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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 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 EXPERT
 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         depends on EARLY_PRINTK && PCI
 49         ---help---
 50           Write kernel log output directly into the EHCI debug port.
 51 
 52           This is useful for kernel debugging when your machine crashes very
 53           early before the console code is initialized. For normal operation
 54           it is not recommended because it looks ugly and doesn't cooperate
 55           with klogd/syslogd or the X server. You should normally N here,
 56           unless you want to debug such a crash. You need usb debug device.
 57 
 58 config EARLY_PRINTK_EFI
 59         bool "Early printk via the EFI framebuffer"
 60         depends on EFI && EARLY_PRINTK
 61         select FONT_SUPPORT
 62         ---help---
 63           Write kernel log output directly into the EFI framebuffer.
 64 
 65           This is useful for kernel debugging when your machine crashes very
 66           early before the console code is initialized.
 67 
 68 config X86_PTDUMP_CORE
 69         def_bool n
 70 
 71 config X86_PTDUMP
 72         bool "Export kernel pagetable layout to userspace via debugfs"
 73         depends on DEBUG_KERNEL
 74         select DEBUG_FS
 75         select X86_PTDUMP_CORE
 76         ---help---
 77           Say Y here if you want to show the kernel pagetable layout in a
 78           debugfs file. This information is only useful for kernel developers
 79           who are working in architecture specific areas of the kernel.
 80           It is probably not a good idea to enable this feature in a production
 81           kernel.
 82           If in doubt, say "N"
 83 
 84 config EFI_PGT_DUMP
 85         bool "Dump the EFI pagetable"
 86         depends on EFI
 87         select X86_PTDUMP_CORE
 88         ---help---
 89           Enable this if you want to dump the EFI page table before
 90           enabling virtual mode. This can be used to debug miscellaneous
 91           issues with the mapping of the EFI runtime regions into that
 92           table.
 93 
 94 config DEBUG_RODATA
 95         bool "Write protect kernel read-only data structures"
 96         default y
 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
101           data. This is recommended so that we can catch kernel bugs sooner.
102           If in doubt, say "Y".
103 
104 config DEBUG_RODATA_TEST
105         bool "Testcase for the DEBUG_RODATA feature"
106         depends on DEBUG_RODATA
107         default y
108         ---help---
109           This option enables a testcase for the DEBUG_RODATA
110           feature as well as for the change_page_attr() infrastructure.
111           If in doubt, say "N"
112 
113 config DEBUG_WX
114         bool "Warn on W+X mappings at boot"
115         depends on DEBUG_RODATA
116         select X86_PTDUMP_CORE
117         ---help---
118           Generate a warning if any W+X mappings are found at boot.
119 
120           This is useful for discovering cases where the kernel is leaving
121           W+X mappings after applying NX, as such mappings are a security risk.
122 
123           Look for a message in dmesg output like this:
124 
125             x86/mm: Checked W+X mappings: passed, no W+X pages found.
126 
127           or like this, if the check failed:
128 
129             x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
130 
131           Note that even if the check fails, your kernel is possibly
132           still fine, as W+X mappings are not a security hole in
133           themselves, what they do is that they make the exploitation
134           of other unfixed kernel bugs easier.
135 
136           There is no runtime or memory usage effect of this option
137           once the kernel has booted up - it's a one time check.
138 
139           If in doubt, say "Y".
140 
141 config DEBUG_SET_MODULE_RONX
142         bool "Set loadable kernel module data as NX and text as RO"
143         depends on MODULES
144         ---help---
145           This option helps catch unintended modifications to loadable
146           kernel module's text and read-only data. It also prevents execution
147           of module data. Such protection may interfere with run-time code
148           patching and dynamic kernel tracing - and they might also protect
149           against certain classes of kernel exploits.
150           If in doubt, say "N".
151 
152 config DEBUG_NX_TEST
153         tristate "Testcase for the NX non-executable stack feature"
154         depends on DEBUG_KERNEL && m
155         ---help---
156           This option enables a testcase for the CPU NX capability
157           and the software setup of this feature.
158           If in doubt, say "N"
159 
160 config DOUBLEFAULT
161         default y
162         bool "Enable doublefault exception handler" if EXPERT
163         ---help---
164           This option allows trapping of rare doublefault exceptions that
165           would otherwise cause a system to silently reboot. Disabling this
166           option saves about 4k and might cause you much additional grey
167           hair.
168 
169 config DEBUG_TLBFLUSH
170         bool "Set upper limit of TLB entries to flush one-by-one"
171         depends on DEBUG_KERNEL
172         ---help---
173 
174         X86-only for now.
175 
176         This option allows the user to tune the amount of TLB entries the
177         kernel flushes one-by-one instead of doing a full TLB flush. In
178         certain situations, the former is cheaper. This is controlled by the
179         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
180         to -1, the code flushes the whole TLB unconditionally. Otherwise,
181         for positive values of it, the kernel will use single TLB entry
182         invalidating instructions according to the following formula:
183 
184         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
185 
186         If in doubt, say "N".
187 
188 config IOMMU_DEBUG
189         bool "Enable IOMMU debugging"
190         depends on GART_IOMMU && DEBUG_KERNEL
191         depends on X86_64
192         ---help---
193           Force the IOMMU to on even when you have less than 4GB of
194           memory and add debugging code. On overflow always panic. And
195           allow to enable IOMMU leak tracing. Can be disabled at boot
196           time with iommu=noforce. This will also enable scatter gather
197           list merging.  Currently not recommended for production
198           code. When you use it make sure you have a big enough
199           IOMMU/AGP aperture.  Most of the options enabled by this can
200           be set more finegrained using the iommu= command line
201           options. See Documentation/x86/x86_64/boot-options.txt for more
202           details.
203 
204 config IOMMU_STRESS
205         bool "Enable IOMMU stress-test mode"
206         ---help---
207           This option disables various optimizations in IOMMU related
208           code to do real stress testing of the IOMMU code. This option
209           will cause a performance drop and should only be enabled for
210           testing.
211 
212 config IOMMU_LEAK
213         bool "IOMMU leak tracing"
214         depends on IOMMU_DEBUG && DMA_API_DEBUG
215         ---help---
216           Add a simple leak tracer to the IOMMU code. This is useful when you
217           are debugging a buggy device driver that leaks IOMMU mappings.
218 
219 config HAVE_MMIOTRACE_SUPPORT
220         def_bool y
221 
222 config X86_DECODER_SELFTEST
223         bool "x86 instruction decoder selftest"
224         depends on DEBUG_KERNEL && KPROBES
225         depends on !COMPILE_TEST
226         ---help---
227          Perform x86 instruction decoder selftests at build time.
228          This option is useful for checking the sanity of x86 instruction
229          decoder code.
230          If unsure, say "N".
231 
232 #
233 # IO delay types:
234 #
235 
236 config IO_DELAY_TYPE_0X80
237         int
238         default "0"
239 
240 config IO_DELAY_TYPE_0XED
241         int
242         default "1"
243 
244 config IO_DELAY_TYPE_UDELAY
245         int
246         default "2"
247 
248 config IO_DELAY_TYPE_NONE
249         int
250         default "3"
251 
252 choice
253         prompt "IO delay type"
254         default IO_DELAY_0X80
255 
256 config IO_DELAY_0X80
257         bool "port 0x80 based port-IO delay [recommended]"
258         ---help---
259           This is the traditional Linux IO delay used for in/out_p.
260           It is the most tested hence safest selection here.
261 
262 config IO_DELAY_0XED
263         bool "port 0xed based port-IO delay"
264         ---help---
265           Use port 0xed as the IO delay. This frees up port 0x80 which is
266           often used as a hardware-debug port.
267 
268 config IO_DELAY_UDELAY
269         bool "udelay based port-IO delay"
270         ---help---
271           Use udelay(2) as the IO delay method. This provides the delay
272           while not having any side-effect on the IO port space.
273 
274 config IO_DELAY_NONE
275         bool "no port-IO delay"
276         ---help---
277           No port-IO delay. Will break on old boxes that require port-IO
278           delay for certain operations. Should work on most new machines.
279 
280 endchoice
281 
282 if IO_DELAY_0X80
283 config DEFAULT_IO_DELAY_TYPE
284         int
285         default IO_DELAY_TYPE_0X80
286 endif
287 
288 if IO_DELAY_0XED
289 config DEFAULT_IO_DELAY_TYPE
290         int
291         default IO_DELAY_TYPE_0XED
292 endif
293 
294 if IO_DELAY_UDELAY
295 config DEFAULT_IO_DELAY_TYPE
296         int
297         default IO_DELAY_TYPE_UDELAY
298 endif
299 
300 if IO_DELAY_NONE
301 config DEFAULT_IO_DELAY_TYPE
302         int
303         default IO_DELAY_TYPE_NONE
304 endif
305 
306 config DEBUG_BOOT_PARAMS
307         bool "Debug boot parameters"
308         depends on DEBUG_KERNEL
309         depends on DEBUG_FS
310         ---help---
311           This option will cause struct boot_params to be exported via debugfs.
312 
313 config CPA_DEBUG
314         bool "CPA self-test code"
315         depends on DEBUG_KERNEL
316         ---help---
317           Do change_page_attr() self-tests every 30 seconds.
318 
319 config OPTIMIZE_INLINING
320         bool "Allow gcc to uninline functions marked 'inline'"
321         ---help---
322           This option determines if the kernel forces gcc to inline the functions
323           developers have marked 'inline'. Doing so takes away freedom from gcc to
324           do what it thinks is best, which is desirable for the gcc 3.x series of
325           compilers. The gcc 4.x series have a rewritten inlining algorithm and
326           enabling this option will generate a smaller kernel there. Hopefully
327           this algorithm is so good that allowing gcc 4.x and above to make the
328           decision will become the default in the future. Until then this option
329           is there to test gcc for this.
330 
331           If unsure, say N.
332 
333 config DEBUG_ENTRY
334         bool "Debug low-level entry code"
335         depends on DEBUG_KERNEL
336         ---help---
337           This option enables sanity checks in x86's low-level entry code.
338           Some of these sanity checks may slow down kernel entries and
339           exits or otherwise impact performance.
340 
341           This is currently used to help test NMI code.
342 
343           If unsure, say N.
344 
345 config DEBUG_NMI_SELFTEST
346         bool "NMI Selftest"
347         depends on DEBUG_KERNEL && X86_LOCAL_APIC
348         ---help---
349           Enabling this option turns on a quick NMI selftest to verify
350           that the NMI behaves correctly.
351 
352           This might help diagnose strange hangs that rely on NMI to
353           function properly.
354 
355           If unsure, say N.
356 
357 config DEBUG_IMR_SELFTEST
358         bool "Isolated Memory Region self test"
359         default n
360         depends on INTEL_IMR
361         ---help---
362           This option enables automated sanity testing of the IMR code.
363           Some simple tests are run to verify IMR bounds checking, alignment
364           and overlapping. This option is really only useful if you are
365           debugging an IMR memory map or are modifying the IMR code and want to
366           test your changes.
367 
368           If unsure say N here.
369 
370 config X86_DEBUG_STATIC_CPU_HAS
371         bool "Debug alternatives"
372         depends on DEBUG_KERNEL
373         ---help---
374           This option causes additional code to be generated which
375           fails if static_cpu_has() is used before alternatives have
376           run.
377 
378           If unsure, say N.
379 
380 config X86_DEBUG_FPU
381         bool "Debug the x86 FPU code"
382         depends on DEBUG_KERNEL
383         default y
384         ---help---
385           If this option is enabled then there will be extra sanity
386           checks and (boot time) debug printouts added to the kernel.
387           This debugging adds some small amount of runtime overhead
388           to the kernel.
389 
390           If unsure, say N.
391 
392 config PUNIT_ATOM_DEBUG
393         tristate "ATOM Punit debug driver"
394         select DEBUG_FS
395         select IOSF_MBI
396         ---help---
397           This is a debug driver, which gets the power states
398           of all Punit North Complex devices. The power states of
399           each device is exposed as part of the debugfs interface.
400           The current power state can be read from
401           /sys/kernel/debug/punit_atom/dev_power_state
402 
403 endmenu

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