1menu "Kernel hacking" 2 3config TRACE_IRQFLAGS_SUPPORT 4 def_bool y 5 6source "lib/Kconfig.debug" 7 8config 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 25config 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 33config 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 46config 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 59config 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 66config 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 75config 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 83config 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 95config 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 107config 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 117config 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 125config 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 133config 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 143config 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 153config 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 169config 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 177config HAVE_MMIOTRACE_SUPPORT 178 def_bool y 179 180# 181# IO delay types: 182# 183 184config IO_DELAY_TYPE_0X80 185 int 186 default "0" 187 188config IO_DELAY_TYPE_0XED 189 int 190 default "1" 191 192config IO_DELAY_TYPE_UDELAY 193 int 194 default "2" 195 196config IO_DELAY_TYPE_NONE 197 int 198 default "3" 199 200choice 201 prompt "IO delay type" 202 default IO_DELAY_0X80 203 204config IO_DELAY_0X80 205 bool "port 0x80 based port-IO delay [recommended]" 206 help 207 This is the traditional Linux IO delay used for in/out_p. 208 It is the most tested hence safest selection here. 209 210config IO_DELAY_0XED 211 bool "port 0xed based port-IO delay" 212 help 213 Use port 0xed as the IO delay. This frees up port 0x80 which is 214 often used as a hardware-debug port. 215 216config IO_DELAY_UDELAY 217 bool "udelay based port-IO delay" 218 help 219 Use udelay(2) as the IO delay method. This provides the delay 220 while not having any side-effect on the IO port space. 221 222config IO_DELAY_NONE 223 bool "no port-IO delay" 224 help 225 No port-IO delay. Will break on old boxes that require port-IO 226 delay for certain operations. Should work on most new machines. 227 228endchoice 229 230if IO_DELAY_0X80 231config DEFAULT_IO_DELAY_TYPE 232 int 233 default IO_DELAY_TYPE_0X80 234endif 235 236if IO_DELAY_0XED 237config DEFAULT_IO_DELAY_TYPE 238 int 239 default IO_DELAY_TYPE_0XED 240endif 241 242if IO_DELAY_UDELAY 243config DEFAULT_IO_DELAY_TYPE 244 int 245 default IO_DELAY_TYPE_UDELAY 246endif 247 248if IO_DELAY_NONE 249config DEFAULT_IO_DELAY_TYPE 250 int 251 default IO_DELAY_TYPE_NONE 252endif 253 254config DEBUG_BOOT_PARAMS 255 bool "Debug boot parameters" 256 depends on DEBUG_KERNEL 257 depends on DEBUG_FS 258 help 259 This option will cause struct boot_params to be exported via debugfs. 260 261config CPA_DEBUG 262 bool "CPA self-test code" 263 depends on DEBUG_KERNEL 264 help 265 Do change_page_attr() self-tests every 30 seconds. 266 267config OPTIMIZE_INLINING 268 bool "Allow gcc to uninline functions marked 'inline'" 269 help 270 This option determines if the kernel forces gcc to inline the functions 271 developers have marked 'inline'. Doing so takes away freedom from gcc to 272 do what it thinks is best, which is desirable for the gcc 3.x series of 273 compilers. The gcc 4.x series have a rewritten inlining algorithm and 274 enabling this option will generate a smaller kernel there. Hopefully 275 this algorithm is so good that allowing gcc 4.x and above to make the 276 decision will become the default in the future. Until then this option 277 is there to test gcc for this. 278 279 If unsure, say N. 280 281endmenu 282 283