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Linux/arch/x86/Kconfig.debug

  1 menu "Kernel hacking"
  2 
  3 config TRACE_IRQFLAGS_SUPPORT
  4         def_bool y
  5 
  6 source "lib/Kconfig.debug"
  7 
  8 config X86_VERBOSE_BOOTUP
  9         bool "Enable verbose x86 bootup info messages"
 10         default y
 11         ---help---
 12           Enables the informational output from the decompression stage
 13           (e.g. bzImage) of the boot. If you disable this you will still
 14           see errors. Disable this if you want silent bootup.
 15 
 16 config EARLY_PRINTK
 17         bool "Early printk" if EXPERT
 18         default y
 19         ---help---
 20           Write kernel log output directly into the VGA buffer or to a serial
 21           port.
 22 
 23           This is useful for kernel debugging when your machine crashes very
 24           early before the console code is initialized. For normal operation
 25           it is not recommended because it looks ugly and doesn't cooperate
 26           with klogd/syslogd or the X server. You should normally N here,
 27           unless you want to debug such a crash.
 28 
 29 config EARLY_PRINTK_DBGP
 30         bool "Early printk via EHCI debug port"
 31         depends on EARLY_PRINTK && PCI
 32         ---help---
 33           Write kernel log output directly into the EHCI debug port.
 34 
 35           This is useful for kernel debugging when your machine crashes very
 36           early before the console code is initialized. For normal operation
 37           it is not recommended because it looks ugly and doesn't cooperate
 38           with klogd/syslogd or the X server. You should normally N here,
 39           unless you want to debug such a crash. You need usb debug device.
 40 
 41 config EARLY_PRINTK_EFI
 42         bool "Early printk via the EFI framebuffer"
 43         depends on EFI && EARLY_PRINTK
 44         select FONT_SUPPORT
 45         ---help---
 46           Write kernel log output directly into the EFI framebuffer.
 47 
 48           This is useful for kernel debugging when your machine crashes very
 49           early before the console code is initialized.
 50 
 51 config X86_PTDUMP_CORE
 52         def_bool n
 53 
 54 config X86_PTDUMP
 55         tristate "Export kernel pagetable layout to userspace via debugfs"
 56         depends on DEBUG_KERNEL
 57         select DEBUG_FS
 58         select X86_PTDUMP_CORE
 59         ---help---
 60           Say Y here if you want to show the kernel pagetable layout in a
 61           debugfs file. This information is only useful for kernel developers
 62           who are working in architecture specific areas of the kernel.
 63           It is probably not a good idea to enable this feature in a production
 64           kernel.
 65           If in doubt, say "N"
 66 
 67 config EFI_PGT_DUMP
 68         bool "Dump the EFI pagetable"
 69         depends on EFI
 70         select X86_PTDUMP_CORE
 71         ---help---
 72           Enable this if you want to dump the EFI page table before
 73           enabling virtual mode. This can be used to debug miscellaneous
 74           issues with the mapping of the EFI runtime regions into that
 75           table.
 76 
 77 config DEBUG_RODATA
 78         bool "Write protect kernel read-only data structures"
 79         default y
 80         depends on DEBUG_KERNEL
 81         ---help---
 82           Mark the kernel read-only data as write-protected in the pagetables,
 83           in order to catch accidental (and incorrect) writes to such const
 84           data. This is recommended so that we can catch kernel bugs sooner.
 85           If in doubt, say "Y".
 86 
 87 config DEBUG_RODATA_TEST
 88         bool "Testcase for the DEBUG_RODATA feature"
 89         depends on DEBUG_RODATA
 90         default y
 91         ---help---
 92           This option enables a testcase for the DEBUG_RODATA
 93           feature as well as for the change_page_attr() infrastructure.
 94           If in doubt, say "N"
 95 
 96 config DEBUG_WX
 97         bool "Warn on W+X mappings at boot"
 98         depends on DEBUG_RODATA
 99         select X86_PTDUMP_CORE
100         ---help---
101           Generate a warning if any W+X mappings are found at boot.
102 
103           This is useful for discovering cases where the kernel is leaving
104           W+X mappings after applying NX, as such mappings are a security risk.
105 
106           Look for a message in dmesg output like this:
107 
108             x86/mm: Checked W+X mappings: passed, no W+X pages found.
109 
110           or like this, if the check failed:
111 
112             x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
113 
114           Note that even if the check fails, your kernel is possibly
115           still fine, as W+X mappings are not a security hole in
116           themselves, what they do is that they make the exploitation
117           of other unfixed kernel bugs easier.
118 
119           There is no runtime or memory usage effect of this option
120           once the kernel has booted up - it's a one time check.
121 
122           If in doubt, say "Y".
123 
124 config DEBUG_SET_MODULE_RONX
125         bool "Set loadable kernel module data as NX and text as RO"
126         depends on MODULES
127         ---help---
128           This option helps catch unintended modifications to loadable
129           kernel module's text and read-only data. It also prevents execution
130           of module data. Such protection may interfere with run-time code
131           patching and dynamic kernel tracing - and they might also protect
132           against certain classes of kernel exploits.
133           If in doubt, say "N".
134 
135 config DEBUG_NX_TEST
136         tristate "Testcase for the NX non-executable stack feature"
137         depends on DEBUG_KERNEL && m
138         ---help---
139           This option enables a testcase for the CPU NX capability
140           and the software setup of this feature.
141           If in doubt, say "N"
142 
143 config DOUBLEFAULT
144         default y
145         bool "Enable doublefault exception handler" if EXPERT
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 DEBUG_TLBFLUSH
153         bool "Set upper limit of TLB entries to flush one-by-one"
154         depends on DEBUG_KERNEL
155         ---help---
156 
157         X86-only for now.
158 
159         This option allows the user to tune the amount of TLB entries the
160         kernel flushes one-by-one instead of doing a full TLB flush. In
161         certain situations, the former is cheaper. This is controlled by the
162         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
163         to -1, the code flushes the whole TLB unconditionally. Otherwise,
164         for positive values of it, the kernel will use single TLB entry
165         invalidating instructions according to the following formula:
166 
167         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
168 
169         If in doubt, say "N".
170 
171 config IOMMU_DEBUG
172         bool "Enable IOMMU debugging"
173         depends on GART_IOMMU && DEBUG_KERNEL
174         depends on X86_64
175         ---help---
176           Force the IOMMU to on even when you have less than 4GB of
177           memory and add debugging code. On overflow always panic. And
178           allow to enable IOMMU leak tracing. Can be disabled at boot
179           time with iommu=noforce. This will also enable scatter gather
180           list merging.  Currently not recommended for production
181           code. When you use it make sure you have a big enough
182           IOMMU/AGP aperture.  Most of the options enabled by this can
183           be set more finegrained using the iommu= command line
184           options. See Documentation/x86/x86_64/boot-options.txt for more
185           details.
186 
187 config IOMMU_STRESS
188         bool "Enable IOMMU stress-test mode"
189         ---help---
190           This option disables various optimizations in IOMMU related
191           code to do real stress testing of the IOMMU code. This option
192           will cause a performance drop and should only be enabled for
193           testing.
194 
195 config IOMMU_LEAK
196         bool "IOMMU leak tracing"
197         depends on IOMMU_DEBUG && DMA_API_DEBUG
198         ---help---
199           Add a simple leak tracer to the IOMMU code. This is useful when you
200           are debugging a buggy device driver that leaks IOMMU mappings.
201 
202 config HAVE_MMIOTRACE_SUPPORT
203         def_bool y
204 
205 config X86_DECODER_SELFTEST
206         bool "x86 instruction decoder selftest"
207         depends on DEBUG_KERNEL && KPROBES
208         depends on !COMPILE_TEST
209         ---help---
210          Perform x86 instruction decoder selftests at build time.
211          This option is useful for checking the sanity of x86 instruction
212          decoder code.
213          If unsure, say "N".
214 
215 #
216 # IO delay types:
217 #
218 
219 config IO_DELAY_TYPE_0X80
220         int
221         default "0"
222 
223 config IO_DELAY_TYPE_0XED
224         int
225         default "1"
226 
227 config IO_DELAY_TYPE_UDELAY
228         int
229         default "2"
230 
231 config IO_DELAY_TYPE_NONE
232         int
233         default "3"
234 
235 choice
236         prompt "IO delay type"
237         default IO_DELAY_0X80
238 
239 config IO_DELAY_0X80
240         bool "port 0x80 based port-IO delay [recommended]"
241         ---help---
242           This is the traditional Linux IO delay used for in/out_p.
243           It is the most tested hence safest selection here.
244 
245 config IO_DELAY_0XED
246         bool "port 0xed based port-IO delay"
247         ---help---
248           Use port 0xed as the IO delay. This frees up port 0x80 which is
249           often used as a hardware-debug port.
250 
251 config IO_DELAY_UDELAY
252         bool "udelay based port-IO delay"
253         ---help---
254           Use udelay(2) as the IO delay method. This provides the delay
255           while not having any side-effect on the IO port space.
256 
257 config IO_DELAY_NONE
258         bool "no port-IO delay"
259         ---help---
260           No port-IO delay. Will break on old boxes that require port-IO
261           delay for certain operations. Should work on most new machines.
262 
263 endchoice
264 
265 if IO_DELAY_0X80
266 config DEFAULT_IO_DELAY_TYPE
267         int
268         default IO_DELAY_TYPE_0X80
269 endif
270 
271 if IO_DELAY_0XED
272 config DEFAULT_IO_DELAY_TYPE
273         int
274         default IO_DELAY_TYPE_0XED
275 endif
276 
277 if IO_DELAY_UDELAY
278 config DEFAULT_IO_DELAY_TYPE
279         int
280         default IO_DELAY_TYPE_UDELAY
281 endif
282 
283 if IO_DELAY_NONE
284 config DEFAULT_IO_DELAY_TYPE
285         int
286         default IO_DELAY_TYPE_NONE
287 endif
288 
289 config DEBUG_BOOT_PARAMS
290         bool "Debug boot parameters"
291         depends on DEBUG_KERNEL
292         depends on DEBUG_FS
293         ---help---
294           This option will cause struct boot_params to be exported via debugfs.
295 
296 config CPA_DEBUG
297         bool "CPA self-test code"
298         depends on DEBUG_KERNEL
299         ---help---
300           Do change_page_attr() self-tests every 30 seconds.
301 
302 config OPTIMIZE_INLINING
303         bool "Allow gcc to uninline functions marked 'inline'"
304         ---help---
305           This option determines if the kernel forces gcc to inline the functions
306           developers have marked 'inline'. Doing so takes away freedom from gcc to
307           do what it thinks is best, which is desirable for the gcc 3.x series of
308           compilers. The gcc 4.x series have a rewritten inlining algorithm and
309           enabling this option will generate a smaller kernel there. Hopefully
310           this algorithm is so good that allowing gcc 4.x and above to make the
311           decision will become the default in the future. Until then this option
312           is there to test gcc for this.
313 
314           If unsure, say N.
315 
316 config DEBUG_ENTRY
317         bool "Debug low-level entry code"
318         depends on DEBUG_KERNEL
319         ---help---
320           This option enables sanity checks in x86's low-level entry code.
321           Some of these sanity checks may slow down kernel entries and
322           exits or otherwise impact performance.
323 
324           This is currently used to help test NMI code.
325 
326           If unsure, say N.
327 
328 config DEBUG_NMI_SELFTEST
329         bool "NMI Selftest"
330         depends on DEBUG_KERNEL && X86_LOCAL_APIC
331         ---help---
332           Enabling this option turns on a quick NMI selftest to verify
333           that the NMI behaves correctly.
334 
335           This might help diagnose strange hangs that rely on NMI to
336           function properly.
337 
338           If unsure, say N.
339 
340 config DEBUG_IMR_SELFTEST
341         bool "Isolated Memory Region self test"
342         default n
343         depends on INTEL_IMR
344         ---help---
345           This option enables automated sanity testing of the IMR code.
346           Some simple tests are run to verify IMR bounds checking, alignment
347           and overlapping. This option is really only useful if you are
348           debugging an IMR memory map or are modifying the IMR code and want to
349           test your changes.
350 
351           If unsure say N here.
352 
353 config X86_DEBUG_STATIC_CPU_HAS
354         bool "Debug alternatives"
355         depends on DEBUG_KERNEL
356         ---help---
357           This option causes additional code to be generated which
358           fails if static_cpu_has() is used before alternatives have
359           run.
360 
361           If unsure, say N.
362 
363 config X86_DEBUG_FPU
364         bool "Debug the x86 FPU code"
365         depends on DEBUG_KERNEL
366         default y
367         ---help---
368           If this option is enabled then there will be extra sanity
369           checks and (boot time) debug printouts added to the kernel.
370           This debugging adds some small amount of runtime overhead
371           to the kernel.
372 
373           If unsure, say N.
374 
375 config PUNIT_ATOM_DEBUG
376         tristate "ATOM Punit debug driver"
377         select DEBUG_FS
378         select IOSF_MBI
379         ---help---
380           This is a debug driver, which gets the power states
381           of all Punit North Complex devices. The power states of
382           each device is exposed as part of the debugfs interface.
383           The current power state can be read from
384           /sys/kernel/debug/punit_atom/dev_power_state
385 
386 endmenu

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