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 "Disable promiscuous /dev/mem"
  10         help
  11           The /dev/mem file by default only allows userspace access to PCI
  12           space and the BIOS code and data regions. This is sufficient for
  13           dosemu and X and all common users of /dev/mem. With this config
  14           option, you allow userspace access to all of memory, including
  15           kernel and userspace memory. Accidental access to this is
  16           obviously disasterous, but specific access can be used by people
  17           debugging the kernel.
  18
  19 config EARLY_PRINTK
  20         bool "Early printk" if EMBEDDED
  21         default y
  22         help
  23           Write kernel log output directly into the VGA buffer or to a serial
  24           port.
  25
  26           This is useful for kernel debugging when your machine crashes very
  27           early before the console code is initialized. For normal operation
  28           it is not recommended because it looks ugly and doesn't cooperate
  29           with klogd/syslogd or the X server. You should normally N here,
  30           unless you want to debug such a crash.
  31
  32 config DEBUG_STACKOVERFLOW
  33         bool "Check for stack overflows"
  34         depends on DEBUG_KERNEL
  35         help
  36           This option will cause messages to be printed if free stack space
  37           drops below a certain limit.
  38
  39 config DEBUG_STACK_USAGE
  40         bool "Stack utilization instrumentation"
  41         depends on DEBUG_KERNEL
  42         help
  43           Enables the display of the minimum amount of free stack which each
  44           task has ever had available in the sysrq-T and sysrq-P debug output.
  45
  46           This option will slow down process creation somewhat.
  47
  48 config DEBUG_PAGEALLOC
  49         bool "Debug page memory allocations"
  50         depends on DEBUG_KERNEL
  51         help
  52           Unmap pages from the kernel linear mapping after free_pages().
  53           This results in a large slowdown, but helps to find certain types
  54           of memory corruptions.
  55
  56 config DEBUG_PER_CPU_MAPS
  57         bool "Debug access to per_cpu maps"
  58         depends on DEBUG_KERNEL
  59         depends on X86_64_SMP
  60         default n
  61         help
  62           Say Y to verify that the per_cpu map being accessed has
  63           been setup.  Adds a fair amount of code to kernel memory
  64           and decreases performance.
  65
  66           Say N if unsure.
  67
  68 config X86_PTDUMP
  69         bool "Export kernel pagetable layout to userspace via debugfs"
  70         depends on DEBUG_KERNEL
  71         select DEBUG_FS
  72         help
  73           Say Y here if you want to show the kernel pagetable layout in a
  74           debugfs file. This information is only useful for kernel developers
  75           who are working in architecture specific areas of the kernel.
  76           It is probably not a good idea to enable this feature in a production
  77           kernel.
  78           If in doubt, say "N"
  79
  80 config DEBUG_RODATA
  81         bool "Write protect kernel read-only data structures"
  82         default y
  83         depends on DEBUG_KERNEL
  84         help
  85           Mark the kernel read-only data as write-protected in the pagetables,
  86           in order to catch accidental (and incorrect) writes to such const
  87           data. This is recommended so that we can catch kernel bugs sooner.
  88           If in doubt, say "Y".
  89
  90 config DIRECT_GBPAGES
  91         bool "Enable gbpages-mapped kernel pagetables"
  92         depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
  93         help
  94           Enable gigabyte pages support (if the CPU supports it). This can
  95           improve the kernel's performance a tiny bit by reducing TLB
  96           pressure.
  97
  98           This is experimental code.
  99
 100           If in doubt, say "N".
 101
 102 config DEBUG_RODATA_TEST
 103         bool "Testcase for the DEBUG_RODATA feature"
 104         depends on DEBUG_RODATA
 105         help
 106           This option enables a testcase for the DEBUG_RODATA
 107           feature as well as for the change_page_attr() infrastructure.
 108           If in doubt, say "N"
 109
 110 config DEBUG_NX_TEST
 111         tristate "Testcase for the NX non-executable stack feature"
 112         depends on DEBUG_KERNEL && m
 113         help
 114           This option enables a testcase for the CPU NX capability
 115           and the software setup of this feature.
 116           If in doubt, say "N"
 117
 118 config 4KSTACKS
 119         bool "Use 4Kb for kernel stacks instead of 8Kb"
 120         depends on X86_32
 121         help
 122           If you say Y here the kernel will use a 4Kb stacksize for the
 123           kernel stack attached to each process/thread. This facilitates
 124           running more threads on a system and also reduces the pressure
 125           on the VM subsystem for higher order allocations. This option
 126           will also use IRQ stacks to compensate for the reduced stackspace.
 127
 128 config X86_FIND_SMP_CONFIG
 129         def_bool y
 130         depends on X86_LOCAL_APIC || X86_VOYAGER
 131         depends on X86_32
 132
 133 config X86_MPPARSE
 134         def_bool y
 135         depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) || X86_64
 136
 137 config DOUBLEFAULT
 138         default y
 139         bool "Enable doublefault exception handler" if EMBEDDED
 140         depends on X86_32
 141         help
 142           This option allows trapping of rare doublefault exceptions that
 143           would otherwise cause a system to silently reboot. Disabling this
 144           option saves about 4k and might cause you much additional grey
 145           hair.
 146
 147 config IOMMU_DEBUG
 148         bool "Enable IOMMU debugging"
 149         depends on GART_IOMMU && DEBUG_KERNEL
 150         depends on X86_64
 151         help
 152           Force the IOMMU to on even when you have less than 4GB of
 153           memory and add debugging code. On overflow always panic. And
 154           allow to enable IOMMU leak tracing. Can be disabled at boot
 155           time with iommu=noforce. This will also enable scatter gather
 156           list merging.  Currently not recommended for production
 157           code. When you use it make sure you have a big enough
 158           IOMMU/AGP aperture.  Most of the options enabled by this can
 159           be set more finegrained using the iommu= command line
 160           options. See Documentation/x86_64/boot-options.txt for more
 161           details.
 162
 163 config IOMMU_LEAK
 164         bool "IOMMU leak tracing"
 165         depends on DEBUG_KERNEL
 166         depends on IOMMU_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 #
 172 # IO delay types:
 173 #
 174
 175 config IO_DELAY_TYPE_0X80
 176         int
 177         default "0"
 178
 179 config IO_DELAY_TYPE_0XED
 180         int
 181         default "1"
 182
 183 config IO_DELAY_TYPE_UDELAY
 184         int
 185         default "2"
 186
 187 config IO_DELAY_TYPE_NONE
 188         int
 189         default "3"
 190
 191 choice
 192         prompt "IO delay type"
 193         default IO_DELAY_0X80
 194
 195 config IO_DELAY_0X80
 196         bool "port 0x80 based port-IO delay [recommended]"
 197         help
 198           This is the traditional Linux IO delay used for in/out_p.
 199           It is the most tested hence safest selection here.
 200
 201 config IO_DELAY_0XED
 202         bool "port 0xed based port-IO delay"
 203         help
 204           Use port 0xed as the IO delay. This frees up port 0x80 which is
 205           often used as a hardware-debug port.
 206
 207 config IO_DELAY_UDELAY
 208         bool "udelay based port-IO delay"
 209         help
 210           Use udelay(2) as the IO delay method. This provides the delay
 211           while not having any side-effect on the IO port space.
 212
 213 config IO_DELAY_NONE
 214         bool "no port-IO delay"
 215         help
 216           No port-IO delay. Will break on old boxes that require port-IO
 217           delay for certain operations. Should work on most new machines.
 218
 219 endchoice
 220
 221 if IO_DELAY_0X80
 222 config DEFAULT_IO_DELAY_TYPE
 223         int
 224         default IO_DELAY_TYPE_0X80
 225 endif
 226
 227 if IO_DELAY_0XED
 228 config DEFAULT_IO_DELAY_TYPE
 229         int
 230         default IO_DELAY_TYPE_0XED
 231 endif
 232
 233 if IO_DELAY_UDELAY
 234 config DEFAULT_IO_DELAY_TYPE
 235         int
 236         default IO_DELAY_TYPE_UDELAY
 237 endif
 238
 239 if IO_DELAY_NONE
 240 config DEFAULT_IO_DELAY_TYPE
 241         int
 242         default IO_DELAY_TYPE_NONE
 243 endif
 244
 245 config DEBUG_BOOT_PARAMS
 246         bool "Debug boot parameters"
 247         depends on DEBUG_KERNEL
 248         depends on DEBUG_FS
 249         help
 250           This option will cause struct boot_params to be exported via debugfs.
 251
 252 config CPA_DEBUG
 253         bool "CPA self-test code"
 254         depends on DEBUG_KERNEL
 255         help
 256           Do change_page_attr() self-tests every 30 seconds.
 257
 258 config OPTIMIZE_INLINING
 259         bool "Allow gcc to uninline functions marked 'inline'"
 260         depends on BROKEN
 261         help
 262           This option determines if the kernel forces gcc to inline the functions
 263           developers have marked 'inline'. Doing so takes away freedom from gcc to
 264           do what it thinks is best, which is desirable for the gcc 3.x series of
 265           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 266           disabling this option will generate a smaller kernel there. Hopefully
 267           this algorithm is so good that allowing gcc4 to make the decision can
 268           become the default in the future, until then this option is there to
 269           test gcc for this.
 270
 271 endmenu
 272