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_INTEL_MID
47	bool "Early printk for Intel MID platform support"
48	depends on EARLY_PRINTK && X86_INTEL_MID
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	  Say Y here if you want to check the overflows of kernel, IRQ
67	  and exception stacks. This option will cause messages of the
68	  stacks in detail when free stack space drops below a certain
69	  limit.
70	  If in doubt, say "N".
71
72config X86_PTDUMP
73	bool "Export kernel pagetable layout to userspace via debugfs"
74	depends on DEBUG_KERNEL
75	select DEBUG_FS
76	---help---
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
84config DEBUG_RODATA
85	bool "Write protect kernel read-only data structures"
86	default y
87	depends on DEBUG_KERNEL
88	---help---
89	  Mark the kernel read-only data as write-protected in the pagetables,
90	  in order to catch accidental (and incorrect) writes to such const
91	  data. This is recommended so that we can catch kernel bugs sooner.
92	  If in doubt, say "Y".
93
94config DEBUG_RODATA_TEST
95	bool "Testcase for the DEBUG_RODATA feature"
96	depends on DEBUG_RODATA
97	default y
98	---help---
99	  This option enables a testcase for the DEBUG_RODATA
100	  feature as well as for the change_page_attr() infrastructure.
101	  If in doubt, say "N"
102
103config DEBUG_SET_MODULE_RONX
104	bool "Set loadable kernel module data as NX and text as RO"
105	depends on MODULES
106	---help---
107	  This option helps catch unintended modifications to loadable
108	  kernel module's text and read-only data. It also prevents execution
109	  of module data. Such protection may interfere with run-time code
110	  patching and dynamic kernel tracing - and they might also protect
111	  against certain classes of kernel exploits.
112	  If in doubt, say "N".
113
114config DEBUG_NX_TEST
115	tristate "Testcase for the NX non-executable stack feature"
116	depends on DEBUG_KERNEL && m
117	---help---
118	  This option enables a testcase for the CPU NX capability
119	  and the software setup of this feature.
120	  If in doubt, say "N"
121
122config DOUBLEFAULT
123	default y
124	bool "Enable doublefault exception handler" if EXPERT
125	depends on X86_32
126	---help---
127	  This option allows trapping of rare doublefault exceptions that
128	  would otherwise cause a system to silently reboot. Disabling this
129	  option saves about 4k and might cause you much additional grey
130	  hair.
131
132config IOMMU_DEBUG
133	bool "Enable IOMMU debugging"
134	depends on GART_IOMMU && DEBUG_KERNEL
135	depends on X86_64
136	---help---
137	  Force the IOMMU to on even when you have less than 4GB of
138	  memory and add debugging code. On overflow always panic. And
139	  allow to enable IOMMU leak tracing. Can be disabled at boot
140	  time with iommu=noforce. This will also enable scatter gather
141	  list merging.  Currently not recommended for production
142	  code. When you use it make sure you have a big enough
143	  IOMMU/AGP aperture.  Most of the options enabled by this can
144	  be set more finegrained using the iommu= command line
145	  options. See Documentation/x86/x86_64/boot-options.txt for more
146	  details.
147
148config IOMMU_STRESS
149	bool "Enable IOMMU stress-test mode"
150	---help---
151	  This option disables various optimizations in IOMMU related
152	  code to do real stress testing of the IOMMU code. This option
153	  will cause a performance drop and should only be enabled for
154	  testing.
155
156config IOMMU_LEAK
157	bool "IOMMU leak tracing"
158	depends on IOMMU_DEBUG && DMA_API_DEBUG
159	---help---
160	  Add a simple leak tracer to the IOMMU code. This is useful when you
161	  are debugging a buggy device driver that leaks IOMMU mappings.
162
163config HAVE_MMIOTRACE_SUPPORT
164	def_bool y
165
166config X86_DECODER_SELFTEST
167	bool "x86 instruction decoder selftest"
168	depends on DEBUG_KERNEL && KPROBES
169	---help---
170	 Perform x86 instruction decoder selftests at build time.
171	 This option is useful for checking the sanity of x86 instruction
172	 decoder code.
173	 If unsure, say "N".
174
175#
176# IO delay types:
177#
178
179config IO_DELAY_TYPE_0X80
180	int
181	default "0"
182
183config IO_DELAY_TYPE_0XED
184	int
185	default "1"
186
187config IO_DELAY_TYPE_UDELAY
188	int
189	default "2"
190
191config IO_DELAY_TYPE_NONE
192	int
193	default "3"
194
195choice
196	prompt "IO delay type"
197	default IO_DELAY_0X80
198
199config IO_DELAY_0X80
200	bool "port 0x80 based port-IO delay [recommended]"
201	---help---
202	  This is the traditional Linux IO delay used for in/out_p.
203	  It is the most tested hence safest selection here.
204
205config IO_DELAY_0XED
206	bool "port 0xed based port-IO delay"
207	---help---
208	  Use port 0xed as the IO delay. This frees up port 0x80 which is
209	  often used as a hardware-debug port.
210
211config IO_DELAY_UDELAY
212	bool "udelay based port-IO delay"
213	---help---
214	  Use udelay(2) as the IO delay method. This provides the delay
215	  while not having any side-effect on the IO port space.
216
217config IO_DELAY_NONE
218	bool "no port-IO delay"
219	---help---
220	  No port-IO delay. Will break on old boxes that require port-IO
221	  delay for certain operations. Should work on most new machines.
222
223endchoice
224
225if IO_DELAY_0X80
226config DEFAULT_IO_DELAY_TYPE
227	int
228	default IO_DELAY_TYPE_0X80
229endif
230
231if IO_DELAY_0XED
232config DEFAULT_IO_DELAY_TYPE
233	int
234	default IO_DELAY_TYPE_0XED
235endif
236
237if IO_DELAY_UDELAY
238config DEFAULT_IO_DELAY_TYPE
239	int
240	default IO_DELAY_TYPE_UDELAY
241endif
242
243if IO_DELAY_NONE
244config DEFAULT_IO_DELAY_TYPE
245	int
246	default IO_DELAY_TYPE_NONE
247endif
248
249config DEBUG_BOOT_PARAMS
250	bool "Debug boot parameters"
251	depends on DEBUG_KERNEL
252	depends on DEBUG_FS
253	---help---
254	  This option will cause struct boot_params to be exported via debugfs.
255
256config CPA_DEBUG
257	bool "CPA self-test code"
258	depends on DEBUG_KERNEL
259	---help---
260	  Do change_page_attr() self-tests every 30 seconds.
261
262config OPTIMIZE_INLINING
263	bool "Allow gcc to uninline functions marked 'inline'"
264	---help---
265	  This option determines if the kernel forces gcc to inline the functions
266	  developers have marked 'inline'. Doing so takes away freedom from gcc to
267	  do what it thinks is best, which is desirable for the gcc 3.x series of
268	  compilers. The gcc 4.x series have a rewritten inlining algorithm and
269	  enabling this option will generate a smaller kernel there. Hopefully
270	  this algorithm is so good that allowing gcc 4.x and above to make the
271	  decision will become the default in the future. Until then this option
272	  is there to test gcc for this.
273
274	  If unsure, say N.
275
276config DEBUG_STRICT_USER_COPY_CHECKS
277	bool "Strict copy size checks"
278	depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
279	---help---
280	  Enabling this option turns a certain set of sanity checks for user
281	  copy operations into compile time failures.
282
283	  The copy_from_user() etc checks are there to help test if there
284	  are sufficient security checks on the length argument of
285	  the copy operation, by having gcc prove that the argument is
286	  within bounds.
287
288	  If unsure, or if you run an older (pre 4.4) gcc, say N.
289
290config DEBUG_NMI_SELFTEST
291	bool "NMI Selftest"
292	depends on DEBUG_KERNEL && X86_LOCAL_APIC
293	---help---
294	  Enabling this option turns on a quick NMI selftest to verify
295	  that the NMI behaves correctly.
296
297	  This might help diagnose strange hangs that rely on NMI to
298	  function properly.
299
300	  If unsure, say N.
301
302endmenu
303