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 EXPERT
  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_MRST
  47         bool "Early printk for MRST platform support"
  48         depends on EARLY_PRINTK && X86_MRST
  49
  50 config EARLY_PRINTK_DBGP
  51         bool "Early printk via EHCI debug port"
  52         depends on EARLY_PRINTK && PCI
  53         ---help---
  54           Write kernel log output directly into the EHCI debug port.
  55
  56           This is useful for kernel debugging when your machine crashes very
  57           early before the console code is initialized. For normal operation
  58           it is not recommended because it looks ugly and doesn't cooperate
  59           with klogd/syslogd or the X server. You should normally N here,
  60           unless you want to debug such a crash. You need usb debug device.
  61
  62 config DEBUG_STACKOVERFLOW
  63         bool "Check for stack overflows"
  64         depends on DEBUG_KERNEL
  65         ---help---
  66           This option will cause messages to be printed if free stack space
  67           drops below a certain limit.
  68
  69 config DEBUG_STACK_USAGE
  70         bool "Stack utilization instrumentation"
  71         depends on DEBUG_KERNEL
  72         ---help---
  73           Enables the display of the minimum amount of free stack which each
  74           task has ever had available in the sysrq-T and sysrq-P debug output.
  75
  76           This option will slow down process creation somewhat.
  77
  78 config DEBUG_PER_CPU_MAPS
  79         bool "Debug access to per_cpu maps"
  80         depends on DEBUG_KERNEL
  81         depends on SMP
  82         ---help---
  83           Say Y to verify that the per_cpu map being accessed has
  84           been setup.  Adds a fair amount of code to kernel memory
  85           and decreases performance.
  86
  87           Say N if unsure.
  88
  89 config X86_PTDUMP
  90         bool "Export kernel pagetable layout to userspace via debugfs"
  91         depends on DEBUG_KERNEL
  92         select DEBUG_FS
  93         ---help---
  94           Say Y here if you want to show the kernel pagetable layout in a
  95           debugfs file. This information is only useful for kernel developers
  96           who are working in architecture specific areas of the kernel.
  97           It is probably not a good idea to enable this feature in a production
  98           kernel.
  99           If in doubt, say "N"
 100
 101 config DEBUG_RODATA
 102         bool "Write protect kernel read-only data structures"
 103         default y
 104         depends on DEBUG_KERNEL
 105         ---help---
 106           Mark the kernel read-only data as write-protected in the pagetables,
 107           in order to catch accidental (and incorrect) writes to such const
 108           data. This is recommended so that we can catch kernel bugs sooner.
 109           If in doubt, say "Y".
 110
 111 config DEBUG_RODATA_TEST
 112         bool "Testcase for the DEBUG_RODATA feature"
 113         depends on DEBUG_RODATA
 114         default y
 115         ---help---
 116           This option enables a testcase for the DEBUG_RODATA
 117           feature as well as for the change_page_attr() infrastructure.
 118           If in doubt, say "N"
 119
 120 config DEBUG_SET_MODULE_RONX
 121         bool "Set loadable kernel module data as NX and text as RO"
 122         depends on MODULES
 123         ---help---
 124           This option helps catch unintended modifications to loadable
 125           kernel module's text and read-only data. It also prevents execution
 126           of module data. Such protection may interfere with run-time code
 127           patching and dynamic kernel tracing - and they might also protect
 128           against certain classes of kernel exploits.
 129           If in doubt, say "N".
 130
 131 config DEBUG_NX_TEST
 132         tristate "Testcase for the NX non-executable stack feature"
 133         depends on DEBUG_KERNEL && m
 134         ---help---
 135           This option enables a testcase for the CPU NX capability
 136           and the software setup of this feature.
 137           If in doubt, say "N"
 138
 139 config DOUBLEFAULT
 140         default y
 141         bool "Enable doublefault exception handler" if EXPERT
 142         depends on X86_32
 143         ---help---
 144           This option allows trapping of rare doublefault exceptions that
 145           would otherwise cause a system to silently reboot. Disabling this
 146           option saves about 4k and might cause you much additional grey
 147           hair.
 148
 149 config IOMMU_DEBUG
 150         bool "Enable IOMMU debugging"
 151         depends on GART_IOMMU && DEBUG_KERNEL
 152         depends on X86_64
 153         ---help---
 154           Force the IOMMU to on even when you have less than 4GB of
 155           memory and add debugging code. On overflow always panic. And
 156           allow to enable IOMMU leak tracing. Can be disabled at boot
 157           time with iommu=noforce. This will also enable scatter gather
 158           list merging.  Currently not recommended for production
 159           code. When you use it make sure you have a big enough
 160           IOMMU/AGP aperture.  Most of the options enabled by this can
 161           be set more finegrained using the iommu= command line
 162           options. See Documentation/x86_64/boot-options.txt for more
 163           details.
 164
 165 config IOMMU_STRESS
 166         bool "Enable IOMMU stress-test mode"
 167         ---help---
 168           This option disables various optimizations in IOMMU related
 169           code to do real stress testing of the IOMMU code. This option
 170           will cause a performance drop and should only be enabled for
 171           testing.
 172
 173 config IOMMU_LEAK
 174         bool "IOMMU leak tracing"
 175         depends on IOMMU_DEBUG && DMA_API_DEBUG
 176         ---help---
 177           Add a simple leak tracer to the IOMMU code. This is useful when you
 178           are debugging a buggy device driver that leaks IOMMU mappings.
 179
 180 config HAVE_MMIOTRACE_SUPPORT
 181         def_bool y
 182
 183 config X86_DECODER_SELFTEST
 184         bool "x86 instruction decoder selftest"
 185         depends on DEBUG_KERNEL && KPROBES
 186         ---help---
 187          Perform x86 instruction decoder selftests at build time.
 188          This option is useful for checking the sanity of x86 instruction
 189          decoder code.
 190          If unsure, say "N".
 191
 192 #
 193 # IO delay types:
 194 #
 195
 196 config IO_DELAY_TYPE_0X80
 197         int
 198         default "0"
 199
 200 config IO_DELAY_TYPE_0XED
 201         int
 202         default "1"
 203
 204 config IO_DELAY_TYPE_UDELAY
 205         int
 206         default "2"
 207
 208 config IO_DELAY_TYPE_NONE
 209         int
 210         default "3"
 211
 212 choice
 213         prompt "IO delay type"
 214         default IO_DELAY_0X80
 215
 216 config IO_DELAY_0X80
 217         bool "port 0x80 based port-IO delay [recommended]"
 218         ---help---
 219           This is the traditional Linux IO delay used for in/out_p.
 220           It is the most tested hence safest selection here.
 221
 222 config IO_DELAY_0XED
 223         bool "port 0xed based port-IO delay"
 224         ---help---
 225           Use port 0xed as the IO delay. This frees up port 0x80 which is
 226           often used as a hardware-debug port.
 227
 228 config IO_DELAY_UDELAY
 229         bool "udelay based port-IO delay"
 230         ---help---
 231           Use udelay(2) as the IO delay method. This provides the delay
 232           while not having any side-effect on the IO port space.
 233
 234 config IO_DELAY_NONE
 235         bool "no port-IO delay"
 236         ---help---
 237           No port-IO delay. Will break on old boxes that require port-IO
 238           delay for certain operations. Should work on most new machines.
 239
 240 endchoice
 241
 242 if IO_DELAY_0X80
 243 config DEFAULT_IO_DELAY_TYPE
 244         int
 245         default IO_DELAY_TYPE_0X80
 246 endif
 247
 248 if IO_DELAY_0XED
 249 config DEFAULT_IO_DELAY_TYPE
 250         int
 251         default IO_DELAY_TYPE_0XED
 252 endif
 253
 254 if IO_DELAY_UDELAY
 255 config DEFAULT_IO_DELAY_TYPE
 256         int
 257         default IO_DELAY_TYPE_UDELAY
 258 endif
 259
 260 if IO_DELAY_NONE
 261 config DEFAULT_IO_DELAY_TYPE
 262         int
 263         default IO_DELAY_TYPE_NONE
 264 endif
 265
 266 config DEBUG_BOOT_PARAMS
 267         bool "Debug boot parameters"
 268         depends on DEBUG_KERNEL
 269         depends on DEBUG_FS
 270         ---help---
 271           This option will cause struct boot_params to be exported via debugfs.
 272
 273 config CPA_DEBUG
 274         bool "CPA self-test code"
 275         depends on DEBUG_KERNEL
 276         ---help---
 277           Do change_page_attr() self-tests every 30 seconds.
 278
 279 config OPTIMIZE_INLINING
 280         bool "Allow gcc to uninline functions marked 'inline'"
 281         ---help---
 282           This option determines if the kernel forces gcc to inline the functions
 283           developers have marked 'inline'. Doing so takes away freedom from gcc to
 284           do what it thinks is best, which is desirable for the gcc 3.x series of
 285           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 286           enabling this option will generate a smaller kernel there. Hopefully
 287           this algorithm is so good that allowing gcc 4.x and above to make the
 288           decision will become the default in the future. Until then this option
 289           is there to test gcc for this.
 290
 291           If unsure, say N.
 292
 293 config DEBUG_STRICT_USER_COPY_CHECKS
 294         bool "Strict copy size checks"
 295         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
 296         ---help---
 297           Enabling this option turns a certain set of sanity checks for user
 298           copy operations into compile time failures.
 299
 300           The copy_from_user() etc checks are there to help test if there
 301           are sufficient security checks on the length argument of
 302           the copy operation, by having gcc prove that the argument is
 303           within bounds.
 304
 305           If unsure, or if you run an older (pre 4.4) gcc, say N.
 306
 307 endmenu