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         default y
 122         help
 123           If you say Y here the kernel will use a 4Kb stacksize for the
 124           kernel stack attached to each process/thread. This facilitates
 125           running more threads on a system and also reduces the pressure
 126           on the VM subsystem for higher order allocations. This option
 127           will also use IRQ stacks to compensate for the reduced stackspace.
 128
 129 config X86_FIND_SMP_CONFIG
 130         def_bool y
 131         depends on X86_LOCAL_APIC || X86_VOYAGER
 132         depends on X86_32
 133
 134 config X86_MPPARSE
 135         def_bool y
 136         depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) || X86_64
 137
 138 config DOUBLEFAULT
 139         default y
 140         bool "Enable doublefault exception handler" if EMBEDDED
 141         depends on X86_32
 142         help
 143           This option allows trapping of rare doublefault exceptions that
 144           would otherwise cause a system to silently reboot. Disabling this
 145           option saves about 4k and might cause you much additional grey
 146           hair.
 147
 148 config IOMMU_DEBUG
 149         bool "Enable IOMMU debugging"
 150         depends on GART_IOMMU && DEBUG_KERNEL
 151         depends on X86_64
 152         help
 153           Force the IOMMU to on even when you have less than 4GB of
 154           memory and add debugging code. On overflow always panic. And
 155           allow to enable IOMMU leak tracing. Can be disabled at boot
 156           time with iommu=noforce. This will also enable scatter gather
 157           list merging.  Currently not recommended for production
 158           code. When you use it make sure you have a big enough
 159           IOMMU/AGP aperture.  Most of the options enabled by this can
 160           be set more finegrained using the iommu= command line
 161           options. See Documentation/x86_64/boot-options.txt for more
 162           details.
 163
 164 config IOMMU_LEAK
 165         bool "IOMMU leak tracing"
 166         depends on DEBUG_KERNEL
 167         depends on IOMMU_DEBUG
 168         help
 169           Add a simple leak tracer to the IOMMU code. This is useful when you
 170           are debugging a buggy device driver that leaks IOMMU mappings.
 171
 172 #
 173 # IO delay types:
 174 #
 175
 176 config IO_DELAY_TYPE_0X80
 177         int
 178         default "0"
 179
 180 config IO_DELAY_TYPE_0XED
 181         int
 182         default "1"
 183
 184 config IO_DELAY_TYPE_UDELAY
 185         int
 186         default "2"
 187
 188 config IO_DELAY_TYPE_NONE
 189         int
 190         default "3"
 191
 192 choice
 193         prompt "IO delay type"
 194         default IO_DELAY_0X80
 195
 196 config IO_DELAY_0X80
 197         bool "port 0x80 based port-IO delay [recommended]"
 198         help
 199           This is the traditional Linux IO delay used for in/out_p.
 200           It is the most tested hence safest selection here.
 201
 202 config IO_DELAY_0XED
 203         bool "port 0xed based port-IO delay"
 204         help
 205           Use port 0xed as the IO delay. This frees up port 0x80 which is
 206           often used as a hardware-debug port.
 207
 208 config IO_DELAY_UDELAY
 209         bool "udelay based port-IO delay"
 210         help
 211           Use udelay(2) as the IO delay method. This provides the delay
 212           while not having any side-effect on the IO port space.
 213
 214 config IO_DELAY_NONE
 215         bool "no port-IO delay"
 216         help
 217           No port-IO delay. Will break on old boxes that require port-IO
 218           delay for certain operations. Should work on most new machines.
 219
 220 endchoice
 221
 222 if IO_DELAY_0X80
 223 config DEFAULT_IO_DELAY_TYPE
 224         int
 225         default IO_DELAY_TYPE_0X80
 226 endif
 227
 228 if IO_DELAY_0XED
 229 config DEFAULT_IO_DELAY_TYPE
 230         int
 231         default IO_DELAY_TYPE_0XED
 232 endif
 233
 234 if IO_DELAY_UDELAY
 235 config DEFAULT_IO_DELAY_TYPE
 236         int
 237         default IO_DELAY_TYPE_UDELAY
 238 endif
 239
 240 if IO_DELAY_NONE
 241 config DEFAULT_IO_DELAY_TYPE
 242         int
 243         default IO_DELAY_TYPE_NONE
 244 endif
 245
 246 config DEBUG_BOOT_PARAMS
 247         bool "Debug boot parameters"
 248         depends on DEBUG_KERNEL
 249         depends on DEBUG_FS
 250         help
 251           This option will cause struct boot_params to be exported via debugfs.
 252
 253 config CPA_DEBUG
 254         bool "CPA self-test code"
 255         depends on DEBUG_KERNEL
 256         help
 257           Do change_page_attr() self-tests every 30 seconds.
 258
 259 endmenu
 260
 261 config OPTIMIZE_INLINING
 262         bool "Allow gcc to uninline functions marked 'inline'"
 263         default y
 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.