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1da177e4 LT |
1 | menu "Kernel hacking" |
2 | ||
55f327fa | 3 | config TRACE_IRQFLAGS_SUPPORT |
d013a27c | 4 | def_bool y |
55f327fa | 5 | |
1da177e4 LT |
6 | source "lib/Kconfig.debug" |
7 | ||
d092633b | 8 | config STRICT_DEVMEM |
16104b55 | 9 | bool "Filter access to /dev/mem" |
ae531c26 | 10 | help |
f2d0f1de | 11 | If this option is disabled, you allow userspace (root) access to all |
16104b55 SR |
12 | of memory, including kernel and userspace memory. Accidental |
13 | access to this is obviously disastrous, but specific access can | |
d092633b IM |
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. | |
16104b55 SR |
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. | |
ae531c26 | 24 | |
6bcb13b3 BC |
25 | config 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 | ||
1da177e4 | 33 | config EARLY_PRINTK |
076f9776 | 34 | bool "Early printk" if EMBEDDED |
1da177e4 LT |
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 | ||
5c05917e YL |
46 | config EARLY_PRINTK_DBGP |
47 | bool "Early printk via EHCI debug port" | |
48 | default n | |
9749986a | 49 | depends on EARLY_PRINTK && PCI |
5c05917e YL |
50 | help |
51 | Write kernel log output directly into the EHCI debug port. | |
52 | ||
53 | This is useful for kernel debugging when your machine crashes very | |
54 | early before the console code is initialized. For normal operation | |
55 | it is not recommended because it looks ugly and doesn't cooperate | |
56 | with klogd/syslogd or the X server. You should normally N here, | |
57 | unless you want to debug such a crash. You need usb debug device. | |
58 | ||
1da177e4 LT |
59 | config DEBUG_STACKOVERFLOW |
60 | bool "Check for stack overflows" | |
61 | depends on DEBUG_KERNEL | |
dab175f3 AB |
62 | help |
63 | This option will cause messages to be printed if free stack space | |
64 | drops below a certain limit. | |
1da177e4 | 65 | |
1da177e4 LT |
66 | config DEBUG_STACK_USAGE |
67 | bool "Stack utilization instrumentation" | |
68 | depends on DEBUG_KERNEL | |
69 | help | |
70 | Enables the display of the minimum amount of free stack which each | |
71 | task has ever had available in the sysrq-T and sysrq-P debug output. | |
72 | ||
73 | This option will slow down process creation somewhat. | |
74 | ||
1da177e4 | 75 | config DEBUG_PAGEALLOC |
4a2f0acf | 76 | bool "Debug page memory allocations" |
b1d95f4e | 77 | depends on DEBUG_KERNEL |
1da177e4 LT |
78 | help |
79 | Unmap pages from the kernel linear mapping after free_pages(). | |
80 | This results in a large slowdown, but helps to find certain types | |
81 | of memory corruptions. | |
82 | ||
c49a4955 | 83 | config DEBUG_PER_CPU_MAPS |
84 | bool "Debug access to per_cpu maps" | |
85 | depends on DEBUG_KERNEL | |
3e5095d1 | 86 | depends on SMP |
c49a4955 | 87 | default n |
88 | help | |
89 | Say Y to verify that the per_cpu map being accessed has | |
90 | been setup. Adds a fair amount of code to kernel memory | |
91 | and decreases performance. | |
92 | ||
93 | Say N if unsure. | |
94 | ||
926e5392 AV |
95 | config X86_PTDUMP |
96 | bool "Export kernel pagetable layout to userspace via debugfs" | |
fe770bf0 | 97 | depends on DEBUG_KERNEL |
926e5392 AV |
98 | select DEBUG_FS |
99 | help | |
100 | Say Y here if you want to show the kernel pagetable layout in a | |
101 | debugfs file. This information is only useful for kernel developers | |
102 | who are working in architecture specific areas of the kernel. | |
103 | It is probably not a good idea to enable this feature in a production | |
104 | kernel. | |
105 | If in doubt, say "N" | |
106 | ||
63aaf308 AV |
107 | config DEBUG_RODATA |
108 | bool "Write protect kernel read-only data structures" | |
11201e60 | 109 | default y |
63aaf308 AV |
110 | depends on DEBUG_KERNEL |
111 | help | |
112 | Mark the kernel read-only data as write-protected in the pagetables, | |
113 | in order to catch accidental (and incorrect) writes to such const | |
11201e60 IM |
114 | data. This is recommended so that we can catch kernel bugs sooner. |
115 | If in doubt, say "Y". | |
63aaf308 | 116 | |
aba8391f IM |
117 | config DEBUG_RODATA_TEST |
118 | bool "Testcase for the DEBUG_RODATA feature" | |
119 | depends on DEBUG_RODATA | |
72370f2a | 120 | default y |
aba8391f IM |
121 | help |
122 | This option enables a testcase for the DEBUG_RODATA | |
123 | feature as well as for the change_page_attr() infrastructure. | |
124 | If in doubt, say "N" | |
125 | ||
126 | config DEBUG_NX_TEST | |
127 | tristate "Testcase for the NX non-executable stack feature" | |
128 | depends on DEBUG_KERNEL && m | |
129 | help | |
130 | This option enables a testcase for the CPU NX capability | |
131 | and the software setup of this feature. | |
132 | If in doubt, say "N" | |
133 | ||
1da177e4 LT |
134 | config 4KSTACKS |
135 | bool "Use 4Kb for kernel stacks instead of 8Kb" | |
d013a27c | 136 | depends on X86_32 |
1da177e4 LT |
137 | help |
138 | If you say Y here the kernel will use a 4Kb stacksize for the | |
139 | kernel stack attached to each process/thread. This facilitates | |
140 | running more threads on a system and also reduces the pressure | |
141 | on the VM subsystem for higher order allocations. This option | |
142 | will also use IRQ stacks to compensate for the reduced stackspace. | |
143 | ||
102e41fd AK |
144 | config DOUBLEFAULT |
145 | default y | |
146 | bool "Enable doublefault exception handler" if EMBEDDED | |
d013a27c RD |
147 | depends on X86_32 |
148 | help | |
149 | This option allows trapping of rare doublefault exceptions that | |
150 | would otherwise cause a system to silently reboot. Disabling this | |
151 | option saves about 4k and might cause you much additional grey | |
152 | hair. | |
153 | ||
154 | config IOMMU_DEBUG | |
155 | bool "Enable IOMMU debugging" | |
966396d3 | 156 | depends on GART_IOMMU && DEBUG_KERNEL |
d013a27c | 157 | depends on X86_64 |
102e41fd | 158 | help |
d013a27c RD |
159 | Force the IOMMU to on even when you have less than 4GB of |
160 | memory and add debugging code. On overflow always panic. And | |
161 | allow to enable IOMMU leak tracing. Can be disabled at boot | |
162 | time with iommu=noforce. This will also enable scatter gather | |
163 | list merging. Currently not recommended for production | |
164 | code. When you use it make sure you have a big enough | |
165 | IOMMU/AGP aperture. Most of the options enabled by this can | |
166 | be set more finegrained using the iommu= command line | |
167 | options. See Documentation/x86_64/boot-options.txt for more | |
168 | details. | |
169 | ||
170 | config IOMMU_LEAK | |
171 | bool "IOMMU leak tracing" | |
172 | depends on DEBUG_KERNEL | |
173 | depends on IOMMU_DEBUG | |
174 | help | |
175 | Add a simple leak tracer to the IOMMU code. This is useful when you | |
176 | are debugging a buggy device driver that leaks IOMMU mappings. | |
177 | ||
8b7d89d0 | 178 | config MMIOTRACE |
d61fc448 | 179 | bool "Memory mapped IO tracing" |
37b36192 | 180 | depends on DEBUG_KERNEL && PCI |
f984b51e | 181 | select TRACING |
8b7d89d0 | 182 | help |
d61fc448 PP |
183 | Mmiotrace traces Memory Mapped I/O access and is meant for |
184 | debugging and reverse engineering. It is called from the ioremap | |
c6c67c1a | 185 | implementation and works via page faults. Tracing is disabled by |
37b36192 | 186 | default and can be enabled at run-time. |
8b7d89d0 | 187 | |
c6c67c1a | 188 | See Documentation/tracers/mmiotrace.txt. |
8b7d89d0 PP |
189 | If you are not helping to develop drivers, say N. |
190 | ||
191 | config MMIOTRACE_TEST | |
192 | tristate "Test module for mmiotrace" | |
193 | depends on MMIOTRACE && m | |
8b7d89d0 PP |
194 | help |
195 | This is a dumb module for testing mmiotrace. It is very dangerous | |
196 | as it will write garbage to IO memory starting at a given address. | |
197 | However, it should be safe to use on e.g. unused portion of VRAM. | |
198 | ||
199 | Say N, unless you absolutely know what you are doing. | |
200 | ||
6e7c4025 IM |
201 | # |
202 | # IO delay types: | |
203 | # | |
204 | ||
205 | config IO_DELAY_TYPE_0X80 | |
206 | int | |
207 | default "0" | |
208 | ||
209 | config IO_DELAY_TYPE_0XED | |
210 | int | |
211 | default "1" | |
212 | ||
213 | config IO_DELAY_TYPE_UDELAY | |
214 | int | |
215 | default "2" | |
216 | ||
217 | config IO_DELAY_TYPE_NONE | |
218 | int | |
219 | default "3" | |
220 | ||
221 | choice | |
222 | prompt "IO delay type" | |
fd59e9e9 | 223 | default IO_DELAY_0X80 |
6e7c4025 IM |
224 | |
225 | config IO_DELAY_0X80 | |
226 | bool "port 0x80 based port-IO delay [recommended]" | |
227 | help | |
228 | This is the traditional Linux IO delay used for in/out_p. | |
229 | It is the most tested hence safest selection here. | |
230 | ||
231 | config IO_DELAY_0XED | |
232 | bool "port 0xed based port-IO delay" | |
233 | help | |
234 | Use port 0xed as the IO delay. This frees up port 0x80 which is | |
235 | often used as a hardware-debug port. | |
236 | ||
237 | config IO_DELAY_UDELAY | |
238 | bool "udelay based port-IO delay" | |
239 | help | |
240 | Use udelay(2) as the IO delay method. This provides the delay | |
241 | while not having any side-effect on the IO port space. | |
242 | ||
243 | config IO_DELAY_NONE | |
244 | bool "no port-IO delay" | |
b02aae9c | 245 | help |
6e7c4025 IM |
246 | No port-IO delay. Will break on old boxes that require port-IO |
247 | delay for certain operations. Should work on most new machines. | |
248 | ||
249 | endchoice | |
250 | ||
251 | if IO_DELAY_0X80 | |
252 | config DEFAULT_IO_DELAY_TYPE | |
253 | int | |
254 | default IO_DELAY_TYPE_0X80 | |
255 | endif | |
256 | ||
257 | if IO_DELAY_0XED | |
258 | config DEFAULT_IO_DELAY_TYPE | |
259 | int | |
260 | default IO_DELAY_TYPE_0XED | |
261 | endif | |
262 | ||
263 | if IO_DELAY_UDELAY | |
264 | config DEFAULT_IO_DELAY_TYPE | |
265 | int | |
266 | default IO_DELAY_TYPE_UDELAY | |
267 | endif | |
268 | ||
269 | if IO_DELAY_NONE | |
270 | config DEFAULT_IO_DELAY_TYPE | |
271 | int | |
272 | default IO_DELAY_TYPE_NONE | |
273 | endif | |
b02aae9c | 274 | |
6d7d7433 HY |
275 | config DEBUG_BOOT_PARAMS |
276 | bool "Debug boot parameters" | |
277 | depends on DEBUG_KERNEL | |
278 | depends on DEBUG_FS | |
279 | help | |
280 | This option will cause struct boot_params to be exported via debugfs. | |
281 | ||
0c42f392 | 282 | config CPA_DEBUG |
971a52d6 | 283 | bool "CPA self-test code" |
f316fe68 | 284 | depends on DEBUG_KERNEL |
0c42f392 | 285 | help |
971a52d6 | 286 | Do change_page_attr() self-tests every 30 seconds. |
0c42f392 | 287 | |
60a3cdd0 IM |
288 | config OPTIMIZE_INLINING |
289 | bool "Allow gcc to uninline functions marked 'inline'" | |
60a3cdd0 IM |
290 | help |
291 | This option determines if the kernel forces gcc to inline the functions | |
292 | developers have marked 'inline'. Doing so takes away freedom from gcc to | |
293 | do what it thinks is best, which is desirable for the gcc 3.x series of | |
294 | compilers. The gcc 4.x series have a rewritten inlining algorithm and | |
63fb7085 SW |
295 | enabling this option will generate a smaller kernel there. Hopefully |
296 | this algorithm is so good that allowing gcc 4.x and above to make the | |
297 | decision will become the default in the future. Until then this option | |
298 | is there to test gcc for this. | |
c9af1e33 | 299 | |
3f9b5cc0 IM |
300 | If unsure, say N. |
301 | ||
c9af1e33 IM |
302 | endmenu |
303 |