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Linus Torvalds1da177e2005-04-16 15:20:36 -07001menu "Kernel hacking"
2
Ingo Molnar55f327f2006-07-03 00:24:43 -07003config TRACE_IRQFLAGS_SUPPORT
Randy Dunlapd013a272007-10-24 15:50:43 -07004 def_bool y
Ingo Molnar55f327f2006-07-03 00:24:43 -07005
Linus Torvalds1da177e2005-04-16 15:20:36 -07006source "lib/Kconfig.debug"
7
Ingo Molnard0926332008-07-18 00:26:59 +02008config STRICT_DEVMEM
Stefan Richter16104b52008-06-05 22:47:13 +02009 bool "Filter access to /dev/mem"
Ingo Molnar8f9ca472009-02-05 16:21:53 +010010 ---help---
Linus Torvaldsf2d0f1d2008-07-21 13:04:08 -070011 If this option is disabled, you allow userspace (root) access to all
Stefan Richter16104b52008-06-05 22:47:13 +020012 of memory, including kernel and userspace memory. Accidental
13 access to this is obviously disastrous, but specific access can
Ingo Molnard0926332008-07-18 00:26:59 +020014 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.
Stefan Richter16104b52008-06-05 22:47:13 +020017
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.
Arjan van de Venae531c22008-04-24 23:40:47 +020024
Ben Collins6bcb13b2008-06-18 14:04:35 -040025config X86_VERBOSE_BOOTUP
26 bool "Enable verbose x86 bootup info messages"
27 default y
Ingo Molnar8f9ca472009-02-05 16:21:53 +010028 ---help---
Ben Collins6bcb13b2008-06-18 14:04:35 -040029 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070033config EARLY_PRINTK
David Rientjes6a108a12011-01-20 14:44:16 -080034 bool "Early printk" if EXPERT
Linus Torvalds1da177e2005-04-16 15:20:36 -070035 default y
Ingo Molnar8f9ca472009-02-05 16:21:53 +010036 ---help---
Linus Torvalds1da177e2005-04-16 15:20:36 -070037 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
Feng Tangc20b5c32010-09-13 15:08:55 +080046config EARLY_PRINTK_MRST
47 bool "Early printk for MRST platform support"
48 depends on EARLY_PRINTK && X86_MRST
49
Yinghai Lu5c059172008-07-24 17:29:40 -070050config EARLY_PRINTK_DBGP
51 bool "Early printk via EHCI debug port"
Ingo Molnar97499862008-07-26 17:28:11 +020052 depends on EARLY_PRINTK && PCI
Ingo Molnar8f9ca472009-02-05 16:21:53 +010053 ---help---
Yinghai Lu5c059172008-07-24 17:29:40 -070054 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070062config DEBUG_STACKOVERFLOW
63 bool "Check for stack overflows"
64 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +010065 ---help---
Adrian Bunkdab175f2005-07-27 11:44:23 -070066 This option will cause messages to be printed if free stack space
67 drops below a certain limit.
Linus Torvalds1da177e2005-04-16 15:20:36 -070068
Linus Torvalds1da177e2005-04-16 15:20:36 -070069config DEBUG_STACK_USAGE
70 bool "Stack utilization instrumentation"
71 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +010072 ---help---
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 Enables the display of the minimum amount of free stack which each
74 task has ever had available in the sysrq-T and sysrq-P debug output.
75
76 This option will slow down process creation somewhat.
77
travis@sgi.comc49a4952008-01-30 13:33:22 +010078config DEBUG_PER_CPU_MAPS
79 bool "Debug access to per_cpu maps"
80 depends on DEBUG_KERNEL
Ingo Molnar3e5095d2009-01-27 17:07:08 +010081 depends on SMP
Ingo Molnar8f9ca472009-02-05 16:21:53 +010082 ---help---
travis@sgi.comc49a4952008-01-30 13:33:22 +010083 Say Y to verify that the per_cpu map being accessed has
84 been setup. Adds a fair amount of code to kernel memory
85 and decreases performance.
86
87 Say N if unsure.
88
Arjan van de Ven926e5392008-04-17 17:40:45 +020089config X86_PTDUMP
90 bool "Export kernel pagetable layout to userspace via debugfs"
H. Peter Anvinfe770bf2008-04-17 17:40:45 +020091 depends on DEBUG_KERNEL
Arjan van de Ven926e5392008-04-17 17:40:45 +020092 select DEBUG_FS
Ingo Molnar8f9ca472009-02-05 16:21:53 +010093 ---help---
Arjan van de Ven926e5392008-04-17 17:40:45 +020094 Say Y here if you want to show the kernel pagetable layout in a
95 debugfs file. This information is only useful for kernel developers
96 who are working in architecture specific areas of the kernel.
97 It is probably not a good idea to enable this feature in a production
98 kernel.
99 If in doubt, say "N"
100
Arjan van de Ven63aaf302006-01-06 00:12:02 -0800101config DEBUG_RODATA
102 bool "Write protect kernel read-only data structures"
Ingo Molnar11201e62008-01-30 13:33:32 +0100103 default y
Arjan van de Ven63aaf302006-01-06 00:12:02 -0800104 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100105 ---help---
Arjan van de Ven63aaf302006-01-06 00:12:02 -0800106 Mark the kernel read-only data as write-protected in the pagetables,
107 in order to catch accidental (and incorrect) writes to such const
Ingo Molnar11201e62008-01-30 13:33:32 +0100108 data. This is recommended so that we can catch kernel bugs sooner.
109 If in doubt, say "Y".
Arjan van de Ven63aaf302006-01-06 00:12:02 -0800110
Ingo Molnaraba83912008-01-30 13:34:09 +0100111config DEBUG_RODATA_TEST
112 bool "Testcase for the DEBUG_RODATA feature"
113 depends on DEBUG_RODATA
Ingo Molnar72370f22008-02-13 16:15:34 +0100114 default y
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100115 ---help---
Ingo Molnaraba83912008-01-30 13:34:09 +0100116 This option enables a testcase for the DEBUG_RODATA
117 feature as well as for the change_page_attr() infrastructure.
118 If in doubt, say "N"
119
matthieu castet84e1c6b2010-11-16 22:35:16 +0100120config DEBUG_SET_MODULE_RONX
121 bool "Set loadable kernel module data as NX and text as RO"
122 depends on MODULES
123 ---help---
124 This option helps catch unintended modifications to loadable
125 kernel module's text and read-only data. It also prevents execution
126 of module data. Such protection may interfere with run-time code
127 patching and dynamic kernel tracing - and they might also protect
128 against certain classes of kernel exploits.
129 If in doubt, say "N".
130
Ingo Molnaraba83912008-01-30 13:34:09 +0100131config DEBUG_NX_TEST
132 tristate "Testcase for the NX non-executable stack feature"
133 depends on DEBUG_KERNEL && m
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100134 ---help---
Ingo Molnaraba83912008-01-30 13:34:09 +0100135 This option enables a testcase for the CPU NX capability
136 and the software setup of this feature.
137 If in doubt, say "N"
138
Andi Kleen102e41f2006-04-18 12:35:22 +0200139config DOUBLEFAULT
140 default y
David Rientjes6a108a12011-01-20 14:44:16 -0800141 bool "Enable doublefault exception handler" if EXPERT
Randy Dunlapd013a272007-10-24 15:50:43 -0700142 depends on X86_32
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100143 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700144 This option allows trapping of rare doublefault exceptions that
145 would otherwise cause a system to silently reboot. Disabling this
146 option saves about 4k and might cause you much additional grey
147 hair.
148
149config IOMMU_DEBUG
150 bool "Enable IOMMU debugging"
Joerg Roedel966396d2007-10-24 12:49:48 +0200151 depends on GART_IOMMU && DEBUG_KERNEL
Randy Dunlapd013a272007-10-24 15:50:43 -0700152 depends on X86_64
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100153 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700154 Force the IOMMU to on even when you have less than 4GB of
155 memory and add debugging code. On overflow always panic. And
156 allow to enable IOMMU leak tracing. Can be disabled at boot
157 time with iommu=noforce. This will also enable scatter gather
158 list merging. Currently not recommended for production
159 code. When you use it make sure you have a big enough
160 IOMMU/AGP aperture. Most of the options enabled by this can
161 be set more finegrained using the iommu= command line
162 options. See Documentation/x86_64/boot-options.txt for more
163 details.
164
Joerg Roedel2be69c72009-05-22 12:15:49 +0200165config IOMMU_STRESS
166 bool "Enable IOMMU stress-test mode"
167 ---help---
168 This option disables various optimizations in IOMMU related
169 code to do real stress testing of the IOMMU code. This option
170 will cause a performance drop and should only be enabled for
171 testing.
172
Randy Dunlapd013a272007-10-24 15:50:43 -0700173config IOMMU_LEAK
174 bool "IOMMU leak tracing"
FUJITA Tomonori19c1a6f2009-04-14 09:43:19 +0900175 depends on IOMMU_DEBUG && DMA_API_DEBUG
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100176 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700177 Add a simple leak tracer to the IOMMU code. This is useful when you
178 are debugging a buggy device driver that leaks IOMMU mappings.
179
Pekka Paalanen6bc5c362009-01-03 21:23:51 +0200180config HAVE_MMIOTRACE_SUPPORT
181 def_bool y
Pekka Paalanen8b7d89d2008-05-12 21:20:56 +0200182
Masami Hiramatsuca0e9ba2009-08-13 16:34:21 -0400183config X86_DECODER_SELFTEST
OGAWA Hirofumicbe5c342009-12-06 20:14:29 +0900184 bool "x86 instruction decoder selftest"
185 depends on DEBUG_KERNEL && KPROBES
Masami Hiramatsuca0e9ba2009-08-13 16:34:21 -0400186 ---help---
187 Perform x86 instruction decoder selftests at build time.
188 This option is useful for checking the sanity of x86 instruction
189 decoder code.
190 If unsure, say "N".
191
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100192#
193# IO delay types:
194#
195
196config IO_DELAY_TYPE_0X80
197 int
198 default "0"
199
200config IO_DELAY_TYPE_0XED
201 int
202 default "1"
203
204config IO_DELAY_TYPE_UDELAY
205 int
206 default "2"
207
208config IO_DELAY_TYPE_NONE
209 int
210 default "3"
211
212choice
213 prompt "IO delay type"
Ingo Molnarfd59e9e2008-02-17 20:20:24 +0100214 default IO_DELAY_0X80
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100215
216config IO_DELAY_0X80
217 bool "port 0x80 based port-IO delay [recommended]"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100218 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100219 This is the traditional Linux IO delay used for in/out_p.
220 It is the most tested hence safest selection here.
221
222config IO_DELAY_0XED
223 bool "port 0xed based port-IO delay"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100224 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100225 Use port 0xed as the IO delay. This frees up port 0x80 which is
226 often used as a hardware-debug port.
227
228config IO_DELAY_UDELAY
229 bool "udelay based port-IO delay"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100230 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100231 Use udelay(2) as the IO delay method. This provides the delay
232 while not having any side-effect on the IO port space.
233
234config IO_DELAY_NONE
235 bool "no port-IO delay"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100236 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100237 No port-IO delay. Will break on old boxes that require port-IO
238 delay for certain operations. Should work on most new machines.
239
240endchoice
241
242if IO_DELAY_0X80
243config DEFAULT_IO_DELAY_TYPE
244 int
245 default IO_DELAY_TYPE_0X80
246endif
247
248if IO_DELAY_0XED
249config DEFAULT_IO_DELAY_TYPE
250 int
251 default IO_DELAY_TYPE_0XED
252endif
253
254if IO_DELAY_UDELAY
255config DEFAULT_IO_DELAY_TYPE
256 int
257 default IO_DELAY_TYPE_UDELAY
258endif
259
260if IO_DELAY_NONE
261config DEFAULT_IO_DELAY_TYPE
262 int
263 default IO_DELAY_TYPE_NONE
264endif
Rene Hermanb02aae92008-01-30 13:30:05 +0100265
Huang, Ying6d7d7432008-01-30 13:32:51 +0100266config DEBUG_BOOT_PARAMS
267 bool "Debug boot parameters"
268 depends on DEBUG_KERNEL
269 depends on DEBUG_FS
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100270 ---help---
Huang, Ying6d7d7432008-01-30 13:32:51 +0100271 This option will cause struct boot_params to be exported via debugfs.
272
Andi Kleen0c42f392008-01-30 13:33:42 +0100273config CPA_DEBUG
Ingo Molnar971a52d2008-02-06 22:39:45 +0100274 bool "CPA self-test code"
Ingo Molnarf316fe62008-01-30 13:34:04 +0100275 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100276 ---help---
Ingo Molnar971a52d2008-02-06 22:39:45 +0100277 Do change_page_attr() self-tests every 30 seconds.
Andi Kleen0c42f392008-01-30 13:33:42 +0100278
Ingo Molnar60a3cdd2008-03-03 12:38:52 +0100279config OPTIMIZE_INLINING
280 bool "Allow gcc to uninline functions marked 'inline'"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100281 ---help---
Ingo Molnar60a3cdd2008-03-03 12:38:52 +0100282 This option determines if the kernel forces gcc to inline the functions
283 developers have marked 'inline'. Doing so takes away freedom from gcc to
284 do what it thinks is best, which is desirable for the gcc 3.x series of
285 compilers. The gcc 4.x series have a rewritten inlining algorithm and
Sitsofe Wheeler63fb7082008-10-11 20:27:53 +0100286 enabling this option will generate a smaller kernel there. Hopefully
287 this algorithm is so good that allowing gcc 4.x and above to make the
288 decision will become the default in the future. Until then this option
289 is there to test gcc for this.
Ingo Molnarc9af1e32008-04-30 08:48:45 +0200290
Ingo Molnar3f9b5cc2008-07-18 16:30:05 +0200291 If unsure, say N.
292
Arjan van de Ven63312b62009-10-02 07:50:50 -0700293config DEBUG_STRICT_USER_COPY_CHECKS
294 bool "Strict copy size checks"
Arjan van de Venad8f4352009-10-06 07:04:52 -0700295 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
Arjan van de Ven63312b62009-10-02 07:50:50 -0700296 ---help---
297 Enabling this option turns a certain set of sanity checks for user
298 copy operations into compile time failures.
299
300 The copy_from_user() etc checks are there to help test if there
301 are sufficient security checks on the length argument of
302 the copy operation, by having gcc prove that the argument is
303 within bounds.
304
305 If unsure, or if you run an older (pre 4.4) gcc, say N.
306
Ingo Molnarc9af1e32008-04-30 08:48:45 +0200307endmenu