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 EARLY_PRINTK_USB
   9         bool
  10
  11 config X86_VERBOSE_BOOTUP
  12         bool "Enable verbose x86 bootup info messages"
  13         default y
  14         ---help---
  15           Enables the informational output from the decompression stage
  16           (e.g. bzImage) of the boot. If you disable this you will still
  17           see errors. Disable this if you want silent bootup.
  18
  19 config EARLY_PRINTK
  20         bool "Early printk" if EXPERT
  21         default y
  22         ---help---
  23           Write kernel log output directly into the VGA buffer or to a serial
  24           port.
  25
  26           This is useful for kernel debugging when your machine crashes very
  27           early before the console code is initialized. For normal operation
  28           it is not recommended because it looks ugly and doesn't cooperate
  29           with klogd/syslogd or the X server. You should normally say N here,
  30           unless you want to debug such a crash.
  31
  32 config EARLY_PRINTK_DBGP
  33         bool "Early printk via EHCI debug port"
  34         depends on EARLY_PRINTK && PCI
  35         select EARLY_PRINTK_USB
  36         ---help---
  37           Write kernel log output directly into the EHCI debug port.
  38
  39           This is useful for kernel debugging when your machine crashes very
  40           early before the console code is initialized. For normal operation
  41           it is not recommended because it looks ugly and doesn't cooperate
  42           with klogd/syslogd or the X server. You should normally say N here,
  43           unless you want to debug such a crash. You need usb debug device.
  44
  45 config EARLY_PRINTK_EFI
  46         bool "Early printk via the EFI framebuffer"
  47         depends on EFI && EARLY_PRINTK
  48         select FONT_SUPPORT
  49         ---help---
  50           Write kernel log output directly into the EFI framebuffer.
  51
  52           This is useful for kernel debugging when your machine crashes very
  53           early before the console code is initialized.
  54
  55 config EARLY_PRINTK_USB_XDBC
  56         bool "Early printk via the xHCI debug port"
  57         depends on EARLY_PRINTK && PCI
  58         select EARLY_PRINTK_USB
  59         ---help---
  60           Write kernel log output directly into the xHCI debug port.
  61
  62           One use for this feature is kernel debugging, for example when your
  63           machine crashes very early before the regular console code is
  64           initialized. Other uses include simpler, lockless logging instead of
  65           a full-blown printk console driver + klogd.
  66
  67           For normal production environments this is normally not recommended,
  68           because it doesn't feed events into klogd/syslogd and doesn't try to
  69           print anything on the screen.
  70
  71           You should normally say N here, unless you want to debug early
  72           crashes or need a very simple printk logging facility.
  73
  74 config X86_PTDUMP_CORE
  75         def_bool n
  76
  77 config X86_PTDUMP
  78         tristate "Export kernel pagetable layout to userspace via debugfs"
  79         depends on DEBUG_KERNEL
  80         select DEBUG_FS
  81         select X86_PTDUMP_CORE
  82         ---help---
  83           Say Y here if you want to show the kernel pagetable layout in a
  84           debugfs file. This information is only useful for kernel developers
  85           who are working in architecture specific areas of the kernel.
  86           It is probably not a good idea to enable this feature in a production
  87           kernel.
  88           If in doubt, say "N"
  89
  90 config EFI_PGT_DUMP
  91         bool "Dump the EFI pagetable"
  92         depends on EFI
  93         select X86_PTDUMP_CORE
  94         ---help---
  95           Enable this if you want to dump the EFI page table before
  96           enabling virtual mode. This can be used to debug miscellaneous
  97           issues with the mapping of the EFI runtime regions into that
  98           table.
  99
 100 config DEBUG_WX
 101         bool "Warn on W+X mappings at boot"
 102         select X86_PTDUMP_CORE
 103         ---help---
 104           Generate a warning if any W+X mappings are found at boot.
 105
 106           This is useful for discovering cases where the kernel is leaving
 107           W+X mappings after applying NX, as such mappings are a security risk.
 108
 109           Look for a message in dmesg output like this:
 110
 111             x86/mm: Checked W+X mappings: passed, no W+X pages found.
 112
 113           or like this, if the check failed:
 114
 115             x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
 116
 117           Note that even if the check fails, your kernel is possibly
 118           still fine, as W+X mappings are not a security hole in
 119           themselves, what they do is that they make the exploitation
 120           of other unfixed kernel bugs easier.
 121
 122           There is no runtime or memory usage effect of this option
 123           once the kernel has booted up - it's a one time check.
 124
 125           If in doubt, say "Y".
 126
 127 config DOUBLEFAULT
 128         default y
 129         bool "Enable doublefault exception handler" if EXPERT
 130         ---help---
 131           This option allows trapping of rare doublefault exceptions that
 132           would otherwise cause a system to silently reboot. Disabling this
 133           option saves about 4k and might cause you much additional grey
 134           hair.
 135
 136 config DEBUG_TLBFLUSH
 137         bool "Set upper limit of TLB entries to flush one-by-one"
 138         depends on DEBUG_KERNEL
 139         ---help---
 140
 141         X86-only for now.
 142
 143         This option allows the user to tune the amount of TLB entries the
 144         kernel flushes one-by-one instead of doing a full TLB flush. In
 145         certain situations, the former is cheaper. This is controlled by the
 146         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 147         to -1, the code flushes the whole TLB unconditionally. Otherwise,
 148         for positive values of it, the kernel will use single TLB entry
 149         invalidating instructions according to the following formula:
 150
 151         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 152
 153         If in doubt, say "N".
 154
 155 config IOMMU_DEBUG
 156         bool "Enable IOMMU debugging"
 157         depends on GART_IOMMU && DEBUG_KERNEL
 158         depends on X86_64
 159         ---help---
 160           Force the IOMMU to on even when you have less than 4GB of
 161           memory and add debugging code. On overflow always panic. And
 162           allow to enable IOMMU leak tracing. Can be disabled at boot
 163           time with iommu=noforce. This will also enable scatter gather
 164           list merging.  Currently not recommended for production
 165           code. When you use it make sure you have a big enough
 166           IOMMU/AGP aperture.  Most of the options enabled by this can
 167           be set more finegrained using the iommu= command line
 168           options. See Documentation/x86/x86_64/boot-options.txt for more
 169           details.
 170
 171 config IOMMU_STRESS
 172         bool "Enable IOMMU stress-test mode"
 173         ---help---
 174           This option disables various optimizations in IOMMU related
 175           code to do real stress testing of the IOMMU code. This option
 176           will cause a performance drop and should only be enabled for
 177           testing.
 178
 179 config IOMMU_LEAK
 180         bool "IOMMU leak tracing"
 181         depends on IOMMU_DEBUG && DMA_API_DEBUG
 182         ---help---
 183           Add a simple leak tracer to the IOMMU code. This is useful when you
 184           are debugging a buggy device driver that leaks IOMMU mappings.
 185
 186 config HAVE_MMIOTRACE_SUPPORT
 187         def_bool y
 188
 189 config X86_DECODER_SELFTEST
 190         bool "x86 instruction decoder selftest"
 191         depends on DEBUG_KERNEL && KPROBES
 192         depends on !COMPILE_TEST
 193         ---help---
 194          Perform x86 instruction decoder selftests at build time.
 195          This option is useful for checking the sanity of x86 instruction
 196          decoder code.
 197          If unsure, say "N".
 198
 199 #
 200 # IO delay types:
 201 #
 202
 203 config IO_DELAY_TYPE_0X80
 204         int
 205         default "0"
 206
 207 config IO_DELAY_TYPE_0XED
 208         int
 209         default "1"
 210
 211 config IO_DELAY_TYPE_UDELAY
 212         int
 213         default "2"
 214
 215 config IO_DELAY_TYPE_NONE
 216         int
 217         default "3"
 218
 219 choice
 220         prompt "IO delay type"
 221         default IO_DELAY_0X80
 222
 223 config IO_DELAY_0X80
 224         bool "port 0x80 based port-IO delay [recommended]"
 225         ---help---
 226           This is the traditional Linux IO delay used for in/out_p.
 227           It is the most tested hence safest selection here.
 228
 229 config IO_DELAY_0XED
 230         bool "port 0xed based port-IO delay"
 231         ---help---
 232           Use port 0xed as the IO delay. This frees up port 0x80 which is
 233           often used as a hardware-debug port.
 234
 235 config IO_DELAY_UDELAY
 236         bool "udelay based port-IO delay"
 237         ---help---
 238           Use udelay(2) as the IO delay method. This provides the delay
 239           while not having any side-effect on the IO port space.
 240
 241 config IO_DELAY_NONE
 242         bool "no port-IO delay"
 243         ---help---
 244           No port-IO delay. Will break on old boxes that require port-IO
 245           delay for certain operations. Should work on most new machines.
 246
 247 endchoice
 248
 249 if IO_DELAY_0X80
 250 config DEFAULT_IO_DELAY_TYPE
 251         int
 252         default IO_DELAY_TYPE_0X80
 253 endif
 254
 255 if IO_DELAY_0XED
 256 config DEFAULT_IO_DELAY_TYPE
 257         int
 258         default IO_DELAY_TYPE_0XED
 259 endif
 260
 261 if IO_DELAY_UDELAY
 262 config DEFAULT_IO_DELAY_TYPE
 263         int
 264         default IO_DELAY_TYPE_UDELAY
 265 endif
 266
 267 if IO_DELAY_NONE
 268 config DEFAULT_IO_DELAY_TYPE
 269         int
 270         default IO_DELAY_TYPE_NONE
 271 endif
 272
 273 config DEBUG_BOOT_PARAMS
 274         bool "Debug boot parameters"
 275         depends on DEBUG_KERNEL
 276         depends on DEBUG_FS
 277         ---help---
 278           This option will cause struct boot_params to be exported via debugfs.
 279
 280 config CPA_DEBUG
 281         bool "CPA self-test code"
 282         depends on DEBUG_KERNEL
 283         ---help---
 284           Do change_page_attr() self-tests every 30 seconds.
 285
 286 config OPTIMIZE_INLINING
 287         bool "Allow gcc to uninline functions marked 'inline'"
 288         ---help---
 289           This option determines if the kernel forces gcc to inline the functions
 290           developers have marked 'inline'. Doing so takes away freedom from gcc to
 291           do what it thinks is best, which is desirable for the gcc 3.x series of
 292           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 293           enabling this option will generate a smaller kernel there. Hopefully
 294           this algorithm is so good that allowing gcc 4.x and above to make the
 295           decision will become the default in the future. Until then this option
 296           is there to test gcc for this.
 297
 298           If unsure, say N.
 299
 300 config DEBUG_ENTRY
 301         bool "Debug low-level entry code"
 302         depends on DEBUG_KERNEL
 303         ---help---
 304           This option enables sanity checks in x86's low-level entry code.
 305           Some of these sanity checks may slow down kernel entries and
 306           exits or otherwise impact performance.
 307
 308           If unsure, say N.
 309
 310 config DEBUG_NMI_SELFTEST
 311         bool "NMI Selftest"
 312         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 313         ---help---
 314           Enabling this option turns on a quick NMI selftest to verify
 315           that the NMI behaves correctly.
 316
 317           This might help diagnose strange hangs that rely on NMI to
 318           function properly.
 319
 320           If unsure, say N.
 321
 322 config DEBUG_IMR_SELFTEST
 323         bool "Isolated Memory Region self test"
 324         default n
 325         depends on INTEL_IMR
 326         ---help---
 327           This option enables automated sanity testing of the IMR code.
 328           Some simple tests are run to verify IMR bounds checking, alignment
 329           and overlapping. This option is really only useful if you are
 330           debugging an IMR memory map or are modifying the IMR code and want to
 331           test your changes.
 332
 333           If unsure say N here.
 334
 335 config X86_DEBUG_FPU
 336         bool "Debug the x86 FPU code"
 337         depends on DEBUG_KERNEL
 338         default y
 339         ---help---
 340           If this option is enabled then there will be extra sanity
 341           checks and (boot time) debug printouts added to the kernel.
 342           This debugging adds some small amount of runtime overhead
 343           to the kernel.
 344
 345           If unsure, say N.
 346
 347 config PUNIT_ATOM_DEBUG
 348         tristate "ATOM Punit debug driver"
 349         depends on PCI
 350         select DEBUG_FS
 351         select IOSF_MBI
 352         ---help---
 353           This is a debug driver, which gets the power states
 354           of all Punit North Complex devices. The power states of
 355           each device is exposed as part of the debugfs interface.
 356           The current power state can be read from
 357           /sys/kernel/debug/punit_atom/dev_power_state
 358
 359 choice
 360         prompt "Choose kernel unwinder"
 361         default FRAME_POINTER_UNWINDER
 362         ---help---
 363           This determines which method will be used for unwinding kernel stack
 364           traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
 365           livepatch, lockdep, and more.
 366
 367 config FRAME_POINTER_UNWINDER
 368         bool "Frame pointer unwinder"
 369         select FRAME_POINTER
 370         ---help---
 371           This option enables the frame pointer unwinder for unwinding kernel
 372           stack traces.
 373
 374           The unwinder itself is fast and it uses less RAM than the ORC
 375           unwinder, but the kernel text size will grow by ~3% and the kernel's
 376           overall performance will degrade by roughly 5-10%.
 377
 378           This option is recommended if you want to use the livepatch
 379           consistency model, as this is currently the only way to get a
 380           reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE).
 381
 382 config ORC_UNWINDER
 383         bool "ORC unwinder"
 384         depends on X86_64
 385         select STACK_VALIDATION
 386         ---help---
 387           This option enables the ORC (Oops Rewind Capability) unwinder for
 388           unwinding kernel stack traces.  It uses a custom data format which is
 389           a simplified version of the DWARF Call Frame Information standard.
 390
 391           This unwinder is more accurate across interrupt entry frames than the
 392           frame pointer unwinder.  It also enables a 5-10% performance
 393           improvement across the entire kernel compared to frame pointers.
 394
 395           Enabling this option will increase the kernel's runtime memory usage
 396           by roughly 2-4MB, depending on your kernel config.
 397
 398 config GUESS_UNWINDER
 399         bool "Guess unwinder"
 400         depends on EXPERT
 401         ---help---
 402           This option enables the "guess" unwinder for unwinding kernel stack
 403           traces.  It scans the stack and reports every kernel text address it
 404           finds.  Some of the addresses it reports may be incorrect.
 405
 406           While this option often produces false positives, it can still be
 407           useful in many cases.  Unlike the other unwinders, it has no runtime
 408           overhead.
 409
 410 endchoice
 411
 412 config FRAME_POINTER
 413         depends on !ORC_UNWINDER && !GUESS_UNWINDER
 414         bool
 415
 416 endmenu