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_DBGP
47	bool "Early printk via EHCI debug port"
48	depends on EARLY_PRINTK && PCI
49	---help---
50	  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
58config EARLY_PRINTK_EFI
59	bool "Early printk via the EFI framebuffer"
60	depends on EFI && EARLY_PRINTK
61	select FONT_SUPPORT
62	---help---
63	  Write kernel log output directly into the EFI framebuffer.
64
65	  This is useful for kernel debugging when your machine crashes very
66	  early before the console code is initialized.
67
68config X86_PTDUMP
69	bool "Export kernel pagetable layout to userspace via debugfs"
70	depends on DEBUG_KERNEL
71	select DEBUG_FS
72	---help---
73	  Say Y here if you want to show the kernel pagetable layout in a
74	  debugfs file. This information is only useful for kernel developers
75	  who are working in architecture specific areas of the kernel.
76	  It is probably not a good idea to enable this feature in a production
77	  kernel.
78	  If in doubt, say "N"
79
80config EFI_PGT_DUMP
81	bool "Dump the EFI pagetable"
82	depends on EFI && X86_PTDUMP
83	---help---
84	  Enable this if you want to dump the EFI page table before
85	  enabling virtual mode. This can be used to debug miscellaneous
86	  issues with the mapping of the EFI runtime regions into that
87	  table.
88
89config DEBUG_RODATA
90	bool "Write protect kernel read-only data structures"
91	default y
92	depends on DEBUG_KERNEL
93	---help---
94	  Mark the kernel read-only data as write-protected in the pagetables,
95	  in order to catch accidental (and incorrect) writes to such const
96	  data. This is recommended so that we can catch kernel bugs sooner.
97	  If in doubt, say "Y".
98
99config DEBUG_RODATA_TEST
100	bool "Testcase for the DEBUG_RODATA feature"
101	depends on DEBUG_RODATA
102	default y
103	---help---
104	  This option enables a testcase for the DEBUG_RODATA
105	  feature as well as for the change_page_attr() infrastructure.
106	  If in doubt, say "N"
107
108config DEBUG_SET_MODULE_RONX
109	bool "Set loadable kernel module data as NX and text as RO"
110	depends on MODULES
111	---help---
112	  This option helps catch unintended modifications to loadable
113	  kernel module's text and read-only data. It also prevents execution
114	  of module data. Such protection may interfere with run-time code
115	  patching and dynamic kernel tracing - and they might also protect
116	  against certain classes of kernel exploits.
117	  If in doubt, say "N".
118
119config DEBUG_NX_TEST
120	tristate "Testcase for the NX non-executable stack feature"
121	depends on DEBUG_KERNEL && m
122	---help---
123	  This option enables a testcase for the CPU NX capability
124	  and the software setup of this feature.
125	  If in doubt, say "N"
126
127config DOUBLEFAULT
128	default y
129	bool "Enable doublefault exception handler" if EXPERT
130	---help---
131	  This option allows trapping of rare doublefault exceptions that
132	  would otherwise cause a system to silently reboot. Disabling this
133	  option saves about 4k and might cause you much additional grey
134	  hair.
135
136config DEBUG_TLBFLUSH
137	bool "Set upper limit of TLB entries to flush one-by-one"
138	depends on DEBUG_KERNEL
139	---help---
140
141	X86-only for now.
142
143	This option allows the user to tune the amount of TLB entries the
144	kernel flushes one-by-one instead of doing a full TLB flush. In
145	certain situations, the former is cheaper. This is controlled by the
146	tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
147	to -1, the code flushes the whole TLB unconditionally. Otherwise,
148	for positive values of it, the kernel will use single TLB entry
149	invalidating instructions according to the following formula:
150
151	flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
152
153	If in doubt, say "N".
154
155config IOMMU_DEBUG
156	bool "Enable IOMMU debugging"
157	depends on GART_IOMMU && DEBUG_KERNEL
158	depends on X86_64
159	---help---
160	  Force the IOMMU to on even when you have less than 4GB of
161	  memory and add debugging code. On overflow always panic. And
162	  allow to enable IOMMU leak tracing. Can be disabled at boot
163	  time with iommu=noforce. This will also enable scatter gather
164	  list merging.  Currently not recommended for production
165	  code. When you use it make sure you have a big enough
166	  IOMMU/AGP aperture.  Most of the options enabled by this can
167	  be set more finegrained using the iommu= command line
168	  options. See Documentation/x86/x86_64/boot-options.txt for more
169	  details.
170
171config IOMMU_STRESS
172	bool "Enable IOMMU stress-test mode"
173	---help---
174	  This option disables various optimizations in IOMMU related
175	  code to do real stress testing of the IOMMU code. This option
176	  will cause a performance drop and should only be enabled for
177	  testing.
178
179config IOMMU_LEAK
180	bool "IOMMU leak tracing"
181	depends on IOMMU_DEBUG && DMA_API_DEBUG
182	---help---
183	  Add a simple leak tracer to the IOMMU code. This is useful when you
184	  are debugging a buggy device driver that leaks IOMMU mappings.
185
186config HAVE_MMIOTRACE_SUPPORT
187	def_bool y
188
189config X86_DECODER_SELFTEST
190	bool "x86 instruction decoder selftest"
191	depends on DEBUG_KERNEL && KPROBES
192	depends on !COMPILE_TEST
193	---help---
194	 Perform x86 instruction decoder selftests at build time.
195	 This option is useful for checking the sanity of x86 instruction
196	 decoder code.
197	 If unsure, say "N".
198
199#
200# IO delay types:
201#
202
203config IO_DELAY_TYPE_0X80
204	int
205	default "0"
206
207config IO_DELAY_TYPE_0XED
208	int
209	default "1"
210
211config IO_DELAY_TYPE_UDELAY
212	int
213	default "2"
214
215config IO_DELAY_TYPE_NONE
216	int
217	default "3"
218
219choice
220	prompt "IO delay type"
221	default IO_DELAY_0X80
222
223config IO_DELAY_0X80
224	bool "port 0x80 based port-IO delay [recommended]"
225	---help---
226	  This is the traditional Linux IO delay used for in/out_p.
227	  It is the most tested hence safest selection here.
228
229config IO_DELAY_0XED
230	bool "port 0xed based port-IO delay"
231	---help---
232	  Use port 0xed as the IO delay. This frees up port 0x80 which is
233	  often used as a hardware-debug port.
234
235config IO_DELAY_UDELAY
236	bool "udelay based port-IO delay"
237	---help---
238	  Use udelay(2) as the IO delay method. This provides the delay
239	  while not having any side-effect on the IO port space.
240
241config IO_DELAY_NONE
242	bool "no port-IO delay"
243	---help---
244	  No port-IO delay. Will break on old boxes that require port-IO
245	  delay for certain operations. Should work on most new machines.
246
247endchoice
248
249if IO_DELAY_0X80
250config DEFAULT_IO_DELAY_TYPE
251	int
252	default IO_DELAY_TYPE_0X80
253endif
254
255if IO_DELAY_0XED
256config DEFAULT_IO_DELAY_TYPE
257	int
258	default IO_DELAY_TYPE_0XED
259endif
260
261if IO_DELAY_UDELAY
262config DEFAULT_IO_DELAY_TYPE
263	int
264	default IO_DELAY_TYPE_UDELAY
265endif
266
267if IO_DELAY_NONE
268config DEFAULT_IO_DELAY_TYPE
269	int
270	default IO_DELAY_TYPE_NONE
271endif
272
273config DEBUG_BOOT_PARAMS
274	bool "Debug boot parameters"
275	depends on DEBUG_KERNEL
276	depends on DEBUG_FS
277	---help---
278	  This option will cause struct boot_params to be exported via debugfs.
279
280config CPA_DEBUG
281	bool "CPA self-test code"
282	depends on DEBUG_KERNEL
283	---help---
284	  Do change_page_attr() self-tests every 30 seconds.
285
286config OPTIMIZE_INLINING
287	bool "Allow gcc to uninline functions marked 'inline'"
288	---help---
289	  This option determines if the kernel forces gcc to inline the functions
290	  developers have marked 'inline'. Doing so takes away freedom from gcc to
291	  do what it thinks is best, which is desirable for the gcc 3.x series of
292	  compilers. The gcc 4.x series have a rewritten inlining algorithm and
293	  enabling this option will generate a smaller kernel there. Hopefully
294	  this algorithm is so good that allowing gcc 4.x and above to make the
295	  decision will become the default in the future. Until then this option
296	  is there to test gcc for this.
297
298	  If unsure, say N.
299
300config DEBUG_NMI_SELFTEST
301	bool "NMI Selftest"
302	depends on DEBUG_KERNEL && X86_LOCAL_APIC
303	---help---
304	  Enabling this option turns on a quick NMI selftest to verify
305	  that the NMI behaves correctly.
306
307	  This might help diagnose strange hangs that rely on NMI to
308	  function properly.
309
310	  If unsure, say N.
311
312config DEBUG_IMR_SELFTEST
313	bool "Isolated Memory Region self test"
314	default n
315	depends on INTEL_IMR
316	---help---
317	  This option enables automated sanity testing of the IMR code.
318	  Some simple tests are run to verify IMR bounds checking, alignment
319	  and overlapping. This option is really only useful if you are
320	  debugging an IMR memory map or are modifying the IMR code and want to
321	  test your changes.
322
323	  If unsure say N here.
324
325config X86_DEBUG_STATIC_CPU_HAS
326	bool "Debug alternatives"
327	depends on DEBUG_KERNEL
328	---help---
329	  This option causes additional code to be generated which
330	  fails if static_cpu_has() is used before alternatives have
331	  run.
332
333	  If unsure, say N.
334
335endmenu
336