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1menu "Kernel hacking"
2
55f327fa 3config TRACE_IRQFLAGS_SUPPORT
d013a27c 4 def_bool y
55f327fa 5
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6source "lib/Kconfig.debug"
7
d092633b 8config STRICT_DEVMEM
16104b55 9 bool "Filter access to /dev/mem"
8f9ca475 10 ---help---
f2d0f1de 11 If this option is disabled, you allow userspace (root) access to all
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12 of memory, including kernel and userspace memory. Accidental
13 access to this is obviously disastrous, but specific access can
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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.
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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.
ae531c26 24
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25config X86_VERBOSE_BOOTUP
26 bool "Enable verbose x86 bootup info messages"
27 default y
8f9ca475 28 ---help---
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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
1da177e4 33config EARLY_PRINTK
6a108a14 34 bool "Early printk" if EXPERT
1da177e4 35 default y
8f9ca475 36 ---help---
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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
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46config EARLY_PRINTK_DBGP
47 bool "Early printk via EHCI debug port"
9749986a 48 depends on EARLY_PRINTK && PCI
8f9ca475 49 ---help---
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50 Write kernel log output directly into the EHCI debug port.
51
52 This is useful for kernel debugging when your machine crashes very
53 early before the console code is initialized. For normal operation
54 it is not recommended because it looks ugly and doesn't cooperate
55 with klogd/syslogd or the X server. You should normally N here,
56 unless you want to debug such a crash. You need usb debug device.
57
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58config EARLY_PRINTK_EFI
59 bool "Early printk via the EFI framebuffer"
60 depends on EFI && EARLY_PRINTK
61 select FONT_SUPPORT
62 ---help---
63 Write kernel log output directly into the EFI framebuffer.
64
65 This is useful for kernel debugging when your machine crashes very
66 early before the console code is initialized.
67
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68config X86_PTDUMP_CORE
69 def_bool n
70
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71config X86_PTDUMP
72 bool "Export kernel pagetable layout to userspace via debugfs"
fe770bf0 73 depends on DEBUG_KERNEL
926e5392 74 select DEBUG_FS
e1a58320 75 select X86_PTDUMP_CORE
8f9ca475 76 ---help---
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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
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84config EFI_PGT_DUMP
85 bool "Dump the EFI pagetable"
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86 depends on EFI
87 select X86_PTDUMP_CORE
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88 ---help---
89 Enable this if you want to dump the EFI page table before
90 enabling virtual mode. This can be used to debug miscellaneous
91 issues with the mapping of the EFI runtime regions into that
92 table.
93
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94config DEBUG_RODATA
95 bool "Write protect kernel read-only data structures"
11201e60 96 default y
63aaf308 97 depends on DEBUG_KERNEL
8f9ca475 98 ---help---
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99 Mark the kernel read-only data as write-protected in the pagetables,
100 in order to catch accidental (and incorrect) writes to such const
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101 data. This is recommended so that we can catch kernel bugs sooner.
102 If in doubt, say "Y".
63aaf308 103
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104config DEBUG_RODATA_TEST
105 bool "Testcase for the DEBUG_RODATA feature"
106 depends on DEBUG_RODATA
72370f2a 107 default y
8f9ca475 108 ---help---
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109 This option enables a testcase for the DEBUG_RODATA
110 feature as well as for the change_page_attr() infrastructure.
111 If in doubt, say "N"
112
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113config DEBUG_WX
114 bool "Warn on W+X mappings at boot"
115 depends on DEBUG_RODATA
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116 select X86_PTDUMP_CORE
117 ---help---
118 Generate a warning if any W+X mappings are found at boot.
119
120 This is useful for discovering cases where the kernel is leaving
121 W+X mappings after applying NX, as such mappings are a security risk.
122
123 Look for a message in dmesg output like this:
124
125 x86/mm: Checked W+X mappings: passed, no W+X pages found.
126
127 or like this, if the check failed:
128
129 x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
130
131 Note that even if the check fails, your kernel is possibly
132 still fine, as W+X mappings are not a security hole in
133 themselves, what they do is that they make the exploitation
134 of other unfixed kernel bugs easier.
135
136 There is no runtime or memory usage effect of this option
137 once the kernel has booted up - it's a one time check.
138
139 If in doubt, say "Y".
140
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141config DEBUG_SET_MODULE_RONX
142 bool "Set loadable kernel module data as NX and text as RO"
143 depends on MODULES
144 ---help---
145 This option helps catch unintended modifications to loadable
146 kernel module's text and read-only data. It also prevents execution
147 of module data. Such protection may interfere with run-time code
148 patching and dynamic kernel tracing - and they might also protect
149 against certain classes of kernel exploits.
150 If in doubt, say "N".
151
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152config DEBUG_NX_TEST
153 tristate "Testcase for the NX non-executable stack feature"
154 depends on DEBUG_KERNEL && m
8f9ca475 155 ---help---
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156 This option enables a testcase for the CPU NX capability
157 and the software setup of this feature.
158 If in doubt, say "N"
159
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160config DOUBLEFAULT
161 default y
6a108a14 162 bool "Enable doublefault exception handler" if EXPERT
8f9ca475 163 ---help---
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164 This option allows trapping of rare doublefault exceptions that
165 would otherwise cause a system to silently reboot. Disabling this
166 option saves about 4k and might cause you much additional grey
167 hair.
168
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169config DEBUG_TLBFLUSH
170 bool "Set upper limit of TLB entries to flush one-by-one"
cd69aa6b 171 depends on DEBUG_KERNEL
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172 ---help---
173
174 X86-only for now.
175
176 This option allows the user to tune the amount of TLB entries the
177 kernel flushes one-by-one instead of doing a full TLB flush. In
178 certain situations, the former is cheaper. This is controlled by the
179 tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
180 to -1, the code flushes the whole TLB unconditionally. Otherwise,
181 for positive values of it, the kernel will use single TLB entry
182 invalidating instructions according to the following formula:
183
184 flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
185
186 If in doubt, say "N".
187
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188config IOMMU_DEBUG
189 bool "Enable IOMMU debugging"
966396d3 190 depends on GART_IOMMU && DEBUG_KERNEL
d013a27c 191 depends on X86_64
8f9ca475 192 ---help---
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193 Force the IOMMU to on even when you have less than 4GB of
194 memory and add debugging code. On overflow always panic. And
195 allow to enable IOMMU leak tracing. Can be disabled at boot
196 time with iommu=noforce. This will also enable scatter gather
197 list merging. Currently not recommended for production
198 code. When you use it make sure you have a big enough
199 IOMMU/AGP aperture. Most of the options enabled by this can
200 be set more finegrained using the iommu= command line
395cf969 201 options. See Documentation/x86/x86_64/boot-options.txt for more
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202 details.
203
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204config IOMMU_STRESS
205 bool "Enable IOMMU stress-test mode"
206 ---help---
207 This option disables various optimizations in IOMMU related
208 code to do real stress testing of the IOMMU code. This option
209 will cause a performance drop and should only be enabled for
210 testing.
211
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212config IOMMU_LEAK
213 bool "IOMMU leak tracing"
19c1a6f5 214 depends on IOMMU_DEBUG && DMA_API_DEBUG
8f9ca475 215 ---help---
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216 Add a simple leak tracer to the IOMMU code. This is useful when you
217 are debugging a buggy device driver that leaks IOMMU mappings.
218
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219config HAVE_MMIOTRACE_SUPPORT
220 def_bool y
8b7d89d0 221
ca0e9bad 222config X86_DECODER_SELFTEST
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223 bool "x86 instruction decoder selftest"
224 depends on DEBUG_KERNEL && KPROBES
f8f20234 225 depends on !COMPILE_TEST
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226 ---help---
227 Perform x86 instruction decoder selftests at build time.
228 This option is useful for checking the sanity of x86 instruction
229 decoder code.
230 If unsure, say "N".
231
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232#
233# IO delay types:
234#
235
236config IO_DELAY_TYPE_0X80
237 int
238 default "0"
239
240config IO_DELAY_TYPE_0XED
241 int
242 default "1"
243
244config IO_DELAY_TYPE_UDELAY
245 int
246 default "2"
247
248config IO_DELAY_TYPE_NONE
249 int
250 default "3"
251
252choice
253 prompt "IO delay type"
fd59e9e9 254 default IO_DELAY_0X80
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255
256config IO_DELAY_0X80
257 bool "port 0x80 based port-IO delay [recommended]"
8f9ca475 258 ---help---
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259 This is the traditional Linux IO delay used for in/out_p.
260 It is the most tested hence safest selection here.
261
262config IO_DELAY_0XED
263 bool "port 0xed based port-IO delay"
8f9ca475 264 ---help---
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265 Use port 0xed as the IO delay. This frees up port 0x80 which is
266 often used as a hardware-debug port.
267
268config IO_DELAY_UDELAY
269 bool "udelay based port-IO delay"
8f9ca475 270 ---help---
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271 Use udelay(2) as the IO delay method. This provides the delay
272 while not having any side-effect on the IO port space.
273
274config IO_DELAY_NONE
275 bool "no port-IO delay"
8f9ca475 276 ---help---
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277 No port-IO delay. Will break on old boxes that require port-IO
278 delay for certain operations. Should work on most new machines.
279
280endchoice
281
282if IO_DELAY_0X80
283config DEFAULT_IO_DELAY_TYPE
284 int
285 default IO_DELAY_TYPE_0X80
286endif
287
288if IO_DELAY_0XED
289config DEFAULT_IO_DELAY_TYPE
290 int
291 default IO_DELAY_TYPE_0XED
292endif
293
294if IO_DELAY_UDELAY
295config DEFAULT_IO_DELAY_TYPE
296 int
297 default IO_DELAY_TYPE_UDELAY
298endif
299
300if IO_DELAY_NONE
301config DEFAULT_IO_DELAY_TYPE
302 int
303 default IO_DELAY_TYPE_NONE
304endif
b02aae9c 305
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306config DEBUG_BOOT_PARAMS
307 bool "Debug boot parameters"
308 depends on DEBUG_KERNEL
309 depends on DEBUG_FS
8f9ca475 310 ---help---
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311 This option will cause struct boot_params to be exported via debugfs.
312
0c42f392 313config CPA_DEBUG
971a52d6 314 bool "CPA self-test code"
f316fe68 315 depends on DEBUG_KERNEL
8f9ca475 316 ---help---
971a52d6 317 Do change_page_attr() self-tests every 30 seconds.
0c42f392 318
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319config OPTIMIZE_INLINING
320 bool "Allow gcc to uninline functions marked 'inline'"
8f9ca475 321 ---help---
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322 This option determines if the kernel forces gcc to inline the functions
323 developers have marked 'inline'. Doing so takes away freedom from gcc to
324 do what it thinks is best, which is desirable for the gcc 3.x series of
325 compilers. The gcc 4.x series have a rewritten inlining algorithm and
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326 enabling this option will generate a smaller kernel there. Hopefully
327 this algorithm is so good that allowing gcc 4.x and above to make the
328 decision will become the default in the future. Until then this option
329 is there to test gcc for this.
c9af1e33 330
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331 If unsure, say N.
332
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333config DEBUG_ENTRY
334 bool "Debug low-level entry code"
335 depends on DEBUG_KERNEL
336 ---help---
337 This option enables sanity checks in x86's low-level entry code.
338 Some of these sanity checks may slow down kernel entries and
339 exits or otherwise impact performance.
340
341 This is currently used to help test NMI code.
342
343 If unsure, say N.
344
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345config DEBUG_NMI_SELFTEST
346 bool "NMI Selftest"
4f941c57 347 depends on DEBUG_KERNEL && X86_LOCAL_APIC
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348 ---help---
349 Enabling this option turns on a quick NMI selftest to verify
350 that the NMI behaves correctly.
351
352 This might help diagnose strange hangs that rely on NMI to
353 function properly.
354
355 If unsure, say N.
356
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357config DEBUG_IMR_SELFTEST
358 bool "Isolated Memory Region self test"
359 default n
360 depends on INTEL_IMR
361 ---help---
362 This option enables automated sanity testing of the IMR code.
363 Some simple tests are run to verify IMR bounds checking, alignment
364 and overlapping. This option is really only useful if you are
365 debugging an IMR memory map or are modifying the IMR code and want to
366 test your changes.
367
368 If unsure say N here.
369
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370config X86_DEBUG_STATIC_CPU_HAS
371 bool "Debug alternatives"
372 depends on DEBUG_KERNEL
373 ---help---
374 This option causes additional code to be generated which
375 fails if static_cpu_has() is used before alternatives have
376 run.
377
378 If unsure, say N.
379
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380config X86_DEBUG_FPU
381 bool "Debug the x86 FPU code"
382 depends on DEBUG_KERNEL
383 default y
384 ---help---
385 If this option is enabled then there will be extra sanity
386 checks and (boot time) debug printouts added to the kernel.
387 This debugging adds some small amount of runtime overhead
388 to the kernel.
389
390 If unsure, say N.
391
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392config PUNIT_ATOM_DEBUG
393 tristate "ATOM Punit debug driver"
394 select DEBUG_FS
395 select IOSF_MBI
396 ---help---
397 This is a debug driver, which gets the power states
398 of all Punit North Complex devices. The power states of
399 each device is exposed as part of the debugfs interface.
400 The current power state can be read from
401 /sys/kernel/debug/punit_atom/dev_power_state
402
c9af1e33 403endmenu