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_LEAK
 173         bool "IOMMU leak tracing"
 174         depends on IOMMU_DEBUG && DMA_API_DEBUG
 175         ---help---
 176           Add a simple leak tracer to the IOMMU code. This is useful when you
 177           are debugging a buggy device driver that leaks IOMMU mappings.
 178
 179 config HAVE_MMIOTRACE_SUPPORT
 180         def_bool y
 181
 182 config X86_DECODER_SELFTEST
 183         bool "x86 instruction decoder selftest"
 184         depends on DEBUG_KERNEL && KPROBES
 185         depends on !COMPILE_TEST
 186         ---help---
 187          Perform x86 instruction decoder selftests at build time.
 188          This option is useful for checking the sanity of x86 instruction
 189          decoder code.
 190          If unsure, say "N".
 191
 192 #
 193 # IO delay types:
 194 #
 195
 196 config IO_DELAY_TYPE_0X80
 197         int
 198         default "0"
 199
 200 config IO_DELAY_TYPE_0XED
 201         int
 202         default "1"
 203
 204 config IO_DELAY_TYPE_UDELAY
 205         int
 206         default "2"
 207
 208 config IO_DELAY_TYPE_NONE
 209         int
 210         default "3"
 211
 212 choice
 213         prompt "IO delay type"
 214         default IO_DELAY_0X80
 215
 216 config IO_DELAY_0X80
 217         bool "port 0x80 based port-IO delay [recommended]"
 218         ---help---
 219           This is the traditional Linux IO delay used for in/out_p.
 220           It is the most tested hence safest selection here.
 221
 222 config IO_DELAY_0XED
 223         bool "port 0xed based port-IO delay"
 224         ---help---
 225           Use port 0xed as the IO delay. This frees up port 0x80 which is
 226           often used as a hardware-debug port.
 227
 228 config IO_DELAY_UDELAY
 229         bool "udelay based port-IO delay"
 230         ---help---
 231           Use udelay(2) as the IO delay method. This provides the delay
 232           while not having any side-effect on the IO port space.
 233
 234 config IO_DELAY_NONE
 235         bool "no port-IO delay"
 236         ---help---
 237           No port-IO delay. Will break on old boxes that require port-IO
 238           delay for certain operations. Should work on most new machines.
 239
 240 endchoice
 241
 242 if IO_DELAY_0X80
 243 config DEFAULT_IO_DELAY_TYPE
 244         int
 245         default IO_DELAY_TYPE_0X80
 246 endif
 247
 248 if IO_DELAY_0XED
 249 config DEFAULT_IO_DELAY_TYPE
 250         int
 251         default IO_DELAY_TYPE_0XED
 252 endif
 253
 254 if IO_DELAY_UDELAY
 255 config DEFAULT_IO_DELAY_TYPE
 256         int
 257         default IO_DELAY_TYPE_UDELAY
 258 endif
 259
 260 if IO_DELAY_NONE
 261 config DEFAULT_IO_DELAY_TYPE
 262         int
 263         default IO_DELAY_TYPE_NONE
 264 endif
 265
 266 config DEBUG_BOOT_PARAMS
 267         bool "Debug boot parameters"
 268         depends on DEBUG_KERNEL
 269         depends on DEBUG_FS
 270         ---help---
 271           This option will cause struct boot_params to be exported via debugfs.
 272
 273 config CPA_DEBUG
 274         bool "CPA self-test code"
 275         depends on DEBUG_KERNEL
 276         ---help---
 277           Do change_page_attr() self-tests every 30 seconds.
 278
 279 config OPTIMIZE_INLINING
 280         bool "Allow gcc to uninline functions marked 'inline'"
 281         ---help---
 282           This option determines if the kernel forces gcc to inline the functions
 283           developers have marked 'inline'. Doing so takes away freedom from gcc to
 284           do what it thinks is best, which is desirable for the gcc 3.x series of
 285           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 286           enabling this option will generate a smaller kernel there. Hopefully
 287           this algorithm is so good that allowing gcc 4.x and above to make the
 288           decision will become the default in the future. Until then this option
 289           is there to test gcc for this.
 290
 291           If unsure, say N.
 292
 293 config DEBUG_ENTRY
 294         bool "Debug low-level entry code"
 295         depends on DEBUG_KERNEL
 296         ---help---
 297           This option enables sanity checks in x86's low-level entry code.
 298           Some of these sanity checks may slow down kernel entries and
 299           exits or otherwise impact performance.
 300
 301           If unsure, say N.
 302
 303 config DEBUG_NMI_SELFTEST
 304         bool "NMI Selftest"
 305         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 306         ---help---
 307           Enabling this option turns on a quick NMI selftest to verify
 308           that the NMI behaves correctly.
 309
 310           This might help diagnose strange hangs that rely on NMI to
 311           function properly.
 312
 313           If unsure, say N.
 314
 315 config DEBUG_IMR_SELFTEST
 316         bool "Isolated Memory Region self test"
 317         default n
 318         depends on INTEL_IMR
 319         ---help---
 320           This option enables automated sanity testing of the IMR code.
 321           Some simple tests are run to verify IMR bounds checking, alignment
 322           and overlapping. This option is really only useful if you are
 323           debugging an IMR memory map or are modifying the IMR code and want to
 324           test your changes.
 325
 326           If unsure say N here.
 327
 328 config X86_DEBUG_FPU
 329         bool "Debug the x86 FPU code"
 330         depends on DEBUG_KERNEL
 331         default y
 332         ---help---
 333           If this option is enabled then there will be extra sanity
 334           checks and (boot time) debug printouts added to the kernel.
 335           This debugging adds some small amount of runtime overhead
 336           to the kernel.
 337
 338           If unsure, say N.
 339
 340 config PUNIT_ATOM_DEBUG
 341         tristate "ATOM Punit debug driver"
 342         depends on PCI
 343         select DEBUG_FS
 344         select IOSF_MBI
 345         ---help---
 346           This is a debug driver, which gets the power states
 347           of all Punit North Complex devices. The power states of
 348           each device is exposed as part of the debugfs interface.
 349           The current power state can be read from
 350           /sys/kernel/debug/punit_atom/dev_power_state
 351
 352 choice
 353         prompt "Choose kernel unwinder"
 354         default UNWINDER_ORC if X86_64
 355         default UNWINDER_FRAME_POINTER if X86_32
 356         ---help---
 357           This determines which method will be used for unwinding kernel stack
 358           traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
 359           livepatch, lockdep, and more.
 360
 361 config UNWINDER_ORC
 362         bool "ORC unwinder"
 363         depends on X86_64
 364         select STACK_VALIDATION
 365         ---help---
 366           This option enables the ORC (Oops Rewind Capability) unwinder for
 367           unwinding kernel stack traces.  It uses a custom data format which is
 368           a simplified version of the DWARF Call Frame Information standard.
 369
 370           This unwinder is more accurate across interrupt entry frames than the
 371           frame pointer unwinder.  It also enables a 5-10% performance
 372           improvement across the entire kernel compared to frame pointers.
 373
 374           Enabling this option will increase the kernel's runtime memory usage
 375           by roughly 2-4MB, depending on your kernel config.
 376
 377 config UNWINDER_FRAME_POINTER
 378         bool "Frame pointer unwinder"
 379         select FRAME_POINTER
 380         ---help---
 381           This option enables the frame pointer unwinder for unwinding kernel
 382           stack traces.
 383
 384           The unwinder itself is fast and it uses less RAM than the ORC
 385           unwinder, but the kernel text size will grow by ~3% and the kernel's
 386           overall performance will degrade by roughly 5-10%.
 387
 388           This option is recommended if you want to use the livepatch
 389           consistency model, as this is currently the only way to get a
 390           reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE).
 391
 392 config UNWINDER_GUESS
 393         bool "Guess unwinder"
 394         depends on EXPERT
 395         depends on !STACKDEPOT
 396         ---help---
 397           This option enables the "guess" unwinder for unwinding kernel stack
 398           traces.  It scans the stack and reports every kernel text address it
 399           finds.  Some of the addresses it reports may be incorrect.
 400
 401           While this option often produces false positives, it can still be
 402           useful in many cases.  Unlike the other unwinders, it has no runtime
 403           overhead.
 404
 405 endchoice
 406
 407 config FRAME_POINTER
 408         depends on !UNWINDER_ORC && !UNWINDER_GUESS
 409         bool
 410
 411 endmenu