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 config MMIOTRACE_HOOKS
 175         bool
 176
 177 config MMIOTRACE
 178         bool "Memory mapped IO tracing"
 179         depends on DEBUG_KERNEL && PCI
 180         select TRACING
 181         select MMIOTRACE_HOOKS
 182         help
 183           Mmiotrace traces Memory Mapped I/O access and is meant for
 184           debugging and reverse engineering. It is called from the ioremap
 185           implementation and works via page faults. Tracing is disabled by
 186           default and can be enabled at run-time.
 187
 188           See Documentation/tracers/mmiotrace.txt.
 189           If you are not helping to develop drivers, say N.
 190
 191 config MMIOTRACE_TEST
 192         tristate "Test module for mmiotrace"
 193         depends on MMIOTRACE && m
 194         help
 195           This is a dumb module for testing mmiotrace. It is very dangerous
 196           as it will write garbage to IO memory starting at a given address.
 197           However, it should be safe to use on e.g. unused portion of VRAM.
 198
 199           Say N, unless you absolutely know what you are doing.
 200
 201 #
 202 # IO delay types:
 203 #
 204
 205 config IO_DELAY_TYPE_0X80
 206         int
 207         default "0"
 208
 209 config IO_DELAY_TYPE_0XED
 210         int
 211         default "1"
 212
 213 config IO_DELAY_TYPE_UDELAY
 214         int
 215         default "2"
 216
 217 config IO_DELAY_TYPE_NONE
 218         int
 219         default "3"
 220
 221 choice
 222         prompt "IO delay type"
 223         default IO_DELAY_0X80
 224
 225 config IO_DELAY_0X80
 226         bool "port 0x80 based port-IO delay [recommended]"
 227         help
 228           This is the traditional Linux IO delay used for in/out_p.
 229           It is the most tested hence safest selection here.
 230
 231 config IO_DELAY_0XED
 232         bool "port 0xed based port-IO delay"
 233         help
 234           Use port 0xed as the IO delay. This frees up port 0x80 which is
 235           often used as a hardware-debug port.
 236
 237 config IO_DELAY_UDELAY
 238         bool "udelay based port-IO delay"
 239         help
 240           Use udelay(2) as the IO delay method. This provides the delay
 241           while not having any side-effect on the IO port space.
 242
 243 config IO_DELAY_NONE
 244         bool "no port-IO delay"
 245         help
 246           No port-IO delay. Will break on old boxes that require port-IO
 247           delay for certain operations. Should work on most new machines.
 248
 249 endchoice
 250
 251 if IO_DELAY_0X80
 252 config DEFAULT_IO_DELAY_TYPE
 253         int
 254         default IO_DELAY_TYPE_0X80
 255 endif
 256
 257 if IO_DELAY_0XED
 258 config DEFAULT_IO_DELAY_TYPE
 259         int
 260         default IO_DELAY_TYPE_0XED
 261 endif
 262
 263 if IO_DELAY_UDELAY
 264 config DEFAULT_IO_DELAY_TYPE
 265         int
 266         default IO_DELAY_TYPE_UDELAY
 267 endif
 268
 269 if IO_DELAY_NONE
 270 config DEFAULT_IO_DELAY_TYPE
 271         int
 272         default IO_DELAY_TYPE_NONE
 273 endif
 274
 275 config DEBUG_BOOT_PARAMS
 276         bool "Debug boot parameters"
 277         depends on DEBUG_KERNEL
 278         depends on DEBUG_FS
 279         help
 280           This option will cause struct boot_params to be exported via debugfs.
 281
 282 config CPA_DEBUG
 283         bool "CPA self-test code"
 284         depends on DEBUG_KERNEL
 285         help
 286           Do change_page_attr() self-tests every 30 seconds.
 287
 288 config OPTIMIZE_INLINING
 289         bool "Allow gcc to uninline functions marked 'inline'"
 290         help
 291           This option determines if the kernel forces gcc to inline the functions
 292           developers have marked 'inline'. Doing so takes away freedom from gcc to
 293           do what it thinks is best, which is desirable for the gcc 3.x series of
 294           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 295           disabling this option will generate a smaller kernel there. Hopefully
 296           this algorithm is so good that allowing gcc4 to make the decision can
 297           become the default in the future, until then this option is there to
 298           test gcc for this.
 299
 300           If unsure, say N.
 301
 302 endmenu
 303