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         tristate "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