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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 DEBUG_RODATA
 85         bool "Write protect kernel read-only data structures"
 86         default y
 87         depends on DEBUG_KERNEL
 88         ---help---
 89           Mark the kernel read-only data as write-protected in the pagetables,
 90           in order to catch accidental (and incorrect) writes to such const
 91           data. This is recommended so that we can catch kernel bugs sooner.
 92           If in doubt, say "Y".
 93 
 94 config DEBUG_RODATA_TEST
 95         bool "Testcase for the DEBUG_RODATA feature"
 96         depends on DEBUG_RODATA
 97         default y
 98         ---help---
 99           This option enables a testcase for the DEBUG_RODATA
100           feature as well as for the change_page_attr() infrastructure.
101           If in doubt, say "N"
102 
103 config DEBUG_SET_MODULE_RONX
104         bool "Set loadable kernel module data as NX and text as RO"
105         depends on MODULES
106         ---help---
107           This option helps catch unintended modifications to loadable
108           kernel module's text and read-only data. It also prevents execution
109           of module data. Such protection may interfere with run-time code
110           patching and dynamic kernel tracing - and they might also protect
111           against certain classes of kernel exploits.
112           If in doubt, say "N".
113 
114 config DEBUG_NX_TEST
115         tristate "Testcase for the NX non-executable stack feature"
116         depends on DEBUG_KERNEL && m
117         ---help---
118           This option enables a testcase for the CPU NX capability
119           and the software setup of this feature.
120           If in doubt, say "N"
121 
122 config DOUBLEFAULT
123         default y
124         bool "Enable doublefault exception handler" if EXPERT
125         ---help---
126           This option allows trapping of rare doublefault exceptions that
127           would otherwise cause a system to silently reboot. Disabling this
128           option saves about 4k and might cause you much additional grey
129           hair.
130 
131 config DEBUG_TLBFLUSH
132         bool "Set upper limit of TLB entries to flush one-by-one"
133         depends on DEBUG_KERNEL
134         ---help---
135 
136         X86-only for now.
137 
138         This option allows the user to tune the amount of TLB entries the
139         kernel flushes one-by-one instead of doing a full TLB flush. In
140         certain situations, the former is cheaper. This is controlled by the
141         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
142         to -1, the code flushes the whole TLB unconditionally. Otherwise,
143         for positive values of it, the kernel will use single TLB entry
144         invalidating instructions according to the following formula:
145 
146         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
147 
148         If in doubt, say "N".
149 
150 config IOMMU_DEBUG
151         bool "Enable IOMMU debugging"
152         depends on GART_IOMMU && DEBUG_KERNEL
153         depends on X86_64
154         ---help---
155           Force the IOMMU to on even when you have less than 4GB of
156           memory and add debugging code. On overflow always panic. And
157           allow to enable IOMMU leak tracing. Can be disabled at boot
158           time with iommu=noforce. This will also enable scatter gather
159           list merging.  Currently not recommended for production
160           code. When you use it make sure you have a big enough
161           IOMMU/AGP aperture.  Most of the options enabled by this can
162           be set more finegrained using the iommu= command line
163           options. See Documentation/x86/x86_64/boot-options.txt for more
164           details.
165 
166 config IOMMU_STRESS
167         bool "Enable IOMMU stress-test mode"
168         ---help---
169           This option disables various optimizations in IOMMU related
170           code to do real stress testing of the IOMMU code. This option
171           will cause a performance drop and should only be enabled for
172           testing.
173 
174 config IOMMU_LEAK
175         bool "IOMMU leak tracing"
176         depends on IOMMU_DEBUG && DMA_API_DEBUG
177         ---help---
178           Add a simple leak tracer to the IOMMU code. This is useful when you
179           are debugging a buggy device driver that leaks IOMMU mappings.
180 
181 config HAVE_MMIOTRACE_SUPPORT
182         def_bool y
183 
184 config X86_DECODER_SELFTEST
185         bool "x86 instruction decoder selftest"
186         depends on DEBUG_KERNEL && KPROBES
187         depends on !COMPILE_TEST
188         ---help---
189          Perform x86 instruction decoder selftests at build time.
190          This option is useful for checking the sanity of x86 instruction
191          decoder code.
192          If unsure, say "N".
193 
194 #
195 # IO delay types:
196 #
197 
198 config IO_DELAY_TYPE_0X80
199         int
200         default "0"
201 
202 config IO_DELAY_TYPE_0XED
203         int
204         default "1"
205 
206 config IO_DELAY_TYPE_UDELAY
207         int
208         default "2"
209 
210 config IO_DELAY_TYPE_NONE
211         int
212         default "3"
213 
214 choice
215         prompt "IO delay type"
216         default IO_DELAY_0X80
217 
218 config IO_DELAY_0X80
219         bool "port 0x80 based port-IO delay [recommended]"
220         ---help---
221           This is the traditional Linux IO delay used for in/out_p.
222           It is the most tested hence safest selection here.
223 
224 config IO_DELAY_0XED
225         bool "port 0xed based port-IO delay"
226         ---help---
227           Use port 0xed as the IO delay. This frees up port 0x80 which is
228           often used as a hardware-debug port.
229 
230 config IO_DELAY_UDELAY
231         bool "udelay based port-IO delay"
232         ---help---
233           Use udelay(2) as the IO delay method. This provides the delay
234           while not having any side-effect on the IO port space.
235 
236 config IO_DELAY_NONE
237         bool "no port-IO delay"
238         ---help---
239           No port-IO delay. Will break on old boxes that require port-IO
240           delay for certain operations. Should work on most new machines.
241 
242 endchoice
243 
244 if IO_DELAY_0X80
245 config DEFAULT_IO_DELAY_TYPE
246         int
247         default IO_DELAY_TYPE_0X80
248 endif
249 
250 if IO_DELAY_0XED
251 config DEFAULT_IO_DELAY_TYPE
252         int
253         default IO_DELAY_TYPE_0XED
254 endif
255 
256 if IO_DELAY_UDELAY
257 config DEFAULT_IO_DELAY_TYPE
258         int
259         default IO_DELAY_TYPE_UDELAY
260 endif
261 
262 if IO_DELAY_NONE
263 config DEFAULT_IO_DELAY_TYPE
264         int
265         default IO_DELAY_TYPE_NONE
266 endif
267 
268 config DEBUG_BOOT_PARAMS
269         bool "Debug boot parameters"
270         depends on DEBUG_KERNEL
271         depends on DEBUG_FS
272         ---help---
273           This option will cause struct boot_params to be exported via debugfs.
274 
275 config CPA_DEBUG
276         bool "CPA self-test code"
277         depends on DEBUG_KERNEL
278         ---help---
279           Do change_page_attr() self-tests every 30 seconds.
280 
281 config OPTIMIZE_INLINING
282         bool "Allow gcc to uninline functions marked 'inline'"
283         ---help---
284           This option determines if the kernel forces gcc to inline the functions
285           developers have marked 'inline'. Doing so takes away freedom from gcc to
286           do what it thinks is best, which is desirable for the gcc 3.x series of
287           compilers. The gcc 4.x series have a rewritten inlining algorithm and
288           enabling this option will generate a smaller kernel there. Hopefully
289           this algorithm is so good that allowing gcc 4.x and above to make the
290           decision will become the default in the future. Until then this option
291           is there to test gcc for this.
292 
293           If unsure, say N.
294 
295 config DEBUG_NMI_SELFTEST
296         bool "NMI Selftest"
297         depends on DEBUG_KERNEL && X86_LOCAL_APIC
298         ---help---
299           Enabling this option turns on a quick NMI selftest to verify
300           that the NMI behaves correctly.
301 
302           This might help diagnose strange hangs that rely on NMI to
303           function properly.
304 
305           If unsure, say N.
306 
307 config X86_DEBUG_STATIC_CPU_HAS
308         bool "Debug alternatives"
309         depends on DEBUG_KERNEL
310         ---help---
311           This option causes additional code to be generated which
312           fails if static_cpu_has() is used before alternatives have
313           run.
314 
315           If unsure, say N.
316 
317 endmenu

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