINTER if X86_32 | |
81d38719 JP |
364 | ---help--- |
365 | This determines which method will be used for unwinding kernel stack | |
366 | traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack, | |
367 | livepatch, lockdep, and more. | |
368 | ||
11af8474 | 369 | config UNWINDER_ORC |
ee9f8fce | 370 | bool "ORC unwinder" |
81d38719 | 371 | depends on X86_64 |
ee9f8fce JP |
372 | select STACK_VALIDATION |
373 | ---help--- | |
374 | This option enables the ORC (Oops Rewind Capability) unwinder for | |
375 | unwinding kernel stack traces. It uses a custom data format which is | |
376 | a simplified version of the DWARF Call Frame Information standard. | |
377 | ||
378 | This unwinder is more accurate across interrupt entry frames than the | |
a34a766f JP |
379 | frame pointer unwinder. It also enables a 5-10% performance |
380 | improvement across the entire kernel compared to frame pointers. | |
ee9f8fce JP |
381 | |
382 | Enabling this option will increase the kernel's runtime memory usage | |
383 | by roughly 2-4MB, depending on your kernel config. | |
384 | ||
fc72ae40 JP |
385 | config UNWINDER_FRAME_POINTER |
386 | bool "Frame pointer unwinder" | |
387 | select FRAME_POINTER | |
388 | ---help--- | |
389 | This option enables the frame pointer unwinder for unwinding kernel | |
390 | stack traces. | |
391 | ||
392 | The unwinder itself is fast and it uses less RAM than the ORC | |
393 | unwinder, but the kernel text size will grow by ~3% and the kernel's | |
394 | overall performance will degrade by roughly 5-10%. | |
395 | ||
396 | This option is recommended if you want to use the livepatch | |
397 | consistency model, as this is currently the only way to get a | |
398 | reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE). | |
399 | ||
11af8474 | 400 | config UNWINDER_GUESS |
81d38719 JP |
401 | bool "Guess unwinder" |
402 | depends on EXPERT | |
0a373d4f | 403 | depends on !STACKDEPOT |
81d38719 JP |
404 | ---help--- |
405 | This option enables the "guess" unwinder for unwinding kernel stack | |
406 | traces. It scans the stack and reports every kernel text address it | |
407 | finds. Some of the addresses it reports may be incorrect. | |
408 | ||
409 | While this option often produces false positives, it can still be | |
410 | useful in many cases. Unlike the other unwinders, it has no runtime | |
411 | overhead. | |
412 | ||
413 | endchoice | |
414 | ||
415 | config FRAME_POINTER | |
11af8474 | 416 | depends on !UNWINDER_ORC && !UNWINDER_GUESS |
81d38719 | 417 | bool |
ee9f8fce | 418 | |
c9af1e33 | 419 | endmenu |