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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 Richter16104b552008-06-05 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 Richter16104b552008-06-05 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 Richter16104b552008-06-05 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
Arjan van de Ven926e5392008-04-17 17:40:45 +020069config X86_PTDUMP
70 bool "Export kernel pagetable layout to userspace via debugfs"
H. Peter Anvinfe770bf02008-04-17 17:40:45 +020071 depends on DEBUG_KERNEL
Arjan van de Ven926e5392008-04-17 17:40:45 +020072 select DEBUG_FS
Ingo Molnar8f9ca472009-02-05 16:21:53 +010073 ---help---
Arjan van de Ven926e5392008-04-17 17:40:45 +020074 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
Arjan van de Ven63aaf302006-01-06 00:12:02 -080081config DEBUG_RODATA
82 bool "Write protect kernel read-only data structures"
Ingo Molnar11201e62008-01-30 13:33:32 +010083 default y
Arjan van de Ven63aaf302006-01-06 00:12:02 -080084 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +010085 ---help---
Arjan van de Ven63aaf302006-01-06 00:12:02 -080086 Mark the kernel read-only data as write-protected in the pagetables,
87 in order to catch accidental (and incorrect) writes to such const
Ingo Molnar11201e62008-01-30 13:33:32 +010088 data. This is recommended so that we can catch kernel bugs sooner.
89 If in doubt, say "Y".
Arjan van de Ven63aaf302006-01-06 00:12:02 -080090
Ingo Molnaraba83912008-01-30 13:34:09 +010091config DEBUG_RODATA_TEST
92 bool "Testcase for the DEBUG_RODATA feature"
93 depends on DEBUG_RODATA
Ingo Molnar72370f22008-02-13 16:15:34 +010094 default y
Ingo Molnar8f9ca472009-02-05 16:21:53 +010095 ---help---
Ingo Molnaraba83912008-01-30 13:34:09 +010096 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
matthieu castet84e1c6b2010-11-16 22:35:16 +0100100config 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
Ingo Molnaraba83912008-01-30 13:34:09 +0100111config DEBUG_NX_TEST
112 tristate "Testcase for the NX non-executable stack feature"
113 depends on DEBUG_KERNEL && m
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100114 ---help---
Ingo Molnaraba83912008-01-30 13:34:09 +0100115 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
Andi Kleen102e41f2006-04-18 12:35:22 +0200119config DOUBLEFAULT
120 default y
David Rientjes6a108a12011-01-20 14:44:16 -0800121 bool "Enable doublefault exception handler" if EXPERT
Randy Dunlapd013a272007-10-24 15:50:43 -0700122 depends on X86_32
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100123 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700124 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"
Joerg Roedel966396d2007-10-24 12:49:48 +0200131 depends on GART_IOMMU && DEBUG_KERNEL
Randy Dunlapd013a272007-10-24 15:50:43 -0700132 depends on X86_64
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100133 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700134 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
Paul Bolle395cf962011-08-15 02:02:26 +0200142 options. See Documentation/x86/x86_64/boot-options.txt for more
Randy Dunlapd013a272007-10-24 15:50:43 -0700143 details.
144
Joerg Roedel2be69c72009-05-22 12:15:49 +0200145config 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
Randy Dunlapd013a272007-10-24 15:50:43 -0700153config IOMMU_LEAK
154 bool "IOMMU leak tracing"
FUJITA Tomonori19c1a6f2009-04-14 09:43:19 +0900155 depends on IOMMU_DEBUG && DMA_API_DEBUG
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100156 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700157 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
Pekka Paalanen6bc5c362009-01-03 21:23:51 +0200160config HAVE_MMIOTRACE_SUPPORT
161 def_bool y
Pekka Paalanen8b7d89d2008-05-12 21:20:56 +0200162
Masami Hiramatsuca0e9ba2009-08-13 16:34:21 -0400163config X86_DECODER_SELFTEST
OGAWA Hirofumicbe5c342009-12-06 20:14:29 +0900164 bool "x86 instruction decoder selftest"
165 depends on DEBUG_KERNEL && KPROBES
Masami Hiramatsuca0e9ba2009-08-13 16:34:21 -0400166 ---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
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100172#
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"
Ingo Molnarfd59e9e2008-02-17 20:20:24 +0100194 default IO_DELAY_0X80
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100195
196config IO_DELAY_0X80
197 bool "port 0x80 based port-IO delay [recommended]"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100198 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100199 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"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100204 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100205 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"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100210 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100211 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"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100216 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100217 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
Rene Hermanb02aae92008-01-30 13:30:05 +0100245
Huang, Ying6d7d7432008-01-30 13:32:51 +0100246config DEBUG_BOOT_PARAMS
247 bool "Debug boot parameters"
248 depends on DEBUG_KERNEL
249 depends on DEBUG_FS
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100250 ---help---
Huang, Ying6d7d7432008-01-30 13:32:51 +0100251 This option will cause struct boot_params to be exported via debugfs.
252
Andi Kleen0c42f392008-01-30 13:33:42 +0100253config CPA_DEBUG
Ingo Molnar971a52d2008-02-06 22:39:45 +0100254 bool "CPA self-test code"
Ingo Molnarf316fe62008-01-30 13:34:04 +0100255 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100256 ---help---
Ingo Molnar971a52d2008-02-06 22:39:45 +0100257 Do change_page_attr() self-tests every 30 seconds.
Andi Kleen0c42f392008-01-30 13:33:42 +0100258
Ingo Molnar60a3cdd2008-03-03 12:38:52 +0100259config OPTIMIZE_INLINING
260 bool "Allow gcc to uninline functions marked 'inline'"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100261 ---help---
Ingo Molnar60a3cdd2008-03-03 12:38:52 +0100262 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
Sitsofe Wheeler63fb7082008-10-11 20:27:53 +0100266 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.
Ingo Molnarc9af1e32008-04-30 08:48:45 +0200270
Ingo Molnar3f9b5cc2008-07-18 16:30:05 +0200271 If unsure, say N.
272
Arjan van de Ven63312b62009-10-02 07:50:50 -0700273config DEBUG_STRICT_USER_COPY_CHECKS
274 bool "Strict copy size checks"
Arjan van de Venad8f4352009-10-06 07:04:52 -0700275 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
Arjan van de Ven63312b62009-10-02 07:50:50 -0700276 ---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
Ingo Molnarc9af1e32008-04-30 08:48:45 +0200287endmenu