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 EMBEDDED
  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_MRST
  47         bool "Early printk for MRST platform support"
  48         depends on EARLY_PRINTK && X86_MRST
  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 DEBUG_STACKOVERFLOW
  63         bool "Check for stack overflows"
  64         depends on DEBUG_KERNEL
  65         ---help---
  66           This option will cause messages to be printed if free stack space
  67           drops below a certain limit.
  68
  69 config DEBUG_STACK_USAGE
  70         bool "Stack utilization instrumentation"
  71         depends on DEBUG_KERNEL
  72         ---help---
  73           Enables the display of the minimum amount of free stack which each
  74           task has ever had available in the sysrq-T and sysrq-P debug output.
  75
  76           This option will slow down process creation somewhat.
  77
  78 config DEBUG_PER_CPU_MAPS
  79         bool "Debug access to per_cpu maps"
  80         depends on DEBUG_KERNEL
  81         depends on SMP
  82         ---help---
  83           Say Y to verify that the per_cpu map being accessed has
  84           been setup.  Adds a fair amount of code to kernel memory
  85           and decreases performance.
  86
  87           Say N if unsure.
  88
  89 config X86_PTDUMP
  90         bool "Export kernel pagetable layout to userspace via debugfs"
  91         depends on DEBUG_KERNEL
  92         select DEBUG_FS
  93         ---help---
  94           Say Y here if you want to show the kernel pagetable layout in a
  95           debugfs file. This information is only useful for kernel developers
  96           who are working in architecture specific areas of the kernel.
  97           It is probably not a good idea to enable this feature in a production
  98           kernel.
  99           If in doubt, say "N"
 100
 101 config DEBUG_RODATA
 102         bool "Write protect kernel read-only data structures"
 103         default y
 104         depends on DEBUG_KERNEL
 105         ---help---
 106           Mark the kernel read-only data as write-protected in the pagetables,
 107           in order to catch accidental (and incorrect) writes to such const
 108           data. This is recommended so that we can catch kernel bugs sooner.
 109           If in doubt, say "Y".
 110
 111 config DEBUG_RODATA_TEST
 112         bool "Testcase for the DEBUG_RODATA feature"
 113         depends on DEBUG_RODATA
 114         default y
 115         ---help---
 116           This option enables a testcase for the DEBUG_RODATA
 117           feature as well as for the change_page_attr() infrastructure.
 118           If in doubt, say "N"
 119
 120 config DEBUG_NX_TEST
 121         tristate "Testcase for the NX non-executable stack feature"
 122         depends on DEBUG_KERNEL && m
 123         ---help---
 124           This option enables a testcase for the CPU NX capability
 125           and the software setup of this feature.
 126           If in doubt, say "N"
 127
 128 config DOUBLEFAULT
 129         default y
 130         bool "Enable doublefault exception handler" if EMBEDDED
 131         depends on X86_32
 132         ---help---
 133           This option allows trapping of rare doublefault exceptions that
 134           would otherwise cause a system to silently reboot. Disabling this
 135           option saves about 4k and might cause you much additional grey
 136           hair.
 137
 138 config IOMMU_DEBUG
 139         bool "Enable IOMMU debugging"
 140         depends on GART_IOMMU && DEBUG_KERNEL
 141         depends on X86_64
 142         ---help---
 143           Force the IOMMU to on even when you have less than 4GB of
 144           memory and add debugging code. On overflow always panic. And
 145           allow to enable IOMMU leak tracing. Can be disabled at boot
 146           time with iommu=noforce. This will also enable scatter gather
 147           list merging.  Currently not recommended for production
 148           code. When you use it make sure you have a big enough
 149           IOMMU/AGP aperture.  Most of the options enabled by this can
 150           be set more finegrained using the iommu= command line
 151           options. See Documentation/x86_64/boot-options.txt for more
 152           details.
 153
 154 config IOMMU_STRESS
 155         bool "Enable IOMMU stress-test mode"
 156         ---help---
 157           This option disables various optimizations in IOMMU related
 158           code to do real stress testing of the IOMMU code. This option
 159           will cause a performance drop and should only be enabled for
 160           testing.
 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         ---help---
 176          Perform x86 instruction decoder selftests at build time.
 177          This option is useful for checking the sanity of x86 instruction
 178          decoder code.
 179          If unsure, say "N".
 180
 181 #
 182 # IO delay types:
 183 #
 184
 185 config IO_DELAY_TYPE_0X80
 186         int
 187         default "0"
 188
 189 config IO_DELAY_TYPE_0XED
 190         int
 191         default "1"
 192
 193 config IO_DELAY_TYPE_UDELAY
 194         int
 195         default "2"
 196
 197 config IO_DELAY_TYPE_NONE
 198         int
 199         default "3"
 200
 201 choice
 202         prompt "IO delay type"
 203         default IO_DELAY_0X80
 204
 205 config IO_DELAY_0X80
 206         bool "port 0x80 based port-IO delay [recommended]"
 207         ---help---
 208           This is the traditional Linux IO delay used for in/out_p.
 209           It is the most tested hence safest selection here.
 210
 211 config IO_DELAY_0XED
 212         bool "port 0xed based port-IO delay"
 213         ---help---
 214           Use port 0xed as the IO delay. This frees up port 0x80 which is
 215           often used as a hardware-debug port.
 216
 217 config IO_DELAY_UDELAY
 218         bool "udelay based port-IO delay"
 219         ---help---
 220           Use udelay(2) as the IO delay method. This provides the delay
 221           while not having any side-effect on the IO port space.
 222
 223 config IO_DELAY_NONE
 224         bool "no port-IO delay"
 225         ---help---
 226           No port-IO delay. Will break on old boxes that require port-IO
 227           delay for certain operations. Should work on most new machines.
 228
 229 endchoice
 230
 231 if IO_DELAY_0X80
 232 config DEFAULT_IO_DELAY_TYPE
 233         int
 234         default IO_DELAY_TYPE_0X80
 235 endif
 236
 237 if IO_DELAY_0XED
 238 config DEFAULT_IO_DELAY_TYPE
 239         int
 240         default IO_DELAY_TYPE_0XED
 241 endif
 242
 243 if IO_DELAY_UDELAY
 244 config DEFAULT_IO_DELAY_TYPE
 245         int
 246         default IO_DELAY_TYPE_UDELAY
 247 endif
 248
 249 if IO_DELAY_NONE
 250 config DEFAULT_IO_DELAY_TYPE
 251         int
 252         default IO_DELAY_TYPE_NONE
 253 endif
 254
 255 config DEBUG_BOOT_PARAMS
 256         bool "Debug boot parameters"
 257         depends on DEBUG_KERNEL
 258         depends on DEBUG_FS
 259         ---help---
 260           This option will cause struct boot_params to be exported via debugfs.
 261
 262 config CPA_DEBUG
 263         bool "CPA self-test code"
 264         depends on DEBUG_KERNEL
 265         ---help---
 266           Do change_page_attr() self-tests every 30 seconds.
 267
 268 config OPTIMIZE_INLINING
 269         bool "Allow gcc to uninline functions marked 'inline'"
 270         ---help---
 271           This option determines if the kernel forces gcc to inline the functions
 272           developers have marked 'inline'. Doing so takes away freedom from gcc to
 273           do what it thinks is best, which is desirable for the gcc 3.x series of
 274           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 275           enabling this option will generate a smaller kernel there. Hopefully
 276           this algorithm is so good that allowing gcc 4.x and above to make the
 277           decision will become the default in the future. Until then this option
 278           is there to test gcc for this.
 279
 280           If unsure, say N.
 281
 282 config DEBUG_STRICT_USER_COPY_CHECKS
 283         bool "Strict copy size checks"
 284         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
 285         ---help---
 286           Enabling this option turns a certain set of sanity checks for user
 287           copy operations into compile time failures.
 288
 289           The copy_from_user() etc checks are there to help test if there
 290           are sufficient security checks on the length argument of
 291           the copy operation, by having gcc prove that the argument is
 292           within bounds.
 293
 294           If unsure, or if you run an older (pre 4.4) gcc, say N.
 295
 296 endmenu