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