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_INTEL_MID
  47         bool "Early printk for Intel MID platform support"
  48         depends on EARLY_PRINTK && X86_INTEL_MID
  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           Say Y here if you want to check the overflows of kernel, IRQ
  67           and exception stacks. This option will cause messages of the
  68           stacks in detail when free stack space drops below a certain
  69           limit.
  70           If in doubt, say "N".
  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 DEBUG_RODATA_TEST
  95         bool "Testcase for the DEBUG_RODATA feature"
  96         depends on DEBUG_RODATA
  97         default y
  98         ---help---
  99           This option enables a testcase for the DEBUG_RODATA
 100           feature as well as for the change_page_attr() infrastructure.
 101           If in doubt, say "N"
 102
 103 config DEBUG_SET_MODULE_RONX
 104         bool "Set loadable kernel module data as NX and text as RO"
 105         depends on MODULES
 106         ---help---
 107           This option helps catch unintended modifications to loadable
 108           kernel module's text and read-only data. It also prevents execution
 109           of module data. Such protection may interfere with run-time code
 110           patching and dynamic kernel tracing - and they might also protect
 111           against certain classes of kernel exploits.
 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 DOUBLEFAULT
 123         default y
 124         bool "Enable doublefault exception handler" if EXPERT
 125         depends on X86_32
 126         ---help---
 127           This option allows trapping of rare doublefault exceptions that
 128           would otherwise cause a system to silently reboot. Disabling this
 129           option saves about 4k and might cause you much additional grey
 130           hair.
 131
 132 config IOMMU_DEBUG
 133         bool "Enable IOMMU debugging"
 134         depends on GART_IOMMU && DEBUG_KERNEL
 135         depends on X86_64
 136         ---help---
 137           Force the IOMMU to on even when you have less than 4GB of
 138           memory and add debugging code. On overflow always panic. And
 139           allow to enable IOMMU leak tracing. Can be disabled at boot
 140           time with iommu=noforce. This will also enable scatter gather
 141           list merging.  Currently not recommended for production
 142           code. When you use it make sure you have a big enough
 143           IOMMU/AGP aperture.  Most of the options enabled by this can
 144           be set more finegrained using the iommu= command line
 145           options. See Documentation/x86/x86_64/boot-options.txt for more
 146           details.
 147
 148 config IOMMU_STRESS
 149         bool "Enable IOMMU stress-test mode"
 150         ---help---
 151           This option disables various optimizations in IOMMU related
 152           code to do real stress testing of the IOMMU code. This option
 153           will cause a performance drop and should only be enabled for
 154           testing.
 155
 156 config IOMMU_LEAK
 157         bool "IOMMU leak tracing"
 158         depends on IOMMU_DEBUG && DMA_API_DEBUG
 159         ---help---
 160           Add a simple leak tracer to the IOMMU code. This is useful when you
 161           are debugging a buggy device driver that leaks IOMMU mappings.
 162
 163 config HAVE_MMIOTRACE_SUPPORT
 164         def_bool y
 165
 166 config X86_DECODER_SELFTEST
 167         bool "x86 instruction decoder selftest"
 168         depends on DEBUG_KERNEL && KPROBES
 169         ---help---
 170          Perform x86 instruction decoder selftests at build time.
 171          This option is useful for checking the sanity of x86 instruction
 172          decoder code.
 173          If unsure, say "N".
 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         ---help---
 265           This option determines if the kernel forces gcc to inline the functions
 266           developers have marked 'inline'. Doing so takes away freedom from gcc to
 267           do what it thinks is best, which is desirable for the gcc 3.x series of
 268           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 269           enabling this option will generate a smaller kernel there. Hopefully
 270           this algorithm is so good that allowing gcc 4.x and above to make the
 271           decision will become the default in the future. Until then this option
 272           is there to test gcc for this.
 273
 274           If unsure, say N.
 275
 276 config DEBUG_STRICT_USER_COPY_CHECKS
 277         bool "Strict copy size checks"
 278         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
 279         ---help---
 280           Enabling this option turns a certain set of sanity checks for user
 281           copy operations into compile time failures.
 282
 283           The copy_from_user() etc checks are there to help test if there
 284           are sufficient security checks on the length argument of
 285           the copy operation, by having gcc prove that the argument is
 286           within bounds.
 287
 288           If unsure, or if you run an older (pre 4.4) gcc, say N.
 289
 290 config DEBUG_NMI_SELFTEST
 291         bool "NMI Selftest"
 292         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 293         ---help---
 294           Enabling this option turns on a quick NMI selftest to verify
 295           that the NMI behaves correctly.
 296
 297           This might help diagnose strange hangs that rely on NMI to
 298           function properly.
 299
 300           If unsure, say N.
 301
 302 endmenu