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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_TEST
 78         bool "Testcase for the marking rodata read-only"
 79         default y
 80         ---help---
 81           This option enables a testcase for the setting rodata read-only
 82           as well as for the change_page_attr() infrastructure.
 83           If in doubt, say "N"
 84 
 85 config DEBUG_WX
 86         bool "Warn on W+X mappings at boot"
 87         select X86_PTDUMP_CORE
 88         ---help---
 89           Generate a warning if any W+X mappings are found at boot.
 90 
 91           This is useful for discovering cases where the kernel is leaving
 92           W+X mappings after applying NX, as such mappings are a security risk.
 93 
 94           Look for a message in dmesg output like this:
 95 
 96             x86/mm: Checked W+X mappings: passed, no W+X pages found.
 97 
 98           or like this, if the check failed:
 99 
100             x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
101 
102           Note that even if the check fails, your kernel is possibly
103           still fine, as W+X mappings are not a security hole in
104           themselves, what they do is that they make the exploitation
105           of other unfixed kernel bugs easier.
106 
107           There is no runtime or memory usage effect of this option
108           once the kernel has booted up - it's a one time check.
109 
110           If in doubt, say "Y".
111 
112 config DEBUG_SET_MODULE_RONX
113         bool "Set loadable kernel module data as NX and text as RO"
114         depends on MODULES
115         ---help---
116           This option helps catch unintended modifications to loadable
117           kernel module's text and read-only data. It also prevents execution
118           of module data. Such protection may interfere with run-time code
119           patching and dynamic kernel tracing - and they might also protect
120           against certain classes of kernel exploits.
121           If in doubt, say "N".
122 
123 config DEBUG_NX_TEST
124         tristate "Testcase for the NX non-executable stack feature"
125         depends on DEBUG_KERNEL && m
126         ---help---
127           This option enables a testcase for the CPU NX capability
128           and the software setup of this feature.
129           If in doubt, say "N"
130 
131 config DOUBLEFAULT
132         default y
133         bool "Enable doublefault exception handler" if EXPERT
134         ---help---
135           This option allows trapping of rare doublefault exceptions that
136           would otherwise cause a system to silently reboot. Disabling this
137           option saves about 4k and might cause you much additional grey
138           hair.
139 
140 config DEBUG_TLBFLUSH
141         bool "Set upper limit of TLB entries to flush one-by-one"
142         depends on DEBUG_KERNEL
143         ---help---
144 
145         X86-only for now.
146 
147         This option allows the user to tune the amount of TLB entries the
148         kernel flushes one-by-one instead of doing a full TLB flush. In
149         certain situations, the former is cheaper. This is controlled by the
150         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
151         to -1, the code flushes the whole TLB unconditionally. Otherwise,
152         for positive values of it, the kernel will use single TLB entry
153         invalidating instructions according to the following formula:
154 
155         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
156 
157         If in doubt, say "N".
158 
159 config IOMMU_DEBUG
160         bool "Enable IOMMU debugging"
161         depends on GART_IOMMU && DEBUG_KERNEL
162         depends on X86_64
163         ---help---
164           Force the IOMMU to on even when you have less than 4GB of
165           memory and add debugging code. On overflow always panic. And
166           allow to enable IOMMU leak tracing. Can be disabled at boot
167           time with iommu=noforce. This will also enable scatter gather
168           list merging.  Currently not recommended for production
169           code. When you use it make sure you have a big enough
170           IOMMU/AGP aperture.  Most of the options enabled by this can
171           be set more finegrained using the iommu= command line
172           options. See Documentation/x86/x86_64/boot-options.txt for more
173           details.
174 
175 config IOMMU_STRESS
176         bool "Enable IOMMU stress-test mode"
177         ---help---
178           This option disables various optimizations in IOMMU related
179           code to do real stress testing of the IOMMU code. This option
180           will cause a performance drop and should only be enabled for
181           testing.
182 
183 config IOMMU_LEAK
184         bool "IOMMU leak tracing"
185         depends on IOMMU_DEBUG && DMA_API_DEBUG
186         ---help---
187           Add a simple leak tracer to the IOMMU code. This is useful when you
188           are debugging a buggy device driver that leaks IOMMU mappings.
189 
190 config HAVE_MMIOTRACE_SUPPORT
191         def_bool y
192 
193 config X86_DECODER_SELFTEST
194         bool "x86 instruction decoder selftest"
195         depends on DEBUG_KERNEL && KPROBES
196         depends on !COMPILE_TEST
197         ---help---
198          Perform x86 instruction decoder selftests at build time.
199          This option is useful for checking the sanity of x86 instruction
200          decoder code.
201          If unsure, say "N".
202 
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"
225         default IO_DELAY_0X80
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"
247         ---help---
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
276 
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 
284 config CPA_DEBUG
285         bool "CPA self-test code"
286         depends on DEBUG_KERNEL
287         ---help---
288           Do change_page_attr() self-tests every 30 seconds.
289 
290 config OPTIMIZE_INLINING
291         bool "Allow gcc to uninline functions marked 'inline'"
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           enabling this option will generate a smaller kernel there. Hopefully
298           this algorithm is so good that allowing gcc 4.x and above to make the
299           decision will become the default in the future. Until then this option
300           is there to test gcc for this.
301 
302           If unsure, say N.
303 
304 config DEBUG_ENTRY
305         bool "Debug low-level entry code"
306         depends on DEBUG_KERNEL
307         ---help---
308           This option enables sanity checks in x86's low-level entry code.
309           Some of these sanity checks may slow down kernel entries and
310           exits or otherwise impact performance.
311 
312           This is currently used to help test NMI code.
313 
314           If unsure, say N.
315 
316 config DEBUG_NMI_SELFTEST
317         bool "NMI Selftest"
318         depends on DEBUG_KERNEL && X86_LOCAL_APIC
319         ---help---
320           Enabling this option turns on a quick NMI selftest to verify
321           that the NMI behaves correctly.
322 
323           This might help diagnose strange hangs that rely on NMI to
324           function properly.
325 
326           If unsure, say N.
327 
328 config DEBUG_IMR_SELFTEST
329         bool "Isolated Memory Region self test"
330         default n
331         depends on INTEL_IMR
332         ---help---
333           This option enables automated sanity testing of the IMR code.
334           Some simple tests are run to verify IMR bounds checking, alignment
335           and overlapping. This option is really only useful if you are
336           debugging an IMR memory map or are modifying the IMR code and want to
337           test your changes.
338 
339           If unsure say N here.
340 
341 config X86_DEBUG_FPU
342         bool "Debug the x86 FPU code"
343         depends on DEBUG_KERNEL
344         default y
345         ---help---
346           If this option is enabled then there will be extra sanity
347           checks and (boot time) debug printouts added to the kernel.
348           This debugging adds some small amount of runtime overhead
349           to the kernel.
350 
351           If unsure, say N.
352 
353 config PUNIT_ATOM_DEBUG
354         tristate "ATOM Punit debug driver"
355         select DEBUG_FS
356         select IOSF_MBI
357         ---help---
358           This is a debug driver, which gets the power states
359           of all Punit North Complex devices. The power states of
360           each device is exposed as part of the debugfs interface.
361           The current power state can be read from
362           /sys/kernel/debug/punit_atom/dev_power_state
363 
364 endmenu

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