arch/x86/Kconfig.debug

   1 # SPDX-License-Identifier: GPL-2.0
   2 menu "Kernel hacking"
   3
   4 config TRACE_IRQFLAGS_SUPPORT
   5         def_bool y
   6
   7 source "lib/Kconfig.debug"
   8
   9 config EARLY_PRINTK_USB
  10         bool
  11
  12 config X86_VERBOSE_BOOTUP
  13         bool "Enable verbose x86 bootup info messages"
  14         default y
  15         ---help---
  16           Enables the informational output from the decompression stage
  17           (e.g. bzImage) of the boot. If you disable this you will still
  18           see errors. Disable this if you want silent bootup.
  19
  20 config EARLY_PRINTK
  21         bool "Early printk" if EXPERT
  22         default y
  23         ---help---
  24           Write kernel log output directly into the VGA buffer or to a serial
  25           port.
  26
  27           This is useful for kernel debugging when your machine crashes very
  28           early before the console code is initialized. For normal operation
  29           it is not recommended because it looks ugly and doesn't cooperate
  30           with klogd/syslogd or the X server. You should normally say N here,
  31           unless you want to debug such a crash.
  32
  33 config EARLY_PRINTK_DBGP
  34         bool "Early printk via EHCI debug port"
  35         depends on EARLY_PRINTK && PCI
  36         select EARLY_PRINTK_USB
  37         ---help---
  38           Write kernel log output directly into the EHCI debug 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 say N here,
  44           unless you want to debug such a crash. You need usb debug device.
  45
  46 config EARLY_PRINTK_EFI
  47         bool "Early printk via the EFI framebuffer"
  48         depends on EFI && EARLY_PRINTK
  49         select FONT_SUPPORT
  50         ---help---
  51           Write kernel log output directly into the EFI framebuffer.
  52
  53           This is useful for kernel debugging when your machine crashes very
  54           early before the console code is initialized.
  55
  56 config EARLY_PRINTK_USB_XDBC
  57         bool "Early printk via the xHCI debug port"
  58         depends on EARLY_PRINTK && PCI
  59         select EARLY_PRINTK_USB
  60         ---help---
  61           Write kernel log output directly into the xHCI debug port.
  62
  63           One use for this feature is kernel debugging, for example when your
  64           machine crashes very early before the regular console code is
  65           initialized. Other uses include simpler, lockless logging instead of
  66           a full-blown printk console driver + klogd.
  67
  68           For normal production environments this is normally not recommended,
  69           because it doesn't feed events into klogd/syslogd and doesn't try to
  70           print anything on the screen.
  71
  72           You should normally say N here, unless you want to debug early
  73           crashes or need a very simple printk logging facility.
  74
  75 config X86_PTDUMP_CORE
  76         def_bool n
  77
  78 config X86_PTDUMP
  79         tristate "Export kernel pagetable layout to userspace via debugfs"
  80         depends on DEBUG_KERNEL
  81         select DEBUG_FS
  82         select X86_PTDUMP_CORE
  83         ---help---
  84           Say Y here if you want to show the kernel pagetable layout in a
  85           debugfs file. This information is only useful for kernel developers
  86           who are working in architecture specific areas of the kernel.
  87           It is probably not a good idea to enable this feature in a production
  88           kernel.
  89           If in doubt, say "N"
  90
  91 config EFI_PGT_DUMP
  92         bool "Dump the EFI pagetable"
  93         depends on EFI
  94         select X86_PTDUMP_CORE
  95         ---help---
  96           Enable this if you want to dump the EFI page table before
  97           enabling virtual mode. This can be used to debug miscellaneous
  98           issues with the mapping of the EFI runtime regions into that
  99           table.
 100
 101 config DEBUG_WX
 102         bool "Warn on W+X mappings at boot"
 103         select X86_PTDUMP_CORE
 104         ---help---
 105           Generate a warning if any W+X mappings are found at boot.
 106
 107           This is useful for discovering cases where the kernel is leaving
 108           W+X mappings after applying NX, as such mappings are a security risk.
 109
 110           Look for a message in dmesg output like this:
 111
 112             x86/mm: Checked W+X mappings: passed, no W+X pages found.
 113
 114           or like this, if the check failed:
 115
 116             x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
 117
 118           Note that even if the check fails, your kernel is possibly
 119           still fine, as W+X mappings are not a security hole in
 120           themselves, what they do is that they make the exploitation
 121           of other unfixed kernel bugs easier.
 122
 123           There is no runtime or memory usage effect of this option
 124           once the kernel has booted up - it's a one time check.
 125
 126           If in doubt, say "Y".
 127
 128 config DOUBLEFAULT
 129         default y
 130         bool "Enable doublefault exception handler" if EXPERT
 131         ---help---
 132           This option allows trapping of rare doublefault exceptions that
 133           would otherwise cause a system to silently reboot. Disabling this
 134           option saves about 4k and might cause you much additional grey
 135           hair.
 136
 137 config DEBUG_TLBFLUSH
 138         bool "Set upper limit of TLB entries to flush one-by-one"
 139         depends on DEBUG_KERNEL
 140         ---help---
 141
 142         X86-only for now.
 143
 144         This option allows the user to tune the amount of TLB entries the
 145         kernel flushes one-by-one instead of doing a full TLB flush. In
 146         certain situations, the former is cheaper. This is controlled by the
 147         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 148         to -1, the code flushes the whole TLB unconditionally. Otherwise,
 149         for positive values of it, the kernel will use single TLB entry
 150         invalidating instructions according to the following formula:
 151
 152         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 153
 154         If in doubt, say "N".
 155
 156 config IOMMU_DEBUG
 157         bool "Enable IOMMU debugging"
 158         depends on GART_IOMMU && DEBUG_KERNEL
 159         depends on X86_64
 160         ---help---
 161           Force the IOMMU to on even when you have less than 4GB of
 162           memory and add debugging code. On overflow always panic. And
 163           allow to enable IOMMU leak tracing. Can be disabled at boot
 164           time with iommu=noforce. This will also enable scatter gather
 165           list merging.  Currently not recommended for production
 166           code. When you use it make sure you have a big enough
 167           IOMMU/AGP aperture.  Most of the options enabled by this can
 168           be set more finegrained using the iommu= command line
 169           options. See Documentation/x86/x86_64/boot-options.txt for more
 170           details.
 171
 172 config IOMMU_STRESS
 173         bool "Enable IOMMU stress-test mode"
 174         ---help---
 175           This option disables various optimizations in IOMMU related
 176           code to do real stress testing of the IOMMU code. This option
 177           will cause a performance drop and should only be enabled for
 178           testing.
 179
 180 config IOMMU_LEAK
 181         bool "IOMMU leak tracing"
 182         depends on IOMMU_DEBUG && DMA_API_DEBUG
 183         ---help---
 184           Add a simple leak tracer to the IOMMU code. This is useful when you
 185           are debugging a buggy device driver that leaks IOMMU mappings.
 186
 187 config HAVE_MMIOTRACE_SUPPORT
 188         def_bool y
 189
 190 config X86_DECODER_SELFTEST
 191         bool "x86 instruction decoder selftest"
 192         depends on DEBUG_KERNEL && KPROBES
 193         depends on !COMPILE_TEST
 194         ---help---
 195          Perform x86 instruction decoder selftests at build time.
 196          This option is useful for checking the sanity of x86 instruction
 197          decoder code.
 198          If unsure, say "N".
 199
 200 #
 201 # IO delay types:
 202 #
 203
 204 config IO_DELAY_TYPE_0X80
 205         int
 206         default "0"
 207
 208 config IO_DELAY_TYPE_0XED
 209         int
 210         default "1"
 211
 212 config IO_DELAY_TYPE_UDELAY
 213         int
 214         default "2"
 215
 216 config IO_DELAY_TYPE_NONE
 217         int
 218         default "3"
 219
 220 choice
 221         prompt "IO delay type"
 222         default IO_DELAY_0X80
 223
 224 config IO_DELAY_0X80
 225         bool "port 0x80 based port-IO delay [recommended]"
 226         ---help---
 227           This is the traditional Linux IO delay used for in/out_p.
 228           It is the most tested hence safest selection here.
 229
 230 config IO_DELAY_0XED
 231         bool "port 0xed based port-IO delay"
 232         ---help---
 233           Use port 0xed as the IO delay. This frees up port 0x80 which is
 234           often used as a hardware-debug port.
 235
 236 config IO_DELAY_UDELAY
 237         bool "udelay based port-IO delay"
 238         ---help---
 239           Use udelay(2) as the IO delay method. This provides the delay
 240           while not having any side-effect on the IO port space.
 241
 242 config IO_DELAY_NONE
 243         bool "no port-IO delay"
 244         ---help---
 245           No port-IO delay. Will break on old boxes that require port-IO
 246           delay for certain operations. Should work on most new machines.
 247
 248 endchoice
 249
 250 if IO_DELAY_0X80
 251 config DEFAULT_IO_DELAY_TYPE
 252         int
 253         default IO_DELAY_TYPE_0X80
 254 endif
 255
 256 if IO_DELAY_0XED
 257 config DEFAULT_IO_DELAY_TYPE
 258         int
 259         default IO_DELAY_TYPE_0XED
 260 endif
 261
 262 if IO_DELAY_UDELAY
 263 config DEFAULT_IO_DELAY_TYPE
 264         int
 265         default IO_DELAY_TYPE_UDELAY
 266 endif
 267
 268 if IO_DELAY_NONE
 269 config DEFAULT_IO_DELAY_TYPE
 270         int
 271         default IO_DELAY_TYPE_NONE
 272 endif
 273
 274 config DEBUG_BOOT_PARAMS
 275         bool "Debug boot parameters"
 276         depends on DEBUG_KERNEL
 277         depends on DEBUG_FS
 278         ---help---
 279           This option will cause struct boot_params to be exported via debugfs.
 280
 281 config CPA_DEBUG
 282         bool "CPA self-test code"
 283         depends on DEBUG_KERNEL
 284         ---help---
 285           Do change_page_attr() self-tests every 30 seconds.
 286
 287 config OPTIMIZE_INLINING
 288         bool "Allow gcc to uninline functions marked 'inline'"
 289         ---help---
 290           This option determines if the kernel forces gcc to inline the functions
 291           developers have marked 'inline'. Doing so takes away freedom from gcc to
 292           do what it thinks is best, which is desirable for the gcc 3.x series of
 293           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 294           enabling this option will generate a smaller kernel there. Hopefully
 295           this algorithm is so good that allowing gcc 4.x and above to make the
 296           decision will become the default in the future. Until then this option
 297           is there to test gcc for this.
 298
 299           If unsure, say N.
 300
 301 config DEBUG_ENTRY
 302         bool "Debug low-level entry code"
 303         depends on DEBUG_KERNEL
 304         ---help---
 305           This option enables sanity checks in x86's low-level entry code.
 306           Some of these sanity checks may slow down kernel entries and
 307           exits or otherwise impact performance.
 308
 309           If unsure, say N.
 310
 311 config DEBUG_NMI_SELFTEST
 312         bool "NMI Selftest"
 313         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 314         ---help---
 315           Enabling this option turns on a quick NMI selftest to verify
 316           that the NMI behaves correctly.
 317
 318           This might help diagnose strange hangs that rely on NMI to
 319           function properly.
 320
 321           If unsure, say N.
 322
 323 config DEBUG_IMR_SELFTEST
 324         bool "Isolated Memory Region self test"
 325         default n
 326         depends on INTEL_IMR
 327         ---help---
 328           This option enables automated sanity testing of the IMR code.
 329           Some simple tests are run to verify IMR bounds checking, alignment
 330           and overlapping. This option is really only useful if you are
 331           debugging an IMR memory map or are modifying the IMR code and want to
 332           test your changes.
 333
 334           If unsure say N here.
 335
 336 config X86_DEBUG_FPU
 337         bool "Debug the x86 FPU code"
 338         depends on DEBUG_KERNEL
 339         default y
 340         ---help---
 341           If this option is enabled then there will be extra sanity
 342           checks and (boot time) debug printouts added to the kernel.
 343           This debugging adds some small amount of runtime overhead
 344           to the kernel.
 345
 346           If unsure, say N.
 347
 348 config PUNIT_ATOM_DEBUG
 349         tristate "ATOM Punit debug driver"
 350         depends on PCI
 351         select DEBUG_FS
 352         select IOSF_MBI
 353         ---help---
 354           This is a debug driver, which gets the power states
 355           of all Punit North Complex devices. The power states of
 356           each device is exposed as part of the debugfs interface.
 357           The current power state can be read from
 358           /sys/kernel/debug/punit_atom/dev_power_state
 359
 360 choice
 361         prompt "Choose kernel unwinder"
 362         default UNWINDER_ORC if X86_64
 363         default UNWINDER_FRAME_POINTER if X86_32
 364         ---help---
 365           This determines which method will be used for unwinding kernel stack
 366           traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
 367           livepatch, lockdep, and more.
 368
 369 config UNWINDER_ORC
 370         bool "ORC unwinder"
 371         depends on X86_64
 372         select STACK_VALIDATION
 373         ---help---
 374           This option enables the ORC (Oops Rewind Capability) unwinder for
 375           unwinding kernel stack traces.  It uses a custom data format which is
 376           a simplified version of the DWARF Call Frame Information standard.
 377
 378           This unwinder is more accurate across interrupt entry frames than the
 379           frame pointer unwinder.  It also enables a 5-10% performance
 380           improvement across the entire kernel compared to frame pointers.
 381
 382           Enabling this option will increase the kernel's runtime memory usage
 383           by roughly 2-4MB, depending on your kernel config.
 384
 385 config UNWINDER_FRAME_POINTER
 386         bool "Frame pointer unwinder"
 387         select FRAME_POINTER
 388         ---help---
 389           This option enables the frame pointer unwinder for unwinding kernel
 390           stack traces.
 391
 392           The unwinder itself is fast and it uses less RAM than the ORC
 393           unwinder, but the kernel text size will grow by ~3% and the kernel's
 394           overall performance will degrade by roughly 5-10%.
 395
 396           This option is recommended if you want to use the livepatch
 397           consistency model, as this is currently the only way to get a
 398           reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE).
 399
 400 config UNWINDER_GUESS
 401         bool "Guess unwinder"
 402         depends on EXPERT
 403         depends on !STACKDEPOT
 404         ---help---
 405           This option enables the "guess" unwinder for unwinding kernel stack
 406           traces.  It scans the stack and reports every kernel text address it
 407           finds.  Some of the addresses it reports may be incorrect.
 408
 409           While this option often produces false positives, it can still be
 410           useful in many cases.  Unlike the other unwinders, it has no runtime
 411           overhead.
 412
 413 endchoice
 414
 415 config FRAME_POINTER
 416         depends on !UNWINDER_ORC && !UNWINDER_GUESS
 417         bool
 418
 419 endmenu