Root/arch/x86/Kconfig.debug

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 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
46config 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
59config 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
66config 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
75config 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
87config 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
99config 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
109config 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
118config 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
126config 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
136config 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
146config 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
162config 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
170config 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
177config 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
186config HAVE_MMIOTRACE_SUPPORT
187    def_bool y
188
189config 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
202config IO_DELAY_TYPE_0X80
203    int
204    default "0"
205
206config IO_DELAY_TYPE_0XED
207    int
208    default "1"
209
210config IO_DELAY_TYPE_UDELAY
211    int
212    default "2"
213
214config IO_DELAY_TYPE_NONE
215    int
216    default "3"
217
218choice
219    prompt "IO delay type"
220    default IO_DELAY_0X80
221
222config 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
228config 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
234config 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
240config 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
246endchoice
247
248if IO_DELAY_0X80
249config DEFAULT_IO_DELAY_TYPE
250    int
251    default IO_DELAY_TYPE_0X80
252endif
253
254if IO_DELAY_0XED
255config DEFAULT_IO_DELAY_TYPE
256    int
257    default IO_DELAY_TYPE_0XED
258endif
259
260if IO_DELAY_UDELAY
261config DEFAULT_IO_DELAY_TYPE
262    int
263    default IO_DELAY_TYPE_UDELAY
264endif
265
266if IO_DELAY_NONE
267config DEFAULT_IO_DELAY_TYPE
268    int
269    default IO_DELAY_TYPE_NONE
270endif
271
272config 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
279config 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
285config 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
299config 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
313endmenu
314

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