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