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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
Ingo Molnar076f9772008-01-30 13:33:06 +010034 bool "Early printk" if EMBEDDED
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
Yinghai Lu5c059172008-07-24 17:29:40 -070046config EARLY_PRINTK_DBGP
47 bool "Early printk via EHCI debug port"
Ingo Molnar97499862008-07-26 17:28:11 +020048 depends on EARLY_PRINTK && PCI
Ingo Molnar8f9ca472009-02-05 16:21:53 +010049 ---help---
Yinghai Lu5c059172008-07-24 17:29:40 -070050 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070058config DEBUG_STACKOVERFLOW
59 bool "Check for stack overflows"
60 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +010061 ---help---
Adrian Bunkdab175f2005-07-27 11:44:23 -070062 This option will cause messages to be printed if free stack space
63 drops below a certain limit.
Linus Torvalds1da177e2005-04-16 15:20:36 -070064
Linus Torvalds1da177e2005-04-16 15:20:36 -070065config DEBUG_STACK_USAGE
66 bool "Stack utilization instrumentation"
67 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +010068 ---help---
Linus Torvalds1da177e2005-04-16 15:20:36 -070069 Enables the display of the minimum amount of free stack which each
70 task has ever had available in the sysrq-T and sysrq-P debug output.
71
72 This option will slow down process creation somewhat.
73
travis@sgi.comc49a4952008-01-30 13:33:22 +010074config DEBUG_PER_CPU_MAPS
75 bool "Debug access to per_cpu maps"
76 depends on DEBUG_KERNEL
Ingo Molnar3e5095d2009-01-27 17:07:08 +010077 depends on SMP
Ingo Molnar8f9ca472009-02-05 16:21:53 +010078 ---help---
travis@sgi.comc49a4952008-01-30 13:33:22 +010079 Say Y to verify that the per_cpu map being accessed has
80 been setup. Adds a fair amount of code to kernel memory
81 and decreases performance.
82
83 Say N if unsure.
84
Arjan van de Ven926e5392008-04-17 17:40:45 +020085config X86_PTDUMP
86 bool "Export kernel pagetable layout to userspace via debugfs"
H. Peter Anvinfe770bf02008-04-17 17:40:45 +020087 depends on DEBUG_KERNEL
Arjan van de Ven926e5392008-04-17 17:40:45 +020088 select DEBUG_FS
Ingo Molnar8f9ca472009-02-05 16:21:53 +010089 ---help---
Arjan van de Ven926e5392008-04-17 17:40:45 +020090 Say Y here if you want to show the kernel pagetable layout in a
91 debugfs file. This information is only useful for kernel developers
92 who are working in architecture specific areas of the kernel.
93 It is probably not a good idea to enable this feature in a production
94 kernel.
95 If in doubt, say "N"
96
Arjan van de Ven63aaf302006-01-06 00:12:02 -080097config DEBUG_RODATA
98 bool "Write protect kernel read-only data structures"
Ingo Molnar11201e62008-01-30 13:33:32 +010099 default y
Arjan van de Ven63aaf302006-01-06 00:12:02 -0800100 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100101 ---help---
Arjan van de Ven63aaf302006-01-06 00:12:02 -0800102 Mark the kernel read-only data as write-protected in the pagetables,
103 in order to catch accidental (and incorrect) writes to such const
Ingo Molnar11201e62008-01-30 13:33:32 +0100104 data. This is recommended so that we can catch kernel bugs sooner.
105 If in doubt, say "Y".
Arjan van de Ven63aaf302006-01-06 00:12:02 -0800106
Ingo Molnaraba83912008-01-30 13:34:09 +0100107config DEBUG_RODATA_TEST
108 bool "Testcase for the DEBUG_RODATA feature"
109 depends on DEBUG_RODATA
Ingo Molnar72370f22008-02-13 16:15:34 +0100110 default y
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100111 ---help---
Ingo Molnaraba83912008-01-30 13:34:09 +0100112 This option enables a testcase for the DEBUG_RODATA
113 feature as well as for the change_page_attr() infrastructure.
114 If in doubt, say "N"
115
116config DEBUG_NX_TEST
117 tristate "Testcase for the NX non-executable stack feature"
118 depends on DEBUG_KERNEL && m
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100119 ---help---
Ingo Molnaraba83912008-01-30 13:34:09 +0100120 This option enables a testcase for the CPU NX capability
121 and the software setup of this feature.
122 If in doubt, say "N"
123
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124config 4KSTACKS
125 bool "Use 4Kb for kernel stacks instead of 8Kb"
Randy Dunlapd013a272007-10-24 15:50:43 -0700126 depends on X86_32
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100127 ---help---
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128 If you say Y here the kernel will use a 4Kb stacksize for the
129 kernel stack attached to each process/thread. This facilitates
130 running more threads on a system and also reduces the pressure
131 on the VM subsystem for higher order allocations. This option
132 will also use IRQ stacks to compensate for the reduced stackspace.
133
Andi Kleen102e41f2006-04-18 12:35:22 +0200134config DOUBLEFAULT
135 default y
136 bool "Enable doublefault exception handler" if EMBEDDED
Randy Dunlapd013a272007-10-24 15:50:43 -0700137 depends on X86_32
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100138 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700139 This option allows trapping of rare doublefault exceptions that
140 would otherwise cause a system to silently reboot. Disabling this
141 option saves about 4k and might cause you much additional grey
142 hair.
143
144config IOMMU_DEBUG
145 bool "Enable IOMMU debugging"
Joerg Roedel966396d2007-10-24 12:49:48 +0200146 depends on GART_IOMMU && DEBUG_KERNEL
Randy Dunlapd013a272007-10-24 15:50:43 -0700147 depends on X86_64
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100148 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700149 Force the IOMMU to on even when you have less than 4GB of
150 memory and add debugging code. On overflow always panic. And
151 allow to enable IOMMU leak tracing. Can be disabled at boot
152 time with iommu=noforce. This will also enable scatter gather
153 list merging. Currently not recommended for production
154 code. When you use it make sure you have a big enough
155 IOMMU/AGP aperture. Most of the options enabled by this can
156 be set more finegrained using the iommu= command line
157 options. See Documentation/x86_64/boot-options.txt for more
158 details.
159
Joerg Roedel2be69c72009-05-22 12:15:49 +0200160config IOMMU_STRESS
161 bool "Enable IOMMU stress-test mode"
162 ---help---
163 This option disables various optimizations in IOMMU related
164 code to do real stress testing of the IOMMU code. This option
165 will cause a performance drop and should only be enabled for
166 testing.
167
Randy Dunlapd013a272007-10-24 15:50:43 -0700168config IOMMU_LEAK
169 bool "IOMMU leak tracing"
FUJITA Tomonori19c1a6f2009-04-14 09:43:19 +0900170 depends on IOMMU_DEBUG && DMA_API_DEBUG
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100171 ---help---
Randy Dunlapd013a272007-10-24 15:50:43 -0700172 Add a simple leak tracer to the IOMMU code. This is useful when you
173 are debugging a buggy device driver that leaks IOMMU mappings.
174
Pekka Paalanen6bc5c362009-01-03 21:23:51 +0200175config HAVE_MMIOTRACE_SUPPORT
176 def_bool y
Pekka Paalanen8b7d89d2008-05-12 21:20:56 +0200177
Masami Hiramatsuca0e9ba2009-08-13 16:34:21 -0400178config X86_DECODER_SELFTEST
OGAWA Hirofumicbe5c342009-12-06 20:14:29 +0900179 bool "x86 instruction decoder selftest"
180 depends on DEBUG_KERNEL && KPROBES
Masami Hiramatsuca0e9ba2009-08-13 16:34:21 -0400181 ---help---
182 Perform x86 instruction decoder selftests at build time.
183 This option is useful for checking the sanity of x86 instruction
184 decoder code.
185 If unsure, say "N".
186
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100187#
188# IO delay types:
189#
190
191config IO_DELAY_TYPE_0X80
192 int
193 default "0"
194
195config IO_DELAY_TYPE_0XED
196 int
197 default "1"
198
199config IO_DELAY_TYPE_UDELAY
200 int
201 default "2"
202
203config IO_DELAY_TYPE_NONE
204 int
205 default "3"
206
207choice
208 prompt "IO delay type"
Ingo Molnarfd59e9e2008-02-17 20:20:24 +0100209 default IO_DELAY_0X80
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100210
211config IO_DELAY_0X80
212 bool "port 0x80 based port-IO delay [recommended]"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100213 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100214 This is the traditional Linux IO delay used for in/out_p.
215 It is the most tested hence safest selection here.
216
217config IO_DELAY_0XED
218 bool "port 0xed based port-IO delay"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100219 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100220 Use port 0xed as the IO delay. This frees up port 0x80 which is
221 often used as a hardware-debug port.
222
223config IO_DELAY_UDELAY
224 bool "udelay based port-IO delay"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100225 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100226 Use udelay(2) as the IO delay method. This provides the delay
227 while not having any side-effect on the IO port space.
228
229config IO_DELAY_NONE
230 bool "no port-IO delay"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100231 ---help---
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100232 No port-IO delay. Will break on old boxes that require port-IO
233 delay for certain operations. Should work on most new machines.
234
235endchoice
236
237if IO_DELAY_0X80
238config DEFAULT_IO_DELAY_TYPE
239 int
240 default IO_DELAY_TYPE_0X80
241endif
242
243if IO_DELAY_0XED
244config DEFAULT_IO_DELAY_TYPE
245 int
246 default IO_DELAY_TYPE_0XED
247endif
248
249if IO_DELAY_UDELAY
250config DEFAULT_IO_DELAY_TYPE
251 int
252 default IO_DELAY_TYPE_UDELAY
253endif
254
255if IO_DELAY_NONE
256config DEFAULT_IO_DELAY_TYPE
257 int
258 default IO_DELAY_TYPE_NONE
259endif
Rene Hermanb02aae92008-01-30 13:30:05 +0100260
Huang, Ying6d7d7432008-01-30 13:32:51 +0100261config DEBUG_BOOT_PARAMS
262 bool "Debug boot parameters"
263 depends on DEBUG_KERNEL
264 depends on DEBUG_FS
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100265 ---help---
Huang, Ying6d7d7432008-01-30 13:32:51 +0100266 This option will cause struct boot_params to be exported via debugfs.
267
Andi Kleen0c42f392008-01-30 13:33:42 +0100268config CPA_DEBUG
Ingo Molnar971a52d2008-02-06 22:39:45 +0100269 bool "CPA self-test code"
Ingo Molnarf316fe62008-01-30 13:34:04 +0100270 depends on DEBUG_KERNEL
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100271 ---help---
Ingo Molnar971a52d2008-02-06 22:39:45 +0100272 Do change_page_attr() self-tests every 30 seconds.
Andi Kleen0c42f392008-01-30 13:33:42 +0100273
Ingo Molnar60a3cdd2008-03-03 12:38:52 +0100274config OPTIMIZE_INLINING
275 bool "Allow gcc to uninline functions marked 'inline'"
Ingo Molnar8f9ca472009-02-05 16:21:53 +0100276 ---help---
Ingo Molnar60a3cdd2008-03-03 12:38:52 +0100277 This option determines if the kernel forces gcc to inline the functions
278 developers have marked 'inline'. Doing so takes away freedom from gcc to
279 do what it thinks is best, which is desirable for the gcc 3.x series of
280 compilers. The gcc 4.x series have a rewritten inlining algorithm and
Sitsofe Wheeler63fb7082008-10-11 20:27:53 +0100281 enabling this option will generate a smaller kernel there. Hopefully
282 this algorithm is so good that allowing gcc 4.x and above to make the
283 decision will become the default in the future. Until then this option
284 is there to test gcc for this.
Ingo Molnarc9af1e32008-04-30 08:48:45 +0200285
Ingo Molnar3f9b5cc2008-07-18 16:30:05 +0200286 If unsure, say N.
287
Arjan van de Ven63312b62009-10-02 07:50:50 -0700288config DEBUG_STRICT_USER_COPY_CHECKS
289 bool "Strict copy size checks"
Arjan van de Venad8f4352009-10-06 07:04:52 -0700290 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
Arjan van de Ven63312b62009-10-02 07:50:50 -0700291 ---help---
292 Enabling this option turns a certain set of sanity checks for user
293 copy operations into compile time failures.
294
295 The copy_from_user() etc checks are there to help test if there
296 are sufficient security checks on the length argument of
297 the copy operation, by having gcc prove that the argument is
298 within bounds.
299
300 If unsure, or if you run an older (pre 4.4) gcc, say N.
301
Ingo Molnarc9af1e32008-04-30 08:48:45 +0200302endmenu