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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_INTEL_MID
 47         bool "Early printk for Intel MID platform support"
 48         depends on EARLY_PRINTK && X86_INTEL_MID
 49 
 50 config EARLY_PRINTK_DBGP
 51         bool "Early printk via EHCI debug port"
 52         depends on EARLY_PRINTK && PCI
 53         ---help---
 54           Write kernel log output directly into the EHCI debug port.
 55 
 56           This is useful for kernel debugging when your machine crashes very
 57           early before the console code is initialized. For normal operation
 58           it is not recommended because it looks ugly and doesn't cooperate
 59           with klogd/syslogd or the X server. You should normally N here,
 60           unless you want to debug such a crash. You need usb debug device.
 61 
 62 config EARLY_PRINTK_EFI
 63         bool "Early printk via the EFI framebuffer"
 64         depends on EFI && EARLY_PRINTK
 65         select FONT_SUPPORT
 66         ---help---
 67           Write kernel log output directly into the EFI framebuffer.
 68 
 69           This is useful for kernel debugging when your machine crashes very
 70           early before the console code is initialized.
 71 
 72 config X86_PTDUMP
 73         bool "Export kernel pagetable layout to userspace via debugfs"
 74         depends on DEBUG_KERNEL
 75         select DEBUG_FS
 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 && X86_PTDUMP
 87         ---help---
 88           Enable this if you want to dump the EFI page table before
 89           enabling virtual mode. This can be used to debug miscellaneous
 90           issues with the mapping of the EFI runtime regions into that
 91           table.
 92 
 93 config DEBUG_RODATA
 94         bool "Write protect kernel read-only data structures"
 95         default y
 96         depends on DEBUG_KERNEL
 97         ---help---
 98           Mark the kernel read-only data as write-protected in the pagetables,
 99           in order to catch accidental (and incorrect) writes to such const
100           data. This is recommended so that we can catch kernel bugs sooner.
101           If in doubt, say "Y".
102 
103 config DEBUG_RODATA_TEST
104         bool "Testcase for the DEBUG_RODATA feature"
105         depends on DEBUG_RODATA
106         default y
107         ---help---
108           This option enables a testcase for the DEBUG_RODATA
109           feature as well as for the change_page_attr() infrastructure.
110           If in doubt, say "N"
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_NMI_SELFTEST
305         bool "NMI Selftest"
306         depends on DEBUG_KERNEL && X86_LOCAL_APIC
307         ---help---
308           Enabling this option turns on a quick NMI selftest to verify
309           that the NMI behaves correctly.
310 
311           This might help diagnose strange hangs that rely on NMI to
312           function properly.
313 
314           If unsure, say N.
315 
316 config X86_DEBUG_STATIC_CPU_HAS
317         bool "Debug alternatives"
318         depends on DEBUG_KERNEL
319         ---help---
320           This option causes additional code to be generated which
321           fails if static_cpu_has() is used before alternatives have
322           run.
323 
324           If unsure, say N.
325 
326 endmenu

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