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