arch/x86/Kconfig.debug

   1 # SPDX-License-Identifier: GPL-2.0
   2
   3 config TRACE_IRQFLAGS_SUPPORT
   4         def_bool y
   5
   6 config EARLY_PRINTK_USB
   7         bool
   8
   9 config X86_VERBOSE_BOOTUP
  10         bool "Enable verbose x86 bootup info messages"
  11         default y
  12         ---help---
  13           Enables the informational output from the decompression stage
  14           (e.g. bzImage) of the boot. If you disable this you will still
  15           see errors. Disable this if you want silent bootup.
  16
  17 config EARLY_PRINTK
  18         bool "Early printk" if EXPERT
  19         default y
  20         ---help---
  21           Write kernel log output directly into the VGA buffer or to a serial
  22           port.
  23
  24           This is useful for kernel debugging when your machine crashes very
  25           early before the console code is initialized. For normal operation
  26           it is not recommended because it looks ugly and doesn't cooperate
  27           with klogd/syslogd or the X server. You should normally say N here,
  28           unless you want to debug such a crash.
  29
  30 config EARLY_PRINTK_DBGP
  31         bool "Early printk via EHCI debug port"
  32         depends on EARLY_PRINTK && PCI
  33         select EARLY_PRINTK_USB
  34         ---help---
  35           Write kernel log output directly into the EHCI debug port.
  36
  37           This is useful for kernel debugging when your machine crashes very
  38           early before the console code is initialized. For normal operation
  39           it is not recommended because it looks ugly and doesn't cooperate
  40           with klogd/syslogd or the X server. You should normally say N here,
  41           unless you want to debug such a crash. You need usb debug device.
  42
  43 config EARLY_PRINTK_USB_XDBC
  44         bool "Early printk via the xHCI debug port"
  45         depends on EARLY_PRINTK && PCI
  46         select EARLY_PRINTK_USB
  47         ---help---
  48           Write kernel log output directly into the xHCI debug port.
  49
  50           One use for this feature is kernel debugging, for example when your
  51           machine crashes very early before the regular console code is
  52           initialized. Other uses include simpler, lockless logging instead of
  53           a full-blown printk console driver + klogd.
  54
  55           For normal production environments this is normally not recommended,
  56           because it doesn't feed events into klogd/syslogd and doesn't try to
  57           print anything on the screen.
  58
  59           You should normally say N here, unless you want to debug early
  60           crashes or need a very simple printk logging facility.
  61
  62 config MCSAFE_TEST
  63         def_bool n
  64
  65 config X86_PTDUMP_CORE
  66         def_bool n
  67
  68 config X86_PTDUMP
  69         tristate "Export kernel pagetable layout to userspace via debugfs"
  70         depends on DEBUG_KERNEL
  71         select DEBUG_FS
  72         select X86_PTDUMP_CORE
  73         ---help---
  74           Say Y here if you want to show the kernel pagetable layout in a
  75           debugfs file. This information is only useful for kernel developers
  76           who are working in architecture specific areas of the kernel.
  77           It is probably not a good idea to enable this feature in a production
  78           kernel.
  79           If in doubt, say "N"
  80
  81 config EFI_PGT_DUMP
  82         bool "Dump the EFI pagetable"
  83         depends on EFI
  84         select X86_PTDUMP_CORE
  85         ---help---
  86           Enable this if you want to dump the EFI page table before
  87           enabling virtual mode. This can be used to debug miscellaneous
  88           issues with the mapping of the EFI runtime regions into that
  89           table.
  90
  91 config DEBUG_WX
  92         bool "Warn on W+X mappings at boot"
  93         select X86_PTDUMP_CORE
  94         ---help---
  95           Generate a warning if any W+X mappings are found at boot.
  96
  97           This is useful for discovering cases where the kernel is leaving
  98           W+X mappings after applying NX, as such mappings are a security risk.
  99
 100           Look for a message in dmesg output like this:
 101
 102             x86/mm: Checked W+X mappings: passed, no W+X pages found.
 103
 104           or like this, if the check failed:
 105
 106             x86/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
 107
 108           Note that even if the check fails, your kernel is possibly
 109           still fine, as W+X mappings are not a security hole in
 110           themselves, what they do is that they make the exploitation
 111           of other unfixed kernel bugs easier.
 112
 113           There is no runtime or memory usage effect of this option
 114           once the kernel has booted up - it's a one time check.
 115
 116           If in doubt, say "Y".
 117
 118 config DOUBLEFAULT
 119         default y
 120         bool "Enable doublefault exception handler" if EXPERT && X86_32
 121         ---help---
 122           This option allows trapping of rare doublefault exceptions that
 123           would otherwise cause a system to silently reboot. Disabling this
 124           option saves about 4k and might cause you much additional grey
 125           hair.
 126
 127 config DEBUG_TLBFLUSH
 128         bool "Set upper limit of TLB entries to flush one-by-one"
 129         depends on DEBUG_KERNEL
 130         ---help---
 131
 132         X86-only for now.
 133
 134         This option allows the user to tune the amount of TLB entries the
 135         kernel flushes one-by-one instead of doing a full TLB flush. In
 136         certain situations, the former is cheaper. This is controlled by the
 137         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 138         to -1, the code flushes the whole TLB unconditionally. Otherwise,
 139         for positive values of it, the kernel will use single TLB entry
 140         invalidating instructions according to the following formula:
 141
 142         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 143
 144         If in doubt, say "N".
 145
 146 config IOMMU_DEBUG
 147         bool "Enable IOMMU debugging"
 148         depends on GART_IOMMU && DEBUG_KERNEL
 149         depends on X86_64
 150         ---help---
 151           Force the IOMMU to on even when you have less than 4GB of
 152           memory and add debugging code. On overflow always panic. And
 153           allow to enable IOMMU leak tracing. Can be disabled at boot
 154           time with iommu=noforce. This will also enable scatter gather
 155           list merging.  Currently not recommended for production
 156           code. When you use it make sure you have a big enough
 157           IOMMU/AGP aperture.  Most of the options enabled by this can
 158           be set more finegrained using the iommu= command line
 159           options. See Documentation/x86/x86_64/boot-options.rst for more
 160           details.
 161
 162 config IOMMU_LEAK
 163         bool "IOMMU leak tracing"
 164         depends on IOMMU_DEBUG && DMA_API_DEBUG
 165         ---help---
 166           Add a simple leak tracer to the IOMMU code. This is useful when you
 167           are debugging a buggy device driver that leaks IOMMU mappings.
 168
 169 config HAVE_MMIOTRACE_SUPPORT
 170         def_bool y
 171
 172 config X86_DECODER_SELFTEST
 173         bool "x86 instruction decoder selftest"
 174         depends on DEBUG_KERNEL && INSTRUCTION_DECODER
 175         depends on !COMPILE_TEST
 176         ---help---
 177          Perform x86 instruction decoder selftests at build time.
 178          This option is useful for checking the sanity of x86 instruction
 179          decoder code.
 180          If unsure, say "N".
 181
 182 choice
 183         prompt "IO delay type"
 184         default IO_DELAY_0X80
 185
 186 config IO_DELAY_0X80
 187         bool "port 0x80 based port-IO delay [recommended]"
 188         ---help---
 189           This is the traditional Linux IO delay used for in/out_p.
 190           It is the most tested hence safest selection here.
 191
 192 config IO_DELAY_0XED
 193         bool "port 0xed based port-IO delay"
 194         ---help---
 195           Use port 0xed as the IO delay. This frees up port 0x80 which is
 196           often used as a hardware-debug port.
 197
 198 config IO_DELAY_UDELAY
 199         bool "udelay based port-IO delay"
 200         ---help---
 201           Use udelay(2) as the IO delay method. This provides the delay
 202           while not having any side-effect on the IO port space.
 203
 204 config IO_DELAY_NONE
 205         bool "no port-IO delay"
 206         ---help---
 207           No port-IO delay. Will break on old boxes that require port-IO
 208           delay for certain operations. Should work on most new machines.
 209
 210 endchoice
 211
 212 config DEBUG_BOOT_PARAMS
 213         bool "Debug boot parameters"
 214         depends on DEBUG_KERNEL
 215         depends on DEBUG_FS
 216         ---help---
 217           This option will cause struct boot_params to be exported via debugfs.
 218
 219 config CPA_DEBUG
 220         bool "CPA self-test code"
 221         depends on DEBUG_KERNEL
 222         ---help---
 223           Do change_page_attr() self-tests every 30 seconds.
 224
 225 config DEBUG_ENTRY
 226         bool "Debug low-level entry code"
 227         depends on DEBUG_KERNEL
 228         ---help---
 229           This option enables sanity checks in x86's low-level entry code.
 230           Some of these sanity checks may slow down kernel entries and
 231           exits or otherwise impact performance.
 232
 233           If unsure, say N.
 234
 235 config DEBUG_NMI_SELFTEST
 236         bool "NMI Selftest"
 237         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 238         ---help---
 239           Enabling this option turns on a quick NMI selftest to verify
 240           that the NMI behaves correctly.
 241
 242           This might help diagnose strange hangs that rely on NMI to
 243           function properly.
 244
 245           If unsure, say N.
 246
 247 config DEBUG_IMR_SELFTEST
 248         bool "Isolated Memory Region self test"
 249         depends on INTEL_IMR
 250         ---help---
 251           This option enables automated sanity testing of the IMR code.
 252           Some simple tests are run to verify IMR bounds checking, alignment
 253           and overlapping. This option is really only useful if you are
 254           debugging an IMR memory map or are modifying the IMR code and want to
 255           test your changes.
 256
 257           If unsure say N here.
 258
 259 config X86_DEBUG_FPU
 260         bool "Debug the x86 FPU code"
 261         depends on DEBUG_KERNEL
 262         default y
 263         ---help---
 264           If this option is enabled then there will be extra sanity
 265           checks and (boot time) debug printouts added to the kernel.
 266           This debugging adds some small amount of runtime overhead
 267           to the kernel.
 268
 269           If unsure, say N.
 270
 271 config PUNIT_ATOM_DEBUG
 272         tristate "ATOM Punit debug driver"
 273         depends on PCI
 274         select DEBUG_FS
 275         select IOSF_MBI
 276         ---help---
 277           This is a debug driver, which gets the power states
 278           of all Punit North Complex devices. The power states of
 279           each device is exposed as part of the debugfs interface.
 280           The current power state can be read from
 281           /sys/kernel/debug/punit_atom/dev_power_state
 282
 283 choice
 284         prompt "Choose kernel unwinder"
 285         default UNWINDER_ORC if X86_64
 286         default UNWINDER_FRAME_POINTER if X86_32
 287         ---help---
 288           This determines which method will be used for unwinding kernel stack
 289           traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
 290           livepatch, lockdep, and more.
 291
 292 config UNWINDER_ORC
 293         bool "ORC unwinder"
 294         depends on X86_64
 295         select STACK_VALIDATION
 296         ---help---
 297           This option enables the ORC (Oops Rewind Capability) unwinder for
 298           unwinding kernel stack traces.  It uses a custom data format which is
 299           a simplified version of the DWARF Call Frame Information standard.
 300
 301           This unwinder is more accurate across interrupt entry frames than the
 302           frame pointer unwinder.  It also enables a 5-10% performance
 303           improvement across the entire kernel compared to frame pointers.
 304
 305           Enabling this option will increase the kernel's runtime memory usage
 306           by roughly 2-4MB, depending on your kernel config.
 307
 308 config UNWINDER_FRAME_POINTER
 309         bool "Frame pointer unwinder"
 310         select FRAME_POINTER
 311         ---help---
 312           This option enables the frame pointer unwinder for unwinding kernel
 313           stack traces.
 314
 315           The unwinder itself is fast and it uses less RAM than the ORC
 316           unwinder, but the kernel text size will grow by ~3% and the kernel's
 317           overall performance will degrade by roughly 5-10%.
 318
 319 config UNWINDER_GUESS
 320         bool "Guess unwinder"
 321         depends on EXPERT
 322         depends on !STACKDEPOT
 323         ---help---
 324           This option enables the "guess" unwinder for unwinding kernel stack
 325           traces.  It scans the stack and reports every kernel text address it
 326           finds.  Some of the addresses it reports may be incorrect.
 327
 328           While this option often produces false positives, it can still be
 329           useful in many cases.  Unlike the other unwinders, it has no runtime
 330           overhead.
 331
 332 endchoice
 333
 334 config FRAME_POINTER
 335         depends on !UNWINDER_ORC && !UNWINDER_GUESS
 336         bool