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 depends on ARCH_SUPPORTS_DEBUG_PAGEALLOC 79 ---help--- 80 Unmap pages from the kernel linear mapping after free_pages(). 81 This results in a large slowdown, but helps to find certain types 82 of memory corruptions. 83 84config DEBUG_PER_CPU_MAPS 85 bool "Debug access to per_cpu maps" 86 depends on DEBUG_KERNEL 87 depends on SMP 88 default n 89 ---help--- 90 Say Y to verify that the per_cpu map being accessed has 91 been setup. Adds a fair amount of code to kernel memory 92 and decreases performance. 93 94 Say N if unsure. 95 96config X86_PTDUMP 97 bool "Export kernel pagetable layout to userspace via debugfs" 98 depends on DEBUG_KERNEL 99 select DEBUG_FS 100 ---help--- 101 Say Y here if you want to show the kernel pagetable layout in a 102 debugfs file. This information is only useful for kernel developers 103 who are working in architecture specific areas of the kernel. 104 It is probably not a good idea to enable this feature in a production 105 kernel. 106 If in doubt, say "N" 107 108config DEBUG_RODATA 109 bool "Write protect kernel read-only data structures" 110 default y 111 depends on DEBUG_KERNEL 112 ---help--- 113 Mark the kernel read-only data as write-protected in the pagetables, 114 in order to catch accidental (and incorrect) writes to such const 115 data. This is recommended so that we can catch kernel bugs sooner. 116 If in doubt, say "Y". 117 118config DEBUG_RODATA_TEST 119 bool "Testcase for the DEBUG_RODATA feature" 120 depends on DEBUG_RODATA 121 default y 122 ---help--- 123 This option enables a testcase for the DEBUG_RODATA 124 feature as well as for the change_page_attr() infrastructure. 125 If in doubt, say "N" 126 127config DEBUG_NX_TEST 128 tristate "Testcase for the NX non-executable stack feature" 129 depends on DEBUG_KERNEL && m 130 ---help--- 131 This option enables a testcase for the CPU NX capability 132 and the software setup of this feature. 133 If in doubt, say "N" 134 135config 4KSTACKS 136 bool "Use 4Kb for kernel stacks instead of 8Kb" 137 depends on X86_32 138 ---help--- 139 If you say Y here the kernel will use a 4Kb stacksize for the 140 kernel stack attached to each process/thread. This facilitates 141 running more threads on a system and also reduces the pressure 142 on the VM subsystem for higher order allocations. This option 143 will also use IRQ stacks to compensate for the reduced stackspace. 144 145config DOUBLEFAULT 146 default y 147 bool "Enable doublefault exception handler" if EMBEDDED 148 depends on X86_32 149 ---help--- 150 This option allows trapping of rare doublefault exceptions that 151 would otherwise cause a system to silently reboot. Disabling this 152 option saves about 4k and might cause you much additional grey 153 hair. 154 155config IOMMU_DEBUG 156 bool "Enable IOMMU debugging" 157 depends on GART_IOMMU && DEBUG_KERNEL 158 depends on X86_64 159 ---help--- 160 Force the IOMMU to on even when you have less than 4GB of 161 memory and add debugging code. On overflow always panic. And 162 allow to enable IOMMU leak tracing. Can be disabled at boot 163 time with iommu=noforce. This will also enable scatter gather 164 list merging. Currently not recommended for production 165 code. When you use it make sure you have a big enough 166 IOMMU/AGP aperture. Most of the options enabled by this can 167 be set more finegrained using the iommu= command line 168 options. See Documentation/x86_64/boot-options.txt for more 169 details. 170 171config IOMMU_LEAK 172 bool "IOMMU leak tracing" 173 depends on DEBUG_KERNEL 174 depends on IOMMU_DEBUG 175 ---help--- 176 Add a simple leak tracer to the IOMMU code. This is useful when you 177 are debugging a buggy device driver that leaks IOMMU mappings. 178 179config HAVE_MMIOTRACE_SUPPORT 180 def_bool y 181 182# 183# IO delay types: 184# 185 186config IO_DELAY_TYPE_0X80 187 int 188 default "0" 189 190config IO_DELAY_TYPE_0XED 191 int 192 default "1" 193 194config IO_DELAY_TYPE_UDELAY 195 int 196 default "2" 197 198config IO_DELAY_TYPE_NONE 199 int 200 default "3" 201 202choice 203 prompt "IO delay type" 204 default IO_DELAY_0X80 205 206config IO_DELAY_0X80 207 bool "port 0x80 based port-IO delay [recommended]" 208 ---help--- 209 This is the traditional Linux IO delay used for in/out_p. 210 It is the most tested hence safest selection here. 211 212config IO_DELAY_0XED 213 bool "port 0xed based port-IO delay" 214 ---help--- 215 Use port 0xed as the IO delay. This frees up port 0x80 which is 216 often used as a hardware-debug port. 217 218config IO_DELAY_UDELAY 219 bool "udelay based port-IO delay" 220 ---help--- 221 Use udelay(2) as the IO delay method. This provides the delay 222 while not having any side-effect on the IO port space. 223 224config IO_DELAY_NONE 225 bool "no port-IO delay" 226 ---help--- 227 No port-IO delay. Will break on old boxes that require port-IO 228 delay for certain operations. Should work on most new machines. 229 230endchoice 231 232if IO_DELAY_0X80 233config DEFAULT_IO_DELAY_TYPE 234 int 235 default IO_DELAY_TYPE_0X80 236endif 237 238if IO_DELAY_0XED 239config DEFAULT_IO_DELAY_TYPE 240 int 241 default IO_DELAY_TYPE_0XED 242endif 243 244if IO_DELAY_UDELAY 245config DEFAULT_IO_DELAY_TYPE 246 int 247 default IO_DELAY_TYPE_UDELAY 248endif 249 250if IO_DELAY_NONE 251config DEFAULT_IO_DELAY_TYPE 252 int 253 default IO_DELAY_TYPE_NONE 254endif 255 256config DEBUG_BOOT_PARAMS 257 bool "Debug boot parameters" 258 depends on DEBUG_KERNEL 259 depends on DEBUG_FS 260 ---help--- 261 This option will cause struct boot_params to be exported via debugfs. 262 263config CPA_DEBUG 264 bool "CPA self-test code" 265 depends on DEBUG_KERNEL 266 ---help--- 267 Do change_page_attr() self-tests every 30 seconds. 268 269config OPTIMIZE_INLINING 270 bool "Allow gcc to uninline functions marked 'inline'" 271 ---help--- 272 This option determines if the kernel forces gcc to inline the functions 273 developers have marked 'inline'. Doing so takes away freedom from gcc to 274 do what it thinks is best, which is desirable for the gcc 3.x series of 275 compilers. The gcc 4.x series have a rewritten inlining algorithm and 276 enabling this option will generate a smaller kernel there. Hopefully 277 this algorithm is so good that allowing gcc 4.x and above to make the 278 decision will become the default in the future. Until then this option 279 is there to test gcc for this. 280 281 If unsure, say N. 282 283endmenu 284