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