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_INTEL_MID
  47         bool "Early printk for Intel MID platform support"
  48         depends on EARLY_PRINTK && X86_INTEL_MID
  49
  50 config EARLY_PRINTK_DBGP
  51         bool "Early printk via EHCI debug port"
  52         depends on EARLY_PRINTK && PCI
  53         ---help---
  54           Write kernel log output directly into the EHCI debug port.
  55
  56           This is useful for kernel debugging when your machine crashes very
  57           early before the console code is initialized. For normal operation
  58           it is not recommended because it looks ugly and doesn't cooperate
  59           with klogd/syslogd or the X server. You should normally N here,
  60           unless you want to debug such a crash. You need usb debug device.
  61
  62 config EARLY_PRINTK_EFI
  63         bool "Early printk via the EFI framebuffer"
  64         depends on EFI && EARLY_PRINTK
  65         select FONT_SUPPORT
  66         ---help---
  67           Write kernel log output directly into the EFI framebuffer.
  68
  69           This is useful for kernel debugging when your machine crashes very
  70           early before the console code is initialized.
  71
  72 config X86_PTDUMP
  73         bool "Export kernel pagetable layout to userspace via debugfs"
  74         depends on DEBUG_KERNEL
  75         select DEBUG_FS
  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 && X86_PTDUMP
  87         ---help---
  88           Enable this if you want to dump the EFI page table before
  89           enabling virtual mode. This can be used to debug miscellaneous
  90           issues with the mapping of the EFI runtime regions into that
  91           table.
  92
  93 config DEBUG_RODATA
  94         bool "Write protect kernel read-only data structures"
  95         default y
  96         depends on DEBUG_KERNEL
  97         ---help---
  98           Mark the kernel read-only data as write-protected in the pagetables,
  99           in order to catch accidental (and incorrect) writes to such const
 100           data. This is recommended so that we can catch kernel bugs sooner.
 101           If in doubt, say "Y".
 102
 103 config DEBUG_RODATA_TEST
 104         bool "Testcase for the DEBUG_RODATA feature"
 105         depends on DEBUG_RODATA
 106         default y
 107         ---help---
 108           This option enables a testcase for the DEBUG_RODATA
 109           feature as well as for the change_page_attr() infrastructure.
 110           If in doubt, say "N"
 111
 112 config DEBUG_SET_MODULE_RONX
 113         bool "Set loadable kernel module data as NX and text as RO"
 114         depends on MODULES
 115         ---help---
 116           This option helps catch unintended modifications to loadable
 117           kernel module's text and read-only data. It also prevents execution
 118           of module data. Such protection may interfere with run-time code
 119           patching and dynamic kernel tracing - and they might also protect
 120           against certain classes of kernel exploits.
 121           If in doubt, say "N".
 122
 123 config DEBUG_NX_TEST
 124         tristate "Testcase for the NX non-executable stack feature"
 125         depends on DEBUG_KERNEL && m
 126         ---help---
 127           This option enables a testcase for the CPU NX capability
 128           and the software setup of this feature.
 129           If in doubt, say "N"
 130
 131 config DOUBLEFAULT
 132         default y
 133         bool "Enable doublefault exception handler" if EXPERT
 134         ---help---
 135           This option allows trapping of rare doublefault exceptions that
 136           would otherwise cause a system to silently reboot. Disabling this
 137           option saves about 4k and might cause you much additional grey
 138           hair.
 139
 140 config DEBUG_TLBFLUSH
 141         bool "Set upper limit of TLB entries to flush one-by-one"
 142         depends on DEBUG_KERNEL
 143         ---help---
 144
 145         X86-only for now.
 146
 147         This option allows the user to tune the amount of TLB entries the
 148         kernel flushes one-by-one instead of doing a full TLB flush. In
 149         certain situations, the former is cheaper. This is controlled by the
 150         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 151         to -1, the code flushes the whole TLB unconditionally. Otherwise,
 152         for positive values of it, the kernel will use single TLB entry
 153         invalidating instructions according to the following formula:
 154
 155         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 156
 157         If in doubt, say "N".
 158
 159 config IOMMU_DEBUG
 160         bool "Enable IOMMU debugging"
 161         depends on GART_IOMMU && DEBUG_KERNEL
 162         depends on X86_64
 163         ---help---
 164           Force the IOMMU to on even when you have less than 4GB of
 165           memory and add debugging code. On overflow always panic. And
 166           allow to enable IOMMU leak tracing. Can be disabled at boot
 167           time with iommu=noforce. This will also enable scatter gather
 168           list merging.  Currently not recommended for production
 169           code. When you use it make sure you have a big enough
 170           IOMMU/AGP aperture.  Most of the options enabled by this can
 171           be set more finegrained using the iommu= command line
 172           options. See Documentation/x86/x86_64/boot-options.txt for more
 173           details.
 174
 175 config IOMMU_STRESS
 176         bool "Enable IOMMU stress-test mode"
 177         ---help---
 178           This option disables various optimizations in IOMMU related
 179           code to do real stress testing of the IOMMU code. This option
 180           will cause a performance drop and should only be enabled for
 181           testing.
 182
 183 config IOMMU_LEAK
 184         bool "IOMMU leak tracing"
 185         depends on IOMMU_DEBUG && DMA_API_DEBUG
 186         ---help---
 187           Add a simple leak tracer to the IOMMU code. This is useful when you
 188           are debugging a buggy device driver that leaks IOMMU mappings.
 189
 190 config HAVE_MMIOTRACE_SUPPORT
 191         def_bool y
 192
 193 config X86_DECODER_SELFTEST
 194         bool "x86 instruction decoder selftest"
 195         depends on DEBUG_KERNEL && KPROBES
 196         depends on !COMPILE_TEST
 197         ---help---
 198          Perform x86 instruction decoder selftests at build time.
 199          This option is useful for checking the sanity of x86 instruction
 200          decoder code.
 201          If unsure, say "N".
 202
 203 #
 204 # IO delay types:
 205 #
 206
 207 config IO_DELAY_TYPE_0X80
 208         int
 209         default "0"
 210
 211 config IO_DELAY_TYPE_0XED
 212         int
 213         default "1"
 214
 215 config IO_DELAY_TYPE_UDELAY
 216         int
 217         default "2"
 218
 219 config IO_DELAY_TYPE_NONE
 220         int
 221         default "3"
 222
 223 choice
 224         prompt "IO delay type"
 225         default IO_DELAY_0X80
 226
 227 config IO_DELAY_0X80
 228         bool "port 0x80 based port-IO delay [recommended]"
 229         ---help---
 230           This is the traditional Linux IO delay used for in/out_p.
 231           It is the most tested hence safest selection here.
 232
 233 config IO_DELAY_0XED
 234         bool "port 0xed based port-IO delay"
 235         ---help---
 236           Use port 0xed as the IO delay. This frees up port 0x80 which is
 237           often used as a hardware-debug port.
 238
 239 config IO_DELAY_UDELAY
 240         bool "udelay based port-IO delay"
 241         ---help---
 242           Use udelay(2) as the IO delay method. This provides the delay
 243           while not having any side-effect on the IO port space.
 244
 245 config IO_DELAY_NONE
 246         bool "no port-IO delay"
 247         ---help---
 248           No port-IO delay. Will break on old boxes that require port-IO
 249           delay for certain operations. Should work on most new machines.
 250
 251 endchoice
 252
 253 if IO_DELAY_0X80
 254 config DEFAULT_IO_DELAY_TYPE
 255         int
 256         default IO_DELAY_TYPE_0X80
 257 endif
 258
 259 if IO_DELAY_0XED
 260 config DEFAULT_IO_DELAY_TYPE
 261         int
 262         default IO_DELAY_TYPE_0XED
 263 endif
 264
 265 if IO_DELAY_UDELAY
 266 config DEFAULT_IO_DELAY_TYPE
 267         int
 268         default IO_DELAY_TYPE_UDELAY
 269 endif
 270
 271 if IO_DELAY_NONE
 272 config DEFAULT_IO_DELAY_TYPE
 273         int
 274         default IO_DELAY_TYPE_NONE
 275 endif
 276
 277 config DEBUG_BOOT_PARAMS
 278         bool "Debug boot parameters"
 279         depends on DEBUG_KERNEL
 280         depends on DEBUG_FS
 281         ---help---
 282           This option will cause struct boot_params to be exported via debugfs.
 283
 284 config CPA_DEBUG
 285         bool "CPA self-test code"
 286         depends on DEBUG_KERNEL
 287         ---help---
 288           Do change_page_attr() self-tests every 30 seconds.
 289
 290 config OPTIMIZE_INLINING
 291         bool "Allow gcc to uninline functions marked 'inline'"
 292         ---help---
 293           This option determines if the kernel forces gcc to inline the functions
 294           developers have marked 'inline'. Doing so takes away freedom from gcc to
 295           do what it thinks is best, which is desirable for the gcc 3.x series of
 296           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 297           enabling this option will generate a smaller kernel there. Hopefully
 298           this algorithm is so good that allowing gcc 4.x and above to make the
 299           decision will become the default in the future. Until then this option
 300           is there to test gcc for this.
 301
 302           If unsure, say N.
 303
 304 config DEBUG_NMI_SELFTEST
 305         bool "NMI Selftest"
 306         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 307         ---help---
 308           Enabling this option turns on a quick NMI selftest to verify
 309           that the NMI behaves correctly.
 310
 311           This might help diagnose strange hangs that rely on NMI to
 312           function properly.
 313
 314           If unsure, say N.
 315
 316 config X86_DEBUG_STATIC_CPU_HAS
 317         bool "Debug alternatives"
 318         depends on DEBUG_KERNEL
 319         ---help---
 320           This option causes additional code to be generated which
 321           fails if static_cpu_has() is used before alternatives have
 322           run.
 323
 324           If unsure, say N.
 325
 326 endmenu