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 EARLY_PRINTK
  24         bool "Early printk" if EMBEDDED
  25         default y
  26         help
  27           Write kernel log output directly into the VGA buffer or to a serial
  28           port.
  29
  30           This is useful for kernel debugging when your machine crashes very
  31           early before the console code is initialized. For normal operation
  32           it is not recommended because it looks ugly and doesn't cooperate
  33           with klogd/syslogd or the X server. You should normally N here,
  34           unless you want to debug such a crash.
  35
  36 config DEBUG_STACKOVERFLOW
  37         bool "Check for stack overflows"
  38         depends on DEBUG_KERNEL
  39         help
  40           This option will cause messages to be printed if free stack space
  41           drops below a certain limit.
  42
  43 config DEBUG_STACK_USAGE
  44         bool "Stack utilization instrumentation"
  45         depends on DEBUG_KERNEL
  46         help
  47           Enables the display of the minimum amount of free stack which each
  48           task has ever had available in the sysrq-T and sysrq-P debug output.
  49
  50           This option will slow down process creation somewhat.
  51
  52 config DEBUG_PAGEALLOC
  53         bool "Debug page memory allocations"
  54         depends on DEBUG_KERNEL
  55         help
  56           Unmap pages from the kernel linear mapping after free_pages().
  57           This results in a large slowdown, but helps to find certain types
  58           of memory corruptions.
  59
  60 config DEBUG_PER_CPU_MAPS
  61         bool "Debug access to per_cpu maps"
  62         depends on DEBUG_KERNEL
  63         depends on X86_64_SMP
  64         default n
  65         help
  66           Say Y to verify that the per_cpu map being accessed has
  67           been setup.  Adds a fair amount of code to kernel memory
  68           and decreases performance.
  69
  70           Say N if unsure.
  71
  72 config X86_PTDUMP
  73         bool "Export kernel pagetable layout to userspace via debugfs"
  74         depends on DEBUG_KERNEL
  75         select DEBUG_FS
  76         help
  77           Say Y here if you want to show the kernel pagetable layout in a
  78           debugfs file. This information is only useful for kernel developers
  79           who are working in architecture specific areas of the kernel.
  80           It is probably not a good idea to enable this feature in a production
  81           kernel.
  82           If in doubt, say "N"
  83
  84 config DEBUG_RODATA
  85         bool "Write protect kernel read-only data structures"
  86         default y
  87         depends on DEBUG_KERNEL
  88         help
  89           Mark the kernel read-only data as write-protected in the pagetables,
  90           in order to catch accidental (and incorrect) writes to such const
  91           data. This is recommended so that we can catch kernel bugs sooner.
  92           If in doubt, say "Y".
  93
  94 config DIRECT_GBPAGES
  95         bool "Enable gbpages-mapped kernel pagetables"
  96         depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
  97         help
  98           Enable gigabyte pages support (if the CPU supports it). This can
  99           improve the kernel's performance a tiny bit by reducing TLB
 100           pressure.
 101
 102           This is experimental code.
 103
 104           If in doubt, say "N".
 105
 106 config DEBUG_RODATA_TEST
 107         bool "Testcase for the DEBUG_RODATA feature"
 108         depends on DEBUG_RODATA
 109         help
 110           This option enables a testcase for the DEBUG_RODATA
 111           feature as well as for the change_page_attr() infrastructure.
 112           If in doubt, say "N"
 113
 114 config DEBUG_NX_TEST
 115         tristate "Testcase for the NX non-executable stack feature"
 116         depends on DEBUG_KERNEL && m
 117         help
 118           This option enables a testcase for the CPU NX capability
 119           and the software setup of this feature.
 120           If in doubt, say "N"
 121
 122 config 4KSTACKS
 123         bool "Use 4Kb for kernel stacks instead of 8Kb"
 124         depends on X86_32
 125         help
 126           If you say Y here the kernel will use a 4Kb stacksize for the
 127           kernel stack attached to each process/thread. This facilitates
 128           running more threads on a system and also reduces the pressure
 129           on the VM subsystem for higher order allocations. This option
 130           will also use IRQ stacks to compensate for the reduced stackspace.
 131
 132 config X86_FIND_SMP_CONFIG
 133         def_bool y
 134         depends on X86_LOCAL_APIC || X86_VOYAGER
 135         depends on X86_32
 136
 137 config X86_MPPARSE
 138         def_bool y
 139         depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) || X86_64
 140
 141 config DOUBLEFAULT
 142         default y
 143         bool "Enable doublefault exception handler" if EMBEDDED
 144         depends on X86_32
 145         help
 146           This option allows trapping of rare doublefault exceptions that
 147           would otherwise cause a system to silently reboot. Disabling this
 148           option saves about 4k and might cause you much additional grey
 149           hair.
 150
 151 config IOMMU_DEBUG
 152         bool "Enable IOMMU debugging"
 153         depends on GART_IOMMU && DEBUG_KERNEL
 154         depends on X86_64
 155         help
 156           Force the IOMMU to on even when you have less than 4GB of
 157           memory and add debugging code. On overflow always panic. And
 158           allow to enable IOMMU leak tracing. Can be disabled at boot
 159           time with iommu=noforce. This will also enable scatter gather
 160           list merging.  Currently not recommended for production
 161           code. When you use it make sure you have a big enough
 162           IOMMU/AGP aperture.  Most of the options enabled by this can
 163           be set more finegrained using the iommu= command line
 164           options. See Documentation/x86_64/boot-options.txt for more
 165           details.
 166
 167 config IOMMU_LEAK
 168         bool "IOMMU leak tracing"
 169         depends on DEBUG_KERNEL
 170         depends on IOMMU_DEBUG
 171         help
 172           Add a simple leak tracer to the IOMMU code. This is useful when you
 173           are debugging a buggy device driver that leaks IOMMU mappings.
 174
 175 #
 176 # IO delay types:
 177 #
 178
 179 config IO_DELAY_TYPE_0X80
 180         int
 181         default "0"
 182
 183 config IO_DELAY_TYPE_0XED
 184         int
 185         default "1"
 186
 187 config IO_DELAY_TYPE_UDELAY
 188         int
 189         default "2"
 190
 191 config IO_DELAY_TYPE_NONE
 192         int
 193         default "3"
 194
 195 choice
 196         prompt "IO delay type"
 197         default IO_DELAY_0X80
 198
 199 config IO_DELAY_0X80
 200         bool "port 0x80 based port-IO delay [recommended]"
 201         help
 202           This is the traditional Linux IO delay used for in/out_p.
 203           It is the most tested hence safest selection here.
 204
 205 config IO_DELAY_0XED
 206         bool "port 0xed based port-IO delay"
 207         help
 208           Use port 0xed as the IO delay. This frees up port 0x80 which is
 209           often used as a hardware-debug port.
 210
 211 config IO_DELAY_UDELAY
 212         bool "udelay based port-IO delay"
 213         help
 214           Use udelay(2) as the IO delay method. This provides the delay
 215           while not having any side-effect on the IO port space.
 216
 217 config IO_DELAY_NONE
 218         bool "no port-IO delay"
 219         help
 220           No port-IO delay. Will break on old boxes that require port-IO
 221           delay for certain operations. Should work on most new machines.
 222
 223 endchoice
 224
 225 if IO_DELAY_0X80
 226 config DEFAULT_IO_DELAY_TYPE
 227         int
 228         default IO_DELAY_TYPE_0X80
 229 endif
 230
 231 if IO_DELAY_0XED
 232 config DEFAULT_IO_DELAY_TYPE
 233         int
 234         default IO_DELAY_TYPE_0XED
 235 endif
 236
 237 if IO_DELAY_UDELAY
 238 config DEFAULT_IO_DELAY_TYPE
 239         int
 240         default IO_DELAY_TYPE_UDELAY
 241 endif
 242
 243 if IO_DELAY_NONE
 244 config DEFAULT_IO_DELAY_TYPE
 245         int
 246         default IO_DELAY_TYPE_NONE
 247 endif
 248
 249 config DEBUG_BOOT_PARAMS
 250         bool "Debug boot parameters"
 251         depends on DEBUG_KERNEL
 252         depends on DEBUG_FS
 253         help
 254           This option will cause struct boot_params to be exported via debugfs.
 255
 256 config CPA_DEBUG
 257         bool "CPA self-test code"
 258         depends on DEBUG_KERNEL
 259         help
 260           Do change_page_attr() self-tests every 30 seconds.
 261
 262 config OPTIMIZE_INLINING
 263         bool "Allow gcc to uninline functions marked 'inline'"
 264         depends on BROKEN
 265         help
 266           This option determines if the kernel forces gcc to inline the functions
 267           developers have marked 'inline'. Doing so takes away freedom from gcc to
 268           do what it thinks is best, which is desirable for the gcc 3.x series of
 269           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 270           disabling this option will generate a smaller kernel there. Hopefully
 271           this algorithm is so good that allowing gcc4 to make the decision can
 272           become the default in the future, until then this option is there to
 273           test gcc for this.
 274
 275 endmenu
 276