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 EARLY_PRINTK_EFI
  63         bool "Early printk via the EFI framebuffer"
  64         depends on EFI && EARLY_PRINTK
  65         select FONT_SUPPORT
  66         ---help---
  67           Write kernel log output directly into the EFI framebuffer.
  68
  69           This is useful for kernel debugging when your machine crashes very
  70           early before the console code is initialized.
  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         ---help---
 126           This option allows trapping of rare doublefault exceptions that
 127           would otherwise cause a system to silently reboot. Disabling this
 128           option saves about 4k and might cause you much additional grey
 129           hair.
 130
 131 config DEBUG_TLBFLUSH
 132         bool "Set upper limit of TLB entries to flush one-by-one"
 133         depends on DEBUG_KERNEL
 134         ---help---
 135
 136         X86-only for now.
 137
 138         This option allows the user to tune the amount of TLB entries the
 139         kernel flushes one-by-one instead of doing a full TLB flush. In
 140         certain situations, the former is cheaper. This is controlled by the
 141         tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
 142         to -1, the code flushes the whole TLB unconditionally. Otherwise,
 143         for positive values of it, the kernel will use single TLB entry
 144         invalidating instructions according to the following formula:
 145
 146         flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
 147
 148         If in doubt, say "N".
 149
 150 config IOMMU_DEBUG
 151         bool "Enable IOMMU debugging"
 152         depends on GART_IOMMU && DEBUG_KERNEL
 153         depends on X86_64
 154         ---help---
 155           Force the IOMMU to on even when you have less than 4GB of
 156           memory and add debugging code. On overflow always panic. And
 157           allow to enable IOMMU leak tracing. Can be disabled at boot
 158           time with iommu=noforce. This will also enable scatter gather
 159           list merging.  Currently not recommended for production
 160           code. When you use it make sure you have a big enough
 161           IOMMU/AGP aperture.  Most of the options enabled by this can
 162           be set more finegrained using the iommu= command line
 163           options. See Documentation/x86/x86_64/boot-options.txt for more
 164           details.
 165
 166 config IOMMU_STRESS
 167         bool "Enable IOMMU stress-test mode"
 168         ---help---
 169           This option disables various optimizations in IOMMU related
 170           code to do real stress testing of the IOMMU code. This option
 171           will cause a performance drop and should only be enabled for
 172           testing.
 173
 174 config IOMMU_LEAK
 175         bool "IOMMU leak tracing"
 176         depends on IOMMU_DEBUG && DMA_API_DEBUG
 177         ---help---
 178           Add a simple leak tracer to the IOMMU code. This is useful when you
 179           are debugging a buggy device driver that leaks IOMMU mappings.
 180
 181 config HAVE_MMIOTRACE_SUPPORT
 182         def_bool y
 183
 184 config X86_DECODER_SELFTEST
 185         bool "x86 instruction decoder selftest"
 186         depends on DEBUG_KERNEL && KPROBES
 187         ---help---
 188          Perform x86 instruction decoder selftests at build time.
 189          This option is useful for checking the sanity of x86 instruction
 190          decoder code.
 191          If unsure, say "N".
 192
 193 #
 194 # IO delay types:
 195 #
 196
 197 config IO_DELAY_TYPE_0X80
 198         int
 199         default "0"
 200
 201 config IO_DELAY_TYPE_0XED
 202         int
 203         default "1"
 204
 205 config IO_DELAY_TYPE_UDELAY
 206         int
 207         default "2"
 208
 209 config IO_DELAY_TYPE_NONE
 210         int
 211         default "3"
 212
 213 choice
 214         prompt "IO delay type"
 215         default IO_DELAY_0X80
 216
 217 config IO_DELAY_0X80
 218         bool "port 0x80 based port-IO delay [recommended]"
 219         ---help---
 220           This is the traditional Linux IO delay used for in/out_p.
 221           It is the most tested hence safest selection here.
 222
 223 config IO_DELAY_0XED
 224         bool "port 0xed based port-IO delay"
 225         ---help---
 226           Use port 0xed as the IO delay. This frees up port 0x80 which is
 227           often used as a hardware-debug port.
 228
 229 config IO_DELAY_UDELAY
 230         bool "udelay based port-IO delay"
 231         ---help---
 232           Use udelay(2) as the IO delay method. This provides the delay
 233           while not having any side-effect on the IO port space.
 234
 235 config IO_DELAY_NONE
 236         bool "no port-IO delay"
 237         ---help---
 238           No port-IO delay. Will break on old boxes that require port-IO
 239           delay for certain operations. Should work on most new machines.
 240
 241 endchoice
 242
 243 if IO_DELAY_0X80
 244 config DEFAULT_IO_DELAY_TYPE
 245         int
 246         default IO_DELAY_TYPE_0X80
 247 endif
 248
 249 if IO_DELAY_0XED
 250 config DEFAULT_IO_DELAY_TYPE
 251         int
 252         default IO_DELAY_TYPE_0XED
 253 endif
 254
 255 if IO_DELAY_UDELAY
 256 config DEFAULT_IO_DELAY_TYPE
 257         int
 258         default IO_DELAY_TYPE_UDELAY
 259 endif
 260
 261 if IO_DELAY_NONE
 262 config DEFAULT_IO_DELAY_TYPE
 263         int
 264         default IO_DELAY_TYPE_NONE
 265 endif
 266
 267 config DEBUG_BOOT_PARAMS
 268         bool "Debug boot parameters"
 269         depends on DEBUG_KERNEL
 270         depends on DEBUG_FS
 271         ---help---
 272           This option will cause struct boot_params to be exported via debugfs.
 273
 274 config CPA_DEBUG
 275         bool "CPA self-test code"
 276         depends on DEBUG_KERNEL
 277         ---help---
 278           Do change_page_attr() self-tests every 30 seconds.
 279
 280 config OPTIMIZE_INLINING
 281         bool "Allow gcc to uninline functions marked 'inline'"
 282         ---help---
 283           This option determines if the kernel forces gcc to inline the functions
 284           developers have marked 'inline'. Doing so takes away freedom from gcc to
 285           do what it thinks is best, which is desirable for the gcc 3.x series of
 286           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 287           enabling this option will generate a smaller kernel there. Hopefully
 288           this algorithm is so good that allowing gcc 4.x and above to make the
 289           decision will become the default in the future. Until then this option
 290           is there to test gcc for this.
 291
 292           If unsure, say N.
 293
 294 config DEBUG_NMI_SELFTEST
 295         bool "NMI Selftest"
 296         depends on DEBUG_KERNEL && X86_LOCAL_APIC
 297         ---help---
 298           Enabling this option turns on a quick NMI selftest to verify
 299           that the NMI behaves correctly.
 300
 301           This might help diagnose strange hangs that rely on NMI to
 302           function properly.
 303
 304           If unsure, say N.
 305
 306 config X86_DEBUG_STATIC_CPU_HAS
 307         bool "Debug alternatives"
 308         depends on DEBUG_KERNEL
 309         ---help---
 310           This option causes additional code to be generated which
 311           fails if static_cpu_has() is used before alternatives have
 312           run.
 313
 314           If unsure, say N.
 315
 316 endmenu