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1 | menu "Kernel hacking" |
2 | |
3 | config TRACE_IRQFLAGS_SUPPORT |
4 | def_bool y |
5 | |
6 | source "lib/Kconfig.debug" |
7 | |
8 | config 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 | |
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 | |
33 | config EARLY_PRINTK |
34 | bool "Early printk" if EMBEDDED |
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 EARLY_PRINTK_DBGP |
47 | bool "Early printk via EHCI debug port" |
48 | default n |
49 | depends on EARLY_PRINTK && PCI |
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 | |
59 | config DEBUG_STACKOVERFLOW |
60 | bool "Check for stack overflows" |
61 | depends on DEBUG_KERNEL |
62 | ---help--- |
63 | This option will cause messages to be printed if free stack space |
64 | drops below a certain limit. |
65 | |
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 | |
75 | config DEBUG_PER_CPU_MAPS |
76 | bool "Debug access to per_cpu maps" |
77 | depends on DEBUG_KERNEL |
78 | depends on SMP |
79 | default n |
80 | ---help--- |
81 | Say Y to verify that the per_cpu map being accessed has |
82 | been setup. Adds a fair amount of code to kernel memory |
83 | and decreases performance. |
84 | |
85 | Say N if unsure. |
86 | |
87 | config X86_PTDUMP |
88 | bool "Export kernel pagetable layout to userspace via debugfs" |
89 | depends on DEBUG_KERNEL |
90 | select DEBUG_FS |
91 | ---help--- |
92 | Say Y here if you want to show the kernel pagetable layout in a |
93 | debugfs file. This information is only useful for kernel developers |
94 | who are working in architecture specific areas of the kernel. |
95 | It is probably not a good idea to enable this feature in a production |
96 | kernel. |
97 | If in doubt, say "N" |
98 | |
99 | config DEBUG_RODATA |
100 | bool "Write protect kernel read-only data structures" |
101 | default y |
102 | depends on DEBUG_KERNEL |
103 | ---help--- |
104 | Mark the kernel read-only data as write-protected in the pagetables, |
105 | in order to catch accidental (and incorrect) writes to such const |
106 | data. This is recommended so that we can catch kernel bugs sooner. |
107 | If in doubt, say "Y". |
108 | |
109 | config DEBUG_RODATA_TEST |
110 | bool "Testcase for the DEBUG_RODATA feature" |
111 | depends on DEBUG_RODATA |
112 | default y |
113 | ---help--- |
114 | This option enables a testcase for the DEBUG_RODATA |
115 | feature as well as for the change_page_attr() infrastructure. |
116 | If in doubt, say "N" |
117 | |
118 | config DEBUG_NX_TEST |
119 | tristate "Testcase for the NX non-executable stack feature" |
120 | depends on DEBUG_KERNEL && m |
121 | ---help--- |
122 | This option enables a testcase for the CPU NX capability |
123 | and the software setup of this feature. |
124 | If in doubt, say "N" |
125 | |
126 | config 4KSTACKS |
127 | bool "Use 4Kb for kernel stacks instead of 8Kb" |
128 | depends on X86_32 |
129 | ---help--- |
130 | If you say Y here the kernel will use a 4Kb stacksize for the |
131 | kernel stack attached to each process/thread. This facilitates |
132 | running more threads on a system and also reduces the pressure |
133 | on the VM subsystem for higher order allocations. This option |
134 | will also use IRQ stacks to compensate for the reduced stackspace. |
135 | |
136 | config DOUBLEFAULT |
137 | default y |
138 | bool "Enable doublefault exception handler" if EMBEDDED |
139 | depends on X86_32 |
140 | ---help--- |
141 | This option allows trapping of rare doublefault exceptions that |
142 | would otherwise cause a system to silently reboot. Disabling this |
143 | option saves about 4k and might cause you much additional grey |
144 | hair. |
145 | |
146 | config IOMMU_DEBUG |
147 | bool "Enable IOMMU debugging" |
148 | depends on GART_IOMMU && DEBUG_KERNEL |
149 | depends on X86_64 |
150 | ---help--- |
151 | Force the IOMMU to on even when you have less than 4GB of |
152 | memory and add debugging code. On overflow always panic. And |
153 | allow to enable IOMMU leak tracing. Can be disabled at boot |
154 | time with iommu=noforce. This will also enable scatter gather |
155 | list merging. Currently not recommended for production |
156 | code. When you use it make sure you have a big enough |
157 | IOMMU/AGP aperture. Most of the options enabled by this can |
158 | be set more finegrained using the iommu= command line |
159 | options. See Documentation/x86_64/boot-options.txt for more |
160 | details. |
161 | |
162 | config IOMMU_STRESS |
163 | bool "Enable IOMMU stress-test mode" |
164 | ---help--- |
165 | This option disables various optimizations in IOMMU related |
166 | code to do real stress testing of the IOMMU code. This option |
167 | will cause a performance drop and should only be enabled for |
168 | testing. |
169 | |
170 | config IOMMU_LEAK |
171 | bool "IOMMU leak tracing" |
172 | depends on IOMMU_DEBUG && DMA_API_DEBUG |
173 | ---help--- |
174 | Add a simple leak tracer to the IOMMU code. This is useful when you |
175 | are debugging a buggy device driver that leaks IOMMU mappings. |
176 | |
177 | config X86_DS_SELFTEST |
178 | bool "DS selftest" |
179 | default y |
180 | depends on DEBUG_KERNEL |
181 | depends on X86_DS |
182 | ---help--- |
183 | Perform Debug Store selftests at boot time. |
184 | If in doubt, say "N". |
185 | |
186 | config HAVE_MMIOTRACE_SUPPORT |
187 | def_bool y |
188 | |
189 | config X86_DECODER_SELFTEST |
190 | bool "x86 instruction decoder selftest" |
191 | depends on DEBUG_KERNEL && KPROBES |
192 | ---help--- |
193 | Perform x86 instruction decoder selftests at build time. |
194 | This option is useful for checking the sanity of x86 instruction |
195 | decoder code. |
196 | If unsure, say "N". |
197 | |
198 | # |
199 | # IO delay types: |
200 | # |
201 | |
202 | config IO_DELAY_TYPE_0X80 |
203 | int |
204 | default "0" |
205 | |
206 | config IO_DELAY_TYPE_0XED |
207 | int |
208 | default "1" |
209 | |
210 | config IO_DELAY_TYPE_UDELAY |
211 | int |
212 | default "2" |
213 | |
214 | config IO_DELAY_TYPE_NONE |
215 | int |
216 | default "3" |
217 | |
218 | choice |
219 | prompt "IO delay type" |
220 | default IO_DELAY_0X80 |
221 | |
222 | config IO_DELAY_0X80 |
223 | bool "port 0x80 based port-IO delay [recommended]" |
224 | ---help--- |
225 | This is the traditional Linux IO delay used for in/out_p. |
226 | It is the most tested hence safest selection here. |
227 | |
228 | config IO_DELAY_0XED |
229 | bool "port 0xed based port-IO delay" |
230 | ---help--- |
231 | Use port 0xed as the IO delay. This frees up port 0x80 which is |
232 | often used as a hardware-debug port. |
233 | |
234 | config IO_DELAY_UDELAY |
235 | bool "udelay based port-IO delay" |
236 | ---help--- |
237 | Use udelay(2) as the IO delay method. This provides the delay |
238 | while not having any side-effect on the IO port space. |
239 | |
240 | config IO_DELAY_NONE |
241 | bool "no port-IO delay" |
242 | ---help--- |
243 | No port-IO delay. Will break on old boxes that require port-IO |
244 | delay for certain operations. Should work on most new machines. |
245 | |
246 | endchoice |
247 | |
248 | if IO_DELAY_0X80 |
249 | config DEFAULT_IO_DELAY_TYPE |
250 | int |
251 | default IO_DELAY_TYPE_0X80 |
252 | endif |
253 | |
254 | if IO_DELAY_0XED |
255 | config DEFAULT_IO_DELAY_TYPE |
256 | int |
257 | default IO_DELAY_TYPE_0XED |
258 | endif |
259 | |
260 | if IO_DELAY_UDELAY |
261 | config DEFAULT_IO_DELAY_TYPE |
262 | int |
263 | default IO_DELAY_TYPE_UDELAY |
264 | endif |
265 | |
266 | if IO_DELAY_NONE |
267 | config DEFAULT_IO_DELAY_TYPE |
268 | int |
269 | default IO_DELAY_TYPE_NONE |
270 | endif |
271 | |
272 | config DEBUG_BOOT_PARAMS |
273 | bool "Debug boot parameters" |
274 | depends on DEBUG_KERNEL |
275 | depends on DEBUG_FS |
276 | ---help--- |
277 | This option will cause struct boot_params to be exported via debugfs. |
278 | |
279 | config CPA_DEBUG |
280 | bool "CPA self-test code" |
281 | depends on DEBUG_KERNEL |
282 | ---help--- |
283 | Do change_page_attr() self-tests every 30 seconds. |
284 | |
285 | config OPTIMIZE_INLINING |
286 | bool "Allow gcc to uninline functions marked 'inline'" |
287 | ---help--- |
288 | This option determines if the kernel forces gcc to inline the functions |
289 | developers have marked 'inline'. Doing so takes away freedom from gcc to |
290 | do what it thinks is best, which is desirable for the gcc 3.x series of |
291 | compilers. The gcc 4.x series have a rewritten inlining algorithm and |
292 | enabling this option will generate a smaller kernel there. Hopefully |
293 | this algorithm is so good that allowing gcc 4.x and above to make the |
294 | decision will become the default in the future. Until then this option |
295 | is there to test gcc for this. |
296 | |
297 | If unsure, say N. |
298 | |
299 | config DEBUG_STRICT_USER_COPY_CHECKS |
300 | bool "Strict copy size checks" |
301 | depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING |
302 | ---help--- |
303 | Enabling this option turns a certain set of sanity checks for user |
304 | copy operations into compile time failures. |
305 | |
306 | The copy_from_user() etc checks are there to help test if there |
307 | are sufficient security checks on the length argument of |
308 | the copy operation, by having gcc prove that the argument is |
309 | within bounds. |
310 | |
311 | If unsure, or if you run an older (pre 4.4) gcc, say N. |
312 | |
313 | endmenu |
314 |
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