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