1menu "Kernel hacking"
2
3config TRACE_IRQFLAGS_SUPPORT
4	def_bool y
5
6source "lib/Kconfig.debug"
7
8config STRICT_DEVMEM
9	bool "Filter access to /dev/mem"
10	---help---
11	  If this option is disabled, you allow userspace (root) access to all
12	  of memory, including kernel and userspace memory. Accidental
13	  access to this is obviously disastrous, but specific access can
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.
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.
24
25config X86_VERBOSE_BOOTUP
26	bool "Enable verbose x86 bootup info messages"
27	default y
28	---help---
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
33config EARLY_PRINTK
34	bool "Early printk" if EXPERT
35	default y
36	---help---
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
46config EARLY_PRINTK_MRST
47	bool "Early printk for MRST platform support"
48	depends on EARLY_PRINTK && X86_MRST
49
50config EARLY_PRINTK_DBGP
51	bool "Early printk via EHCI debug port"
52	depends on EARLY_PRINTK && PCI
53	---help---
54	  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
62config DEBUG_STACKOVERFLOW
63	bool "Check for stack overflows"
64	depends on DEBUG_KERNEL
65	---help---
66	  This option will cause messages to be printed if free stack space
67	  drops below a certain limit.
68
69config DEBUG_STACK_USAGE
70	bool "Stack utilization instrumentation"
71	depends on DEBUG_KERNEL
72	---help---
73	  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
78config DEBUG_PER_CPU_MAPS
79	bool "Debug access to per_cpu maps"
80	depends on DEBUG_KERNEL
81	depends on SMP
82	---help---
83	  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
89config X86_PTDUMP
90	bool "Export kernel pagetable layout to userspace via debugfs"
91	depends on DEBUG_KERNEL
92	select DEBUG_FS
93	---help---
94	  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
101config DEBUG_RODATA
102	bool "Write protect kernel read-only data structures"
103	default y
104	depends on DEBUG_KERNEL
105	---help---
106	  Mark the kernel read-only data as write-protected in the pagetables,
107	  in order to catch accidental (and incorrect) writes to such const
108	  data. This is recommended so that we can catch kernel bugs sooner.
109	  If in doubt, say "Y".
110
111config DEBUG_RODATA_TEST
112	bool "Testcase for the DEBUG_RODATA feature"
113	depends on DEBUG_RODATA
114	default y
115	---help---
116	  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
120config 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
131config DEBUG_NX_TEST
132	tristate "Testcase for the NX non-executable stack feature"
133	depends on DEBUG_KERNEL && m
134	---help---
135	  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
139config DOUBLEFAULT
140	default y
141	bool "Enable doublefault exception handler" if EXPERT
142	depends on X86_32
143	---help---
144	  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"
151	depends on GART_IOMMU && DEBUG_KERNEL
152	depends on X86_64
153	---help---
154	  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
165config 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
173config IOMMU_LEAK
174	bool "IOMMU leak tracing"
175	depends on IOMMU_DEBUG && DMA_API_DEBUG
176	---help---
177	  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
180config HAVE_MMIOTRACE_SUPPORT
181	def_bool y
182
183config X86_DECODER_SELFTEST
184	bool "x86 instruction decoder selftest"
185	depends on DEBUG_KERNEL && KPROBES
186	---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
192#
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"
214	default IO_DELAY_0X80
215
216config IO_DELAY_0X80
217	bool "port 0x80 based port-IO delay [recommended]"
218	---help---
219	  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"
224	---help---
225	  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"
230	---help---
231	  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"
236	---help---
237	  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
265
266config DEBUG_BOOT_PARAMS
267	bool "Debug boot parameters"
268	depends on DEBUG_KERNEL
269	depends on DEBUG_FS
270	---help---
271	  This option will cause struct boot_params to be exported via debugfs.
272
273config CPA_DEBUG
274	bool "CPA self-test code"
275	depends on DEBUG_KERNEL
276	---help---
277	  Do change_page_attr() self-tests every 30 seconds.
278
279config OPTIMIZE_INLINING
280	bool "Allow gcc to uninline functions marked 'inline'"
281	---help---
282	  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
286	  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.
290
291	  If unsure, say N.
292
293config DEBUG_STRICT_USER_COPY_CHECKS
294	bool "Strict copy size checks"
295	depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
296	---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
307endmenu
308