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 EMBEDDED
  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_DBGP
  47         bool "Early printk via EHCI debug port"
  48         default n
  49         depends on EARLY_PRINTK && PCI
  50         help
  51           Write kernel log output directly into the EHCI debug port.
  52
  53           This is useful for kernel debugging when your machine crashes very
  54           early before the console code is initialized. For normal operation
  55           it is not recommended because it looks ugly and doesn't cooperate
  56           with klogd/syslogd or the X server. You should normally N here,
  57           unless you want to debug such a crash. You need usb debug device.
  58
  59 config DEBUG_STACKOVERFLOW
  60         bool "Check for stack overflows"
  61         depends on DEBUG_KERNEL
  62         help
  63           This option will cause messages to be printed if free stack space
  64           drops below a certain limit.
  65
  66 config DEBUG_STACK_USAGE
  67         bool "Stack utilization instrumentation"
  68         depends on DEBUG_KERNEL
  69         help
  70           Enables the display of the minimum amount of free stack which each
  71           task has ever had available in the sysrq-T and sysrq-P debug output.
  72
  73           This option will slow down process creation somewhat.
  74
  75 config DEBUG_PAGEALLOC
  76         bool "Debug page memory allocations"
  77         depends on DEBUG_KERNEL
  78         help
  79           Unmap pages from the kernel linear mapping after free_pages().
  80           This results in a large slowdown, but helps to find certain types
  81           of memory corruptions.
  82
  83 config DEBUG_PER_CPU_MAPS
  84         bool "Debug access to per_cpu maps"
  85         depends on DEBUG_KERNEL
  86         depends on X86_SMP
  87         default n
  88         help
  89           Say Y to verify that the per_cpu map being accessed has
  90           been setup.  Adds a fair amount of code to kernel memory
  91           and decreases performance.
  92
  93           Say N if unsure.
  94
  95 config X86_PTDUMP
  96         bool "Export kernel pagetable layout to userspace via debugfs"
  97         depends on DEBUG_KERNEL
  98         select DEBUG_FS
  99         help
 100           Say Y here if you want to show the kernel pagetable layout in a
 101           debugfs file. This information is only useful for kernel developers
 102           who are working in architecture specific areas of the kernel.
 103           It is probably not a good idea to enable this feature in a production
 104           kernel.
 105           If in doubt, say "N"
 106
 107 config DEBUG_RODATA
 108         bool "Write protect kernel read-only data structures"
 109         default y
 110         depends on DEBUG_KERNEL
 111         help
 112           Mark the kernel read-only data as write-protected in the pagetables,
 113           in order to catch accidental (and incorrect) writes to such const
 114           data. This is recommended so that we can catch kernel bugs sooner.
 115           If in doubt, say "Y".
 116
 117 config DIRECT_GBPAGES
 118         bool "Enable gbpages-mapped kernel pagetables"
 119         depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
 120         help
 121           Enable gigabyte pages support (if the CPU supports it). This can
 122           improve the kernel's performance a tiny bit by reducing TLB
 123           pressure.
 124
 125           This is experimental code.
 126
 127           If in doubt, say "N".
 128
 129 config DEBUG_RODATA_TEST
 130         bool "Testcase for the DEBUG_RODATA feature"
 131         depends on DEBUG_RODATA
 132         help
 133           This option enables a testcase for the DEBUG_RODATA
 134           feature as well as for the change_page_attr() infrastructure.
 135           If in doubt, say "N"
 136
 137 config DEBUG_NX_TEST
 138         tristate "Testcase for the NX non-executable stack feature"
 139         depends on DEBUG_KERNEL && m
 140         help
 141           This option enables a testcase for the CPU NX capability
 142           and the software setup of this feature.
 143           If in doubt, say "N"
 144
 145 config 4KSTACKS
 146         bool "Use 4Kb for kernel stacks instead of 8Kb"
 147         depends on X86_32
 148         help
 149           If you say Y here the kernel will use a 4Kb stacksize for the
 150           kernel stack attached to each process/thread. This facilitates
 151           running more threads on a system and also reduces the pressure
 152           on the VM subsystem for higher order allocations. This option
 153           will also use IRQ stacks to compensate for the reduced stackspace.
 154
 155 config DOUBLEFAULT
 156         default y
 157         bool "Enable doublefault exception handler" if EMBEDDED
 158         depends on X86_32
 159         help
 160           This option allows trapping of rare doublefault exceptions that
 161           would otherwise cause a system to silently reboot. Disabling this
 162           option saves about 4k and might cause you much additional grey
 163           hair.
 164
 165 config IOMMU_DEBUG
 166         bool "Enable IOMMU debugging"
 167         depends on GART_IOMMU && DEBUG_KERNEL
 168         depends on X86_64
 169         help
 170           Force the IOMMU to on even when you have less than 4GB of
 171           memory and add debugging code. On overflow always panic. And
 172           allow to enable IOMMU leak tracing. Can be disabled at boot
 173           time with iommu=noforce. This will also enable scatter gather
 174           list merging.  Currently not recommended for production
 175           code. When you use it make sure you have a big enough
 176           IOMMU/AGP aperture.  Most of the options enabled by this can
 177           be set more finegrained using the iommu= command line
 178           options. See Documentation/x86_64/boot-options.txt for more
 179           details.
 180
 181 config IOMMU_LEAK
 182         bool "IOMMU leak tracing"
 183         depends on DEBUG_KERNEL
 184         depends on IOMMU_DEBUG
 185         help
 186           Add a simple leak tracer to the IOMMU code. This is useful when you
 187           are debugging a buggy device driver that leaks IOMMU mappings.
 188
 189 config MMIOTRACE
 190         bool "Memory mapped IO tracing"
 191         depends on DEBUG_KERNEL && PCI
 192         select TRACING
 193         help
 194           Mmiotrace traces Memory Mapped I/O access and is meant for
 195           debugging and reverse engineering. It is called from the ioremap
 196           implementation and works via page faults. Tracing is disabled by
 197           default and can be enabled at run-time.
 198
 199           See Documentation/tracers/mmiotrace.txt.
 200           If you are not helping to develop drivers, say N.
 201
 202 config MMIOTRACE_TEST
 203         tristate "Test module for mmiotrace"
 204         depends on MMIOTRACE && m
 205         help
 206           This is a dumb module for testing mmiotrace. It is very dangerous
 207           as it will write garbage to IO memory starting at a given address.
 208           However, it should be safe to use on e.g. unused portion of VRAM.
 209
 210           Say N, unless you absolutely know what you are doing.
 211
 212 #
 213 # IO delay types:
 214 #
 215
 216 config IO_DELAY_TYPE_0X80
 217         int
 218         default "0"
 219
 220 config IO_DELAY_TYPE_0XED
 221         int
 222         default "1"
 223
 224 config IO_DELAY_TYPE_UDELAY
 225         int
 226         default "2"
 227
 228 config IO_DELAY_TYPE_NONE
 229         int
 230         default "3"
 231
 232 choice
 233         prompt "IO delay type"
 234         default IO_DELAY_0X80
 235
 236 config IO_DELAY_0X80
 237         bool "port 0x80 based port-IO delay [recommended]"
 238         help
 239           This is the traditional Linux IO delay used for in/out_p.
 240           It is the most tested hence safest selection here.
 241
 242 config IO_DELAY_0XED
 243         bool "port 0xed based port-IO delay"
 244         help
 245           Use port 0xed as the IO delay. This frees up port 0x80 which is
 246           often used as a hardware-debug port.
 247
 248 config IO_DELAY_UDELAY
 249         bool "udelay based port-IO delay"
 250         help
 251           Use udelay(2) as the IO delay method. This provides the delay
 252           while not having any side-effect on the IO port space.
 253
 254 config IO_DELAY_NONE
 255         bool "no port-IO delay"
 256         help
 257           No port-IO delay. Will break on old boxes that require port-IO
 258           delay for certain operations. Should work on most new machines.
 259
 260 endchoice
 261
 262 if IO_DELAY_0X80
 263 config DEFAULT_IO_DELAY_TYPE
 264         int
 265         default IO_DELAY_TYPE_0X80
 266 endif
 267
 268 if IO_DELAY_0XED
 269 config DEFAULT_IO_DELAY_TYPE
 270         int
 271         default IO_DELAY_TYPE_0XED
 272 endif
 273
 274 if IO_DELAY_UDELAY
 275 config DEFAULT_IO_DELAY_TYPE
 276         int
 277         default IO_DELAY_TYPE_UDELAY
 278 endif
 279
 280 if IO_DELAY_NONE
 281 config DEFAULT_IO_DELAY_TYPE
 282         int
 283         default IO_DELAY_TYPE_NONE
 284 endif
 285
 286 config DEBUG_BOOT_PARAMS
 287         bool "Debug boot parameters"
 288         depends on DEBUG_KERNEL
 289         depends on DEBUG_FS
 290         help
 291           This option will cause struct boot_params to be exported via debugfs.
 292
 293 config CPA_DEBUG
 294         bool "CPA self-test code"
 295         depends on DEBUG_KERNEL
 296         help
 297           Do change_page_attr() self-tests every 30 seconds.
 298
 299 config OPTIMIZE_INLINING
 300         bool "Allow gcc to uninline functions marked 'inline'"
 301         help
 302           This option determines if the kernel forces gcc to inline the functions
 303           developers have marked 'inline'. Doing so takes away freedom from gcc to
 304           do what it thinks is best, which is desirable for the gcc 3.x series of
 305           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 306           disabling this option will generate a smaller kernel there. Hopefully
 307           this algorithm is so good that allowing gcc4 to make the decision can
 308           become the default in the future, until then this option is there to
 309           test gcc for this.
 310
 311           If unsure, say N.
 312
 313 endmenu
 314