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         bool "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         default y
 117         select X86_PTDUMP_CORE
 118         ---help---
 119           Generate a warning if any W+X mappings are found at boot.
 120
 121           This is useful for discovering cases where the kernel is leaving
 122           W+X mappings after applying NX, as such mappings are a security risk.
 123
 124           Look for a message in dmesg output like this:
 125
 126             x86/mm: Checked W+X mappings: passed, no W+X pages found.
 127
 128           or like this, if the check failed:
 129
 130             x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
 131
 132           Note that even if the check fails, your kernel is possibly
 133           still fine, as W+X mappings are not a security hole in
 134           themselves, what they do is that they make the exploitation
 135           of other unfixed kernel bugs easier.
 136
 137           There is no runtime or memory usage effect of this option
 138           once the kernel has booted up - it's a one time check.
 139
 140           If in doubt, say "Y".
 141
 142 config DEBUG_SET_MODULE_RONX
 143         bool "Set loadable kernel module data as NX and text as RO"
 144         depends on MODULES
 145         ---help---
 146           This option helps catch unintended modifications to loadable
 147           kernel module's text and read-only data. It also prevents execution
 148           of module data. Such protection may interfere with run-time code
 149           patching and dynamic kernel tracing - and they might also protect
 150           against certain classes of kernel exploits.
 151           If in doubt, say "N".
 152
 153 config DEBUG_NX_TEST
 154         tristate "Testcase for the NX non-executable stack feature"
 155         depends on DEBUG_KERNEL && m
 156         ---help---
 157           This option enables a testcase for the CPU NX capability
 158           and the software setup of this feature.
 159           If in doubt, say "N"
 160
 161 config DOUBLEFAULT
 162         default y
 163         bool "Enable doublefault exception handler" if EXPERT
 164         ---help---
 165           This option allows trapping of rare doublefault exceptions that
 166           would otherwise cause a system to silently reboot. Disabling this
 167           option saves about 4k and might cause you much additional grey
 168           hair.
 169
 170 config DEBUG_TLBFLUSH
 171         bool "Set upper limit of TLB entries to flush one-by-one"
 172         depends on DEBUG_KERNEL
 173         ---help---
 174
 175         X86-only for now.
 176
 177         This option allows the user to tune the amount of TLB entries the
 178         kernel flushes one-by-one instead of doing a full TLB flush. In
 179         certain situations, the former is cheaper. This is controlled by the
 180         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 181         to -1, the code flushes the whole TLB unconditionally. Otherwise,
 182         for positive values of it, the kernel will use single TLB entry
 183         invalidating instructions according to the following formula:
 184
 185         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 186
 187         If in doubt, say "N".
 188
 189 config IOMMU_DEBUG
 190         bool "Enable IOMMU debugging"
 191         depends on GART_IOMMU && DEBUG_KERNEL
 192         depends on X86_64
 193         ---help---
 194           Force the IOMMU to on even when you have less than 4GB of
 195           memory and add debugging code. On overflow always panic. And
 196           allow to enable IOMMU leak tracing. Can be disabled at boot
 197           time with iommu=noforce. This will also enable scatter gather
 198           list merging.  Currently not recommended for production
 199           code. When you use it make sure you have a big enough
 200           IOMMU/AGP aperture.  Most of the options enabled by this can
 201           be set more finegrained using the iommu= command line
 202           options. See Documentation/x86/x86_64/boot-options.txt for more
 203           details.
 204
 205 config IOMMU_STRESS
 206         bool "Enable IOMMU stress-test mode"
 207         ---help---
 208           This option disables various optimizations in IOMMU related
 209           code to do real stress testing of the IOMMU code. This option
 210           will cause a performance drop and should only be enabled for
 211           testing.
 212
 213 config IOMMU_LEAK
 214         bool "IOMMU leak tracing"
 215         depends on IOMMU_DEBUG && DMA_API_DEBUG
 216         ---help---
 217           Add a simple leak tracer to the IOMMU code. This is useful when you
 218           are debugging a buggy device driver that leaks IOMMU mappings.
 219
 220 config HAVE_MMIOTRACE_SUPPORT
 221         def_bool y
 222
 223 config X86_DECODER_SELFTEST
 224         bool "x86 instruction decoder selftest"
 225         depends on DEBUG_KERNEL && KPROBES
 226         depends on !COMPILE_TEST
 227         ---help---
 228          Perform x86 instruction decoder selftests at build time.
 229          This option is useful for checking the sanity of x86 instruction
 230          decoder code.
 231          If unsure, say "N".
 232
 233 #
 234 # IO delay types:
 235 #
 236
 237 config IO_DELAY_TYPE_0X80
 238         int
 239         default "0"
 240
 241 config IO_DELAY_TYPE_0XED
 242         int
 243         default "1"
 244
 245 config IO_DELAY_TYPE_UDELAY
 246         int
 247         default "2"
 248
 249 config IO_DELAY_TYPE_NONE
 250         int
 251         default "3"
 252
 253 choice
 254         prompt "IO delay type"
 255         default IO_DELAY_0X80
 256
 257 config IO_DELAY_0X80
 258         bool "port 0x80 based port-IO delay [recommended]"
 259         ---help---
 260           This is the traditional Linux IO delay used for in/out_p.
 261           It is the most tested hence safest selection here.
 262
 263 config IO_DELAY_0XED
 264         bool "port 0xed based port-IO delay"
 265         ---help---
 266           Use port 0xed as the IO delay. This frees up port 0x80 which is
 267           often used as a hardware-debug port.
 268
 269 config IO_DELAY_UDELAY
 270         bool "udelay based port-IO delay"
 271         ---help---
 272           Use udelay(2) as the IO delay method. This provides the delay
 273           while not having any side-effect on the IO port space.
 274
 275 config IO_DELAY_NONE
 276         bool "no port-IO delay"
 277         ---help---
 278           No port-IO delay. Will break on old boxes that require port-IO
 279           delay for certain operations. Should work on most new machines.
 280
 281 endchoice
 282
 283 if IO_DELAY_0X80
 284 config DEFAULT_IO_DELAY_TYPE
 285         int
 286         default IO_DELAY_TYPE_0X80
 287 endif
 288
 289 if IO_DELAY_0XED
 290 config DEFAULT_IO_DELAY_TYPE
 291         int
 292         default IO_DELAY_TYPE_0XED
 293 endif
 294
 295 if IO_DELAY_UDELAY
 296 config DEFAULT_IO_DELAY_TYPE
 297         int
 298         default IO_DELAY_TYPE_UDELAY
 299 endif
 300
 301 if IO_DELAY_NONE
 302 config DEFAULT_IO_DELAY_TYPE
 303         int
 304         default IO_DELAY_TYPE_NONE
 305 endif
 306
 307 config DEBUG_BOOT_PARAMS
 308         bool "Debug boot parameters"
 309         depends on DEBUG_KERNEL
 310         depends on DEBUG_FS
 311         ---help---
 312           This option will cause struct boot_params to be exported via debugfs.
 313
 314 config CPA_DEBUG
 315         bool "CPA self-test code"
 316         depends on DEBUG_KERNEL
 317         ---help---
 318           Do change_page_attr() self-tests every 30 seconds.
 319
 320 config OPTIMIZE_INLINING
 321         bool "Allow gcc to uninline functions marked 'inline'"
 322         ---help---
 323           This option determines if the kernel forces gcc to inline the functions
 324           developers have marked 'inline'. Doing so takes away freedom from gcc to
 325           do what it thinks is best, which is desirable for the gcc 3.x series of
 326           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 327           enabling this option will generate a smaller kernel there. Hopefully
 328           this algorithm is so good that allowing gcc 4.x and above to make the
 329           decision will become the default in the future. Until then this option
 330           is there to test gcc for this.
 331
 332           If unsure, say N.
 333
 334 config DEBUG_ENTRY
 335         bool "Debug low-level entry code"
 336         depends on DEBUG_KERNEL
 337         ---help---
 338           This option enables sanity checks in x86's low-level entry code.
 339           Some of these sanity checks may slow down kernel entries and
 340           exits or otherwise impact performance.
 341
 342           This is currently used to help test NMI code.
 343
 344           If unsure, say N.
 345
 346 config DEBUG_NMI_SELFTEST
 347         bool "NMI Selftest"
 348         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 349         ---help---
 350           Enabling this option turns on a quick NMI selftest to verify
 351           that the NMI behaves correctly.
 352
 353           This might help diagnose strange hangs that rely on NMI to
 354           function properly.
 355
 356           If unsure, say N.
 357
 358 config DEBUG_IMR_SELFTEST
 359         bool "Isolated Memory Region self test"
 360         default n
 361         depends on INTEL_IMR
 362         ---help---
 363           This option enables automated sanity testing of the IMR code.
 364           Some simple tests are run to verify IMR bounds checking, alignment
 365           and overlapping. This option is really only useful if you are
 366           debugging an IMR memory map or are modifying the IMR code and want to
 367           test your changes.
 368
 369           If unsure say N here.
 370
 371 config X86_DEBUG_STATIC_CPU_HAS
 372         bool "Debug alternatives"
 373         depends on DEBUG_KERNEL
 374         ---help---
 375           This option causes additional code to be generated which
 376           fails if static_cpu_has() is used before alternatives have
 377           run.
 378
 379           If unsure, say N.
 380
 381 config X86_DEBUG_FPU
 382         bool "Debug the x86 FPU code"
 383         depends on DEBUG_KERNEL
 384         default y
 385         ---help---
 386           If this option is enabled then there will be extra sanity
 387           checks and (boot time) debug printouts added to the kernel.
 388           This debugging adds some small amount of runtime overhead
 389           to the kernel.
 390
 391           If unsure, say N.
 392
 393 config PUNIT_ATOM_DEBUG
 394         tristate "ATOM Punit debug driver"
 395         select DEBUG_FS
 396         select IOSF_MBI
 397         ---help---
 398           This is a debug driver, which gets the power states
 399           of all Punit North Complex devices. The power states of
 400           each device is exposed as part of the debugfs interface.
 401           The current power state can be read from
 402           /sys/kernel/debug/punit_atom/dev_power_state
 403
 404 endmenu