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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 X86_PTDUMP
70 bool "Export kernel pagetable layout to userspace via debugfs"
71 depends on DEBUG_KERNEL
72 select DEBUG_FS
73 ---help---
74 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
81config DEBUG_RODATA
82 bool "Write protect kernel read-only data structures"
83 default y
84 depends on DEBUG_KERNEL
85 ---help---
86 Mark the kernel read-only data as write-protected in the pagetables,
87 in order to catch accidental (and incorrect) writes to such const
88 data. This is recommended so that we can catch kernel bugs sooner.
89 If in doubt, say "Y".
90
91config DEBUG_RODATA_TEST
92 bool "Testcase for the DEBUG_RODATA feature"
93 depends on DEBUG_RODATA
94 default y
95 ---help---
96 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
100config 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
111config DEBUG_NX_TEST
112 tristate "Testcase for the NX non-executable stack feature"
113 depends on DEBUG_KERNEL && m
114 ---help---
115 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
119config DOUBLEFAULT
120 default y
121 bool "Enable doublefault exception handler" if EXPERT
122 depends on X86_32
123 ---help---
124 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"
131 depends on GART_IOMMU && DEBUG_KERNEL
132 depends on X86_64
133 ---help---
134 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
142 options. See Documentation/x86_64/boot-options.txt for more
143 details.
144
145config 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
153config IOMMU_LEAK
154 bool "IOMMU leak tracing"
155 depends on IOMMU_DEBUG && DMA_API_DEBUG
156 ---help---
157 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
160config HAVE_MMIOTRACE_SUPPORT
161 def_bool y
162
163config X86_DECODER_SELFTEST
164 bool "x86 instruction decoder selftest"
165 depends on DEBUG_KERNEL && KPROBES
166 ---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
172#
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"
194 default IO_DELAY_0X80
195
196config IO_DELAY_0X80
197 bool "port 0x80 based port-IO delay [recommended]"
198 ---help---
199 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"
204 ---help---
205 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"
210 ---help---
211 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"
216 ---help---
217 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
245
246config DEBUG_BOOT_PARAMS
247 bool "Debug boot parameters"
248 depends on DEBUG_KERNEL
249 depends on DEBUG_FS
250 ---help---
251 This option will cause struct boot_params to be exported via debugfs.
252
253config CPA_DEBUG
254 bool "CPA self-test code"
255 depends on DEBUG_KERNEL
256 ---help---
257 Do change_page_attr() self-tests every 30 seconds.
258
259config OPTIMIZE_INLINING
260 bool "Allow gcc to uninline functions marked 'inline'"
261 ---help---
262 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
266 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.
270
271 If unsure, say N.
272
273config DEBUG_STRICT_USER_COPY_CHECKS
274 bool "Strict copy size checks"
275 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
276 ---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
287endmenu
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