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_STRESS
 163         bool "Enable IOMMU stress-test mode"
 164         ---help---
 165           This option disables various optimizations in IOMMU related
 166           code to do real stress testing of the IOMMU code. This option
 167           will cause a performance drop and should only be enabled for
 168           testing.
 169
 170 config IOMMU_LEAK
 171         bool "IOMMU leak tracing"
 172         depends on IOMMU_DEBUG && DMA_API_DEBUG
 173         ---help---
 174           Add a simple leak tracer to the IOMMU code. This is useful when you
 175           are debugging a buggy device driver that leaks IOMMU mappings.
 176
 177 config X86_DS_SELFTEST
 178     bool "DS selftest"
 179     default y
 180     depends on DEBUG_KERNEL
 181     depends on X86_DS
 182         ---help---
 183           Perform Debug Store selftests at boot time.
 184           If in doubt, say "N".
 185
 186 config HAVE_MMIOTRACE_SUPPORT
 187         def_bool y
 188
 189 config X86_DECODER_SELFTEST
 190         bool "x86 instruction decoder selftest"
 191         depends on DEBUG_KERNEL && KPROBES
 192         ---help---
 193          Perform x86 instruction decoder selftests at build time.
 194          This option is useful for checking the sanity of x86 instruction
 195          decoder code.
 196          If unsure, say "N".
 197
 198 #
 199 # IO delay types:
 200 #
 201
 202 config IO_DELAY_TYPE_0X80
 203         int
 204         default "0"
 205
 206 config IO_DELAY_TYPE_0XED
 207         int
 208         default "1"
 209
 210 config IO_DELAY_TYPE_UDELAY
 211         int
 212         default "2"
 213
 214 config IO_DELAY_TYPE_NONE
 215         int
 216         default "3"
 217
 218 choice
 219         prompt "IO delay type"
 220         default IO_DELAY_0X80
 221
 222 config IO_DELAY_0X80
 223         bool "port 0x80 based port-IO delay [recommended]"
 224         ---help---
 225           This is the traditional Linux IO delay used for in/out_p.
 226           It is the most tested hence safest selection here.
 227
 228 config IO_DELAY_0XED
 229         bool "port 0xed based port-IO delay"
 230         ---help---
 231           Use port 0xed as the IO delay. This frees up port 0x80 which is
 232           often used as a hardware-debug port.
 233
 234 config IO_DELAY_UDELAY
 235         bool "udelay based port-IO delay"
 236         ---help---
 237           Use udelay(2) as the IO delay method. This provides the delay
 238           while not having any side-effect on the IO port space.
 239
 240 config IO_DELAY_NONE
 241         bool "no port-IO delay"
 242         ---help---
 243           No port-IO delay. Will break on old boxes that require port-IO
 244           delay for certain operations. Should work on most new machines.
 245
 246 endchoice
 247
 248 if IO_DELAY_0X80
 249 config DEFAULT_IO_DELAY_TYPE
 250         int
 251         default IO_DELAY_TYPE_0X80
 252 endif
 253
 254 if IO_DELAY_0XED
 255 config DEFAULT_IO_DELAY_TYPE
 256         int
 257         default IO_DELAY_TYPE_0XED
 258 endif
 259
 260 if IO_DELAY_UDELAY
 261 config DEFAULT_IO_DELAY_TYPE
 262         int
 263         default IO_DELAY_TYPE_UDELAY
 264 endif
 265
 266 if IO_DELAY_NONE
 267 config DEFAULT_IO_DELAY_TYPE
 268         int
 269         default IO_DELAY_TYPE_NONE
 270 endif
 271
 272 config DEBUG_BOOT_PARAMS
 273         bool "Debug boot parameters"
 274         depends on DEBUG_KERNEL
 275         depends on DEBUG_FS
 276         ---help---
 277           This option will cause struct boot_params to be exported via debugfs.
 278
 279 config CPA_DEBUG
 280         bool "CPA self-test code"
 281         depends on DEBUG_KERNEL
 282         ---help---
 283           Do change_page_attr() self-tests every 30 seconds.
 284
 285 config OPTIMIZE_INLINING
 286         bool "Allow gcc to uninline functions marked 'inline'"
 287         ---help---
 288           This option determines if the kernel forces gcc to inline the functions
 289           developers have marked 'inline'. Doing so takes away freedom from gcc to
 290           do what it thinks is best, which is desirable for the gcc 3.x series of
 291           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 292           enabling this option will generate a smaller kernel there. Hopefully
 293           this algorithm is so good that allowing gcc 4.x and above to make the
 294           decision will become the default in the future. Until then this option
 295           is there to test gcc for this.
 296
 297           If unsure, say N.
 298
 299 config DEBUG_STRICT_USER_COPY_CHECKS
 300         bool "Strict copy size checks"
 301         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
 302         ---help---
 303           Enabling this option turns a certain set of sanity checks for user
 304           copy operations into compile time failures.
 305
 306           The copy_from_user() etc checks are there to help test if there
 307           are sufficient security checks on the length argument of
 308           the copy operation, by having gcc prove that the argument is
 309           within bounds.
 310
 311           If unsure, or if you run an older (pre 4.4) gcc, say N.
 312
 313 endmenu