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