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 X86_PTDUMP
  63         bool "Export kernel pagetable layout to userspace via debugfs"
  64         depends on DEBUG_KERNEL
  65         select DEBUG_FS
  66         ---help---
  67           Say Y here if you want to show the kernel pagetable layout in a
  68           debugfs file. This information is only useful for kernel developers
  69           who are working in architecture specific areas of the kernel.
  70           It is probably not a good idea to enable this feature in a production
  71           kernel.
  72           If in doubt, say "N"
  73
  74 config DEBUG_RODATA
  75         bool "Write protect kernel read-only data structures"
  76         default y
  77         depends on DEBUG_KERNEL
  78         ---help---
  79           Mark the kernel read-only data as write-protected in the pagetables,
  80           in order to catch accidental (and incorrect) writes to such const
  81           data. This is recommended so that we can catch kernel bugs sooner.
  82           If in doubt, say "Y".
  83
  84 config DEBUG_RODATA_TEST
  85         bool "Testcase for the DEBUG_RODATA feature"
  86         depends on DEBUG_RODATA
  87         default y
  88         ---help---
  89           This option enables a testcase for the DEBUG_RODATA
  90           feature as well as for the change_page_attr() infrastructure.
  91           If in doubt, say "N"
  92
  93 config DEBUG_SET_MODULE_RONX
  94         bool "Set loadable kernel module data as NX and text as RO"
  95         depends on MODULES
  96         ---help---
  97           This option helps catch unintended modifications to loadable
  98           kernel module's text and read-only data. It also prevents execution
  99           of module data. Such protection may interfere with run-time code
 100           patching and dynamic kernel tracing - and they might also protect
 101           against certain classes of kernel exploits.
 102           If in doubt, say "N".
 103
 104 config DEBUG_NX_TEST
 105         tristate "Testcase for the NX non-executable stack feature"
 106         depends on DEBUG_KERNEL && m
 107         ---help---
 108           This option enables a testcase for the CPU NX capability
 109           and the software setup of this feature.
 110           If in doubt, say "N"
 111
 112 config DOUBLEFAULT
 113         default y
 114         bool "Enable doublefault exception handler" if EXPERT
 115         ---help---
 116           This option allows trapping of rare doublefault exceptions that
 117           would otherwise cause a system to silently reboot. Disabling this
 118           option saves about 4k and might cause you much additional grey
 119           hair.
 120
 121 config DEBUG_TLBFLUSH
 122         bool "Set upper limit of TLB entries to flush one-by-one"
 123         depends on DEBUG_KERNEL
 124         ---help---
 125
 126         X86-only for now.
 127
 128         This option allows the user to tune the amount of TLB entries the
 129         kernel flushes one-by-one instead of doing a full TLB flush. In
 130         certain situations, the former is cheaper. This is controlled by the
 131         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 132         to -1, the code flushes the whole TLB unconditionally. Otherwise,
 133         for positive values of it, the kernel will use single TLB entry
 134         invalidating instructions according to the following formula:
 135
 136         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 137
 138         If in doubt, say "N".
 139
 140 config IOMMU_DEBUG
 141         bool "Enable IOMMU debugging"
 142         depends on GART_IOMMU && DEBUG_KERNEL
 143         depends on X86_64
 144         ---help---
 145           Force the IOMMU to on even when you have less than 4GB of
 146           memory and add debugging code. On overflow always panic. And
 147           allow to enable IOMMU leak tracing. Can be disabled at boot
 148           time with iommu=noforce. This will also enable scatter gather
 149           list merging.  Currently not recommended for production
 150           code. When you use it make sure you have a big enough
 151           IOMMU/AGP aperture.  Most of the options enabled by this can
 152           be set more finegrained using the iommu= command line
 153           options. See Documentation/x86/x86_64/boot-options.txt for more
 154           details.
 155
 156 config IOMMU_STRESS
 157         bool "Enable IOMMU stress-test mode"
 158         ---help---
 159           This option disables various optimizations in IOMMU related
 160           code to do real stress testing of the IOMMU code. This option
 161           will cause a performance drop and should only be enabled for
 162           testing.
 163
 164 config IOMMU_LEAK
 165         bool "IOMMU leak tracing"
 166         depends on IOMMU_DEBUG && DMA_API_DEBUG
 167         ---help---
 168           Add a simple leak tracer to the IOMMU code. This is useful when you
 169           are debugging a buggy device driver that leaks IOMMU mappings.
 170
 171 config HAVE_MMIOTRACE_SUPPORT
 172         def_bool y
 173
 174 config X86_DECODER_SELFTEST
 175         bool "x86 instruction decoder selftest"
 176         depends on DEBUG_KERNEL && KPROBES
 177         ---help---
 178          Perform x86 instruction decoder selftests at build time.
 179          This option is useful for checking the sanity of x86 instruction
 180          decoder code.
 181          If unsure, say "N".
 182
 183 #
 184 # IO delay types:
 185 #
 186
 187 config IO_DELAY_TYPE_0X80
 188         int
 189         default "0"
 190
 191 config IO_DELAY_TYPE_0XED
 192         int
 193         default "1"
 194
 195 config IO_DELAY_TYPE_UDELAY
 196         int
 197         default "2"
 198
 199 config IO_DELAY_TYPE_NONE
 200         int
 201         default "3"
 202
 203 choice
 204         prompt "IO delay type"
 205         default IO_DELAY_0X80
 206
 207 config IO_DELAY_0X80
 208         bool "port 0x80 based port-IO delay [recommended]"
 209         ---help---
 210           This is the traditional Linux IO delay used for in/out_p.
 211           It is the most tested hence safest selection here.
 212
 213 config IO_DELAY_0XED
 214         bool "port 0xed based port-IO delay"
 215         ---help---
 216           Use port 0xed as the IO delay. This frees up port 0x80 which is
 217           often used as a hardware-debug port.
 218
 219 config IO_DELAY_UDELAY
 220         bool "udelay based port-IO delay"
 221         ---help---
 222           Use udelay(2) as the IO delay method. This provides the delay
 223           while not having any side-effect on the IO port space.
 224
 225 config IO_DELAY_NONE
 226         bool "no port-IO delay"
 227         ---help---
 228           No port-IO delay. Will break on old boxes that require port-IO
 229           delay for certain operations. Should work on most new machines.
 230
 231 endchoice
 232
 233 if IO_DELAY_0X80
 234 config DEFAULT_IO_DELAY_TYPE
 235         int
 236         default IO_DELAY_TYPE_0X80
 237 endif
 238
 239 if IO_DELAY_0XED
 240 config DEFAULT_IO_DELAY_TYPE
 241         int
 242         default IO_DELAY_TYPE_0XED
 243 endif
 244
 245 if IO_DELAY_UDELAY
 246 config DEFAULT_IO_DELAY_TYPE
 247         int
 248         default IO_DELAY_TYPE_UDELAY
 249 endif
 250
 251 if IO_DELAY_NONE
 252 config DEFAULT_IO_DELAY_TYPE
 253         int
 254         default IO_DELAY_TYPE_NONE
 255 endif
 256
 257 config DEBUG_BOOT_PARAMS
 258         bool "Debug boot parameters"
 259         depends on DEBUG_KERNEL
 260         depends on DEBUG_FS
 261         ---help---
 262           This option will cause struct boot_params to be exported via debugfs.
 263
 264 config CPA_DEBUG
 265         bool "CPA self-test code"
 266         depends on DEBUG_KERNEL
 267         ---help---
 268           Do change_page_attr() self-tests every 30 seconds.
 269
 270 config OPTIMIZE_INLINING
 271         bool "Allow gcc to uninline functions marked 'inline'"
 272         ---help---
 273           This option determines if the kernel forces gcc to inline the functions
 274           developers have marked 'inline'. Doing so takes away freedom from gcc to
 275           do what it thinks is best, which is desirable for the gcc 3.x series of
 276           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 277           enabling this option will generate a smaller kernel there. Hopefully
 278           this algorithm is so good that allowing gcc 4.x and above to make the
 279           decision will become the default in the future. Until then this option
 280           is there to test gcc for this.
 281
 282           If unsure, say N.
 283
 284 config DEBUG_NMI_SELFTEST
 285         bool "NMI Selftest"
 286         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 287         ---help---
 288           Enabling this option turns on a quick NMI selftest to verify
 289           that the NMI behaves correctly.
 290
 291           This might help diagnose strange hangs that rely on NMI to
 292           function properly.
 293
 294           If unsure, say N.
 295
 296 config X86_DEBUG_STATIC_CPU_HAS
 297         bool "Debug alternatives"
 298         depends on DEBUG_KERNEL
 299         ---help---
 300           This option causes additional code to be generated which
 301           fails if static_cpu_has() is used before alternatives have
 302           run.
 303
 304           If unsure, say N.
 305
 306 endmenu