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 DEBUG_RODATA_TEST
 118         bool "Testcase for the DEBUG_RODATA feature"
 119         depends on DEBUG_RODATA
 120         help
 121           This option enables a testcase for the DEBUG_RODATA
 122           feature as well as for the change_page_attr() infrastructure.
 123           If in doubt, say "N"
 124
 125 config DEBUG_NX_TEST
 126         tristate "Testcase for the NX non-executable stack feature"
 127         depends on DEBUG_KERNEL && m
 128         help
 129           This option enables a testcase for the CPU NX capability
 130           and the software setup of this feature.
 131           If in doubt, say "N"
 132
 133 config 4KSTACKS
 134         bool "Use 4Kb for kernel stacks instead of 8Kb"
 135         depends on X86_32
 136         help
 137           If you say Y here the kernel will use a 4Kb stacksize for the
 138           kernel stack attached to each process/thread. This facilitates
 139           running more threads on a system and also reduces the pressure
 140           on the VM subsystem for higher order allocations. This option
 141           will also use IRQ stacks to compensate for the reduced stackspace.
 142
 143 config DOUBLEFAULT
 144         default y
 145         bool "Enable doublefault exception handler" if EMBEDDED
 146         depends on X86_32
 147         help
 148           This option allows trapping of rare doublefault exceptions that
 149           would otherwise cause a system to silently reboot. Disabling this
 150           option saves about 4k and might cause you much additional grey
 151           hair.
 152
 153 config IOMMU_DEBUG
 154         bool "Enable IOMMU debugging"
 155         depends on GART_IOMMU && DEBUG_KERNEL
 156         depends on X86_64
 157         help
 158           Force the IOMMU to on even when you have less than 4GB of
 159           memory and add debugging code. On overflow always panic. And
 160           allow to enable IOMMU leak tracing. Can be disabled at boot
 161           time with iommu=noforce. This will also enable scatter gather
 162           list merging.  Currently not recommended for production
 163           code. When you use it make sure you have a big enough
 164           IOMMU/AGP aperture.  Most of the options enabled by this can
 165           be set more finegrained using the iommu= command line
 166           options. See Documentation/x86_64/boot-options.txt for more
 167           details.
 168
 169 config IOMMU_LEAK
 170         bool "IOMMU leak tracing"
 171         depends on DEBUG_KERNEL
 172         depends on IOMMU_DEBUG
 173         help
 174           Add a simple leak tracer to the IOMMU code. This is useful when you
 175           are debugging a buggy device driver that leaks IOMMU mappings.
 176
 177 config MMIOTRACE
 178         bool "Memory mapped IO tracing"
 179         depends on DEBUG_KERNEL && PCI
 180         select TRACING
 181         help
 182           Mmiotrace traces Memory Mapped I/O access and is meant for
 183           debugging and reverse engineering. It is called from the ioremap
 184           implementation and works via page faults. Tracing is disabled by
 185           default and can be enabled at run-time.
 186
 187           See Documentation/tracers/mmiotrace.txt.
 188           If you are not helping to develop drivers, say N.
 189
 190 config MMIOTRACE_TEST
 191         tristate "Test module for mmiotrace"
 192         depends on MMIOTRACE && m
 193         help
 194           This is a dumb module for testing mmiotrace. It is very dangerous
 195           as it will write garbage to IO memory starting at a given address.
 196           However, it should be safe to use on e.g. unused portion of VRAM.
 197
 198           Say N, unless you absolutely know what you are doing.
 199
 200 #
 201 # IO delay types:
 202 #
 203
 204 config IO_DELAY_TYPE_0X80
 205         int
 206         default "0"
 207
 208 config IO_DELAY_TYPE_0XED
 209         int
 210         default "1"
 211
 212 config IO_DELAY_TYPE_UDELAY
 213         int
 214         default "2"
 215
 216 config IO_DELAY_TYPE_NONE
 217         int
 218         default "3"
 219
 220 choice
 221         prompt "IO delay type"
 222         default IO_DELAY_0X80
 223
 224 config IO_DELAY_0X80
 225         bool "port 0x80 based port-IO delay [recommended]"
 226         help
 227           This is the traditional Linux IO delay used for in/out_p.
 228           It is the most tested hence safest selection here.
 229
 230 config IO_DELAY_0XED
 231         bool "port 0xed based port-IO delay"
 232         help
 233           Use port 0xed as the IO delay. This frees up port 0x80 which is
 234           often used as a hardware-debug port.
 235
 236 config IO_DELAY_UDELAY
 237         bool "udelay based port-IO delay"
 238         help
 239           Use udelay(2) as the IO delay method. This provides the delay
 240           while not having any side-effect on the IO port space.
 241
 242 config IO_DELAY_NONE
 243         bool "no port-IO delay"
 244         help
 245           No port-IO delay. Will break on old boxes that require port-IO
 246           delay for certain operations. Should work on most new machines.
 247
 248 endchoice
 249
 250 if IO_DELAY_0X80
 251 config DEFAULT_IO_DELAY_TYPE
 252         int
 253         default IO_DELAY_TYPE_0X80
 254 endif
 255
 256 if IO_DELAY_0XED
 257 config DEFAULT_IO_DELAY_TYPE
 258         int
 259         default IO_DELAY_TYPE_0XED
 260 endif
 261
 262 if IO_DELAY_UDELAY
 263 config DEFAULT_IO_DELAY_TYPE
 264         int
 265         default IO_DELAY_TYPE_UDELAY
 266 endif
 267
 268 if IO_DELAY_NONE
 269 config DEFAULT_IO_DELAY_TYPE
 270         int
 271         default IO_DELAY_TYPE_NONE
 272 endif
 273
 274 config DEBUG_BOOT_PARAMS
 275         bool "Debug boot parameters"
 276         depends on DEBUG_KERNEL
 277         depends on DEBUG_FS
 278         help
 279           This option will cause struct boot_params to be exported via debugfs.
 280
 281 config CPA_DEBUG
 282         bool "CPA self-test code"
 283         depends on DEBUG_KERNEL
 284         help
 285           Do change_page_attr() self-tests every 30 seconds.
 286
 287 config OPTIMIZE_INLINING
 288         bool "Allow gcc to uninline functions marked 'inline'"
 289         help
 290           This option determines if the kernel forces gcc to inline the functions
 291           developers have marked 'inline'. Doing so takes away freedom from gcc to
 292           do what it thinks is best, which is desirable for the gcc 3.x series of
 293           compilers. The gcc 4.x series have a rewritten inlining algorithm and
 294           enabling this option will generate a smaller kernel there. Hopefully
 295           this algorithm is so good that allowing gcc 4.x and above to make the
 296           decision will become the default in the future. Until then this option
 297           is there to test gcc for this.
 298
 299           If unsure, say N.
 300
 301 endmenu
 302