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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 IM |
8 | config STRICT_DEVMEM |
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 | ||
46 | config DEBUG_STACKOVERFLOW | |
47 | bool "Check for stack overflows" | |
48 | depends on DEBUG_KERNEL | |
dab175f3 AB |
49 | help |
50 | This option will cause messages to be printed if free stack space | |
51 | drops below a certain limit. | |
1da177e4 | 52 | |
1da177e4 LT |
53 | config DEBUG_STACK_USAGE |
54 | bool "Stack utilization instrumentation" | |
55 | depends on DEBUG_KERNEL | |
56 | help | |
57 | Enables the display of the minimum amount of free stack which each | |
58 | task has ever had available in the sysrq-T and sysrq-P debug output. | |
59 | ||
60 | This option will slow down process creation somewhat. | |
61 | ||
1da177e4 | 62 | config DEBUG_PAGEALLOC |
4a2f0acf | 63 | bool "Debug page memory allocations" |
b1d95f4e | 64 | depends on DEBUG_KERNEL |
1da177e4 LT |
65 | help |
66 | Unmap pages from the kernel linear mapping after free_pages(). | |
67 | This results in a large slowdown, but helps to find certain types | |
68 | of memory corruptions. | |
69 | ||
c49a4955 | 70 | config DEBUG_PER_CPU_MAPS |
71 | bool "Debug access to per_cpu maps" | |
72 | depends on DEBUG_KERNEL | |
23ca4bba | 73 | depends on X86_SMP |
c49a4955 | 74 | default n |
75 | help | |
76 | Say Y to verify that the per_cpu map being accessed has | |
77 | been setup. Adds a fair amount of code to kernel memory | |
78 | and decreases performance. | |
79 | ||
80 | Say N if unsure. | |
81 | ||
926e5392 AV |
82 | config X86_PTDUMP |
83 | bool "Export kernel pagetable layout to userspace via debugfs" | |
fe770bf0 | 84 | depends on DEBUG_KERNEL |
926e5392 AV |
85 | select DEBUG_FS |
86 | help | |
87 | Say Y here if you want to show the kernel pagetable layout in a | |
88 | debugfs file. This information is only useful for kernel developers | |
89 | who are working in architecture specific areas of the kernel. | |
90 | It is probably not a good idea to enable this feature in a production | |
91 | kernel. | |
92 | If in doubt, say "N" | |
93 | ||
63aaf308 AV |
94 | config DEBUG_RODATA |
95 | bool "Write protect kernel read-only data structures" | |
11201e60 | 96 | default y |
63aaf308 AV |
97 | depends on DEBUG_KERNEL |
98 | help | |
99 | Mark the kernel read-only data as write-protected in the pagetables, | |
100 | in order to catch accidental (and incorrect) writes to such const | |
11201e60 IM |
101 | data. This is recommended so that we can catch kernel bugs sooner. |
102 | If in doubt, say "Y". | |
63aaf308 | 103 | |
00d1c5e0 IM |
104 | config DIRECT_GBPAGES |
105 | bool "Enable gbpages-mapped kernel pagetables" | |
106 | depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64 | |
107 | help | |
108 | Enable gigabyte pages support (if the CPU supports it). This can | |
109 | improve the kernel's performance a tiny bit by reducing TLB | |
110 | pressure. | |
111 | ||
112 | This is experimental code. | |
113 | ||
114 | If in doubt, say "N". | |
115 | ||
aba8391f IM |
116 | config DEBUG_RODATA_TEST |
117 | bool "Testcase for the DEBUG_RODATA feature" | |
118 | depends on DEBUG_RODATA | |
119 | help | |
120 | This option enables a testcase for the DEBUG_RODATA | |
121 | feature as well as for the change_page_attr() infrastructure. | |
122 | If in doubt, say "N" | |
123 | ||
124 | config DEBUG_NX_TEST | |
125 | tristate "Testcase for the NX non-executable stack feature" | |
126 | depends on DEBUG_KERNEL && m | |
127 | help | |
128 | This option enables a testcase for the CPU NX capability | |
129 | and the software setup of this feature. | |
130 | If in doubt, say "N" | |
131 | ||
1da177e4 LT |
132 | config 4KSTACKS |
133 | bool "Use 4Kb for kernel stacks instead of 8Kb" | |
d013a27c | 134 | depends on X86_32 |
1da177e4 LT |
135 | help |
136 | If you say Y here the kernel will use a 4Kb stacksize for the | |
137 | kernel stack attached to each process/thread. This facilitates | |
138 | running more threads on a system and also reduces the pressure | |
139 | on the VM subsystem for higher order allocations. This option | |
140 | will also use IRQ stacks to compensate for the reduced stackspace. | |
141 | ||
102e41fd AK |
142 | config DOUBLEFAULT |
143 | default y | |
144 | bool "Enable doublefault exception handler" if EMBEDDED | |
d013a27c RD |
145 | depends on X86_32 |
146 | help | |
147 | This option allows trapping of rare doublefault exceptions that | |
148 | would otherwise cause a system to silently reboot. Disabling this | |
149 | option saves about 4k and might cause you much additional grey | |
150 | hair. | |
151 | ||
152 | config IOMMU_DEBUG | |
153 | bool "Enable IOMMU debugging" | |
966396d3 | 154 | depends on GART_IOMMU && DEBUG_KERNEL |
d013a27c | 155 | depends on X86_64 |
102e41fd | 156 | help |
d013a27c RD |
157 | Force the IOMMU to on even when you have less than 4GB of |
158 | memory and add debugging code. On overflow always panic. And | |
159 | allow to enable IOMMU leak tracing. Can be disabled at boot | |
160 | time with iommu=noforce. This will also enable scatter gather | |
161 | list merging. Currently not recommended for production | |
162 | code. When you use it make sure you have a big enough | |
163 | IOMMU/AGP aperture. Most of the options enabled by this can | |
164 | be set more finegrained using the iommu= command line | |
165 | options. See Documentation/x86_64/boot-options.txt for more | |
166 | details. | |
167 | ||
168 | config IOMMU_LEAK | |
169 | bool "IOMMU leak tracing" | |
170 | depends on DEBUG_KERNEL | |
171 | depends on IOMMU_DEBUG | |
172 | help | |
173 | Add a simple leak tracer to the IOMMU code. This is useful when you | |
174 | are debugging a buggy device driver that leaks IOMMU mappings. | |
175 | ||
10c43d2e PP |
176 | config MMIOTRACE_HOOKS |
177 | bool | |
86069782 | 178 | |
8b7d89d0 | 179 | config MMIOTRACE |
d61fc448 | 180 | bool "Memory mapped IO tracing" |
37b36192 | 181 | depends on DEBUG_KERNEL && PCI |
f984b51e | 182 | select TRACING |
10c43d2e | 183 | select MMIOTRACE_HOOKS |
8b7d89d0 | 184 | help |
d61fc448 PP |
185 | Mmiotrace traces Memory Mapped I/O access and is meant for |
186 | debugging and reverse engineering. It is called from the ioremap | |
c6c67c1a | 187 | implementation and works via page faults. Tracing is disabled by |
37b36192 | 188 | default and can be enabled at run-time. |
8b7d89d0 | 189 | |
c6c67c1a | 190 | See Documentation/tracers/mmiotrace.txt. |
8b7d89d0 PP |
191 | If you are not helping to develop drivers, say N. |
192 | ||
193 | config MMIOTRACE_TEST | |
194 | tristate "Test module for mmiotrace" | |
195 | depends on MMIOTRACE && m | |
8b7d89d0 PP |
196 | help |
197 | This is a dumb module for testing mmiotrace. It is very dangerous | |
198 | as it will write garbage to IO memory starting at a given address. | |
199 | However, it should be safe to use on e.g. unused portion of VRAM. | |
200 | ||
201 | Say N, unless you absolutely know what you are doing. | |
202 | ||
6e7c4025 IM |
203 | # |
204 | # IO delay types: | |
205 | # | |
206 | ||
207 | config IO_DELAY_TYPE_0X80 | |
208 | int | |
209 | default "0" | |
210 | ||
211 | config IO_DELAY_TYPE_0XED | |
212 | int | |
213 | default "1" | |
214 | ||
215 | config IO_DELAY_TYPE_UDELAY | |
216 | int | |
217 | default "2" | |
218 | ||
219 | config IO_DELAY_TYPE_NONE | |
220 | int | |
221 | default "3" | |
222 | ||
223 | choice | |
224 | prompt "IO delay type" | |
fd59e9e9 | 225 | default IO_DELAY_0X80 |
6e7c4025 IM |
226 | |
227 | config 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 | ||
233 | config 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 | ||
239 | config 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 | ||
245 | config IO_DELAY_NONE | |
246 | bool "no port-IO delay" | |
b02aae9c | 247 | help |
6e7c4025 IM |
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 | ||
251 | endchoice | |
252 | ||
253 | if IO_DELAY_0X80 | |
254 | config DEFAULT_IO_DELAY_TYPE | |
255 | int | |
256 | default IO_DELAY_TYPE_0X80 | |
257 | endif | |
258 | ||
259 | if IO_DELAY_0XED | |
260 | config DEFAULT_IO_DELAY_TYPE | |
261 | int | |
262 | default IO_DELAY_TYPE_0XED | |
263 | endif | |
264 | ||
265 | if IO_DELAY_UDELAY | |
266 | config DEFAULT_IO_DELAY_TYPE | |
267 | int | |
268 | default IO_DELAY_TYPE_UDELAY | |
269 | endif | |
270 | ||
271 | if IO_DELAY_NONE | |
272 | config DEFAULT_IO_DELAY_TYPE | |
273 | int | |
274 | default IO_DELAY_TYPE_NONE | |
275 | endif | |
b02aae9c | 276 | |
6d7d7433 HY |
277 | config 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 | ||
0c42f392 | 284 | config CPA_DEBUG |
971a52d6 | 285 | bool "CPA self-test code" |
f316fe68 | 286 | depends on DEBUG_KERNEL |
0c42f392 | 287 | help |
971a52d6 | 288 | Do change_page_attr() self-tests every 30 seconds. |
0c42f392 | 289 | |
60a3cdd0 IM |
290 | config OPTIMIZE_INLINING |
291 | bool "Allow gcc to uninline functions marked 'inline'" | |
60a3cdd0 IM |
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 | disabling this option will generate a smaller kernel there. Hopefully | |
298 | this algorithm is so good that allowing gcc4 to make the decision can | |
299 | become the default in the future, until then this option is there to | |
300 | test gcc for this. | |
c9af1e33 | 301 | |
3f9b5cc0 IM |
302 | If unsure, say N. |
303 | ||
c9af1e33 IM |
304 | endmenu |
305 |