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 NONPROMISC_DEVMEM
   9         bool "Filter access to /dev/mem"
  10         help
  11           If this option is left off, you allow userspace 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.
  15
  16           If this option is switched on, the /dev/mem file only allows
  17           userspace access to PCI space and the BIOS code and data regions.
  18           This is sufficient for dosemu and X and all common users of
  19           /dev/mem.
  20
  21           If in doubt, say Y.
  22
  23 config X86_VERBOSE_BOOTUP
  24         bool "Enable verbose x86 bootup info messages"
  25         default y
  26         help
  27           Enables the informational output from the decompression stage
  28           (e.g. bzImage) of the boot. If you disable this you will still
  29           see errors. Disable this if you want silent bootup.
  30
  31 config EARLY_PRINTK
  32         bool "Early printk" if EMBEDDED
  33         default y
  34         help
  35           Write kernel log output directly into the VGA buffer or to a serial
  36           port.
  37
  38           This is useful for kernel debugging when your machine crashes very
  39           early before the console code is initialized. For normal operation
  40           it is not recommended because it looks ugly and doesn't cooperate
  41           with klogd/syslogd or the X server. You should normally N here,
  42           unless you want to debug such a crash.
  43
  44 config DEBUG_STACKOVERFLOW
  45         bool "Check for stack overflows"
  46         depends on DEBUG_KERNEL
  47         help
  48           This option will cause messages to be printed if free stack space
  49           drops below a certain limit.
  50
  51 config DEBUG_STACK_USAGE
  52         bool "Stack utilization instrumentation"
  53         depends on DEBUG_KERNEL
  54         help
  55           Enables the display of the minimum amount of free stack which each
  56           task has ever had available in the sysrq-T and sysrq-P debug output.
  57
  58           This option will slow down process creation somewhat.
  59
  60 config DEBUG_PAGEALLOC
  61         bool "Debug page memory allocations"
  62         depends on DEBUG_KERNEL
  63         help
  64           Unmap pages from the kernel linear mapping after free_pages().
  65           This results in a large slowdown, but helps to find certain types
  66           of memory corruptions.
  67
  68 config DEBUG_PER_CPU_MAPS
  69         bool "Debug access to per_cpu maps"
  70         depends on DEBUG_KERNEL
  71         depends on X86_SMP
  72         default n
  73         help
  74           Say Y to verify that the per_cpu map being accessed has
  75           been setup.  Adds a fair amount of code to kernel memory
  76           and decreases performance.
  77
  78           Say N if unsure.
  79
  80 config X86_PTDUMP
  81         bool "Export kernel pagetable layout to userspace via debugfs"
  82         depends on DEBUG_KERNEL
  83         select DEBUG_FS
  84         help
  85           Say Y here if you want to show the kernel pagetable layout in a
  86           debugfs file. This information is only useful for kernel developers
  87           who are working in architecture specific areas of the kernel.
  88           It is probably not a good idea to enable this feature in a production
  89           kernel.
  90           If in doubt, say "N"
  91
  92 config DEBUG_RODATA
  93         bool "Write protect kernel read-only data structures"
  94         default y
  95         depends on DEBUG_KERNEL
  96         help
  97           Mark the kernel read-only data as write-protected in the pagetables,
  98           in order to catch accidental (and incorrect) writes to such const
  99           data. This is recommended so that we can catch kernel bugs sooner.
 100           If in doubt, say "Y".
 101
 102 config DIRECT_GBPAGES
 103         bool "Enable gbpages-mapped kernel pagetables"
 104         depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
 105         help
 106           Enable gigabyte pages support (if the CPU supports it). This can
 107           improve the kernel's performance a tiny bit by reducing TLB
 108           pressure.
 109
 110           This is experimental code.
 111
 112           If in doubt, say "N".
 113
 114 config DEBUG_RODATA_TEST
 115         bool "Testcase for the DEBUG_RODATA feature"
 116         depends on DEBUG_RODATA
 117         help
 118           This option enables a testcase for the DEBUG_RODATA
 119           feature as well as for the change_page_attr() infrastructure.
 120           If in doubt, say "N"
 121
 122 config DEBUG_NX_TEST
 123         tristate "Testcase for the NX non-executable stack feature"
 124         depends on DEBUG_KERNEL && m
 125         help
 126           This option enables a testcase for the CPU NX capability
 127           and the software setup of this feature.
 128           If in doubt, say "N"
 129
 130 config 4KSTACKS
 131         bool "Use 4Kb for kernel stacks instead of 8Kb"
 132         depends on X86_32
 133         help
 134           If you say Y here the kernel will use a 4Kb stacksize for the
 135           kernel stack attached to each process/thread. This facilitates
 136           running more threads on a system and also reduces the pressure
 137           on the VM subsystem for higher order allocations. This option
 138           will also use IRQ stacks to compensate for the reduced stackspace.
 139
 140 config DOUBLEFAULT
 141         default y
 142         bool "Enable doublefault exception handler" if EMBEDDED
 143         depends on X86_32
 144         help
 145           This option allows trapping of rare doublefault exceptions that
 146           would otherwise cause a system to silently reboot. Disabling this
 147           option saves about 4k and might cause you much additional grey
 148           hair.
 149
 150 config IOMMU_DEBUG
 151         bool "Enable IOMMU debugging"
 152         depends on GART_IOMMU && DEBUG_KERNEL
 153         depends on X86_64
 154         help
 155           Force the IOMMU to on even when you have less than 4GB of
 156           memory and add debugging code. On overflow always panic. And
 157           allow to enable IOMMU leak tracing. Can be disabled at boot
 158           time with iommu=noforce. This will also enable scatter gather
 159           list merging.  Currently not recommended for production
 160           code. When you use it make sure you have a big enough
 161           IOMMU/AGP aperture.  Most of the options enabled by this can
 162           be set more finegrained using the iommu= command line
 163           options. See Documentation/x86_64/boot-options.txt for more
 164           details.
 165
 166 config IOMMU_LEAK
 167         bool "IOMMU leak tracing"
 168         depends on DEBUG_KERNEL
 169         depends on IOMMU_DEBUG
 170         help
 171           Add a simple leak tracer to the IOMMU code. This is useful when you
 172           are debugging a buggy device driver that leaks IOMMU mappings.
 173
 174 #
 175 # IO delay types:
 176 #
 177
 178 config IO_DELAY_TYPE_0X80
 179         int
 180         default "0"
 181
 182 config IO_DELAY_TYPE_0XED
 183         int
 184         default "1"
 185
 186 config IO_DELAY_TYPE_UDELAY
 187         int
 188         default "2"
 189
 190 config IO_DELAY_TYPE_NONE
 191         int
 192         default "3"
 193
 194 choice
 195         prompt "IO delay type"
 196         default IO_DELAY_0X80
 197
 198 config IO_DELAY_0X80
 199         bool "port 0x80 based port-IO delay [recommended]"
 200         help
 201           This is the traditional Linux IO delay used for in/out_p.
 202           It is the most tested hence safest selection here.
 203
 204 config IO_DELAY_0XED
 205         bool "port 0xed based port-IO delay"
 206         help
 207           Use port 0xed as the IO delay. This frees up port 0x80 which is
 208           often used as a hardware-debug port.
 209
 210 config IO_DELAY_UDELAY
 211         bool "udelay based port-IO delay"
 212         help
 213           Use udelay(2) as the IO delay method. This provides the delay
 214           while not having any side-effect on the IO port space.
 215
 216 config IO_DELAY_NONE
 217         bool "no port-IO delay"
 218         help
 219           No port-IO delay. Will break on old boxes that require port-IO
 220           delay for certain operations. Should work on most new machines.
 221
 222 endchoice
 223
 224 if IO_DELAY_0X80
 225 config DEFAULT_IO_DELAY_TYPE
 226         int
 227         default IO_DELAY_TYPE_0X80
 228 endif
 229
 230 if IO_DELAY_0XED
 231 config DEFAULT_IO_DELAY_TYPE
 232         int
 233         default IO_DELAY_TYPE_0XED
 234 endif
 235
 236 if IO_DELAY_UDELAY
 237 config DEFAULT_IO_DELAY_TYPE
 238         int
 239         default IO_DELAY_TYPE_UDELAY
 240 endif
 241
 242 if IO_DELAY_NONE
 243 config DEFAULT_IO_DELAY_TYPE
 244         int
 245         default IO_DELAY_TYPE_NONE
 246 endif
 247
 248 config DEBUG_BOOT_PARAMS
 249         bool "Debug boot parameters"
 250         depends on DEBUG_KERNEL
 251         depends on DEBUG_FS
 252         help
 253           This option will cause struct boot_params to be exported via debugfs.
 254
 255 config CPA_DEBUG
 256         bool "CPA self-test code"
 257         depends on DEBUG_KERNEL
 258         help
 259           Do change_page_attr() self-tests every 30 seconds.
 260
 261 config OPTIMIZE_INLINING
 262         bool "Allow gcc to uninline functions marked 'inline'"
 263         depends on BROKEN
 264         help
 265           This option determines if the kernel forces gcc to inline the functions
 266           developers have marked 'inline'. Doing so takes away freedom from gcc to
 267           do what it thinks is best, which is desirable for the gcc 3.x series of
 268           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 269           disabling this option will generate a smaller kernel there. Hopefully
 270           this algorithm is so good that allowing gcc4 to make the decision can
 271           become the default in the future, until then this option is there to
 272           test gcc for this.
 273
 274 endmenu
 275