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 X86_PTDUMP
  70         bool "Export kernel pagetable layout to userspace via debugfs"
  71         depends on DEBUG_KERNEL
  72         select DEBUG_FS
  73         ---help---
  74           Say Y here if you want to show the kernel pagetable layout in a
  75           debugfs file. This information is only useful for kernel developers
  76           who are working in architecture specific areas of the kernel.
  77           It is probably not a good idea to enable this feature in a production
  78           kernel.
  79           If in doubt, say "N"
  80
  81 config DEBUG_RODATA
  82         bool "Write protect kernel read-only data structures"
  83         default y
  84         depends on DEBUG_KERNEL
  85         ---help---
  86           Mark the kernel read-only data as write-protected in the pagetables,
  87           in order to catch accidental (and incorrect) writes to such const
  88           data. This is recommended so that we can catch kernel bugs sooner.
  89           If in doubt, say "Y".
  90
  91 config DEBUG_RODATA_TEST
  92         bool "Testcase for the DEBUG_RODATA feature"
  93         depends on DEBUG_RODATA
  94         default y
  95         ---help---
  96           This option enables a testcase for the DEBUG_RODATA
  97           feature as well as for the change_page_attr() infrastructure.
  98           If in doubt, say "N"
  99
 100 config DEBUG_SET_MODULE_RONX
 101         bool "Set loadable kernel module data as NX and text as RO"
 102         depends on MODULES
 103         ---help---
 104           This option helps catch unintended modifications to loadable
 105           kernel module's text and read-only data. It also prevents execution
 106           of module data. Such protection may interfere with run-time code
 107           patching and dynamic kernel tracing - and they might also protect
 108           against certain classes of kernel exploits.
 109           If in doubt, say "N".
 110
 111 config DEBUG_NX_TEST
 112         tristate "Testcase for the NX non-executable stack feature"
 113         depends on DEBUG_KERNEL && m
 114         ---help---
 115           This option enables a testcase for the CPU NX capability
 116           and the software setup of this feature.
 117           If in doubt, say "N"
 118
 119 config DOUBLEFAULT
 120         default y
 121         bool "Enable doublefault exception handler" if EXPERT
 122         depends on X86_32
 123         ---help---
 124           This option allows trapping of rare doublefault exceptions that
 125           would otherwise cause a system to silently reboot. Disabling this
 126           option saves about 4k and might cause you much additional grey
 127           hair.
 128
 129 config IOMMU_DEBUG
 130         bool "Enable IOMMU debugging"
 131         depends on GART_IOMMU && DEBUG_KERNEL
 132         depends on X86_64
 133         ---help---
 134           Force the IOMMU to on even when you have less than 4GB of
 135           memory and add debugging code. On overflow always panic. And
 136           allow to enable IOMMU leak tracing. Can be disabled at boot
 137           time with iommu=noforce. This will also enable scatter gather
 138           list merging.  Currently not recommended for production
 139           code. When you use it make sure you have a big enough
 140           IOMMU/AGP aperture.  Most of the options enabled by this can
 141           be set more finegrained using the iommu= command line
 142           options. See Documentation/x86/x86_64/boot-options.txt for more
 143           details.
 144
 145 config IOMMU_STRESS
 146         bool "Enable IOMMU stress-test mode"
 147         ---help---
 148           This option disables various optimizations in IOMMU related
 149           code to do real stress testing of the IOMMU code. This option
 150           will cause a performance drop and should only be enabled for
 151           testing.
 152
 153 config IOMMU_LEAK
 154         bool "IOMMU leak tracing"
 155         depends on IOMMU_DEBUG && DMA_API_DEBUG
 156         ---help---
 157           Add a simple leak tracer to the IOMMU code. This is useful when you
 158           are debugging a buggy device driver that leaks IOMMU mappings.
 159
 160 config HAVE_MMIOTRACE_SUPPORT
 161         def_bool y
 162
 163 config X86_DECODER_SELFTEST
 164         bool "x86 instruction decoder selftest"
 165         depends on DEBUG_KERNEL && KPROBES
 166         ---help---
 167          Perform x86 instruction decoder selftests at build time.
 168          This option is useful for checking the sanity of x86 instruction
 169          decoder code.
 170          If unsure, say "N".
 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 config OPTIMIZE_INLINING
 260         bool "Allow gcc to uninline functions marked 'inline'"
 261         ---help---
 262           This option determines if the kernel forces gcc to inline the functions
 263           developers have marked 'inline'. Doing so takes away freedom from gcc to
 264           do what it thinks is best, which is desirable for the gcc 3.x series of
 265           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 266           enabling this option will generate a smaller kernel there. Hopefully
 267           this algorithm is so good that allowing gcc 4.x and above to make the
 268           decision will become the default in the future. Until then this option
 269           is there to test gcc for this.
 270
 271           If unsure, say N.
 272
 273 config DEBUG_STRICT_USER_COPY_CHECKS
 274         bool "Strict copy size checks"
 275         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
 276         ---help---
 277           Enabling this option turns a certain set of sanity checks for user
 278           copy operations into compile time failures.
 279
 280           The copy_from_user() etc checks are there to help test if there
 281           are sufficient security checks on the length argument of
 282           the copy operation, by having gcc prove that the argument is
 283           within bounds.
 284
 285           If unsure, or if you run an older (pre 4.4) gcc, say N.
 286
 287 endmenu